A UNITED STATES DEPARTMENT OF COMMERCE PUBLICATION U.S. DEPARTMENT OF COMMERCE NATIONAL OCEANIC AND ATMOSPHERIC piNlSTBATlON NATIONAL MARINE FISHERIES SERVICE [/.anne Bioiogicai Laboratory |_l BRAR Y i971 WOODS HOLE. MASS. 4 Blue Crab Meat I. Preservation by Freezing II. Effect of Chemical TreatmenTs on Acceptability 1S71 SPECIAL SCIENTIFIC REPORT-FIS. The National Marine Fisheries Service (NMFS) does not approve, rec- ommend or endorse any proprietary product or proprietary material mentioned in this publication. No reference shall be made to NMFS, or to this publication furnished by NMFS, in any advertising or sales pro- motion which would indicate or imply that NMFS approves, recommends or endorses any proprietary product or proprietary material mentioned herein, or which has as its purpose an intent to cause directly or indirectly the advertised product to be used or purchased because of this NMFS publication. UNITED STATES DEPARTMENT OF COMMERCE Maurice H. Stans, Secretary NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION Dr. Robert M. White, Adm'mistrator NATIONAL MARINE FISHERIES SERVICE Philip M. Roedel, Director Blue Crab Meat I. Preservafion by Freezing II. Effect of Chemical Treatments on Acceptability By JURGEN H. STRASSER, JEAN S. LENNON, and FREDERICK J. KING Special Scientific Report — Fisheries No. 630 Seattle, Washington July 1971 CONTENTS Page I. Preservation by Freezing Introduction 1 Materials 2 Types of blue crab meat 2 Freezing of blue crab meat 2 Other methods of preservation 4 Methods of packaging and storage 5 Organoleptic evaluation 5 Results and Discussion 5 Evaluation of taste-panel consistency 5 Comparison of freezing rates 6 Comparison of different freezing methods 7 Comparison of two packaging methods 8 Comparison of tyi^es of blue crab meat 8 Summary and conclusions 8 Acknowledgments 11 Literature cited 11 II. Effect of chemical treatments on acceptability Introduction 15 Materials and methods 17 Dipping treatment 17 Spray (glazing) procedure 17 Chemical preservative solutions used 17 Bacteriological analyses 18 Results and Discussion 18 Monosodium glutamate dips or dusts 18 Ascorbic acid dips 19 Condensed phosphate, salt, and citrate dips 20 Sodium nitrite dip 20 Various combinations of dip and spray solutions 21 Comparison of freezing with other preservations methods . 22 Summary and conclusions 23 Acknowledgments 24 Literature cited 24 111 Blue Crab Meat I. Preservation by Freezing By JURGEN H. STRASSER and JEAN S. LENNON Central Engineering Laboratories, FMC Corporation, 1185 Coleman Avenue, Santa Clara, California 95052 and FREDERICK J. KING National Marine Fisheries Service Technological Laboratory Gloucester, Massachusetts 01930 ABSTRACT Freezing was studied as a method of preserving blue crab meat for up to 8 months. The results indicate that a rapid freezing rate, storage below 0° F, and vacuum pack- aging are preferable to minimize losses in the desirable qualities of freshly picked meat. INTRODUCTION The blue crab {Callinectes sapidus) is one of our most valuable commercial shellfish re- sources both in volume of landings and in value of its food products. This industry is also dis- tinguished by having one of the greatest sea- sonal variations in ex-vessel prices for any shellfish. Several factors are involved, such as the short life span of the animal (2-3 years) and the fact that it must be kept alive until cooked in order to remove the meat. However, a more significant factor is that blue crab meat itself is a highly perishable product. Practi- cally all of the present output is sold as fresh meat which has a shelf life of up to 10 days at 32° to 38° F. Because blue crab meat is highly perishable, several methods of food preservation have been considered. Heat sterilization was proposed several years ago (Fellers, 1936) but this treat- ' Presented at the 30th Annual Meeting of the In- stitute of Food Technologists, May 24-28, 1970. ment is unpopular because it causes discolora- tion and development of off'-flavors. Although the chemical nature of these alterations is not completely understood, it is generally accepted that heat-induced breakdown products from the muscle proteins and copper from blood pig- ments are involved (Groninger and Dassow, 1964; Elliott and Harvey, 1951). Milder heat treatments have been proposed (Byrd, 1951) and heat pasteurization is used commercially. By using heat to reduce the bacterial popula- tion of freshly picked crab meat, it is possible to extend the meat's storage life for up to 6 months at 33° to 38° F (Littleford, 1957). In practice, the heat input to reduce the bacterial population has to be controlled very carefully to avoid the undesirable effects of overcooking on the meat's appearance and taste. Because the tolerance is narrow between the intended and the undesirable effects of this heat treat- ment, the usefulness of this method of preserva- tion is highly dependant on the bacterial pop- ulation of the meat just before it is pasteurized. Freezing has also been considered as a meth- od of preservation. Since it achieves inacti- vation of bacterial spoilage without a heat treatment, it has a theoretical advantage com- pared with pasteurization. However, the com- mercial production of frozen blue crab meat is minor since its storage life at 0° F is considered to be less than 1 month (U.S. General Services Administration, 1956). If blue crab meat is frozen by conventional techniques (plate freez- er, air-blast freezer, etc.), the meat tends to become spongy and fibrous in texture and it will lose the delicate flavor of fresh meat after a few weeks at 0° F (Dassow, Pottinger, and Holston, 1956). Although this deterioration is probably related to protein and lipid trans- formations in situ, its cause is not clear. Sim- ilar phenomena are believed to limit the frozen storage life of other crustaceans although the rate of this deterioration is dependent on the species used and whether the picked meat or meat-in-the-shell is frozen. It is well known that the storage stability of frozen seafoods, in general, can be influenced by the following factors: method (rate) of freezing, method of packaging, and storage tem- perature and its duration. For example, it is known that techniques such as cryogenic freez- ing (vs. plate, air blast, or brine immersion freezing), vacuum packaging (vs. a loose-fit- ting package containing air) and storage below 0° F (vs. storage at 0° F or above) may pro- long the storage life of seafoods. In the case of blue crab meat or meat from other crusta- ceans, the relative importance of these tech- niques in determining frozen storage stability has received very little attention. Consequently, the objective of the present investigation is to compare each of these techniques in various combinations with other preservation tech- niques in order to discover which procedures are required to preserve blue crab meat for 2 to 8 months without any significant loss in the desirable qualities of freshly picked meat. MATERIALS AND METHODS Types of Blue Crab Meat Most of the experimental i^rogram was per- formed with "regular" blue crab meat obtained from low-salinity waters in the Chesapeake Bay and supplied by the J. M. Clayton Company, Cambridge, Md. Regular meat is a trade des- ignation for meat which is picked from crab bodies or cores. Because it contains mostly flake meat with a much smaller quantity of lump meat, it is called "flake" meat in this report. For comparison purposes, hand-picked lump meat and claw meat from the same source were used in smaller quantities. For other comparison tests, regular and lump meat were obtained from the high-salinity waters oflF the Virginia coast and supplied by George 0. Spence and Sons Co., Quinby, Va. The freshly picked samples were shipped in ice to the Na- tional Marine Fisheries Service Laboratory in College Park, Md., and immediately frozen as described below. Each sample in these tests contained appi'oximately 95 g of crab meat. After completing the preservation treatments, the samples were shipped to FMC Central En- gineering Laboratories in insulated styrofoam containers using dry ice for the frozen samples or wet ice for the freshly picked control samples. Freezing of Blue Crab Meat Two cryogenic liquids, Freon 12- and nitro- gen, were used to freeze individual pieces of meat before packaging. These cryogenic meth- ods were not used on prepackaged meat for two basic reasons. We were aware that prepack- aging the meat would increase the cost of freez- ing per unit of meat frozen since it would lengthen the time needed to freeze all the pieces of meat in that package. Also, there was no evident advantage from a technological view- point for the blue crab industry to freeze pre- packaged meat. Indeed, preliminary experi- mental results have indicated that the quality of individually frozen pieces of blue crab meat is superior to the quality of prepackaged frozen blue crab meat even when the package is kept 14,-inch thick during freezing. Freezing by immersion in food grade Freon 1 2. — The arrangement of the equipment is shown in Figure I-l. Dewar I (capacity 2 liters) was used to cool the Freon coming from ' Trade names are used to facilitate description; no endorsement of product is implied. The chemical name for Freon 12 is dichlorodifluoromethane. Valve i ^ Copper lubing Dry Ice and Acetone ;r Cover screen f^f^Si ■^ Pieces of crab meat immersed in Freon 12 ^^an Wire basket Dewar I Dewar II I Pressure tank with Freon 12 Figure I-l. — Equipment used for immersion freezing tests. Figure 1-2. — Immersion freezing of crab meat in food grade Freon 12. the tank by means of a dry ice-acetone mix- ture. The liquid Freon level in Dewar II (ca- pacity 4 liters) was kept at about 4 inches (Fig. 1-2). The highest temperature the liq- uid Freon can reach is — 21.6° F, which is its evaporation temperature. Owing to the evaporative cooling effect, the temperature of the Freon in Dewar II was usually several degrees lower. A stainless steel wire basket was first im- mersed into the Freon. Each 95-g sample was frozen by dropping the crab meat, piece by piece, into the Freon. This operation took 60 sec to complete. Then a screen was placed on top of the floating meat pieces to hold them immersed. The meat was taken out of the Freon by means of the wire basket and placed into its package. Freezing by spraying with Freon 12. — A spray nozzle head was attached to the copper tubing carrying liquid Freon from Dewar I (Fig. I-l) . The Freon was sprayed in a sway- ing action for about 6 min onto a crab meat sample placed on a stainless steel screen. After the meat was covered with another stainless steel screen, it was turned over and sprayed from the other side until completely frozen. Freezing by immersion in liquid nitrogen. — The same procedure as used in freezing by Freon immersion was applied, using in this case liquid nitrogen in the Dewar flask II (Fig. I-l). The crab meat was dropped into the nitrogen piece by piece. Since the meat sank to the bottom, no cover screen was necessary. Freezing by intermittent dipping in liquid nitrogen. — The crab meat was spread as loosely as possible in the wire basket and then the basket was immersed in the liquid nitrogen. However, the liquid nitrogen immersion was interrupted in short intervals to allow the in- side of the sample to equilibrate in temperature. This was done by dipping the sample 10 times in 30 sec, with an immersion time of 2 sec each time. This procedure prevented cracking of the frozen meat samples. Freezing by nitrogen gas blast. — An "Ultra Freeze Simulator Freezer" of National Cyl- inder Gas (NCG) Division of Chemetron Cor- poration, Chicago, 111., was used to demonstrate the effect of fast freezing in a low-temperature nitrogen gas atmosphere. Freshly picked, reg- ular blue crab meat was placed on a wire screen (Fig. 1-3) and exposed to a blast of nitrogen gas at a temperature of — 150° F. This tem- perature was maintained by injecting controlled amounts of liquid nitrogen into the gas which was circulated by a high-speed fan. Slow freezing of blue crab meat. — The blue crab meat was packaged in a double wall polyethylene bag, then wrapped by aluminum foil and a paper bag. The different samples were then placed in a — 20° F freezer room. Other Methods of Preservation Pasteurization of blue crab meat. — Vac- uum-packed pouches (6.5 x 10 inches) con- taining 95 g of crab meat were submersed into Figure 1-3. — Crab meat spread on the screen of an "Ultra-Freeze Simulator Freezer". a 170° F water bath and kept there for 10 min to raise the minimum internal temperature to 170° F (Byrd, 1951; Littleford, 1957). The hot pouches were quickly cooled in a cold-water bath and put into storage in a refrigerator at 34° F. Sterilization of blue crab meat. — Vacuum- packed pouches (6.5 X 10 inches) containing 95 g of crab meat were brought into an auto- clave and heated at 250° F under steam pres- sure for 15 min. The pouches were cooled to room temperature under pressure with cold water. Then they were stored at 34° F. Freeze drying of blue crab meat. — Crab meat samples were frozen by exposure to cold air (—20° F) then freeze-dried at a vacuum of less than 200 fj. and a maximum heating temperature of 120° F. The freeze-dried samples were packaged under vacuum in lam- inated pouches. Methods of Packaging and of Storage Vacuum pouches. — All the heat-processed and freeze-dried crab meat samples and some of the frozen samples were packaged in pouches of 6.5 X 10 inches made of laminated polyeth- ylene-aluminum foil-mylar and heat-sealed under a vacuum of 28 inches. Bags. — The rest of the frozen crab meat samples were placed into double-wall polyeth- ylene bags which are commonly used for stor- age of food in household freezers. The bags were wrapped with aluminum foil for mechan- ical protection and as a protection against "freezer burn" which is caused by a moisture transport because of uneven temperature dis- tribution inside the bag. An outside paper bag was used to facilitate labeling. Storage conditions. — Most of the frozen crab meat samples were stored at — 20° F (± 2° F) or at 0° F ( ± 2° F) . A few samples were stored on dry ice ( — 108° F) for com- parison purposes. The pasteurized and steri- lized samples were held at 34° F (±2° F) while the freeze-dried samples were held at ambient (room) temperature. Organoleptic Evaluation From an initial group of 24 persons, a taste panel of 12 to 15 members was selected. Each tester was asked to rate samples for appear- ance, odor, texture, and overall taste on a 9- point hedonic preference scale. For the flavor evaluation, intensity scoring, and descriptive evaluation were also used (Fig. 1-4) . To lessen the effect of fatigue, only five samples were used for each test. Two tests were performed per day, one at about 11:30 AM and the other at about 3:00 PM. Crab meat samples were prepared for these evaluations by thawing in the package at ambient (room) temperature for 45 to 60 min. The pasteurized or sterilized samples were just taken out of the pouch while the freeze-dried samples were rehydrated for 25 min in water at ambient (room) temperature and drained afterwards. Samples were distributed into 1- oz portion control cups and served to the mem- bers of the taste panel. Fresh crab meat was used as a reference sample for each panel session. It was shipped in crushed ice by air freight from the East Coast, stored at 34° F and used within 1 week. It was served together with the other samples being evaluated and was not designated as be- ing "fresh." RESULTS AND DISCUSSION Evaluation of Taste-Panel Consistency Since fresh crab meat was used as an un- known reference sample in each session, the panel evaluated it a total of 23 times during an 8-month period. The total average ratings for these fresh samples (based on 23 evaluations or 295 individual ratings) were: appearance = 6.6, odor = 6.5, texture — 6.6, overall taste 6.8, and degree of undesirable flavors = 1.5. The ranges for these ratings were: appearance = 5.5 to 7.4, odor = 5.7 to 7.9, texture = 5.9 to 7.5, overall taste = 6.4 to 7.4, and degree of undesirable flavor = 1.1 to 1.8. A statistical analysis was made from the in- dividual ratings for overall taste to assess the effects of personal preference for crab meat and individual sensitivity to different samples of fresh crab meat on the results (Strasser, 1969) . BLUE CRAB STUDY Nanne Date Please evaluate each crab nneat sample for the quality factor listed below, using the appropriate scale. Appearance Texture Overall Taste Like extremely Like very much Like moderately Like slightly Neither like nor dislike Dislike slightly Dislike moderately Dislike very much Dislike extremely Presence of Undesirable Flavor Kind of Undesirable Flavor None 1 Slight 2 Moderate 3 Intense 4 Flat 1 Salty 2 Too acidic 3 Metallic 4 Medicinal 5 Bitter 6 Astringent 7 Rancid 8 Musty 9 Biting 10 Fishy U Other (Please state) SAMPLE Appe arance Odor Texture Overall Taste | Rating Remarks Ratirg Remarks Ralmg Remarks Ralmg Remarks A B C D E Presence of Kind of Undesirable Undesirable Flavor Flavor Figure 1-4. — Rating sheet for organoleptic evaluation of quality. The results of this analysis indicated that it was not necessary to apply statistical correc- tions to the overall taste data. Following this analysis and visual examination of the taste- panel data (Strasser, 1969), it was decided not to apply statistical corrections to the appear- ance, odor, and texture data as well. Several different chemical or physical meth- ods have been used or proposed to determine the quality of crab meat from various species. They include determination of ammonia (Bur- nett, 1965; Fernandez-Flores and Salwin, 1968) , trimethylamine nitrogen or volatile ba- sic nitrogen (Spinelli, Eklund, and Miyauchi, 1964a; Tanikawa, 1959) , volatile reducing sub- stances (Farber and Lerke, 1968), picric acid turbidity (Kurtzman and Sn.vder, 1960), 2- thiobarbituric acid (Anderson and Danielson, 1961) , hypoxanthine (Spinelli, Eklund, and Mi- yauchi, 1964b) , physical measurement of shear force (Dassow, McKee, and Nelson, 1962), or drip (Barnett, Nelson, and Dassow, 1967; Col- lins and Brown. 1965; Miyauchi, 1963). They were not used in this investigation owing to incomplete information on their suitability for assessing degrees of freshness of thawed blue crab meat (in contrast to fresh meat) or their correlation with sensory evaluation methodol- ogy as recommended by Amerine, Pangborn, and Roessler ( 1965) . A similar conclusion was made by Early (1967). Comparison of Freezing Rates In order to compare freezing rates, pieces of lump meat of about 5 mm diameter, 20 mm in length and about 1 g in weight were exposed to three different freezing conditions. These conditions were freezing in still air at — 20° F, freezing in circulated nitrogen gas which was kept at — 150° F, and immersion freezing in Freon 12 which had a temperature of — 28° F. The temperature in the center of the piece of crab meat, as measured by fine copper-con- stantan thermocouples, was monitored contin- uously during the freezing experiments. The results are plotted in Figure 1-5. It took ap- proximately 30 sec to freeze the sample by im- mersion in Freon 12. The freezing time was approximately 2 min when using cold nitrogen blast. However, it took 14 min to freeze the same size piece in still cold air. Immersion pi'oved to be by far the fastest method of freezing. *100 1^ +80 S +40 5 +20 - 1 1 I 1 1 1 - - V ^.^ Still air at -20" F. - V - x \ -__^_^^^ - V ,,,.-— Cifcjtated itrogen 9a S a -150''f, ^'''■'~---..,,,____^^ \ Y^ ^— Immersion n Freon 12 a -28° F. ' 1 -V -A - \ - - \ - - 1 \ 1 1 1 1 1 FREEZING TIME Figure 1-5. — Freezing curves of crab meat. Comparison of DifFerent Freezing Methods Ratings obtained from samples frozen by Freon immersion or by Freon sprays were quite similar to those obtained from samples frozen by intermittent immersion in liquid ni- trogen (Table I-l) . In a few cases, the ratings in these tables also suggest that samples frozen in Freon were slightly better than samples frozen in liquid nitrogen but this difference is not considered significant. In comparison with the Freon freezing and the liquid nitrogen freezing methods, the panel ratings for samples frozen by a cold nitrogen gas blast (about — 150° F) were very similar for up to 4 months' storage. After 6 months' storage, the samples frozen by nitrogen blast rated slightly, but not significantly, lower than the immersion-frozen samples (Table I-l). Results obtained from panel evaluations of slow-frozen samples indicate that this method was less desirable than any of the other freez- ing methods used in this study. For example, even a low-temperature storage at — 20° F did not prevent a gradual loss in quality in these samples, whereas the quick-frozen samples maintained a much better quality at this tem- perature. These results are consistent with the hypothesis that slower freezing rates permit more interactions between solutes in the un- frozen tissue fluids and other tissue components (Love, 1968; van den Berg, 1968). Although most of the frozen-stored samples were slowly thawed at room temperature, quick thawing by microwave energy resulted in a product of slightly higher acceptability (Table I-l). Comparison of Freezing with Other Preservation Methods Panel ratings given to heat-pasteurized sam- ples stored for up to 8 months at -h 34° F (Table 1-2) were generally comparable to quick-frozen, vacuum-i^ackaged samples stored at 0° F for the same length of time. In some instances, the ratings for these pasteurized samples ap- peared to lie lower than those received by sam- ples stored at —20° F (Table I-l). On the other hand, heat-sterilized samples were con- sistently downgraded by the panel for their undesirable bluish discoloration as well as their oif-taste (Table 1-2). A few samples of crab meat were preserved by freeze-drying, vacuum-packaged, and stored for 6 months at ambient temperature. The panel consistently rated the taste of these sam- ples as unacceptable although their appearance and texture received fair acceptance ratings (Table 1-2). Effect of Different Storage Tempera- tures Crab meat samples held at dry ice temper- ature (about — 108° F) were rated highly by the taste panel even after 8 months' storage. Quick-frozen samples held at — 20° F were rated somewhat lower during this storage peri- od but their ratings were still generally within the range given to freshly picked, nonfrozen control samples. In contrast, some of the sam- ples held at 0° F, received much lower ratings than comparative samples held at the lower temperatures. Particularly, the ratings of texture often dropped farther than the taste ratings for these samples. Evidently, the method of packaging as well as the length of the storage period significantly affects the qual- ity of samples held at 0° F for up to 8 months. Comparison of Two Packaging Methods It was generally noted that the samples which had been packaged in a vacuum-sealed pouch (laminated polyethylene-aluminum foil-mylar) rated higher than samples which had been packaged in unsealed polyethylene bags under atmospheric pressure. In samples stored at — 20° F, this difference was more pronounced in the odor ratings than in the taste ratings. In samples stored at 0° F, this difference be- came obvious in the taste ratings after much shorter storage periods. Comparison of Types of Blue Crab Meat In evaluating the results of the taste-panel evaluations (Tables I-l and 1-2), flake and lump meat samples have been considered on virtually synonomous terms. Lump meat is often regarded as a premium grade of flake meat in the trade. The freezing and storage characteristics of both types of meat appear to be reasonably similar. On the other hand, claw meat is considered a lower quality meat even when fresh since it comes from a muscle tissue which has a different physiological function. Thus, the poorer ratings given for the few frozen-stored claw meat samples tested (Table I-l) are not surprising. The taste- panel evaluations did not reveal any consistently significant difference that could be related to the low-salinity waters of the Chesapeake Bay and the high-salinity waters off the Virginia Coast. This conclusion may surprise some gourmets who are partial to locally caught blue crabs but the origins of this partiality are spec- ulative. SUMMARY AND CONCLUSIONS The results of this investigation show that rapid freezing, storage below 0° F, and vac- uum-packaging extend the shelf life of blue crab meat. Quick-freezing methods (immer- sion or spraying using Freon 12 or low-temper- ature nitrogen) were superior to slow-freezing methods (freezing time more than 30 min). For example, after 8 months of storage at — 20° F, quick-frozen, vacuum-packed, blue crab meat was highly acceptable when com- pared with fresh, refrigerated meat. At 0° F storage temperature, a noticeable drop in qual- ity occurred during storage, especially if the product was not vacuum-packed. However, vacuum-packed frozen crab meat of high initial quality can be stored at 0° F for at least 8 months and still be comparable in quality to heat-pasteurized crab meat that has been stored at 34° F for the same time. The rate of freezing blue crab meat has a significant effect on preserving its desirable qualities. Using spraying or immersion tech- niques based on Freon 12, freezing was accom- plished in about 1 min and resulted in a product of very acceptable quality after storage and thawing. Slightly longer freezing rates were involved in some of the cryogenic nitrogen freezing methods. Although these freezing rates were less than 3 min, they resulted in products with a slightly lower acceptability. Even without considering the detrimental ef- fects of slow freezing (30 min or more), it is obvious that the quality of frozen-stored blue crab meat is directly related to the rapidity of freezing it. To extend the shelf life of frozen blue crab meat, it would be advisable to store it below 0°F, preferably as low as — 20° F. Storage temperatures below — 20° F offer further im- provement in its storage stability but they are usually not as economically feasible as the higher temperatures. At 0° F storage temper- ature, a noticeable drop in quality can occur during storage, especially if proper attention is not given to considerations such as using only crab meat of high initial quality, quick freezing, vacuum packaging, and minimum storage per- iods. The method of packaging had a noticeable in- fluence on the storage stability of frozen crab meat. At 0° F storage temperature, vacuum packaging in a heat-sealed polyethylene-alumi- num foil-mylar pouch resulted in a considerably Table I-l. — Organoleptic evaluation of frozen-stored blue crab meat. Results (9 point scale) after storing samples at indicated temperature and number of months^ Type of meat Method of freezing Packaging used' 0° F -20° F Part 1. Overall taste results. Lump Freon immersion Bag V. P. 7.2 6.0 6.9 7.1 7.4 " " Bag 5.5 3.7 . . *' " V. P. 7.4 "8 » V.P. , . 7.9 Flake " Bag V.P. 6,2 6,6 6,9 6,2 7.6 6.7 6.9 "« •• Bag Bag 4.4 4.9 5.9 3.9 6,2 6,7 7,2 7.0 " tt V.P. 6.9 5.9 6.3 6.0 "8 " Bag 6,9 6.4 "a " V.P. 7.4 7.7 7.7 "8 ** V.P. 7.0 6,4 5,0 5.9 >» Freon spray Bag 6.9 6.6 »f *' V.P. . . 7.0 Lump LN immersion V.P. 7.5 »» ** V.P. 6,7 6.8 " w V.P. V.P. 6.6 6,4 •• 7.5 Claw ** V.P. , , 5.8 »P Intermittent V.P. 6.1 6.2 Flake LN dipping N2 blast Bag V.P. 7.3 6.9 7.0 NCG process V.P. 7.0 6.2 »» Slow frozen"^ Bag V.P. 6.4 5.4 5.4 Part 2. Odor results. Lump Freon immersion Bag V.P. •• 6.6 6,8 7.3 6.9 7.5 » ** Bag 5.4 4.9 . . " " V.P. 7.3 »a *• V.P. 7.4 Flake " Bag V.P. 5.6 6.3 6.5 6.4 7.2 6.7 6.7 "« " Bag 6,1 6.3 6,6 6.3 " » Bag 4,9 5.1 5.5 4,5 " »» V.P. 6.7 6,1 6.8 6,0 »•• " Bag 6,9 6.6 »'« " V.P. 6.7 7.1 7,1 "» " V.P. 6.9 6.7 6.4 7.2 n Freon spray Bag V.P. 7.2 6.5 7.3 Lump LN immersion V.P. 7,2 »» " V.P. 7.1 6.8 n w V.P. V.P. •• •• 7.2 7.3 7.0 Claw '• V.P. 5.9 i> *' V.P. , , 6.4 6.0 See footnotes at end of table. Table I-l. — Organoleptic evaluation of frozen-stored blue crab meat. — Con. Type Method of freezing Packaging used' Besults (9 point indicated temper scale) after storing samples at ature and number of months" of meat 0° F -20° F 2 4 6 8 2 4 6 8 Part 2. Odor results. — Con Flake Intermittent LN dipping Na blast NCG process Bag V. P. V. P. 6.6 6.9 6.0 6.9 6.7 » Slow frozen^ Bag V. P. 6.2 5.9 5.0 Part 3 Textu re results. Lump Freon immersion Bag 7.8 7.5 7.2 7.2 " " V. P. 7.9 : » Bag V. P. 7.0 5.4 7.3 •• "a " V. P. 8.1 . . Flake >. Bag V. P. •• •• 6.6 6.6 6.8 6.5 7.4 7.1 6.7 »•* " Bag Bag 5.3 3.9 5.3 3.6 6.2 7.1 7.4 7.4 » " V. P. 6.6 5.8 5.8 5.5 "9 " Bag 7.2 7.0 "8 " V. P. 7.6 7.4 7.5 **a " V. P. 6.9 5.8 4.4 5.0 , , . , „ Freon spray Bag V. P. •• 6.9 6.9 7.4 Lump LN immersion V.P. V. p. 7.1 6.9 7.8 " " V.P. , , , , 7.8 •' » V.P. 7.3 6.5 , . . . Claw >• V.P. V.P. 6.0 5.7 6.6 Flake Intermittent LN dipping Bag 7.4 6.9 fP " V.P. 6.9 •' Na blast NCG process Slow frozen^ V.P. Bag •• •• 7.0 6.1 6.7 6.1 n " V.P. •• 5.8 Part 4. Appearance results. Lump Freon immersion Bag V.P. 7.9 7.9 7.7 7.6 8.1 Bag V.P. 7.2 6.3 7.7 »'a »» V.P. . , 8.1 , , Flake n Bag , , , , . , 5.9 6.1 7.1 6.9 " " V.P. , , . , 6.6 5.6 6.5 "4 " Bag . . 5.3 6.3 5.8 6.0 " •• Bag 5.0 5.5 5.5 5.2 » " V.P. 5.0 6.1 6.3 5.9 »»a " Bag 6.9 7.1 See footnotes at end of table. 10 Table I-l. — Organoleptic evaluation of frozen-stored blue crab meat. — Con, Type Method of freezing Packaging used' Results (9 point scale) after storing samples at indicated temperature and number of months' of meat 0° F -20° F 2 4 6 8 2 4 6 8 Part 4. Appearance results. — Con. Flake' Freon immersion V. P. V.P. 7.5 5.0 5.7 7.7 7.4 7.9 7.4 .. Freon spray Bag V.P. . . 7.3 6.9 7.1 Lump LN immersion V.P. V.P. 7.0 7.5 7.8 " " V.P. . . 7.1 " '> V.P. 7.2 6.9 Claw « V.P. . . 5.9 " " V.P. 5.0 5.8 Flake Intermittent LN dipping Bag V.P. .. 6.7 7.1 6.4 " Na blast NCG process Slow frozen^ V.P. Bag V.P. .. 7.0 6.2 6.5 5.9 6.0 ^ "Bag" refers to a polyethylene bag without vacuum while "V.P." refers to a three-ply laminate package heat-sealed while under vacuum. " The rating system is outlined in Figure 1-4. Based on 23 separate evaluations (295 individual ratings), the panel's average rating for overall taste was 6.8 and its range was 6.4 to 7.4 for fresh crab meat. ' Samples obtained from crabs caught near the Virginia coast (high-salinity water). Other samples from crabs caught in the Chesapeake Bay (low-salinity water). ' Sample thawed by microwave energy instead of ambient conditions for the organoleptic evaluation. ' Crab meat placed in package before freezing in still air at —20° F. smaller quality drop during storage when com- pared with crab meat which was packed in unsealed but tightly closed polyethylene bags. This indicates that the quality changes of blue crab meat during frozen storage are caused primarily by oxidation effects. At — 20° F storage temperature, these oxidative changes occurred at a much slower pace. Nevertheless, even at — 20° F there was a noticeable quality difference between the vacuum-packed samples and the samples packed in unsealed polyethyl- ene bags. ACKNOWLEDGMENTS John J. Powell and George M. Knobl, Na- tional Marine Fisheries Service, College Park, Md., provided facilities for part of the exper- imental work and shipped crab meat samples to FMC Laboratories during this investigation. Financial support was received from the National Marine Fisheries Service under con- tract number 14-17-0007-968. LITERATURE CITED AMERINE, M. A., R. M. PANGBORN, and E. B. ROESSLER. 1965. Principles of sensory evaluation of food. Academic Press, New York, N.Y., 602 p. ANDERSON, K., and C. E. DANIELSON. 1961. Storage changes in frozen fish : A compar- ison of objective and subjective tests. Food Technol. 15(2): 55-57. BARNETT, H. J., R. W. NELSON, and J. A. DASSOW. 1967. Technological studies of Dungeness crab processing. Part 3 — Laboratory experiments in the control of drain time. U.S. Fish Wildl. Serv., Fish. Ind. Res. 3(4) : 11-17. BURNETT, J. L. 1965. Ammonia as an inde.x of decomposition in crabmeat. J. Ass. Offic. Agr. Chem. 48(3) : 624- 627. BYRD, G. C. 1951. Method of keeping the meat of shellfish in a fresh condition. U.S. Patent 2,546,428. COLLINS, J., and R. L. BROWN. 1965. Frozen king crab (Paralithodes camtschat- ica) meat: Effect of processing conditions on fluids freed upon thawing. U.S. Fish. Wildl. Serv., Fish. Ind. Res. 2(4): 45-53. 11 Table 1-2. — Organoleptic evaluation of preserved blue crab meat. Type of Method of preservation Packaging used' Storage conditions Results (9 point scale) after storing samples for indicated number of months" meat 3 4 6 8 Part 1. Overall taste results Flake Heat-pasteurized V. P. -f34° F 6.8 6.9 6.7 Flake Heat-sterilized V. P. +34° F 4.0 4.7 5.2 Flake Freeze-dried V. P. Ambient temp. 4.9 Flake Freon immersion Bag On dry ice 7.3 7.4 Lump" Freon immersion Bag On dry ice 7.9 Flake' Freon immersion Bag On dry ice 7.2 Part 2. Odor results. Flake Heat-pasteurized V. P. +34° F 6.5 6.3 6.0 Flake Heat-sterilized V. P. + 34° F 3.3 4.7 4.2 Flake Freeze-dried V. P. Ambient temp. 5.9 Flake Freon immersion Bag On dry ice 6.7 6.8 Lump" Freon immersion Bag On dry ice 7.4 Flake' Freon immersion Bag On dry ice 7.9 Part 3. Texture results. Flake Heat-pasteurized V.P. +34° F 6.9 6.8 7.1 Flake Heat-sterilized V. P. + 34° F 6.0 5.0 5.4 Flake Freeze-dried V.P. Ambient temp. 6.1 Flake Freon immersion Bag On dry ice . . 7.3 7.4 Lump' Freon immersion Bag On dry ice 8.1 Flake' Freon immersion Bag On dry ice •• 7.5 Part 4. Appearance results. Flake Heat-pasteurized V.P. + 34° F 6.2 6.4 6.4 Flake Heat-sterilized V.P. + 34° F L7 2.7 2.9 Flake Freeze-dried V.P. Ambient temp. 7.0 Flake Freon immersion Bag On dry ice 6.3 7.1 Lump' Freon immersion Bag On dry ice 7.9 Flake' Freon immersion Bag On dry ice 7.4 ' "Bag" refers to a polyethylene bag without vacuum while "V. P." refers to a three-ply laminate package heat-sealed while imder vacuum. ' The rating system is oudined in Figure 1-4. Based on 23 separate evaluations (295 individual ratings), the panel's average rating for overall taste was 6.8 and its range was 6.4 to 7.4 for fresh crab meat. " Samples obtained from crabs caught near the Virginia coast (high-salinity water). Other samples from crabs caught in the Chesapeake Bay (low-salinity water). DASSOW, J. A., S. R. POTTINGER, and J. A. HOLSTON. 1956. Refrigeration of fish. Part 4. Prepara- tion, freezing and cold storage of fish, shellfish and precooked fishery products. U.S. Fish Wildl. Serv., Fish. Leafl. 430, 124 p. DASSOW, J. A., L. G. McKEE, and R. W. NELSON. 1962 Development of an instrument for evalu- ating texture of fishery products. Food Technol. 16(3) : 108-110. EARLY, J. C. 1967. Spoilage of crabmeat. M. Sc. thesis, Univer- sity of Nottingham, Nottingham, England, 146 p. ELLIOTT, H., and E. W. HARVEY. 1951. Biological methods of blood removal and their effectiveness in reducing discoloration in canned Dungeness crab meat. Food Technol. 5(4): 163-166. FARBER, L., and P. LERKE. 1968. A study of pasteurization as a means of ex- tending the low-temperature storage life of Dun- geness crab and shrimp. Final Report, Tech- nical Assistance Project Nos. 07-6-09102 and 99-6-09031, U.S. Department of Commerce, 39 p. FELLERS, C. R. 1936. Canning of crab meat. U.S. Patent 2,027,270. FERNANDEZ-FLORES, E., and H. SALWIN. 1968. Note on determination of ammonia in sea- food. J. Ass. Offic. Anal. Chem. 51 (5) : 1109-1110. 12 GRONINGER, H. S., and J. A. DASSOW. 1964. Observations of the "blueing" of king crab {Paralithodes cnintschatica) . U.S. Fish Wildl. Serv., Fish. Ind. Res. 2(3): 47-52. KURTZMAN, C. H., and D. G. SNYDER. 1960. Rapid objective freshness test for blue crab meat and observations on spoilage characteris- tics. Commer. Fish. Rev. 22(11): 12-15. LITTLEFORD, R. A. 1957. Studies on pasteurization of crab meat. University of Maryland, Seafood Processing Laboratory, Bull. 2, 14 p. LOVE, R. M. 1968. Ice formation in frozen muscle. In J. Havifthorn and E. J. Rolfe (editors), Low tem- perature biology of foodstuffs, p. 105-124. Perg- amon Press, Oxford, England. MIYAUCHI, D. T. 1963. Drip formation in fish. 1. A review of factors affecting drip. U.S. Fish Wildl. Serv., Fi.sh. Ind. Res. 2(2): 13-20. SPINELLI, J., M. EKLUND, and D. MIYAUCHI. i964a. Irradiation preservation of Pacific coast shellfish. II. Relation of bacterial counts, tri- methvlamine and total volatile base to sensory evaluation of irradiated king crab meat. Food Technol. 18(6): 143-147. 1964b. Measurement of hypoxanthine in fish as a method of assessing freshness. J. Food Sci. 29(6) : 710-714. STRASSER, J. H. 1969. Blue crab meat preservation study. Final Report, Contract No. 14-17-0007-968, Bureau of Commercial Fisheries, U.S. Fish Wildl. Serv., p. 101-257. TANIKAWA, E. 1959. Studies on technical problems in the pro- cessing of canned crab (ParnlitJwdes camtschat- ica) . Mem. Fac. Fisheries, Hokkaido Univ. 7(1 and 2) : 95-155. U.S. GENERAL SERVICES ADMINISTRATION. 1956. Crab meat, cooked, chilled and frozen. Fed- eral Specification PP-C-656a ( March 6, 1956 ), 6 p. VAN DEN BERG, L. 1968. Physiochemical changes in foods during freezing and subsequent storage. In J. Haw- thorn and E. J. Rolfe (editors), Low tempera- ture biology of foodstuffs, p. 205-219. Pergamon Press, Oxford, England. 13 Blue Crab Meat Effect of Chemical Treatments on Acceptability By JURCxEN H. STRASSER and JEAN S. LENNON Central Engineering Laboratories, FMC Corporation, 1185 Coleman Avenue, Santa Clara, California 95052 and FREDERICK J. KING National Marine Fisheries Service Technological Laboratory Gloucester, Massachusetts 01930 ABSTRACT Several chemical treatments were tested as adjuncts to i^reservation of blue crab meat. Most of these samples were preserved by freezing but some were heat-preserved or freeze-dried. In general, the dip treatments studied did not improve the quality of the preserved samples. However, glazing treatments with some of these chemical so- lutions appeared to improve the quality of frozen-stored samples. INTRODUCTION Meat from the blue crab (Callinectes sa- pidiis) is an example of a commercially valu- able product which is also highly perishable. Practically all of the present output is sold as fresh meat which has a shelf life of up to 10 days at 32° to 38° F. Although heat pasteur- ization is used occasionally to extend this shelf life (Byrd, 1951; Littleford, 1957), freezing is considered to have a great potential useful- ness in preserving the desirable qualities of fresh crab meat over a period of several months (Strasser, Lennon, and King, 1971) . Other re- sults have led to the suggestion that chemical treatments such as the ones listed below may be a useful adjunct to preservation techniques such as freezing, pasteurization, or even f reeze- drying. ' Portions of this report were presented at the 30th Annual Meeting of the Institute of Food Technologists, May 24-28, 1970. Monosodium glutamate is widely known as a flavor enhancer in food products. It has been used to glaze frozen shrimp or as a dusting on shrimp just before freezing with beneficial results after 10 months' storage at 0° F (Norton, Tressler, Farkas, 1952). Lake her- ring fillets treated with a 2^f solution of ascorbic acid and then glazed with a 1% so- lution of glutamate were of good quality through 12 months' storage at — 5° F (Greig, Emerson, and Fliehman, 1967). In contrast, results of other investigations based on frozen shrimp (Commercial Fisheries Review, 1952) or oysters (Morton and Dyer, 1956; Oster- haug and Nelson, 1957) do not suggest that monosodium glutamate improves the quality of these stored ])roducts. It is conceivable that the variability of these results is related to different concentrations of monosodium gluta- mate used in these investigations since treat- ment of food products with monosodium gluta- mate before freezing can reduce the number of 15 viable bacteria obtainable from the frozen- stored product (Rojowska and Cyganska, 1966^). Ascorbic acid has been used successfully to retard oxidative deterioration during frozen storage of several types of fish fillets (Ander- son and Danielson, 1961; Bauernfeind. Smith, and Siemer, 1951; Greig, 1967a, 1967b; Greig et al., 1967) and to inhibit the blueing reaction in canned king crab meat (Groninger and Das- sow, 1964) . The results of other investigations suggest that treating shrimp (Faulkner and Watts, 1955), oysters (Osterhaug and Nelson, 1957; Pottinger, 1951), lobster meat (Dyer and Home, 1953; Getchell and Highlands, 1957), or herring (Banks, 1951; Stansby and Dassow, 1963; Stansby, Pottinger, and Mi- yauchi, 1956) with ascorbic acid offers little or no improvement on the storage life of these frozen products. Since the effectiveness of ascorbic acid results from its sensitivity to ox- idizing agents, its usefulness in extending shelf life is obviously related to the concentration remaining on a product after a dip or spray treatment and after a given set of frozen stor- age conditions. For this reason, it is con- ceivable that the difference in results between the cited investigations may be a result of dif- ferent frozen storage conditions after a treat- ment with a dilute solution containing up to l^f ascorbic acid. On the other hand, antiox- idants such as butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) have been used successfully in several food products because their effectiveness depends on a dif- ferent chemical mechanism (Furia, 1968). Condensed phosphates, salt, and citrate have been used on several occasions singularly, or in various combinations, as components of dips or glazes used to extend the shelf life of frozen- stored seafoods. Trijiolyphosphate and pyro- phosphate are examples of condensed phos- phates which are used to inhibit textural deterioration or jn-otein dehydration in frozen- stored fish fillets (Burt, Dreosti, Jones, Kelman, McDonald, Murray, Simmonds, and Stroud, 1968; Mahon, 1962; Murray 1967), canned ' Rojowska, I., and R. Cyzanska, 1966. The influence Df sodium glutamate on the bacterial count in frozen foods. Paper presented at the Second International Congress of Food Science and Technology, Warsaw, Poland. tuna (U.S. General Services Administration, 1964) , or canned king crab (Jones, 1968) . Salt (usually sodium chloride) is usually included in a tripolyphosphate or a pyrophosi^hate solu- tion to increase its effectiveness. Studies by Dyer, Brockerhoff, Hoyle, and Fraser (1964) and Hellendoorn (1962) demonstrate that the optimum concentration of each of these com- pounds is related to its ionic strength and the ionic strength of the fluid in the surface layer of a treated fillet. Sodium chloride alone has been used in solutions for treating Dungeness crab meat (Farber and Lerke, 1968), shrimp meat (Commercial Fisheries Review, 1952), lobsters (Getchell and Highlands, 1957), or fish fillets (Holston and Pottinger, 1955). Citric acid has been used to inhibit discoloration of crab meat (Dassow, 1950; Gangal and Magar, 1963; Stansby and Dassow, 1963). Treatment with a single acidified brine solu- tion has already been suggested to inhibit textural deterioration and discoloration of Dungeness (Farber and Lerke, 1968), king (Dassow, 1950), and blue (Fellers and Harris, 1940) crab meat during subsequent storage. Sodium nitrite is used as a preservative and color fixative in several meat products and in certain seafood products such as smoked-cured salmon, sable fish, and shad (Furia, 1968). The use of nitrite in crab meat has been pro- posed (U.S. General Services Administration, 1965). Since under certain storage conditions outgrowth of Clostridium botulinum in seafoods is theoretically possible (Johannsen, 1961; Perigo and Roberts, 1968), nitrite has been used occasionally as a bacterial growth inhib- itor. Although the chemicals listed above have been used in several applications for preserving seafoods, evidence is lacking concerning their suitability in preserving frozen blue crab meat even in contrast to heat-pasteurized, heat-ster- ilized, or chilled meat. On the other hand, there is definite evidence that factors such as: rate of freezing, method of packaging, and storage temperature and its duration have to be carefully controlled in order to ijreserve frozen blue crab meat for 2 to 8 months with- out any significant loss in the desirable qual- ities of freshly picked meat (Strasser et al., 1971). Consequently, the objective of the 16 present investigation is to determine if a chem- ical pretreatment affects the quality of pre- served blue crab meat. MATERIALS AND METHODS Types of blue crab meat, methods of preser- vation by freezing, heating, or freeze-drying, methods of packaging, storage conditions, and methods of taste-panel evaluation are the same as described in Strasser et al. (1971). The 9-point rating scale used for the panel eval- uations is given in Figure 1-4. The following two procedures were used with the various preservative solutions listed below. Dipping Method Preweighed crab meat was placed into a strainer, dipped into the preserving solution for 30 sec, and then allowed to drain for 90 sec before further processing (freezing, pas- teurization, sterilization, or freeze-drying). Spray (Glazing) Procedure Just after freezing a sample of crab meat by immersion in food-grade Freon 12^ it was spread out on a stainless steel screen. The spraying solution was sprayed on the sample from a Sprayon Jet Pack which was kept ap- proximately 9 inches away from the sample. Spraying was done in a swaying action for about 15 sec (Fig. II-l). After another stain- less steel screen was placed on top, the sample was turned over to spray the other side. Then the sample was refrozen by Freon immersion. Chemical Preservative Solution Used over evenly with the powder before being frozen. Monosodium glutamate. — An aqueous solu- tion containing 2% monosodium glutamate was used for the dipping treatment and for glazing samples by the spray procedure. Instead of dipping or spraying treatments, four crab meat samples received a dusting with monosodium glutamate powder. The meat was spread out on stainless steel screens and dusted Ascorbic acid. — Although most of the crab meat samples treated with ascorbic acid were dipped in a 3% aqueous solution, a 1% solution was used for some of the samples. The 3% solution was also used to glaze several samples by the spray procedure. Two other samples were glazed using a 1 % spray solution but this solution also contained 1% carboxymethylcel- lulose (a thickening agent) to give a better coating effect. Condensed phosphates, salt, and citrate. — ■ Two different phosphate compounds were used. One solution contained lO^r sodium tripoly- phosphate plus 2% sodium chloride. It was used for the dipping treatment and for glazing samples by the spray procedure. The other solution contained 2% sodium acid pyrophos- phate alone, and it was used only for the dipping treatment. A third solution containing 5% sodium chloride and l^r sodium citrate was also used only for the dipping treatment. Sodium nitrate. — An aqueous solution con- taining 1% sodium nitrite was used for the dipping treatment. Tenox-6. — The spray procedure was used with a 3% solution of Tenox-6 in ethanol. ' Trade names are used to facilitate description ; no endorsement of product is implied. The chemical name for Freon 12 is dichlorodifluoromethane. Figure ll-l. — .Spraying of crab meat with protective chemical solutions. 17 Table II-l. — Organoleptic evaluation of blue crab meat treated with MSG before frozen storage.' Ty^e meat Method of freezing Packaging used" Overall taste results (9 point scale) after storing samples at indicated temperature and number of months' 0° F -20° F 2 4 6 8 2 4 6 8 Flake Freon immersion Lump Claw Flake^ " b Na blast NCG process Bag Bag V.P. Bag V.P. V.P. Bag Bag V.P. V.P. V.P. Bag V.P. V.P. 6.8 6.1 5.4 5.5 5.1 5.4 5.1 6.4 5.3 7. 6. 4.7 5.2 4.6 3.0 5.7 6.6 7.1 7.2 7.3 6.7 7.0 7.0 7.1 6.1 7.1 6.8 6.2 6.4 ' Crab meat dipped in a 2% monosodium glutamate (MSG) solution before freezing except for samples, footnoted * and *> in first column, which were dusted with dry MSG. ' The rating system is outlined in Figure 1-4. Based on 23 separate evaluations (295 individual ratings), the panel's average rating for overall taste in fresh crab meat was 6.8 and its range was 6.4 to 7.4. ' "Bag" refers to a polyethylene bag without vacuum while "V.P." refers to a three-ply laminate package heat-sealed while under vacuum. * Samples obtained from crabs caught near the Virginia coast (high-salinity water). Other samples from crabs caught in the Chesapeake Bay (low-salinity water). Tenox-6 is a commercial food-grade antioxidant which according to the manufacturer, Eastman Chemical Products, Inc., Kingsport, Tenn., con- tains: 10% butylated hydroxyanisole (BHA), 10% butylated hydroxytoluene (BHT), 6% propylgallate, 6% citric acid, 12% propylene glycol, 28% corn oil, and 28% glyceryl mono- oleate. Bacteriological Analyses Difco Plate Count Agar was used in the total count determinations and Difco Violet Red Bile Agar was used in the coliform count determinations. Standard plate count tech- niques (including incubation at 37° C for 48 hr) were used for both determinations. RESULTS AND DISCUSSION Monosodium Glutamate Dips or Dusts Panel evaluations of samples treated with monosodium glutamate before freezing are given in Table II-l for samples held at 0° F or —20° F and in Table II-2 for samples held Table II-2. — Organoleptic evaluation of blue crab meat frozen by Freon immersion and stored on dry ice.' Chemical treatment Overall taste results (9 point scale) after storing samples for indicated number of months '^ 2% sodium glutamate dip . . . 7.5 7.4 1% ascorbic acid dip 7.0 7.4 3% ascorbic acid dip 5.3 4.7 Dip in 10% sodium tri- polyphosphate plus 2% sodium ch oride 5.9 6.5 2% sodium acid pyro- 5.7 6.1 65 1% sodium nitrite dip 6.0 Dip in 1% sodium citrate plus 5% sodium chloride . . 5.8 5.8 Flake meat samples dipped in indicated solution, frozen and packaged in a polyethylene bag. " The rating system is ouUined in Figure 1-4. Based on 23 separate evaluations (295 individual ratings), the panel's average rating for overall taste in fresh crab meat was 6.8 and its range was 6.4 to 7.4. 18 on dry ice. Only the results for overall taste are presented in these tables since monosodium glutamate is known principally for its effect on the taste of foods and the ratings for ap- pearance, odor, and texture on these samples were not significantly different from those re- ceived by control samples (Strasser et al., 1971). It is quite evident from these i-esults that the temperature of frozen storage is a more important consideration than the method of packaging for these storage periods. A com- parison of these results with evaluations of samples which received the same freezing, packaging, and storage treatments but were not treated with monosodium glutamate (Stras- ser et al., 1971), suggests that treatment with this chemical did not significantly improve the taste of these samples. Ascorbic Acid Dips Panel evaluations of samples dipped in a 1 % or a S'^c solution of ascorbic acid before freez- ing are given in Table II-3 for samples held at 0° F or —20° F and in Table II-2 for. samples held on dry ice. Although ratings for appear- ance, odor, and texture were also obtained, the results for overall taste presented in these tables are sufficient for this discussion. In general, these ascorbic acid treatments depressed quality of the samples rather than enhanced it. Samples treated with ascorbic acid tended to receive the lowest ratings in com- parison with samples which received other chemical treatments. Table II-3. — Organoleptic evaluation of blue crab meat dipped in ascorbic acid solution before frozen storage.' Type Method of freezing Packaging Overall taste results (9 point scale) after indicated temperature and number storing of mon samples at ths= of meat 0° F -20= F 2 4 6 8 2 4 6 8 Flake Freon immersion Bag . . 4.0 5.3 6.8 6.9 ** " V.P. 6.3 n Bag V.P. 4.5 5.8 4.4 4.9 (*) M » Bag 5.3 4.6 5.0 5.6 »»B Bag V.P. 5.; } 6.0 5.2 »9 » Bag V.P. 3.7 4.2 3.6 4.1 •• •• •• •• • "B " V.P. 4.9 3.6 . . , . Lump n Bag V.P. 6.8 •• • 7.2 Claw »» Bag V.P. 5.5 •• •• 6.4 Flake Freon spray Bag V.P. •• 4.! ) 5.5 6.1 9* 9P Intermittent LN dipping Bag V.P. •• •• •• •• •• 6.( ) 5.8 7.1 n N2 blast NCG process Slow frozen' V.P. Bag •• •■ -• •• •■ 4.7 4.' 4.< ) 49 f» " V.P. 5.3 ' First four samples dipped in 1% ascorbic acid solution; other samples dipped in 3% ascorbic acid solution. ^ The rating system is outlined in Figure 1-4. Based on 23 separate evaluations (295 individual ratings), the panel's average rating for overall taste in fresh crab meat was 6.4 to 7.4. ' "Bag" refers to a polyethylene bag without vacuum while "V.P." refers to a three-ply laminate package heat-sealed while under vacuum. ' Not tasted because of poor appearance and ofF-odor. ^ Samples obtained from crabs caught near the Virginia coast (high-salinity water). Other samples from crabs caught in the Chesapeake Bay (low-salinity water). ° Crab meat placed in package before freezing in stiU air at —20° F. 19 Condensed Phosphate, Salt, and Citrate Dips Panel evaluations for overall taste of sam- ples dipped in a solution containing 10% so- dium tripolyphosphate plus 2',r sodium chlor- ide, or in a solution containing- 2^r sodium acid pyrophosphate, or in a solution containing b'^'r sodium chloride plus l^f sodium citrate before freezing are given in Table II-4 for samples held at 0° F or —20° F and in Table II-2 for samples held on dry ice. Since it was antici- pated that the use of these solutions would affect texture of the stored samples, results of the texture evaluations are presented in Table II-5. These treatments produced mixed results. The samples which had been treated with tri- polyphosphate plus salt or salt plus citrate were usually rated lower than untreated samples be- cause of a pronounced salty taste. Samples treated with sodium acid pyrophosphate alone received slightly higher ratings for texture as well as overall taste. However, all three of these chemical treatments resulted in lower ratings compared with untreated frozen-stored samples (Strasser et al., 1971). Employment of these chemicals was based on current theory concerning their effect on the functional properties of fish muscle proteins (Dyer, 1969). On the basis of this theory, it was assumed that these chemical treatments would be effective by producing an ionic strength in the order of 0.3 to 0.4 in the surface layer of the crab meat samples. From the re- sults actually obtained, it is suggested that this assumption may be erroneous for blue crab meat (and possibly for other invertebrate food species) . Obviously, some direct evidence is needed on the composition of crab muscle pro- teins and their extractability from raw and cooked crab meat. Sodium Nitrite Dips Panel evaluation of overall taste for samples diiiiied in a 1% sodium nitrite solution before freezing are given in Table II-6 for samples Table II-4. — Organoleptic evaluation of blue crab meat treated with phosphate, citrate, and salt before frozen storage: overall taste results.' Packaging used* Overall taste results (9 point scale) after storing samples at indicated temperature and number of months" treatment' 0° F -20° F 2 4 6 8 2 4 6 8 TPP-NaCl Bag »> 6 Bag V. P. »> Bag 4.1 4.4 4.7 4.2 " V. P. 5.8 5.9 4.4 4.9 " 6 V. P. 6.1 6.1 SAPP Bag V. P. " Bag 5.5 5.0 4.7 5.2 ** V. P. 6.5 6.2 4.8 5.2 NaCl-citrate Bag " V. P. " Bag 4.7 5.0 4.0 3.0 ** V. P. 5.6 4.8 5.1 4.4 6.0 6.1 6.7 5,5 6.6 5.6 5.9 6.7 6.1 5.9 6.2 6.9 5.3 6.1 7.1 6.1 6.2 ^ Flake meat samples frozen by immersion in Freon 12. ' The rating system is outlined in Figure 1-4. Based on 23 separate evaluation (295 individual ratings), the panel's average rating for overall taste in fresh crab meat was 6.4 to 7.4. ' Cral) meat dipped in a solution containing 10% sodium tripolyphosphate (TPP-NaCl) or in a solution containing 2% sodiimi acid pyrophosphate (SAPP) or in a solution containing 5% sodiimi chloride plus 1% sodium citrate (NaCl-citrate) before freezing. * "Bag" refers to a polyetheylene bag without vacuinn while "V.P." refers to a three-ply laminate package heat- sealed while under vacuum. ° Samples obtained from crabs caught near the Virginia coast (high-salinity water). Other samples from crabs caught in the Chesapeake Bay (low-salinity water). 20 Table 5. — Organoleptic evaluation of blue crab meat treated with phosphates, citrate, and salt before frozen storage: texture results.' Texture results (9 poiat scale) after storing samples at indicated temperature and number of months" Chemical treatment' Packaging used' 0° F -20° F Dry ice 6 8 TPP-NaCl Bag " 6 Bag V. P. w Bag 5.6 5.8 5.5 5.4 » V. P. 5.4 5.7 5.4 4.9 »' 6 V. P. Bag 6.4 5.3 SAP? Bag " V. P. l> Bag 6.3 4.6 4.8 5.8 »t V. P. 6.7 6.2 5.0 5.2 n Bag slaCl-citrate Bag V. P. W Bag 5.6 5.3 3.7 3.9 M V. P. 5.3 6.1 4.6 5.0 6.4 6.3 6.5 6 7.4 7 7 6.) 6.3 Bag 6.4 6. 7. 6.6 6.9 6. 7, 6.9 7.5 7.5 6.5 7.0 7.0 ' Flake meat samples frozen by immersion in Freon 12. ^ The rating system is outlined in Figure 1-4. ' Crab meat dipped in a solution containing 10% sodium tripolyphosphate plus 2% sodium chloride (TPP-NaCl) or in a solution containing 2C'f sodium acid pyrophosphate (SAPP) or in a solution containing 5% sodiiun chloride plus 1% sodium citrate (NaCl-citrate) before freezing. ' "Bag" refers to a polyethylene bag without vacuum while "V.P." refers to a three-ply laminate package seat-sealed while under vacuum. ° Samples obtained from crabs caught near the Virginia coast (high-salinity water). Other samples from crabs caught in the Chesapeake Bay (low-salinity water). held at 0° F or —20° F and in Table II-2 for samples held on dry ice. Ratings for appear- ance, odor, and texture were also made on these samples, but these results did not change as much as the overall taste rating. Taken as a group, these results indicate that the nitrite dip treatment had a neutral effect on the acceptability of these samples. These results are very similar to evaluations made of undipped samples which were frozen, packaged, and stored by similar methods (Strasser et al., 1971). On the other hand, the nitrite-treated samples which were frozen rapidly and stored at — 20° F received much higher ratings than samples which were dipped in some of the other chemical solutions used in this investigation. Various Combinations of Dip and Spray Solutions Several crab meat samples were glazed with various spray solutions either after a dip treat- ment and freezing or merely freezing them. The solutions used and the results obtained after storing these samples at — 20° F are sum- marized in Table II-7. Apart from Tenox-6, which was the only non-aqueous solution used, the composition of the spray solution had relatively little effect on the ratings received by these samples. These ratings are also generally similar to ratings received by crab meat samples which were frozen and stored under similar conditions but had not been treated with chemical solutions (Strasser et al., 1971). Although only tvvo samples were treated with sodium carboxy- methylcellulose, which is known as a coating agent, it is conceivable that the slightly higher ratings of these samples may be related to a slight preference shown for vacuum-packaged crab meat frozen and stored under similar con- ditions except for chemical treatments (Stras- ser et al., 1971). Considering all of these re- sults, it appears that a glazing treatment is at 21 Table II-6. — Organoleptic evaluation of blue crab meat dipped in 1% sodium nitrite solution before frozen storage. Overall taste results (9 point seal e) a fter storing samples at Type Method of freezing Packaging used- indicated tempe ■ature ; nd number of mon ths' of meat 0° F -20"^ F 2 4 6 8 2 4 6 8 Flake F'reon immersion Bag 6.5 7.0 6.9 6.2 "3 " Bag 7.0 7.0 »> " V. P. , , , , 6.2 " n Bag 4.2 4.3 4.9 4.4 " » V. P. 6.6 4.7 4.3 4.5 »»3 » V. P. 4.5 3.6 , . Lump » Bag Bag 5.2 7.4 " " V. P. 6.0 Claw Bag Bag V. P. 5.8 4.6 6.1 Flake Freon spray Bag V. P. 6.1 5.8 6.2 " Intermittent LN dipping N2 blast NCG process Slow frozen* Bag V. P. V. P. Bag V.P. .. •• •■ 5.9 6.3 5.7 5.4 6.8 7.4 5.5 5.4 ^ The rating system is outlined in Figure 1-4. Based on 23 separate evaluations (295 individual ratings), the panel's average rating for overall taste was 6.4 to 7.4 for fresh crab meat. ' "Bag" refers to a polyethylene bag without vacuum while "V.P." refers to a three-ply laminate package heat-sealed while under vacuum. ^ Samples obtained from crabs caught near the Virginia Coast (high-salinity water). Other samples from crabs caught in the Chesapeake Bay (low-salinity water). ' Crab meat placed in package before freezing in still air at —20° F. least equivalent to vacuum-packaging in main- taining the initial quality of crab meat during frozen storage. Glazing also imiiroved the storage stability of crab meat samples that had received unfa- vorable treatments before freezing. This im- provement was evident for frozen samples sprayed with ascorbic acid or tripolyphosphate- sodium chloride solutions compared with sam- ples that had been dipped in these solutions be- fore freezing and not glazed afterwards (Table II-7 versus Tables II-3 and II-4). However, samples that had been dipped in monosodium glutamate solution or a sodium nitrite solu- tion before frozen-storage were more accept- able and the glazing treatments did not sig- nificantly improve their acceptability (Table II-7 versus Tables II-l and II-6). Comparison of Freezing with Other Preservation Methods Several of the chemical solutions previously discussed were also used to dip fresh crab meat before preserving it by heat pasteurization, heat sterilization, or freeze-drying. These so- lutions are listed in Table II-8 together with the results of panel evaluations for overall taste after storing these samples for 2 to 8 months. The acceptability of these samples was gen- erally rated no better than the acceptability of similarly preserved and stored samples which were not treated with chemical additives (Strasser et al., 1971). Ratings for the heat- pasteurized samjiles in Table II-8 were usually between those obtained for frozen samples stored at — 20° F and samples stored at 0° F 22 Table II-7. — Organoleptic evaluation of blue crab meat treated with various dip and spray solutions.' Composition of dip solution Composition of spray solution Packaging used^ Overall taste results (9 point scale) after storing samples at —20° F for indicated number of months" 2% monosodium glutamate' 1% ascorbic acid plus 1% sodium carboxymethyl cel- lulose Bag 6.7 " 3% ascorbic acid Bag 5.8 '• 10% sodium tripoly- phosphate plus 2% sodium chloride V. P. Bag 6.0 6.6 " " V.P. 6.5 1% sodium nitrite 3% ascorbic acid Bag 6.1 " " V.P. 6.5 None 2% monosodium glutaniate Bag 6.3 •• " V.P. 6.8 *» 3% ascorbic acid Bag 6.6 " 3% Tenox-6 Bag 5.5 •• » V.P. 5.6 7.2 6.8 7.1 6.7 6.4 5,9 6.5 6.0 6.4 6.1 3.1 3.9 ' Flake meat samples dipped in solution indicated, frozen by immersion in Freon 12, then sprayed with solution indicated and refrozen by immersion in Freon 12. ^ "Bag" refers to a polyethylene bag without vacuum while "V.P." refers to a three-ply laminate package heat-sealed while under vacuum. ^ The rating system is outlined in Figure 1-4. Based on 23 separate evaluations (295 individual ratings), the panel's average rating for overall taste in fresh crab meat was 6.8 and its range was 6.4 to 7.4. ' Samples obtained from crabs caught near the Virginia coast (high-salinity water). Other samples from crabs caught in the Chesapeake Bay (low-salinity water). (Tables II-l, II-4, and II-6). None of the chemical treatments used appeared to improve the taste of the heat-sterilized samples even though sodium acid pyrophosphate and sodium nitrite treatments did improve their appear- ance. All of the freeze-dried samples received poor ratings. SUMMARY AND CONCLUSIONS In general, the chemical dip treatments did not improve the quality of preserved blue crab meat. Some of these dip treatments, such as ascorbic acid, actually depressed the quality of frozen-stored crab meat compared with un- treated samples stored under similar conditions. Other dip treatments, such as monosodium glutamate or sodium nitrite, had a neutral effect. It is conceivable that the failure of these dip treatments to improve the quality of preserved crab meat may be due to unknowTi biochemical differences related to species or processing conditions between blue crabs and other crustaceans. Although these dip treat- ments may have leached some chemical con- stituents from the samples, the results of bac- teriological examinations indicate that these samples were not significantly contaminated by these dip treatments (Table II-9). When some of the same chemical solutions were used to glaze crab meat just after freezing it, an improvement in the quality of the frozen- stored samples was usually observed. All of 23 Table II-8. — Organoleptic evaluation of preserved blue crab meat.' Chemical treatment'' Method of preservation Overall taste results (9 point scale) after storing samples for indicated number of months' 2 4 6 8 2% sodium glutamate Pasteurized 2% sodium acid pyrophosphate 1% sodium nitrite 1% sodium citrate plus 5% sodium chloride 2% sodium glutamate 2% sodium acid pyrophosphate 1% sodium nitrite 1% sodium citrate plus 5% sodium chloride 3% ascorbic acid 2% sodium acid pyrophosphate 2% Tenox-6 spray -"asteurized 6.6 5.6 5.6 6.2 " 6.4 7.1 5.0 5.8 ** •• 6.8 5.1 5.9 " 6.4 6..3 6.7 2.9 Sterilized 4.4 5.9 6.4 5.1 " 5.1 5.6 5.4 5.0 5.1 " 6.0 5.7 4.6 reeze-dried 3.7 4.7 4.4 •• ' Vacuum-packed flake meat stored at 34° F (heat pasteurized and heat sterilized samples) or at ambient (room) temperature (freeze-dried samples). ' Meat samples dipped into solution indicated except last sample which received a spray of Tenox-6 solution. ^ The rating system is outlined in Figure 1-4. Bast-d on 23 separate evaluations (295 individual ratings), the panel's average rating for the overall taste of fresh crab meat was 6.8 and its range was 6.4 to 7.4. these samples were stored at — 20° F, a storage temperature which is more suitable than 0° F to prolong the useful shelf life of crab meat for several months. Since ■ — 20° F storage conditions are not always obtainable in commercial practice, an investigation of the merits of glazing cryogen- ically frozen crab meat for storage at 0° F ap- pears worthwhile. ACKNOWLEDGMENTS John J. Powell and George M. Knobl, Na- tional Marine Fisheries Service, College Park, Md., provided facilities for part of the exper- imental work and shipped crab meat samples to FMC Laboratories during this investigation. Financial support was received from the Na- tional Marine Fisheries Service under contract number 14-17-0007-968. LITERATURE CITED ANDERSON, K., and C. E. DANIELSON. 1961. Storage changes in frozen fish. A compar- ison of objective and subjective tests. Food Technol. 15(2): 55-57. BANKS, A. 1951. The freezing and cold storage of herrings. Mod. Refrig. 54(4): 96-98. BAUERNFEIND, J. C, E. G. SMITH, and G. F. SIEMERS. 1951. Commercial processing of frozen fish with ascorbic acid. Food Technol. 5(6): 254-260. BURT, J. R., G. M. DREOSTI, N. R. JONES, J. H. KELMAN, I . McDonald, J. MURRAY, C. K. SIMMONDS, and G. D. STROUD. 1968. The handling of Cape hake. Fishing News International 7(6): 39-42. BYRD, G. C. 1951. Method of keeping the meat of shellfish in a fresh condition. U.S. Patent 2,546,428. COMMERCIAL FISHERIES REVIEW. 1952. Freezing and storing Alaska shrimp and Dungeness crab. Commer. Fish. Rev. 14(10) : 26. DASSOW, J. A. 1950. Freezing and canning king crab. U.S. Fish Wildl. Serv., Fish. Leafl. 374, 9 p. DYER, W. J. 1969. Eff^ect of brining and polyphosphate on yield and quality. In Rudolf Kreuzer (editor), Freezing and irradiation of fish, p. 167-171. 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Preservation Storage conditions Bacterial counts 5er gram of sample treatment' Temperature Months Total Count Agar Violet Red Bile Ager Not stored Not stored , , 1,300 35 " " 11,000 50 Frozen by 0< ' F 2 1,100 3,000 Freon immersion •■ 4 1,240 Heat pasteurized + 34° F 2 No growth No growth " 4 <100 Heat sterilized + 34° F 2 No growth No growth MSG dip -20° F n 0 51,000 70 •> +34° F 2 4 2 4 No growth <106/gram No growth No growth No growth No growth Ascorbic dip -20° F 9 0 2 4 5,200 4,900 330 120 <10/gram " 0° F " 4 1,790 TPP-NaCl dip -20° F (;) 0 2 4 32,000 3,500 2,010 1,000 <10/gram ** 0° F " 4 3,200 SAPP dip -20° F (=) 0 17,000 1,140 " + 34° F 0 2 4 No growth <100/gram No growth »» " (') 2 No growth No growth » " " 4 No growth Nitrite dip -20° F (;) 0 2 4 43,000 14,500 3,320 1,300 200 *• 0° F " 4 750 NaCl-citrate dip -20° F n 0 2 4 25,000 66,000 4,100 120 <10/gram " 0° F " 4 540 n + 34° F 1? (*) 2 4 2 No growth <100/gram No growth No growth No growth ' Description to abbreviations: MSG = 2'r monosodivmi glutamate solution Ascorbic = 3'f ascorbic acid solution TPP-NaCl := Solution containing 10% sodium tripolyphosphate plus 2% sodium chloride SAPP = 2% sodium acid pyrophosphate solution Nitrite =1% sodium nitrite solution NaCl-citrate = Solution containing 5% sodium chloride and 1% sodium citrate " Sample frozen by immersion in Freon 12 before storage. ^ Sample heat-pasteurized before storage. ' Sample heat-sterilized before storage. 25 DYER, W. J., and D. C. HORNE. 1953. Yellow discoloration in frozen lobster meat. Fish. Res. Bd. Can., Atl. Fish. Exp. Sta. Circ, New Series No. 2, 6 p. FARBER, L., and P. LERKE. 1968. A study of pasteurization as a means of extending the low temperature storage life of Dungeness crab and shrimp. U.S. Dep. Commer., Final Rep. Proj. Nos. 07-6-09102 and 99-6-09031, 39 p. FAULKNER, M. B., and B. M. WATTS. 1955. 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Symposium vid Svenska Institutet for Konser- veringsforskning 15 februrai 1961. 108 p. S. I. K. Report Number 100, Goteborg, Sweden. (English translation, 37 p.). JONES, R. 1968. Use of sodium acid pyrophosphate to retain natural moisture and reduce struvite in canned king crab (Paralithodes ssp.). U.S. Fish Wildl. Serv., Fish. Ind. Res. 4(2) : 83-89. LITTLEFORD, R. A. 1957. Studies on pasteurization of crab meat. Univ. Maryland, Seafood Processing Lab., Cris- field, Maryland, Bull. 2, 14 p. MAHON, J. H. 1962. Preservation of fish. U.S. Patent 3,036,923. MORTON, M. L., and W. J. DYER. 1956. Frozen oysters. J. Fish. Res. Bd. Can. 13(1): 47-51. MURRAY, C. K. 1967. Polyphosphate dips for fish. Ministry of Technology, Torry Research Station, Aberdeen, Scotland, Torry Advisory Note 31, 8 p. NORTON, K. B., D. K. TRESSLER, and L. D. FARKAS. 1952. The use of monosodium glutamate in frozen foods. Food Technol. 6(11): 405-411. OSTERHAUG, K. L., and R. W. NELSON. 1957. Cold storage of frozen Pacific oysters (Crassostrea gig as) . Effect of antioxidant and other treatments on keeping quality. Commer. Fish. Rev. 19(6) : 10-14. PERIGO, J. A., and T. A. ROBERTS. 1968. Inhibition of Clostridia by nitrite. J. Food Technol. 3(2): 91-94. POTTINGER, S. R. 1951. Effect of ascorbic acid on keeping quality of frozen oysters. Commer. Fish. Rev. 13(7): 5-8. STANSBY, M. E., and J. A. DASSOW (editors). 1963. Industrial fishery technology. Reinhold Publishing Co., New York, N.Y., 393 p. STANSBY, M. E., S. R. POTTINGER, and D. T. MIYAUCHL 1956. Refrigeration of fish. Part 3. Factors to be considered in the freezing and cold storage of fishery products. U.S. Fish. Wildl. Serv., Fish. Leafl. 429, 65 p. STRASSER, J. H., J. S. LENNON, and F. J. KING. 1971. Blue crab meat. 1. Preservation by freez- ing. Nat. Mar. Fish. Serv., Spec. Sci. Rep. Fish. 630, p. 1-13. U.S. GENERAL SERVICES ADMINISTRATION. 1964. Sodium acid pyrophosphate as optional in- gredient in canned tuna. Federal Register 29(75): 5225. 1965. Petition. Federal Register, August 31, 1965 (FAP 6A1829). [Cited in Commer. Fish. Rev. 27(11): 78.] 26 GPO 998-388 film'Sir''"" 5 WHSE 01814 UNITED STATES DEPARTMENT OF COMMERCE NATIONAL OCEANIC 8, ATMOSPHERIC ADMINISTRATION NATIONAL MARINE FISHERIES SERVICE SCIENTIFIC PUBLICATIONS STAFF BLDG. 67, NAVAL SUPPORT ACTIVITY SEAHLE, WASHINGTON 98115 POSTAGE AND FEES PAID U.S. DEPARTMENT OF COMMERCE OFFICIAL BUSINESS PERIODICALS LIBRARIAN marine: BiOLOGiCAL LABORATORY LIBRARY m/UODS HOLE, MA 02513