Utilization of Pacific Rockfish. 3. April Fisheries and Marine Service Technical Report No (9 tit t. I BR AO,

Transcription

1 Utilization of Pacific Rockfish. 3. By D.E. Kramer and M.D. Peters Ait-w (,t, irta All e. -eci (9 tit t. I BR AO, S Technology Services Branch Fisheries Management, Pacific Region Department of Fisheries and Oceans 6640 N.W. Marine Drive Vancouver, British Columbia V6T 1X2 Canada April 1979 Fisheries and Marine Service Technical Report No. 879 I Fisheries and Environment Canada Fisheries and Marine Service Peches et Environnement Canada Service des peches et de la mer

2 Fisheries and Marine Service Technical Reports These reports contain scientific and technical information that represents an important contribution to existing knowledge but which for some reason may not be appropriate for primary scientific (i.e. Journal) publication. Technical Reports are directed primarily towards a world wide audience and have an international distribution. No restriction is placed on subject matter and the series reflects the broad interests and policies of the Fisheries and Marine Service, namely, fisheries management, technology and development, ocean sciences, and aquatic environments relevant to Canada. Technical Reports may be cited as full publications. The correct citation appears above the abstract of each report. Each report will be abstracted in Aquatic Sciences and Fisheries Abstracts and will be indexed annually in the Service's index to scientific and technical publications. Numbers in this series were issued as Technical Reports of the Fisheries Research Board of Canada. Numbers were issued as Department of the Environment, Fisheries and Marine Service, Research and Development Directorate Technical Reports. The series name was changed with report number 715. Details on the availability of Technical Reports in hard copy may be obtained from the issuing establishment indicated on the front cover. Service des 'Aches et de la mer Rapports techniques Ces rapports contiennent des renseignements scientifiques et techniques qui constituent une contribution importante aux connaissances actuelles mais qui, pour une raison ou pour une autre, ne semblent pas appropries pour Ia publication dans un journal scientifique. Il n'y a aucune restriction quant au sujet, de fait, Ia serie reflete Ia vaste gamme des interets et des politiques du Service des peches et de Ia mer, notamment gestion des peches, techniques et developpement, sciences oceaniques et environnements aquatiques, au Canada. Les Rapports techniques peuvent etre consideres comme des publications completes. Le titre exact paraitra au haut du résumé de chaque rapport, qui sera publie dans la revue Aquatic Sciences and Fisheries Abstracts et qui figurera dans ('index annuel des publications scientifiques et techniques du Service. Les numeros de cette serie ont ete publies a titre de Rapports techniques de ('Office des recherches sur les pecheries du Canada. Les numeros , a titre de Rapports techniques de la Direction generale de la recherche et du developpement, Service des peches et de Ia mer, minis ere de l'environnement. Le nom de la serie a ete modi fie a partir du numero 701. La page couverture porte le nom de retablissement auteur oia l'on peut se procurer les rapports sous couverture cartonnee.

3 Fisheries and Marine Service Technical Report No. 879 April 1979 i UTILIZATION OF PACIFIC ROCKFISH. 3. A Quality Comparison of Sebastes alutus and Sebastes flavidus During Chill and Frozen Storage. by D. E. Kramer and M. D. Peters Technology Services Branch Fisheries Management, Pacific Region Department of Fisheries and Oceans 6640 N.W. Marine Drive Vancouver, B.C. V6T 1X2 This is the sixteenth Technical Report from the Technology Services Branch Vancouver

4 i i Minister of Supply and Services Canada 1979 Cat. No. FS 97-6/879 ISSN

5 LIST OF TABLES LIST OF FIGURES iii TABLE OF CONTENTS Page No. v... vi ABSTRACT vi i INTRODUCTION EXPERIMENTAL RESULTS II. 1. II. I I 1. IV. V I. MATERIALS A. Fish Samples 2 B. Additives Used for Treatments 2 C. Salt Determinations 2 D. Thiobarbituric Acid (TBA) Analysis Reagents.. 2 METHODS A. B. C. D. E. F. G. H. Preparation of Frozen Fillet Blocks 3 Thiobarbituric Acid (TBA) Determination 3 Tissue Chloride. 4 Thaw Drip 4 Ottawa Texture Measuring System 4 Organoleptic Evaluation 4 Statistical Treatment of Organoleptic Data 4 Proximate Analysis 6 VISUAL OBSERVATIONS... 6 THIOBARBITURIC ACID VALUES 6 TI SSUE CHLOR IDE... 7 THAW DRIP 7 A. Without TPP Treatment 7 B. With TPP Treatment 7 OTTAWA TEXTURE MEASURING SYSTEM DATA 8 A. OTMS Values for Prerigor Fish... 8 B. OTMS Values for Iced Fish... 8 C. OTMS Values for RSW-Held Fish... 9

6 iv TABLE OF CONTENTS (Cont'd.) Page No. VI. ORGANOLEPTIC EVALUATION... 9 A. Stati sti cal Compari son 9 B. Number of Undesirable Scores 11 VI I. PROXIMATE ANALYSIS.. 12 DISCUSSION I. VISUAL OBSERVATIONS. 12 II. THIOBARBITURIC ACID VALUES 12 III. TISSUE CHLORIDE 12 I V THAW DR I P 13 V. OTTAWA TEXTURE MEASURING SYSTEM DATA 13 VI. ORGANOLEPTIC EVALUATION 14 A. Species Comparison 14 B. Stowage Comparison 15 C. Treatment Compari son 16 CONCLUSIONS 17 ACKNOWLEDGEMENTS 18 REFERENCES 19 APPENDICES 39 A. Thiobarbituric acid values for S. alutus and S. flavidus with and without tripolyphosphate and erythorbate treatment after various periods of frozen storage at -28 C 40 B. Tissue chloride values for S. alutus and S. flavidus with and without tripolyphosphate and erythorbate treatment after various periods of frozen storage at -28 C 41 C. Thaw drip values for S. alutus and S. flavidus with and without tripolyphosphate and erythorbate treatment after various periods of frozen storage at -28 C 42 D. Ottawa Texture Measuring System values for S. alutus and S. flavidus with and without tripolyphosphate and erythorbate treatment after various periods of frozen storage at -28 C 43 E. Summary of organoleptic evaluation data for ~. alutus and ~. flavidus with and without tripolyphosphate and erythorbate treatment after various periods of frozen storage at -28 C 46 F. Number of taste panel scores considered to be undesirable, i.e. below 5 or for rancidity or saltiness above 1 49 G. Organoleptic evaluation score sheet 52 H. Proximate analysis data for S. alutus and i. flavidus 54

7 v LIST OF TABLES Table Page No. 1. II. Visual observations on ice- and refrigerated sea water-held S. alutus and S. flavidus Mean values for thiobarbituric acid determination on S. alutus and S. flavidus fillets (with and without erythorbate treatment> after various periods of frozen storage at -28 C 22 III. Mean values for tissue chloride (reported as % NaCl) for ice- and refrigerated sea water-held S. alutus and S. flavidus : 23 IV. V. V I. VII. Mean values for thaw drip of S. alutus and S. flavidus fillets (with and without tripolyphosphate treatment> after various periods of frozen storage at -28 C 24 Statistical comparison of organoleptic scores for two species of Pacific rockfish -- comparison of the species S. alutus and S. flavidus : 25 Statistical comparison of organoleptic scores for two species of Pacific rockfish comparison of the method of stowage 26 Statistical comparison of organoleptic scores for two species of Pacific rockfish -- comparison of tripolyphosphate and erythorbate treatments 27 V II I. IX. Summary showing the number of undesirable organoleptic scores for fillet blocks of two species of ice-held Pacific rockfish stored frozen at -28 C Summary showing the number of undesirable organoleptic scores for fillet blocks of two species of RSW-held Pacific rockfish stored frozen at -28 C ~

8 vi LIST OF FIGURES Figure Page No Stowage and preparation of fillet blocks for two species of Pacific rockfish 30 OTMS measurement of texture changes during frozen storage at -28 C for raw and cooked muscle from fillet blocks prepared immediately after catching 31 OTMS measurement of texture changes during frozen storage at -28 C for raw and cooked muscle from fillet blocks prepared after 7 days chill storage (ice) 32 OTMS measurement of texture changes during frozen storage at -28 C for raw and cooked muscle from fillet blocks prepared after 7 days chill storage (RSW) 33 Changes in organoleptic assessment of odor for fillet blocks stored at -28 C Changes in organoleptic assessment of flavor for fillet blocks stored at -28 C 35 Changes in organoleptic assessment of juiciness for fillet blocks stored at -28 C Changes in organoleptic assessment of tenderness for fillet blocks stored at -28 C 37 Changes in organoleptic assessment of texture for fillet blocks stored at -28 C 38

9 vii ABSTRACT Kramer, D. and M.D. Peters Utilization of Pacific rockfish. 3. A quality comparison of Sebastes alutus and Sebastes flavidus during chill and frozen storage. Fish. Mar. Servo Tech. Rep. No. 879, 54 p. The storage characteristics of Sebastes flavidus (yellowtail rockfish) have been compared with Sebastes alutus (Pacific ocean perch). Fillet blocks were prepared immediately after catching and from fish which were held 7 days in ice or in refrigerated sea water. The fillets were treated prior to freezing by dipping in water, 12% tripolyphosphate or 12% tripolyphosphate-l.25% erythorbate. Quality was assessed after various periods of frozen storage at -28 C with particular attention to changes in texture and development of oxidative rancidity. Organoleptic evaluation was carried out on cooked samples for odor, flavor, juiciness, tenderness and texture. Thiobarbituric acid value, tissue chloride and thaw drip were determined. Texture changes were studied using the Ottawa Texture Measuring System. Although the flavor of~. flavidus was rated lower than~. alutus, the difference in the two species is very small. Texture studies show S. flavidus is tougher than~. alutus, however, for fillets treated with tripolyphosphate there is very little species difference. We do not find rancidity (due to lipid oxidation) to be a problem in the white muscle if the fish are properly chill-stored (either in ice or in refrigerated sea water) and are held frozen at -28 C. However, rancidity is likely to develop mainly in the red muscle and organoleptic tests made on samples including the red muscle show the development of rancidity 1S more pronounced in~. flavidus than S. alutus. This can be controlled by the addition of erythorbate applied as a dip prior to freezing.

10 viii ~, RESUME Kramer, D. and M.D. Peters Utilization of Pacific rockfish. 3. A quality comparison of Sebastes alutus and Sebastes flavidus during chill and frozen storage. Fish. Mar. Servo Tech. Rep. No. 879, 54 p. On a compare les caracteristiques d'entreposage du Sebastes flavidus et du Sebastes alut~~ (sebaste du Pacifique). Certains blocs de filets ont ete prepares immediatement apres la prise, d'autres avec du poisson conserve durant sept jours dans la glace ou de l'eau de mer refrigeree. On a traite les filets avant la congelation en les trempant dans de l'eau contenant 12% de tripolyphosphate ou 12% de tripolyphosphate et 1.25% d'erythorbate. On a evalue la qualite a diverses periodes de l'entreposage frigorifique a C, en pretant une attention particuliere aux changements de texture et au rancissement par oxydation. On a fait une evaluation organoleptique portant sur l'odeur, la saveur, Ie caractere juteux, la tendrete et la texture d'echantillons cuits. On a determine la teneur en acide thiobarbiturique, Ie chlorure des tissus et l'exsudat. L'etude des changements de texture etait basee sur Ie systeme de me sure de la texture d'ottawa. Bien que la saveur de I. %lavidus se soit revelee moins prononcee que celie de S. alutus, la difference rests cependant minime entre les deux especes. Les etudes de texture revelent que~. flavidus est plus coriace que~. alutus mais, en ce qui concerne les filets traites au tripolyphosphate, la difference entre les deux especes est tres mince. Le rancissement (du a l'oxydation des lipides) du muscle blanc ne constitue pas un probleme si Ie poisson est correctement emmagasine a froid (soit dans la glace, soit dans l'eau de mer refrigeree) et s'il reste congele a une temperature de C. Cependant, il y a plus de risques que Ie rancissement se produise dans Ie muscle rouge; a cet effet, les tests organoleptiques effectues sur les muscles rouges revelent que Ie rancissement est plus prononce chez I. alutus. On peut y remedier en ajoutant de l'erythorbate lors du trempage preecedant la congelation.

11 1 INTRODUCTION This study is an extension of some previous work at this station (Tomlinson et al., 1973; Tomlinson et al., 1976) which investigated the feasibility-of-marketing some of the-various species of Pacific rockfish as a group with Sebastes alutus (using Pacific ocean perch as the market name). The yellowtail rockfish, Sebastes flavidus (which is commonly called greenies by British Columbia fishermen), was not included in the two previously published reports. However, for British Columbia, as well as for Washington and Oregon, S. flavidus is the principal species of rockfish landed other than S. alutus. S. flavidus accounts for about 45% of Canadian Pacific Coast rockftsh landings-other than S. alutus (Forrester and Smith, 1973). It is presently being landed in some quantity in Vancouver and in Prince Rupert (Wilson, 1977). S. flavidus landings in Vancouver from July to October of 1977 were 2,028,800 lbs (22.47% of the total rockfish catch), compared to S. alutus landings of 2,622,800 lbs (29.05% of the total rockfish catch). PrInce Rupert landings of S. flavidus from July to October of 1977 were 431,264 pounds (15.B6% of the total rockfish catch), compared to ~. alutus landings of 440,583 pounds (16.20% of the total rockfish catch). Studies 1 and 2 of this series on the keeping quality of Pacific rockfish indicate that fillets from~. reedi, ~. babcocki, ~. brevispinis and ~. pinniger are of sufficiently good quality to market with ~. alutus. ~. proriger was found to be inferior in keeping quality and it was recommended this species be marketed separately (Tomlinson et al., 1973). S. entomelas was reported to be inferior with regard to tenderness and texture and S. yaucispinus with regard to odor, flavor and rancidity (Tomlinson et!l., 976). Hence, these species also should not be marketed with S. alutus as Pacific ocean perch. - Best utilization of the S. flavidus resource would be to combine it with S. alutus and the other good food quality rockfish species using the established market name of Pacific ocean perch. However, this is desirable only if the organoleptic properties and the storage characteristics of this species can be shown to be similar to those of ~. alutus. Previous work (Tomlinson, 1976) indicated that some quality aspects of ~. flavidus (in particular, tenderness and development of rancidity) might be sufficiently different from~. alutus to warrant marketing it as a separate species. Fish fillets, in particular those intended for use in making frozen fillet blocks, are often dipped in a preservative solution to lessen fluid loss during thawing and to prevent oxidative rancidity. Sodium tripolyphosphate gives the most satisfactory results in reducing drip (Sutton, 1969), and sodium erythorbate is an effective antioxidant. This report compares frozen fillet blocks prepared from S. flavidus and S. alutus to permit evaluation of any differences in taste panel assessment of quality, instrumental measurement of texture, thaw drip and rancidity development during fifteen months of frozen storge. Solutions containing tripolyphosphate (used to decrease thaw drip and to preserve texture) and tripolyphosphate plus sodium erythorbate (used to control oxidative rancidity) were used to dip the fillets before making and freezing the blocks.

12 2 EXPERIMENTAL I. MATERIALS A. Fish Samples The fish samples S. alutus and S. flavidus were caught in October of 1976 by bottom trawl in Queen Charlotte-Sound. Data for the tows are given below: Species Date Time Location Depth S. alutus start 20 Oct 'N x 'W 110 fathoms finish 20 Oct ' N x ' W 110 fathoms S. flavidus start 21 Oct ' N x 'W 72 fathoms finish 21 Oct ' N x ' W 72 fathoms B. Additives Used for Treatments The sodium tripolyphosphate used was Freez-Gard Formula FP-19 (food grade sodium tripolyphosphate) obtained from Food Products Department, Calgon Corporation (Subsidiary of Merck & Co., Inc.) Pittsburg, Pennsylvania. The strength of dipping solution recommended by the manufacturer for use on seafood is 20 ounces per imperial gallon, which is a 12.5% solution. We used a 12% solution. The sodium erythorbate was NEO-CEBITATE (sodium erythorbate produced for meat curing) from Merck, Sharp & Dohme, Kirkland, Quebec. 1.25% solution was used. C. Salt Determinations Quantab chloride titrator 1176 was obtained from Ames Company, Division Miles Laboratories Inc., and used to determine the percent salt in the tissue. D. Thiobarbituric Acid (TBA) Analysis Reagents The extracting solution for the TBA determinations was made using reagent grade trichloroacetic acid. The 2-thiobarbituric acid (4,6-dihydroxy-2-thiopyrimidine, No. T-550) and n-propyl gallate (No. P-3130) were from Sigma Chemical Company. (Ethylenedinitrilo)-tetraacetic acid disodium salt (EDTA, analytical grade) was from Mallinckrodt Chemical Company. Malonaldehyde bis-(dimethyl acetal), 99+% (1,1,3,3-tetramethoxypropane) was from Aldrich Chemical Company. A

13 II. METHODS A. Preparation of Frozen Fillet Blocks species. 3 The scheme shown in Figure 1 was followed for each of the two After catching, the fish were divided into three groups: 1~ filleted immediately (control), 2) iced for 7 days before filleting, 3) held in refrigerated sea water (RSW) for 7 days before filleting. Immediately after filleting the fillets were divided into three treatment lots and dipped for two minutes with gentle stirring in the following solutions: 1) fresh water (water), 2) 12% sodium tripolyphosphate in fresh water (TPP), 3) 12% sodium tripolyphosphate % sodium erythorbate in fresh water (TPP+Ery). Each treatment lot of fillets was placed in a fillet block mold lined with a polyethylene sheet and frozen in a horizontal plate freezer at -40 C (-40 F) for 5 hours. The frozen fillet blocks were removed from the mold and glazed twice with fresh water (kept at O C with ice). They were then wrapped twice in polyethylene bags and stored in covered plastic tubs at -28 C (-18 F). After frozen storage times of 0, 5, 10 and 15 months, three one-inch cross sections (of the width of the block) were cut using a Butcher Boy meat saw. These were used for subsequent analysis. The block was then reglazed and placed back in frozen storage. B. Thiobarbituric Acid (TBA) Determination The TBA test was used as a measure of oxidative rancidity. The extraction procedure of Vyncke (1970), modified for a sample size of 8 grams, was used. Triplicate analyses were done on each sample. Because of the varying thickness of red muscle on the fillets, it is very difficult to be consistent in the amount of red muscle included in each analysis. In samples where oxidative rancidity has occurred, inclusion of a larger portion of red to white muscle would be expected to give a higher TBA reading (due to the higher lipid content of the red muscle and the presence of heme compounds which act as catalysts of lipid oxidation). As our TBA values were to be based on wet weight of tissue rather than on amount of lipid in the sample, we used only white muscle tissue (all red muscle was cut away).

14 C. Tissue Chloride Percent salt in the tissue of the samples was measured in duplicate using Quantab chloride titrators. D. Thaw Drip The outside glaze was chipped away from the cross section of the frozen block. This frozen section was then weighed and placed inside two plastic bags (one inside the other) and thawed for two hours in a 20 C water bath. The weight after thawing was determined and the loss in weight was calculated as % thaw drip. frozen weight - thawed weight (100) % thaw drip = frozen weight 4 E. Ottawa Texture Measuring System A Kramer shear press cell, modified for a IS-gram sample, was used. Tenderness values were measured on both raw and cooked samples. The raw muscle was cut into 1/4-inch cubes. The cooked muscle (wrapped in foil and steam cooked for 10 minutes) was flaked by hand to uniform pieces approximately 1/4 inch square. The pieces were uniformly packed into the cell and the texture value was recorded using a Daytronic Model 300D Transducer Amplifier-Indicator in combination with a Riken Denshi Speedex Recorder. F. Organoleptic Evaluation The ph of the thawed fillet pieces was measured using a Metrohm Herisau Model E488 ph meter. Pieces were then trimmed to approximately 1 inch x 2 inches x 1/2 inch, wrapped in aluminum foil and steam cooked for 10 minutes. Six pieces of fish (one from each of six different treatments) were presented to each of six experienced tasters at each sitting of the panel. The samples were judged for odor, flavor, tenderness, juiciness, texture, rancidity and saltiness. Comments were also requested for color of the cooked piece. G. Statistical Treatment of Organoleptic Data table: There are many variables in this study, as shown in the following Variable Species Stowage method Treatment Frozen storage time Number Component S. alutus, ~. flavidus contro 1 (no stowage), ice, RSW water, TPP, TPP+Ery 0, 5, 10, 15 months

15 5 The taste panel data was statistically analyzed (analysis of variance) in order to determine the effects of the various combinations of treatments and stowage methods on each species. Duncan's multiple range test was used to determine differences significant at the a=0.05 level (analysis was carried out by the University of British Columbia Computing Centre). The complete statistical analysis included looking at quality differences arising from interaction of the variables. For example, one type of treatment may be better for S. alutus and another different treatment better for S. flavidus. The various interactions possible at each frozen storage sampling time generate too much data to be included in this report. Therefore only those results showing statistically significant differences will be commented on in the discussion section. To see differences in quality caused by one variable only, the taste panel data is grouped in the following specific ways. 1. Species (Table V and Appendix E1) Under each quality assessment heading (e.g. flavor, odor, tenderness, etc.) the mean of all the scores obtained [i.e. includes all stowage methods (0, ice and RSW)-and all treatments (water, TPP and TPP+Ery)] for S. alutus (or S. flavidus) was calculated for each frozen storage period. - There are ntne different combinations of stowage method and treatment (Figure 1) for each species and there were six panel members -- therefore, each mean in Appendix E1 is calculated from 54 values. The means are then compared to determine if one score is significantly better than the other (using a 0.05). The plus signs in Table V indicate statistically significant (a=0.05) better scores. The mean value, standard deviation and range of the scores for each quality criteria are given in Appendix E1. 2. Method of Holding (Stowage) (Table VI and Appendix E2) The taste panel data was grouped to determine differences in quality caused by method of holding before filleting and freezing. Each value in Appendix E2 is the mean of all the scores (i.e. includes both species and the three treatment dips,-given for that particular stowage method under a given quality criteria (e.g. flavor). There are six different combinations of species and treatment and each was tasted by six different panel members. Therefore, each mean in Appendix E2 is calculated from 36 values. The plus signs in Table VI indicate statistically significant (a= 0.05) better scores. The mean value, standard deviation and range of the scores for each quality criteria are given in Appendix E2. 3. Treatment (Table VII and Appendix E3) The taste panel data was grouped in a similar manner to obtain Table VII and Appendix E3, an assessment of organoleptic quality differences due to changing the treatment dip. Each value in Appendix E3 is the mean of all the scores (i.e. includes both species and all storage methods) given for that particular treatment at each frozen storage time. There are six

16 6 different combinations of species and stowage method and each was tasted by six different panel members. Therefore, each mean in Appendix E3 is calculated from 36 values. The plus signs in Table VII indicate statistically significant (a= O.OS) better scores. The mean value, standard deviation and range of the scores for each quality criteria are given in Appendix E3. H. Proximate Analysis The samples were analyzed in duplicate for the following: I} protein (Steyermark, 1961) 2} lipid (using the Foss-let fat determining apparatus) 3} moisture (dried overnight at 105 C) 4} ash (Joslyn, 1970 and Horwitz et!l., 1970). I. VISUAL OBSERVATIONS RESULTS Table I compares observations on eyes, skin color, gills, flesh and gut made on the two species after holding for 7 days in ice or refrigerated sea water. After 7 days on ice, the appearance of S. flavidus indicated it held as well or slightly better than S. alutus. The development of sour odor in the gills and gut was not as pronounced in ~. flavidus as in ~. alutus. The slight belly-burn found in ~. alutus was not observed in ~. flavidus. Retention of skin color was better in S. flavidus. In refrigerated sea water for 7 days, the appearance of S. flavidus was again as good or slightly better than ~. alutus. The-eyes, gills, flesh, and gut characteristics were very similar for the two species. S. flavidus held its skin color very well but S. alutus showed some fading. S. alutus had a lot of scale loss and was colorless in the descaled skin areas. II. THIOBARBITURIC ACID VALUES All thiobarbituric acid values are very low. There is no apparent difference between species or between treatments over the IS-month frozen storage period. The mean values reported in Table II are from pieces of fillets which were at the surface of the block as well as from pieces of fillets which were at the center of the block. Comparison of surface samples with middle of the block samples showed no consistent differences in TBA values.

17 7 III. TISSUE CHLORIDE Table III gives the mean values obtained for tissue chloride (reported as percent NaCl) contained in the samples for each stowage method and treatment. The lower part of the table gives the combined mean and range of values for control plus iced fish (for all three treatments) and for RSW fish (for all three treatments). This allows for a comparison of species and for a determination of amount of salt uptake during holding in RSW. There is no difference in initial salt content for the two species S. alutus and S. flavidus. The combined mean value for fish held other than Tn RSW is 0.12% (chloride reported as % NaCl) for both species. The iced fish have slightly (but consistently) higher values compared with the fish frozen for controls. It appears that the loss of fluid during holding in ice is not reflected in an equivalent loss of chloride. Fish held in refrigerated sea water (RSW) have about 3- to 4-fold higher salt content than fish held in ice or frozen immediately. Salt uptake during 7 days storage in RSW is higher for S. alutus compared to S. flavidus. This may be merely a reflection of the size difference, as S. alutus is on the average smaller, and consequently, surface area per weight of fish will be greater for this species. IV. THAW DRIP Table IV shows the mean values (an average of 2 determinations in most cases) of thaw drip for all of the treatment groups. Each determination reflects an average of many (about 15 to 20) fish, as a cross section of a frozen block of fillets was used for this measurement (see Methods, part D). A. Without TPP Treatment Without TPP treatment, except for controls at the initial and 5-month frozen storage sampling times, S. flavidus had higher thaw drip values than S. alutus. - The values generally rose during the period of frozen storage and reached 10 to 15% thaw drip for ~. alutus and 14 to 17% for~. flavidus. B. With TPP Treatment The tripolyphosphate dip was effective in reducing thaw drip for both species at all frozen storage times. Except for RSW-held fish at 10 months frozen storage, TPP-treated S. alutus had lower thaw drip values than TPP-treated S. flavidus. The mean of all thaw drip values for TPP-treated S. alutus was 2.8% (standat"d deviation 1.2) compared with 3.4% (standard deviation 1.4) for TPP-treated S. flavidus.

18 8 Over the period of frozen storage, thaw drip values for fillets of both species treated with TPP rose about 1 to 2% during the first 5 months, were relatively stable between 5 and 10 months of frozen storage, then rose again about 1 to 2% during the 10- to 15-month frozen storage period. V. OTTAWA TEXTURE MEASURING SYSTEM OATA Figures 2, 3 and 4 and Appendix 0 give the OTMS data for comparison of treatments and species during 15 months of frozen storage. A higher OTMS score corresponds to a tougher fillet. Values for both raw and cooked muscle are plotted. For each treatment the range of values obtained is shown and the mean value (of 3 measurements) is circled. A. OTMS Values for Prerigor Fish The Ottawa Texture Measuring System values for fillets from fish filleted prerigor is given in Fig. 2 and Appendix 01. There is a large difference in OTMS values between the raw and cooked muscle. For raw tissue, the range of values obtained is small compared to the cooked values. There is not a large species difference. S. flavidus fillets with the TPP treatment are slightly more tender than S: flavidus without the TPP treatment, however the difference is very small. For cooked tissue, the range of values obtained in some cases is quite large. The water-dipped fillets show a definite species difference; S. alutus is more tender at all frozen storage times. Comparison of Tpp-treated fillets shows S. alutus is generally more tender than S. flavidus. However, the species difference is much smaller than in-the case of water-dipped fillets. B. OTMS Values for Iced Fish The Ottawa Texture Measuring System values for fillets from fish stored for 7 days in ice before filleting are given in Fig. 3 and Appendix 02. For raw tissue, there is no large species difference. For both species, fillets given the TPP treatment are more tender. The range of values for the raw muscle is quite small. For cooked tissue, the range obtained for iced fish is generally smaller compared to prerigor fish (although S. flavidus sometimes has a large range of values). For the water-dipped fillets, S. alutus is more tender than S. flavidus. Up to 5 months frozen storage~ there is very little species difference for the TPP-dipped fillets. After 10 months of frozen storage, S. alutus is slightly more tender than S. flavidus. Tpp-treated fillets of both species are much more tender than the water-dipped fillets.

19 9 C. OTMS Values for RSW-Held Fish The Ottawa Texture Measuring System values for fillets from fish held 7 days in RSW before filleting are given in Fig. 4 and Appendix D3. For raw tissue, there is no large species difference. The range of values obtained is quite small in all cases. S. flavidus fillets with a TPP treatment are slightly more tender than S. flavidus fillets which had a water dip. However, there is in general ve~ little difference in species or treatments. For cooked tissue, the range of values obtained is in general smaller than for prerigor fish for both species. The ranges obtained are much smaller for S. alutus than for S. flavidus. For both species, TPP-treated fillets are more tender than water-dipped fillets. Comparison of the water-dipped fillets shows S. alutus is slightly more tender than S. flavidus. Comparison of the TPP-treated fillets shows that with this - treatment there is very little difference in tenderness between the two species. VI. ORGANOLEPTIC EVALUATION A. Statistical Comparison The organoleptic results were treated statistically using analysis of variance to determine significant differences ata= Appendix E gives the mean, standard deviation and range of values from the taste panel data. These are grouped to compare the effects of species (Appendix E1), stowage method (Appendix E2) and preservative treatment (Appendix E3). Tables V, VI and VII summarize Appendix E using plus signs to indicate significantly better scores from the taste panel evaluations. 1. Species Comparison The plus signs in Table V indicate a statistically significant better mean taste panel score. The numerical values for this comparison are given in Appendix E1. S. alutus had significantly better organoleptic scores than S. flavidus for odor and flavor initially, for texture at 10 months of frozen storage, and for juiciness and flavor at 15 months of frozen storage. When taste panel scores for all 4 sampling periods were averaged, S. alutus had better scores for flavor, texture and tenderness. S. alutus had slightly better average scores for odor and juiciness than S.-flavidus but the differences were very small. Rancidity was detected slightly less in S. alutus. The higher average score for saltiness in S. alutus reflects the-higher rate of salt uptake in that species for the RSW-held fish.

20 10 2. Stowage Comparison Table VI and Appendix E2 compare organoleptic scores grouped to show differences caused by method of holding. The plus signs in Table VI indicate statistically significant better scores. The numerical values are given in Appendix E2. There were no significant differences between ice- and RSW-held fish in tenderness, texture, juiciness, flavor or rancidity levels initially or throughout the frozen storage period. Iced fish had a better odor score only at the initial sampling. Fish held in RSW were saltier at all sampling periods than those held in ice or filleted prerigor. Fillets from fish filleted prerigor were less tender and had coarser texture than the iced or RSW-held fish at all sampling periods. Also, prerigor fish were not as juicy as iced or RSW-held fish at the initial sampling. When taste panel scores of all four sampling periods were averaged, iced and RSW-held fish had significantly better tenderness, texture and juiciness scores than fish filleted prerigor. Fish held in RSW had a significantly higher saltiness score than iced or prerigor-filleted fish. 3. Treatment Comparison Table VII and Appendix E3 compare organoleptic scores grouped to show differences caused by treatment with tripolyphosphate and erythorbate. The plus signs in Table VII indicate statistically significant better scores. The actual numerical values are given in Appendix E3. The TPP and the TPP + erythorbate dips gave better tenderness scores at all the sampling times and better texture scores at the 5-, 10-, and 15-months frozen storage samplings. Fillets dipped in TPP and in TPP + erythorbate had better juiciness scores at the 10-month and 15-month frozen storage times. At the initial sampling period (zero frozen storage time) fillets treated with TPP or TPP + erythorbate had better tenderness scores and lower values for rancidity. The treated fillets were judged to be saltier than the water-dipped fillets. After 5 months of frozen storage, the fillets treated with TPP had better tenderness and texture scores. The addition of erythorbate improved the flavor and rancidity scores. After 10 months of frozen storage fillets treated with TPP had better tenderness, texture and juiciness scores than the water-dipped fillets. The addition of erythorbate gave an improvement in odor and flavor scores. As found at the initial sampling, treated fillets were judged to be saltier than the water-dipped fillets.

21 11 After 15 months of frozen storage, the TPP- and TPP + erythorbatetreated fillets had better tenderness, texture, JU1Clness, flavor and rancidity values than did water-dipped fillets. They were also rated as being saltier. When the taste panel scores from all 4 sampling periods are averaged, the TPP-treated fillets had improved tenderness, texture, juiciness and rancidity scores. The additional treatment with erythorbate improved odor and flavor and resulted in lower rancidity scores. The TPP and TPP + erythorbate dips resulted in fillets which have a salty taste. B. Number of Undesirable Scores Tables VIII and IX show the number of undesirable scores given by the taste panel for each quality criteria. Data is shown in the two tables for TPP- and TPP + erythorbate-treated fillets from iced and RSW-held fish. Complete data, including control fish, is given in Appendix F (the numbers under each characteristic in Appendix F, except for the totals, are for 6 panel members). 1. Iced Fi sh All scores for odor, juiciness, tenderness and texture for TPP-treated fillets from iced S. alutus were acceptable; however, there were some unacceptable scores for flavor, rancidity and saltiness. When treated with TPP + erythorbate, all flavor scores for S. alutus fillets were acceptable and there was only one unacceptable-rancidity score. All tenderness scores for TPP-treated fillets from iced S. flavidus were acceptable but there were some unacceptable scores for odor, flavor, rancidity, saltiness, juiciness and texture. When treated with TPP + erythorbate all odor and flavor scores were acceptable and there was only one unacceptable rancidity score. 2. RSW Fish Fillets from S. alutus or S. flavidus held in RSW (in particular those treated with TPP)-had a large number of high saltiness scores. S. alutus had more high saltiness scores than ~. flavidus. - All TPP-treated fillets from RSW-held S. alutus had acceptable scores for juiciness and texture but some undesirable scores for odor, flavor, rancidity, saltiness and tenderness. The addition of erythorbate reduced the number of undesirable rancidity scores. All RSW-held S. flavidus treated with TPP had acceptable scores for odor, flavor, juiciness, tenderness and texture but some unacceptable scores for rancidity and saltiness. The addition of erythorbate reduced the number of undesirable rancidity scores to only one.

22 12 VII. PROXIMATE ANALYSIS Appendix H shows the proximate analysis data (protein, moisture, ash and lipid) for the species, stowage methods, and treatments averaged from the 4 sampling times (0, 5, 10 and 15 months frozen storage). I. VISUAL OBSERVATIONS DISCUSSION Visual observations indicated S. flavidus and S. alutus were of similar quality after holding 7 days in ice. Eyes, gills, flesh and gut of the two species were of similar quality after holding 7 days in RSW. However, the skin appearance of S. flavidus was much better than S. alutus after 7 days in RSW. S. alutus had considerable scale loss during-rsw stowage and color was essentially gone in the descaled areas. S. flavidus suffered very little scale loss during stowage in RSW and consequently held its color very well. II. THIOBARBITURIC ACID VALUES TBA values were used as an indication of rancidity. In this study there is no apparent difference in TBA values for the two species or for the different treatments over 15 months of frozen storage. The values are all very low. The very low TBA values no doubt reflect the exclusion of red muscle (which is higher in lipid and is expected to go rancid more quickly because the heme compounds occurring in this tissue act as catalysts of lipid oxidation). Red muscle was excluded from the chemical test for rancidity because of the difficulty in getting the same red muscle to white muscle ratio for each sample. Red muscle was included in the samples used for organoleptic testing and the taste panel found a higher rate of rancidity than the TBA values would indicate. Removal of as much red muscle as practical during preparation for frozen storage will result in longer storage life. This has been shown to be of particular importance for ~. flavidus (Stansby and Dassow, 1949). III. TISSUE CHLORIDE When S. alutus and S. flavidus were held other than in RSW (frozen prerigor or held in ice), the-two species had the same tissue salt concentration. After 7 days chill storage in RSW, S. alutus had a higher tissue salt concentration than S. flavidus. -

23 The lower % salt found in S. flavidus could be simply the result of the size difference. S. alutus were smaller than S. flavidus, so surface area based on weight of ftsh would be greater for ~. alutus. ~. flavidus retained their scales better during the holding period in RSW; S. alutus had appreciable scale loss during holding in RSW. Also~. flavidus-appears to have a thicker skin compared with S. alutus. These factors no doubt contribute to the lower rate of salt uptake in ~. flavidus. For both species, the levels of salt found were not so high as to be objectionable for marketing. IV. THAW DRIP A sodium tripolyphosphate dip is in general use commercially for fish fillets which are going into frozen storage. It reduces undesirable textural changes and decreases thaw drip. Thaw drip not only represents a loss in weight and therefore a loss in saleable product, it represents loss of tissue fluid which results in a less juicy, less flavorful fillet. Our results show that the tripolyphosphate treatment effectively reduced thaw drip for both S. flavidus and S. alutus, at all frozen storage times. Although~. flavidus generally had a higher thaw drip value than ~. alutus, the thaw drip values obtained for both species, when given the TPP treatment, are in the acceptable range. Sutton (1969) found high drip losses for prer;'gor unprocessed cod (the values ranged from 12 to 24%). For cod iced for up to 6 days, he found much lower values (a range of 2 to 10%). We do not find such large differences between prerigor fish and ice- or RSW-held S. alutus or S. flavidus. In fact, for the initial sampling of S. flavldus, untreated prerigor fillets had less thaw drip than the untreated fillets from ice- or RSW-held fish. V. OTTAWA TEXTURE MEASURING SYSTEM DATA Other investigations (Tomlinson, 1976) have indicated that toughness is the problem of most concern for the species S. flavidus. Treatment with TPP should improve the texture and minimize undesirable changes during frozen storage. The Ottawa Texture Measuring System (OTMS) is an instrumental, and therefore objective, measurement of texture. A firmer (or tougher) sample results in a higher OTMS reading. The OTMS values for both raw and cooked tissue are included in this report. Both S. alutus and S. flavidus have firmer texture after cooking (as shown in Figs. 2, 3 and-4, the cooked samples are the higher lines on each graph). 13

24 The raw tissue OTMS values indicate only minor differences between species, methods of stowage, TPP and erythorbate treatments and time in frozen storage. Thus, the texture of cooked samples can not be predicted from raw tissue OTMS values. The OTMS values for cooked muscle showed much greater differences with species, method of stowage, TPP and erythorbate treatments and time in frozen storage than the OTMS values for raw muscle. As cooked muscle texture is of much importance to the consumer, these differences are very important in regard to any recommendations to be made for handling and storage prior to freezing. Both stowage method and tripolyphosphate treatment had an effect on OTMS score, and consequently, on texture. The toughest fillets of each species were those from fish filleted prerigor. For these fillets, a tripolyphosphate treatment gave some improvement in texture. Storage in ice or RSW for 7 days before filleting resulted in much improved texture. Treatment of these samples with TPP resulted in further improvement of the texture. There was very little difference in texture between the two species if the fillets were taken from fish held through rigor in either ice or RSW and the fillets were given a tripolyphosphate treatment prior to freezing. VI. ORGANOLEPTIC EVALUATION Taste panel evaluation of quality is a very important part of any study on storage characteristics of food, as it is the best measure of eating quality and will reflect consumer preferences. Statistical comparison of the mean taste panel scores will show species, stowage and treatment differences. However, number of undesirable scores is perhaps a better measure of what will result in acceptance or rejection by the consumer. A. Species Comparison 1. Statistical Comparison All mean values obtained for the taste panel scores were acceptable for both species. S. alutus was statistically significantly better in some of the quality assessments (Table V). However, as shown in Appendix E1, the actual numerical values for the means are very close (0.5 point difference or less in all but one case) and the range of values obtained is quite wide, but very similar, for both species. The largest species difference (in flavor) is found after 15 months of frozen storage. The S. alutus value (7.1) is 0.8 point higher than the S. flavidus value (6.3). The values in Appendix E1 include all storage methods and treatments. If the prerigor and water-dipped fillets are excluded, the means for flavor at 15 months frozen storage are: S. alutus = 7.2, and S. flavidus = 6.7, a difference of 0.5 point. For both species, the numbers correspond to a loss of fresh flavor, but do not show the appearance of off-flavor (see Appendix G). 14

25 15 2. Number of Undesirable Scores For ice-held fish (Table VIII), the water-dipped S. f1avidus fillets received about twice the number of undesirable scores from the taste panel compared with water-dipped S. a1utus fillets. Treatment with TPP and erythorbate reduced the number of-undesirable scores from 11 to 3 for S. a1utus and from 20 to 4 for S. flavidus. - In both prerigor and iced fish (Appendix F1 and F2), S. f1avidus had a higher number of undesirable rancidity scores than S. a1utus for untreated fillets. Treatment of fillets with erythorbate-reduced the undesirable rancidity scores to only one for each species. The numbers of high saltiness scores in fillets from prerigor or iced fish were about equal for the two species. For RSW-held fish (Table IX), as was found for ice-held fish, water-dipped S. f1avidus fillets received almost twice as many undesirable taste panel scores as did water-dipped S. alutus fillets. Treatment with TPP and erythorbate reduced these scores (excepting the ones for saltiness) to 4 for -S. a1utus and 1 for -S. f1avidus. ~. a1utus held in RSW had a much larger number of high saltiness scores than S. f1avidus held an equal time in RSW (Appendix F3). These results agree with the measurement of tissue chloride levels using Quantabs. It is concluded that species is less important than other factors in influencing quality as measured organoleptically. B. Stowage Comparison 1. Statistical Comparison With the exception of the saltiness scores and the initial odor scores (Table VI), there were no significant differences between ice- and RSW-held fish in taste panel quality assessments. Fillets from the RSW-stored fish were definitely saltier than iced or prerigor fish fillets at all sampling periods (Appendix F). Tenderness and texture scores for iced and RSW-held fish were superior to the scores obtained with fish filleted prerigor. The difference in mean scores was 1 point or greater, and therefore represents a definite quality difference. 2. Number of Undesirable Scores The number of unacceptable tenderness and texture scores obtained from the taste panel for prerigor fish (Appendix F1) is very large (32 for S. alutus and 56 for S. flavidus) compared to iced (6 for S. a1utus and 9 for - S. f1avidus) or RSW-he1d (1 for -- S. a1utus and 5 for S.-f1avidus) fish.

26 Within each stowage group, S. flavidus has more undesirable scores than S. alutus. This shows that there is a very large stowage effect and a smaller species effect on tenderness and texture of the cooked fillets. C. Treatment Comparison 1. Statistical Comparison TPP-treatment has been shown to improve the textural properties of cooked cod muscle (Sutton 1969). Our data show that sodium tripolyphosphate-treated rockfish fillets are significantly more tender and have much finer texture than water-washed fillets (Appendix F). 2. Number of Undesirable Scores TPP-treatment of iced or RSW-held S. alutus and S. flavidus (see Appendix F) eliminates the species difference for tenderness and texture, as judged by the number of undesirable scores for the control samples (prerigor fish fillets). The lower thaw drip for the TPP-treated fillets is also reflected in higher juiciness scores. Use of erythorbate reduces the number of undesirable rancidity scores to totals of only 3 for S. alutus and 2 for S. flavidus for all stowage methods and all frozen storage periods. - 16

27 17 CONCLUSIONS 1. Visual observations on S. alutus and S. flavidus held 7 days in ice or refrigerated sea water indicated they were of similar quality. However, skin appearance of S. alutus held in refrigerated sea water was poor due to scale loss and fading of red color. 2. Thiobarbituric acid values determined on the white muscle during frozen storage at -28 C did not show a difference in the two rockfish species, ~. alutus and~. flavidus. 3. ~. alutus has a higher rate of salt uptake than ~. flavidus during storage in refrigerated sea water, possibly due to its smaller size. However, salt uptake is not a problem with either species as levels are not high enough to be objectionable for marketing. 4. Although thaw drip is higher for S. flavidus compared with S. alutus, treatment of the fillets with a sodium tripolyphosphate dip (12% solution) reduced thaw drip in both species to acceptable levels for up to 15 months frozen storage at -28 C. 5. Ottawa Texture Measuring System values for raw muscle show very little dependence on species, methods of stowage, sodium tripolyphoslphate and sodium erythorbate treatments and time in frozen storage. 6. Ottawa Texture Measuring System values for cooked muscle show fish filleted prerigor are much tougher than fish filleted after storage in ice or refrigerated sea water and that S. flavidus fillets are tougher than those from~. alutus. Treatment wtth a sodium tripolyphosphate dip (12% solution) was effective in improving texture for both species. For sodium tripolyphosphate-treated fillets from fish held in ice or in refrigerated sea water, there was virtually no species difference. 7. Organoleptic evaluation of cooked fillets indicates S. alutus is slightly superior in odor and flavor to S. flavidus and that rancidity is much more of a problem in ~. flavidus~ Treatment of the fillets by dipping in a sodium tripolyphosphate-sodium erythorbate solution (12% and 1.25% respectively) improved the storage characteristics and made species differences insignificant. 8. Organoleptic evaluation of tenderness and texture of cooked muscle shows S. flavidus to be tougher and coarser than S. alutus. Treatment with a-sodium tripolyphosphate solution (12%) improved the tenderness and texture and eliminated the species difference. 9. Organoleptic assessment of juiciness indicates there is no problem for either S. alutus or S. flavidus for up to 15 months frozen storage at -28 C. - -