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Abstract This investigation aims to the possibility of utilizing the bolti fish which obtained from High Dam Lake specially large size and underutilized for manufacturing imitated shellfish product and compared with natural shell fish and also, aims to study the possibility of gamma irradiation at doses 1, 3, and 5 kGy for keeping the quality of imitated fish product during cold storage. Therefore whole fish boIti were obtained from Misr Aswan Company. The whole fish were dressed and minced. The obtained minced fish was washed three times with sodium bicarbonate (0.2%), distilled water and sodium chloride solution (0.15%). The cryoprotectants ingredient (sorbitol, sucrose and tripoliphosphate) was added to washed minced fish for producing intermediate product (surimi). The final product (imitated fish) was manufactured by adding egg white, starch, corn oil, natural color and flavor of shrimp and crab according to special formula for shrimp and crab. The imitated shrimp sample were irradiated at doses 1, 3 and 5 kGy and cold stored. The obtained results could summarized as following: A- Yield of bolti fish: - The results indicated that the big size of fish gave high yield as compared with small size and the average of the yield (dressing percentage) ofbolti fish was 42.8 %. B- Effect of washing on chemical composition, quality attributes and microbiological load of bolti mince: - l-Washing process caused an increase in moisture content of fish mince to 81.1 % after third washing and fat and ash 141 content were reduced from 17.66 and 5.25 % (on dry weight basis) to 8.25 and 3.12 % (on dry weight basis) respectively. 2-Washing steps increased protein content and salt extractable protein from 75.53 % (on dry weight basis) and 45.26 ”Y 0 to 88.25 (on dry weight basis) and 88 %respectively. 3-TVN and TBA were decreased after washing steps from 9.93 mg / 100g sample and 0.88 mg / kg to 3.12 mg / 100g sample and 0.72 mg / kg respectively, after washing. 4-WHC was increased after washing steps from 74.930 A to 82.26 % on the other hand pH was slightly decreased after washing process from 6.78 to 6.57. 5-Washing reduced the Total bacterial count, Psychrophilic bacteria, yeast and mold counts. 6-Washing process reduced the mineral contents (Ca, P, Na, K and bp) of boIti mince. C- Sensory evaluation for choosing the best flavor concentration of shrimp and crab :- I-Results showed that the best concentration of flavors could be used in imitated shrimp were 1 and 2 gm / kg from shrimp Aspin flavor and American flavor respectively. 2-The results indicated that the best concentration of American crab flavor in imitated crab was 2 gm / kg. D- Yield of surimi:- Yield of surimi was 42.38% and washed mince was 32.28%. E- Chemical composition of natural and imitated shrimp and crab: 1- Moisture content of natural and imitated shrimp and crab were 74.86, 77,81, 78.02 and 79.33 % respectively. 2-Results concluded that protein, fat, ash and carbohydrate contents of natural and imitated shrimp were 84.76, 47.68,86.71 and 55.640 A; 8.47, 7.66, 4.69 and 4.89 %; 4.73, 6.13, 8.32 and 11.22 %; 2.03, 38.53, 0.27, 28.25 % ( on dry weight basis), respectively. F- Effect of cooking on the quality attributes of natural and imitated shrimp and crab:- I-Salt extractable protein of natural and imitated shrimp were 32.7 and 53.4 for unheated sample and were reduced by heat treatment to 25.8 and 47.4 % respectively. 2-Similarly, salt extractable protein of natural and imitated crab was decreased after heating to 29.10 and 39.49 % respectively. 3- Heating process slightly reduced TVN of natural and imitated shrimp from 24.6 and 2.11 mg/lOOgto 24.2 and 1.69 and mg/ 100grespectively. 4- Similarly, heating process slightly reduced TVN of natural and imitated crab from 22.30 and 1.83 mg/100g to 22.0 and 1.45 mg/lOOgrespectively. 5- Heating process caused slightly increased the TBA and pH of natural and imitated shrimp and crab. 6-Heating process reduced WHC of imitated shrimp and crab. 143 G- Effect of cooking (heating process) on microbiological parameters of natural and imitated shrimp and crab:- Heating process decreased total bacterial count, psychrophilic bacteria, mold and yeast of natural and imitated crab. H- Effect of irradiation by different doses on chemical composition and quality attributes of imitated shrimp and during cold storage period:- 1-Results indicated that moisture, protein and fat contents of imitated shrimp were 74.69,47.09 and 7.74 % (on dry weight basis) respectively and the chemical composition of samples were not change after irradiation where as slightly decreased during cold storage. 2- Irradiation with doses 1, 3 and 5 kGy caused slightly increase in TBA after irradiation and there was gradual increase in TBA during cold storage period. 3- WHC was slightly increased after irradiation and there was a gradual decrease in WHC. 4- pH of imitated shrimp was slightly increase after irradiation and gradual decrease during cold storage period. 5- Salt extractable protein was not affect after irradiation and during cold storage period. 6- Irradiation treatment by doses 1, 3 and 5 kGy caused slightly increase in TVN and there was a gradual increase during cold storage. 144 J- Microbiological analysis of imitated shrimp during cold storage: 1-Total bacterial count, psychrophilic bacteria, yeast and mold of imitated shrimp was 2xIO 2, IxI02, <10 and <10 cfu /g respectively. 2- Irradiation treatment caused a significant decrease in total bacterial count, psychrophilic bacteria, mold and yeast and this decrement was increased as increase in dose. 3- Total bacterial count was increased during cold storage in all treatment. 4- Psychrophilic bacteria of unirradiated samples and eradiated with 1 kGy was increased during cold storage. While there were no growth in the initial period of cold storage but there was a growth at the end of cold storage in irradiated imitated shrimp with doses 3 and 5 kGy. 5- cold storage period caused increase in yeast of unirradiated imitated shrimp but irradiated imitated shrimp did not show any growth at the initial period of cold storage and there was a gradual growth at the end of cold storage. 6- Mold growth was detected at the end of cold storage period of all treatment. K- Sensory evaluation of imitated shrimp during storage period:- Results indicated that irradiation process did not affect in the appearance of imitated shrimp. While mold growth started at the surface of unirradiated samples and the panelists rejected these samples. It could be concluded that using of boIti fish as a raw material for processing of imitated fish (crab and shrimp), also using of shrimp flavor (Aspin) at 1 gm / kg was the best treatment. In addition it could be concluded that gamma irradiation at doses of 3 kGy was the best treatment under investigation for extending the shelf life of imitated shrimp to 16 weeks which cold stored without a deleterious effects on their chemical, microbiological and sensory properties compared to 7 weeks for control sample. |