| China water area is abundant in freshwater fishes. The freshwater fish is a good source of high quality protein, but the industrialization level was low in production scale, which leading a tremendous waste of freshwater fish resource. Currently, the study of freshwater fish mainly concentrated in the drying, processing, flavor and quality control.This thesis was focused on developing processing methods on grass carp relating leisure food, the storage characteristics and processing methods studied in this thesis may bring economic benefits for the enterprises and provide theoretical basis and production guidance in industry and scientific research.In order to study the curing process of grass carp and its impact on the flavor. Optimizing the salting processing treatment from the content of salt, curing time and curing temperature with fresh grass carp. The optimal condition is as follows: the ratio of salt 10.89%, time18.12 h and temperrture 9.23℃. The flavor components of grass crap under different salting time were studied. Totally 27 kinds of flavor components were detected on the sixth day. Hexanal was the highest level with a content of 24.82%. Isopentyl ester was in a lower level with a content of 15.81%. 48 kinds of flavor components were detected on the twelfth day. Hexanal was the highest level with a content of 31.74%. Octane was at second level with a content of 15.28%.In order to study the drying process of the grass carp and changes in various parts of the water during the dewatering process.The LF-NMR was used to determine the moisture changes in fresh grass carps fillets,salted and dried fillets. During the curing and drying process, the main weight loss was the immobilized water. The drying process was a layer by layer drying. The free water evaporated first and then the immobilized water and the constitutional water began evaporated. Comparing the drying characteristics and the quality of dried samples of hot air drying and vacuum microwave drying, final results indicated that vacuum microwave drying was more efficient and leading to a better quality in dried grass crap fillets. The vacuum microwave dried fillets were lighter in color whereas the hot air dried grass carp fillets were darker and more yellow. For rehydration, rehydration rate constants of the salted grass carp fillets from vacuum microwave drying were significantly higher than those from hot air drying.In order to study processing technology of the grass carp, the study mainly from four aspects: desalination,processing, flavor and product quality.The desalination was studied. The optimal condition of desalination is: water temperature 30℃, the ratio of water to fish fillets10:1, desalting time 180min. The desalted fish fillets could directly for process without adding salt. The optimal condition of frying is: frying temperture 170℃, frying time4min, seasoning time 3 min and dosage of millet wine 1.5%. 48 kinds of flavor components were detected in fried grass carp. The main flavor components of fried grass crap were limonene, 2- methylbutyryl aldehyde and hexanal. Three kinds of coating materials (CMC, sodium alginate and agar) were used to the decrease of oil content in fried grass carp. 10%-15% oil was reduced after coating pretreatment. Oil content can significantly be reduced with Sodium alginate coating. In order to study storage characteristics of product during storage. The changes of AV and POV were determined under room temperature and through high temperature storage experiment. The AV level rised quicker than that of POV. For the high temperature and high pressure sterilized fried grass carp, the AV was the key factor in shelf life. 0.3 g/kg tea polyphenol added could reduce the AV for 26.47% and the POV for 23.09%. |
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