The Study On The Processing Conditions And Quality Attributes Of A Ready-to-eat Fried Loach

There are few ready-to-eat processed products from loach(Misgurnusa nguillicaudatus) in the market in the recent time. Loach processing into ready-to-eat foods is one way to confer higher added-value. In the present study, loach from Bayan country, Heilongjiang Province was used the raw material, and investigated for its processing conditions including deodorizating, curing, pre-drying and oil frying, aiming to obtain a ready-to-eat fried loach product. The suitable processing conditions were selected from sigle experiment trial. Main chemical compositions, volatiles and textural characters of the ready-to-eat fried loach were evauated, and amino acids in protein fraction as well as fatty acids in lipid fraction were determined by respective analyses. At the same time, changes of two microbiological indices and lipid oxidation of the stored ready-to-eat fried loach were analyzed. The main results obtained in the present study were surmarrized as following.(1) The optimal processing conditions of the ready-to-eat fried loach were selected. The fresh loach was decapitated and gut contents were removed before deodorization in a solution(used at half weight level of the loach) containing 1.0% Na HCO3 and 0.5% Na Cl for 2 h. After that, the loach was cured in a solution(also used at half weight level of the loach) containing 4% Na Cl and 8% cooking wine for 2 h, dried at 55 °C for 2 h, and then fried in soybean oil at 180 ~ 200 °C for 90 s.(2) The nutritive and chemical qualities of the ready-to-eat fried loach were evaluated. The moisture content of the ready-to-eat fried loach was significantly decreased(p<0.05), while the protein, fat, ash and salt contents of the ready-to-eat fried loach was significantly increased. Eighteen amino acids in the protein fraction were detected in the ready-to-eat fried loach; the proportion of the essential amino acids to total amino acids was as high as 39.19%. The essential fatty acids in the lipid fraction of the ready-to-eat fried loach accounted for about 13% to the total fatty acids, with increased level of 225% compared with the fresh loach. Oleic acid and linoleic acid level in lipid fraction of the ready-to-eat fried loach were enhanced about 4% and 242%, respectively. However, eicosapntemacnioc and docosahexenoic acid were decreased about 9% and 16%, respectively. The carried out analyses also revealed that there were 28 volatiles detected in the ready-to-eat fried loach, among which were furan and pyrazine compounds formed during thermal processing. Aldehydes were observed to be the most abundant volatiles in the ready-to-eat fried loach(34.30%), followed by furans(18.91%) and ketones(14.06%). Textural analysis showed that the thermal processing applied on the loach resulted in increase of the hardness, springiness and chewiness of the ready-to-eat fried loach by 65%, 98% and 385%, respectively.(3) The possible changes of microbiological index and lipid oxidation of the ready-to-eat fried loach during storage periods were studied. The obtained results indicated that the coliforms were not detectable during the storage. After the storage of 90 days, the aerobic bacterial counts of the ready-to-eat fried loach stored at 20 °C were detected to be 1.5×104 CFU/g, while that of the ready-to-eat fried loach stored at 37 °C were about 2.2×105 CFU/g, the level beyond standard of the highest aerobic bacterial counts(3.0×104 CFU/g) recommended by food agency. During storage at 20 °C, lipid oxidation was found in the ready-to-eat fried loach. Addition of tea polyphenol and propylgallate in the loach had lower lipid oxidation. The fried loach stored at 20 °C had lower lipid oxidation than that stored at 37 °C. These results indicated that shelf life of the ready-to-eat fried loach with addition of one of the antioxidants was larger than 90 days if the fried loach was stored at 20 °C.