Integrated Study On The Characters Of Fish Meat

The selected fishes,such as Pseudosciaena crocea(Richardson),Epinephelus awoara(Temminck et Schlegel),Paralichthys olivaceus(Temminck et Schlegel), Siniperca chuatsi(Basilewsky),Oreochromis nilotica(Linnaeus) and Chilocsyllium plagiosum(Bennett),used in the present study were the important economical aquatic products reared in Fujian.The major nutrition components and physical-chemical characteristic in these tested fish muscles were determined in the present research;the contents of Inosine monophosphate(IMP) and fatty acid in fish muscles were also investigated.It might,based on this study,preliminarily establish the foundation for evaluating the fish muscle character,instead of some impersonality indexes,and would deeply promote the investigation and supplement for the fish dietetics research, and also will impel an important effect on the practices in fish breeding,production, genetic improving,seed selection,especially in improving muscle characters.The main results are as follows:1.The crude proteins of the tested fishes P.crocea,E.awoara,S.chuatsi,P. olivaceus,O.nilotica and C.plagiosum were 17%-18%of the total components,and the crude lipid 3%-4%,their moisture content reached 78%-82%,and only 0.5%-0.8%ash.It seemed that they would be fresh and delicious taste referring to landing animals.C.plagiosum appeared quite high contents of crude protein(23.1%), moisture(81.5%),and ash(1.1%),but low crude lipid(0.27%).The compositions of amino acid were similar for all the tested fishes,that of E.awoara kept highest of the total content of amino acids(83.27%) and essential amino acid index(EAAI,45.29)., C.plagiosum(75.68%,41.03) and S.chuatsi(75.82%,40.59) was lower.For all samples,the amino acid score(AAS) of(Met+Cys) and Val were lowest,the fist limited amino acid were(Met+Cys),the second was Val.Other AAS were close to 1 or even higher;also,AAS of Lys was the high. Comparing with Min-Yue stock,P.crocea of Dai-Qu stock held higher content of crude protein(17.6%-18%) and moisture(75.7%-78%),but the content of ash (0.4%-0.9%) is lower,they also showed superiority with higher indexes on total content of amino acids and EAAI.In seven samples of Min-Yue stock,P.crocea cultured in offshore cages(diameter 12m) in Nanji Island possessed the maximum crude protein content(17.4%) but fewer crude fat(2.96%) and ash content(1.0%) comparatively,appearing much better than the other samples.Therefore,their nutritive proportions trended toward balance,and the fresh tendemess,flavor and taste seemed better than those in others.2.By comparing and analysing the physical-chemical characteristics in P. crocea,P.olivaceus,E.awoara and O.nilotica,the initial pH value of O.nilotica was 6.54,higher than other 3 kinds of fish.However,the nutrition value of O.nilotica was tailender during storage,because of heavy change,droped to pH 6.27 in 24 hours and decreasing nutrition elements.E.awoara exhibited similarity with P.olivaceus on physical-chemical characters.P.crocea had the highest water holding capacity (39.40%),the lowest storage loss(1.41%),and the fastest cooked meat percentage (81.39%) among 4 kinds of fish;and also pH(6.45) was higher than E.awoara and P. olivaceus.Regarding to the characters of pH and water holding capacity in tested fish muscles,that of Min-Yue stock P.crocea seemed to be well than what in Dai-Qu one, not only for its higher initial pH,but also with slow fall on pH,few water loss and better water holding capacity while storage.The freeze drying method were designed and originated in determining water holding capacity,moisture in musculatures,sublimed from liquid without calefaction by using vacuum freeze drying machine.This designed method could be easily operated and good for the stability and repeatability of test data.The moisture loss was higher than ones from other test ways.3.IMP contents of six fishes,C.plagiosum,P.crocea,S.chuatsi,E.awoara,P. olivaceus and Bostrichthys sinensis,were tested by HPLC.The results showed:IMP contents of the musculatures varied with the different fish species,the IMP quantity (4.214 mg/g) in fresh sample of P.olivaceus was higher than those in others (2.365～3.634 mg/g).IMP contents of six fish meats frozen in -70℃were all higher than those of fresh ones in cold-storage for 10 days.IMP of frozen samples in P. crocea reached tiptop after 24hr cold storage,of which S.chuatsi still got up by the end of the test,while those of the other fishes got the highest at the 5th day.The result indicated,IMP contents of fish meat reduced in longtime cold-storage and resulted in fresh low down.But the IMP contents obviously increased and the fresh and edibility seemed improved in cold-storage in the first week.4.As for the sorts and contents of fatty acid in the above tested fish muscles; contents of the unsaturated fatty acids were all higher than those of the saturated ones. The results showed that unsaturated contents in different samples varied slightly,and so did the saturated ones.For the contents of EPA and DHA in samples of P.crocea,P.olivaceus,E. awoara and O.nilotica,the highest one was found in P.olivaceus,accounted for 28.4%,followed by E.awoara,C.plagiosum and P.crocea,with 19.1%,15.7%and 14.9%respectively;the lowest was 2.1%tested in O.nilotica.EPA and DHA of P.crocea in Dai-Qu stock occupied 16.9%of the total fatty acid contents,lightly higher than that in Min-Ye stock(15.2%),the lowest value 9.0% was the sample collected from Fuzhou fish market.5.With synthesized the indexes of nutrition components,physical-chemical characteristic,contents of IMP and fatty acid,it is proposed to estimate fish meat character according the following contents of protein,lipid,EAAI,water holding capacity,PH and EPA+DHA.