Growth Characteristics and Toxigenicity of Aeromonas Hydrophila Isolated from Seafood

Abstract

The changes in protein of mantle muscle of dried squid(Illex argentinus)occurredduring rehydration were studied by analyzing the extracted protein fractions,collagen content,and the SDS-polyacrylamide gel electrophoretic pattern.The structural alternation wasalso studied by using a scanning electron microscopy.The ratio of content of nonproteinnitrogen to total crude nitrogen(total-N)in dried muscle was 27.6% and was mostly leached from muscle during rehydration.Lots of muscle protein were aggregated and denaturedthrough the process of drying.After the rehydration simply by water soaking,the percentdistribution of sarcoplasmic protein nitrogen(Sp-N)and myofibrillar protein nitrogen(MfN)in total-N of muscle was 7.8 and 9.1% respectively,which was quite lower than thosein the fresh muscle(16.8 and 59.0%,respectively).Alkali soluble nitrogen(Alk-N)in freshmuscle was 1.6% and increased to 72.5% in water-rehydrated muscle.Alkali rehydrationincreased the moisture content of muscle and the ratios of Sp-N and Alk-N while decreasedthat of Mf-N.The content of hydroxyproline(Hyp),as an indication of collagen,decreasedwith the increasing moisture content of rehydrated squid muscle.The Hyp content showedhigh correlation to the firmness of rehydrated muscles in raw state(r=0.8761).There weredegradations of myosin heavy chain and paramyosin of muscle protein during rehydrationand the increases of protein components whose molecular weight were lower than 50,000daltons.After the rchydration,the crowded muscle fibers of dried squid became looser withthe larger interstitial space due to the increase of extrafiber fluid.When alkali solution wasused for rehydration,some fibers of muscle became swollen.測定復水魷魚乾胴肉中蛋白質組成分之抽出率，膠原蛋白質含量，並以SDS-PAGE電泳分析肌肉蛋白質之變化，並以掃瞄式電子顯微鏡觀察肌肉組織之變化。魷魚素乾品胴肉之粗蛋白質中含有27.6％非蛋白態氮化合物，大多於復水過程中流失，魷魚在乾製過程中，大量蛋白質凝集變性，與鮮肉比較，經水復水後其總氮含量中，肌漿蛋白質氮(Sp-N)及肌原纖維蛋白質氮(Mf-N)之含量分別由16.8％及59.0％降低至9.1％及7.8％，而鹼可溶性氮含量(Alk-N)則由1.6％增至72.5％。使用鹼液復水有助於肌肉之吸水膨潤，可提高Sp-N之抽出量，但Mf-N隨鹼復水程度之增加而略減，Alk-N則相對增加。膠原蛋白質之含量（以羥脯胺酸表示，Hyp），隨鹼復水程度之增加而略爲減少，Hyp之含量與生肉的肉質硬度呈高度相關性（r=0.8761）。肌肉全蛋白質之SDS-PAGE電泳圖型顯示肌凝蛋白重鏈及副肌凝蛋白含量，隨著鹼復水程度之增加而減少，有部分斷裂現象，且分子量小於5萬之蛋白質成分稍有增加。以電子顯微鏡觀察鹼復水魷魚胴肉組織，相鄰肌纖維之間隙因吸水而加大，部分肌纖維亦有膨大的現象。