Comparative Study On Sensory Evaluation And Nutritional Value Of Fish And Crab Steamed By Different Methods And Preliminary Exploration Of The Reasons

Different cooking methods show different effects on the nutritional value of food ingredients.Steaming is a relatively healthy cooking method among them.However,there was no literature focused on different effects on food ingredients caused by different steaming methods.Patagonian toothfish and Taihu crab are popular dishes in central kitchen,and a proper cooking method can preserve the taste and nutritional value to the most extent.Nevertheless,the sensory acceptability of cooked food was not considered in the evaluation of nutritional value in previous studies.Therefore,this study was designed to investigate effects on sensory evaluation and nutritional value of Patagonian toothfish and Taihu crab steamed by different methods.The main results of this study were listed as follows:First of all,combined with sensory evaluation,the weight loss rates and water loss rates of Patagonian toothfish and Taihu crab steamed by different methods(gas heated steamer and electric steamer)were studied to determinate the optimal steaming periods.The optimal steaming periods of Patagonian toothfish steamed by electric steamer(11 min)and gas heated steamer(9 min)were determined,which of Taihu crab were 25 min and 20 min respectively.Furthermore,the nutritional values of cooked Patagonian toothfishes and Taihu crabs steamed by two different methods were studied under the best sensory condition.The contents of crude protein and fat in the fish fillets steamed by electric steamer were significantly higher than those steamed by gas heated steamer(P<0.05).No significant differences were observed in the total amino acids or essential amino acids among the samples steamed by different methods(P<0.05).However,the content of glutamic acid in the samples steamed by electric steamer was significantly higher than other groups(P<0.05),which contributed to its better flavor.The steaming methods only marginally affected the fatty acid profiles of the Patagonian toothfish.Among the essential fatty acids,no significant differences were observed in the relative percentage of eicosapentaenoic acid(EPA)among the samples steamed by different methods(P<0.05).The relative percentage of docosahexenoic acid(DHA)was the highest in the samples steamed by gas heated steamer(2.0 L of water volume),followed with those steamed by electric steamer and gas heated stemer(0.7 L of water volume).Under the optimal sensory condition,Taihu crabs steamed by electric steamer showed significantly better characteristics compared with those steamed by gas heated steamer,such as basic nutrition contents,vitamin contents,the contents of total,essential and delicious amino acids,the relative percentage of monounsaturated fatty acids(MUFAs)(P<0.05).And the contents of DHA and astaxanthin in samples steamed by electric steamer were 2-folds more than those steamed by gas heated steamer.Therefore,under the premise of the best sensory evaluation,Patagonian toothfish fillets and Taihu crabs steamed by electric steamer contained more nutrition compared with those steamed by gas heated steamer.Then,texture characteristics of Patagonian toothfish fillets were estimated,and the correlations between basic nutritional components and texture characteristics were analyzed.The results revealed that there were obvious correlations between the moisture,protein,fat content of Patagonian toothfish fillets and hardness,cohesiveness,chewiness(??0.05).What's more,an extremely significant correlation between the protein content and chewiness was observed(??0.01),with ? value of 0.009.Finally,the low field nuclear magnetic resonance(LF-NMR)technology was used to monitor and analyze the status and content of water in the muscle of Patagonian toothfish during the process of steaming.Besides,the causes that resulted in the differences on nutritional value between different steaming methods were also analyzed.The results showed that the T2 relaxation time and the proportion of water status of the Patagonian toothfish fillets were significantly correlated with the moisture of muscle(P<0.01).Furthermore,the content of immobilized water in the samples steamed by gas heated steamer was less than those steamed by electric steamer.And owing to the higher liquidity of immobilized water,more nutrients lost with this part of water in Patagonian toothfish fillets steamed by gas heated steamer.