| Pufferfish is very popular among consumers because of its rich nutrition and delicious.The development and utilization of pufferfish are mainly focused on muscle,skin,liver and gonad,but little research has been done on the by-products of fish including head and bone.Therefore,fish head and bone as targetwhich are by-products of processing of Takifugu obscurus,were used in this sudy.The proteolytic hydrolysates of by-products were prepared by enzymatic hydrolysis technology.On this basis,the odor,taste and antioxidant activity of Maillard reaction products of enzymatic hydrolysates of different molecular weight peptide were studied,which provided new ideas and theoretical support for the development and utilization of taste-presenting base material of Takifugu obscurus.The main contents and results of this study were as follows:(1)On the basis of understanding the nutrient components of different parts of Takifugu obscurus,the optimum enzymatic preparation and hydrolysis conditions for the enzymatic hydrolysis of by-products of Takifugu obscurus were screened by single factor and response surface test,and the changes of free amino acids of by-products before and after enzymatic hydrolysis were analyzed and compared.The results showed that the bone with high protein content(43.00±0.70%)and low fat content(1.32±0.08%)could be used as a good protein substrate for protein hydrolysates.When the ratio of material to liquid was 1:4 and the time of enzymatic hydrolysis was 5 h,the optimum conditions of enzymatic hydrolysis of by-products of Takifugu obscurus were as follows: protamex was the best enzyme,the amount of protamex was 2.56%,the temperature of enzymatic hydrolysis was 47.70?,and the p H value is6.06.The hydrolysis degree of protease hydrolysate reached 48.62±0.67%,the umami score was 5.25±0.42,and the bitterness score was 2.34±0.39.These results which were basically consistent with the predicted results of response surface experiment.The total content of free amino acids after enzymatic hydrolysis(1733.19 ± 190.01 mg/100 g)was 6.5 times higher than untreated sample(267.49±7.59 mg/100 g).The contents of umami,sweet and bitter amino acids were 9.15,11.25 and 4.93 times higher than umtreated sample,respectively.(2)The changes in browning intensity,umami value,bitterness value,electronic tongue and electronic nose as indicators was used to assess the maillard reaction product(MRP).The enzymatic hydrolysates of >3k Da and 0.3-3k Da fractions were obtained by membrane separation technology.The effects of different molecular weight peptide fractions on the taste and odor of Maillard products were investigated.The results showed that xylose had higher Maillard reaction degree,and sensory evaluation combined with electronic tongue analysis showed higher umami value and lower bitterness value.The results showed that 0.3-3k Da had better taste activity after Maillard reaction and good enhancement effect on salty,sour and umami.The total free amino acid content was 193.68 mg/g,and the total proportion of umami and sweet amino acid was 35.53%.The total content of AMP+GMP+IMP was 18.62 mg/100 g,and EUC was 42.26 g MSG/100 g.The results of volatile odor analysis showed that 74 flavor components were identified in Maillard reaction products,among which aldehydes were dominant,followed by esters and heterocycles,benzaldehyde,phenylacetaldehyde,nonanal,decanal,4-propylbenzaldehyde,dimethyl phthalate,diisooctyl phthalate,1,2-phthalic acid,butyl 2-methylpropyl ester,2-isobutylpiperazine and furyl mercaptan.2,5-thiophene dimethylaldehyde plays an important role in the formation of characteristic flavor.The content of volatile compounds in MRPs of the whole peptide fraction was significantly higher other two samples,and the total content of aldehydes,esters and heterocyclic compounds contributed greatly to the overall flavor of the samples.(3)The antioxidant ability of maillard reaction products of different molecular weight peptide hydrolysates were investigated by reducing power,DPPH radical scavenging rate and ferrous ion chelating rate.When the sample concentration was 5 mg/m L,the antioxidant capacity of potassium ferricyanide and DPPH free radical scavenging rate of Maillard product of each molecular weight peptide after Maillard reaction increased at least two times,and the scavenging rate of DPPH radicals was increased by at least 50%,the chelating rate of ferrous ions increased by at least 10%,and the comprehensive antioxidant capacity of MRPs-PH was the strongest.In summary,the optimum preparation conditions of flavoring base material from by-products of Takifugu obscurus were determined,and the flavor and functional characteristics of the base material were studied from the aspects of taste,odor and antioxidant activity.These could provide some references for the development of nutritive functional puffer fish seasoning with rich peptides. |
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