Abstract
This study aims at preparing the Maillard reaction products of protein hydrolysate from grass carp (Ctenopharyngodon idella) bone and identifying its characteristic flavour compounds. Meanwhile, bioactivities and amino acids composition of hydrolysates and its Maillard reaction products were compared with the thermal degradation reaction as one positive control. Single factor experiment was applied to optimize the enzymolysis parameters of grass carp bone protein using flavourzyme, under which the highest degree of hydrolysis (40.1%) was obtained. According to the response surface methodology, the top predicted value (70.45%) of degree of graft of Maillard reaction was obtained with initial pH of 7.07, temperature of 118.33°C, and time of 1.75 h. Moreover, the results of Maillard reaction products illustrated a significant increase in DPPH radical scavenging activity (p<0.05) compared to that of hydrolysate and its thermal degradation products, which was accompanied by the decreased ACE inhibitory activity. Besides, the umami-sweet taste amino acid ratio in free amino acids of Maillard reaction products climbed considerably compared to those of hydrolysate and its thermal degradation products, which proved that Maillard reaction is an effective way to improve the flavour taste of protein hydrolysate. The GC-MS results showed that 37, 40, and 62 kinds of volatile compounds were detected in hydrolysate, thermal degradation products, and Maillard reaction products, respectively. The Maillard reaction products contained more flavour volatile compounds of aldehydes, alcohol, ketone, pyrazine, and other compounds that contribute to pleasant aromas. These results suggested that the grass carp bone protein hydrolysate after Maillard reaction could potentially have a wide range of applications as antioxidant and flavour substances.
Highlights
As a traditional freshwater fish, grass carp (Ctenopharyngodon idellus) is one of the major freshwater-cultured fishes [1]
E statistical significance of equation (5) was checked by F-test, and the results of analysis of variance indicated that the F-value of 70.68 (p < 0.0001) implied that the model was statistically highly significant. e F-value and p value of the lack of fit were 1.01 and 0.4763, respectively. is illustrated that the lack of fit was not significant, which confirmed the goodness of fit and suitability of the regression model for predicting the degree of graft (DG) of Maillard reaction of grass carp bone protein hydrolysates (GCBPH) under any combination of values of the independent variables. e coefficient of multiple determinations (R2 of 0.9891) revealed that 98.91% of the variation in the DG was due to the independent variables and only 1.09% of the total variation was not explained by the model
Parity plot (Figure 2) showed an acceptable level of agreement. e strong correlation between the actual and the predicted results confirmed that the response model was accurate to reflect the expected optimization. All these results confirmed the predictability of the model for DG of Maillard reaction of GCBPH
Summary
As a traditional freshwater fish, grass carp (Ctenopharyngodon idellus) is one of the major freshwater-cultured fishes [1]. Erefore, it is of great urgency to develop value-added products from grass carp bone. Journal of Food Quality the grass carp proteins were mainly used to prepare bioactive peptide and functional material in secondary processing [5, 6]. The research of Li et al [7] revealed that the grass carp protein hydrolysate displayed high antioxidant activities. Fish protein hydrolysate was proved to be of use for flavour enhancer for direct human consumption for the material composition of free amino acids, smaller peptides, salt, and many savory compounds [9]. The study of protein hydrolysate from grass carp bone on food flavour agents has not been fully investigated
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