Study On Preparation And Antioxidant Activity Of Meat-like Flavor By Maillard Reaction From Alaska Pollock Frame

Maillard reaction is one of the important formation ways of meat flavor. The utilization of reaction between reducing sugar, amino acids, and peptides in animal protein hydrolysate to prepare meaty flavor not only comprehensively use the by-product (pollock fillet) to improve its economic value, but also provide theoretical basis for preparing natural, antioxidative meaty flavor. The major studies are as follows.Firstly, protein hydrolyte was prepared from Alaska pollock frame using Protamex and Flavorzyme. Taken the degree of hydrolysis (DH) as an index, the effect of different reaction conditions on pollock frame was studied. Based on single factor experiments, the optimum processing condition was obtained by using Box-Behnken center-united design and surface response analysis. The result showed that the optimum hydrolytic condition was initial pH 7.0, temperature 47℃, solid-liquid ratio 1:2, enzyme dosage 3.0%, compound enzyme ratio 1:1, hydrolysis time 3 h, and the DH of pollock frame was 38.74%. Moreover, further study on Maillard reaction showed that, after 9 hours of continuous hydrolysis, the growth of DH and contents of free amino acids (FAAs) was essentially flat, and there was no significant difference in the flavor evaluation of Maillard reaction products. Ultimately,9 h was confirmed as the optimal hydrolysis time. The enzymatic hydrolysate obtained under the optimum condition could provide a good source of high quality protein for producing different meat flavor through Maillard reaction.Secondly, the processing technology of beef-like flavor and chicken-like flavor by Maillard reaction using pollock frame hydrolysate was investigated. Based on single factor experiments, the orthogonal experiment was applied to obtain the optimal conditions. The result showed that, beef-like flavor is pure and aromatic under the conditions of 3.0 g/100 mL glucose,1.0 g/100 mL xylose,1.25 g/100 mL thiamine,1.5 g/100 mL L-cysteine hydrochloride,30 mL/100 mL beef hydrolysate, pH 5.0, temperature 120℃ and reacting time 120 min. While chichen-like flavor is also pure and aromatic under the conditions of 3.0 g/100 mL glucose,1.0 g/100 mL xylose,0.75 g/100 mL thiamine,1.0 g/100 mL L-cysteine hydrochloride,40 mL/100 mL beef hydrolysate, pH 5.0, temperature 90℃ and reacting time 90 min.Thirdly, the contents of free amino acid and volatile components before and after Maillard reaction were analyzed. Results showed that the loss ratio of threonine went up to 63.02% after Maillard reaction in beef-like flavor productions, which suggested threonine may be the key amino acid involved in the Maillard reaction; While the loss ratio of arginine went up to 35.02% after Maillard reaction in chicken-like flavor productions, which suggested arginine may be the key amino acid involved in the Maillard reaction. A total of 76 compounds were identified in beef-like flavor productions, including sulphur compounds (3), alcohols (12), aldehydes (22), ketones (7), esters (4), ethers (1), hydrocarbons (24) and acids (3). Among them, methanthiol, 2-methyl-3-furanthiol,3-methional, hexanal, octanal, benzeneacetaldehyde, (E,E)-2,4-nonadienal, and trans-(E,E)-2,4-decadienal were identified as the key aroma compounds of the beef-like flavor. A total of 70 compounds were identified in chicken-like flavor productions, including nitrogen compounds (1), sulphur compounds (3), chloric compounds (1), alcohols (12), aldehydes (13), ketones (7), esters (1), ethers (1), hydrocarbons (27) and acids (4). Among them,2-methyl-3-furanthiol,3-methional, octanal, nonanal and 2,4-decadienal were identified as the key aroma compounds of the chicken-like flavor.Lastly, the antioxidant activities in vitro of Maillard reaction products (MRPs) were studied. The results showed that constant generation of organic acids declined the pH of MRPs with the prolongation of heating time. As the reaction proceeded, more and more uncoloured intermediates, fluorescent substances and melanoidin were produced, whose absorbance values at 294 nm,420 nm and fluorescence intensity kept increasing. After Maillard reaction, the products of two type flavor had better scavenging activity against DPPH-, hydroxyl free radical and hydrogen peroxide than that before reaction and reducing power is also higher. The scavenging activity against DPPH-and reducing power was increased with the prolongation of heating time, while the scavenging activity against OH and H2O2 was increased at the beginning, and then declined. It is likely that the components with the ability of scavenging activity against ·OH and H2O2 were decomposed as intermediates in the Maillard reaction. The antioxidant activity of beef-like flavor was higher than that of chicken-like flavor, which might be due to the different reaction conditions of preparation process and the difference of MRPs.