| The Maillard reaction (MR) is a kind of naturally occurring non-enzymatic browning related to reaction between the sugar and protein, amino acids or peptides in food material during the thermal processing and storage, and it is the most complex reaction in food chemistry. Numerous studies have shown that Maillard reaction products (MRPs) are considered as natural products possessing antioxidative activity, which are formed and accumulated during food processing and storage. The factors, such as pH, water activity, heating time and temperature, type and proportion of material and other factors affect the mechanism, pathway, product types MR, etc. Tilapia skin has been clearly proven to be a good source to produce gelatin, which then produce a large amount of free amino group after hydrolysis. The free amino group can be involved in Maillard reaction as reactant. The Maillard reaction systems and products from tilapia skin gelatin peptides (TSGP)-glucose with different pH, glucose concentration and hydrolytic degree were prepared, and the systems were characterized by grafting degree, ultraviolet-visible (UV-Vis) spectroscopy and fluorescence assays, as well as the antioxidative activity of MRPs, so as to provide theoretical guidance for high-value utilization of tilapia skin.The gelatin was obtained from tilapia skin by hot water extraction, and the resulting preotein was typical gelatin based on the UV spectroscopy scanning. The composition and content of amino acids in gelatin were analyzed, the results indicated that tilapia skin gelatin contains seven kinds of essential amino acids (Lys, Val, Leu, Ile, Phe, Met, Thr) and ten kinds of non-essential amino acids. The content of essential amino acids accounted for16.94%of total amino acids content.The tilapia skin gelatin peptides (TSGP) with different hydrolytic degree were prepared by papain, trypsin and alkali protease, the degree of hydrolysis were6.2%,8.0%and14.3%, respectively.The Maillard reaction process were investigated with TSGP and glucose as raw materials. The Maillard reaction systems from TSGP-glucose with different pH, glucose concentrations and hydrolytic degree were prepared, and the systems were characterized by UV-Vis spectroscopy and fluorescence assays, and the change in grafting degree and pH were also evaluated. The results indicated that, compared to the neutral and acid condition, alkaline condition was in favor of Maillard reaction. In addition, the higher the glucose concentration or hydrolytic degree, the faster the reaction rate, showing the high grafting degree, UV-Vis absorbance value and fluorescence intensity. The total content of free amino acid reduced after Maillard reaction, the ratio of essential amino acid and non-essential amino acid of MRPs is higher than that of native TSGP.The antioxidant properties of MRPs from TSGP-glucose with different pH, glucose concentrations and hydrolytic degree. The results showed that, MRPs from TSGP-glucose demonstrated the DPPH and ABTS radical scavenging activities, as well as reducing power. The antioxidative effects increased as the heating prolonged. MRPs from alkaline media showed much higher antioxidant effects than that from neutral and acid condition. And the higher the glucose concentration, the stronger the antioxidavitve activity of MRPs, as well as the hydrolytic degree of TSGP, the MRPs from system from TSGP with higher hydrolytic degree showed the stronger antioxidant activity. |
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