Abstract: This study aimed to elucidate the mechanism for the preparation of meat flavorings by thermal reaction of hydrolyzed animal protein (HAP). Four thermal reaction systems, HAP alone, HAP plus oxidized lard (HAP-OL), HAP plus xylose (HAP-Xyl) and HAP plus both oxidized lard plus xylose (HAP-Xyl-OL), were reacted at 120, 130 or 140 ℃ for 120 min. The effect of adding oxidized lard and xylose on the pH, browning degree, molecular mass distribution and taste of reaction products was investigated. The results showed that the pH decline, absorbance at 294 and 420 nm, and chroma of the reaction products from HAP-Xyl were much higher than those of HAP-OL, and the?values?of?these parameters?were?highest?in the reaction products of HAP-Xyl-OL. The changes in absorbance at 420 nm and chroma at the early stage of reaction followed zero-order kinetics for all four reaction systems. The reaction rate constant and activation energy showed that HAP-Xyl reacted fastest and HAP-Xyl-OL reacted more slowly than HAP-Xyl, suggesting that the presence of OL inhibited the reaction of xylose with HAP. The molecular mass distribution of the reaction products with better taste was determined by high-performance gel chromatography (HPGC). It was shown that the addition of xylose decreased the fractions with molecular mass < 1 kDa, while oxidized lard had little effect on the molecular mass distribution. Furthermore, sensory evaluation showed that the addition of xylose enhanced the umami and meaty taste, the addition of oxidized lard increased the kokumi, continuity and mouthfulness, and the addition of both oxidized lard and xylose increased the umami, meaty taste, kokumi, continuity and mouthfulness.

Key words: Maillard reaction, taste, xylose, oxidized lard, kinetics, enzymatic hydrolysate of pork