Preparation Of Thermal-Reaction Type Shrimp Flavors

The objective of this paper was to prepare shrimp flavors true to nature using the shrimp offal as raw material through biologic enzyme hydrolysis and thermal reactions (it should be Mallard Reaction in theory).Firstly, the shrimp offal was hydrolyzed by proteinase. According to the shrimp protein hydrolysing ability(expressed as Degree of Hydrolysis, DH), five different kinds of proteinase (Flavourzyme, Protamex, Neutrase, Alcalase and Papain) were studied. Their appropriate amount and time were obtained as follows respectively: 4.5LAPU/g﹒protein, 300min; 0.0135×104u/g﹒protein, 300 min; 14.4AU/g﹒protein, 180 min; 3480DU/g﹒protein, 240 min and 0.054×104u /g﹒protein, 300 min. Also, the hydrolyzing ability of mixed enzymes were studied according to the reaction of single enzyme. The results showed that the mixture of Flavourzyme and Alcalase was the most effective combination. The mixture of Flavourzyme and Alcalase on hydrolysis of the shrimp offal were then studied further through response surface methodology (RSM). The optimum hydrolysis parameters were figured out as follows: initial pH 6.74, temperature 48.3℃, substrate (shrimp protein) concentration 7.3%. Thrice repeat experiments were conducted under this condition and the degree of hydrolysis could reach 23.16%.Secondly, thermal reactions to prepare shrimp flavors were studied. Through sensory evaluations on the reaction products, the basic reaction materials were determined as follows: arginine and alanine were added to the shrimp offal hydrolyte which were hydrolyzed for 5 hours, initial pH, temperature and reacting time were the most important factors affecting the quality of the products. By monofactorial and orthogonal experiments, the optimum parameters of thermal reaction were gained as follows: initial pH 7.0, temperature 100℃, reaction time 30min .Lastly, the formula of thermal reaction can be adjusted in order to prepare more realistic products: adding a mixture of monosaccharide (xylose and glucose and the ratio of them was 1:4); adjusting the ratio of arginine and alanine to2:1 and adding 1.0% thiamin, 0.6% ascorbic acid and 0.4% taurine according to the mass of hydrolysate.Finally, volatile components in the shrimp flavours were analyzed. Volatile components were extracted by Simultaneous Distillation and Extraction(SDE) method and Solid Phase Microextraction (SPME) method separately. The extracts were isolated and identified by gas chromatograph-mass spectrometry (GC-MS). Ninety-one compounds were.gained totally. The percentage of pyrazines which were reported to contribute to shrimp aroma greatly was 12.47% (SPME)and 12.68%(SDE), and the percentage of sulfur-containing compounds was...