Study On Fermentation Technology And Textural Properties And Flavor Components Of Goat Yoghurt

Goat milk is a kind of unique dairy resource, rich in nutrition, containing more than 200 kinds of nutrients and bioactive substances.It has become more and more attention by people. But its flavor has been the bottleneck of consumer acceptance of goat milk products. Goat yogurt is an active lactobacillus product making from biological fermentation ,on goat milk as raw materials. It has a variety of nutrition health care effects, and the flavor can be significantly improved by lactobacillus fermentation, beneficial to actively promote goat milk market development.This paper optimized the fermentation process conditions of goat yogurt. And its textural properties and flavor components were studied by texture techonology, near infrared spectroscopy and GC-MS. The main research contents and results are as follows:1 The influences of different lactobacillus on the sensory and texture properties of goat yoghurt was investigated and compared, and finally compound culture (Bifidobacterium and Streptococcus thermophilus ) was selected as the starter of goat yogurt, with good flavor quality and texture quality.2 The comprehensive texture property of goat yogurt increased as the sugar amounts added, best at 10%; first increased and then decreased with inoculation numbers added; best at 3%; first decreased and then increased with fermentation temperature increased, worst at 36℃; first increased and then decreased with strain proportions increased; best at 2:1.3 The fermentation process conditions of goat yogurt was optimized, the optimal parameters were as follows: fermentation temperature was 38℃, inoculation numbers was 4%, sugar amounts was 8%, the proportion of Bifidobacterium and Streptococcus thermophilus was 2:1.The goat yogurt has smooth structure, good taste, excellent flavor, and almost without mutton flavor.4 The flavor components of goat yogurt were analyzed by GC-MS-SPME, 8 kinds of volatile flavor components were identified in goat yoghurt, including alkanes, ketones, aldehydes, alcohols, acids, esters, sulphides and aromatic compounds.The mainly components were 2,3-Butanedione, 2,3-Pentanedione, 3 - hydroxyl - 2-Butanone, Benzaldehyde, Acetic aci and Butanoic acid, Isopentyl phenylacetate,1,2,3,5-tetramethyl-Benzene, 1-ethyl-2, 4-dimethyl- Benzene, 1-methyl-2-(1-methylethyl)- Benzene,et al. These components make up the subject flavor of goat yoghurt.5 We first attempted to establish the quantitative calibration moldls of the hardness, cohesiveness and water holding capacity of goat yogurt. The analysis showed that R~2 of the firmness, cohesiveness and water holding capacity were 0.6668, 0.6461and 0.7269, respectively,and their correlation coefficients of external-validation were 0.7577, 0.7200 and 0.7174, respectively. The external-validation results were all not significant different from actual measurements (P > 0105). The results showed: textural properties of goat yoghurt were predictioned by NIRS ,which had certain feasibility, providing a new direction for the research of online monitoring technology of goat yogurt quality in the process.