为探明酸奶发酵和冷藏过程中的品质特性及主要风味成分变化情况,测定了酸奶在发酵和冷藏过程中的pH值、酸度、持水力、黏度等理化指标以及乳酸菌活菌数和氨基酸、脂肪酸等风味成分含量。结果表明,酸奶持水力和黏度变化趋势相同,在发酵和冷藏前期逐渐增加,后期平缓下降;发酵阶段酸度显著升高,而pH值显著下降,且均有显著性差异(P<0.05),冷藏阶段均变化不显著;乳酸菌数量、氨基酸总量、必需氨基酸和非必需氨基酸以及鲜味氨基酸含量在发酵和冷藏阶段呈现逐渐增加—迅速降低—缓慢上升的趋势;脂肪酸含量在发酵和冷藏期间持续上升,其中多不饱和脂肪酸在发酵和冷藏阶段逐渐降低,而短链脂肪酸、中链脂肪酸及长链脂肪酸逐渐增加,均无显著性变化。该研究为酸奶及发酵乳制品的研发和品质评价提供一定的理论基础。
The qualitative characteristics and changes in the main flavor components of yogurt were analyzed during fermentation and storage. The physicochemical indexes (e.g. pH, acidity, water holding capacity and viscosity), the number of active lactic acid bacteria and the content of flavor components (e.g. amino acids and fatty acids) were determined. The results showed that both water holding capacity and viscosity of yogurt gradually increased at early stage of fermentation and cold storage, and then slowly decreased after this stage. The acidity of yogurt increased and the pH decreased significantly (P<0.05) during the fermentation process, and there were no significant changes during cold storage. During fermentation and storage, the number of lactic acid bacteria, total amino acids, essential and non-essential amino acids, as well as contents of umami amino acids gradually increased and subsequently decreased and then slowly increased. Furthermore, the content of fatty acids continually increased during fermentation and cold storage, polyunsaturated fatty acids gradually decreased, while short-, medium-and long-chain fatty acids gradually increased but all with no significant changes. This study provides a theoretical basis for developing and evaluating the quality of yogurt and other fermented dairy products.
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