Effect of addition of different dairy ingredients on the quality of yogurt

Research Hypothesis: Yogurt flavor depends on both starter cultures and dairy base composition. Different ingredients alter flavor precursors (amino acids, fatty acids), directing microbial metabolism to produce distinct key flavor compounds and sensory profiles. Data & Methods: Flavor differences were characterized using sensory evaluation, E-nose, GC×GC-O-MS (for OAVs and concentrations of 19 key odorants), and HPLC (for amino and organic acids). Correlation analyses linked chemical and sensory data. Key Findings: Whey protein (WP) yogurt performed best, with the highest levels of key volatiles (e.g., acetoin, diacetyl), organic acids, and sweet amino acids (alanine, lysine), resulting in superior creamy/fresh aroma and balanced taste. Core flavor drivers were acetoin (OAV=76), acetic acid (OAV=181), diacetyl (OAV=30), and 2-nonanone (OAV=52). Milky aroma correlated with acetoin, fresh with styrene, and fishy odor with hexanoic/butyric acids. Interpretation & Application: High OAV compounds drive sensory perception. For optimal flavor, use whey protein. To correct fishy off-notes, trace and reduce precursors like caproic/butyric acid by adjusting ingredients or process.研究假设：酸奶的风味同时受发酵剂菌株（starter cultures）与乳基配方组成的共同影响。不同配料会改变风味前体物质（氨基酸、脂肪酸），进而调控微生物代谢，生成具有显著差异的关键风味物质与感官特征。 数据与方法：本研究通过感官评价（sensory evaluation）、电子鼻（E-nose）、全二维气相色谱-嗅闻-质谱联用（GC×GC-O-MS，用于测定19种关键风味物质的气味活性值（OAV）与浓度）以及高效液相色谱（HPLC，用于测定氨基酸与有机酸含量）对风味差异进行表征，并通过相关性分析关联化学检测数据与感官评价数据。 关键研究结果：乳清蛋白（whey protein, WP）酸奶表现最优，其关键挥发性物质（如乙偶姻（acetoin）、双乙酰（diacetyl））、有机酸以及甜味氨基酸（丙氨酸（alanine）、赖氨酸（lysine））的含量均为最高，最终呈现出更优异的乳脂/清新香气与均衡的口感。核心风味贡献物质为乙偶姻（OAV=76）、乙酸（OAV=181）、双乙酰（OAV=30）以及2-壬酮（OAV=52）。乳香气息与乙偶姻呈显著相关，清新香气与苯乙烯（styrene）相关，而鱼腥味则与己酸、丁酸呈显著相关。 解读与应用：高气味活性值的化合物对感官感知起到决定性作用。若要获得最优风味，应选用乳清蛋白作为配料。若需要矫正鱼腥味杂味，可通过调整配料或工艺，追踪并减少己酸、丁酸这类风味前体物质的含量。