Castada Hardy Z, Polentz Victoria, Barringer Sheryl, Wick Macdonald
Department of Food Science and Technology, The Ohio State University, Columbus, OH, 43210, USA.
Department of Animal Sciences, The Ohio State University, Columbus, OH, 43210, USA.
Rapid Commun Mass Spectrom. 2017 Dec 30;31(24):2135-2145. doi: 10.1002/rcm.8007.
4-Alkyl branched-chain fatty acids and 3-methylindole are characteristic flavor compounds associated with sheep meat. Determining their partitioning behavior between the gas and condensed phase and ultimately developing a correlation between the compound's headspace concentration and sensory descriptive grouping are important for high-throughput characterization and grading classification.
The headspace concentrations of 3-methylindole, 4-methyloctanoic acid, 4-ethyl-octanoic acid, and 4-methylnonanoic acid above corn-oil-based standard solutions and lamb fat samples were measured using selected ion flow tube-mass spectrometry (SIFT-MS). The standard solutions were equilibrated at 80, 100, 110 and 125°C while the fat samples were equilibrated at 125°C. Statistical evaluation, linear and polynomial regression analyses were performed to establish the compound-specific and temperature-dependent Henry's Law constants, enthalpy (ΔH) and entropy (ΔS) of phase changes.
The Henry's Law constants (k ) were calculated from the regression analysis with a high degree of confidence (p < 0.05) and linearity (r > 0.99). The k increased with increase in equilibrium temperature. The empirical calculation of ΔH and ΔS at different temperatures confirmed the temperature-dependence of the Henry's Law constants. The headspace concentrations of the lamb-flavor compounds were determined above actual lamb fat samples and the corresponding condensed-phase concentrations were successfully derived.
The temperature-dependent Henry's Law constants, ΔH, and ΔS of phase changes for 3-methylindole, 4-methyloctanoic acid, 4-ethyloctanoic acid, and 4-methylnonanoic acid in an air-oil matrix were empirically derived. The effectiveness of SIFT-MS for the direct, real-time, and rapid determination of key flavor compounds in lamb fat samples was established.
4-烷基支链脂肪酸和3-甲基吲哚是与羊肉相关的特征风味化合物。确定它们在气相和凝聚相之间的分配行为，并最终建立化合物顶空浓度与感官描述分组之间的相关性，对于高通量表征和分级分类很重要。
使用选择离子流管质谱法（SIFT-MS）测量玉米油基标准溶液和羊肉脂肪样品上方3-甲基吲哚、4-甲基辛酸、4-乙基辛酸和4-甲基壬酸的顶空浓度。标准溶液在80、100、110和125°C下平衡，而脂肪样品在125°C下平衡。进行统计评估、线性和多项式回归分析，以确定化合物特异性和温度依赖性的亨利定律常数、相变的焓（ΔH）和熵（ΔS）。
通过回归分析计算出亨利定律常数（k），具有高度置信度（p < 0.05）和线性（r > 0.99）。k随平衡温度的升高而增加。不同温度下ΔH和ΔS的经验计算证实了亨利定律常数的温度依赖性。测定了实际羊肉脂肪样品上方羊肉风味化合物的顶空浓度，并成功推导了相应的凝聚相浓度。
通过经验推导得出了空气-油基质中3-甲基吲哚、4-甲基辛酸、4-乙基辛酸和4-甲基壬酸的温度依赖性亨利定律常数、ΔH和相变熵。确立了SIFT-MS用于直接、实时和快速测定羊肉脂肪样品中关键风味化合物的有效性。
