Flavor properties of post-heated fermented milk revealed by a comprehensive analysis based on volatile and non-volatile metabolites and sensory evaluation
Xiaoxia Li, Zhi Hao Zhao, Shaoqi Shi, Dongdong Li, Yue Sang, Pengjie Wang, Liang Zhao, Wang Fuqing, Bing Fang, Shuxing Chen, Yixuan Li, Zhengqiang Jiang, Jie Luo, Xiaoxu Zhang, Ran Wang
Abstract
Existing research on the post-heating processing of fermented milk has primarily focused on single post-heating treatments and the texture, while research on how changes in metabolites during different post-heating treatments affect flavor and sensory properties is limited. This study investigates the changes in volatile metabolites in fermented milk treated at different post-heating temperatures to determine the characteristic aroma types and analyzes the changes in non-volatile metabolites associated with aroma-active compounds or their precursors to clarify the causes of the altered flavor and sensory properties. The results showed that in the 65 °C and 75 °C treatments, 63 volatile compounds were produced by Strecker degradation, lipid oxidation and esterification to produce ketones and aldehydes. Significantly higher odor activity values for 2,3-butanedione, hexanoic acid, and esters and significantly lower odor activity values for 2-heptanone enhanced the frankincense odors and creaminess of the post-heated fermented milk. With temperatures increasing to 95 °C, the increased ketones were primarily 2-heptanone, 2-nonanone, and 2-undecanone that originated from the oxidative decomposition of unsaturated phospholipids at high temperatures. The Maillard reaction of dipeptides produces nitrogenous heterocycles that trigger a caramelized flavor, while organic acids interact with proteins to form complexes that produce astringent flavors. These increase the oxidative off-flavors and reduce the overall palatability. These findings provide a scientific basis for optimizing the post-heating temperature process of fermented milk. • Fermented milk was heated at 55 °C, 65 °C, 75 °C, 85 °C and 95 °C for 25s to obtain PHT samples. • Sixty-three volatiles were identified by using HS-SPME-GC/MS. • 2,3-butanedione, hexanoic acid, and esters are characteristic flavor compounds of 65–75 °C PHT samples. • 65–75 °C PHT samples exhibit strong creamy and frankincense aromas, along with the highest consumer preference.