Research on the Flavor and Physicochemical Characteristics of Yogurt Fermented by Different Starter Cultures

To screen for a yogurt starter cultures with high viscosity and good comprehensive performance, six types of starter cultures were used to ferment milk in this study. By comparing the physicochemical properties, texture, and rheology, the quality differences of the yogurts fermented by different starter cultures were evaluated. Furthermore, the volatile flavor compounds of the fermented yogurts were identified using electronic nose and headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). The aroma differences in the yogurts fermented with various starter cultures were analyzed using partial least squares-discriminant analysis (PLS-DA) and odor activity values (OAV). Results indicated that in terms of physicochemical properties, rapid acid production was observed in yogurts fermented with L903 and 558 starter cultures, and the yogurt fermented with the L903 starter culture exhibited better water-holding capacity. In terms of texture, the highest hardness, adhesiveness, and chewiness were observed in the yogurts fermented with the 992, 900, and 883 starter cultures, while the samples fermented with the L903 and 558 starter cultures were moderate. Results of rheology showed that the yogurt fermented with the L903 starter culture exhibited higher apparent viscosity than the other samples at high shear rates. Principal component analysis of the electronic nose data clearly distinguished the flavors of the yogurts fermented with the 900 and 558 starter cultures, showing significant differences from the other samples. A total of 39 volatile flavor compounds were identified using HS-SPME-GC-MS, including 4 alcohols, 7 aldehydes, 13 ketones, 4 esters, 9 acids, and 2 alkanes. The yogurts fermented with the 558 and 992 starter cultures had more flavor compounds. The PLS-DA model screened 17 landmark volatile flavor compounds (VIP>1, P<0.05). The OAV results indicated that isopropyl myristate, benzoic acid, 2-butanone, acetic acid, decanal, and 2-hydroxy-3-pentanone might be the primary compounds influencing the flavor differences of the yogurts, and 558 fermented yogurt contained three key flavor compounds with high aroma contribution rates, namely benzoic acid, 2-hydroxy-3-pentanone, and decanal. In summary, L903 fermented yogurt exhibited the highest viscosity, excellent water-holding capacity, and moderate texture performance, but its flavor was average. A yogurt starter culture that produces high viscosity and has good overall performance was screened in this study, laying the foundation for the development of high-viscosity yogurt.