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• The specific impact on VOCs profile of different strains of ST and LB was elucidated. • Ketones, acids and aromatic compounds were predominant. • ST and LB strains showed a strain-specific differential VOCs production. • Only LB strains contributed to acetaldehyde and 2-nonanol formation. • ST strains generated more acetic- and hexanoic- acids, diacetyl, and acetoin. In the dairy industry, a considerable and growing interest is given to the aroma of yogurt and fermented milks (FMs), and the capability of lactic acid bacteria, applied as starter cultures, to naturally improve flavor characteristics. This case study aimed to characterize volatile organic compounds (VOCs) in fermented milks obtained by using industrial starters, either individual or in mix, composed of Lactobacillus delbrueckii subsp. bulgaricus (LB) and/or Streptococcus thermophilus (ST), with the aim to elucidate the impact of each single strain within the same species in the complexity of the microbial communities. Thus, 33 different VOCs, including ketones, acids, aldehydes, alcohols, esters and aromatic compounds were identified through headspace solid-phase microextraction coupled to GC-MS. Only LB produced acetaldehyde (green apple-like) and 2-nonanol (musty), whilst in ST-FM acetic acid (vinegar like), diacetyl (buttery), 2,3-pentanedione (sweet), acetoin (creamy), and hexanoic acid (pungent) were higher compared to LB-FM. Depending on the single strain and their different combinations, noticeable differences in the VOCs profile were observed, showing that, the selection of the proper combinations of ST and LB strains to obtain FMs with a specific final VOCs profile is a key aspect in the dairy industry sector.
Alam et al. (Wed,) studied this question.