Abstract
Lactobacillus delbrueckii subsp. bulgaricus is one of the predominant lactic acid bacterial species used as starter cultures in industrial fermented dairy manufacturing, as it strongly affects the quality of the products. Volatile flavor compound profiles and fermentation characteristics are considered to be the most important indicators for starter culture screening. In the present study, volatile compounds in milk fermented by 17 test strains of L. delbrueckii subsp. bulgaricus and a commercial strain used as a control were identified using solid-phase microextraction (SPME) methods coupled with gas chromatography mass spectrometry (GC-MS). In total, 86 volatile flavor compounds were identified in the fermented milk upon completion of fermentation, including 17 carboxylic acids, 14 aldehydes, 13 ketones, 29 alcohols, 8 esters, and 5 aromatic hydrocarbon compounds. Various volatile flavor compounds (acetaldehyde, 3-methyl-butanal, (E)-2-pentenal, hexanal, (E)-2-octenal, nonanal, 2,3-butanedione, acetoin, 2-heptanone, 2-non-anone, formic acid ethenyl ester) were identified due to their higher odor activity values (>1). In addition, of the 17 test strains of L. delbrueckii subsp. bulgaricus, IMAU20312 (B14) and IMAU62081 (B16) strains exhibited good fermentation characteristics in milk compared with the control strain. The combination of the volatile flavor compound profile and fermentation characteristics in this work could be useful when selecting lactic acid bacteria that may serve as important resources in the development of novel fermented milk products.
Highlights
Fermented dairy products have played an important role in the human diet for thousands of years
Solid-phase microextraction (SPME) coupled with gas chromatography mass spectrometry (GC-MS) can be used to detect these compounds associated with flavor
Changes in pH were observed in milk during fermentation by each of the 17 test strains of L. delbrueckii subsp. bulgaricus and the control strain (Table 2)
Summary
Fermented dairy products have played an important role in the human diet for thousands of years. The yogurt aroma, involving the volatiles initially present in milk and compounds produced during fermentation and storage, is an important factor that contributes to yogurt quality (Ott et al, 2000; Cheng, 2010). More than 90 flavor compounds have been detected in fermented milk (Ott et al, 1997; Routray and Mishra, 2011). Numerous recent SPME-GC-MS studies have investigated the odorant characteristics of yogurt (Settachaimongkon et al, 2014), cheese (Reale et al, 2016b; Ruggirello et al, 2018), fermented camel milk (Ning et al, 2011), and other fermented foods (Reale et al, 2016a; Di Renzo et al, 2018)
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