Screening of mixed-species starter cultures for increasing flavour during fermentation of milk

Abstract

Flavour is an important factor determining the quality of fermented dairy products. Three L.delbrueckii subsp. bulgaricus isolates and five Streptococcus thermophilus isolates with good fermentation characteristics were selected for evaluation as starter cultures when used in ten different combinations, and in comparison with a commercial starter. Using solid phase micro extraction-gas chromatography-mass spectrometry (SPME-GC-MS) analysis, a total of 55 volatile compounds and nine odour-active compounds were detected in milk fermented by mixed-species starter cultures C5 (L. delbrueckii subsp. bulgaricus IMAU62081: S. thermophilus IMAU40133). The results from partial least squares-discriminant analysis (PLS-DA), electronic nose (E-nose) analysis and sensory evaluation indicated that flavor composition and content of fermentation samples from the C5 mixture were closer to the commercial control than the other mixtures. These results help understand how volatile flavour compounds in yoghurt are affected by the starter culture; this will be useful in the development of value-added fermented dairy products.