Characterisation of a malty-compound producing Lactococcus lactis subsp lactis biovar. diacetylactis C1 strain isolated from naturally fermented milk

Sammendrag

We previously described the characteristics of LAB isolated from naturally fermented milk produced in Zimbabwe. Among these isolates, strain Lactococcus (L.) lactis subsp. lactis biovar. diacetylactis C1 produced acceptable fermented milk to a sensory panel despite the presence of a slight malty flavour. This strain also showed good growth in milk and produced appreciable quantities of flavour compounds normally present in fermented milks. The aim of this study was therefore to determine whether strain L. lactis subsp. lactis biovar. diacetylactis C1 produced any known malty compounds in fermented milk. The volatile organic compounds were analyzed by GC-MS, using a dynamic gas-purging headspace technique with Tenax-TA adsorbent. Nine compounds could be identified from the 21 chromatographic peaks detected. The malty compounds, 2- and 3-methylbutanal as well as their corresponding alcohols, 2- and 3-methyl-1 1-butanol were among the identified compounds. L. lactis subsp. lactis biovar. diacetylactis C1 was also tested for inhibition of indicator strains of Enterococcus, Escherichia coli, Lactobacillus, Lactococcus and Pediococcus. An inhibition zone was observed around Escherichia coli LMG 2700 strain suggesting that strain C1 may produce inhibitory substances against this strain. No inhibitory activities of the strain were observed against the other tested strains.