Microbiological properties of labneh (concentrated yoghurt) stored without vegetable oil at room or refrigeration temperatures

Abstract

Labnehs (concentrated yoghurts) were made from cow or goat milk (and produced directly from either yoghurt or strained yoghurt) and stored without submersion in vegetable oil at either room or refrigeration temperatures. The results showed that total aerobic mesophilic bacterial counts decreased during storage at both temperatures. Yeast and mould counts, however, increased especially in the samples stored at room temperature due to increased acidity during storage. The number of aerobic spore-forming bacteria decreased, although it was high at the beginning of storage. The number of psychrotrophic bacteria significantly decreased after 60 days in the samples stored at refrigeration temperature and to a smaller degree decreased in the samples stored at room temperature. The statistical analysis showed that the variety of milks and draining of the yoghurts and their interactions had no effect on the growth/survival of total aerobic mesophilic bacteria and psychrotrophic bacteria (P>0.05). However, storage time had a significant effect on the growth of aerobic mesophilic bacteria and aerobic spore-forming bacteria (P<0.01) and yeast, mould and psychrotrophic bacterial counts (P<0.05). No coliform bacteria and Escherichia coli were detected in any sample. The labnehs were consumable for a short period of time, if stored at room temperature and for 180 day, if stored at refrigeration temperature.