Abstract
Three essential oils, namely thyme, marjoram and sage, were added to concentrated yoghurt (labneh) at concentrations of 0.2, 0.5 and 1.0 parts per million (ppm). Subsequently, the chemical, microbiological and organoleptic properties of freshly prepared labneh and of the labneh stored at 5 degrees C +/- 1 for up to 21 days were determined. Addition of essential oils affected the pH, soluble nitrogen-to-total nitrogen, total volatile fatty acid and acetaldehyde values of the prepared labneh. On the other hand, total solids and fat-to-dry matter values were only slightly affected. Total viable counts, as well as counts of Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus in the treated labneh increased and reached a maximum after 7 days of storage where after it decreased until the end of the storage period. Yeasts and moulds, coliform bacteria and spore-forming bacteria were not detected in the treated labneh. Of the different treated labneh, labneh containing 0.2 ppm thyme, marjoram or sage oils were organoleptically the most acceptable, and it had a good body and texture that was similar to that of the untreated control. From the results of this study, it can be concluded that 0.2 ppm of thyme, marjoram or sage can be used in order to increase the shelf life of labneh for up to 21days.