Effect of Pasteurization, Centrifugation and Additives on Quality of Concentrated Yogurt (Labneh)

Abstract

Pasteurization of yogurt by heat at 60–80°C or by addition of 0.2 to 2% hydrogen peroxide were investigated. Heat-treatment caused a very pronounced reduction in the bacterial count of yogurt samples. Addition of hydrogen peroxide was not effective at the low levels studied. Higher concentrations of hydrogen peroxide that were effective in reducing the bacterial population persisted in the food for more than 4 weeks. Heat-pasteurization in the presence of hydrogen peroxide, was very efficient in destroying bacterial cells and hastened the disappearance of hydrogen peroxide residues from the food. “Labneh”, which is usually prepared from yogurt by filtering out the whey through a cloth, had an inferior texture when prepared from pasteurized yogurt. Milder heat treatment in the presence of hydrogen peroxide and addition of potassium sorbate and thickeners, greatly improved the quality and the shelf-life of labneh as confirmed by sensory evaluation experiments. Further improvements were possible by preparing labneh using centrifugation at various speeds for a short time.

Manufacturing, properties and shelf life of labneh: a review

“…Since the demand for concentrated yogurt has increased considerably over the recent years, most of the production now takes place in large dairy plants where centrifuges replace cloth bags for the separation of whey. Dagher and Ali‐Ghariebeh (1985) produced labneh from heated yogurt by centrifugation for 5 min at different speeds between 4000 and 11 700 g , and all these labnehs were organoleptically similar to the control made by using a cloth bag.…”

“…Milder heat treatment in the presence of hydrogen peroxide and addition of potassium sorbate and thickeners, greatly improved the quality of labneh as confirmed by sensory evaluation experiments. Further improvements were possible by preparing labneh using centrifugation at various speeds for a short time (Dagher and Ali‐Ghariebeh 1985). The thick consistency of this product makes it a better carrier for a variety of fruits and vegetables.…”

“…Yogurt pasteurization at 60–80°C and the addition of 0.2–2% hydrogen peroxide improved the shelf life of labneh by destroying bacterial cells (Dagher and Ali‐Ghariebeh 1985). However, the addition of propionibacteria improved the keeping quality of the product (Sharal et al .…”

Microbial shelf life quality assessment of a sensory evaluated ready-to-serve Momordica charantia L. (Bitter Gourd) drink

“…Similar to viable plate counts of yogurt, lactic acid bacteria was most probably the dominant microflora that appears on the plate count [28]. Heat treatment, for example, pasteurization may not be a suitable option for the formulation of this RTS drink, as it was reported that the heating of yogurt for 10-15 min at 60°C will cause a reduction in its bacterial count by 97-99% [29]. Other foodborne pathogens possibly present in RTS drinks are Staphylococcus aureus as it is widely present in the environment and could also be contamination from food handlers.…”

Effect of Partial Substitution of Milk Solids With Whey Protein Concentrate Powder in "Labneh" Made by Ultrafiltration

“…Besides the losses of product due to its adherence to the cloth bags are quite higher, therefore, during over the past three decades, several techniques of Labneh manufacture have been developed. In one of them, Labneh is produced from yoghurt by centrifugation (Dagher andAli, 1985 andEl-Kenany, 1995). Alternatively, Labneh may be made by concentrating a mixture of yoghurt and brine (Kharrazi, 1984) using centrifugal separator.…”