Development of Shelf Life for Labaneh Using Protective Cultures of L. paracasei and Propionibacterium freudenreichii subsp. shermanii

Abstract

Labaneh (strained yogurt) is a traditional dairy product. It is usually produced without chemical preservatives as Jordanian standards for this product prevent their addition. Its shelf life is limited to two weeks. This research aims to develop the shelf life of labaneh using eco-friendly methods, via the addition of protective probiotic cultures. Protective probiotic cultures were prepared by activating DVI freeze-dried Propionibacterium freuendereichii, subsp. shermanii and Lactobacillus paracasei in sterilized skim milk. Fifty kg of fresh milk was divided into two portions, the first containing the traditional yogurt starter culture (2%) and the second processed by adding both the starter (2%) and protective probiotic cultures (1%). After fermentation, two types of yogurts were produced, and refrigerated for several hours. They were then salted, strained separately to about 25% total solids in a special cloth to produce labaneh paste. The paste was then distributed into two groups of sterilized jars (21 for each) and placed in refrigerated storage. Both types of labaneh (traditional and developed) were evaluated at different time intervals of refrigerated storage (0, 3, 7, 10, 14, 21, 30 days) for their counts of coliform bacteria, yeast and mould, and lactic acid bacteria (LAB), and for their pH, ash, acidity, moisture, protein, fat and titratable acidity. The probiotic count was also evaluated for the developed labaneh. The shelf life of the developed labaneh was determined based on the acidity, yeast and mould counts and organoleptic characteristics. No obvious and significant undesirable changes were seen at 30 days of refrigeration or went beyond the Jordanian standard for the developed labaneh, compared to the traditional one which started to spoil after 14 days. No coliform bacteria were found after 30 days of refrigerated storage in the traditional and developed labanehs. The counts of yeast and mould were generally higher in the traditional labaneh than in the developed one, while the number of LAB was lower in the traditional labaneh than in the developed one. The pH and moisture of the developed labaneh were generally lower than that of the traditional labaneh, but the titratable acidity, ash, protein and fat were higher in the developed one. Regarding the sensory properties, most of the panelists organoleptically preferred the developed one during the storage period. Therefore, it is concluded that the protective probiotic cultures were effective in extending the shelf life of labaneh.