EFFECT OF CAROB GALACTOMANNANS ON STARTER CULTURES VIABILITY AND ON TEXTURAL PROPERTIES OF REFRIGERATED NON-FAT YOGHURT

Low-fat and non-fat yoghurts have some rheological changes particularly in syneresis and viscosity. Hydrocolloids such as galactomannans (locust bean gum: LBG) can act as fat replacers and can improve the rheological properties of low and non-fat yoghurts. The present study investigates the effect of carob galactomannans on both the viability of starter cultures and textural properties of non-fat yoghurt during cold storage period (4 °C). Carob galactomannans were extracted from carob seeds. Yoghurt was made from skimmed milk powder with the addition of starter culture and locust bean gum at different concentrations (0.01, 0.02, 0.05 and 0.1% W/V). The yoghurt was stored for 28 days at 4°C. Changes in starter microorganisms’ viability, pH, viscosity and syneresis were measured after 24h of manufacturing than every 7 days. Results showed that starter culture microorganisms (Streptococcus thermophilus and Lactobacilus bulgaricus) showed better (P<0.05) retention of viability in yoghurt supplemented with galactomannans (0.05 and 0.1%) in comparison with control. LBG did not showed a significant (P<0.05) effect on pH changes during refrigerated storage of yoghurt. However its hydrocolloid improved (P