Evaluation of physicochemical and sensory properties of half-fat synbiotic stirred yogurt containing Panirak (Malva neglecta) and lactulose

The aim of this study was to investigate the possibility of production of a functional half-fat synbiotic stirred yogurt using Panirak (Malva neglecta) and lactulose (as a prebiotic compound) with an acceptable physicochemical and sensory properties. To produce half-fat synbiotic stirred yogurt samples, Lactobacillus fermentum SL163-4 from a fermented food (Ashkardeh) was isolated and used as probiotic bacteria. Panirak at four levels (0, 5, 10, 15%) and lactulose at three levels (0, 1 and 2%) were used as prebiotic substances. Physicochemical and sensory properties of the yogurt samples were investigated during 21 days of refrigerated storage. Based on the results obtained from the data analysis, it was found that as the level of Panirak enhanced, pH increased and acidity decreased (p<0.05) while by increasing the amount of lactulose and with passing the storage time, pH decreased and acidity increased (p<0.05). Also, by increasing the amount of Panirak and lactulose and with passing the storage time, the extent of syneresis of the yogurt samples decreased (p<0.05). Based on the sensory results, it was found that by addition of Panirak up to 10% level, taste and acceptability of yogurt samples improved (p<0.05), but lactulose caused a significant reduction in these sensory attributes (p<0.05). Furthermore, there were no differences between yogurt samples containing 10 and 15% Panirak and samples having 0 and 1% lactulose. Therefore, according to the results obtained from this study, the use of 15% Panirak and 1% lactulose to produce a functional stirred yoghurt with an acceptable quality is recommended.