Improvement of the Physico-Chemical and Sensory Properties of Yoghurt by Supplementation with Starch of Sweet Potato of the NASPOT-12 Variety (Ipomoea batatas L.)

The use of plant extracts in milk fermentation is widely recognised as a means of developing functional dairy products with improved nutritional and biological properties. Plant extracts can improve milk fermentation technology by promoting the growth and acidification rate of beneficial bacteria such as Streptococcus thermophilus and Lactobacillus delbrueckii sp. bulgaricus.The main aim of this study was therefore to improve yoghurt fermentation technology by using starch from the NASPOT 12 sweet potato variety as a thickener and stabiliser, with the aim of finding a solution to the technological defects often encountered in yoghurt manufacture, such as inadequate gel firmness, variations in viscosity, syneresis and whey, and anomalies in sensory properties. The principle of the study was based on investigating the influence of this extract on the physico-chemical parameters and sensory properties of the yoghurt as a function of the 21-day shelf life, depending on the level of incorporation (0%, 1.5%, 2%) of the starch in the yoghurt. The stability of the finished product was monitored by controlling the physico-chemical parameters (pH, titratable acidity, viscosity, total dry extract, fat, Brix degree, density and syneresis control) throughout the two periods (fermentation and post-acidification period) over 21 days in the refrigerator at a temperature of 4°C. The results showed that sweet potato starch stabilised certain parameters (pH, titratable acidity) and significantly improved certain parameters, in particular the viscosity of the yoghurt, reduced the syneresis rate and increased the dry extract rate, titratable acidity, hydrogen potential and Brix degree.