Abstract
Saccharomyces boulardii is a unique species of yeast previously characterized as a probiotic strain (CNCM I-745) among a few probiotic yeasts reported to date. Inulin is one of the most common prebiotics that exhibit twisted hydrocolloidal properties in dairy products. The present study was designed to develop a synbiotic yogurt by incorporation of S. boulardii and inulin at 1%, 1.5%, and 2% (w/v), comparing with the probiotic and control plain yogurts. Microrheological, microstructural, microbiological, sensory properties, and volatile compounds of the yogurt samples were evaluated. Microrheological analysis showed that addition of inulin to yogurt slightly reduced the values of G′ and G″, while solid–liquid balance (SLB) values confirmed more solid properties of the synbiotic yogurt (0.582~0.595) than the plain yogurt (0.503~0.518). A total of 18 volatile compounds were identified in the synbiotic yogurt, while only five and six compounds were identified in plain and probiotic yogurts, respectively. Physiochemical parameters such as pH, acidity, and protein content were in the normal range (as with the control), while fat content in the synbiotic yogurt decreased significantly. Addition of 1% inulin not only reduced syneresis but also maintained viability of S. boulardii after 28 days of storage. Microstructural and microrheological studies confirmed the dense, compressed, homogeneous structure of the synbiotic yogurt. Thus, addition of inulin improved the textural and sensory properties of the synbiotic yogurt, as well as survival of S. boulardii with viable count above 6.0 log CFU/g in yogurt, as generally required for probiotics. Therefore, novel synbiotic yogurt with desirable quality was developed as an effective carrier for delivery of the probiotic yeast exerting its beneficial health effects.
Highlights
Yogurt is a type of coagulated milk product with smooth texture, and that has a gentle sour and pleasant flavor that results from lactic fermentation with Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus thermophilus [1]
Prebiotics are a non-digestible part of food, which may serve as nutritional supplements for probiotic microorganisms to enhance their survival chances and implantation in the host intestinal tract [10]
From the texture profile analysis described above, our study indicated that the synbiotic yogurt with 1% inulin exhibited better textural properties, in terms of hardness, adhesiveness, and gumminess, without negatively affecting the palatability of natural yogurt in comparison with the control and probiotic yogurts
Summary
Yogurt is a type of coagulated milk product with smooth texture, and that has a gentle sour and pleasant flavor that results from lactic fermentation with Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus thermophilus [1]. There is an intensified demand for a new range of dairy products, including synbiotic yogurt containing both probiotics and prebiotics [3,4]. Synbiotic yogurt has become increasingly popular as a type of functional food that beneficially affect the health condition of human beings [7,8]. Prebiotics are a non-digestible part of food, which may serve as nutritional supplements for probiotic microorganisms to enhance their survival chances and implantation in the host intestinal tract [10]. There is an increasing interest in addition of inulin and other oligofructose to food products (e.g., yogurt) for their healthful effects (e.g., enhancing Lactobacillus and Bifidobacterium growth in the colon, boosting bioavailability of a variety of minerals like calcium and iron, increasing antioxidant activities, and boosting immune functions) [20]. Attention was paid to the effect of addition of the yeast and inulin on the syneresis of synbiotic yogurt resulted from exclusion of water as surface whey from the network of milk gel, leading to an adverse effect on perception of yogurt consumers
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