Potential Using of Ulvan Polysaccharide from Ulva lactuca as a Prebiotic in Synbiotic Yogurt Production

Abstract

Background and objective: There is growing interesting for edible marine algae species as a source for beneficial polysaccharides. Ulva lactuca is a widespread macroalga and highly consumed by humans and livestock because of its great nutritional values. Many studies showed that different extracts of U. lactuca possess nutritional and biological values. Ulvan is one of its structural water-soluble sulfated polysaccharides. The main objective of this study is preparing synbiotic yogurt by using ulvan polysaccharide by different percentage as a prebiotic ingredient and using probiotic starter bacteria in the manufacture of set synbiotic yogurt. Then study the quality properties of the resultant synbiotic yogurt. Methodology: ulvan polysaccharide was extracted from Ulva lactuca using the methods of hot water-extraction and ethanol-precipitation. The synbiotic yogurt was prepared from fresh skim milk and ulvan polysaccharide as prebiotics, which was added by different concentrations: 1%, 2% and 4% (w/v). The mixtures were heated to 90°C for 10 min and immediately cooled to 39°-40°C; and inoculated with 3% of probiotic starter culture (containing of Lactobacillus acidophilus LA-5 Streptococcus thermophilus TH-4, and Bifidobacterium sp. Bb-12). The inoculated milks were distributed into 100 mL plastic cups and incubated at 40°C till complete coagulation. The synbiotic yogurt were transferred to the refrigerator at 7° ± 1°C and storage for 9 days; then the treatments were analyzed for the bacteriological, physical, chemical, and organoleptic assessments at fresh time and after 9 days of cold storage. Results: The results showed that adding of 1-2% of the ulvan polysaccharide presented synbiotic yogurt with good chemical and physical properties, as well as stimulated the growth and activity of probiotic bacteria. But the addition of high percentage (4%) gave opposite results in terms of flavor, delayed fermentation and weak texture with syneresis also. Conclusion: Therefore, it is recommended to use ulvan polysaccharide as prebiotic in the manufacture of synbiotic yogurt by adding 1-2%; and the flavor can be improved by adding any natural flavor to the synbiotic yogurt..