DOI: 10.14457/tu.the.2019.1318
title: Food product development of roselle soy yogurt

description: Soy yogurt is a healthy functional food for consumers and becoming popular with it nutritious. Soy yogurt produced from fermentation between soymilk and lactic acid bacteria. Moreover, berry fruits are popular added into yogurt. Therefore, soy yogurt is developed to herbal soy yogurt products for increasing nutrients value. Roselle is an interesting herb for used to developed with soy yogurt. The objective of this study was to develop roselle soy yogurt. The specific aims were to compare biological activities and chemical content of extracts, to investigate roselle extract under stress conditions, to isolate lactic acid bacteria for soy yogurt production, to study optimal condition for soy yogurt fermentation and to develop product from soy yogurt and roselle extract. Roselle aqueous extract displayed antioxidant activity and total phenolic content, but no potential to inhibit nitric oxide production in RAW264.7 cell and superoxide ions production in HL-60 cell. After being hydrolyzed, the hydrolyzed extract showed anti-inflammatory, antioxidant and total phenolic content more than the initial extract. The positive marker compound of roselle aqueous extract was chlorogenic acid, coumaric acid, ferulic acid, quercetin and cyanidin-3-o-sambubiosides. In hydrolyzed extract, chlorogenic acid and cyanidin-3-osambubiosideswere disappeared and become derivative compound. The results showed the increment of coumaric acid, ferulic acid and quercetin. Moreover, roselle aqueous extract under stress condition (thermal, moisture, acid, base and oxidation)demonstrated that the conditions of roselle extract for product development were thermal and moisture conditions. Therefore, roselle aqueous extract was developed in reverse spherification form and tested for antioxidant, total phenolic contents and bioactive compound during storage. Antioxidant and total phenolic contents of roselle alginate bead in storage period were significantly decreased in day 7. Besides, chemical fingerprint in roselle spherification was shown to be unstable and significantly decreased in day 14. Likewise, appearance of roselle spherification exhibited the highest scores in sensory evaluation and secondary grade was overall acceptance. For soy yogurt production, Lactobacillus plantarum subsp. plantarum (ATCC 14917) and Pediococcus acidilactici (DSM 20284) were lactic acid bacteria that used for soy yogurt starters. The soymilk and two starter cultures on the various fermentation duration at 37˚C was investigated for stability of physiochemical (viscosity, %acidity, pH, %syneresis, color and bacterial growth) and sensory qualities (appearance, smell, flavor, texture, overall acceptance and overall acceptance when eating with roselle beads). The bacterial growth of soy yogurt at fermentation time 10, 12 and 14 hr were reached to 108 CFU/g and slightly changed during storage. Viscosityand pH were reduced in storage time. Moreover, %acidity, %syneresis and color were increased during period. Organoleptic evaluation of all soy yogurt was not significantly altered at 95% confidence interval. The highest scores of overall acceptances were soy yogurt at fermentation time 10 and 12 hr. The combination of soy yogurt androselle spherification was enhanced overall acceptance scores from participants. Consequently, fermentation duration was influenced to physiochemical and organoleptic qualities of soy yogurt. In addition, roselle spherification can improve flavor of plain soy yogurt.