EFFECTS OF DIFFERENT METHODS OF DRYING ON ANTIOXIDANT AND MICROSCOPIC CHARACTERISTICS OF Spirullina platensis ENRICHED SOY YOGURT

Abstract

Spirulina platensis was discussed as an active compound with regard to the combined effects with soy yogurt in dried food formulation. Drying influenced the microscopic, and antioxidant properties of soy yogurts, and could be used to create new functionalities. The present investigation aimed to convert Spirulina platensis enriched soy yogurts to powder form by different drying methodologies such as air, vacuum, freeze, and microwave drying and evaluate the microstructure and antioxidant activity of the powders obtained. Antioxidant activities were assayed by using polyphenol assay, estimation of carotenoid content, DPPH radical scavenging activity and FRAP assay. Structural changes were analyzed using a scanning electron microscope and an X-ray diffraction pattern. Freeze-drying was produced significantly high quality dried Spirulina platensis enriched soy yogurt, i.e. better functional and antioxidant properties (Polyphenol 0.211 Gallic acid equivalent. g-1, p<0.001 and DPPH activity 17.48±0.11%, p<0.01 of dried yogurt). In addition, Spirulina platensis enriched soy yogurt exhibited an amorphous type molecular structure in all four types of drying methods adopted. It could be concluded that the freeze-drying method could produce superior quality Spirulina platensis enriched dried soy yogurt powder compared to hot-air-oven and vacuum drying, while it is highly comparable to microwave drying.