Enrichment of stirred yogurt with soluble dietary fiber from Pachyrhizus erosus L. Urban: Effect on syneresis, microstructure and rheological properties

Yam soluble fiber (YSF) extracted from Pachyrhizus erosus was added (1 g per 100 mL) to a stirred yogurt (SYYSF). Its syneresis and microstructure properties were evaluated and compared to those of a stirred yogurt (SYC) without added YSF. The SYC yogurt exhibited a more compact casein micelle aggregates network than that of the SYYSF yogurt which was more open, relaxed and covered with fibrous structures attributed to the YSF components. The rheological analysis showed that the SYYSF yogurt had lower storage modulus (G′) and loss modulus (G″) values in the linear viscoelastic region than the SYC yogurt, but its flow behavior was characterized by a lower flow index (n), higher consistency index (k), and higher yield stress (τ0) than the SYC yogurt. Incorporation of the YSF reduced significantly the syneresis and produced a more acceptable mouthfeel in the SYYSF yogurt in comparison to the SYC yogurt, indicating the viability of the process to obtain a commercial product.