Effect of exopolysaccharides and inulin on the proteolytic, angiotensin-I-converting enzyme- and α-glucosidase-inhibitory activities as well as on textural and rheological properties of low-fat yogurt during refrigerated storage | Effet des exopolysaccharides et de l’inuline sur l’activité protéolytique, l’activité inhibitrice de l’enzyme de conversion de l’angiotensine I et de l’αglucosidase, ainsi que sur les propriétés texturales et rhéologiques de yaourt allégé en matière grasse au cours du stockage réfrigéré

Whey separation during storage continues to be one of the major problems in low-fat yogurts. Exopolysaccharides (EPS) produced by lactic acid bacteria have been recognized as a solution to this problem. Inulin is accepted as a fat replacer in products such as low-fat yogurts, in addition to providing physiological benefits. A combination of EPS and inulin could give both health- and texture-promoting properties to low-fat yogurt. Therefore, the aim of this study was to comprehensively study the influence of using an EPS-producing strain of Streptococcus thermophilus along with inulin (3%, wt/vol) on the viability of S. thermophilus and Lactobacillus delbrueckii ssp. bulgaricus, their proteolytic, ACE- and α-glucosidase-inhibitory activities, as well on the textural and rheological properties of low-fat yogurt during storage at 4 °C for 28 days. The time to reach a pH of 4.5 was less in the presence of EPS-producing S. thermophilus. However, during storage, EPS and inulin together did not influence the pH and lactic acid, and the effect on ACE-inhibition activity varied with the period of storage. The presence of EPS showed a protective effect on the survival of Lb. delbrueckii ssp. bulgaricus and partially on the extent of proteolysis. The α-glucosidase-inhibitory activity was more apparent in EPS-containing yogurt. The yield of EPS varied with the period of storage, being maximal (110.77 mg·100 g⁻¹)at d 14. EPS-containing yogurts showed lower firmness, spontaneous whey separation, storage modulus, yield stress, consistency index and hysteresis area than non-EPS producing yogurts. It was concluded that low-fat yogurt with a stable and compact texture having anti-hypertensive and anti-diabetic potential could be obtained using an EPS-producing strain of S. thermophilus.