Effects of Dietary Fiber Concentration of Nano-sized Bamboo Shoots on the Formation of Yogurt Gel Network

The effect of nano-sized bamboo shoot dietary fiber concentration on gel network of yogurt was studied to provide a theoretical basis for the selection of fiber additions in the processing of high-fibre yogurt. The dietary fiber was degraded by ultrasonic autoclave-assisted enzymatic hydrolysis. The effects of fiber concentration on milk protein adhesion and the network structure of yogurt gel were investigated. Microscopic observations revealed that nano-sized dietary fiber at a high concentration (1.50% w/w) exhibited significant adhesion to milk proteins, thereby affecting the formation of the casein network. Infrared spectroscopy results indicated that the adhesive effect was attributed to hydrogen bonding between the amino groups of casein and the polyhydroxy structure of the fiber. Compared to yogurt without fiber, the addition of nano-sized dietary fiber at a low concentration (0.75% w/w) increased the fermentation acidity by 7.41% and the bound water content by 33.59%, resulting in a stable ''cheese-like'' gel. In contrast, the high-concentration fiber (1.50% w/w) disrupted the molecular orientation of casein through excessive adhesion, leading to an increase in the loss tangent (tanδ) of the gel modulus. This phenomenon compromised the structural stability of the yogurt gel. Therefore, optimizing yogurt processing quality can be achieved by using a low fiber addition concentration (0.75% w/w).