Delaying In vitro gastric digestion of myofibrillar protein gel using carboxymethylated cellulose nanofibrils: Forming a compact and uniform microstructure

In this study, the reinforcement effects of carboxymethylated cellulose nanofibrils (CNF) with different carboxyl degree of substitution (0, 0.36, 0.72, and 1.24 mmol/g) on microstructure and gastric digestion in vitro of myofibrillar protein (MP) gel were investigated. The results showed that the addition of carboxymethylated CNF formed a dense and homogeneous gel network microstructure, thereby increasing the gel hardness and decreased the water mobility. The reinforcement of carboxymethylated CNF in gel structure was greatly depended on the surface charge, but it tended to strengthen and then weaken. The maximum value of hardness and lowest water mobility (T21 and T22) were shown in C0.72 gel, indicating the excessive surface charge would weaken the strengthening effects of particle fillers. Interestingly, the diffusion rate of pepsin was significantly correlated (p < 0.05) with T22, dry mass loss, and degree of hydrolysis (DH), suggesting that water mobility might be a factor associated to diffusion of pepsin, thereby affecting the MP gel gastric digestion. Moreover, a negative and significant correlation (p < 0.05) was observed between gel hardness and gel digestion. To sum up, the gel microstructure was greatly affected by the surface charge of carboxymethylated CNF and denser microstructure could delay the gastric digestibility of MP gel.