In vitro starch digestibility, edible quality and microstructure of instant rice noodles enriched with rice bran insoluble dietary fiber

Rice bran insoluble dietary fiber (RBIDF) was added into the noodle formulation at a proportion of 3–12% (w/w) to produce instant rice noodles. The eating quality, texture, and microstructure of noodles were investigated. Meanwhile, the effect of RBIDF and its three main components (cellulose, hemicellulose, and lignin) on the in vitro digestion of noodles was further explored. Noodles with 3%–6% (w/w) RBIDF addition showed appropriate textural quality, where 3% RBIDF addition led to the best sensory performance. Scanning electron microscopy (SEM) results showed that 9% or more RBIDF addition caused rough and porous noodles, which decreased eating quality. In addition, 3%–9% RBIDF significantly delayed the hydrolysis of starch during in vitro digestion. The 3% samples exhibited the highest antidigestive properties, with the final degree of hydrolysis reduced from 88.43% to 83.69% and the resistant starch (RS) content increased from 12.64% to 19.78%. Furthermore, the degree of noodle digestibility reduction followed the sequence: hemicellulose > lignin > cellulose. Hemicellulose, which significantly decreased the diffusion of glucose from 98.86% to 78.14%, played a major role in reducing noodle digestibility. These results indicated that RBIDF (≤6%) can significantly reduce the in vitro digestibility of rice noodles without compromising their eating quality.