Effect of particle size on composition, physicochemical, functional, and structural properties of insoluble dietary fiber concentrate from citrus peel

To investigate the composition, physicochemical, functional, and structural properties of citrus insoluble dietary fiber concentrate from citrus peel affected by different particle sizes, citrus insoluble dietary fiber concentrate was modified by coarse crush and superfine grinding treatments. The results showed that the contents of hemicellulose and lignin significantly decrease and a significant increase in cellulose and insoluble dietary fiber contents with the reduction in particle size. In addition, the markedly decreased particle size and obviously microstructural changes of citrus insoluble dietary fiber concentrate powder were observed. The color value of citrus insoluble dietary fiber concentrate was observably improved, crystallinity and thermal stability of modified fiber slightly increase with the decrease in particle size, which is due to the partial elimination of hemicellulose and lignin after the treatments. However, water holding capacity, water swelling capacity, and oil holding capacity were found to be lower with the reduction in particle size, which might be attributed to the fact that superfine grinding treatment destroyed the structure integrity, thus causing some soluble components to break away from the cellulose backbone, or due to aggregation of smaller granules. The present study suggested that decreasing the particle size could effectively change some properties of citrus insoluble dietary fiber concentrate, which will provide new perspectives for the application of citrus insoluble dietary fiber concentrate in food products.