Appropriate modification methods can increase the proportion of soluble dietary fiber (SDF). In this study, grapefruit peel insoluble dietary fiber (GP-IDF) was modified with the combined microwave and enzymatic method to obtain SDF. With regard to structural characterization, SDF from grapefruit peel IDF (GP-IDF-SDF) presented as a flat sheet with cracks, composed of a typical cellulose type I crystal, and had good stability below 200 °C. Galacturonic acid, arabinose and glucuronic acid were the main monosaccharide compositions, indicating that pectin might have been the principal component. Moreover, GP-IDF-SDF was excellent in water retention capacity (13.43 ± 1.19 g/g), oil retention capacity (22.10 ± 0.85 g/g) and glucose adsorption capacity (14.49 ± 0.068 mg/g). Thereafter, the effects of GP-IDF-SDF and commercial pectin addition on the color, rheology, texture and sensory properties of blueberry jam were compared. The results showed that the color of jam with GP-IDF-SDF was lighter. The addition of GP-IDF-SDF had less effects on the viscosity and gel strength of jam, but it enhanced the stability of jam. According to sensory data, the color, texture and spreadability of jam with GP-IDF-SDF or pectin were improved and more acceptable. Overall, GP-IDF-SDF had functional characteristics and played a positive role in jam, and it is expected to be a candidate for the development of functional food ingredients.
Keywords: color analysis; modification; monosaccharide compositions; rheology; sensory qualities.