Study on the Chemical Compositions and Emulsification Stability of Water-soluble Dietary Fibers from Wine Grape Skin
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Abstract:
Soluble dietary fiber (SDF) was obtained from wine grape skin by two different methods, viz. hot acid and enzymatic methods, and the chemical compositions of the two types of water-soluble dietary fiber, viz. SDF1 (extracted via hot acid method) and SDF2 (obtained using enzyme method), were determined. Subsequently, SDF1 and SDF2 were used to prepare oil-in-water emulsions. The emulsion uniformity was examined using the particle size distribution, while the emulsifying stability was determined using the volume-weighted mean diameter (D4,3). The protein, galacturonic acid, and neutral sugar contents, degrees of methylation and acetylation, and molecular weight of SDF2 are lower than those of SDF1. The emulsions were stored separately for 15 d at 4, 20, and 60 ℃. After storage, the D4,3 value of SDF1 emulsion increases from 1.10 μm to 4.29 μm (4 ℃), 5.72 μm (20 ℃), and 7.57 μm (60 ℃), indicating the higher stability of SDF1 emulsion at low temperatures. After storage, the D4,3 value of SDF2 emulsion increases from 3.73 μm to 17.7 μm (4 ℃), 15.30 μm (20 ℃), and 12.47 μm (60 ℃). Eventually, the values of SDF2 emulsions stored at different temperatures reach ≥12 μm, indicating an unsatisfactory overall stability of SDF2 emulsions. The span of SDF1 ranges from 3.37 to 4.18, which is significantly higher than that of SDF2 (2.84~3.52); therefore, SDF2 is more homogeneous than SDF1. After enzyme treatment, the emulsifying activity of SDF decreases significantly. Hence, the emulsifying stability of SDF can be considerably improved by ensuring the integrity of components such as proteins and neutral sugars in SDF.
