Comparison of quality of apple pectin between conventional solution extraction and microwave-assisted extraction

The physicochemical differences of apple pectin between conventional solution extraction (CSE) and microwave-assisted extraction (MAE) were studied. The yield of pectin, purity and galacturonic acid content by MAE (at pH 1.0, extraction time 20.8 min, power 499 W, solid/liquid ratio=1:14.5) were significantly higher than those by CSE (pH=2.0, extraction time 1.5 h, temperature 85℃, solid/liquid ratio=1:13), and the glass transition temperature (Tg) by CSE obtained by analyzing gel properties of pectin solution was 94℃, which was higher than 82℃ by MAE, but the degree of esterification and viscosity average molecular weight were lower. The brown index, yield stress, apparent viscosity and activation energy of apple pectin solution by CSE were significantly higher than those by MAE, however, total phenolic contents by CSE were significantly lower than those by MAE. The lower C (colour saturation), higher L* (lightness）and H (hue of colour) by CSE were found by the analysis of L*a*b*. The apple pectin by CSE has stronger three-dimensional network by frequency scanning and better gel properties.