Hot-air drying vs. lyophilization of sugar beet flakes for efficient pectin recovery and influence of extraction conditions on pectin physicochemical properties

Abstract

This study assessed the influence of drying pretreatment and extraction conditions (type of acid and particle size of plant material) on the yield and physicochemical properties of pectin from sugar beet flakes resulted as by-product of sugar beet processing in the sugar industry. The results indicated that the drying conditions (hot-air drying and lyophilization) affected the extraction yield, the chemical composition of pectin, its color, degree of methylation and acetylation, molecular weight, and its rheological and emulsifying properties. The best results for pectin yield (16.20%), galacturonic acid content (91.19 g/100 g), degree of methylation and acetylation (66.93 and 23.87%), and molecular weight (3.89 × 105 g/mol) were obtained when sugar beet flakes were pretreated by hot-air drying, and the extraction was made with citric acid using plant material with particle sizes of 125–200 μm. This pectin also had high emulsion activity (51.42%) and emulsion stability (88.03%). The FT-IR spectra were similar, while pectin thermal behavior was affected by the drying pretreatment and extraction conditions. The results of this study showed that from this by-product of the sugar industry it can be extracted high quality pectin with rheological and emulsifying properties that are superior to commercial citrus and apple pectin.