Effect of drying methods on the characterisation of pectin extracted from dried hawthorn fruit

Pectin is a natural complex carbohydrate widely used in the food, chemical, cosmetic and pharmaceutical industries. Hawthorn fruit is a new source for extracting pectin. This study investigated the effects of different drying methods on the characterisation of hot-air-dried hawthorn fruit pectin (ADHFP), microwave-vacuum-dried hawthorn fruit pectin (MVDHFP) and conventional freeze-dried hawthorn fruit pectin (CFDHFP). The apparent viscosity, monosaccharide composition, molecular weight (MW), chemical structure, esterification degree, gel properties and microstructure were compared. Monosaccharide analysis showed that hawthorn fruit pectin (HFP) is composed of glucose (Glu), rhamnose (Rha), galactose (Gal), mannose (Man) and galacturonic acid (GalA). Fourier transform infrared spectroscopy (FTIR) showed no significant structural differences in the three types of pectin. At a concentration of 3% (w/w) in water, all three types of pectin showed pseudoplastic behaviour. However, different drying conditions affected the MW, GalA content, degree of esterification (DE) and gelation capacity of pectin. CFDHP had the highest MW and DE, and the gels formed by CFDHP had the highest hardness, viscosity and chewiness and were bound more tightly to water. ADHFP had the highest GalA content and the lowest number of side chains. Compared with commercial citrus pectin, HFP has high potential in food application.