Improving viscosity and gelling properties of leaf pectin by comparing five pectin extraction methods using green tea leaf as a model material

摘要

Leaf pectin product has a great potential in food market; however, due to the low extraction efficiency and poor pectin properties, its applications are limited. To obtain high yield leaf pectin with better viscosity and gelling properties, five pectin extraction methods, including hydrothermal, acidic, alkaline, Viscozyme (R) L and FoodPro (R) CBL extraction were compared using green tea leaf as model material. The results showed that alkaline extract had the highest pectin yield (9.2%) with galacturonic acid content of 41.6%, suggesting high content of homogalacturonan pectin. Its average molecular weight and particle size were 3.34 x 10(5) Da and 296 nm. The alkaline extract showed a strong shear thinning property with a viscosity of about 90 mPas, which was four times as those of other leaf pectin extracts. Its gel rigidity was similar as that of acidic extract, which were about 10 times as those of other pectin solution including commercial citrus pectin. It was deduced that the viscosity of pectin extract was influenced by both HG pectin content and the formation of large polymers, while the gelling property was mainly influenced by the formation of large polymers. Although Viscozyme (R) L extract also had a high yield (8.5%), the high contents of rhamnogalacturonan I & rhamnogalacturonan II pectin and the hydrolysis of the side chains resulted in poor viscosity and gelling properties.