VARIATIONS IN WATER‐SOLUBLE SACCHARIDES AND PHENOLS IN LONGAN FRUIT PERICARP AFTER DRYING

Abstract

ABSTRACT Variations in the contents of water‐soluble polysaccharides (WSP), water‐soluble total saccharides (WSTS), gallic acid and total phenols in longan pericarp tissues of three major cultivars (“Shixia,”“Chuliang” and “Fuyan”) planted in Guangzhou, Gaozhou and Haikou, respectively, were evaluated. Microwave radiation, solar radiation and lyophilization were employed to dry the longan pericarps. A great variation in the contents of WSTS, WSP, total phenols and gallic acid existed in pericarp tissues of longan fruit among the three cultivars, locations and drying methods. The highest content (248.7‐mg glucose equivalents [GE]/g dry weight [DW]) of WSTS was obtained in “Shixia” fruit from Haikou, while the lowest content (58.9‐mg GE/g DW) was detected in “Fuyan” fruit from Guangzhou using lyophilization. WSP content was in a decreasing order except for cv. “Shixia” from Haikou, using the three various drying methods: microwave radiation > solar radiation > lyophilization. The longan pericarp tissues contained a large amount of phenolic compounds. “Shixia” fruit from Haikou had the highest content (49.4‐mg gallic acid equivalents/g DW) of total phenols. The contents of total phenols followed a decreasing order for the three drying methods: lyophilization > microwave radiation > solar radiation. No gallic acid was detected in either fresh or lyophilized pericarp tissues, but it was found in the dried pericarp tissues with a higher content in fruit pericarp tissues dried by microwave radiation than by solar radiation.PRACTICAL APPLICATIONSThere is increasing interest of utilizing saccharides and phenols from plant sources for their uses in medicine and cosmetics. Microwave radiation, solar radiation and lyophilization were employed to dry longan fruit pericarp tissues of three major cultivars in relation to their various production locations, while contents of water‐soluble total saccharides (WSTS), water‐soluble polysaccharides (WSP), total phenols and gallic acid in the pericarp were evaluated after these dryings. Significant variations in the contents of WSP, WSTS, gallic acid and total phenols of longan pericarp tissues among the three major cultivars and various locations and drying methods were found. This study can help utilize better the longan fruit pericarp in practice.