Purple glutinous rice bran (Kum Doi Saket rice (KUM)) contains high content of edible polysaccharides and anthocyanins and has an excellent antioxidant activity. This research aimed to optimize the extraction of crude polysaccharides from defatted purple glutinous rice bran using an ultrasonic-assisted extraction (UAE) and compared with a hot water extraction (HWE). Results showed that optimal extraction condition was as follows: a defatted rice bran to water ratio of 1:20 w/v, extraction temperature and time of 70 °C for 20 min. Under the optimal extraction condition, the yield of polysaccharide of UAE (4%) was significantly higher than that obtained from the HWE (0.8%). Additionally, antioxidant activities of extracted polysaccharide including IC50 value DPPH, IC50 value ABTS, and FRAP value were 1.09 mg/mL, 2.80 mg/mL and 197 µM Fe2+/g, respectively. It is suggested that the UAE process is promising method to decrease the processing time and to enhance extracted polysaccharide yields by 4 times.

This research aimed to extract polysaccharides and improve the property of sulphate-modified purple glutinous rice bran, cv. Kum Doi Saket. The effects of temperature, ratio of sulphur trioxide-trimethylamine (STMA) to sample and reaction times were studied. The results showed that the degree of substitution (DS) of sulphated polysaccharides was 0.01-0.53. Low molecular weight sulphated polysaccharides were obtained, and the functional groups of the sulphated polysaccharides were confirmed using FT-IR. No enhancement of the antioxidant activity of the sulphated polysaccharides was observed. Interestingly, immunomodulatory activity, including inducing cytokine production (iNOS, TNF-a, IL-1b and IL-10) via up-regulated mRNA expression, was significantly increased by 10-86% when compared to the crude polysaccharides.

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Longan (Dimocarpus longan Lour.) syrup is a novel liquid sweetener produced from longan, one of the traditional and economic fruits in the Northern of Thailand. In this research, the effect of extraction and concentration processes on properties of longan syrup was investigated. There were two extraction methods (juice extractor and hydraulic press) and three concentration methods (direct heating, steam heating and vacuum evaporation). Results overall showed that the extraction method had no significant (p≥0.05) effect on longan syrup properties, while concentration resulted in the quality changes of longan syrup. Concentration using direct heating of longan juice caused reduction of sucrose content, and longan syrup dark in color. The headspace volatile compounds of longan syrup were sampled using direct headspace t e c h n i q u e a n d fu rt h e r c h a r a c t e r i z e d u si n g g a s chromatography-mass spectrometry. The identified volatile compounds could be divided into two groups of aroma characteristics which were (1) floral aroma: 3-methybutyl acetate, (β)-ocimene and 2-phenylethyl alcohol and (2) caramel aroma: butyraldehyde, furfural and benzaldehyde. 2-Phenylethyl alcohol, contributing to floral odor, was retained using vacuum evaporation as a concentration method. Result revealed that the optimal concentration process for longan syrup production was vacuum evaporation, providing the highest floral volatile and lowest caramel volatile. Sensory tests confirmed that longan flavor of the syrup produced from the vacuum evaporation process had significantly higher hedonic scores than other processes.