Preparation and Characterization of Superfine Longan Powder Rich in Polysaccharides: Optimization of Processing Conditions and Functional Properties.

To prepare superfine longan powder (SLP) rich in polysaccharides without adding extra ingredients, the production condition was optimized via ethanol pretreatment and response surface methodology, and the characteristics of SLP were investigated in contrast with those of the coarse longan powder. The optimal condition was determined to be: the solid-liquid ratio of 1:2, soaking time of 48 h, and ethanol concentration of 75.80%. The results indicated that superfine grinding could reduce particle size and raise the specific surface area of the powders and generate better solubility and dispersibility, but worse flowability and water-holding capacity. Scanning electron microscopy analysis showed that large, uneven particles with visible edges changed to irregular and uniform granules after superfine grinding, and there were no new compositions and chemical groups. The results suggested that ethanol pretreatment combined with superfine grinding is an effective method to solve the technical bottleneck of longan powder produce.