Abstract: Red skin seeds of lotus usually produce about 15% of red skin powder in the resurfacing process. It was determined that protein content in red skin of lotus seed is 17.65%. In the present study, the conditions for the salt-extraction of proteins from red skin of lotus seed assisted by microwave, such as the ratio of solid to liquid (m/V), the concentration of NaCl solution, extraction temperature, extraction time and the repeat times of extraction, were investigated using the extraction rate of protein as an evaluation index. On the basis of single factor and orthogonal array design investigations, the optimal extraction conditions were obtained as follows: under the assistance of 600 W microwave irradiation twice-repeated extraction at 35 ℃ for 20 min each time at a ratio of solid to liquid 1:12 (g/mL). Under the above conditions, the extraction rate of protein was 85.52%. When HCl was used to precipitate protein, the precipitation rate of protein was 35.96% at an isoelectric point of pH 4.9. The yield and purity of lotus proteins extracted by this method were 30.75% and 83.67%, respectively. As a conclusion, lotus seed red skin has good development prospects.

Key words: red skin of lotus seed, protein, microwave-assisted salt-extraction