Optimization of microwave-assisted extraction parameter for unsaturated fatty acids in raw potato flours and its application

Abstract: In 2015, the Ministry of Agriculture of the People's Republic of China formally put forward the strategy of using potatoes as the staple food. Potato is one of the most productive crops in China. However, fresh potato is easy to go moldy in storage. Fatty acid is an important component for quality of food. Most of the fatty acid in potato is unsaturated fatty acid which is the necessary nutrient of the human body and has an important physiological function. In this research, we have conducted an orthogonal experiment to determine extraction temperature, extraction time, the proportion of acetone and the solid-liquid ratio for microwave-assisted extraction of unsaturated fatty acid from raw potato flours. The content of unsaturated fatty acid in each group of experiment was tested by the gas chromatographic method. After all the data were acquired, the microwave-assisted extraction process of the unsaturated fatty acid in the raw potato flours was optimized by virtue of Design-Expert 8.05 Analysis and Response Surface Method. Then the optimized program was used for studying the influence of the hot air drying temperature on the content of unsaturated fatty acid of potato. The results allowed us to develop the extraction model (P=0.000 1<0.01，R2=0.939 8) of unsaturated fatty acids in raw potato flours . By use of the model, the optimum extraction technology of unsaturated fatty acids in raw potato flours was obtained and they were, the extraction temperature was 81 ℃, the extraction time was 11 min, the volume ratio of acetone in the extraction solvent was 0.802 5, and the solid-liquid ratio was 3.25:1. The effects of various factors on the content of the unsaturated fatty acids were as follows: the volume ratio of acetone > the solid-liquid ratio > the extraction temperature > the extraction time, and the predicted value of the content of unsaturated fatty acid in the raw potato flours was 1.084 mg/mL. After getting the average value from three replicated tests for the optimal extraction process, the actual value of the content of the unsaturated fatty acid in the raw potato flours was 1.081 mg/g, which confirmed the predicted response value. In the application of optimization scheme, the drying of raw potato flours was operated by making use of different temperature (50, 60, 70, 80 and 90 ℃ ), and the determination showed that, with the increase of the drying temperature, the content of total unsaturated fatty acids had been increased (P<0.05), therein, the content of linoleic acids had also been increased significantly (P < 0.05), and the content of oleic acids and linolenic acids had been also increased, which has been not increased significantly by comparing with the content of linoleic acids. Such change can be attributed to two reasons: on the one hand, the lipolysis had produced the glycerol and fatty acid, on the other hand, the fatty acid has constantly been biosynthesized. Through the research on the influence of hot air drying temperature on the quality of raw potato flours, the optimal hot air drying temperature was obtained according to the index of content of unsaturated fatty acid to realize the optimal quality of raw potato flours after drying so as to promote the strategy of taking potato as the staple food.