Optimization of the acid degumming process of tiger nut crude oil by response surface method

Tiger nut (Cyperus esculentus L.) oil, which is a high-quality and healthy edible oil, is rich in unsaturated fatty acids and active components. The phospholipids in the crude tiger nut oil affect not only the quality of the refined oil, but also the subsequent refining efficiency. In order to decrease the phosphorus content in tiger nut degummed oil as much as possible and improve the quality of refined oil better, in this study, the tiger nut crude oil prepared by solvent method was used as raw material, the acid degumming process was investigated. Different solutions including citric acid and phosphoric acid were tested preliminary.It was found that the lowest phosphorus content occurred in citric acid solution. Hence, citric acid was selected in the following experiments. The effects of acid solution mass fraction, acid solution dosage, water dosage, hydration time, acidification time and reaction temperature on phosphorus content and degumming rate of tiger nut oil for single factor experiment were also studied. On the basis of single factor experiment, reaction temperature, water dosage and hydration time were selected as the main indexes for response surface methodology. The response surface optimization experiment with three factors and three levels was conducted to optimize the acid degumming process conditions of tiger nut oil. The order of the influence of variables was reaction temperature > hydration time > water dosage. The optimized process conditions for acid degumming of tiger nut oil were as follows:reaction temperature 59℃, water dosage 3.5%, hydration time 49.5 min. Under the optimized conditions, the degumming rate of tiger nut crude oil was (95.9±0.3)% and the phosphorus content could be reduced to (4.4±0.3) mg/kg. In summary, the degumming of the tiger nut crude oil using citric acid can significantly improve the degumming effect, reduce the phosphorus content, and improve the quality of the oil.