New insights into influencing the extraction efficiency of tigernut oil: Impact of heat on oil absorption and enzymatic hydrolysis of tigernut starch in a starch-protein-oil model system.

Abstract

Tigernut is a potential source of valuable edible oil; however, current oil extraction techniques are inefficient. We assessed high temperature-induced variations in oil absorption and enzymatic hydrolysis of tigernut starch (TS) in the presence of protein to explore the intrinsic reasons for the low oil extraction from tigernut. The results showed that, due to high temperature and the presence of protein, an increase in the volume mean diameters and agglomeration of TS granules occurred. As the temperature increased (80-140 °C), the relative crystallinity (19.09 %-24.40 %) of the long-range ordered structure and the orderliness of the short-range ordered structure increased, the total oil absorption (TOA: 0.25-0.19 g oil/g sample) decreased, and the starch-lipid complex index (2.56 %-24.61 %) increased. With increasing temperature in the range of 170-200 °C, the short-range ordered structure of TS became more compact, and the TOA (0.18-0.14 g oil/g sample) and the starch-lipid complex index (24.61 %-5.64 %) decreased. Changes in the structure of TS led to an increase and then a decrease in its thermal stability, an enhancement of the gel network structure, and a weakening of enzymatic hydrolysis. Results can help reveal the oil absorption mechanism of TS and regulate its physicochemical properties for the efficient extraction of tigernut oil.