Effects of Three Traditional Heat Processing Methods on the Physicochemical Properties and Structure of Cassava

Cassava (Manihot esculenta Crantz) is one of the three major potato crops in the world. Consumption of cassava necessitates thermal processing, and the impact of such processing on the physicochemical and structural characteristics of cassava remained unknown. In this paper, three traditional thermal processing methods (boiling, steaming and frying) were used to heat-treat cassava. The physicochemical properties (chemical composition, pasting properties, thermal properties) and structural changes (microstructure, long-range ordering, and short-range ordering) of the processed cassava and untreated cassava was characterized by scanning electron microscopy, Fourier transform infrared spectrometry, X-ray diffractometer, and differential thermal scanning calorimetry. The findings indicated a significant reduction in the total starch content of cassava following diverse heat treatments, accompanied by a notable increase in amylose content (P<0.05). The relative crystallinity and short-range ordering of starch in cassava decreased, with a 74.35% decrease in crystal structure after frying and a 65.16% decrease in crystal structure after steaming. The effect of heat treatment on the gelatinization characteristics of cassava was significant: after heat treatment, the peak viscosity and disintegration value showed an overall upward trend, while the gelatinization temperature significantly decreased (P<0.05). Boiling and steaming treatments resulted in a 49.67% and 43.98% increase in recovery value, respectively, while frying treatment decreased by 23.25%. There were no significant differences observed in the thermal properties and infrared spectrum groups among cassava samples that underwent different heat treatments. Generally, steaming treatment exhibited minimal damage to the crystal structure of starch in cassava, boiling treatment enhanced its gel formation and susceptibility to aging while frying treatment demonstrated superior thermal stability. The results can serve as a theoretical reference for selecting appropriate heat processing methods for cassava in food applications and designing a variety of cassava products.