Surface Association of Flaxseed Oil on Cassava Starch Granules via Prolonged Mild Thermal Treatment: Structural, Pasting, Textural, and Emulsifying Properties

The objective of this study was to evaluate the effect of prolonged mild thermal treatment (65 °C, 7 days) in the presence of flaxseed oil (0.16%, w/w), on the structural, pasting, texture, and emulsifying properties of cassava starch (CS). The resulting sample was designated as CS-oil-h. Confocal laser scanning micrographs showed oil on the interface of starch granules promoted granule agglomeration. DSC and FTIR analyses showed no detectable evidence of amylose–lipid complexes or new covalent bonds. Compared to CS, CS-oil-h exhibited slight variations in pasting temperature and peak time, and significantly lower peak, trough, breakdown, final, and setback viscosities. CS-oil-h gel showed higher hardness, adhesiveness, gumminess, and chewiness when compared to the CS gel. Crucially, CS-oil-h exhibited the best emulsifying ability (60.8%, volume of emulsion layer relative to total tube volume after 30 min standing) and emulsion stability (94.1%, after 7 days of storage). The result suggested that the prolonged mild thermal treatment may have promoted putative surface association between flaxseed oil and the surface of starch granules, which resulted in inhibition of pasting viscosity and improved gel properties and emulsifying ability.