Impact of annealing on the hierarchical structure and physicochemical properties of waxy starches of different botanical origins
Samarakoon, E.R.J., Waduge, R., Liu, Q., Shahidi, F., Banoub, J.H. (2020). Impact of annealing on the hierarchical structure and physicochemical properties of waxy starches of different botanical origins. Food Chemistry, [online] 303 http://dx.doi.org/10.1016/j.foodchem.2019.125344
Plain language summary
Native starches have many disadvantages and require modifications to enhance their functional properties prior to industrial utilization. Annealing is a promising physical modification technique which can improve functional properties of starch without changing their granule structure. Annealing modification occurs when starch granules are heated at a temperature below gelatinization temperature in an excess (> 60%) water content for a fixed period.
In this study, four different waxy starches from different botanical origins (waxy potato, waxy corn, waxy rice and waxy barley) that are devoid of amylose were analyzed for structural and functional properties during annealing. No major changes to the granular surface, crystalline structure pattern and molecular order were observed after annealing modification. However, annealing modification increased the starch gelatinization temperatures, while decreasing the gelatinization temperature range without significantly affecting viscosity properties. The extent of these changes varied depending on the botanical origins. Overall, the generated knowledge would assist in identifying appropriate starch sources and modification for targeted applications in the food industry.
The effect of annealing on structure and physicochemical properties of four different waxy starches were investigated to understand the mechanism of annealing in the absence of amylose. Granule morphology, X-ray pattern, molecular order, and gelatinization enthalpy remained unchanged upon annealing. Relative crystallinity of waxy corn starch increased from 42.4 to 46.1% on annealing, while it remained unchanged in other starches. Annealing increased the gelatinization temperatures, while it decreased the temperature range. Waxy potato starch showed the highest increase in To, where it was 8.1 °C after 72 h of annealing. Viscosity profiles were only slightly affected by the annealing treatment. Susceptibility towards amylolysis increased in waxy corn and waxy barley, while it decreased in waxy potato and waxy rice. This study demonstrated that even in the absence of amylose, annealing caused changes in the structure and properties, however, the extents of these changes varied depending on the botanical origin.