Effect of planetary ball-milling on multi-scale structures and pasting properties of waxy and high-amylose cornstarches

Waxy and high-amylose cornstarches were mechanically modified, and the effects of planetary ball-milling treatment on the multi-scale structures and pasting properties of these cornstarches were investigated. The ball-milling could hardly change the structures and properties of high-amylose cornstarch but result in distinct changes to that of waxy cornstarch. With the thicker semi-crystalline lamellae, larger crystalline amylopectin lamellae, thinner amorphous amylopectin lamellae and more structural rigidity amylose amorphous background region, high-amylose cornstarch showed high resistance to the mechanical disruption during the planetary ball-milling treatment. Consistent with the structural changes, the paste properties of high-amylose starch has negligible changes, but the treated waxy cornstarch showed a reduced pasting temperature and paste viscosity, increased pasting stability and a reduced tendency to retrogradation. The results suggest that planetary ball-milling could be a potential physical method to obtain starch products with relatively low viscosity at high concentration and enhanced pasting stability. Industrial relevance Ball-milling is an eco-friendly and cost-effective physical technique which regulates the structure and therefore the physicochemical properties of polymers. Starch is a natural polysaccharide and has been widely used in foods and non-food products. As starch structure plays a key role in determining its properties, it is highly important to ensure a desirable structure and thus properties to be achieved for specific applications. The present study reveals that planetary ball-milling is an attractive technique to alter the multi-scale structures of starch (in particular waxy starch) and therefore its paste properties. In particular, the treatment displayed a reduced pasting temperature and paste viscosity, an enhanced paste stability at different temperatures and a smaller tendency to retrogradation, which makes starch suitable for a wide range of products such as confections, instant desserts and canned and bottled foods. This enables planetary ball-milling to be a potential physical technique to produce starch products with desired paste behaviors and to expand the industrial applications of starch.