Starch–Protein and Starch–Lipid Interactions and Their Effects on the Digestibility of Starch
The digestibility of starch in grains and grain-based foods is of heightened research interest due to its implications for post-prandial blood glucose levels and diet-related chronic diseases such as diabetes. Interactions between starch and the two other macro-components of grains – proteins and lipids – have modulatory effects on the digestibility of starch and other functional properties. Starch–protein interactions occur within the grain and also during food processing. The protein matrix can interact with starch through mechanisms such as hydrogen bonding, hydrophobic interactions or electrostatic interactions to form discrete film-like structures that reduce the accessibility of starch to enzymes and hence reduce the digestibility of starch. Starch–lipid interactions are exploited for the production of nanoscale structures, such as amylose–lipid complexes, where fatty acids and monoglycerides are the main lipids involved. Amylose–lipid complexes have reduced digestibility and find applications as ingredients in foods for people with diabetes and as encapsulants for bioactive compounds with health-promoting properties.