Location and interactions of starches in planta: effects on food and nutritional functionality

Background: Starch is the major stored carbohydrate in grains and legumes. Apart from nutritional functionality, starch has multiple industrial applications. Starch is synthesised in plant cells along with proteins, lipids, and polyphenols. These macromolecules interact both in planta as well as during downstream processing, e.g., extraction of starch. Scope and approach: Whilst the interaction of starch with protein, lipids, and other hydrocolloids during processing is widely reported, the in planta interactions and their effect on food and nutritional functionality is mostly overlooked. This review provides an overview of mechanisms of interaction of starch with protein, lipids, and polyphenols in planta and the effect of these interactions on food processing as well as human nutrition. Key findings and conclusions: The interaction of starch with other macronutrients as well as polyphenols are described at the granular level as well as at the cellular level and presented in a schematic model (Fig. 1). The granular level interactions such as with surface and internal protein and lipids associated with granules, extra-granular storage proteins and formation of amylose-lipid and polyphenol complexes primarily affect the processing functionality of starch, whereas cellular level interactions and encapsulation enhance nutritional functionality of starch in terms of lowering the metabolic responses from energy dense nutrients. Thus, consideration of in planta interactions among macronutrients as well as with cell walls is important during processing, in both selection of ingredients as well as the formulation of foods.