RESISTANT STARCH IN BANANAS AND OTHER FRUITS: STRUCTURAL TO MOLECULAR CHARACTERISTICS FOR NUTRITIONAL SIGNIFICANCE AND HEALTH BENEFITS OF CONSUMING

Abstract

Resistant starch (RS) is the fraction of starch that escapes digestion in the small intestine and is instead fermented by microbes in the colon. Bananas, especially when unripe, are among the richest fruit sources of RS, accounting for 40-60% of their total starch content. As bananas ripen, their starch converts into soluble sugars, resulting in a decrease in RS content. Jack Fruit and Bread Fruit also contain significant levels of RS, ranging from 15­35%, which vary based on the cultivar, maturity, and processing methods. The structural properties of RS in fruits are influenced by the ratio of amylose to amylopectin, granule shape, and crystalline structure. Unripe banana starch exhibits B-type crystallinity, making it resistant to enzymatic digestion. As the fruit matures, crystallinity diminishes, affecting its digestibility. Processing methods like heat treatment, retrogradation, enzymatic modification, and dehydration can enhance RS formation by 20­­­­­­­-50%. RS derived from fruits serves as dietary fiber and a texture enhancer in foods. The fermentation of RS produces short-chain fatty acids, notably butyrate, which supports gut health. RS content varies with genotype, maturity, and processing, necessitating optimized processing and cultivar selection for functional foods.