Structural changes to starch after acid hydrolysis, debranching, autoclaving-cooling cycles, and heat moisture treatment (HMT): A review

Starch is a carbohydrate polymer consisting of glucose monomers with alpha-glycosidic bonds comprising amylose (linear chains) and amylopectin (linear and branched chains). Starch modification is generally carried out for two reasons. First, native starch has limited applications. Second, functional properties can be added to starch through the modification to produce resistant starch for use in functional foods. Resistant starch has been revealed to show several health benefits including increasing faecal bulk, lowering colonic pH, and reducing glycaemic response. Acid hydrolysis, debranching, autoclaving-cooling cycles, and heat moisture treatment (HMT) are the common methods involved in resistant starch production. These modifications can lead to changes in the structure of starch related to its resistance to human digestion. Here, the structural changes observed by gel-permeation/filtration chromatography (GPC/GFC), Fourier transform infra-red (FTIR) spectroscopy, X-ray diffractometry (XRD), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) are discussed.