Effect of amylose/amylopectin ratio and extent of processing on the physical properties of expanded maize starches. (8th February 2022)

• Record Type: Journal Article
• Authors: Beech, Daniel; Beech, John; Gould, Joanne; Hill, Sandra
• Is Part Of: International journal of food science & technology. Volume 57:Number 4(2022)
• Page Start: 2298
• Page End: 2309
• Publication Date: 2022-02-08
• Subjects: Amylose/amylopectin ratio -- bubble growth -- expansion -- high temperature RVA -- popping -- starch conversion -- thermomechanical extrusion; Food industry and trade -- Periodicals; 664
• DOI: 10.1111/ijfs.15581
• Languages: English
• ISSNs: 0950-5423

Abstract

Summary: Low‐density expanded starchy products are often desirable, particularly in the snack food industry. Levels of shear and amylose are often deemed crucial factors for expansion. In this study, maize starches containing low (waxy), normal and high levels of amylose were compared after processing. Low shear processing used a popping head (similar to a rice‐cake machine), while high shear (~450 kJ kg −1 ) samples (pellets and directly expanded) were created using twin‐screw thermomechanical extrusion. Native starches and ground extruded materials (<106 µm) were popped using the same conditions (230 °C, 4 s, water content 12% wwb). All samples tested created fused aerated cakes, which had little or no remaining crystallinity, except for the directly popped waxy sample, which retained ~17% of its original crystallinity. Water absorbances and solubilities were influenced greatly by the starch source and marginally by the amount of processing. On processing, waxy samples showed increased solubility while those with normal amylose content had greater absorption. The densities of all the popped samples were similar despite marked differences in shear regime history and the major variations in the amylose and amylopectin ratios. These results challenge the expected relationships between shear and different starches' potential to expand. Abstract : Maize starches containing low, normal and high levels of amylose were popped using a heat press. Samples were popped either directly from native starch powders or with the starch having undergone an intermediate extrusion process. When popping at a sample water content of 12% (wwb), all samples yielded fused, expanded products of similar densities despite further analysis revealing considerable variation in macromolecular order between samples of different starch types and shear histories.