Effect of amylose/amylopectin ratio and extent of processing on the physical properties of expanded maize starches

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.

A Novel starch from bitter vetch (Vicia ervilia) seeds: a comparison of its physicochemical, structural, thermal, rheological and pasting properties with conventional starches

“…The physicochemical and functional properties such as pasting, gelatinisation, solubility, swelling and rheological characteristics of different starch sources are significantly different which are attributed to the amylose to amylopectin ratio, morphology of starch granules and crystalline structures. These characteristics may influence the use of starch in food and non‐food applications (Singh et al ., 2004; Beech et al ., 2022). Thus, researchers and manufacturers are looking for new starch sources to fulfil the processing requirements.…”

Effect of popping water content and amylose/amylopectin ratio on the physical properties of expanded starch products with different shear histories

“…Amylose/amylopectin ratio and shear history greatly affected the water interactions of products created and the measures of crystallinity within them. Despite this, as previously reported (Beech et al ., 2022), the ultimate densities of the products were largely unaffected by these factors, particularly when popping within the optimum water content region. As such, water content during popping appears to be the most important factor determining sample aeration/density.…”

“…However, findings in the paper by Beech et al . (2022) indicated that after being expanded in a popping head, at a water level of 12%, the bulk densities of native starch and powders created from starches that had been previously thermomechanically extruded were not greatly different. The variances, in terms of expansion, between waxy, normal and high amylose maize starches were also not obvious, except that native waxy maize starch, unlike the high amylose and normal maize starch, retained much of its crystalline structure when directly popped.…”

“…In addition to the starches, the only other ingredient manipulated in the work of Beech et al . (2022) was the water levels. As water molecules are such an integral part of the starch behaviour, it was considered that the starch/water interactions may have been such that the variances due to the starches were not obvious.…”

Unlocking the potential of pasting properties to predict extrudate characteristics of corn grits blends with high amylose corn starch, potato starch, or rice flour

“…Formulations with 50% potato starch showed low peak temperature (73.8 ± 04 • C), low WAI (4.0% ± 0.2%), and high WSI (49.1% ± 2.5%), whereas 50% Hylon showed high peak temperature (95.0 ± 0.0 • C), medium WAI (4.7% ± 0.2%), and low WSI (18.0% ± 2.5%). Beech et al (2022) found that water absorbances and solubilities of extruded products are greatly influenced by the starch source. In a study of Waramboi et al (2014), a very high correlation among WAI and initial viscosity (r = 0.978), peak viscosity (r = −0.930), trough viscosity (r = −0.961), final viscosity (r = −0.957), and peak temperature (r = 0.784) was found for sweetpotato cultivars.…”