Effect of amylopectin long chains on measured amylose content and their correlation with pasting properties

Molecular structure and linear-non linear rheology relation of rice starch during milky, dough, and mature stages

Immature rice has potential to be used as healthy food. The relation between molecular structure and rheological properties was investigated. The lamellar repeating distance (8.42-8.63 nm) and crystalline thickness (4.60-4.72 nm) were not different among stages indicating a complete lamellar structure even at early stage. The relative crystallinity was higher in dough (39.62 %) than milky (36.69 %) and mature starch (35.22 %) caused by molecular structure, amylose, and amylose-lipid complex. The short amylopectin branched chains (A and B1) in dough starch were easily entangled resulted in higher Payne effect and elastic dominant. Dough starch paste exhibited higher G'_Max (738 Pa) than milky (685 Pa) and mature (645 Pa) starch. In a non-linear viscoelastic regime, small strain hardening was found in milky and dough starch. Mature starch showed the highest plasticity and shear thinning at high-shear strains as the long-branched chains (B3) microstructure was disrupted, disentangled, followed by chain orientation along shear.

High-amylose maize starch: Structure, properties, modifications and industrial applications

High-amylose maize refers to a special type of maize cultivar with a 50 %-90 % amylose content of the total starch. High-amylose maize starch (HAMS) is of interest because it possesses unique functionalities and provides many health benefits for humans. Therefore, many high-amylose maize varieties have been developed via mutation or transgenic breeding approaches. From the literature reviewed, the fine structure of HAMS is different from the waxy and normal corn starches, influencing its gelatinization, retrogradation, solubility, swelling power, freeze-thaw stability, transparency, pasting and rheological properties, and even in vitro digestion. HAMS has undergone physical, chemical, and enzymatical modifications to enhance its characteristics and thereby broaden its possible uses. HAMS has also been used for the benefit of increasing resistant starch levels in food products. This review summarizes the recent developments in our understanding of the extraction and chemical composition, structure, physicochemical properties, digestibility, modifications, and industrial applications of HAMS.

Development of a 96-well plate iodine binding assay for amylose content determination

Cereal starch amylose/amylopectin (AM/AP) is critical in functional properties for food and industrial applications. Conventional methods of AM/AP are time consuming and labor intensive making it difficult to screen the large sample sets necessary for evaluating breeding samples and investigating environmental impact on starch development. The objective was to adapt and optimize the iodine binding assay in a 96-well plate format for measurement at both λ 620 nm and λ 510 nm. The standard curve for amylose content was scaled to a 96-well plate format and demonstrated R(2) values of 0.999 and 0.993 for single and dual wavelengths, respectively. The plate methods were applicable over large ranges of amylose contents: high amylose maize starch at 61.7±2.3%, normal wheat starch at 29.0±0.74%, and a waxy maize starch at 1.2±0.9%. The method exhibited slightly greater amylose content values than the Concanavalin A method for normal type starches; but is consistent with cuvette scale iodine binding assays.