Wheat bran arabinoxylans: Chemical structure, extraction, properties, health benefits, and uses in foods.

Wheat bran (WB) is a well-known and valuable source of dietary fiber. Arabinoxylan (AX) is the primary hemicellulose in WB and can be isolated and used as a functional component in various food products. Typically, AX is extracted from the whole WB using different processes after mechanical treatments. However, WB is composed of different layers, namely, the aleurone layer, pericarp, testa, and hyaline layer. The distribution, structure, and extractability of AX vary within these layers. Modern fractionation technologies, such as debranning and electrostatic separation, can separate the different layers of WB, making it possible to extract AX from each layer separately. Therefore, AX in WB shows potential for broader applications if it can be extracted from the different layers separately. In this review, the distribution and chemical structures of AX in WB layers are first discussed followed by extraction, physicochemical properties, and health benefits of isolated AX from WB. Additionally, the utilization of AX isolated from WB in foods, including cereal foods, packaging film, and the delivery of food ingredients, is reviewed. Future perspectives on challenges and opportunities in the research field of AX isolated from WB are highlighted.

Wheat bran layers: composition, structure, fractionation, and potential uses in foods.

Wheat bran, the main by-product of dry milling of wheat, is currently mainly used in the animal feed industry, but has attracted attention as a food ingredient owing to its high dietary fiber and phytochemical contents, providing excellent physiological effects. The bran layers (aleurone layer, outer pericarp and intermediate layer) contain different compositions, structures, and nutrients, and have different properties. Each layer, when separated and isolated, potentially could find more extensive applications in foods. This triggered interest in isolating the bran layers using milling and wet- or dry-fractionation techniques based on their chemical or physical properties. The recent progress has allowed the production of commercial products from wheat bran layers, particularly aleurone-rich products, enhancing the value of wheat bran layers and their applications in food. The present review highlights the recent advances in studying the chemical composition including distribution of chemical components, physical structure, biopolymer matrix, and physicochemical properties of each wheat bran layer. Technologies to fractionate wheat bran layers and utilization of different bran layers in foods are discussed and reviewed, providing new strategies for improving the value of wheat bran and utilization of wheat bran in foods.

Glycemic Response and Fermentation of Crystalline Short Linear α-Glucans from Debranched Waxy Maize Starch.

The glycemic index (GI) is used to rank foods based on postprandial blood glucose response. GI test requires that 50 g of available carbohydrate be used. Available carbohydrate is often calculated as total carbohydrate minus dietary fiber; yet, AOAC fiber methods do not always include resistant starch (RS). The objective of this study was to examine GI response and fermentation properties of crystalline short-chain α-glucan (CSCA), which has high RS content, but no total dietary fiber (TDF) content as measured by AOAC method 991.43. Using the standard GI method, 10 adults were fed 50 g of waxy maize starch and CSCA, consumed alone and in mixed formulation. Breath hydrogen was also determined over 6 h. Fifty grams of CSCA was not entirely available in vivo, and breath hydrogen testing indicated that CSCA was as likely to ferment. Products high in RS, but with no TDF, would yield reduced GI values, and this calls for the need of a method to define available carbohydrate.

Mechanism and enzymatic contribution to in vitro test method of digestion for maize starches differing in amylose content.

To determine the rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS) contents in a starch sample, the addition of amyloglucosidase is often used to convert hydrolyzates from α-amylase digestion to glucose. The objectives of this study were to investigate the exact role of amyloglucosidase in determining the digestibility of starch and to understand the mechanism of enzymatic actions on starch granules. Four maize starches differing in amylose content were examined: waxy maize (0.5% amylose), normal maize (≈27% amylose), and two high-amylose starches (≈57 and ≈71% amylose). Notably, without amyloglucosidase addition, the RS content increased from 4.3 to 74.3% for waxy maize starch, 29.7 to 76.5% for normal maize starch, 65.8 to 88.0% for starch with 57% amylose, and 68.2 to 90.4% for the starch with 71% amylose. In the method without α-amylase addition, less RS was produced than without added amyloglucosidase, except in maize at 71% amylose content. Scanning electron microscopy (SEM) revealed the digestive patterns of pinholes with α-amylase and burrowing with amyloglucosidase as well as the degree of digestion between samples. To understand the roles of amyloglucosidase and α-amylase in the in vitro test, multiple analytical techniques including gel permeation chromatography, SEM, synchrotron wide-angle X-ray diffraction, and small-angle X-ray scattering were used to determine the molecular and crystalline structure before and after digestion. Amyloglucosidase has a significant impact on the SDS and RS contents of granular maize starches.