Wheat grain tissue proportions in milling fractions using biochemical marker measurements: Application to different wheat cultivars

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.

The Wheat Aleurone Layer: Optimisation of Its Benefits and Application to Bakery Products

The wheat aleurone layer is, according to millers, the main bran fraction. It is a source of nutritionally valuable compounds, such as dietary fibres, proteins, minerals and vitamins, that may exhibit health benefits. Despite these advantages, the aleurone layer is scarce on the market, probably due to issues related to its extraction. Many processes exist with some patents, but a choice must be made between the quality and quantity of the resulting product. Nonetheless, its potential has been studied mainly in bread and pasta. While the nutritional benefits of aleurone-rich flour addition to bread agree, opposite results have been obtained concerning its effects on end-product characteristics (namely loaf volume and sensory characteristics), thus ensuing different acceptability responses from consumers. However, the observed negative effects of aleurone-rich flour on bread dough could be reduced by subjecting it to pre- or post-extracting treatments meant to either reduce the particle size of the aleurone's fibres or to change the conformation of its components.

Quantification of Protein "Biomarkers" in Wheat-Based Food Systems: Dealing with Process-Related Issues

Selected food proteins may represent suitable markers for assessing either the presence/absence of specific food ingredients or the type and intensity of food processes. A fundamental step in the quantification of any protein marker is choosing a proper protocol for solubilizing the protein of interest. This step is particularly critical in the case of solid foods and when the protein analyte is prone to undergo intermolecular disulfide exchange reactions with itself or with other protein components in the system as a consequence of process-induced unfolding. In this frame, gluten-based systems represent matrices where a protein network is present and the biomarker proteins may be either linked to other components of the network or trapped into the network itself. The protein biomarkers considered here were wheat gluten toxic sequences for coeliac (QQPFP, R5), wheat germ agglutinin (WGA), and chicken egg ovalbumin (OVA). These proteins were considered here in the frame of three different cases dealing with processes different in nature and severity. Results from individual cases are commented as for: (1) the molecular basis of the observed behavior of the protein; (2) the design of procedure aimed at improving the recovery of the protein biomarker in a form suitable for reliable identification and quantification; (3) a critical analysis of the difficulties associated with the plain transfer of an analytical protocol from one product/process to another. Proper respect for the indications provided by the studies exemplified in this study may prevent coarse errors in assays and vane attempts at estimating the efficacy of a given treatment under a given set of conditions. The cases presented here also indicate that recovery of a protein analyte often does not depend in a linear fashion on the intensity of the applied treatment, so that caution must be exerted when attributing predictive value to the results of a particular study.

Wheat germ agglutinin is a biomarker of whole grain content in wheat flour and pasta

When consumed as whole grain, wheat has a high nutrient density that contributes to a healthy diet. Yet, products labeled as whole wheat can still contain a substantial amount of refined grain leading to the confusion for consumers, so a method was designed to determine the whole grain status within wheat-based foods. Wheat germ agglutinin (WGA), a lectin found in the germ tissue of wheat kernels, was evaluated as a biomarker of whole grain wheat. WGA content strongly correlated with the percentage of whole wheat within premade mixtures of whole and refined (white) flours. Then, commercial flours labeled as whole wheat were tested for WGA content and found to contain up to 40% less WGA compared to a whole grain standard. Commercial pasta products labeled as whole wheat were also tested for WGA content and found to contain up to 90% less WGA compared to a whole grain standard. The differences in WGA content were not likely due to varietal differences alone, as the WGA content in common varieties used in domestic wheat flour production varied less than 25%. The levels of other constituents in wheat kernels, including starch, mineral, phytate, and total protein, were not different among the commercial whole wheat flours and pasta products. WGA is a unique biomarker that can identify wheat products with the highest whole grain content. PRACTICAL ABSTRACT: Whole grain wheat has a high nutrient density that can be part of a healthy diet, but products labeled as whole wheat can still contain some refined grain. Wheat germ agglutinin (WGA) was tested as a biomarker to measure whole grain status in wheat-based foods and revealed that some commercial whole wheat flour and pasta contained unexpectedly lower levels of the WGA biomarker compared to a whole grain standard. WGA may therefore be a useful way to test for whole grain wheat content.

Evidence of a Synergistic Effect between Pea Seed and Wheat Grain Endogenous Phytase Activities

Distribution of phytic acid and phytase activity in pea seeds was analyzed and compared with those in wheat grains under identical assay conditions (55 °C, pH 5.5). Most total phytic acid content and phytase activity were found in pea cotyledons. In wheat grains, debranning resulted in a 70% reduction in phytic acid content, whereas more than 40% of the total phytase activity remained. The possibility to hydrolyze phytic acid by use of ground debranned wheat as a source of phytase in blends with pea cotyledon flour was investigated. The Michaelis-Menten parameters for each endogenous enzyme were identified and used to predict the rate of phytic acid hydrolysis. Results demonstrate a synergistic effect between the two phytase activities, enabling a 70-95% reduction of phytic acid depending on pea/wheat flour ratios in a relatively short time (4 h). This reduction appears to be able to increase zinc bioavailability but remains insufficient for iron.

Structural and physiological characterization during wheat pericarp development

The cytological and physiological features of developing wheat pericarp were clearly characterized in this report. Our results may be helpful to articulate the functions of pericarp during the seed development. Although wheat pericarp has been well studied, knowledge of the sequence of events in the process of pericarp development is incomplete. In the present study, the structural development process of wheat (Triticum aestivum L.) pericarp was investigated in detail using resin microtomy and microscopy. Chlorophyll contents, and photosynthetic and respiratory rates, in pericarp were determined using spectrophotometer and an oxygen electrode, respectively. Mineral nutrient contents were also determined using scanning electron microscopy. The main results are as follows: (1) based on the structures and physiological characteristics observed, the developmental process of pericarp was divided into four stages, growth, formation, extinction and maturation stages, pericarp exhibited specific features at each stage. (2) Pericarp development differed in different parts, or varieties, of wheat. The dorsal pericarp had fewer starch grains and slower rates of apoptosis than the abdominal mesocarp. The cross cells in dorsal pericarp had an irregular outline. When compared with soft wheat cv. Yangmai 11, mesocarp cells in hard wheat cv. Xumai 30 had more starch grains, larger cell size and longer development duration. (3) The chlorophyll content, photosynthesis rate and respiratory rate in pericarp increased gradually, reaching a maximum about 16 days after anthesis, and later decreased continually. The photosynthetic rate in pericarp was lower than the respiration rate. (4) The contents of mineral elements in pericarp, such as calcium, zinc, iron and potassium were higher than those in the inner endosperm. The data indicate that wheat pericarp has many functions, e.g. protection, photosynthesis, mineral accumulation, synthesis and degradation of starch.

Whole grains, type 2 diabetes, coronary heart disease, and hypertension: links to the aleurone preferred over indigestible fiber

Higher whole grain cereal intakes are associated with substantially lower risks of type 2 diabetes, coronary heart disease, and hypertension. These reduced risks have been established in large prospective studies that now include millions of person-years of follow-up. We analyze the results of 11 major prospective studies to provide recommendations about whole grain consumption. The following review establishes the amount of whole grains that should ideally be consumed based on prospective evidence; defines the nature of whole grains; identifies that the whole grain evidence is robust and not due to confounding; and provides a detailed assessment of several potential mechanisms for the effect of whole grains on health. We draw the following conclusions. Firstly, to maintain health, 40 grams or more of whole grains should be consumed daily. This is about a bowl of whole grain breakfast cereal daily, but 80% of the population does not achieve this. Secondly, aleurone in bran is a critical grain component generally overlooked in favor of indigestible fiber. Live aleurone cells constitute 50% of millers' bran. They store minerals, protein, and the antioxidant ferulic acid, and are clearly more than just indigestible fiber. Finally, we suggest potential roles for magnesium, zinc, and ferulic acid in the development of chronic disease. If the results of prospective studies were applied to the life-style practices of modern societies there exists the potential for enormous personal health and public financial benefits.

Present status and perspectives on the use of alkylresorcinols as biomarkers of wholegrain wheat and rye intake

Alkylresorcinols (ARs) were first proposed as potential biomarkers of wholegrain wheat and rye intake a decade ago. Since then there has been a considerable body of research which suggests that ARs do meet most criteria of a biomarker of these foods. Results from human studies on plasma AR and their plasma and urinary metabolites strongly indicate that these compounds are responsive to whole grain wheat and rye intake and are correlated with various measures of AR consumption. This review briefly summarises work on the bioactivities of AR and focuses on aspects related to their use as biomarkers of whole grain wheat and rye intake. Evidence suggests that they thus far broadly fulfil the criteria to act as biomarkers of these cereals. However, there are still gaps in the knowledge on factors relating to the wide interindividual variation, and application to different epidemiological cohorts. Overall, ARs are highly promising biomarkers of whole grain wheat and rye intake and add to our increasing understanding of whole grains and health.

Prediction of relative tissue proportions in wheat mill streams by fourier transform mid-infrared spectroscopy

Fourier-transform mid-infrared (FTIR) spectroscopy was investigated as a method to quantify the relative wheat grain tissue proportion in milling fractions. Spectra were acquired with a FTIR spectrometer equipped with an attenuated total reflectance device on ground samples, and the relative tissue proportion was determined according to the biochemical marker methodology as the reference method. Partial least-squares models were developed independently to predict the amount of outer pericarp, aleurone layer, starchy endosperm, and an intermediate layer (made up of inner pericarp plus seed coat plus nucellar epidermis). Good quality of prediction was obtained regardless of the target tissue. The standard errors of prediction obtained for the outer pericarp, intermediate layer, aleurone layer, and starchy endosperm quantification were, respectively, 3.4, 1.3, 3.4, and 4.6%.