Pearling affects the lipid content and composition and lipase activity levels of wheat (Triticum aestivum L.) roller milling fractions

Wheat bran contains most of the dietary fiber, vitamins, minerals, and antioxidants of the grain. Unfortunately, it readily deteriorates upon storage because it has high lipid contents and lipase activity levels, which can cause rancidity and, hence, when used in food systems, inferior product quality. We here examined the lipid composition and the lipase activities of wheat bran and the impact of pearling prior to milling thereupon. The lipid content of the outer bran layers (2.31% on a dry matter [dm] basis) is lower than that of regular bran (3.81% dm). Nevertheless, these layers have the highest concentration of free fatty acids (FFA, 0.56% dm), which is ascribed to lipid hydrolysis. Indeed, the lipase activity levels in the peripheral layers were three times higher than in the bran itself. Abrading these tissues by pearling prior to milling yielded a bran fraction with about 30% lower FFA content and 30% lower lipase activity level. Pearling offers opportunities to lower the FFA content and lipase activity levels in wheat bran and, hence, to contribute to an improved storage stability of bran.status: publishe

Differences in endosperm cell wall integrity in wheat (Triticum aestivum L.) milling fractions impacts on the way starch responds to gelatinization and pasting treatments and its subsequent enzymatic in vitro digestibility

Wheat grain roller milling disrupts the starch containing endosperm cell walls and extracts white flour. Many wheat based food processes involve simultaneous use of heat and water which then cause starch to gelatinize and enhance its digestibility. In this study, the impact of starch enclosure in intact endosperm cell walls on starch physicochemical properties and digestibility was investigated. Wheat kernels milled into coarse farina (average particle size 705 µm) contained a substantial portion of intact cells and exhibited 15 - 30% lower Rapid Visco Analyzer peak viscosity readings than flour and fine farina (average particle size 85 and 330 µm, respectively) since its higher level of intact cell walls limited the swelling of the enclosed starch. Xylanase use in situ substantially degraded coarse farina cell walls and increased its swelling and viscosifying potential. Following full gelatinization of the different samples, the starch in coarse farina was digested at a 40% lower rate in an in vitro gastrointestinal digestion assay, but still to a similar extent than that in fully gelatinized flour. This indicates that while wheat endosperm cell walls are permeable to pancreatic amylase, they can sufficiently slow down enzyme diffusion. When xylanase treatment was performed after starch gelatinization and pasting, the rates of starch digestion were similar for all samples evidencing that cell walls act as physical barrier to enzyme diffusion and thus retard its digestion. The present findings offer ways to produce wheat-based foods with sustained energy release benefits.status: accepte

Factors affecting mental health of health care workers during coronavirus disease outbreaks (SARS, MERS & COVID-19): A rapid systematic review.

IntroductionThe novel Coronavirus Disease (COVID-19) outbreak currently puts health care workers at high risk of both physical and mental health problems. This study aimed to identify the risk and protective factors for mental health outcomes in health care workers during coronavirus epidemics.MethodsA rapid systematic review was performed in three databases (March 24, 2020) and a current COVID-19 resource (May 28, 2020). Following study selection, study characteristics and effect measures were tabulated, and data were synthesized by using vote counting. Meta-analysis was not possible because of high variation in risk factors, outcomes and effect measures. Risk of bias of each study was assessed and the certainty of evidence was appraised according to the GRADE methodology.ResultsOut of 2605 references, 33 observational studies were selected and the identified risk and protective factors were categorized in ten thematic categories. Most of these studies (n = 23) were performed during the SARS outbreak, seven during the current COVID-19 pandemic and three during the MERS outbreak. The level of disease exposure and health fear were significantly associated with worse mental health outcomes. There was evidence that clear communication and support from the organization, social support and personal sense of control are protective factors. The evidence was of very low certainty, because of risk of bias and imprecision.ConclusionSafeguarding mental health of health care workers during infectious disease outbreaks should not be treated as a separate mental health intervention strategy, but could benefit from a protective approach. This study suggests that embedding mental health support in a safe and efficient working environment which promotes collegial social support and personal sense of control could help to maximize resilience of health care workers. Low quality cross-sectional studies currently provide the best possible evidence, and further research is warranted to confirm causality

Effect of wheat endosperm cell wall structures on starch physico-chemical properties and digestibility

Starch is the most abundant glycemic carbohydrate in a normal human diet. Lowering the rate of its digestion in the small intestine provides a unique opportunity to maintain optimal blood glucose and insulin levels. Wheat milling into white flour disrupts the endosperm cell walls. One can assume that these cell walls can act as a physical barrier to the amylolytic enzymes during digestion. Against this background, the aim of this study was to investigate the impact of the degree of starch enclosure in wheat endosperm cellular structures on its physico-chemical properties and digestibility before and after hydrothermal processing. Hard wheat (Triticum aestivum L) kernels were milled and separated into different size fractions: regular flour (average particle diameter: 85 μm), fine (330 μm) and coarse (710 μm) farina. Epifluorescence microscopy images showed that the coarse particles had a significantly higher level of intact cells than regular flour. The coarse farina particles exhibited substantially retarded and, at the same time, up to 25% lower starch swelling than flour and fine farina, clearly indicating that the surrounding matrices impose physical restraints to starch swelling. Rapid Visco Analyzer (RVA) peak viscosity values at a dry matter content of 12% w/w were 4,121 cP for fine farina and 3,316 cP for coarse farina as a result of the increased cell walls intactness. At the same time, coarse farina exhibited lower breakdown values (1,005 cP) than did fine farina (2042 cP), since intact cells are more resistant to the applied shear. To fully comprehend the impact of the cell walls on starch pasting, Bacillus subtilis xylanase was added during RVA analysis to in situ hydrolyze arabinoxylan, the main cell wall component of wheat endosperm tissue. The peak viscosity values of coarse farina increased from 3,316 to 3,597 cP upon cell wall hydrolysis indicating that removing the physical barriers allowed starch granules to swell to a larger extent. Moreover, the breakdown values increased from 1,005 to 1,436 cP since the granules were more susceptible for disintegration once the cell walls were (partly) broken down. Nevertheless, the starch gelatinization properties such as measured by Differential Scanning Calorimetry were not affected by the degree of cell wall intactness. Finally, the rate and extent of in vitro starch digestibility went hand in hand with the degree of cell wall disintegration of the study samples indicating that the cell walls have a substantial impact on starch digestibility by acting as physical barrier and/or changing starch physico-chemical properties. In conclusion, intact wheat endosperm cell walls drastically limit the swelling and viscosity development of starch and, at the same time, retard (and limit) in vitro digestibility, offering innovative opportunities to design novel cereal-based products with potential claims on sustained energy release.status: publishe

Impact of multivalent ions on the gel forming capacity of potato (Solanum tuberosum) flakes and on texture and fat content of snacks made thereof

status: Published onlin

Steeping and germination of wheat (Triticum aestivum L.). I. Unlocking the impact of phytate and cell wall hydrolysis on bio-accessibility of iron and zinc elements

In wheat aleurone cells iron and zinc ions occur as phytate structures. Phytate and arabinoxylan cell wall material resist digestion in the human gastro-intestinal tract resulting in very low mineral bio-accessibility. During wheat germination, enzymes make nutrients available for plant development and, when used in foods, for human uptake. We here provide understanding of the impact of the wheat matrix on mineral bio-accessibility. A multifactor experiment in which wheat was subjected to multiple combinations of steeping time (8–36 h), steeping temperature (15–40 °C), germination time (0–120 h) and germination temperature (15–30 °C) showed that steeping for 36 h at 15 °C and germination for 120 h at 26 °C decreased phytate content from 0.96% to 0.65% of initial dry matter (idm) and increased water extractable arabinoxylan content from 0.48% to 1.34% of idm due to phytase and endoxylanase action, respectively. While the iron and zinc bio-accessibility in the wheat grains was 5 and 3%, respectively, that in the germinated grains was 6 and 8% when the cellular matrix was preserved, and 22 and 21% when it was mechanically disrupted. This study thus revealed that controlled steeping and germination of wheat can substantially improve mineral bio-accessibility when the cell walls are broken down.status: Published onlin

Starch isolation method impacts soft wheat (Triticum aestivum L. cv. Claire) starch puroindoline and lipid levels as well as its functional properties

Wheat (Triticum aestivum L.) kernel hardness is a major quality characteristic, which has been ascribed to the presence of puroindolines a and b. These proteins occur in higher levels at the surface of water-washed starch granules from soft wheat cultivars than at that of starch from hard wheat cultivars. In the present study, prime starch was isolated from flour from soft wheat (cultivar Claire) using a dough ball or batter based separation method. Starch isolated with the dough ball method contained lower levels of puroindolines, as well as of other starch granule associated proteins and lipids than that isolated with the batter method. Similar patterns of puroindoline and lipid levels after starch isolation can presumably be related to (polar) lipid binding by puroindolines. Both isolated starch fractions showed comparable differential scanning calorimetry thermograms, whereas higher levels of starch surface associated components restricted starch swelling. Necessary controls demonstrated that the observed differences did not arise from artefacts associated with hydration, fractionation or freeze-drying in the experimental protocols. Apparently, proteins and lipids at the starch granule surface impact water absorption and, as such, starch swelling, but they do not affect starch granule internal phenomena such as melting of the crystalline amylopectin chains.status: publishe

The impact of controlled steeping and germination of wheat on hydrolysis of phytate and arabinoxylan and mineral bio-accessibility

Wheat whole grain food products deserve to be an important part of a healthy diet as they reduce the risk of developing diet-related disorders such as obesity, type II diabetes, cardiovascular disease and cancer. Their health benefits are mainly ascribed to the high concentrations of dietary fiber and other bio-actives such as B vitamins and minerals in bran. However, these bio-actives are entrapped in cells with rigid walls which withstand conventional milling and digestion by the human enzyme arsenal. Moreover, wheat phosphorus is mainly stored as phytic acid which chelates divalent cations such as iron and zinc. As a consequence, the bio-accessibility of wheat minerals only amounts to 5 to 25%. Hydrolytic enzymes such as xylanase and phytase are activated and de novo synthesized in wheat aleurone cells to fuel seedling growth. Xylanases hydrolyze and solubilize arabinoxylan (AX), the main aleurone cell wall dietary fibre (DF) component. At the same time, the increase in phytase activity during germination makes phosphate, mineral elements and myo-inositol available for plant growth and development. In a food system context, this is important since opening wheat aleurone cell walls and breaking down phytate structures by (partial) germination may well result in a greater wheat mineral accessibility in the human gastro-intestinal tract. We here studied how steeping and germination affect the wheat DF complex and increase the bio-accessibility of minerals. During steeping (29 h) and germination (120 h) of wheat grains at 15 °C the xylanase and phytase activity levels increased about five times. As a result, the content of water extractable AX (WEAX) doubled during steeping and germination [from 0.5% to 1.0% of initial dry matter (idm)]. However, the phytate content decreased only from 0.96% to 0.81% of idm. The iron bio-accessibility increased from 7% in regular wheat to 15% in germinated wheat. In a next step, we used an I-optimal design of experiments to maximize the impact of controlled steeping (3-36 h; 15-50 °C) and germination (6-120 h; 15-30 °C) on AX and phytate hydrolysis in wheat and, hence, improve the levels of soluble DF and elemental bio-accessibility. The WEAX content was mainly determined by the main effect of germination time and the quadratic effect of steeping temperature. When wheat grains were steeped at 24 °C for 36 h and germinated at 22 °C for 120 h, the WEAX content in wheat increased from 0.5% to 1.3% of idm and the phytate content decreased from 0.96% to 0.61% of idm. We conclude that controlled steeping and germination of wheat offers novel raw materials which can be used for manufacturing cereal products with different DF properties and an improved bio-accessibility of minerals.status: publishe

Extractability and Chromatographic Characterization of Wheat (Triticum aestivum L.) Bran Protein

About 70% of the protein for human consumption is derived from plants, with cereals as the most important source. Wheat bran protein has a more balanced amino acid profile than that of flour. We here for the first time report the amino acid, size exclusion, and SDS-PAGE profiles of bran Osborne protein fractions (OPFs). Moreover, we also investigated how OPFs are affected when physical barriers which entrap proteins in bran tissues are removed. Albumin/globulin is the most abundant OPF. It is richer in lysine and asparagine/aspartic acid than other OPF. Most bran albumin/globulin proteins have a molecular weight (MW) lower than 30 k and their chromatographic profiles differ from those of flour. The prolamin has high levels of proline and glutamine/glutamic acid. It is rich in proteins with a MW of 30 to 45 k and about 66 k reflecting contamination with gliadin from endosperm. The glutelin has high levels of glycine, proline, and glutamine/glutamic acid. Its protein is of intermediate and high MW with little protein with MW lower than 30 k. The high (MWs from 80 to 120 k) and low (MW around 45 k) MW glutenin subunits of flour are also present in bran. The glutelin of wheat endosperm is named glutenin. Ball milling releases albumin/globulin and glutelin but not prolamin. Not all glutelin was endosperm glutenin as a substantial part was entrapped in the aleurone cells.status: publishe

The impact of pearling as a treatment prior to wheat roller milling on the texture and structure of bran-rich breakfast flakes

While wheat bran has an interesting nutritional profile, its inclusion in food recipes can lead to poor structure and sensory quality of the final product. Here, we studied how outer bran layers affect textural and structural properties of breakfast cereal flakes (containing 20 or 40% regular, aleurone-enriched or reconstituted bran). Aleurone-enriched bran was obtained by removing the outer bran layers by pearling and thereby enriching the bran obtained by subsequent roller milling in aleurone tissue while reconstituted bran was obtained by reconstituting aleurone-enriched bran with pearlings. Flakes containing aleurone-enriched bran were more crispy and maintained better hardness during soaking in milk, especially for 40% bran-rich breakfast flakes, than their regular bran containing counterparts. Inclusion of 40% reconstituted bran in the recipe deteriorated the texture and microstructure. The present work demonstrates that pearling offers bran material that is very suitable as ingredient for producing breakfast flakes with improved textural properties.publisher: Elsevier articletitle: The impact of pearling as a treatment prior to wheat roller milling on the texture and structure of bran-rich breakfast flakes journaltitle: LWT - Food Science and Technology articlelink: http://dx.doi.org/10.1016/j.lwt.2014.08.015 content_type: article copyright: Copyright © 2014 Elsevier Ltd. All rights reserved.status: publishe