Wholemeal Wheat Research Articles

Measurement of Acrylamide and Its Precursors in Potato, Wheat, and Rye Model Systems

The relationship between acrylamide and its precursors, namely, free asparagine and reducing sugars, was studied in cakes made from potato flake, wholemeal wheat, and wholemeal rye, cooked at 180 degrees C, from 5 to 60 min. Between 5 and 20 min, major losses of asparagine, water, and total reducing sugars were accompanied by large increases in acrylamide, which maximized in all three products between 25 and 30 min, followed by a slow linear reduction. Acrylamide formation did not occur to a large degree until the moisture contents of the cakes fell below 5%. Linear relationships were observed for acrylamide formation with the residual levels of asparagine and reducing sugars for all three food materials.

Application of reflectance colour measurement to the estimation of carotene and lutein content in wheat and triticale

Whole-meal wheat, including both bread and durum varieties, and triticale samples were analysed for their carotenoid content by HPLC, and colour using reflectance spectrophotometry (CIE L*a*b*). A positive correlation between CIE b* (yellowness) and lutein concentration was shown in all wheat groups but was strongest in the durums. There was little correlation between CIE L* (lightness) or CIE a* (redness) and lutein, alpha- or beta-carotene. In contrast, the b* value correlated well with the concentration of alpha- and beta-carotene, and therefore the vitamin A activity, though those wheat groups that did not have a strong correlation were those with the lowest CIE b* values. The durum wheat group had the highest CIE b* value and the highest lutein concentration but a relatively low concentration of beta-carotene.

Debranning of wheat prior to milling reduces xylanase but not xylanase inhibitor activities in wholemeal and flour

Debranning of wheat to remove the outer 7% of the kernel, prior to grinding or milling reduced xylanase activity in wheat wholemeal and wheat endosperm flour by up to 80 and 60%, respectively, whereas there was no significant reduction of xylanase inhibiting activity. Flours obtained after debranning and milling showed no major differences in moisture content, whereas ash content decreased and protein and arabinoxylan content decreased slightly with increasing debranning degree. Part of the xylanase activity in the flour was lost on addition of Triticum aestivum xylanase inhibitor (TAXI). Since TAXI specifically inhibits glycosyl hydrolase family 11 xylanases and since endogenous cereal xylanases belong exclusively to family 10, part of the xylanase activity in the flour is most likely of microbial origin. Debranning also significantly reduced alpha-amylase activities in wheat wholemeal and wheat flour. Debranning prior to milling can, therefore, impact on flour functionality.

Contents of Volume

An affinity-based purification procedure allowed the resolution of two distinct groups of endoxylanase inhibitors with different molecular structures and endoxylanase specificities from wheat wholemeal. The first group comprises the so-called Triticum aestivum L. Endoxylanase inhibitor (TAXI)-type proteins which are of approx. Mr 40 000 and occur in two different molecular forms. These inhibitors were removed from a concentrated cation exchange chromatography fraction from wheat wholemeal on a Bacillus subtilis endoxylanase affinity column. The second group of structurally different endoxylanase inhibitors, the so-called xylanase inhibiting protein (XIP)-type, of approx.Mr 29 000–32 000, with pI values varying between 8·8 and 9·2, was purified from the unbound fraction from the B. subtilis endoxylanase affinity column by chromatography on an Aspergillus niger endoxylanase affinity column followed by gel permeation chromatography. The XIP-type inhibitors are not active against the B. subtilis endoxylanase and were consequently not retained on the B. subtilis endoxylanase column. Further analysis of the XIP-type proteins by high-resolution cation exchange chromatography, SDS-PAGE and iso-electrofocusing, revealed several forms. They had similar endoxylanase specificities and N-terminal amino acid sequences.

Fate of ochratoxin A in the processing of whole wheat grain during extrusion

Ochratoxin A in cereal foods and some other products is controlled in the European Community by recent legislation with the objective of minimizing consumer exposure to this mycotoxin. Few studies have examined losses during processing. The stability of ochratoxin A during extrusion of contaminated wholemeal wheat flour was examined using pilot scale equipment. Factors examined were temperature, moisture content, screw speed and residence time. Ochratoxin A was partially stable with breakdown, increasing with temperature and moisture content. However, even under the harshest conditions likely to be used in commercial practice, maximum loss was no greater than 40%, with a residence time of about 40 s. The chemical properties of ochratoxin A suggest that breakdown might be affected by changes in pH and that further studies are necessary to investigate this possibility.

Debranning of wheat prior to milling reduces xylanase but not xylanase inhibitor activities in wholemeal and flour

Debranning of wheat to remove the outer 7% of the kernel, prior to grinding or milling reduced xylanase activity in wheat wholemeal and wheat endosperm flour by up to 80 and 60%, respectively, whereas there was no significant reduction of xylanase inhibiting activity. Flours obtained after debranning and milling showed no major differences in moisture content, whereas ash content decreased and protein and arabinoxylan content decreased slightly with increasing debranning degree. Part of the xylanase activity in the flour was lost on addition of Triticum aestivum xylanase inhibitor (TAXI). Since TAXI specifically inhibits glycosyl hydrolase family 11 xylanases and since endogenous cereal xylanases belong exclusively to family 10, part of the xylanase activity in the flour is most likely of microbial origin. Debranning also significantly reduced alpha -amylase activities in wheat wholemeal and wheat flour. Debranning prior to milling can, therefore, impact on flour functionality.

Fate of ochratoxin A in the processing of whole wheat grains during milling and bread production

Batches of whole wheat contaminated with ochratoxin A were produced by inoculation with Penicillium verrucosum under controlled conditions in the laboratory. The fate of ochratoxin was followed through initial cleaning, abrasive scouring of the outer grain coat, milling into wholemeal wheat or into 10 milled fractions. Bread was baked from both wholemeal flour and straight-run white flour. Concentrations of ochratoxin A in the cleanings, scourings, and the bran and offal fractions were increased, but reduced in the white flour. Scouring removed up to 44% of the ochratoxin A present, but only a small further loss occurred in the bread-making process. An overall reduction of about 75% could be achieved in white bread using a combination of cleaning scouring and removal of the bran and offal fractions. Maximum overall reduction in producing wholemeal bread was about 40%. The reduction in ochratoxin A that can be achieved must be considered in relation to economic constraints concerning the disposal of wasted grain. Appropriate strategies for the use or disposal of potentially highly contaminated cleanings, scourings, bran or offal must be established.

Affinity Chromatography with Immobilised Endoxylanases Separates TAXI- and XIP-type Endoxylanase Inhibitors from Wheat (Triticum aestivum L.)

Abstract An affinity-based purification procedure allowed the resolution of two distinct groups of endoxylanase inhibitors with different molecular structures and endoxylanase specificities from wheat wholemeal. The first group comprises the so-called Triticum aestivum L. Endoxylanase inhibitor (TAXI)-type proteins which are of approx. M r 40 000 and occur in two different molecular forms. These inhibitors were removed from a concentrated cation exchange chromatography fraction from wheat wholemeal on a Bacillus subtilis endoxylanase affinity column. The second group of structurally different endoxylanase inhibitors, the so-called xylanase inhibiting protein (XIP)-type, of approx. M r 29 000–32 000, with pI values varying between 8·8 and 9·2, was purified from the unbound fraction from the B. subtilis endoxylanase affinity column by chromatography on an Aspergillus niger endoxylanase affinity column followed by gel permeation chromatography. The XIP-type inhibitors are not active against the B. subtilis endoxylanase and were consequently not retained on the B. subtilis endoxylanase column. Further analysis of the XIP-type proteins by high-resolution cation exchange chromatography, SDS-PAGE and iso-electrofocusing, revealed several forms. They had similar endoxylanase specificities and N-terminal amino acid sequences.

A Comparative Analysis of Free, Bound and Total Lipid Content on Spelt and Winter Wheat Wholemeal

Free lipids (FL), bound lipids (BL) and total lipids (TL) were determined by the Soxhlet method in whole ground spelt (Triticum aestivum ssp. spella L.) and hexaploid winter wheat (T. aestivum) samples. Ninety-one samples of spelt and 78 samples of winter wheat were analysed in the present study. The available material is representative of the wide variability found in spell (true spelt forms compared with spell wheat hybrid material). The results show that spell differs from winter wheat by a higher FL and TL content (on average, 1.3 times and 1.2 times respectively). Furthermore, our results demonstrate that FL account for most of the high TL content of spelt Lis compared to winter wheat. Lipid content is a parameter which allows a distinction between spell and winter wheat. This could lie useful for breeders to classify spelt varieties. (C) 2002 Elsevier Science Ltd.

Effect of Fermented Cassava Flour on the Physical, Chemical and Sensory Properties of Brown Bread

The effect of incorporating fermented cassava flour into wheat bread quality was investigated. Peeled cassava roots were chopped, fermented in water and dried for seven days before ground into flour, a process that reduced the cyanide content of cassava from 46mg/Kg to 3.6mg/Kg. Wholemeal wheat flour was prepared from different groups of wheat procured from National Plant Breeding Research Station, Njoro. For preparation of composite flours, wheat flour and fermented cassava flour were mixed in the ratios from 100% wheat flour to 100% cassava flour. Protein content, dough properties, gluten content, loaf volume and organoleptic judgement (crust color, internal color, crumb color, taste and aroma, texture, structure and general acceptability) of baked breads were evaluated. Protein content decreased with increase in the level of cassava substitution, except for the 10% cassava composite flour. Up to 20% cassava flour level of substitution had adequate amount of protein required to produce loaves of acceptable volume and texture. Water absorption, peak time, stability and tolerance index increased with increase in the cassava flour level. These increases were not significant up to 50% level of substitution. The decreases in gluten content and loaf volume were not significant at 10% and 20% cassava flour level of substitution respectively. Organoleptic judgement showed a decrease in the quality of breads, though the decrease was not significant at 20% level.

An improved method for mass rearing of three liposcelid psocids (Psocoptera:: Liposcelidae) infesting stored commodities

An improved method of mass culturing liposcelid psocids is described that enables the production of large numbers of insects with minimal equipment and handling. The key factor was the provision of refuge by the addition of black chart papers (five pieces, each 10×2 cm) inside the culture jars. A culture medium comprising whole wheat (14% moisture content), kibbled wheat, wholemeal wheat flour and brewer's yeast in the proportion of 10 : 10 : 10 : 0.1 (v/v) was tested on Liposcelis bostrychophila, L. entomophila and L. paeta. When reared on this medium with initial colonies of 10 adults, there was a 12-fold increase in L. bostrychophila, 5-fold increase in L. entomophila and an 8-fold increase in L. paeta populations over a 4-week period. The method enables quick and simple extraction and handling of insects. This rearing method produced significantly ( P<0.05) larger population numbers when compared with a range of published and unpublished methods.

Development of anIn VitroEnzymic Digestion Method for Removal of Starch and Protein and Assessment of its Performance Using Rye andWheat Breads

The development of anin vitroenzymic batch method for pretreatment of cereal samples prior toin vitrofermentation is presented. A statistical experimental design is described and the importance of bile and pepsin for the digestibility of starch was investigated. Day-to-day variation was studied by measuring glucose released and total starch in the digestion residue of rye flour. Four samples, wholemeal rye flour and bread, wholemeal and white wheat breads, were tested to evaluate the performance of the digestion procedure. Pepsin and bile enhanced the hydrolysis of slowly digestible starch. The extent of starch hydrolysis in rye and wheat breads (93–95%) was reproducible and about the same as using thermostablealpha-amylase. More soluble fibres were released from the wholemeal rye bread than from the wholemeal wheat bread. The procedure is an efficient method for the removal of starch and protein under physiological conditions prior toin vitrofermentation. The method can also be used as a tool for studying the solubility of dietary fibre (DF).

Development of Ephestia kuehniella (Zeller), Plodia interpunctella (Hübner) and Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae) on kernels and wholemeal flours of Fagopyrum esculentum (Moench) and Triticum aestivum L.

Three stored product moth pests, Ephestia kuehniella, Plodia interpunctella and Corcyra cephalonica were reared on the following five foods: whole buckwheat with pericarp, decorticated buckwheat, wheat var. “Centauro” (kernels), wholemeal wheat flour and whole buckwheat flour. Results showed that achenes of buckwheat with pericarp are a poor food for the development of these species. A low rate of survival to adulthood for E. kuehniella and P. interpunctella was recorded, with a considerable extension of post-embryonic development. Although the mandibles of larvae are strong, they have trouble in breaking the fibrous buckwheat pericarp. It was observed that when the seed was decorticated there was a higher percentage of adults emerged. The emergence of E. kuehniella began, according to the food given, 34–42 days after the eggs were laid. The susceptibility index (s.i.) of achenes without pericarp (s.i. 9.7) was higher than that observed on wheat (s.i. 8.6). The first P. interpunctella adults were found after 29 days on wheat and after 56 days on buckwheat with pericarp. The shortest mean period of development occurred on wheat (34 days) while the longest was on buckwheat with pericarp at 81 days. The highest susceptibility index was on kernels (s.i. 12.8), the lowest one was on buckwheat with pericarp (s.i. 2.3). C. cephalonica began to emerge, according to the food given, after 40–55 days. In this case, fewer adults were recorded from buckwheat with pericarp, but no significant differences among the means of emerged adults on wheat, wholemeal wheat flour and whole buckwheat flour were observed. The longest mean period of development was recorded on wholemeal wheat flour (72 days) while the shortest was on wheat kernels (58 days). The highest value for the susceptibility index was obtained for wheat kernels (s.i. 7.4) and the lowest one for buckwheat with pericarp (s.i. 4.5).

Arabinoxylan Solubilization and Inhibition of the Barley Malt Xylanolytic System by Wheat During Mashing with Wheat Wholemeal Adjunct: Evidence for a New Class of Enzyme Inhibitors in Wheat

Three EBC worts were made with 100% barley malt and eight with 60% barley malt and 40% wheat, of which two had additions of a Bacillus subtilis endoxylanase. The xylose (Xyl) levels of centrifuged wort (indicative of arabinoxylan levels) made from 100% barley malt were 0.46, 0.70, and 0.55% (% dry matter), while the corresponding malt water-extractable Xyl contents were 0.31, 0.44, and 0.41%. The Xyl levels in centrifuged worts from 60% barley malt and 40% wheat (0.37– 0.58%) depended mainly on the water-extractable arabinoxylan content of the starting material. The endoxylanolytic levels of the malts had only minor effect on the resulting Xyl contents of the worts. The increase of Xyl levels during mashing with 40% wheat (0.05–0.10%) were 12–58% lower than 60% of the increase in Xyl with a corresponding 100% malt wort. The addition of the endoxylanase from B. subtilis increased the centrifuged wort Xyl level. Experiments in which the endoxylanolytic activity of malt extracts was measured in the presence of wheat water-extractables provided evidence for the presence of one or more endoxylanase inhibitors in wheat that are inactivated by heat treatment. The wheat inhibitors however did not inactivate the B. subtilis endoxylanase.

Reduction in the Levels of Phytate During Wholemeal Bread Making; Effect of Yeast and Wheat Phytases

Abstract No difference in wheat phytase activity was observed when different types of acid were used to adjust the pH of wholemeal wheat flour suspensions to pH 5·0, the optimum for wheat phytase. When whole wheat bread was made without additives or after adjustment of the dough pH with acetic acid or lingonberry (traditional ingredients in bread making in Sweden), 64%, 96% and 83%, respectively, of the initial phytate was hydrolysed. A small but significant difference between breads with and without yeast or with deactivated yeast was found, indicating that yeast contributed some phytase activity under the conditions of bread making (pH 5·3–5·8 and 30–37°C). The optimum pH of yeast phytase was found to be 3·5. The isomers of IP 5 formed with purified wheat phytase or yeast phytase were studied using sodium phytate as substrate. Wheat phytase formed 1,2,3,4,5-IP 5 whereas yeast phytase formed 1,2,4,5,6-IP 5 . Determination of the isomers of inositol pentaphosphate demonstrated that the reduction in phytate levels in bread compared with wholemeal flour resulted from both wheat and yeast phytase activities.

The application of near infrared reflectance spectroscopy to measure the degree of processing in extrusion cooking processes

NIR spectroscopy has previously been used to study structural changes in starch during the ageing of bread. In the present work, carried out under the Measurement & Testing Programme of the European Commission, this concept has been extended to measurement of starch structure in the products of twin-screw extrusion cooking of cereals. A range of processing conditions was devised to provide increasing levels of SME for the starch and a fairly constant residence time within the high temperature shearing zone on the screws. Thus, SME was used as the dependent variable against which NIR data were calibrated. A correlation coefficient of 0.99 and standard error of calibration of 11 kJ/kg were achieved on products based on wholemeal wheat flour. This result was validated using an independent set of samples with a standard error of prediction of 16 kJ/kg. A spectral interpretation was achieved by studying the spectral pattern associated with the prediction equations.

Effect of formulation on protein breakdown, in vitro digestibility, rheological properties and acceptability of tarhana, a traditional Turkish cereal food

SummaryThree formulations of tarhana, a traditional Turkish fermented yogurt‐wheat mixture used in soups, were prepared in the laboratory. The effects of white or wholemeal wheat flours and amount of yogurt on the protein breakdown, rheology and acceptability of the samples were measured and the samples were compared with single samples of homemade and commercial tarhana from Turkey.Replacement of white wheat flour with wholemeal flour and increasing the yogurt had little effect on protein breakdown, but the true‐ to crude‐protein ratio fell slightly during fermentation. Tarhana soups behaved as pseudoplastics (ñ &lt; 1) at 80°C, and those with ñ values (&gt;0.8) closer to Newtonian flow (ñ= 1) were most liked in mouth feel; however high apparent viscosity and samples with less liked mouth feel were not less liked in overall acceptability than the commercial sample. In vitro digestibility of commercial tarhana was lower than the laboratory prepared tarhana.

Contamination profiles and characterisation of Bacillus species in wheat bread and raw materials for bread production

The Bacillus counts in white and wholemeal wheat loaves produced without preservatives or sour dough were consistently 10 6 cfu g after two days of storage at ambient summer temperatures (25–30 °C). Identified species were B. subtilis (70%), B. licheniformis (24%), B. pumilus (2%) and B. cereus (2%). The dominance of B. subtilis in bread could be explained by the higher resistance to heat of this species as determined by inoculation studies. Among 14 species isolated from retail bread and wheat grains, B. subtilis was the only species associated with ropiness. Samples of raw materials, particularly bran, seeds and oat products, contained low levels (10 0–10 2 cfu g ) of Bacillus spores, surviving a heat treatment (100 °C, 10 min) corresponding to a baking process. Even low spore levels in raw materials, with the frequently isolated species, B. licheniformis (49%) and B. subtilis (10%), resulted in 10 7 Bacillus per g bread crumb in two days as determined by test bakings. The results indicate a need for controlling growth of Bacillus in bread.

Bran and irritable bowel syndrome: time for reappraisal

Summary Whilst following up large numbers of patients with irritable bowel syndrome we got the impression that wholemeal wheat and bran products made people with the condition worse rather than better. One hundred consecutive new referrals, all of whom had tried bran, were questioned to resolve this issue. 55% of patients were made worse by bran whereas only 10% had found it helpful. With the exception of fruit, other forms of dietary fibre were not as detrimental and proprietary supplements were found to be beneficial. All symptoms of irritable bowel syndrome were exacerbated by bran, with bowel disturbance most often adversely affected, followed by abdominal distension and pain. The results of this study suggest that the use of bran in irritable bowel syndrome should be reconsidered. The study also raises the possibility that excessive consumption of bran in the community may actually be creating patients with irritable bowel syndrome by exacerbating mild, non-complaining cases.

Improved Vitamin E Retention By Using Freshly Milled Whole-Meal Wheat Flour During Drum-Drying

The retention of α-tocopherol and certain lipid oxidation parameters were followed in freshly milled or stored (6 weeks) whole-meal wheat flour (WMWF) subjected to drum-drying. Drum-drying is a process used in the manufacture of infant products. The two flours were each mixed with whey powder in the proportion 9:2.4, followed by scalding and fermentation, prior to drum-drying. The lipid oxidation parameters that were followed indicated more pronounced lipid oxidation in stored WMWF, on the basis of a 2-fold higher concentration of free fatty acids and a 10-fold higher O 2 uptake compared with those of freshly milled WMWF. It is concluded that lipid oxidation might have occurred enzymatically as well as nonenzymatically by catalysis with iron and copper