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

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 IP₅formed with purified wheat phytase or yeast phytase were studied using sodium phytate as substrate. Wheat phytase formed 1,2,3,4,5-IP₅whereas yeast phytase formed 1,2,4,5,6-IP₅. 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 effect of infrared stabilized rice bran substitution on B vitamins,minerals and phytic acid content of pan breads: Part II

The effect of replacing wheat flour by infrared stabilized rice bran (SRB) at the levels of 2.5, 5.0 and 10.0% on the content of thiamine, riboflavin, niacin, pyridoxamine, pyridoxine, minerals and phytic acid in white wheat, wheat bran, and whole grain wheat breads was investigated. The incorporation of SRB significantly increased the amount of the noted B vitamins, especially niacin, in all bread types (p < 0.05). Zinc, iron, potassium and phosphorus levels of the breads increased gradually and significantly with the inclusion of SRB (p < 0.05). Moreover, phytic acid content of the breads increased proportional to the SRB substitution dose (p < 0.05).     

Formation,characterization, and glucose response in mice to rice starch with low digestibility produced by citric acid treatment

The optimum conditions for producing rice starch enriched in slowly digestible and resistant fractions by citric acid treatment determined by a response surface methodology (RSM) model equation, were: reaction temperature, 128.4 °C; reaction time, 13.8 h; and citric acid, 2.62 mmol/20 g starch. The slowly digestible and resistant starch fractions of the optimally acid-treated rice starch totalled 54.1%, which was 28.1% higher than the control. The slowly digestible and resistant fractions of the acid-treated rice starch did not differ significantly after heat treatment, whereas those of raw rice starch decreased by 49.6–63.8%, depending on the type of heat treatment (cooking at 100 °C or autoclaving). The slowly digestible fraction of the acid-treated starch increased by 8.9–14.2%. After autoclaving, the glucose response of the acid-treated starch was lower than untreated starch, but similar to that of Novelose 330. After heat treatment, the rate of blood glucose decrease was slower for the acid-treated starch than for Novelose 330. Compared to raw rice starch, the acid-treated starch exhibited increases in apparent amylose content, blue value, dextrose equivalent, cold-water solubility and transmittance, and decreases in wavelength of maximum absorbance, viscosity, and gel-forming ability.     

Rabadi fermentation of wheat: Changes in phytic acid content andin vitro digestibility

Fermentation of raw as well as autoclaved wheat flour with buttermilk at 30, 35 and 40°C for 6, 12, 18, 24 ad 48h significantly decreased the level of phytic acid; maximum decrease was observed at 40°C for 48h. Starch as well as protein digestibility (in vitro) improved with an increase in temperature and period of fermentation. Phytic acid had a significant (P<0.05) negative correlation with digestibility (in vitro) of both starch and protein ofrabadi.     

Changes in common wheat grain milling behavior and tissue mechanical properties following ozone treatment

Ozone treatment (10 g/kg) of common wheat grains with a new patented process, Oxygreen^®, used before milling was found to significantly reduce (by 10–20%) the required energy at breaking stage whatever the grain hardness and without changes in the flour yield. Detailed study of each of the milling steps undertaken on a hard type cultivar showed that both the breaking and the reduction energy were decreased. Reduction of the coarse bran yield was also observed concomitantly with an increase in the yield of white shorts. Biochemical characterization of the milling fractions pointed out changes in technological flour properties as starch damage reduction, aleurone content enrichment and increase of insoluble glutenin polymers. Measurement of wheat grain tissue mechanical properties showed that ozone treatment leads to reduction of the aleurone layer extensibility and affects the local endosperm resistance to rupture. These data as well as the direct effect of ozone oxidation on biochemical compounds could explain the observed changes in milling energy, bran and shorts yield and flour composition.     

Sequential fermentation of pearl millet by yeasts and lactobacilli—effect on the antinutrients andin vitro digestibility

Sequential culture fermentation by yeasts (S. diastaticus orS. cerevisiae) at 30°C for 72 hr and then followed by lactobacilli fermentation (L. brevis orL. fermentum) at 30°C for 72 h more resulted in a significant reduction in phytic acid and polyphenol content of pearl millet flour. Fermentation byS. diastaticus andL. brevis combination almost eliminated phytic acid from pearl millet flour. The combinations ofS. diastaticus with both the lactobacilli reduced phytic acid more effectively than those ofS. cerevisiae. The products fermented byS. cerevisiae andL. brevis and byS. diastaticus andL. brevis combinations had the highest protein and starch digestibility (in vitro).     

Effect of solid state fermentation by Enterococcus faecalis M2 on antioxidant and nutritional properties of wheat bran

Wheat bran is the main by-product during wheat flour processing. Although wheat bran is rich in the bioactive compounds and antioxidant capacity, it is not widely utilized in its natural state. To improve the antioxidant and nutritional properties of wheat bran, a dominant strain, Enterococcus faecalis M2, was screened from lactic acid bacteria (LAB) isolated from various foods. Following solid state fermentation, the soluble dietary fiber content of wheat bran nearly quadrupled compared to the raw material. Total proportion of phenols, flavonoids, alkylresorcinols, along with the antioxidant capacity and free radical scavenging rate were significantly improved, particularly the ferulic acid content increased by 5.5 times. Additionally, the free amino acid content increased with degradation of wheat bran protein, whereas the level of anti-nutrient phytic acid decreased. The results of this study could provide an effective method for biological modification of wheat bran, which further enhance the health benefit and utilization of bran.     

Changes in bran structure by bioprocessing with enzymes and yeast modifies the in vitro digestibility and fermentability of bran protein and dietary fibre complex

Bran is a good source of dietary fibre, phytochemicals, and also protein, but highly insoluble and recalcitrant structure of bran hinders accessibility of these components for gastrointestinal digestion. In the present work, influence of bioprocessing on the microstructure and chemical properties of rye bran and wheat bread fortified with the rye bran were studied. In vitro protein digestibility, and release of short chain fatty acids (SCFA) and ferulic acid in a gut model were studied. Bioprocessing of rye bran was performed with subsequent treatments with cell-wall hydrolysing enzymes (40 °C, 4 h) and yeast fermentation (20 °C, 20 h). Bioprocessing of rye bran resulted in reduced total dietary fibre content, caused mainly by degradation of fructan and β-glucan, and increased soluble fibre content, caused mainly by solubilisation of arabinoxylans. Microscopic analysis revealed degradation of aleurone cell wall structure of the bioprocessed rye bran. Bioprocessing caused release of protein from aleurone cells, assessed as a larger content of soluble protein in bran and a higher hydrolysis rate in vitro. Bioprocessed bran had also faster SCFA formation and ferulic acid release in the colon fermentation in vitro as compared to native bran.     

Antioxidant and anti-inflammatory capacity of bioaccessible compounds from wheat fractions after gastrointestinal digestion

Wholegrain consumption is associated with several health benefits, in contrast to the consumption of refined grains. This can partly be related to the antioxidant compounds in the outer parts of the grain kernel. The bioaccessibility of these antioxidant compounds from the wholegrain matrix during gastrointestinal digestion is crucial for their absorption and bioavailability. In the current study, the bioaccessible compounds from aleurone, bran and flour were obtained from a dynamic in vitro model of the upper gastrointestinal tract. They were collected at 1 h time intervals to assess their antioxidant capacity (TEAC assay) and also their anti-inflammatory effect (TNF-α reduction in U937 macrophages stimulated with LPS). The bioaccessible compounds from aleurone had the highest antioxidant capacity and provided a prolonged anti-inflammatory effect, shown by the TNF-α reduction of a relatively late time-interval (3–4 h after start of digestion). The contribution of ferulic acid to those effects was minor due to its low bioaccessibility. Aleurone seems a promising wheat fraction for cereal products with a healthy added value.     

Analysis of polyphenols in cereals may be improved performing acidic hydrolysis: A study in wheat flour and wheat bran and cereals of the diet

Most analytical studies on polyphenols in cereals refer to compounds determined in aqueous-organic extracts and alkali hydrolysates, but an appreciable amount of polyphenols bound to cell wall constituents may remain insoluble in the residues of extraction and alkali hydrolysis. The main objective of this work was to determine if sulphuric acid hydrolysis may release significant amounts of polyphenols to be considered for analytical and nutritional studies. HPLC/MS analyses of polyphenols were performed in methanol–acetone extracts, alkali and sulphuric acid hydrolysates of wheat flour, bran and a pool of cereals of the diet. The amount of polyphenols found in the acidic hydrolysates (200–1600 mg/100 g) was higher than in alkali hydrolysates (0.2–372 mg/100 g). Lower amount of polyphenols were found in the methanol–acetone extracts (44–160 mg/100 g). Hydroxybenzoic, caffeic, cinammic, ferulic and protocatechuic acids were the main constituents of the hydrolysates. The contribution of cereals to the intake of dietary polyphenols in Spain was estimated around 360 mg/person/day (65 mg of extractable and 295 mg nonextractable polyphenols).     

Studies on multigrain milling and its effects on physical,chemical and rheology characteristics of milled streams

The multigrain blends of wheat-green gram-barley in the ratio of C (100:0:0); B1 (90:5:5); B2 (80:10:10); B3 (70:15:15) were co milled using a Buhler roller mill to produce nutritious flour. The studies showed that the yield of straight run flour (SRF) increased gradually with an increase in blending of green gram and barley with wheat. The highest SRF of 79.71% was obtained from the B3 blend. The coarse bran decreased from 15.95% for the control sample to 9.52% for B3 blending. The milling yield of pollard and fine bran showed a decreasing trend from control to B3 blending. In general, flour yield decreased for reduction passages from C1 to C3 and reduction passages produced higher flour compared to break rolls for all blends. The multigrain milling resulted in an increase in protein(113.1–13.35%) and dietary fiber (2.91–4.65%) content of flour, but sedimentation values (52–38 ml), which is the index of flour strength, decreased significantly. The distributions of mineral matters and fat show wide variation among the mill streams and concentrated in coarse and fine brans. The rheological properties of flour obtained showed increased water absorption (55.8–57.5%) and decreased dough stability(5.5–2.8 min), amylograph peak viscosity (388-335BU) and setback (265-224BU) with an increase of multigrain in blends.     

The influence of temperature extremes on some quality and starch characteristics in bread,biscuit and durum wheat

Environmental conditions during grain-fill can affect the duration of protein accumulation and starch deposition, and thus play an important role in grain yield and flour quality of wheat. Two bread-, one durum- and one biscuit wheat were exposed to extreme low (−5.5 °C for 3 h) and high (32 °C/15 °C day/night for three days) temperatures during grain filling under controlled conditions for two consecutive seasons. Flour protein content was increased significantly in one bread wheat, Kariega, under heat stress. Cold stress significantly reduced SDS sedimentation in both bread wheats. Kernel weight and diameter were significantly decreased at both stress treatments for the two bread wheats. Kernel characteristics of the biscuit wheat were thermo stable. Kernel hardness was reduced in the durum wheat for the heat treatment. Durum wheat had consistently low SDS sedimentation values and the bread wheat high values. Across the two seasons, the starch content in one bread wheat was significantly reduced by both high and low temperatures, as is reflected in the reduction of weight and diameter of these kernels. In the durum wheat, only heat caused a significant reduction in starch content, which is again reflected in the reduction of kernel weight and diameter.     

Levels of antinutritional factors in pearl millet as affected by processing treatments and various types of fermentation

Pearl millet (Pennisetum typhoideum) was fermented with Lactobacilli or yeasts alone and in combination, and with natural microflora after various processing treatments, as grinding, soaking, debranning, dry heat treatment, autoclaving and germination. Fermentation was carried out at 30°C for 48 hours withLactobacillus plantarum (LP) andRhodotorula (R) isolated from naturally fermented pearl millet andLactobacillus acidophilus (LA),Candida utilis (CU) and natural microflora (NF). Germination and autoclaving, and debranning and autoclaving were the most effective processing treatments to reduce the phytic acid, amylase inhibitors and polyphenols. There was a further reduction in these antinutrients due to fermentation. Phytic acid and amylase inhibitors were completely eliminated after fermentation in some of the samples especially in soaked, debranned and germinated ones. Polyphenols were altered non-significantly in general but fermentation with Lp+R and NF caused a significant increased in polyphenols.     

Value-addition of agricultural wastes for augmented cellulase and xylanase production through solid-state tray fermentation employing mixed-culture of fungi

Solid-state fermentation (SSF) was performed to evaluate the potential of agricultural residues for the production of cellulase and hemicellulase using individual and mixed cultures of Aspergillus niger and Trichoderma reseei. The maximum filter paper (FP) cellulase activity of 13.57 IU/gram dry substrate (gds), 22.89 IU/gds and 24.17 IU/gds and β-glucosidase activities of 21.69 IU/gds, 13.58 IU/gds and 24.54 IU/gds were obtained with wheat bran medium at 96 h incubation period with A. niger, T. reseei and mixed-cultures of A. niger and T. reseei, respectively. Mixed-culture SSF using rice straw supplemented with wheat bran in the ratio 3:2 resulted in higher FP cellulase, β-glucosidase, endoglucanase (CMCase) and xylanase activities, compared to the activities obtained using mono-cultures. Similarly, higher FP cellulase, β-glucosidase, CMCase and xylanase activities of 35.8 IU/gds (96 h), 33.71 IU/gds (96 h), 131.34 IU/gds (120 h) and 3106.34 IU/gds (120 h) were achieved in the tray fermentation using rice straw with wheat bran in the ratio of 3:2. Results of present investigation showed that higher cellulase activity and an optimal combination of cellulase and β-glucosidase can be achieved through mixed-culture SSF in trays. The approach of utilizing negative cost agricultural wastes through tray fermentation for cellulase and hemicellulase production is expected to serve the objectives of: (a) management of wastes which would otherwise cause environmental pollution problems; (b) production of hydrolytic enzymes at low cost and; (c) simple technique requiring no sophisticated instruments with practical applications.     

Effects of wheat bran with different colors on the qualities of dry noodles

White, blue, black and purple red wheat bran powders were prepared by ultrafine grinding to the particle size distribution of 0.5–100 μm. The effects of wheat bran addition on the qualities of dry Chinese noodles were investigated. Rapid Visco Analyzer results suggested that peak viscosity, hot paste viscosity, cool paste viscosity, breakdown viscosity and setback viscosity of the blends decreased with the increasing bran levels from 2.0% to 6.0% (P < 0.05). Color of dough sheet (L*) decreased with the addition of wheat bran, while a* and b* values increased distinctly. Water absorption and firmness of the cooked noodles showed up trends with increasing addition of bran, while cooking loss showed a downtrend. Tensile strength and elongation rate decreased when bran addition was 2.0%, but increased when bran addition reached 4.0%–6.0%. Storage modulus (E′) and loss modulus (E″) showed decreasing trends with increases in bran addition at frequencies of 0.1–10 Hz. SEM revealed that bran presence could slightly decrease surface connectivity between starch granules and gluten. It is possible to produce fiber-rich noodles by using 2.0%–6.0% ultrafine-ground bran in wheat flour.     

Sourdough fermentation of wholemeal wheat bread increases solubility of arabinoxylan and protein and decreases postprandial glucose and insulin responses

Glycemic responses to most of the conventional breads are high, including breads made of wholemeal flour. Baking technology is known to affect these responses. The aim of the present study was to investigate effects of xylanase enzyme treatment and sourdough fermentation in wholemeal wheat bread baking on postprandial glucose and insulin responses and on in vitro protein digestibility. The wheat breads were made of 100% flour from peeled kernels by a straight dough or sourdough fermentation method, and with or without using xylanase during mixing of dough. Standard white wheat bread was used as a reference. All test bread portions contained 50 g available carbohydrate and were served in random order to eleven insulin resistant subjects. Blood samples for measuring glucose and insulin concentrations were drawn over 4 h. The sourdough wholemeal wheat bread resulted in the lowest postprandial glucose and insulin responses among the four tested breads (treatment × time; p = 0.000 and p = 0.022, respectively). There were differences in solubility and depolymerisation of protein and arabinoxylan among the breads but these did not fully explain the in vivo findings. In conclusion, the health effects of wholemeal wheat bread can be further improved by using sourdough process in breadmaking.     

Low moisture milling of wheat for quality testing of wholegrain flour

The objective of this study was to produce wholegrain wheat flour on a laboratory-scale with particle size distributions similar to commercially-milled samples without re-milling the bran. The moisture contents of four hard winter wheat cultivars were adjusted to 7.29–7.98% (by drying), 9.00–10.6% (“as is”), and 15.6% (by tempering) prior to milling into wholegrain flour. The moisture treatments appeared to affect the partitioning of wholegrain flour particles into each of three categories: fine (<600 μm), medium (600–849 μm) and coarse (≥850 μm). When the distributions of particles were grouped into these categories, wholegrain flours made from dried and “as is” wheat fell within the values for commercial wholegrain flours, while that from tempered wheat contained more coarse particles than even the coarsest commercial wholegrain flour. Loaf volumes and crumb firmness were not significantly different between bread made from wholegrain flour that had been produced from dried or “as is” wheat, but loaf volume was significantly lower and bread crumb firmness was significantly higher when wholegrain flour from tempered wheat was used. These results show that wheat may be milled without tempering to produce wholegrain flour with particle size similar to some commercially-milled flours without needing to re-grind the bran.     

Modification of the rheological behavior of amaranth (Amaranthus hypochondriacus) dough

For people with celiac disease, a lifelong abdication of gluten including-products is necessary to live a life without celiac affected reactions. The production of high-quality bread from gluten free flour is not simple in comparison to gluten including flours such as those derived from wheat (Triticum spp.). The gas binding and crumb structure forming capacity are very low in gluten free batters. They can efficiently be analyzed through the rheological properties of the dough used. The use of acidification in amaranth (Amaranthus hypochondriacus) dough preparation is a possible means of changing the rheological behavior of amaranth in the desired direction. Methods include the use of lactic acid directly, or the fermentation via lactic acid bacteria. Adding up to 20 mL lactic acid/kg flour in amaranth dough preparation led, during oscillation tests, to an increase of the complex shear modulus up to 30% in the range of 0.1 up to 10 Hz. The use of sourdough fermentation decreased the complex shear modulus in the same test up to nearly 60%. In creep recovery tests, the elastic part of amaranth dough decreased from 65.4% without any treatment down to 63.9% by the addition of up to 20 mL lactic acid/kg flour. Sourdough fermentation by Lactobacillus plantarum was able to decrease it to 54%. The acidification showed a significant positive influence on the rheological parameters of amaranth dough only at the higher stress level. In contrast, sourdough fermentation was able to produce doughs with viscosity and elasticity similar to that found in pure wheat flours.     

Evaluation of sorghum flour as extender in plywood adhesives for sprayline coaters or foam extrusion

This study was conducted to evaluate sorghum flour as protein extender in phenol-formaldehyde-based plywood adhesive for sprayline coaters or foam extrusion. Defatted sorghum flour, containing 0.2% (db) residual oil and 12.0% (db) crude protein, was analyzed for solubility and foaming properties. Sorghum flour proteins were least soluble (≤12%) under acidic pH, most soluble (72%) at pH 10, and produced substantial and highly stable foam at pH 10. Sorghum flour was substituted (on protein content basis) for wheat flour in the standard glue mix. Mixing properties and bond strength of the sorghum-based glue were compared with those of the industry standard glue. The sorghum flour-based adhesive had mixing properties and appearance that were superior to those of the standard wheat flour-based plywood glue, but its viscosity and bond strength were markedly less. Doubling the amount of protein contributed by sorghum flour in the glue mix markedly improved both viscosity (1104 cP) and adhesion strength (1.37 MPa) of the sorghum-based plywood glue to acceptable levels. The modified sorghum flour-based plywood glue also produced foam that remained stable up to 3 h. These results demonstrated that sorghum flour is a viable extender in plywood glues for sprayline coater or foam extrusion.     

Optimisation of a solvent for the complete extraction of prolamins from heated foods

Wheat bread was lyophilised, ground, extracted and centrifuged. The supernatants were analysed for gluten content by RP-HPLC and a commercial sandwich ELISA. Prolamin extraction solvents contained tris(2-carboxyethyl)phosphine (TCEP; 1, 2, 5, 10, 20, 50 mmol/L), guanidine hydrochloride (GUA; 0 or 2 mol/L) and a buffered salt solution. A commercial cocktail solution (250 mmol/L mercaptoethanol (ME), 2 mol/L GUA, buffered salt solution) as well as 60% (v/v) ethanol were used as control solvents. Wheat flour was the control for the extractability of the native prolamins. 60% ethanol only extracted 37% of the prolamins from wheat bread (cocktail = 100%). When ME was replaced by TCEP the protein yield increased from 35% at the lowest TCEP-level to 95% when 20–50 mmol/L TCEP were used. The use of GUA was essential to extract prolamins quantitatively. Comparative protein analysis using RP-HPLC and ELISA showed that both methods provided comparable prolamin (gliadin) concentrations of the wheat flour (40.3–45.7 mg/g), when 60% ethanol was used as extraction solvent. The extraction yields from bread were considerably lower (16.7–24.7 mg/g). Cocktail and TCEP extracted almost the same amount of protein from flour and bread with TCEP showing slightly lower yields. Total extractable protein (gliadin + glutenin) as determined by RP-HPLC was 70.5–75.3 mg/g, and total gliadin as determined by ELISA was 42.7–44.2 mg/g. Thus, the study has shown that TCEP in combination with GUA extracts proteins from heated, gluten-containing foods as effective as the commercial cocktail solution.