Effects of pressure treatment of hydrated oat,finger millet and sorghum flours on the quality and nutritional properties of composite wheat breads

Breadmaking achievement using grains alternative to wheat and rye is a challenging task for cereal technologists, since most of the available innovative breads are characterised by poor crumb and crust characteristics, slight flavour and fast staling. To improve texture, mouth-feel, acceptability and shelf-life of breads prepared by using minor and/or under-utilised cereals, gluten and/or polymeric substances that mimic the viscoelastic properties of gluten, are required. Recent studies reported that high hydrostatic pressure (HP) treatment may represent an efficient non-thermal technique to promote the dough structure formation of composite cereal matrices. In the present study the effects of HP on the techno-functional and nutritional properties of oat-, millet-, and sorghum- based breads were evaluated compared to their unpressured- and gluten-added conventionally made counterparts. HP-treated (350 MPa, 10 min) wheat, oat, millet and sorghum batters were added to the bread recipe, replacing 50%, 60% and 40% of untreated wheat flour, respectively. Data from bread analyses revealed non significant physico-chemical impairment, and superior nutritional and sensory profiles in most quality features when HP treatment was applied to dough batters, compared with conventional/gluten-added samples. Specifically, HP breads deserved better sensory scores and exhibited higher antiradical activities despite a reduction in specific volume (wheat and oat) and faster staling kinetics (millet and sorghum) that were explicit in some composite samples.     

Biochemical and sensory evaluation of wheat bran supplemented sorghum bread

Addition of wheat bran to sorghum flour (Dabar cultivar) at two extraction rates 72% and 80% resulted in lowering reducing sugars. The percent decreasewas 75.6% compared with the control at the end of fermentation period. There was a highly significant (p 0.05) increase in crude fiber content as a result of addition of wheat bran. The increase was from 0.8 to 5.2 and from 0.5 to 5.3% for the 80% S/WB and 72% S/WB blends, respectively. Sorghum bread containing wheat bran was lower in reducing sugars and showed a significant increase (p 0.05) in starch content. Sorghum bread containing wheat bran resulted in a lower in vitro protein and starch digestibilities.     

Novel food and non-food uses for sorghum and millets

Sorghum and millets have considerable potential in foods and beverages. As they are gluten-free they are suitable for coeliacs. Sorghum is also a potentially important source of nutraceuticals such antioxidant phenolics and cholesterol-lowering waxes. Cakes, cookies, pasta, a parboiled rice-like product and snack foods have been successfully produced from sorghum and, in some cases, millets. Wheat-free sorghum or millet bread remains the main challenge. Additives such as native and pre-gelatinised starches, hydrocolloids, fat, egg and rye pentosans improve bread quality. However, specific volumes are lower than those for wheat bread or gluten-free breads based on pure starches, and in many cases, breads tend to stale faster. Lager and stout beers with sorghum are brewed commercially. Sorghum's high-starch gelatinisation temperature and low beta-amylase activity remain problems with regard to complete substitution of barley malt with sorghum malt . The role of the sorghum endosperm matrix protein and cell wall components in limiting extract is a research focus. Brewing with millets is still at an experimental stage. Sorghum could be important for bioethanol and other bio-industrial products. Bioethanol research has focused on improving the economics of the process through cultivar selection, method development for low-quality grain and pre-processing to recover valuable by-products. Potential by-products such as the kafirin prolamin proteins and the pericarp wax have potential as bioplastic films and coatings for foods, primarily due to their hydrophobicity.     

Novel food and non-food uses for sorghum and millets

Sorghum and millets have considerable potential in foods and beverages. As they are gluten-free they are suitable for coeliacs. Sorghum is also a potentially important source of nutraceuticals such antioxidant phenolics and cholesterol-lowering waxes. Cakes, cookies, pasta, a parboiled rice-like product and snack foods have been successfully produced from sorghum and, in some cases, millets. Wheat-free sorghum or millet bread remains the main challenge. Additives such as native and pre-gelatinised starches, hydrocolloids, fat, egg and rye pentosans improve bread quality. However, specific volumes are lower than those for wheat bread or gluten-free breads based on pure starches, and in many cases, breads tend to stale faster. Lager and stout beers with sorghum are brewed commercially. Sorghum's high-starch gelatinisation temperature and low beta-amylase activity remain problems with regard to complete substitution of barley malt with sorghum malt . The role of the sorghum endosperm matrix protein and cell wall components in limiting extract is a research focus. Brewing with millets is still at an experimental stage. Sorghum could be important for bioethanol and other bio-industrial products. Bioethanol research has focused on improving the economics of the process through cultivar selection, method development for low-quality grain and pre-processing to recover valuable by-products. Potential by-products such as the kafirin prolamin proteins and the pericarp wax have potential as bioplastic films and coatings for foods, primarily due to their hydrophobicity.     

Production of syrup rich in arabinoxylan oligomers and antioxidants from wheat bran by alkaline pretreatment and enzymatic hydrolysis,and applicability in baking

The target of this work was to develop a novel, industrially applicable process for simultaneously releasing different valuable components from wheat bran, including carbohydrates, oligomeric arabinoxylan and antioxidants. The process was based on alkaline pretreatment with potassium hydroxide (KOH) and subsequent enzymatic hydrolysis. Increasing KOH-dosage and thermal severity in pretreatment promoted carbohydrate solubilisation in hydrolysis, reaching glucose and arabinoxylan yields up to 86% and 76%, respectively. Release of antioxidants was particularly promoted by increasing KOH-dosage, while both the pretreatment severity and KOH-dosage promoted the release of oligomeric arabinoxylan in enzymatic hydrolysis. Two bran syrups, with or without KOH-treatment, were tested in bread making by substituting added sugar in the dough with bran syrup. The KOH-derived KCl also substituted 30% of NaCl in the bread formulation. The addition of bran syrup did not affect the baking properties of wheat bread dough. However, a decrease in bread flavour balance was observed with addition of syrup from KOH-pretreated bran. Conceptual level techno-economic assessment indicated that production of bran syrup would be economically feasible at a minimum selling price of 770 €/t and 1030 €/t with KOH-pretreatment and without KOH, respectively.     

Sorghum for human food – A review

A brief review of literature on sorghum for human foods and on the relationship among some kernel characteristics and food quality is presented. The chief foods prepared with sorghum, such as tortilla, porridge, couscous and baked goods are described. Tortillas, prepared with 75% of whole sorghum and 25% of yellow maize, are better than those prepared with whole sorghum alone. A porridge formulation with a 30:40:30 mix of sorghum, maize and cassava respectively, has been shown to be the most acceptable combination. The cooked porridge Aceda has lower protein digestibility and higher biological value than the uncooked porridge Aceda. Sorghum is not considered breadmaking flour but the addition of 30% sorghum flour to wheat flour of 72% extraction rate produces a bread, evaluated as good to excellent.     

Changes in micro- and macronutrient composition of pearl millet and white sorghum during in field versus laboratory decortication

Traditional decortication of pearl millet and white sorghum by hand pounding or using a mechanical device were performed in Burkina Faso, and compared to abrasive decortication in the laboratory using the same kernel lots. Using some nutrients as histological markers, the decortication characteristics and nutritional composition (iron, zinc, phytates, lipids, ADF fibres and starch) of decorticated grains were measured. Decortication had numerous effects on grain composition but no significant differences were observed between the two traditional methods of decortication. The effects varied according to the type of grain mainly due to the fact that more germ was removed in sorghum than in millet, as the millet germ is more embedded in the endosperm. During abrasive decortication, zinc and lipid losses increased rapidly due to removal of the germ, particularly in sorghum. Phytates were shown to be located mainly in the bran and germ but also in the endosperm in millet. In both sorghum and millet, half the iron was removed when only 10% of grain DM was abraded. The method of decortication, shock or friction vs. abrasion, influenced the fractions removed and thus the chemical composition of the decorticated kernels.     

Key issues and challenges in whole wheat flour milling and storage

Whole wheat flour is increasingly popular as research continues to reveal the benefits of whole grains and the food industry offers more whole grain options for consumers. The purpose of this review is to address milling and shelf-life issues that are unique to whole wheat flour. No standard methods are available for whole wheat flour milling, resulting in very different bran particle sizes. Literature suggests that moderate bran particle size is the best for bread production, while small particle size is better for non-gluten applications. Shelf-life of whole wheat flour is shorter compared to white flour due to the presence of lipids and lipid-degrading enzymes. Lipolytic degradation leads to reduction in functionality, palatability and nutritional properties. Strategies to stabilize whole wheat flour have focused on controlling lipolytic enzyme activity and have marginally succeeded.     

Grain of high digestible,high lysine (HDHL) sorghum contains kafirins which enhance the protein network of composite dough and bread

The aim of this study was to determine whether protein body-free kafirins in high digestibility, high-lysine (HDHL) sorghum flour can participate as viscoelastic proteins in sorghum-wheat composite dough and bread. Dough extensibility tests revealed that maximum resistance to extension (g) and time to dough breakage (sec) at 35 °C for HDHL sorghum-wheat composite doughs were substantially greater (p < 0.01) than for normal sorghum-wheat composite doughs at 30 and 60% substitution levels. Functional changes in HDHL kafirin occurred upon exceeding its T_g. Normal sorghum showed a clear decrease in strain hardening at 60% substitution, whereas HDHL sorghum maintained a level similar to wheat dough. Significantly higher loaf volumes resulted for HDHL sorghum-wheat composites compared to normal sorghum-wheat composites at substitution levels above 30% and up to 56%, with the largest difference at 42%. HDHL sorghum-wheat composite bread exhibited lower hardness values, lower compressibility and higher springiness than normal sorghum-wheat composite bread. Finally, HDHL sorghum flour mixed with 18% vital wheat gluten produced viscoelastic dough while normal sorghum did not. These results clearly show that kafirin in HDHL sorghum flour contributes to the formation of an improved protein network with viscoelastic properties that leads to better quality composite doughs and breads.     

Effect of steam explosion on enzymatic hydrolysis and baking quality of wheat bran

In this study, the effect of steam explosion (SE) treatment on microstructure, enzymatic hydrolysis and baking quality of wheat bran was investigated. Coarse and fine bran were treated at different steam temperatures (120–160 °C) and residence times (5 or 10 min) and then hydrolysed with carbohydrase enzymes. The SE treatment increased water extractable arabinoxylan (WEAX) content from 0.75 to 2.06% and reducing sugars from 0.92 to 2.41% for fine bran. The effect was more pronounced with increased SE temperature and residence time. The highest carbohydrate solubilisation was observed in fine bran at SE treatment of 160 °C, 5 min. WEAX content increased to 3.13% when this bran was incubated without enzyme, while WEAX content increased to 9.14% with enzyme addition. Microscopic analysis indicated that cell wall structure of wheat bran was disrupted by severe SE conditions. Supplementation of SE treated (150 °C, 10 min) bran at 20% replacement level decreased the baking quality of bread. However SE followed by enzymatic hydrolysis increased specific volume and decreased crumb hardness (on the day of baking and after three days of storage). Phytic acid content of bread supplemented with SE treated bran was lower than the one supplemented with untreated bran.     

Development of β-glucan enriched wheat bread using soluble oat fiber

Soluble oat fiber (SOF) containing 70% oat β-glucan was incorporated into wheat bread by replacing 10, 12, and 14% of flour in wheat bread formulas. At each level of SOF, bread was made at the farinograph water content defined by the amount of water required to develop a dough consistency of 500 Brabender Units in farinograph tests, and 10 and 20% extra water above the farinograph water content. At the farinograph water content, bread formulated at each level of SOF exhibited lower specific volume and porosity, darker color, higher hardness, and lower springiness and cohesiveness than the control white bread. These negative effects were effectively counteracted by optimizing the water content in bread formulas. For the three levels of bran addition, when the water content was increased by 20% above the farinograph water content, the obtained loaves exhibited similar loaf volume, microstructure, textural properties, and crumb porosity to the control white bread. A serving (28 g) of the developed bread contained respectively 0.95, 1.12, and 1.28 g of β-glucan, which substantially exceed the minimum standard for approved health claims.     

The effect of infrared stabilized rice bran substitution on physicochemical and sensory properties of pan breads: Part I

Infrared stabilized rice bran (SRB) substitution to white wheat, wheat bran and whole grain wheat breads at the levels of 2.5, 5.0 and 10.0% was evaluated in terms of proximate composition, crumb color, dietary fiber, texture and sensory attributes. An increasing tendency was observed in crude fat and ash content of the breads. Redness (+a*), yellowness (+b*) chroma and redness (a*/b*) values were increased gradually with the addition of SRB. Crumb color was found to be darker when 10% of SRB was added to the breads. SRB inclusion did not affect the content of soluble dietary fiber while it significantly increased the insoluble and total dietary fiber contents of the breads (p < 0.05). In general, whole grain wheat bread differed from the other bread types in terms of textural behavior. Based on the overall acceptability scores, white wheat and wheat bran breads were sensory accepted up to 10% of flour replacement with rice bran, while substitution levels higher than 2.5% negatively affected the sensory scores of whole grain wheat bread.     

Whole wheat bread: Effect of bran fractions on dough and end-product quality

Consumption of whole-wheat based products is encouraged due to their important nutritional elements that benefit human health. However, the use of whole-wheat flour is limited because of the poor processing and end-product quality. Bran was postulated as the major problem in whole wheat breadmaking. In this study, four major bran components including lipids, extractable phenolics (EP), hydrolysable phenolics (HP), and fiber were evaluated for their specific functionality in flour, dough and bread baking. The experiment was done by reconstitution approach using the 2⁴ factorial experimental layout. Fiber was identified as a main component to have highly significant (P < 0.05) and negative influence on most breadmaking characteristics. Although HP had positive effect on farinograph stability, it was identified as another main factor that negatively impacted the oven spring and bread loaf volume. Bran oil and EP seemed to be detrimental to most breadmaking characteristics. Overall, statistical analysis indicates that influence of the four bran components are highly complex. The bran components demonstrate multi-way interactions in regards to their influence on dough and bread-making characteristics. Particularly, Fiber appeared to have a high degree of interaction with other bran components and notably influenced the functionality of those components in whole wheat bread-making.     

国内外高粱深加工研究现状与发展前景

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Effect of barley and oat flour types and sourdoughs on dough rheology and bread quality of composite wheat bread

The potential of sourdough to improve bread quality of barley and oat enriched wheat breads may depend on the characteristics of the added flour (cereal type, variety, extraction rate). We compared the effect of different barley flours and oat bran (substitution level 40%), unfermented and as sourdoughs (20% of total flour), on composite wheat dough and bread characteristics by combining empirical rheological analyses (DoughLab, SMS/Kieffer Dough and Gluten Extensibility Rig) with small-scale baking of hearth loaves. Whole grain barley flour sourdough increased resistance to extension (Rmax) of the dough and improved the form ratio of hearth loaves compared to unfermented whole grain barley flour. However, sourdough showed little effect on the breads prepared with sifted barley flour or oat bran. The breads made with oat bran showed highest bread volume, lowest crumb firmness and highest β-glucan calcofluor weight average molecular weight (MW). The heat treatment of oat bran inactivated endogenous enzymes resulting in less β-glucan degradation. High MW β-glucans will increase the viscosity of the doughs water phase, which in turn may stabilise gas cells and may therefore be the reason for the higher bread volume of the oat bran breads observed in our study.     

Storage stability,micronisation, and application of nutrient-dense fraction of proso millet bran in gluten-free bread

This study aimed to valorise the underutilised by-product of proso millet decortication. Millet bran was sieved into three fractions with substantially different nutritional profile. The fraction with diameter <500 μm had the highest nutrient density (14% protein, 26% starch, 36% dietary fibre, 9% fat, and 3 mg GAE/g phenolics (d.w.)) and was analysed for oxidative stability, micronisation effect under cryogenic or ambient conditions (2, 4, 8, 12 min), and baking applicability. The bran was oxidatively stable under refrigerator conditions for 150 days. Micronisation slightly increased the antioxidant activity measured by FRAP and ABTS assays as well as the content of fibre soluble in water and 78% ethanol as the bran particle size decreased from 171 μm to 26–46 μm. Gluten-free bread containing 10% of the nutrient-dense fraction of millet bran had higher dietary fibre (76%) and phenolics content (117%), improved volume and crumb softness, regardless of the bran particle size (diameter of 50th percentile 171 vs. 26 μm).     

Effect of hydrothermaled bran on physicochemical, rheological and microstructural characteristics of Sangak bread

Increased consumption of whole grain products has been associated with decreased risk of health problems such as cardiovascular disease, diabetes and obesity. Phytate however, has always been a matter of concern, since it chelates minerals such as iron. Sangak is very popular Iranian flat bread invented five hundred years ago, made from 95% extraction flour. The bread is fermented but usually fermentation is not able to remove all phytate from the dough. In this study flours were first debranned; resulting bran was subjected to a hydrothermal process. The hydrothermaled (HT) brans were then incorporated in the Sangak flour. In the next step, physicochemical, rheological and microstructural characteristics of Sangak flour and dough prepared from two Iranian wheat varieties, Tajan and Back Cross of Roshan were investigated. Results indicated a reduction in phytate up to 55% in the samples. The resulting dough containing HT bran showed a higher development time and valorimetric value and was more stable than doughs made with normal bran. Dough made with HT bran showed a kind of protein matrix in which proteins and starch granules are oriented in a more non-ordered structure.     

The apparent digestibility of energy,nitrogen and fibre and the biological value of protein in low- and high-fibre wheat breads

Sixteen 15 kg liveweight entire-male pigs were given either a low-fibre (1.21 g/100 g Neutral detergent fibre, NDF) or a high-fibre (6.38 g 100 g, NDF) wheat bread as their sole source of dietary protein, in a conventional 21-day metabolism study. A glucose/oil supplement which was assumed to be completely absorbed was given with the bread to ensure a high ratio of dietary energy to protein, to allow measurement of biological value (BV). The apparent faecal digestibility of gross energy was significantly (p<0.001) lower (7.4% units) for pigs given the high-fibre bread as was the apparent digestibility of NDF (24% units lower). The apparent faecal digestibility of total nitrogen was also significantly (p<0.001) lower for the animals fed the high-fibre bread, but there were no significant differences between the breads for the BV of their protein. The overall mean BV for the breads was 46%. The results indicate a significantly lower digestibility of nutrients and gross energy in breads containing appreciable quantities of wheat bran fibre.     

Nutritional components and antioxidant properties of seven kinds of cereals fermented by the basidiomycete Agaricus blazei

The aim of this work was to evaluate the effects of solid-state fermentation (SSF) by basidiomycete Agaricus blazei Murrill (ABM) on the nutritional components and antioxidant properties of wheat, rice, oat, corn, millet, broomcorn millet and sorghum.The results showed that the contents of nutritional components in the fermented cereals varied with the fermentation time. After SSF of ABM, the enhancement rates of millet in total phenols, amino acid nitrogen and water-soluble protein content were the highest, which were respectively 4.03, 12.04 and 10.37 times higher than that of the control; the enhancement rates of wheat in total protein and reducing sugar content were the highest, which were 0.32 and 100.77 times higher than that of control. According to 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity, reducing power, ferrous ion chelating ability and superoxide anion radical scavenging ability of ethanolic extracts from the fermented cereals, it was shown that the antioxidant properties of the cereals were significantly stronger than that of control after fermented by ABM. The improvement degrees of sorghum in DPPH radical scavenging capacity and superoxide anion radical scavenging ability were the highest, the improvement degrees of wheat in reducing power and ferrous ion chelating ability were the highest.     

Distributions of phenolic compounds,yellow pigments and oxidative enzymes in wheat grains and their relation to antioxidant capacity of bran and debranned flour

In this study, the distribution of phenolic compounds and yellow pigments in wheat grains and their relation to the total antioxidant capacity of bran and debranned flour was investigated. Yellow pigments, the activity of lipoxygenase (LOX) and peroxidase (POX) enzymes were also determined. The bran fraction was found to contain significantly higher concentrations of phenolic acids, flavonoids and yellow pigments. The LOX activity was concentrated in endosperm and embryo, while the POX activity mostly concentrated in the bran fraction. The results suggest that the bran fraction of wheat would potentially provide naturally occurring antioxidants. From the health benefit point of view, a small level of bran incorporation to bread can be recommended to increase dietary fibre and phytonutrients in the diet.