Effect of technological process on the nutritional quality of naked barley enriched rye bread

Naked barley products used in bread making gain popularity as a source of both soluble and insoluble fractions of dietary fibre, especially β-glucans. The aim of the study was to investigate the effects of different naked barley flour share in rye bread formulations and dough preparation methods (Single-phase and Detmold sourdough) on non-starch polysaccharides content and solubility and antioxidant properties of products at different processing stage. Naked barley incorporation to rye contributed to the increase in dietary fibre content with higher soluble fraction share, highly enriched products in β-glucan and increased antioxidant activity of products. It also contains high amounts of arabinoxylans, but less soluble than those from rye. A Single Phase method of rye bread production resulted in higher β-glucan concentration in products and their antioxidant activity, compared to Detmold method products. The nutritional quality of bread is highly influenced by the process parameters.     

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.     

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.     

Wheat Bread Quality as Influenced by the Substitution of Waxy and Regular Barley Flours in Their Native and Extruded Forms

The substitution of wheat flour with barley flour (i.e. native or pretreated/extruded) reduced the loaf volume. Depending on the barley variety and flour pretreatments, the colour and firmness/texture of the bread loaves were altered. Amongst the barley breads prepared from native flours (at 15% barley flour substitution level), Phoenix had higher loaf volume and lower crumb firmness than Candle. However, amongst the barley breads prepared from extruded flours, CDC-Candle had higher loaf volume and lower crumb firmness than Phoenix. The lower loaf volume and firmer crumb texture of barley breads as compared with wheat bread may be attributed to gluten dilution. Also, the physicochemical properties of barley flour components, especially that of β-glucan, can affect bread volume and texture. β-glucan in barley flour, when added to wheat flour during bread making, could tightly bind to appreciable amounts of water in the dough, suppressing the availability of water for the development of the gluten network. An underdeveloped gluten network can lead to reduced loaf volume and increased bread firmness. Furthermore, in yeast leavened bread systems, in addition to CO₂, steam is an important leavening agent. Due to its high affinity for water, β-glucan could suppress the amount of steam generated, resulting in reduced loaf volume and greater firmness. In the present study, breads made with 15% HTHM CDC-Candle flour had highly acceptable properties (loaf volume, firmness and colour) and it indicated that the use of extruded barley flours would be an effective way to increase the dietary fibre content of barley breads.     

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).     

Effect of immature wheat flour on nutritional and technological quality of sourdough bread

In this study, the effect of immature wheat flour (IWF) on the fermentation activity of lactic acid bacteria (LAB) and on the nutritional quality properties of bread were evaluated. IWF was added in the as the ratio of 10g/100g in sourdough fermentation medium, and the fermentation activity (total LAB, pH, titration acidity (TA), and total reducing sugar (TRS)) of LAB cultures was monitored. Additionally, some physical quality characteristics (specific volume, texture profile and colour value), estimated glycaemic index (eGI), rapidly digestible starch (RDS), slowly digestible starch (SDS), and the total dietary fibre content of sourdough bread were determined. According to the statistical test, it was revealed that the IWF addition stimulated LAB growth and increased their fermentation activity. The pH of the fermentation medium decreased from 6.57 to 3.50, and TA raised from 0.13% to 1.2% in 48 h. The highest TRS content was determined in IWF enriched sourdough samples, and as a result of this, the eGI of sourdough bread increased. Compared to the control sample, the SDS and total dietary fibre content were higher in IWF added sourdough bread, and a positive correlation was noted between these two components. IWF utilisation of sourdough bread formulation increased the hardness value by nearly 50%.     

Production of ß-glucan enriched flour from waxy barley

Starch (total, amylose and amylopectin), β-glucans (total, soluble and insoluble) and pasting properties of waxy and normal barley genotypes were assessed. Waxy genotypes showed higher β-glucans content, lower starch amount and higher viscosity than normal genotypes. The USA2 waxy genotype characterized by higher β-glucans content, has been subjected to dehulling, pearling, and pin-milling and then to air classification to obtain an enriched flour that showed higher dietary fiber (23.4% d.w.) and β-glucans content (15.3% d.w.) The obtained enriched flour could be used for the production of functional foods (pasta, bread, biscuits etc) that satisfy the requirements of FDA and EU Regulation.     

Wholemeal wheat bread: A comparison of different breadmaking processes and fungal phytase addition

The effect of different breadmaking processes (conventional, frozen dough, frozen partially baked bread) and the effect of the storage period on the technological quality of fresh wholemeal wheat breads are investigated. In addition, the impact of the exogenous fungal phytase on the phytate content was also determined. Results showed that breadmaking technology significantly affected the quality parameters of wholemeal breads (specific volume, moisture content, crumb and crust colour, crumb texture profile analysis and crust flaking) and frozen storage affected to a different extent the quality of the loaves obtained from partially baked breads and those obtained from frozen dough, particularly crust flaking. Freezing and frozen storage of wholemeal bread in the presence of fungal phytase decreased significantly the phytate content in whole wheat breads. The combination of fungal phytase addition, breadmaking process and frozen storage could be advisable for overcoming the detrimental effect of bran on the mineral bioavailability.     

The influence of fermentation processes and cereal grains in wholegrain bread on reducing phytate content

Wholegrain bread is generally thought of as being more healthy than white bread due to it having a higher content of dietary fibre, vitamins (especially vitamin B and E) and many important minerals. However, wholegrain bread also contains high levels of phytate (myo-inositolhexakisphosphate, InsP-6) which may bind desirable nutrients, preventing their absorption in the gut and thereby reducing the nutritional value of the end product. In order to evaluate factors influencing phytate levels, the effects of fermentation and selected wholemeal flours from rye, oats and wheat were investigated. Phytate levels were assessed using a spectrophotometric assay based on the measurement of iron with 2,2′-bipyridine. Phytate decreased in freshly ground wholegrain flour dough during the fermentation process with time of fermentation being the most important factor. Fermentation temperature was found to make only a small difference to the process of phytate reduction. Since the potential benefits of wholemeal breads incorporating various grains (e.g. oats and rye) are increasingly evident, this research has important implications for human health.     

Stability of B-complex vitamins and dietary fiber during rye sourdough bread production

The stability of vitamers: thiamine, riboflavin, nicotinic acid, nicotinamide, pantothenic acid, pyridoxine and pyridoxal, as well as soluble and insoluble dietary fiber was studied in a rye sourdough bread process. The vitamer concentrations were measured in raw materials (rye flours, white and red rye malt, yeast) and the rye sourdough breads made from them by means of LC–MS and stable isotope dilution assay. The content of dietary fiber was determined using a standard enzymatic-gravimetric method. During baking, the concentration of vitamins decreased by 20–45% in the case of thiamine, 25–50% in the case of nicotinic acid, 45–65% in the case of pyridoxal in both breads, 50% in the case of riboflavin and 15% in the case of pyridoxine only in fine rye bread. In contrast, the content of nicotinamide increased during processing by ten fold, presumably due to microbial activity during sourdough fermentation. The ratio of soluble to insoluble dietary fiber increased during rye sourdough processing.     

Wheat Bread Quality as Influenced by the Substitution of Waxy and Regular Barley Flours in Their Native and Cooked Forms

The substitution of wheat flour with barley flours altered the bread loaf volume, colour and bread crumb firmness. These changes were found to be dependent on the barley cultivar, substitution level and flour treatment. In native form, Phoenix barley flour at 15% substitution produced breads with bigger loaf volume and softer crumb than Candle barley flour. However, when the barley flours were heat-treated (pan-cooked in excess water and then dried) before substitution, Candle barley flour produced better quality breads in terms of loaf volume, crumb firmness and crust colour than the Phoenix counterparts. The baking functionality of Candle flour was markedly improved when added after heat treatment.     

Improving the quality of nutrient-rich Teff (Eragrostis tef) breads by combination of enzymes in straight dough and sourdough breadmaking

The growing interest in the benefits of wholegrain products has resulted in the development of baked products incorporating less utilised and ancient grains such as, millet, quinoa, sorghum and teff. However, addition of wholegrains can have detrimental effects on textural and sensory bread product qualities.Enzymes can be utilised to improve breadmaking performance of wholegrain flours, which do not possess the same visco-elastic properties as refined wheat flour, in order to produce a healthy and consumer acceptable cereal product.The effects of Teff grain on dough and bread quality, selected nutritional properties and the impact of enzymes on physical, textural and sensory properties of straight dough and sourdough Teff breads were investigated.Teff breads were prepared with the replacement of white wheat flour with Teff flour at various levels (0%, 10%, 20%, and 30%) using straight dough and sourdough breadmaking. Different combinations of enzymes, including xylanase and amylase (X + A), amylase and glucose oxidase (A + GO), glucose oxidase and xylanase (GO + X), lipase and amylase (L + A) were used to improve the quality of the highest level Teff breads. A number of physical, textural and sensory properties of the finished products were studied. The nutritional value of breads was determined by measuring chemical composition for iron, total antioxidant capacity, protein, fibre and fat. The obtained results were used to estimates intakes of nutrients and to compare them with DRIs.The incorporation of Teff significantly (P < 0.05) improved dietary iron levels as 30% Teff breads contained more than double the amount of iron when compared to corresponding wheat bread (6 mg/100 g v 2 mg/100 g). Addition of Teff also significantly (P < 0.05) improved total antioxidant capacity from 1.4 mM TEAC/100 g to 2.4 mM TEAC/100 g. It was estimated that an average daily allowance of 200 g of Teff enriched bread would contribute to DRIs in the range of 42-81% for iron in females, 72-138% for iron in males; 38-39% for protein in males, 46-48% for protein in females; and 47-50% of fibre in adults.The major challenge was encountered in producing the highest level of Teff bread with good textural and sensory attributes. Increasing the level of Teff significantly (P < 0.05) increased dough development time, degree of softening, crumb firmness and bitter flavour whilst decreasing the dough stability, specific loaf volume and overall acceptability of the bread. Teff breads produced with the addition of enzyme combinations showed significant improvements (P < 0.05) in terms of loaf volume, crumb firmness, crumb structure, flavour and overall acceptability in both straight dough and sourdough breadmaking.     

The combined use of hull-less barley flour and xylanase as a strategy for wheat/hull-less barley flour breads with increased arabinoxylan and (1→3,1→4)-β-D-glucan levels

Bread-making with a composite flour (CF) consisting of 60% wheat flour (WF) and 40% hull-less barley flour, increased the total and soluble (1→3,1→4)-β-D-glucan and total arabinoxylan (AX) contents of dough and bread samples, but decreased the specific bread loaf volume. A xylanase insensitive to inhibition by Triticum aestivum L. xylanase inhibitor (TAXI) and xylanase inhibiting protein (XIP), increased loaf volume by 8.8 and 20.1% for WF and CF breads, respectively. Xylanase addition not only markedly improved loaf volume of CF bread, but also increased the soluble AX content of the WF and CF dough and bread samples because of conversion of water-unextractable AX into soluble AX. The xylanase had no impact on the extractability and molecular weight of (1→3,1→4)-β-D-glucan, but (1→3,1→4)-β-D-glucan was degraded during bread-making probably because of endogenous β-glucanase activity. Taken together, the results clearly show that the combined use of hull-less barley flour and a xylanase active during bread making, lead to palatable breads with high total and soluble AX and (1→3,1→4)-β-D-glucan contents. The sum of total AX and (1→3,1→4)-β-D-glucan was 1.70% for WF bread and 3.06% for CF bread, while the sum of soluble AX and (1→3,1→4)-β-D-glucan was 0.49 and 1.41% for control WF and CF xylanase supplemented breads, respectively.     

Solubilisation of Mixed Linkage (1→3), (1→4)β-D-glucans From Barley: Effects of Cooking and Digestion

The extractability behaviour of mixed linkage β-glucans from barley has been assessed during cooking and under different regimens used for fibre isolation. Whilst β-glucan extractability increased to around 50% during cooking, from around 30% in the raw flour, methods used for NSP isolation resulted in even greater extractability (>60%). Enzymic rather than chemical treatments were more important in accounting for the increased extractability. Endogenous proteases from the small intestine were shown to be capable of enhancing the extractability of the β-glucan to a level similar to that found in ileal effluent from patients fed an acute barley-based diet. This is consistent with the presence of mixed linkage β-glucans as proteoglycan complexes in barley. The extractability of β-glucans measuredin vivowas significantly higher (P<0·001) than that measured in the original barley but without protease treatment. Thus, not only do «unextractable» β-glucans from barley have the potential to behave as a source of soluble NSP but the fibre matrix can be modified during transit in the upper gut. Hence the amount of soluble fibre present during gut transit can differ significantly from that measured in foods. This has implications for assessing the mechanism(s) involved in determining the response to fibre in the diet. It is important to take account of modifications to the fibre matrix when assessing the dietary response to a fibre source.     

A Multistrategic Approach in the Development of Sourdough Bread Targeted Towards Blood Pressure Reduction

Rising prevalence of hypertension is pushing food industry towards the development of innovative food products with antihypertensive effects. The aim was to study the effect of reduced sodium content and 21 % addition of wholemeal wheat sourdough (produced by Lactobacillus brevis CECT 8183 and protease) on proximate composition, γ-aminobutyric acid (GABA) and peptide content of wheat bread. Angiotensin converting enzyme I (ACE) inhibitory and antioxidant activities were also evaluated. Sodium replacement by potassium salt did not affect chemical composition and biological activities of bread. In contrast, GABA and peptides <3 kDa contents in sourdough bread (SDB) were 7 and 3 times higher, respectively, than the observed in control. ACE inhibitory and antioxidant activities of the peptide fraction?<?3 kDa from SDB was 1.7 and 2.6-3.0 times higher than control. Therefore, the combination of reduced sodium content with enriched concentrations of bioactive compounds in bread making may provide interesting perspectives for development of innovative breads towards blood pressure reduction.

     

Presence of β-glucanase activity in wheat and dairy ingredients and use of organic salts as potential enzyme inhibitors

Depolymerization of mixed linkage cereal β-glucans has been observed during the mixing and fermentation of multigrain breads. To maintain the bioactivity of β-glucans in bread and other foods, control of β-glucanase activity during production is needed. β-Glucanase activity in wheat and dairy ingredients was determined by adding them to β-glucan solutions and following the change in the molecular weight of β-glucan at 50 °C for 60 min. The activities in six wheat and six dairy ingredients ranged from undetectable to a 98% reduction in molecular weight. Calcium propionate, potassium sorbate, and sodium benzoate are salts of organic acids commonly used as food preservatives. Low concentrations of these additives (0.1–1.0%) were found to have an inhibitory effect on the β-glucanases found in wheat flour and whey protein isolate. The depolymerization rate of β-glucan was reduced by up to 76% by the three additives.     

Presence of β-glucanase activity in wheat and dairy ingredients and use of organic salts as potential enzyme inhibitors

Depolymerization of mixed linkage cereal β-glucans has been observed during the mixing and fermentation of multigrain breads. To maintain the bioactivity of β-glucans in bread and other foods, control of β-glucanase activity during production is needed. β-Glucanase activity in wheat and dairy ingredients was determined by adding them to β-glucan solutions and following the change in the molecular weight of β-glucan at 50 °C for 60 min. The activities in six wheat and six dairy ingredients ranged from undetectable to a 98% reduction in molecular weight. Calcium propionate, potassium sorbate, and sodium benzoate are salts of organic acids commonly used as food preservatives. Low concentrations of these additives (0.1–1.0%) were found to have an inhibitory effect on the β-glucanases found in wheat flour and whey protein isolate. The depolymerization rate of β-glucan was reduced by up to 76% by the three additives.     

Effect of Barley and Barley Components on Rheological Properties of Wheat Dough

The effects of addition of whole barley and barley components (starch, β-glucans and arabinoxylans) on rheological properties of dough prepared from wheat flours with variable gluten quality (cv. Glenlea, extra-strong; cv. Katepwa, very strong; cv. AC Karma, strong; and cv. AC Reed, weak) were investigated in these studies using Mixograph and dynamic rheological measurements. Whole barley meal, starch and non-starch polysaccharides from hulless barley with variable starch characteristics (normal, high amylose, waxy, and zero amylose waxy) were tested. Upon addition of either β-glucans or arabinoxylans, significant increases in peak dough resistance, mixing stability, and work input were recorded in all flours. The addition of starch to various wheat flours reduced the strength of the respective flour-water doughs. The improvement of dough strength upon addition of waxy or zero amylose waxy barley meal was associated with the high content of total and soluble β-glucans present in barley samples. The addition of arabinoxylans or β-glucans increased the G′ of wheat doughs; arabinoxylans had a greater effect than β-glucans. Starch substantially decreased the elastic modulus of dough prepared from cv. Glenlea but waxy and high amylose starches increased the G′ of dough prepared from cv. AC Karma. A combination of the high amounts of non-starch polysaccharides and unusual starch characteristics in barley seems to balance the negative effects associated with gluten dilution brought about by addition of barley into wheat flour.     

Optimization of air classification for the production of β-glucan-enriched barley flours

Barley grains contain a relevant amount of soluble fibre (i.e. β-glucans) and can be used for production of foods with healthy functions. To produce barley flours enriched in β-glucans, grain micronization and air classification of the flour was used, and a method to predict the relationship between the yield of the enriched flour and its β-glucan content was developed. This method is based on a series of sortings of micronized flour, with a progressive increase in the yield of a selected fraction; a curve for β-glucan enrichment vs. yield can then be calculated. Thus, the most suitable combination of yield and β-glucan content can be chosen. We tested this approach on two hull-less barleys with different starch type, and obtained barley flour fractions with twice the β-glucan concentration that the grain had. Enriched flour fractions with 11.2 and 15.6% β-glucans were obtained from cultivars Priora (hull-less) and CDC Alamo (waxy, hull-less), respectively, with a good flour yield (about 30%). We suggest that our method can be adopted for finely tuning the enrichment process to meet the industry's needs.     

The combined use of hull-less barley flour and xylanase as a strategy for wheat/hull-less barley flour breads with increased arabinoxylan and (1→3,1→4)-β-D-glucan levels

Bread-making with a composite flour (CF) consisting of 60% wheat flour (WF) and 40% hull-less barley flour, increased the total and soluble (1→3,1→4)-β-D-glucan and total arabinoxylan (AX) contents of dough and bread samples, but decreased the specific bread loaf volume. A xylanase insensitive to inhibition by Triticum aestivum L. xylanase inhibitor (TAXI) and xylanase inhibiting protein (XIP), increased loaf volume by 8.8 and 20.1% for WF and CF breads, respectively. Xylanase addition not only markedly improved loaf volume of CF bread, but also increased the soluble AX content of the WF and CF dough and bread samples because of conversion of water-unextractable AX into soluble AX. The xylanase had no impact on the extractability and molecular weight of (1→3,1→4)-β-D-glucan, but (1→3,1→4)-β-D-glucan was degraded during bread-making probably because of endogenous β-glucanase activity. Taken together, the results clearly show that the combined use of hull-less barley flour and a xylanase active during bread making, lead to palatable breads with high total and soluble AX and (1→3,1→4)-β-D-glucan contents. The sum of total AX and (1→3,1→4)-β-D-glucan was 1.70% for WF bread and 3.06% for CF bread, while the sum of soluble AX and (1→3,1→4)-β-D-glucan was 0.49 and 1.41% for control WF and CF xylanase supplemented breads, respectively.