Exploring the interactions between blackcurrant polyphenols, pectin and wheat biopolymers in model breads; a FTIR and HPLC investigation

This study explores the interactions between added blackcurrant polyphenols (PPs) and pectin, as well as different bread components in model bread systems. A series of model breads containing flour, yeast, sugar, salt, oil and water, with/without added pectin and blackcurrant PP extract, were prepared and characterised. Results show that adding PPs in addition to pectin increased the total extractable PP content and antioxidant activity of the breads, and decreased the proportion of unextractable high molecular weight proteins (detected by size exclusion-HPLC). The composition of bread formulations influences the amount of anthocyanins, especially delphinidin-3-o-glucoside and delphinidin-3-o-rutinoside, which are retained after bread baking. Replacing flour with starch and gluten, adding blackcurrant PP extract and pectin, or removing bread components (oil, salt or the mixture of yeast and sugar), caused changes in the bread gluten conformations related to Amide I and II bands (revealed by FTIR), as well as the extractability of PPs and proteins (revealed by HPLC).     

Application of FT-IR and Raman spectroscopy for the study of biopolymers in breads fortified with fibre and polyphenols

Adding dietary fibres (DFs) and polyphenols (PPs) to bread is a convenient way to deliver the health benefits of DFs and PPs to consumers. In this study, we investigate the interactions among added pectin polysaccharides, PPs and bread components such as wheat proteins in different bread formulations. Two sets of breads with a 20% difference in the water content were prepared in the absence (Control), or presence of pectin and/or fruit PP extracts (Treated). Results show that adding pectin and PPs caused changes in the molecular conformations and polymer structure of wheat gluten and starch in the finished breads, especially in the secondary protein conformation (Amides I and II, as revealed by FTIR Spectroscopy). An increase of water content during dough formulation also affected secondary protein conformation. The Treated breads gained β-sheets in the protein's secondary conformation at the expense of β-turns, and contained more un-ordered conformations especially in the presence of berry PPs. These results were confirmed by complementary Raman spectroscopic measurements. Both hydrophobic and H bonding interactions occurred among bread components and the added PPs and pectin, which affected PP stability during breadmaking and the total extractable PP content of finished breads. Schematic Loop and Train models for breads enhanced with PPs and pectin are proposed that illustrate the possible conformational changes in wheat protein structure due to the presence of added PPs and pectin.     

Physicochemical properties of bread dough and finished bread with added pectin fiber and phenolic antioxidants

Comparative studies were conducted in this paper to investigate the effects of added dietary fiber (DF) and/or phenolic antioxidants on the properties of bread dough and finished bread. Breads were developed in the absence (control bread), or presence of apple pectin and/or fruit phenolic extracts (treated breads), and subjected to quality evaluation (attributes including color, weight, and volume) and characterization of chemical and rheological properties. Chemical analyses revealed that breads with added phenolic extracts had greater antioxidant activity and higher extractable phenolic content, than control bread and the treated breads with added apple pectin(s). The measured antioxidant activity was mainly derived from the phenolics present in bread. Storage modulus G' (elasticity) and loss modulus G″ (viscocity) of the treated bread dough with added pectin(s) only were higher than those of control dough. The G' or G″ of the treated breads incorporated with a combination of a pectin and fruit phenolic extract depended on the type of phenolic extract (that is, apple and blackcurrant extracts behaved differently from kiwifruit extract). The G' and G″ at the final baking step were higher than those of other stages, indicating an increase in cross-linking among polymeric molecules and bread particles of high molecular weight. We conclude that the added pectin and/or phenolic extract had influenced bread dough cross-linking microstructure and bread properties through being involved in the interactions with bread components such as wheat proteins during dough development and bread baking. PRACTICAL APPLICATION: Dietary fibers and phytochemicals (including phenolic antioxidants) have long been recognized as the active nutrients responsible for the health benefits of fruit and vegetables to humans. Interest in incorporating bioactive ingredients such as dietary fiber and phenolic antioxidants into popular foods like bread has grown rapidly, due to the increased consumer health awareness. The added bioactive ingredients may or may not promote the development of bread dough. This paper reports the findings associated with the properties of the functional breads enhanced with apple pectin and apple, blackcurrant, and kiwifruit phenolic extracts. Results of this paper indicate that the success of the development of such functional breads is ultimately determined by the interactions among added bioactive ingredients and other bread components.     

Structure and Dynamics of Wheat Starch in Breads Fortified with Polyphenols and Pectin: an ESEM and Solid-State CP/MAS 13C NMR Spectroscopic Study

Two sets of breads formulated with a 20% difference in water quantity in the absence (control bread), or presence (fortified bread) of high methoxyl pectin (HM) and an apple, kiwifruit, or blackcurrant polyphenol (PP) extract (APE, KPE or BPE) were examined by Environmental Scanning Electron Microscopy (ESEM) and Cross Polarization/Magic Angle Spinning ¹³C NMR Spectroscopy. ESEM revealed that all the bread doughs had similar microstructures, comprising starch granules and yeast cells embedded in a continuous gluten matrix. However, the microstructure of the finished breads differed. NMR studies revealed differences in amylopectin-related crystalline domains and the amylose-related amorphous domains among the breads. All the breads showed V-type or amorphous starch structures by NMR, and the control bread may also contain some A-type starch. Breads formulated with 20% extra water showed a greater degree of starch gelatinization, a smoother crumb microstructure, and a lower amorphous starch content. It is feasible to incorporate PPs and pectin in breads at reasonably high concentrations.     

Effects of Adding Apple Polyphenols Before and After Fermentation on the Properties of Drinking Yoghurt

Adding polyphenols (PPs) to yoghurt is a convenient way to deliver the health benefits of PPs and also the probiotic effects of starter cultures. In this study, drinking yoghurts with apple PPs (chlorogenic acid, phlorizin, or apple PP extract (APE)) added pre- or post-fermentation, and pectins (low or high methoxyl) were subjected to chemical, physical, and microbiological analyses. Results show that the type of PPs and pectin affected the total extractable PP content (TEPC), PP profiles, viscosity, storage modulus of yogurt, colony number, and morphology of the starter cultures. Adding APE before fermentation produced yoghurts with a greater TEPC and more polar PPs than adding post-fermentation. Producing drinking yoghurt enhanced with apple PPs via either approach is feasible. The pre-fermentation approach may be more beneficial in terms of increased TEPC and growth of starter culture, offering a bio-process to optimise PP profiles in drinking yoghurt.     

Usage of enzymes in a novel baking process

In this study, the effects of different enzymes (alpha-amylase, xylanase, lipase, protease) on quality of breads baked in different ovens (microwave, halogen lamp-microwave combination and conventional oven) were investigated. It was also aimed to reduce the quality problems of breads baked in microwave ovens with the usage of enzymes. As a control, bread dough containing no enzyme was used. Specific volume, firmness and color of the breads were measured as quality parameters. All of the enzymes were found to be effective in reducing the initial firmness and increasing the specific volume of breads baked in microwave and halogen lamp-microwave combination ovens. However, in conventional baking, the effects of enzymes on crumb firmness were seen mostly during storage. The color of protease enzyme added breads were found to be significantly different from that of the no enzyme and the other enzyme added breads in the case of all type of ovens.     

The use of normal and heat-treated barley flour and waxy barley starch as anti-staling agents in laboratory and industrial baking processes

Normal and heat-treated barley, both as flour and waxy starch, were added at a concentration of 3% to a white wheat bread. The effect not only of selected additives, but also of laboratory- and industrial baking processes on stalling was evaluated. Laboratory baked breads with heat-treated barley flour differed from control breads with regard to water content, firmness and amylopectin retrogradation. The influence of water content on firmness increased with storage time. All laboratory baked breads with barley additives, except normal barley flour, were less firm after 7 days of storage as compared to the control although amylopectin retrogradation tended to increase. Improved water absorption, and consequently, increased water content and/or different water binding capacities of the flour/starch could explain these results. Industrial baking caused higher water losses, especially in breads containing additives, thus reducing the effects on amylopectin retrogradation and firmness.     

USE OF APPLE POMACE AS A SOURCE OF DIETARY FIBER IN WHEAT BREAD

Chemical analysis of apple pomace revealed that it contains 29.4% neutral detergent fiber and 13.0% pectin. Pomace-flour blends were prepared by incorporating 2, 5, 8 and 11% pomace in wheat flour. Blends were evaluated for their bread making quality. Water absorption increased with the increase of pomace in the blends. Neutralizing the acidity of pomace blended dough did not change the water absorption significantly. As the percentage of pomace in blends increased from 0 to 11, a reduction of 42.8% in loaf volume was observed but neutralization of pomace acidity in dough resulted in only 26.6% reduction in volume under similar conditions. On the other hand loaf weight of the breads, prepared from blends with 11% pomace under unneutralized and neutralized conditions, increased by 7.0 and 3.1%, respectively. With increase of pomace percentage in blends up to 11, the bread firmness increased from 3N in control to 12 and 10N respectively, in unneutralized and neutralized pomace blended dough. Blending of pomace (0–11%) increased baking time from 20 min for control to 33 min for unneutralized and 27 min for neutralized blends. Sensory evaluation of the product revealed that breads containing up to 5% pomace were acceptable.     

Impact of thermostable amylases during bread making on wheat bread crumb structure and texture

Thermostable amylases [Bacillus subtilis α-amylase (BSuA) and B. stearothermophilus maltogenic amylase (BStA)] with different modes of action and impacts on firming properties were added during straight-dough bread making. BSuA continuously degraded the starch fraction during bread making. Its action resulted in larger gas cells than in control bread, but did not change initial firmness. In contrast to BSuA, BStA mainly degraded starch at the end of the baking phase and during bread cooling, which caused little if any impact on bread crumb texture. However, it led to higher initial firmness readings than for the control breads. Neither BSuA nor BStA were inactivated during bread making. The results evidence that starch properties have a large impact on bread crumb structure and initial firmness and are highly influenced by the mode of action of the enzyme.     

The impact of baking time and bread storage temperature on bread crumb properties

Two baking times (9 and 24 min) and storage temperatures (4 and 25 °C) were used to explore the impact of heat exposure during bread baking and subsequent storage on amylopectin retrogradation, water mobility, and bread crumb firming. Shorter baking resulted in less retrogradation, a less extended starch network and smaller changes in crumb firmness and elasticity. A lower storage temperature resulted in faster retrogradation, a more rigid starch network with more water inclusion and larger changes in crumb firmness and elasticity. Crumb to crust moisture migration was lower for breads baked shorter and stored at lower temperature, resulting in better plasticized biopolymer networks in crumb. Network stiffening, therefore, contributed less to crumb firmness. A negative relation was found between proton mobilities of water and biopolymers in the crumb gel network and crumb firmness. The slope of this linear function was indicative for the strength of the starch network.     

Enzymes Action on Wheat–Soy Dough Properties and Bread Quality

High levels of soy flour added to wheat bread produce negative effects on gluten network formation, dough properties, and on bread final quality. The objective of this study was to assess the influence of three enzymes, transglutaminase (TG), glucose oxidase (GOX), and endoxylanase (XYL), on dough properties and final quality of high-protein breads. The addition of TG and GOX increased the mixing stability and maximum resistance of dough, decreased its extensibility, and produced stronger and more consistent dough samples. XYL incorporation produced opposite results. XYL addition and the lowest GOX dose increased bread volume significantly and decreased initial crumb firmness, while high doses of TG (0.3%) produced detrimental effects on bread volume and crumb firmness. In conclusion, XYL and GOX 0.001% addition improved the final quality of soy-fortified breads, but XYL was the best additive to improve dough properties, bread volume, and quality.     

High-Amylose Resistant Starch as a Functional Ingredient in Breads: a Technological and Microstructural Approach

Resistant starches (RS) are important functional fibers with high potential for the development of healthy foods. The technological, nutritional, and commercial possibilities of introducing type 2 RS in white breads were studied. Four levels of maize RS (HM) as wheat flour replacement were evaluated: 0%, 10%, 20%, and 30% (control, HM10, HM20, and HM30, respectively). Thermal transitions experiments were assessed on doughs prior to breadmaking. The bread quality was studied by specific volume, color of crust and crumb, porosity, and texture of the crumb. The microstructure of the crumb was analyzed by environmental scanning electron microscopy (ESEM). Proximate composition and in vitro starch digestibility were performed to characterize the nutritional profile of breads and estimate the glycemic index (GI). Consumer acceptability of breads was also evaluated. Breads with HM showed great performance up to 20% replacement in the specific volume, the crumb porosity, and the texture. Replacement up to 30% caused major damage to those parameters. Differential scanning calorimetry runs demonstrated that HM starch did not gelatinize under the baking conditions, as confirmed by ESEM. The presence of increasing levels of native starch is thought to have the greatest influence on reducing the crust browning, increasing the crumblier texture and decreasing starch digestibility. With respect to the control, a high and progressive reduction in the estimated GI and an outstanding increase of fiber with increasing levels of HM were found. The sensory evaluation of HM20 bread showed that this level of substitution has great consumer acceptance, giving it the chance to become a healthy substitute of white bread.     

Preparation and use of apple skin polyphenol extracts in milk: enhancement of the viability and adhesion of probiotic Lactobacillus acidophilus (ATCC 1643) bacteria

This study explored the feasibility of using apple skin as a source for generating antioxidant extracts, that is ethanolic or aqueous apple skin polyphenol extract (ASPE) and examined the effects of such ASPEs and six purified polyphenols (PPs), that is rutin, epicatechin, phlorizin, cholorogenic acid, quercetin and p‐coumaric acid on the viability of probiotic bacteria (PB) Lactobacillus acidophilus in a PP‐enhanced milk drink at 4 °C and the in vitroPB adhesion to hydrophilic tissue culture microtitre plates (TCMPs) at 4 °C or 37 °C. The two ASPEs differed slightly in antioxidant activity, PP composition and total extracted PP, vitamin C and uronic acid contents. PB. had over 10× better viability in milk with added PPs than without over a 50‐day storage at 4 °C, while the aqueous extract was more effective than any of the pure PPs, except rutin. PB exhibited significantly greater potential adhesion to intestinal cells in the presence of the aqueous ASPE than the ethanolic ASPE or purified PP, while temperature (4 °C or 37 °C) had a negligible effect on adhesion. Use of apple skin as a source of PPs for enhancing PB functionality in dairy foods may offer a means of deriving value from this waste stream.     

Combinations of glucose oxidase, α‐amylase and xylanase affect dough properties and bread quality

The objective of this work was to study the effects of the combination of glucose oxidase (Gox), α‐amylase (AM) and xylanase (Xyl) on dough properties and bread quality, applying response surface analysis. Gox improved dough stickiness and bread crumb uniformity, but had a negative effect on specific volume. A positive synergist effect was observed combining Xyl and AM on specific volume and crumb firmness but this synergist effect was negative on crumb uniformity. Using the ‘desirability function’, two optimal formulations for the baking process were obtained. In the first optimisation, the combination of Gox 0.0026, Xyl 0.016 and AM 0.01 g per 100 g of flour will allow to obtain breads with high specific volume and low firmness. Second optimisation (Gox 0.0037, Xyl 0.0089 and AM 0.0105 g per 100 g of flour) will allow to obtain breads with 37% higher specific volume than control and, additionally, with low dough stickiness.     

Modification of gluten-free sorghum batter and bread using maize, potato, cassava or rice starch

Gluten-free sorghum bread was made from cassava, maize, potato or rice starch and sorghum in the ratios 10:90, 20:80, 30:70, 40:60 and 50:50. The other baking ingredients, on flour-weight-basis, were water (100%), sugar (6.7%), egg white powder (6%), fat (2%), salt (1.7%) and yeast (1.5%). Increasing starch content changed the batters’ consistencies from soft doughs to thin pourable batters. Increasing starch content decreased crumb firmness and chewiness, and increased cohesiveness, springiness and resilience of all breads. Cassava-sorghum and rice-sorghum breads had better crumb properties than maize-sorghum or potato-sorghum breads. Although the crumb properties of all breads declined (i.e. firmness and chewiness increased; cohesiveness, resilience and springiness decreased) on storage, the formulation containing 50% cassava starch retained the best overall texture.     

Modification of appetite by bread consumption: A systematic review of randomized controlled trials

The inclusion of different ingredients or the use of different baking technologies may modify the satiety response to bread, and aid in the control of food intake. The aim of this study was to perform a systematic search of randomized clinical trials on the effect of bread consumption on appetite ratings in humans. The search equation was (“Bread”[MeSH]) AND (“Satiation”[MeSH] OR “Satiety response”[MeSH]), and the filter “clinical trials.” As a result of this procedure, 37 publications were selected. The satiety response was considered as the primary outcome. The studies were classified as follows: breads differing in their flour composition, breads differing in ingredients other than flours, breads with added organic acids, or breads made using different baking technologies. In addition, we have revised the data related to the influence of bread on glycemic index, insulinemic index and postprandial gastrointestinal hormones responses. The inclusion of appropriate ingredients such as fiber, proteins, legumes, seaweeds and acids into breads and the use of specific technologies may result in the development of healthier breads that increase satiety and satiation, which may aid in the control of weight gain and benefit postprandial glycemia. However, more well-designed randomized control trials are required to reach final conclusions.     

Gluten-Free Bread Making Trials from Cassava (Manihot Esculenta Crantz) Flour and Sensory Evaluation of the Final Product

The aim of this work was to evaluate the effectiveness of the use of cassava flour in bread making, and the sensory acceptability of the final product. Different baking trials were carried out by using egg white and extra-virgin olive oil, in consideration of their high nutritional value with respect to other food additives (i.e., hydrocolloids). Significant (p < 0.05) improvements of loaf specific volume (from 2.24 to 3.93 mL/g) and crumb firmness (from 9.14 to 4.67 N) were achieved by contemporarily including egg white and extra-virgin olive oil in the formulation. Cassava breads containing both these ingredients obtained the best scores from panelists for all the test breads examined and resulted attractive as the wheat bread prepared as reference.     

Effect of Retrograded Waxy Corn Starch on Bread Staling

Waxy corn starch pastes (10%) were stored at 5 °C for up to 35 days, and the powder specimens of retrograded starches thus obtained were added to wheat flour for bread baking at a level of 5%. The effect of retrograded starch on the staling of bread was determined. The loaf which contained retrograded waxy corn starch, which was prepared by storing the 10% paste at 5 °C for 7 days, showed an increase in specific volume and the results of the sensory evaluation showed that it was very acceptable. During the storage of bread, the increase in firmness and decrease in degree of gelatinization were suppressed by adding retrograded waxy corn starch. The moisture content of bread crumbs did not relate to firmness. Added retrograded waxy corn starch decreased the final viscosity of flour. The crystalline region of retrograded waxy corn starch used for bread baking included longer chains from amylopectin which in raw starch occurred in the amorphous region.     

Investigations on the extractability of gluten proteins from wheat bread in comparison with flour

 Immunochemical methods are recommended for the quantitation of small amounts of gluten in food produced for those with coeliac disease. A major problem, however, is the reduced extractability of gliadin, the toxic factor of gluten, with aqueous alcohol, when foods have been heat-processed. A combined extraction/HPLC procedure was used to study the extractability of all gluten protein types from wheat flour and bread under both non-reducing and reducing conditions. Gliadin isolated from wheat flour was used as a reference protein for quantitation. The results indicate that the extractability of gliadin from bread with 60% ethanol under non-reducing conditions is strongly reduced. α- and γ-gliadins are much more affected than ω-gliadins, and less gliadin was extracted from the crust than from the crumb. For a complete extraction of gliadins from bread, reducing conditions and increased temperature are required. However, glutenin subunits are coextracted with the gliadins. This extract can be used for the quantitation of total gluten proteins by RP-HPLC. The recovery of gliadin added to flour before dough-mixing and bread-making is 98%. Received: 16 February 1998     

Investigations on the extractability of gluten proteins from wheat bread in comparison with flour

 Immunochemical methods are recommended for the quantitation of small amounts of gluten in food produced for those with coeliac disease. A major problem, however, is the reduced extractability of gliadin, the toxic factor of gluten, with aqueous alcohol, when foods have been heat-processed. A combined extraction/HPLC procedure was used to study the extractability of all gluten protein types from wheat flour and bread under both non-reducing and reducing conditions. Gliadin isolated from wheat flour was used as a reference protein for quantitation. The results indicate that the extractability of gliadin from bread with 60% ethanol under non-reducing conditions is strongly reduced. α- and γ-gliadins are much more affected than ω-gliadins, and less gliadin was extracted from the crust than from the crumb. For a complete extraction of gliadins from bread, reducing conditions and increased temperature are required. However, glutenin subunits are coextracted with the gliadins. This extract can be used for the quantitation of total gluten proteins by RP-HPLC. The recovery of gliadin added to flour before dough-mixing and bread-making is 98%. Received: 16 February 1998