Application of Response Surface Methodology in the Development of Gluten‐Free Bread

The formulation of gluten‐free (GF) bread of high quality presents a formidable challenge as it is the gluten fraction of flour that is responsible for an extensible dough with good gas‐holding properties and baked bread with good crumb structure. As the use of wheat starch in GF formulations remains a controversial issue, naturally GF ingredients were utilized in this study. Response surface methodology was used to optimize a GF bread formulation primarily based on rice flour, potato starch, and skim milk powder. Hydroxypropylmethylcellulose (HPMC) and water were the predictor variables. Analyses of the treatments from the design were made 24 hr after baking. Specific volume and loaf height increased as water addition increased (P < 0.01). Crumb firmness decreased as water levels increased (P < 0.01). Significant interactions (P < 0.01) between HPMC and water were found for the number of cells/cm². The number of large cells (>4 mm²) decreased with increasing levels of HPMC and water. Optimal ingredient levels were determined from the data obtained. The optimized formulation contained 2.2% HPMC and 79% water flour/starch base (fsb) and measured responses compared favorably to predicted values. Shelf‐life analysis of the optimized formulation over seven days revealed that, as crumb firmness increased, crust firmness and crumb moisture decreased.     

Gluten‐Free Bread from Sorghum: Quality Differences Among Hybrids

Gluten‐free breadmaking quality of 10 sorghum flours was compared using (relative basis) decorticated sorghum flour (70), corn starch (30), water (105), salt (1.75), sugar (1), and dried yeast (2). Batter consistency was standardized by varying water levels to achieve the same force during extrusion. Crumb properties were evaluated by digital image analysis and texture profile analysis (TPA). Significant differences (P < 0.001) in crumb grain were found among the hybrids with mean cell area ranging from 1.3 to 3.3 mm² and total number of cells ranging from 13.5 to 27.8/cm². TPA hardness values of the crumb also varied significantly (P < 0.001). Based on significant correlations (P < 0.01), starch damage, influenced by kernel hardness, was identified as a key element for these differences. Breads differed little in volume, height, bake loss, and water activity. Investigation of added ingredients on bread quality was conducted using response surface methodology (RSM) with two sorghum hybrids of opposite quality. Addition of xanthan gum (0.3–1.2% flour weight basis [fwb]) and skim milk powder (1.2–4.8% fwb) and varying water levels (100–115% fwb) were tested using a central composite design. Increasing water levels increased loaf specific volume, while increasing xanthan gum levels decreased the volume. As skim milk powder levels increased, loaf height decreased. Quality differences between the hybrids were maintained throughout the RSM.     

Starch–Hydrocolloid Interaction in Chemically Leavened Gluten‐Free Sorghum Bread

A satisfactory chemically leavened gluten‐free sorghum bread method was developed by using a blend of 90% commercially milled sorghum flour and 10% rice, tapioca, or potato starch as the “flour.” The most effective starch/hydrocolloid combinations in the formula were potato starch with 4% xanthan, tapioca starch with 3% hydroxypropyl methylcellulose, and rice starch with 3% xanthan. Overall, there was not a significant difference in the quality of loaves made with each starch/hydrocolloid combination. Rapid visco analysis showed that batter viscosity did not have a significant impact on loaf volume index but did affect crumb grain properties. Batters with lower viscosity produced loaves with better crumb grain.     

Compliance with Gluten‐Free Labelling Regulation in the Brazilian Food Industry

Gluten is an important protein complex for baking products found in wheat, rye, barley, and some oat varieties. However, some people need to avoid these grains and their products because they result in gluten‐related disorders. The only treatment for these individuals is to engage in a gluten‐free diet. The objective of this work was to verify if the gluten content of several commercial food products sold in Brazil complied with their labeling. The Méndez ELISA R5 sandwich method was used to analyze 437 samples, and of these, 70% were labeled as gluten‐free, 26% as containing gluten, and 4% not labeled in relation to gluten. The results indicated that 89% of the products labeled as gluten‐free were correctly labeled and 11% were not, which represented a risk for celiac people.     

Textural Comparisons of Gluten‐Free and Wheat‐Based Doughs,Batters, and Breads

Studies were conducted with two newly developed gluten‐free bread recipes. One was based on corn starch (relative amount 54), brown rice (25), soya (12.5), and buckwheat flour (8.5), while the other contained brown rice flour (50), skim milk powder (37.5), whole egg (30), potato (25), and corn starch (12.5), and soya flour (12.5). The hydrocolloids used were xanthan gum (1.25) and xanthan (0.9) plus konjac gum (1.5), respectively. Wheat bread and gluten‐free bread made from commercial flour mix were included for comparison. Baking tests showed that wheat and the bread made from the commercial flour mix yielded significantly higher loaf volumes (P < 0.01). All the gluten‐free breads were brittle after two days of storage, detectable by the occurrence of fracture, and the decrease in springiness (P < 0.01), cohesiveness (P < 0.01), and resilience (P < 0.01) derived from texture profile analysis. However, these changes were generally less pronounced for the dairy‐based gluten‐free bread, indicating a better keeping quality. Confocal laser‐scanning microscopy showed that the dairy‐based gluten‐free bread crumb contained network‐like structures resembling the gluten network in wheat bread crumb. It was concluded that the formation of a continuous protein phase is critical for an improved keeping quality of gluten‐free bread.     

Definition of the “Purity Protocol” for Producing Gluten‐Free Oats

Several oat processors in the United States and Canada operate under what is referred to as a Purity Protocol for the provision of gluten‐free oats. This term is derived from a Health Canada position statement that indicated that pure oats, which they defined as oats that are harvested, transported, stored, processed, and manufactured under good manufacturing practices (GMPs) to minimize the presence of gluten, can safely be consumed by some persons with celiac disease. While proprietary definitions of the appropriate GMPs have been used in industry for many years, no independent definition of the requirements to make a Purity Protocol claim has been published. This paper provides a consensus definition of the Purity Protocol requirements based on input from the four largest Purity Protocol oat processors in North America. This definition provides transparency to gluten‐free consumers and allows for auditing of a Purity Protocol claim.     

Formation of Enzyme‐Resistant Starch in Bread as Affected by High‐Amylose Wheat Flour Substitutions

High‐amylose wheat flour was used to substitute for normal wheat flour in breadmaking and formation of resistant starch (RS) in bread during storage was determined. Substitution with high‐amylose wheat flour (HAF) decreased peak and final viscosities, breakdown, and setback. Doughs with HAF substitutions were weaker and less elastic, and absorbed more water than those of the normal wheat flour. After baking, RS contents in breads with 10, 30, and 50% HAF substitutions were 1.6, 2.6, and 3.0% (db), respectively, higher than that of the control (0.9%, db). The levels of RS increased gradually during storage for one, three, and five days. With substitutions of 30 and 50% HAF, the total levels of dietary fiber (DF) and RS in bread after five days of storage were 15.5 and 16.8% (db), respectively, as compared to 13.0% (db) in bread from the normal wheat flour. The loaf volumes and appearances of bread crumbs made from HAF substitutions of 10 and 30% were not significantly different from those of the control, whereas the substitution with 50% HAF decreased loaf volume and resulted in inferior appearance of breadcrumbs. The firmness of breadcrumbs increased along with increase in the level of HAF substitutions after baking. During storage, the firmness of breadcrumb with 10% HAF substitutions was higher than that of the control, whereas breads with 30 and 50% HAF substitutions had similar firmness to the control. As a result, HAF might be used to substitute for up to 50% normal wheat flour to make bread with acceptable bread quality and significantly high amount of RS.     

Application of Polished‐Graded Wheat Grains for Sourdough Bread

Flours obtained by a specific polishing process were used to prepare sourdough and bread. Three fractions designated C‐1 (100–90%), C‐5 (60–50%), and C‐8 (30–0%) were studied. The pH, total titratable acidity levels, and buffering capacity of sourdoughs made from polished flours were significantly different from those of the control sourdough with No. 1 Canada Western Red Spring (CW), and they provided sourdough breads with better qualities than that of CW. The growth of lactic acid bacteria and yeast in polished flour sourdoughs were significantly accelerated during fermentation over that in CW sourdough. Higher maturation of polished flour sourdoughs softened the hardness of mixed dough. The intricate network of honeycomb structure gluten and uneven surface of starch granules were distinctly observed in SEM images. Substitutions of C‐5 or C‐8 sourdoughs for CW significantly increased the loaf volume and softened breadcrumbs more than CW sourdough. Flour qualities of polished flours such as suitable acidity and good buffering capacity caused by the bran fraction were effective for better growth and longer life of yeast in the dough during fermentation. Therefore, application of polished flours in sourdough bread would improve rheological properties of dough and bread as compared with CW sourdough.     

REVIEW: Effects of Germination on the Nutritional Profile of Gluten‐Free Cereals and Pseudocereals: A Review

There are a growing number of individuals diagnosed with food allergies and intolerances. Gluten, in particular, is avoided by many individuals because of celiac disease, gluten intolerance, and gluten ataxia. Individuals with allergies, intolerances, or both follow strict diets, but there is concern that these individuals may be at risk of several nutrient deficiencies, including decreased calcium, iron, B vitamins, and fiber. To prevent deficiencies, alternative sources of these nutrients must be provided. Gluten‐free cereals and pseudocereals such as amaranth, buckwheat, corn, millet, rice, sorghum, and quinoa can be excellent sources of vitamins, minerals, fiber, and other important nutrients. Germination of these edible seeds has been shown to further increase nutrient content and to reduce antinutrients. Their use to naturally fortify and enrich gluten‐free foods has great potential. Although there are many benefits to germinated seeds in food, more research must be done to improve texture and sensory properties to gain wider consumer acceptance. A review of germination of gluten‐free cereals and pseudocereals and its effect on their nutritional profile is presented.     

In Vitro Starch Digestibility of Gluten‐Free Spaghetti Based on Maize,Chickpea, and Unripe Plantain Flours

Gluten‐free and high indigestible carbohydrate food development is a topic that deserves investigation because of an increased focus on gluten intolerance and celiac disease and on metabolic disorders caused by overweight and obesity. Here, chickpea and maize flours were used as sources of protein and carbohydrate (because of the level used in the mixture) and unripe plantain as an indigestible carbohydrate source in composite gluten‐free spaghetti elaboration. The mixture of unripe plantain, chickpea, and maize was used at different levels to prepare spaghetti (samples S15Pla and S25Pla); control pasta was made of 100% semolina (S100Sem), and a 100% unripe plantain flour (S100Pla) pasta was also evaluated. In vitro amylolysis rate of fresh and stored (three and five days) spaghetti was assessed. The spaghetti with 100% unripe plantain (S100Pla) had higher resistant starch (RS) content than the control sample and the two cooked composite gluten‐free spaghettis (S15Pla, S25Pla), and RS further increased with the storage time. The plantain spaghetti (S100Pla) also had the highest rapidly digestible starch and the lowest slowly digestible starch contents; this pattern agrees with the hydrolysis rate, especially after cold storage. The stored S25Pla spaghetti showed the lowest hydrolysis rate and predicted glycemic index. Blending chickpea, maize, and unripe plantain flours represents a way to obtain gluten‐free spaghetti with high nondigestible carbohydrate content and slow digestion properties.     

Development of a Novel Staining Procedure for Visualizing the Gluten–Starch Matrix in Bread Dough and Cereal Products

A novel staining procedure has been developed to visualize the gluten– starch matrix in wheat flour dough. Dough samples mixed to the final stage were stained with 26 fluorescent reagents, and each stained sample was observed with three sets of fluorescence filters (blue, green, and red). Of all the combinations of reagents and filters, the combination of acid magenta and the blue fluorescent filter set was the most effective in distinguishing starch granules from gluten network structure. Its effectiveness was further demonstrated with gluten and starch granule samples, in which the contrast was clearer when observed with the blue fluorescent filter set than without any fluorescent filter. Visualizing the gluten–starch matrix in dough samples at four mixing stages with the same procedure resulted in clear identification of the changes in gluten network structure because of the differences in mixing stages. The same procedure also enabled us to distinguish starch from gluten in white salted noodles, baked cookies, and flour particles. The proposed procedure is quicker, simpler, and has a lower risk of altering the sample than other conventional ones, and it is expected to become a useful tool in cereal studies.     

Impact of Chickpea‐ and Raw Plantain‐Based Gluten‐Free Snacks on Weight Gain,Serum Lipid Profile,and Insulin Resistance of Rats Fed with a High‐Fructose Diet

Two gluten‐free snacks containing chickpea, plantain, and maize flours at different concentrations were prepared. The impact of chickpea or plantain flour level on weight gain, insulin resistance, and serum lipid profile of rats fed a high‐fructose diet was evaluated. A dose of 0.93 g/kg was used in the experiments to simulate the snack consumption level by humans (average content of a small package, which is twice the portion recommended by the U.S. Department of Agriculture). Compared with a high‐fructose reference diet, consumption of both snacks decreased weight gain, fasting serum glucose, and triglycerides. The effect was more pronounced for snack B, with higher chickpea content. Consumption of these snacks may also have beneficial effects against obesity and cardiometabolic complications. Chickpea flour is a promising functional ingredient for the development of antiobesity foods.     

Effects of Ferulic Acid and Transglutaminase on Hard Wheat Flour Dough and Bread

The effects of ferulic acid and transglutaminase (TG) on the properties of wheat flour dough and bread were investigated. Ferulic acid and TG were blended with hard wheat flour at levels of 250 and 2,000 ppm of flour weight, respectively. The addition of ferulic acid reduced the mixing time and mixing tolerance. The addition of TG did not obviously affect the mixing properties. Significant effects of ferulic acid plus TG on the rested dough texture were observed for overmixed dough. The maximum resistance (Rmax) of the dough was significantly reduced with the addition of ferulic acid but increased with the addition of TG. The addition of TG with ferulic acid restored the Rmax reduced by ferulic acid alone. The proportion of SDS‐soluble high molecular weight proteins in the dough increased with the addition of ferulic acid and decreased with TG, when assessed with size‐exclusion HPLC fractionation. Although the addition of TG improved the handling properties of the dough made sticky with added ferulic acid, it did not improve the quality of the bread with added ferulic acid as measured by loaf volume and firmness.     

Glass Transition Behavior and Rheological Properties of Surfactants and Gluten‐Surfactant Mixtures

Diacetyltartaric acid esters of monoglycerides (DATEM) and sodium stearoyl lactylate (SSL) displayed thermal events corresponding to glass transition temperature (T_g) and melting of crystalline domains, while monoglycerides (MG) exhibited an endothermic peak corresponding to melting of crystalline structures when heated in a differential scanning calorimeter. The plasticizing effect of water on T_g of gluten exhibited little apparent change in the presence of DATEM, MG, or SSL (glutensurfactant 10:1), in the moisture range of 6.5–21.3% as shown by mechanical spectrometry and differential scanning calorimetry. Glutensurfactant mixtures showed higher G′ and apart from gluten‐SSL, which displayed higher tan δ (G″/G′) at ≤2.51 rad/sec, lower tan δ values than gluten in the frequency range of 0.1–100 rad/sec. DATEM and SSL softened the gluten network before cross‐linking reactions, while MG shifted the onset of cross‐linking reactions to higher temperatures at moisture contents of 30–40%. Complete vitrification of the gluten network occurred at higher temperatures, at the indicated moisture contents, in the presence of surfactants. Softening of the matrix and the delay in cross‐linking of gluten, in the presence of surfactants, might allow for greater expansion of doughs during baking with concomitant increase in loaf volumes.     

Quality of Fiber‐Enriched Spaghetti Containing Microbial Transglutaminase

The effects of transglutaminase (TG) on the properties of semolina dough and pasta cooking properties in durum‐only and fiber‐enriched pasta were investigated. TG was blended at levels 0, 0.05, 0.1, 0.25, 0.5, and 1% of semolina weight with semolina and semolina‐pollard (60% w/w) and semolina‐guar gum (15%) mixtures. The addition of TG increased dough maximal resistance, making the dough inextensible at >1%. Optimum effects on dough strength were obtained at 0.5% TG; this dough gave the firmest and least sticky pasta. A more extensive and thicker protein matrix was observed in the TG pasta by confocal scanning laser microscopy, indicating more cross‐links were formed, a finding supported by measuring percentage of unextracted polymeric protein. TG was unable to overcome the negative effect of 60% pollard on cooking loss or 15% guar gum on stickiness. Gluten was generally more effective than TG in restoring the properties of pastas with added fiber.     

Identification of Wheat Protein Components Involved in Polymer Formation on Incubation with Transglutaminase

Transglutaminase (TG) catalyzes acyl‐transfer reactions, introducing covalent cross‐links between l ‐lysine and l ‐glutamine residues. As a result, peptides are connected and the structure of a stabilized protein network is formed, thereby improving protein strength. In this study, wheat flour was incubated with TG for different time intervals (0, 30, 60, 120, and 240 min) and the extent of polymer formation and proteins involved were investigated by SE‐HPLC, SDS‐PAGE, and RP‐HPLC. Results indicated that the amount of polymers formed increased with incubation time. TG induced the cross‐linking of HMW glutenin subunits more so than of other proteins in wheat.     

A New Method to Study Simple Shear Processing of Wheat Gluten‐Starch Mixtures

This article introduces a new method that uses a shearing device to study the effect of simple shear on the overall properties of pasta‐like products made from commercial wheat gluten‐starch (GS) blends. The shear‐processed GS samples had a lower cooking loss (CL) and a higher swelling index (SI) than unprocessed materials, suggesting the presence of a gluten phase surrounding starch granules. Pictures of dough micro‐structure by confocal scanning laser microscopy (CSLM) showed the distribution of proteins in the shear‐processed samples. This study revealed that simple shear processing could result in a product with relevant cooking properties as compared with those of commercial pasta. Increasing gluten content in GS mixtures led to a decrease in CL and an increase in maximum cutting stress of processed samples, whereas no clear correlation was found for SI values of sheared products. It was concluded that the new shearing device is unique in its capability to study the effect of pure shear deformation on dough development and properties at mechanical energy and shear stress levels relevant to industrial processing techniques like pasta extrusion.     

Basic Rheology of Bread Dough with Modified Protein Content and Glutenin‐to‐Gliadin Ratios

The uniaxial elongational and shear rheology of doughs varying in either the protein content or glutenin‐to‐gliadin ratio were investigated. Increasing the protein content at constant glutenin‐to‐gliadin ratio increased the strain‐hardening properties of the dough, as shown by increasing elongational rupture viscosity and rupture stress. Glutenin and gliadin had a more complex effect on the elongational properties of the dough. Increased levels of glutenin increased the rupture viscosity but lowered the rupture strain, while elevated gliadin levels lowered the rupture viscosity but increased the rupture strain. These observations provide rheological support for the widely inferred role of gliadin and glutenin in shaping bread dough rheology, namely that gliadin contributes the flow properties, and glutenin contributes the elastic or strength properties. The shear and elongational properties of the doughs were quite different, reflecting the dissimilar natures of these two types of flow. Increasing protein content lowered the maximum shear viscosity, while increasing the glutenin‐to‐gliadin ratio increased maximum shear viscosity. Strong correlations between the results of basic and empirical rheology were found. These basic, or fundamental, rheological measurements confirmed prior empirical studies and supported baking industry experience, highlighting the potential of basic rheology for bread and wheat research.     

Effect of Glutamate Accumulation During Sourdough Fermentation with Lactobacillus reuteri on the Taste of Bread and Sodium‐Reduced Bread

NaCl is an important contributor to the taste and texture of bread; therefore, it is challenging to reduce NaCl in bread without compromising quality. This study investigated sensory properties of bread with sourdough fermented with Lactobacillus reuteri accumulating glutamate or γ‐aminobutyrate (GABA). Sourdough was fermented with the GABA‐producing L. reuteri 100‐23 and LTH5448 as well as the glutamate‐accumulating L. reuteri 100‐23ΔgadB and TMW1.106. A consumer panel detected significant differences in the taste of bread with 6% addition of sourdough fermented with glutamate‐ or GABA‐producing L. reuteri. Remarkably, this difference was also detected when GABA‐producing L. reuteri 100‐23 was compared with its glutamate‐producing isogenic mutant L. reuteri 100‐23ΔgadB. The intensity of the salty taste of sourdough bread produced with 1% (flour basis) salt was equivalent to the intensity of the salty taste of reference bread produced with 1.5% salt. A trained panel found that sourdough breads (1 or 2% NaCl flour base) had a higher sour and umami taste intensity when compared with reference bread with the same salt content. Bread produced with sourdough fermented with L. reuteri 100‐23ΔgadB consistently had a higher umami taste intensity when compared with other sourdough breads. Neither sourdough addition nor NaCl level influenced bread volume or texture. In conclusion, the use of sourdough fermented with glutamate‐accumulating lactobacilli allowed reduction of NaCl without adverse effects on the taste or other quality attributes of bread.