Fermented Sorghum as a Functional Ingredient in Composite Breads

Whole sorghum flour was fermented (a five‐day natural lactic acid fermentation) and dried under forced draught at 60°C, and evaluated for its effect on sorghum and wheat composite bread quality. In comparison with unfermented sorghum flour, fermentation decreased the flour pH from 6.2 to 3.4, decreased total starch and water‐soluble proteins, and increased enzyme‐susceptible starch, total protein, and the in vitro protein digestibility (IVPD). Fermentation and drying did not decrease the pasting temperature of sorghum flour, but slightly increased its peak and final viscosity. In comparison with composite bread dough containing unfermented sorghum flour, fermented and dried sorghum flour decreased the pH of the dough from 5.8 to 4.9, increased bread volume by ≈4%, improved crumb structure, and slightly decreased crumb firmness. IVPD of the composite bread was also improved. Mixing wet fermented sorghum flour directly with wheat flour (sourdough‐type process) further increased loaf volume and weight and reduced crumb firmness, and simplified the breadmaking process. It appears that the low pH of fermented sorghum flour inactivated amylases and increased the viscosity of sorghum flour, thus improving the gas‐holding capacity of sorghum and wheat composite dough. Fermentation of sorghum flour, particularly in a sourdough breadmaking process, appears to have considerable potential for increasing sorghum utilization in bread.     

Malted Sorghum as a Functional Ingredient in Composite Bread

To alleviate the adverse effects (grittiness and high crumb firmness) caused by the inclusion of sorghum flour in composite breads, sorghum grain was malted with the aim of decreasing the gelatinization temperature and increasing the water‐holding capacity of sorghum flour. Four different heat treatments were investigated: drying the malt at high temperatures (50–150°C), stewing, steaming, and boiling before drying the malt at 80°C. Malting decreased the pasting temperature of sorghum to values approaching those of wheat flour, but the paste viscosity was very low. Increasing the malt drying temperature inactivated the amylases but gave malts of darker color and bitter taste. Stewing, steaming, and boiling the malt before drying almost completely inactivated the amylases and increased the enzyme‐susceptible starch content and the paste viscosity of malt flours. Bread made with boiled malt flour (30%) had an improved crumb structure, crumb softness, water‐holding capacity, and resistance to staling, as well as a fine malt flavor compared with the bread made with grain sorghum flour (30%). Consumers preferred the malted sorghum bread over the bread made with plain sorghum flour.     

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.     

Characteristics of French Bread Baked from Wheat Flours of Reduced Starch Amylose Content

Wheat genotypes of wild type, partial waxy, and waxy starch were used to determine the influence of starch amylose content on French bread making quality of wheat flour. Starch amylose content and protein content of flours were 25.0–25.4% and 14.3–16.9% for wild type; 21.2 and 14.9% for single null partial waxy; 15.4–17.1% and 13.2–17.6% for double null partial waxy; and 1.8 and 19.3% for waxy starch, respectively. Wheat flours of double null partial waxy starch produced smaller or comparable loaf volume of bread than wheat flours of wild type and single null partial waxy starch. Waxy wheat flour, despite its high protein content, generally produced smaller volume of bread with highly porous, glutinous, and weak crumb than wheat flours of wild type and partial waxy starch. French bread baked from a flour of double null partial waxy starch using the sponge-and-dough method maintained greater crumb moisture content for 24 hr and softer crumb texture for 48 hr of storage compared with bread baked from a flour of wild type starch. In French bread baked using the straight-dough method, double null partial waxy wheat flours with protein content >14.3% exhibited comparable or greater moisture content of bread crumb during 48 hr of storage than wheat flours of wild type starch. While the crumb firmness of bread stored for 48 hr was >11.4 N in wheat flours of wild type starch, it was <10.6 N in single or double null partial waxy flours. Wheat flours of reduced starch amylose content could be desirable for production of French bread with better retained crumb moisture and softness during storage.     

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.     

Influence of baking conditions and precursor supplementation on the amounts of the antioxidant pronyl-L-lysine in bakery products

The influence of baking conditions and dough supplements on the amounts of the antioxidant and Phase II-Enzyme modulating, protein-bound 2,4-dihydroxy-2,5-dimethyl-1-(5-acetamino-5-methoxycarbonyl-pentyl)-3-oxo-2H-pyrrol (pronyl-L-lysine) in bakery products was investigated in quantitative studies. These studies revealed high amounts of the antioxidant in bread crust, only low amounts in the crumb, and the absence of this compound in untreated flour. The amounts of pronyl-L-lysine were found to be strongly influenced by the intensity of the thermal treatment. For example, increasing the baking time from 70 to 210 min or increasing the baking temperature from 220 to 260 degrees C led to a 5- or 3-fold increase in the concentrations of this antioxidant in the crust, respectively. In addition, modifications in the recipe showed to have a major impact on pronyl-L-lysine formation. For example, substituting 5% of the flour with the lysine-rich protein casein or with 10% of glucose increased the amounts of the antioxidant by more than 200%. Quantitative analyses of commercial bread samples collected from German bakeries revealed the highest amount of 43 mg/kg for a full grain bread, followed by a rye/wheat bread, both of which have been sourdough fermented. A mixed-grain bread as well as pale wheat bread, both prepared without sourdough fermentation, contained significantly lower amounts of pronyl-L-lysine, and German pretzels, which are treated with a dilute sodium hydroxide solution prior to baking, contained only trace amounts of pronyl-L-lysine (e.g., less than 5 mg/kg were detectable in pretzels). Systematic studies revealed that the decrease of the pH value induced by microbial acid formation during sourdough fermentation is the clue for producing high amounts of pronyl-L-lysine in baking products. These data clearly demonstrate for the first time that the amounts of the antioxidant and chemopreventive compound pronyl-L-lysine in bakery products is strongly dependent on the manufacturing conditions as well as the recipe.     

Effects of Varying Weight Ratios of Large and Small Wheat Starch Granules on Experimental Straight‐Dough Bread

One commercial bread wheat flour with medium strength (11.3% protein content, 14% mb) was fractionated into starch, gluten, and water solubles by hand‐washing. The starch fraction was separated further into large and small granules by repeated sedimentation. Large (10–40 μm diameter) and small (1–15 μm diameter) starch fractions were examined. Flour fractions were reconstituted to original levels in the flour using composites of varying weight percentages of starch granules: 0% small granules (100% large granules), 30, 60, and 100% (0% large granules). A modified straight‐dough method was used in an experimental baking test. Crumb grain and texture were significantly affected. The bread made from the reconstituted flour with 30% small granules and 70% large granules starch had the highest crumb grain score (4.0, subjective method), the highest peak fineness value (1,029), and the second‐highest elongation ratio (1.55). Inferior crumb grain scores and low fineness and elongation ratios were observed in breads made from flours with starch fractions with 100% small granules or 100% large granules. As the proportion of small granules increased in the reconstituted flour, it yielded bread with softer texture that was better maintained than the bread made from the reconstituted reference flour during storage.     

Starch Retrogradation and Firming of Bread Containing Hydroxypropylated,Acetylated, and Phosphorylated Cross‐Linked Tapioca Starches for Wheat Flour

The present investigation aims at understanding the role of chemically modified starch on the firmness of fresh or stale bread. Bread was prepared from wheat flour or substituted wheat flour that contained 18% chemically modified tapioca starch and 2% vital gluten. Hydroxypropylated tapioca starch (HTS), acetylated tapioca starch (ATS), phosphorylated cross‐linked tapioca starch (PTS), and native tapioca starch (NTS) were tested. Bread prepared from the substituted flour with PTS showed a firmer texture on the day of baking compared with bread prepared from NTS, HTS, and ATS. PTS retained its granular structure in the gluten network after baking and seemed to play the role of filler particles in the gluten matrix, thereby increasing firmness of fresh bread crumb. Bread prepared from the substituted flour with HTS or ATS firmed at a lower rate and showed a lower endothermic melting enthalpy of amylopectin after three days of storage compared with NTS or PTS. These findings suggest that the staling of bread containing chemically modified tapioca starch involves recrystallization of amylopectin.     

Moderate decrease of pH by sourdough fermentation is sufficient to reduce phytate content of whole wheat flour through endogenous phytase activity

Whole wheat bread is an important source of minerals but also contains considerable amounts of phytic acid, which is known to impair their absorption. An in vitro trial was performed to assess the effect of a moderate drop of the dough pH (around 5.5) by way of sourdough fermentation or by exogenous organic acid addition on phytate hydrolysis. It was shown that a slight acidification of the dough (pH 5.5) with either sourdough or lactic acid addition allowed a significant phytate breakdown (70% of the initial flour content compared to 40% without any leavening agent or acidification). This result highlights the predominance of wheat phytase activity over sourdough microflora phytase activity during moderate sourdough fermentation and shows that a slight drop of the pH (pH value around 5.5) is sufficient to reduce significantly the phytate content of a wholemeal flour. Mg "bioaccessibility"of whole wheat dough was improved by direct solubilization of the cation and by phytate hydrolysis.     

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.     

Baking Performance of Durum and Soft Wheat Flour in a Sponge-Dough Breadmaking Procedure

Breadmaking properties were determined for formulations that included durum, soft, and spring wheat flour, using a pound-loaf sponge-dough baking procedure. Up to 60% durum or soft wheat flour plus 10% spring wheat flour could be incorporated at the sponge stage for optimum dough-handling properties. At remix, the dough stage required 30% spring wheat flour. Bread made with 100% spring wheat flour was used as a standard for comparison. Bread made with 60% durum flour exhibited internal crumb color that was slightly yellow. When storing pound bread loaves for 72 hr, crumb moisture content remained unchanged. Crumb firmness and enthalpy increased the most in bread made with 60% soft wheat flour. Crumb firmness increased the least in bread made with 100% spring wheat flour. Enthalpy changed the least in bread made with 60% durum flour. Crumb moisture content was significantly correlated with crumb firmness (r = -0.82) and enthalpy (r = -0.65). However, crumb moisture content was specific for each type of flour and a function of flour water absorption; therefore, these correlations should be interpreted with caution. Crumb firmness and enthalpy were significantly correlated (r = 0.65). Ball-milling flour resulted in an increase in water absorption of ≈2% and in crumb moisture content of ≈0.5% but had no effect on either crumb firmness or enthalpy.     

White Pan Bread and Sugar‐Snap Cookies Containing Wheat Starch Phosphate,A Cross‐Linked Resistant Starch

Pup‐loaf bread was made with 10, 30, and 50% substitution of flour with wheat starch phosphate, a cross‐linked resistant starch (XL‐RS4), while maintaining flour protein level at 11.0% (14% mb) by adding vital wheat gluten. Bread with 30% replacement of flour with laboratory‐prepared XL‐RS4 gave a specific volume of 5.9 cm³/g compared with 6.3 g/cm³ for negative control bread (no added wheat starch), and its crumb was 53% more firm than the control bread after 1 day at 25°C, but 13% more firm after 7 days. Total dietary fiber (TDF) in one‐day‐old bread made with commercial XL‐RS4 at 30% flour substitution increased 3–4% (db) in the control to 19.2% (db) in the test bread, while the sum of slowly digestible starch (SDS) plus resistant starch (RS), determined by a modified Englyst method, increased from 24.3 to 41.8% (db). The reference amount (50 g, as‐is) of that test bread would provide 5.5 g of dietary fiber with 10% fewer calories than control bread. Sugar‐snap cookies were made at 30 and 50% flour replacement with laboratory‐prepared XL‐RS4, potato starch, high‐amylose (70%) corn starch, and commercial heat‐moisture‐treated high‐amylose (70%) corn starch. The shape of cookies was affected by the added starches except for XL‐RS4. The reference amount (30 g, as‐is) of cookies made with commercial XL‐RS4 at 30% flour replacement contained 4.3 g (db) TDF and 3.4 g (db) RS, whereas the negative control contained 0.4 g TDF and 0.6 g RS. The retention of TDF in the baked foods containing added XL‐RS4 was calculated to be >80% for bread and 100% for cookies, while the retention of RS was 35–54% for bread and 106–113% for cookies.     

Ethanol‐Production Performance of Ozone‐Treated Tannin Grain Sorghum Flour

Ozone has been reported as being able to degrade macromolecules such as cellulose, starch, lignins, and tannins in the textile, pulping, and water‐treatment industries. Thus, we hypothesized that ozone treatment may also inactivate tannin activity and increase fermentation efficiency of tannin sorghum lines. The objective of this research was to study the physicochemical properties of ozone‐treated whole tannin grain sorghum flour and its fermentation performance in ethanol production. Results showed that the ethanol yields from ozone‐treated tannin grain sorghums were significantly higher than yields from the untreated flour. The fermentation efficiency of ozone‐treated tannin grain sorghum was approximately 90%, which was 8–14% higher than that of untreated samples at the 36th hr of fermentation. At the end of 72 hr of fermentation, the efficiencies of ozone‐treated sorghum flour were 2–5% higher than those of untreated samples. Measured tannin levels of ozone‐treated samples decreased significantly from 3.8 to 2.7%. Gel‐permeation chromatographic results indicated that both degradation and polymerization processes might have happened to starch molecules during ozone treatment. Rapid Visco Analyzer data showed that the setback of viscosity of ozone‐treated flour was lower than that of untreated flours. Distillers dried grains with solubles made from ozone‐treated sorghum were low in residual starch (<1%) and high in crude protein (≈35%). Therefore, ozonation could be a novel and useful method to improve ethanol yield and fermentation efficiency of tannin grain sorghum.     

Factors Controlling Gas Cell Failure in Bread Dough

Stress relaxation in the wall of a gas bubble, as measured by the alveograph, was used to study surface tension at the gas-dough interface of doughs from flours producing differing bread crumb grains. The surface tensions in the various wheat flour doughs were not different. Dough rheological properties, as measured by both dynamic oscillatory rheometry and lubricated uniaxial compression, were not different for doughs made from wheat flours that gave breads with different crumb grains. However, when the effect of starch granule size on gas cell wall stability was tested, the presence of a greater proportion of large starch granules in wheat flour dough was sufficient to result in gas cell coalescence and open crumb grain in the final baked product. This suggests that starch granule size is at least one of the factors that affects the crumb grain of bread.     

Effects of Bran Fermentation on Quality and Microstructure of High‐Fiber Wheat Bread

We compared the effects of spontaneous fermentation of the bran fraction and fermentation with added yeast or added yeast and lactic acid bacteria (Lactobacillus brevis) on the quality of wheat bread supplemented with bran. Prefermentation of wheat bran with yeast or with yeast and lactic acid bacteria improved the loaf volume, crumb structure, and shelf life of bread supplemented with bran. The bread also had added flavor and good and homogenous crumb structure. Elasticity of the crumb was excellent. Spontaneous fermentation of the bran fraction did not have the same positive effects on bread quality. The microstructure of the breads was characterized by light microscopy. The positive effect of fermentation of bran on bread quality was evident when comparing the well‐developed protein network structure of the breads baked with fermented bran with the control bread. Prefermentation of the bran with yeast and lactic acid bacteria had the greatest effect on the structure of starch. The starch granules were more swollen and gelatinized in the breads made with prefermented bran. The pretreatments of the bran fraction had no detectable effect on the microstructure of the cell wall particles in the test breads.     

REVIEW: Aroma of Wheat Bread Crumb

Bread aroma is an important parameter for bread quality, and this review aims to provide an overview of aroma compounds identified in bread crumb and how these compounds are formed. More than 150 volatile compounds were identified in bread crumb, and they mainly originated from the fermentative activity of yeast, from oxidation of flour lipids, and to a lower extent from Maillard reactions. Of those volatile compounds, 45 compounds can be characterized as aroma compounds, because they most likely can be sensed when the bread is eaten because of their high odor activity values and flavor dilution factors. The influence of ingredients and mixing conditions on bread aroma has scarcely been investigated. The fermentation conditions (yeast level and strain as well as fermentation temperature and time) were found to significantly influence the aroma of bread crumb. Yeast level and strain mainly influence formation of compounds directly related to the fermentative activity of yeast, whereas fermentation temperature and time also influence formation of compounds from oxidation of flour lipids.     

Cooking,Roasting, and Fermentation of Chickpeas,Lentils, Peas,and Soybeans for Fortification of Leavened Bread

The effects of cooking, roasting, and fermentation on the composition and protein properties of grain legumes and the characteristics of dough and bread incorporated with legume flours were determined to identify an appropriate pretreatment. Oligosaccharide content of legumes was reduced by 76.2–96.9% by fermentation, 44.0–64.0% by roasting, and 28.4–70.1% by cooking. Cooking and roasting decreased protein solubility but improved in vitro protein digestibility. Mixograph absorption of wheat and legume flour blends increased from 50–52% for raw legumes to 68–76, 62–64, and 74–80% for cooked, roasted, and fermented ones, respectively. Bread dough with cooked or roasted legume flour was less sticky than that with raw or fermented legume flour. Loaf volume of bread baked from wheat and raw or roasted legume flour blends with or without gluten addition was consistently highest for chickpeas, less for peas and lentils, and lowest for soybeans. Roasted legume flour exhibited more appealing aroma and greater loaf volume of bread than cooked legume flour, and it appears to be the most appropriate preprocessing method for incorporation into bread.     

Effects of Oat Grain Hydrothermal Treatments on Wheat-Oat Flour Dough Properties and Breadbaking Quality

Hydrothermal treatments, which are routine in oat processing, have profound effects on oat flour dough rheological properties. The influence of roasting and steam treatments of oat grain on dough mixing and breadbaking properties was investigated when hydrothermally treated oat flour was blended with wheat flour. Roasting of oat grain (105°C, 2 hr) resulted in oat flours that were highly detrimental to wheat flour dough mixing properties and breadbaking quality. Steaming (105°C, 20 min) or a combination of roasting and steaming of oat grain significantly improved the breadbaking potential of the oat flours. The addition of oat flours increased water absorption and mixing requirements of the wheat flour dough and also decreased bread loaf volume. However, at the 10% substitution level, steamed oat flours exhibited only a gluten dilution effect on bread loaf volume when wheat starch was used as a reference. Oat flour in the breadbaking system decreased the retrogradation rate of bread crumb starch. The results indicate that adequate hydrothermal treatments of oat grain are necessary for oat flour breadbaking applications. Steamed oat flours used at a 10% level retarded bread staling without adversely affecting the loaf volume.     

Influence of Bran Particle Size on Bread‐Baking Quality of Whole Grain Wheat Flour and Starch Retrogradation

The influence of bran particle size on bread‐baking quality of whole grain wheat flour (WWF) and starch retrogradation was studied. Higher water absorption of dough prepared from WWF with added gluten to attain 18% protein was observed for WWFs of fine bran than those of coarse bran, whereas no significant difference in dough mixing time was detected for WWFs of varying bran particle size. The effects of bran particle size on loaf volume of WWF bread and crumb firmness during storage were more evident in hard white wheat than in hard red wheat. A greater degree of starch retrogradation in bread crumb stored for seven days at 4°C was observed in WWFs of fine bran than those of coarse bran. The gels prepared from starch–fine bran blends were harder than those prepared from starch–unground bran blends when stored for one and seven days at 4°C. Furthermore, a greater degree of starch retrogradation was observed in gelatinized starch containing fine bran than that containing unground bran after storage for seven days at 4°C. It is probable that finely ground bran takes away more water from gelatinized starch than coarsely ground bran, increasing the extent of starch retrogradation in bread and gels during storage.     

Effects of Flour Strength,Baking Absorption,and Processing Conditions on the Structure and Mechanical Properties of Bread Crumb

The objective of this study was to determine the effects of flour type, baking absorption, variation in sheeting, and dough proofing time on the density, crumb grain (visual texture), and mechanical properties (physical texture) of bread crumb. All response variables were measured on the same bread crumb specimens. Bread loaves were prepared by a short‐time bread‐making process using four spring wheat flours of varying strength. After crumb density measurement, digital image analysis (DIA) was used to determine crumb grain properties including crumb brightness, cell size, cell wall thickness, and crumb uniformity. Tensile tests were performed on bone‐shaped specimens cut from the same bread slices used for DIA to obtain values for Young's modulus, fracture stress, fracture strain, and fracture energy. Proof time had the most profound influence on the bread with substantial effects on loaf volume, crumb density, crumb brightness, and grain, as well as crumb mechanical properties. Increasing proof time resulted in higher loaf volume, lower crumb density and brightness, coarser crumb with fewer and larger cells with thicker cell walls, and weaker crumb tensile properties. Varying flour type also led to significant differences in most of the measured crumb parameters that appeared to correspond to differences in gluten strength among the flour samples. With increasing flour strength, there was a clear trend to increasing loaf volume, finer and more uniform crumb grain, and stronger and more extensible bread crumb. Increasing baking absorption had virtually no effect on crumb structure but significantly weakened crumb strength and increased fracture strain. In contrast, varying the number of sheeting passes had a minor effect on crumb cellular structure but no effect on mechanical properties. The experimental data were consistent with a cause‐effect relationship between flour strength and the tensile strength of bread crumb arising as a result of stronger flours exhibiting greater resistance to gas cell coalescence, thereby having fewer crumb defects.