THERMAL DIFFUSIVITY MEASUREMENTS of WHEAT FLOUR and WHEAT FLOUR DOUGH

A simple technique was used to measure thermal diffusivity of whole wheat flour and whole wheat flour dough at various levels of moisture and temperatures. the experimental values showed good agreement with the calculated values. It was found that thermal diffusivity of dough increases with moisture and temperature below 60C, but above 60C its value decreases. This is attributed to physico-chemical changes, e.g., starch gelerinization and protein coagulation. Due to these changes swelling and softening of dough occur, which reduce the ability of dough to diffuse thermal energy, thus lowering the value of the thermal diffusivity. Based on the experimental value of wheat dough at various moisture levels and temperatures, the following equation is proposed: α= (7.957 − 0.6346 M + 0.217 T + 0.008 M²− 0.00176 T²− 0.00051 M × T) × 10-7     

Storage Stability of a Puff Pastry Dough with Reduced Water Activity

A puff pastry dough that remained stable at refrigerated temperatures was developed. Dry heat treatment was used to partially destroy amylase and lipoxygenase in wheat flour. Water activity of puff pastry dough was reduced from 0.98–0.90 by addition of 12g sorbitol/100g flour. The adverse effects of sorbitol on baking properties of puff pastry were alleviated by addition of sodium stearoyl lactylate and gum arabic. The puff pastry dough stored at 5°C in air or nitrogen was stable for 75 days without any significant loss in specific volume or pastry height in comparison with the frozen control.     

THERMAL CONDUCTIVITY of INDIAN UNLEAVENED FLAT BREAD (CHAPATI) AT VARIOUS STAGES of BAKING

A steady state technique was used to measure thermal conductivity of whole wheat dough (rolled chapati) and baked chapati (round disc prepared mostly from whole wheat flour dough) at various stages of cooking. Based on the experimental data of chapati at various stages of cooking, a linear equation K = -0.5677 + 0.01396 M + 0.005131 T is proposed for conductivity of wheat flour dough and baked chapati at moisture levels (M): 35 < M < 50 and temperature ranges 35 < T < 60 A separate equation K = 0.3204 + 0.0091 M -0.00805 T predicts thermal conductivity of rolled chapati and baked chapati at T > 60C.     

Experiments on dough rheology to improve screening of bread wheat cultivars

The bread‐making potential of flour may be roughly estimated by dough rheology, especially its tolerance to over‐mixing as determined with the farinograph. The objective of this study was to identify the relative effects of experimental conditions likely to affect dough mixing stability: mixer speed, temperature, salt, yeast and bread additives such as ascorbic acid and preservatives. The addition of 1–2% salt or ascorbic acid (50 mg kg^?1 flour) improved dough mixing stability and counteracted the negative effect of bread preservatives. Mixing salted dough at slow speed (63 rpm) and 25 °C might be a more realistic bread‐making procedure for performing dough rheology assays with equipment such as the farinograph, compared to official methods (only flour and water, no salt; 30 °C). Amongst five bread wheat cultivars, differences existed in dough strengthening response to both salt and ascorbic acid, a property that may find application in wheat breeding and screening.     

Effect of sourdough processing and baking on the content of enniatins and beauvericin in wheat and rye bread

The occurrence of the emerging mycotoxins enniatins (ENNs) and beauvericin (BEA) has been reported in Fusarium-infected cereals. To study the effect of sourdough processing and baking on ENN B, ENN B1, and BEA concentrations, a recently developed stable isotope dilution assay for these mycotoxins was used. After milling of wheat and rye grains naturally contaminated with ENN B and ENN B1, approximately 70–82 % of the two ENNs were found in the bran fraction and the rest remained in flour. BEA was added to flour before sourdough fermentation. In an experiment on a microscale, dough was fermented for 24 h at 30 or 40 °C, which reduced part of the ENNs and BEA in particular at 40 °C. On a standard scale, mixing, resting, and proofing of the bread dough resulted in 13–19 % reduction of the ENNs compared with flour, but in no significant change of BEA. The final baking at 200 °C for 25 min led to a further decrease of the ENNs and BEA, ranging from 9 to 28 % compared with fermented dough. In case of rye sourdough bread, greater reductions of ENNs were found in crust than in crumb. For both wheat and rye flours, overall 25–41 % of ENN B, ENN B1, and BEA were reduced during the whole sourdough bread-making process.     

Effect of flour extraction rate and baking process on vitamin B1 and B2 contents and antioxidant activity of ginger-based products

The effect of flour extraction rate and baking on thiamine (vitamin B₁) and riboflavin (vitamin B₂) content and antioxidant capacity of traditional ginger cake was studied and then compared to white wheat bread. Ginger cake was formulated either with whole-grain (100% extraction rate) or with brown (92% extraction rate) rye flour and baked at 180 °C for 18 min. The antioxidant capacity was evaluated in terms of radical scavenging activity against peroxyl (ROO·) and superoxide anion radicals (O ₂ ^·? ). Thiamine content in rye doughs (F-100% and F-92%) was found to be 38% lower when compared to wheat dough. In contrast, whole-grain and brown rye doughs exhibited an almost fourfold higher riboflavin content than wheat dough. Rye dough baking led to reductions in thiamine (from 53 to 65%) and riboflavin (from 69 to 71%) contents. Likewise, thiamine and riboflavin contents in wheat dough were also reduced (56 and 10%, respectively) after baking; however, ginger cake with whole-grain rye flour exhibited significantly higher thiamine and riboflavin contents. Rye doughs and ginger cakes showed higher scavenging activities against ROO· radicals when compared to that of wheat dough and bread. Thus, baking significantly enhanced ROO· scavenging properties of ginger cakes while only a slight increase was observed in wheat bread. In contrary, baking gave rise to a decrease in SOD-like activity both in ginger cake or wheat bread. Our findings suggest that formulation with whole-grain rye flour can potentially increase B₁ and B₂ vitamin contents as well as the ROO· scavenging capacity of traditional ginger cake.     

Effects of frying temperature,pressure and time on gelatinisation of sago flour as compared to wheat and rice flour in fried coating

This study was conducted to determine the gelatinisation properties of coating with sago flour compared with wheat and rice as influenced by frying temperature, pressure and time. Chicken nuggets were immersed in sago, rice or wheat flour batters and fried at temperatures of 150, 165 and 180 °C and under pressures of 102 and 156 kPa for 0, 6, 18 and 30 s. Results showed that T_o of coatings from sago flour ranged from 71.8 to 74.7 °C. T_o of coatings from wheat flour ranged from 58.2 to 61.2 °C, while that of coatings from rice flour ranged from 77.9 to 78.6 °C. Except for a few combinations, frying temperature and pressure used did not have any significant effects on onset (T_o), peak (T_p) and end (T_e) temperatures. Except for a few combinations, degree of gelatinisation of coatings from sago flour was not influenced by frying temperature and pressure similar to coatings from rice and wheat flour.     

Prediction of the degree of starch gelatinization in wheat flour dough during microwave heating

In order to produce quick-boiling noodles, we made partially pre-gelatinized wheat flour dough by the microwave heating method. A cylindrical-shaped piece of wheat flour dough containing 3% NaCl was heated by 117 W microwave oven operating at 2450 MHz. The sample dough was intermittently heated to allow sufficient gelatinization of the starch granules of the dough. The resultant changes in the internal temperature profiles of the sample dough were measured and compared with numerical prediction, which is the two-dimensional heat conductive equation with a term for internal heat generation based on Lambert’s law. In order to calculate the internal heat generation during microwave heating, we measured the dielectric properties of wheat flour dough at 2450 MHz from 10 to 70 °C by the open-ended coaxial probe method. The calculated temperature history could describe the feature of the experimental one during intermittently microwave heating. Furthermore, the progress of starch gelatinization according to the heat transfer in the sample dough was predicted by the Runge–Kutta gel method. A tendency that the total gelatinization degree increased slowly during the microwave intermittent heating was obtained in the calculated result.     

Studies on Polyphenol Oxidase Activity of Heat Stabilized Whole Wheat Flour and its Chapatti Making Quality

Studies were conducted to evaluate the effect of heat treatment on polyphenol oxidase (PPO) activity of whole-wheat flour (WWF) as well as its chapatti making quality. Whole wheat flour samples were heat treated through various means such as (i) dipping in boiling water (BW) for 20, 30, 40, 50, and 60 min; (ii) inpack heating under pressure (PH) at 0.352 kg/cm² for 4, 6, 8, 10, and 12 min; (iii) microwave heat treatment (MW) at 900 Watt, 2450 MHz for 20, 40, 60, 80, and 100 s. Studies showed that the heat treatment effectively reduced PPO level in whole wheat flour; although, it had adverse effect on the dough-making quality. Based on textural analysis of dough and chapatti as well as sensory scores of chapatti, the conditions for each of the treatments were optimized, i.e., (i) Dipping in boiling water (BW) for 30 min; (ii) inpack heating under pressure (PH) at 0.352 kg/cm² for 10 min; and (iii) microwave heating (MW) for 80 s. A maximum reduction (71.2%) in PPO activity of WWF using microwave treatment could be achieved followed by PH (56.9%) and BW (38.3%). The changes in colour of unbaked chapattis (flattened circular dough, diameter 150.0 mm and thickness 2.0 mm) and changes in quality of baked chapattis were measured to assess the effectiveness of the heat treatment. The L-value (lightness) decreased from 65.2 to 55.8, 65.7 to 58.3, 65.9 to 61.4, and 64.8 to 49.1 in case of BW, PH, MW treated, and control samples, respectively during the 72 h of storage under refrigeration temperature (5–6°C).     

Dough properties and breadmaking qualities of whole waxy wheat flour and effects of additional enzymes

BACKGROUND: Waxy wheat, a new kind of genetically back‐crossed wheat, was applied to make whole bread in this study. Dough properties and bread quality of the whole waxy wheat flour, which was milled from 100% whole grains containing bran and germ, were determined. RESULTS: Whole waxy wheat had lower protein and lipid contents but higher dietary fiber content than whole regular wheat flour. Pasting temperature and viscosity of the whole waxy wheat flour were significantly lower than those of the whole regular wheat. However, the white wheat flour milled from wheat grains with 48% recovery had significantly higher peak viscosity than the whole waxy wheat. Bread made from the whole waxy wheat flour was significantly softer than that from the whole regular wheat flour during storage. However, bread made from whole waxy wheat had significantly lower specific volume than that from the white waxy flour because of the high amount of dietary fiber. Addition of cellulase increased paste viscosity, lowered dough mixing properties and reduced the firmness of the bread. The addition of pentosanase also increased paste viscosity, lowered dough mixing properties, improved loaf volume of bread but increased the firmness of breadcrumbs, while the addition of α‐amylase only increased final viscosity of flour and did not affect dough properties and bread qualities of whole waxy wheat flour. CONCLUSION: As a result, waxy wheat shows superior properties for making whole breads. Additional enzymes are also necessary to improve bread quality and nutritive values of whole waxy bread. Copyright © 2007 Society of Chemical Industry     

Amino Acid Profiles of Fermenting Wheat Sour Doughs

The free amino acid patterns of unfermented and fermented wheat sour doughs started with Lactobacillus plantarum were related by factor analysis to dough yield, ash content of flour, fermentation temperature and presence/absence of yeast, from data corresponding to a central composite design of samples. Individual levels of hydrophobic, acid and basic amino acids as well as total amino acid content positively correlated with extraction rate of flours. The presence of yeast promoted metabolism of histidine, aspartic acid and asparagine, particularly in samples made with whole and wholemeal flours. Proliferation of predominant amino acids by enzymatic release was more notable at higher fermentation temperatures and wholemeal samples. Sour doughs with maximum levels of hydrophobic and basic amino acids were started with no yeast bacterial cultures, made with whole and wholemeal flours and fermented at 35°C.     

The effects of low mixing temperature on dough rheology and bread properties

In this research, the effects of a low mixing temperature on dough rheology and the quality of bread were investigated. In the experiments, strong flour samples (Type 550), 1.5% salt, 3% of yeast and 1% additive mixture were used and dough samples were mixed at 17 °C (low temperature), 23 °C (control) and 30 °C (high temperature). Five different periods (0, 30, 60, 90 and 120 min) were applied at the bulk fermentation stage. At the final proofing stage, the dough was fermented until it reached a constant height. It was determined that almost every bread from dough samples mixed at 17 °C resulted in not only the highest bread volume and bread weight, but also the best texture, elasticity and crumb structure. The results of dough samples mixed at 23 °C were worse than those of dough samples mixed at 17 °C. The worst results were obtained from dough samples mixed at 30 °C (high temperature). As a result, it may be concluded that the quality of bread from dough samples mixed at low temperature (17 °C) is superior to those from dough samples mixed at the higher temperatures. Besides these findings, it may also be stated that prolonging the period of bulk fermentation in dough samples mixed at 17 °C positively develops baking performances.     

Effect of freeze–thaw cycles and additives on rheological and sensory properties of ready to bake frozen chapaties

The wheat grains were conditioned at 18% moisture level for 1 h followed by heating for 80 s in a microwave oven to reduce the activity of polyphenol oxidase as well as other lipolytic and oxidative enzymes. The dough samples were prepared from whole wheat flour (milled from microwave treated wheat grains) using 68% water and 2% salt on flour weight basis as common ingredients. The additives like glycerol monostearate and glycerol (5% and 1% respectively on flour weight basis) were also used in order to study their effects on the quality of ready to bake frozen chapaties (R-BFC) during freeze–thaw cycles. Alveographic properties of R-BFC as well as textural profile and sensory quality of chapaties prepared from R-BFC samples were evaluated during repeated freeze–thaw (FT) cycles. Results showed that the alveographic properties (P, L, and W) decreased significantly ( P  ≤   0.05) in all the samples after each FT cycle, while glycerol added samples showed the least changes. Chapati hardness increased in all the samples up to fourth FT cycle, thereafter sharply decreased. However, chapaties with 1% glycerol were rated better in terms of mouth feel and texture during FT cycles.     

The Effect of Hybrid Carrageenan on the Thermo-rheological Properties of Gluten-Free Flour Doughs Using a Modified Kneading Protocol

Thermo-rheological behaviour of chestnut flour doughs supplemented with kappa/iota-hybrid carrageenan (HC) (up to 2.0%, flour basis (f.b.)) and sodium chloride (1.8%, f.b.) was determined at both target (C1) and final (C5) mixing peaks. For this purpose, small amplitude oscillatory shear (0.01 to 100 Hz), creep–recovery (loading of 50 Pa for 60 s, 30 °C), temperature sweeps (from 30 up to 180 °C) and heating/cooling cycles (between 30 and 60 °C) were conducted on a controlled stress rheometer. Previously, the thermal-mixing behaviour at proposed mixing temperature (50 °C) was conducted on Mixolab® apparatus. Results showed that the dough stability (from 2.2 to 5.8 min) in mixing stage and starch heat resistance to dough processing were significantly improved at proposed mixing temperature, even in the absence of HC. No statistical differences in rheological properties were observed for doughs evaluated in C1; however, those analysed in C5 were significantly modified in the presence of HC, mainly in terms of viscous behaviour (from 52.1 × 10⁶ to 39.1 × 10⁶ Pa s). Creep–recovery data sets, successfully fitted using Burgers model, revealed that the elasticity (J _r/J _max from 73.3 to 87.6%) of doughs analysed in C5 improved with HC addition. Thermal tests showed that the starch transitions were significantly promoted and stabilized with HC addition.     

Characteristics and oil absorption of deep‐fat fried dough prepared from ball‐milled wheat flour

BACKGROUND: High levels of oil in fried products has been recognized as causing health problems. The formation of microstructure during frying is one factor that influences oil absorption. Above the glass transition temperature (T_g), the physical properties of a polymer influences the formation of structure. The ball‐milling process changes the physicochemical properties of wheat flour constituents. The present study investigated the effects of physicochemical changes in wheat flour by the ball‐milling process on structure formation and oil absorption in wheat flour dough model. RESULTS: Dough samples were made from wheat flour that had been ball‐milled for 0 to 10 h and then fried in frying oil at 150 °C for 1–7 min. Thermal properties of wheat flour, structure alteration, and textural properties of fried samples were evaluated. As compared with samples made of non‐milled flour, samples made from milled flour had smaller pores and higher oil absorption. The fracture force of a fried sample prepared from non‐milled flour was lower than that of a sample prepared from milled flour. CONCLUSION: Ball‐milling affected the microstructure formation in fried wheat flour dough, and subsequently oil absorption. The crispness of a sample prepared from non‐milled wheat flour is higher than that of a sample prepared from ball‐milled wheat flour. This may be due not only to a plasticization effect, but may also be dependent on microstructure. Copyright © 2008 Society of Chemical Industry     

Molecular Oxygen and Reactive Oxygen Species in Bread-making Processes: Scarce,but Nevertheless Important

In bread making, O₂ is consumed by flour constituents, yeast, and, optionally, some additives optimizing dough processing and/or product quality. It plays a major role especially in the oxidation/reduction phenomena in dough, impacting gluten network structure. The O₂ level is about 7.2 mmol/kg dough, of which a significant part stems from wheat flour. We speculate that O₂ is quickly lost to the atmosphere during flour hydration. Later, when the gluten network structure develops, some O₂ is incorporated in dough through mixing-in of air. O₂ is consumed by yeast respiration and in a number of reactions catalyzed by a wide range of enzymes present or added. About 60% of the O₂ consumption in yeastless dough is ascribed to oxidation of fatty acids by wheat lipoxygenase activity. In yeasted dough, about 70% of the O₂ in dough is consumed by yeast and wheat lipoxygenase. This would leave only about 30% for other reactions. The severe competition between endogenous (and added) O₂-consuming systems impacts the gluten network. Moreover, the scarce literature data available suggest that exogenous oxidative enzymes but not those in flour may promote crosslinking of arabinoxylan in yeastless dough. In any case, dough turns anaerobic during the first minutes of fermentation.     

Effect of β-Glucan Concentrate on the Water Uptake,Rheological and Textural Properties of Wheat Flour Dough

The effects of the addition of β-glucan concentrate (2.5–10 g/100 g flour) and water (58–70 mL/100 g flour) on the rheological and textural properties of wheat flour doughs were studied. Various empirical (farinograph, extensograph, dough inflation, and dough stickiness) and fundamental rheological tests (oscillatory and creep-recovery) were employed to investigate composite dough structure and an attempt was made to correlate the data obtained from different instrumental measurements. The water absorption increased with the addition of β-glucan concentrate into wheat flour. An increase in mixing time and stability were recorded upon addition of β-glucan concentrate (≤ 5 g/100 g flour), and the extensibility decreased at similar condition. The composite dough exhibited predominating solid-like behavior. The mechanical strength, dough stickiness, the peak dough inflation pressure decreased with increasing water content but those parameters increased with β-glucan concentrate incorporation within the studied concentration range. Creep-recovery tests for 5 g β-glucan concentrate/100 g flour doughs recorded less resistance to deformation with an increase in water level and data were well described by the Burger model. Thermal scanning of doughs revealed that the protein denaturation peak was significantly influenced by water content, and the values were ranged between 110 and 124°C. Significant relationships between empirical and fundamental rheological testing methods were found.     

Enzymatic Reduction of Phytate in Whole Wheat Breads

The presence of phytate in flour may be responsible for reduced bioavailability of iron, magnesium, zinc, and calcium from bread. The effect of various concentrations of commercial phytase or phosphatase added to whole wheat flour-yeast doughs on their phytate and nonphytate phosphorus content has been investigated. By using 2.0% (flour basis) of phytase and 0.11% phosphatase the initial phytate phosphorus concentration of the dough was reduced to 1/8 and 1/12 of its initial values, respectively. Storage of the whole wheat breads for up to 96 hr at room temperature showed further significant reduction of phytate phosphorus. The phytate phosphorus content of yeast leavened whole wheat breads decreased during 2 hours of dough fermentation, baking and the subsequent 48 hours of storage at room temperature from 24 mg/100g dough (dry matter) to 1.7 mg/100g bread (dry matter); the phytate phosphorus continued to decrease and after 96 hours storage it was 0.6 mg/100g bread.     

Technological Assessment of Chestnut Flour Doughs Regarding to Doughs from Other Commercial Flours and Formulations

The technological assessment of chestnut flour doughs was studied using Mixolab® apparatus, establishing a comparison with gluten (soft, hard and whole wheat) and gluten-free (rice and yellow corn) flour doughs as well as corn starch pastrymaking and breadmaking formulations. This equipment measures the torque in function of temperature and time, firstly at 30 °C (mixing curve) and secondly the mixing during heating (4 °C/min up to 90 °C) and cooling (4 °C/min up to 50 °C) steps (complete curve). Different hydrations of doughs ranging from 41.4% to 68.5% (flour basis) were necessary to reach the torque of 1.10?±?0.07 Nm. Parameters of mixing such as water absorption, development time, stability and mixing tolerance index were obtained. Parameters of heating and cooling cycle related to weakening of proteins, gelatinization starch, amylase activity and starch retrogradation as well as range of gelatinization temperatures were also determined. Chestnut flour showed suitable parameters in the mixing stage such as arrival time (1.93?±?0.1 min), stability (12.1?±?0.4 min) and departure time (14.0?±?0.3 min). In the heating cycle, chestnut flour exhibited close behaviour to soft wheat flour with cooking stability of 1.12?±?0.01 min and seems to be suitable for pastrymaking products. Finally, in the cooling cycle the behaviour revealed that products of this flour can present problems of staling and crumbs firmness due to high values (2.88 Nm) of C5 parameter.     

Low‐ and Medium‐DE Maltodextrins From Waxy Wheat Starch: Preparation and Properties

The goal of the research was to prepare maltodextrins (MD) from waxy wheat starch and waxy corn starch (control). Waxy wheat starches with 0.2% protein, 0.2% lipid and ∼1% amylose were isolated from two flours by mixing a dough, dispersing the dough in excess water, and separating the starch and gluten from the resultant dispersion. The mean recoveries were 72% for the starches and 76% for the gluten fraction with 80% protein. Maltodextrins having low‐dextrose equivalence (DE) 1—2 and mid‐DE 9—10 were prepared by treatment of 15% slurries of waxy wheat starch and waxy corn starch at 95 °C for 5—10 min and 20—50 min, respectively, with a heat‐stable α‐amylase. Denaturing the enzyme and spray‐drying produced MD's with bulk densities of 0.3 g/cm ³. The powdery MD's were subjected to an accelerated‐rancidity development test at 60 °C, and an off‐odor was detected after 2 days storage for the low‐DE MD's from the two waxy wheat starches (WxWS₁‐MD 1.2 and WxWS₂‐MD 1.5), but not for the low‐DE waxy corn maltodextrin (WxCS‐MD 2.2) or a commercial waxy corn MD with DE 1. None of the mid‐DE 9—10 MD's developed off‐odor after 30 days storage at 60 °C. The experimental products WxWS₁‐MD 9.2, WxWS₂‐MD 9.9 and WxCS‐MD 9.1 showed high water‐solubility and gave 1—10% aqueous solutions of high clarity with no clouding upon cooling.