A Study on Staling Characteristics of Gluten-Free Breads Prepared with Chestnut and Rice Flours

The effects of chestnut flour and a xanthan–guar gum blend–DATEM mixture on staling of gluten-free rice breads baked in conventional and infrared–microwave combination ovens were studied. Staling properties of the bread were assessed using mechanical compression (TA), differential scanning calorimetry, X-ray diffraction, and fourier transform infrared spectroscopy (FT-IR). Hardness, moisture loss, and retrogradation enthalpy values for all bread samples increased significantly during storage. FT-IR spectra showed that the integrated area of peaks around 1,041 and 1,150 cm^?1 wave lengths, which are related to the structure of starch retrogradation, increased with storage time. The X-ray diffractograms of aged breads indicated a B-type structure with the appearance of peaks at around 17°, 19.5°, and 22°. An additional peak at 24° was observed in breads stored for longer periods. Higher values of hardness and lower moisture contents were obtained for breads baked in an infrared–microwave combination oven, but the use of infrared–microwave combination oven did not result in excessive hardness after storage. Retrogradation enthalpies and total crystallinity values of breads did not show significant differences with baking type.The replacement of rice flour with chestnut flour and addition of xanthan–guar gum blend–DATEM mixture in formulations significantly delayed staling of gluten-free breads by decreasing moisture loss, hardness, retrogradation enthalpy, and total mass crystallinity.     

Optimisation of formulations and infrared–microwave combination baking conditions of chestnut–rice breads

The main objective of this study was to design gluten‐free breads containing chestnut and rice flour and xanthan–guar gum blend to be baked in infrared–microwave combination oven. Response surface methodology (RSM) was used to optimise gluten‐free bread formulations and processing conditions. Weight loss, firmness, specific volume and colour change of the breads were determined. Rice flour mixed with different proportions of chestnut flour and different emulsifier contents were used to prepare breads. The gluten‐free formulations were baked using different upper halogen lamp powers, microwave powers and baking time which were varied from 40% to 80%, 30% to 70% and 9 to 17 min, respectively. Gluten‐free breads and wheat breads baked in conventional oven were used for comparison. Breads containing 46.5% chestnut flour and 0.62% emulsifier and baked using 40% infrared and 30% microwave power for 9 min had statistically comparable quality with conventionally baked ones.     

Quantitative analysis of macro and micro-structure of gluten-free rice cakes containing different types of gums baked in different ovens

The effects of different gums on macro-structure of gluten-free rice cakes baked in conventional and infrared–microwave (IR–MW) combination ovens were investigated by using the images obtained by scanner and scanning electron microscopy in this study. The gum types used were xanthan, guar, locust bean, κ-carrageenan and xanthan–guar blend. Cake containing no gum was used as control. It was observed that both addition of different types of gums affected the pore area fraction and percent number of pores of the rice cakes. The highest pore area fraction was obtained in cakes containing xanthan and xanthan–guar blend. Cakes baked in IR–MW combination oven had higher porosity than those baked in conventional oven. Micro-structure of gluten-free rice cakes was also analyzed. According to these results, conventionally baked cakes showed more starch granule deformations. Both granular starch residues and deformed starch structure were observed together in cakes baked in IR–MW combination oven. All of the starch granules did not lose their identity and did not disintegrate completely.     

The effects of gums on macro and micro-structure of breads baked in different ovens

In this study, the effects of gums on macro and micro-structure of breads baked in different ovens (infrared (IR)-microwave combination and conventional) were investigated by the help of image and SEM analysis, respectively. The gums used were xanthan, guar, κ-carrageenan and xanthan-guar blend. The gums were added to the formulation at 0.5% concentration. As a control, no gum added formulations were used. Results of Image analysis demonstrated that xanthan-guar gum blend addition improved bread quality with increasing pore area fractions. It was seen that about 75% of the pores of control breads baked in infrared-microwave combination oven and about 63% of the pores of control breads baked in conventional oven had diameters of above 1000 μm. According to SEM analysis, pores in control breads baked in conventional oven were found to be smaller, and had spherical, oval-like shape as compared to the ones baked in IR-microwave combination oven. Moreover, more homogeneous closed-cell structure was observed for conventionally baked control breads. The pores of breads baked in IR-microwave combination oven were so close to each other which resulted in coalescence of the gas cells to form channels, then the pores were no longer spherical. The starch granules in conventionally baked breads were more distorted and seen as a continuous sheet of gelatinized starch. On the other hand, granular residues and continuous starch structure was observed together in IR-microwave combination heating.     

Quality of Gluten-Free Bread Formulations Baked in Different Ovens

The objective of this study was to determine the effects of different tigernut flour/rice flour ratios (0:100, 5:95, 10:90, 15:85, 20:80, and 25:75) on quality of gluten-free bread formulations baked in infrared–microwave combination and conventional ovens. The degrees of the starch gelatinization of breads baked in different ovens were also compared. Conventionally baked breads prepared with tigernut flour/rice flour ratio of 10:90 and the infrared–microwave combination-baked breads prepared with tigernut/rice flour ratio of 20:80 had the most acceptable firmness and specific volume values. These breads had also similar color. Tigernut flour had significantly higher gelatinization temperatures and lower gelatinization enthalpy (ΔH_g) values than rice flour (p?≤?0.05). As rice flour was replaced with tigernut flour, lower ΔH_g values were observed in dough samples. Breads baked in both conventional and combination oven had sufficient starch gelatinization degrees ranging from 91% to 94% and from 84% to 85%, respectively.     

Optimization of Baking of Rice Cakes in Infrared–Microwave Combination Oven by Response Surface Methodology

In this study, response surface methodology was used to design gluten-free cakes made from rice flour to be baked in infrared-microwave combination oven. Two types of cake formulations containing different types of gums were used in the experiments, which were xanthan gum and xanthan–guar gum blend. The independent variables were emulsifier content (0, 3, and 6% of flour weight), upper halogen lamp power (50, 60, and 70%), and baking time (7, 7.5, and 8 min). Specific volume, surface color change, firmness and weight loss of the cakes were determined for optimization. Cakes formulated with xanthan gum had better quality characteristics than cakes containing xanthan–guar gum blend. Cakes formulated with xanthan gum and 5.28% emulsifier and baked using 60% halogen lamp power for 7 min had the most acceptable quality.     

Effects of different emulsifier types,fat contents,and gum types on retardation of staling of microwave‐baked cakes

The effects of different types of emulsifiers, gums, and fat contents on the retardation of staling of microwave‐baked cakes were investigated. First, different types of emulsifiers (DATEM, Lecigran, and Purawave) at three different fat contents (50%, 25%, and 0%) were added to cake formulations to retard staling of microwave‐baked cakes. Then, three types of gums (guar gum, xanthan gum, and methylcellulose) were added to the optimum formulations chosen. As a control, cakes formulated without any emulsifier or gum addition and baked in an conventional oven at 175°C for 25 min was used. Weight loss, firmness, soluble starch and amylose content of the cakes were used as the indicators of staling criteria. Cakes were baked in a microwave oven for 1.5 min at 100% power. Variation of staling parameters during storage of cakes followed zero‐order kinetics. Use of emulsifiers and gums helped to retard staling of microwave‐baked cakes. Fat content was found to be a significant factor in affecting variation of firmness and weight loss of the cakes during storage. DATEM and Purawave were the most effective emulsifier types. Using gums in combination with emulsifiers gave better moisture retention and softer cakes than using gums alone.     

A study on the effects of different gums on dielectric properties and quality of breads baked in infrared-microwave combination oven

In this study, the effects of different gums on dielectric properties of doughs and breads baked in infrared-microwave combination oven were investigated. In addition, the quality parameters of breads formulated with different gums baked in infrared-microwave combination oven were determined. The gums used were xanthan, guar, xanthan-guar blend and κ-carrageenan. The gums were added to the formulation at 0.5% concentration. The dielectric properties and quality parameters of breads baked in infrared-microwave combination oven were found to be dependent on gum type. κ-carrageenan resulted in undesirable final bread quality, while xanthan-guar blend addition improved bread quality (high specific volume and porosity, low hardness values). The dielectric properties of bread samples formulated with κ-carrageenan were found to be the highest among the other gum types.     

Influence of Final Baking Technologies in Partially Baked Frozen Gluten‐Free Bread Quality

The effect of final baking in convection oven (FBC), microwave oven (FBM), and microwave oven with susceptor packaging material (FBMS) on partially baked (PB) frozen gluten‐free bread characteristics was investigated. Specific volume and crust color of loaves were measured at day 0. Bread moisture, water activity, and crumb and crust texture (at 15, 45, and 90 min after baking) were analyzed at day 0 and after 28 d of frozen storage (?18 °C). Volatile compounds from breads baked in convection oven or microwave oven with susceptor packaging material were also evaluated. Bread finally baked in convection oven or in microwave oven with susceptor packaging increased crust browning. Crumb and roll hardness increased with time after final baking (measured at 15, 45, 90 min) and after 28 d of frozen storage. Bread finally baked in microwave oven was the hardest, due to high water losses. At day 0, bread finally baked in convection oven had softer crumb than bread finally baked in microwave oven with susceptor packaging but, after 28 d of frozen storage, there were no differences between them. Moreover, FBC and FBMS rendered gluten‐free breads that could not be distinguished in a triangular test and had the same volatile compounds profile. In conclusion, FBMS could be an alternative to FBC.     

Rheological properties of gluten-free bread formulations

In this study, the rheological properties of rice bread dough containing different gums with or without emulsifiers were determined. In addition, the quality of rice breads (volume, firmness and sensory analysis) was evaluated. Different gums (xanthan gum, guar gum, locust bean gum (LBG), hydroxyl propyl methyl cellulose (HPMC), pectin, xanthan–guar, and xanthan–LBG blend) and emulsifiers (Purawave^™ and DATEM) were used to find the best formulation for gluten-free breads. Rice dough and wheat dough containing no gum and emulsifier were used as control formulations. The rice dough containing different gums with or without emulsifiers at 25 °C showed shear-thinning behavior with a flow behavior index (n) ranging from 0.33–0.68 (except pectin containing samples) and consistency index (K) ranging from 2.75–61.7 Pa sⁿ. The highest elastic (G′) and loss (G″) module were obtained for rice dough samples containing xanthan gum, xanthan–guar and xanthan–LBG blend with DATEM. When Purawave^™ was used as an emulsifier, dough samples had relatively smaller consistency index and viscoelastic moduli values compared to DATEM. The viscoelastic parameters of rice dough were found to be related to bread firmness. Addition of DATEM improved bread quality in terms of specific volume and sensory values.     

The effects of xanthan and guar gums on staling of gluten-free rice cakes baked in different ovens

The objective of this study was to determine the effects of different concentrations of xanthan and guar gums and their blends on staling of gluten-free rice cakes baked in microwave-infrared combination oven (MW–IR) and to compare the cakes with conventionally baked ones. Gums were added at concentrations of 0.3% and 1.0%. For preparation of gum blend, 0.5% xanthan gum was mixed with 0.5% guar gum. In order to understand the staling behaviour of cakes, cakes were stored at 22 ± 2 °C for 120 h. Xanthan-guar gum blend decreased hardness, weight loss, retrogradation enthalpy and the change in setback viscosity values of cakes during storage for both types of ovens as compared to control formulation. It was found that oven type was a significant factor in affecting staling parameters of gluten-free cakes.     

Effects of different emulsifier types,fat contents,and gum types on retardation of staling of microwave-baked cakes

The effects of different types of emulsifiers, gums, and fat contents on the retardation of staling of microwave-baked cakes were investigated. First, different types of emulsifiers (DATEM, Lecigran, and Purawave) at three different fat contents (50%, 25%, and 0%) were added to cake formulations to retard staling of microwave-baked cakes. Then, three types of gums (guar gum, xanthan gum, and methylcellulose) were added to the optimum formulations chosen. As a control, cakes formulated without any emulsifier or gum addition and baked in an conventional oven at 175 degrees C for 25 min was used. Weight loss, firmness, soluble starch and amylose content of the cakes were used as the indicators of staling criteria. Cakes were baked in a microwave oven for 1.5 min at 100% power. Variation of staling parameters during storage of cakes followed zero-order kinetics. Use of emulsifiers and gums helped to retard staling of microwave-baked cakes. Fat content was found to be a significant factor in affecting variation of firmness and weight loss of the cakes during storage. DATEM and Purawave were the most effective emulsifier types. Using gums in combination with emulsifiers gave better moisture retention and softer cakes than using gums alone.     

Optimization of bread baking in a halogen lamp–microwave combination oven by response surface methodology

The main objective of this study was to optimize the baking conditions of bread in a halogen lamp–microwave combination oven. Independent variables were the baking time (4, 4.5, 5, 5.5, and 6 min), the power of the microwaves (20, 30, 40, 50, and 60%), and the power of the upper and lower halogen lamps (40, 50, 60, 70, and 80%). The quality parameters measured were the weight loss, the color, the specific volume, the porosity, and the texture profile of the breads. For the optimization, the response surface methodology was used. Baking time, upper halogen lamp power, and microwave power were found to be significant in affecting most of the quality parameters. On the other hand, the lower halogen lamp power was found to be an insignificant factor. The optimum baking conditions in the halogen lamp–microwave combination oven were determined as 5 min of baking time at 70% upper halogen lamp power, 50% lower halogen lamp power, and 20% microwave power. Breads baked at the optimum condition had comparable quality with conventionally baked ones. When the halogen lamp–microwave combination oven was used, the conventional baking time of breads was reduced by 60%.     

EFFECTS OF BAKING PARAMETERS ON THE WHITE LAYER CAKE QUALITY BY COMBINED USE OF CONVENTIONAL AND MICROWAVE OVENS

The effects of combined conventional and microwave oven baked white layer cake characteristics were studied. Two types of commercially milled wheat flour, white (A) and whole wheat (B), were used. The modified white layer cake making method was used for conducting the cake baking trials. The conventional baking times (8 or 11 min), microwave power (400 or 600 W) and microwave baking time (30, 40, or 50 s) were chosen as baking parameters. Conventional baking was applied to form the cake crust before baking with the microwave oven used to form the crumb of the cakes. The performance of combination baking was compared with the performance of conventional baking. The volume, bake loss, internal factors, and crust color of cakes were evaluated as quality characteristics. The bake losses of cakes using the combination of short oven times and low microwave power for selected microwave times were smaller than the bake losses of the control cakes for both flours. Long oven times and low microwave power increased the specific volume of cakes. Cakes baked from flours A and B exhibited similar internal properties. Oven time significantly affected the crust color of cakes made with flour A. The crust color of cakes made with flour B was similar to the crust color of control cakes. Using a combination of conventional and microwave baking produces cakes with qualities equivalent to the qualities of cakes produced with conventional baking.     

Effects of different formulations on the quality of microwave baked breads

Effects of different amounts of gluten, fat, emulsifier, and dextrose on the quality of breads baked in the microwave oven were investigated. Response surface methodology was used to optimize the formulation of microwave baked breads. Firmness, specific volume, and weight loss of the breads were determined. Breads formulated with low gluten flour were softer and had higher volume. Volume of these breads can be comparable with the volume of conventionally baked breads. For breads formulated with flour containing low gluten, the increase in fat and emulsifier contents decreased the firmness and increased the specific volume of breads. Fat, emulsifier, and dextrose contents were found to be the significant factors to reduce the weight loss of microwave baked breads.     

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.     

Assessment of proofing of bread dough in the microwave oven

 The effects of different proofing times in the microwave oven on the quality of microwave baked breads were investigated. The proofing height of the dough, specific volume and the firmness of the breads were found to be dependent on proofing time. When emulsifiers were added, the optimum proofing condition in the microwave oven was found to be 6 minutes at 10% power. The effects of different emulsifiers on the properties of the dough and, the volume and the firmness of the microwave-baked breads were compared. DATEM, Lecimulthin M-45 and Purawave were the three emulsifiers used. Purawave was found to be the most effective emulsifier on bread quality. Received: 5 July 2000 / Revised version: 6 September 2000     

Acidulant and oven type affect total anthocyanin content of blue corn cookies

BACKGROUND: Anthocyanins, pink to purple water‐soluble flavonoids, are naturally occurring pigments with claimed health benefits. However, they are sensitive to degradation by high pH, light and temperature. Blue corn (maize) contains high levels of anthocyanins. Cookies are popular snacks and might serve as a vehicle to deliver antioxidants. A cookie formula with a high level of blue corn was developed with added acidulents and baked in ovens with different heat transfer coefficients. RESULTS: The best whole‐grain blue corn flour/wheat pastry flour ratio (80:20 w/w), guar gum level (10 g kg^?1, flour weight basis) and water level (215 g kg^?1, flour weight basis) were determined based on response surface methodology analysis. The interactions of citric and lactic acids and glucono‐δ‐lactone with three oven types having different heat transfer coefficients (impingement oven 179 °C/4 min, reel oven 204 °C/10 min and convection oven 182 °C/4 min) influenced the total anthocyanin content (TAC) remaining in blue corn‐containing cookies after baking. CONCLUSION: Cookies baked with citric acid in the convection oven retained the maximum TAC (227 ± 3 mg kg^?1). By baking rapidly at lower temperatures and adding acidulents, it may be possible to increase residual natural source antioxidants in baked foods. Copyright © 2010 Society of Chemical Industry     

Effect of Microwave Radiation Pretreatment of Rice Flour on Gluten-Free Breadmaking and Molecular Size of β-Glucans in the Fortified Breads

Cereal β-glucan concentrates can be used in gluten-free breads to improve dough handling properties and quality of final products as well as to enhance their nutritional value; however, the presence of endogenous β-glucanases in rice flour, in combination with prolonged mixing, fermentation, and proofing time, can cause a substantial reduction in β-glucan molecular weight, affecting detrimentally their efficacy for bioactivity. In this study, microwave (MIWA) heating was applied to the rice flours before breadmaking at different flour water contents (13–25%) and treatment times (0-4 min) to reduce β-glucanase activity. Gluten-free breads made from the MIWA-treated rice flours were fortified with oat β-glucan concentrate to enhance their nutritional profile. The molecular weight of added β-glucan in the final products increased with increasing both flour water content and time of MIWA treatment, reflecting the magnitude of residual β-glucanase activity in the flour. Pretreatment with MIWA radiation for 4 min of the rice flour tempered at 25% moisture resulted in negligible residual β-glucanase activity and preserved to a great extent the molecular weight of β-glucans in the enriched breads. End-product quality was not affected by flour MIWA pretreatment, and even a slightly higher loaf specific volume was noted for breads made from the MIWA-treated flours (4 min MIWA at 25% moisture content) compared to that of untreated flour. These findings can contribute to the improvement of nutritional value of rice-based gluten-free breads for celiac consumers as well as of any β-glucan-containing yeast-leavened bakery product without altering its sensorial attributes. Additional studies are still required for further evaluation of the effect of more intense microwave treatment on rice flour and its application on breadmaking.