Effect of dietary fibre on dough rheology and bread quality

Dietary fibre is a common and important ingredient of a new generation of healthy food products demanded more each day by customers. Dietary fibre increases the nutritional value of bread but usually at the same time alters rheological properties of dough and, finally, the quality and sensorial properties of bread. The present work investigates the effect of some purified dietary fibres from different origins (orange, pea, cocoa, coffee, wheat and microcrystalline cellulose) on the rheological properties of wheat flour dough and the final quality of breads. The study of the rheological behaviour of the dough was performed by means of a consistograph and an alveograph. Bread quality was determined by means of texture, colour and specific volume measurements after baking under controlled conditions. The influence of fibre on bread sensory evaluation was established. Dietary fibre additions, in general, had pronounced effects on dough properties yielding higher water absorption, mixing tolerance and tenacity, and smaller extensibility in comparison with those obtained without fibre addition (in the control bread). Regarding the effect on bread properties, the fibre always enhanced the shelf life, as textural studies revealed. Sensory evaluations revealed that dietary fibres, with the exception of those from coffee and cocoa, can be added to flour at the level of 2% without deterioration of the bread palatability in comparison with white flour bread. Additions of 5% could imply the use of some additives to correct the rheological properties of dough.     

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.     

Determination of vitamins A and E in cooked sausages

A reliable and sensitive reverse-phase HPLC method is described for the separation and quantification of all-trans-retinol and dl-α-tocopherol in cooked sausages. Samples were chromatographed with UV and fluorescence detection on a 15 cm × 0.4 cm i.d. Spherisorb ODS-2, 5 μm column, using as mobile phase a mixture of 90% acetonitrile and 10% tetrahydrofuran. Sample preparation included saponification and extraction by n-hexane. Addition of pyrogallol and oxygen-free conditions avoided oxidation of both vitamins, increasing recovery percentages, which ranged from 90.0 to 95.0%. Precision was 1.0% (within a day) and 3.4% (between days) for all-trans-retinol and 1.1% (within a day) and 2.6% (between days) for dl-α-tocopherol. Detection limits were 10 μg/100 g for all-trans-retinol and 0.1 mg/100 g for dl-α-tocopherol with a signal-to-noise ratio of 3. Twenty samples of six different products were analyzed in duplicate. Average for all-trans-retinol in “enriched chopped” was 108 mg/100 g fresh weight, and the mean value for dl-α-tocopherol in “enriched chopped” was 2.3 mg/100 g fresh weight.     

A new family of BiO(ClxBr1 − x) visible light sensitive photocatalysts

A new family of BiO(Cl_xBr_1 − x) photocatalysts have been synthesized by a hydrothermal method. The photocatalytic activity of the new material was measured on the degradation of Rhodamine B (RhB) and Acetophenone (AP) and photooxidation of potassium iodide in water under UV–vis and visible light (λ ≥ 420 nm) irradiations. In comparison to Degussa P25, the new photoactive material with x = 0.5 demonstrated 3 times higher rate in removing aqueous RhB under visible light irradiation. A morphology, chemical composition and crystalline structure of BiO(Cl_xBr_1 − x) were characterized using scanning electron microscopy and powder X-ray diffraction. The values of their unit cell parameters depend on Cl/Br ratio and they change according to the Vegard's law.     

Rheological study of layer cake batters made with soybean protein isolate and different starch sources

The study of new gluten-free foods suitable for celiac people is necessary since people allergic to wheat proteins are more and more frequent. This study examined the effect of using different starch sources (rice, corn, potato and wheat) and protein types (soy protein isolate, wheat protein) at different percentages (0%, 10%, 20%), on the rheological properties of batters (flow, viscoelastic and stickiness behaviour) and on batter density and cake volume. The highest consistency, viscous and elastic moduli, and adhesive force corresponded to batters made of rice starch and soy protein isolate, which showed the most similar rheological behaviour to wheat flour batters. The batters obtained showed adequate characteristics in processing and in achieving high quality products. However, the percentages of starches and proteins should be experimentally optimized in each case.     

Compact lowpass filters with very sharp transition bands based on open complementary split ring resonators

It is shown that open complementary split ring resonators (OCSRRs) are useful particles for the design of lowpass filters with very narrow transition bands in microstrip technology. Owing to the small electrical size of OCSRRs, the filters are also very small. These filters are implemented by cascading several OCSRR stages in a microstrip line. The OCSRR stages can be modelled as parallel resonators in series configuration, thus providing a transmission zero at their resonance frequency. By designing the OCSRRs with small inductance and high capacitance, very sharp cutoffs are achieved. To illustrate the possibilities of the approach, a prototype device example is provided. It consists on a five-stage periodic microstrip lowpass filter with 3 dB insertion losses at 1.33 GHz and 40 dB rejection at 1.45 GHz. To improve out-of-band rejection, four additional OCSRR stages tuned at the spurious frequency band have been cascaded. Filter dimensions are 39 x 7.4 mm (i.e. 0.46l x 0.087l, where l is the guided wavelength at the cutoff frequency). These filters are of interest in applications where small size and severe cutoff requirements are required.     

Effect of fermentation conditions on bread staling kinetics

The effects of yeast dose, temperature and fermentation time on bread volume, bread density, bread texture (firmness, cohesiveness, resilience, springiness and gumminess) and their change during staling were analysed. Thus, changes in the texture profile (TP) parameters as bread aged were modelled and their initial values and their variation rate were obtained. In white and whole breads, the longer the fermentation time and the higher the yeast dose, the lower the firmness and the firming rate. The fermentation temperature only affected the initial firmness in whole breads. Significant linear correlations were found between bread density and volume (r ² = 0.94 in white bread; r ² = 0.96 in whole bread), between density and the initial firmness (r ² = 0.88 in white bread; r ² = 0.61 in whole bread), and between the first two parameters and the firming rate. Between density and firming rate r ² obtained was 0.72 in white bread and 0.32 in whole bread and between volume and firming rate r ² obtained was 0.58 in white bread and 0.29 in whole bread.     

Functionality of different emulsifiers on the performance of breadmaking and wheat bread quality

Emulsifiers are widely used in bakeries as dough strengtheners and crumb softeners, but there is a great diversity of compounds with emulsifier action. The objective of this study was to analyze the influence of emulsifiers with different functionalities on the rheological characteristics of wheat dough, as well as their effect in the final bread parameters, including behavior during aging. All the emulsifiers tested increased dough stability, although the extent of this effect was concentration-dependent. The presence of emulsifier retarded dough proofing; in consequence, longer proofing times would be required when emulsifiers are used. In fact, the positive effects of emulsifiers on bread volume were only observed with long proofing times, and that also became evident when crumb hardness was analyzed. Sodium stearoyl lactylate, sucrose ester, lecithin and enriched lecithin were the emulsifiers with the greatst crumb softening effects at extended proofing times. However, when the objective is a hardening delay during storage, the emulsifiers of choice are monoglyceride and lecithin enriched in lysophospholipids. This study reveals the importance of the proofing period to the functionality of the emulsifiers when used for breadmaking performance.