Electrophoretic analysis of wheat and rye mixtures in meal,flour and baked goods

Starch gel electrophoresis of endosperm prolamines extracted with 2 M urea, provides distinction between varieties of either wheat or rye, but the major differences in general pattern type between all rye samples and all wheat samples offers a basis for distinction between the two cereals. The proportions of wheat and rye in a mixture can be determined by comparing relative areas of densitometric scans for standard mixtures with that of a sample for analysis, or by direct calculation from area ratios for pure wheat and rye. For baked products, extraction with urea containing a reducing agent is recommended. Electrophoretic patterns are altered both as a result of baking and of using the reducing agent, but distinction between wheat and rye is still possible.     

Protein profile and sensorial properties of rye breads

The protein profile of four types of traditional rye breads formed on rye flours with the extraction rate of 100, 95, 85 and 70% and baked at 260 °C for 40 min was investigated as a nutritional quality indicator. A fractionation process was applied to discriminate high-molecular- (HMW >3 kDa) and low-molecular weight compounds (LMW <3 kDa) present in extracts of rye bread and its crumb and crust. The content of soluble proteins, available lysine, carbohydrates and total phenolic compounds was analysed before and after ultrafiltration in both retentates (HMW >3 kDa) and filtrates (LMW <3 kDa). The dependence between sensory quality of rye breads and composition on soluble proteins, available lysine, carbohydrates and total phenolic compounds was provided. Baking caused a decrease in rye bread protein content. The content of available lysine was the lowest in crusts and it was dependent on the rye flour extraction rate taken for rye bread making. The SDS-PAGE analysis showed that the primary structure of the rye bread proteins was modified in the highest extent in the crust’s bread of all types. The analyses of both retentates and filtrates after ultrafiltration demonstrated that the most of carbohydrates and phenolic compounds were incorporated into the HMW fraction suggesting their conjugation with proteins due to the Maillard reaction. Compounds able to react with Folin Ciocalteu reagent were also detected in filtrates of crust’s extracts (MW ≤3 kDa) from all breads indicating their distribution between LMW and HMW fractions. About 22.5, 27, 11.2 and 46.8% of the phenol compounds forming crusts of breads based on the flours with extraction rates of 100, 95, 85 and 70% were recovered in the corresponding LMW fractions.The sensory analysis of the four types of rye breads indicated for a high correlation between overall quality of breads and their content of carbohydrates. The highest correlation was noted for a rye bread formed on flour with extraction rate of 95%. This finding suggested that the content of carbohydrates as a substrate for Maillard reaction has had an influence on palatability by consumers of rye bread formed on flour with the extraction rate of 95% which had also the highest overall quality.     

Furosine is a useful indicator in pre‐baked breads

There is increasing demand for pre‐baked bread. Bakers can meet consumer requirements for breads of specific flavour and colour by pre‐baking an amount of bread in the morning and completing the baking process in the afternoon. This type of product is of special interest to sandwich bars, restaurants and large communities. In order to obtain an indicator of utility to monitor the processing of pre‐baked bread, the browning indicators furosine, hydroxymethylfurfural (HMF) and glucosylisomaltol were analysed in two independent assays of bread pre‐baked at 175 °C for between 5 and 30 min. No furosine was detected in raw or fermented dough. In the pre‐baking stage, furosine increased from 1.5‐ to 5‐fold between 5 and 30 min. The furosine values obtained in the two independent experiments were similar. HMF and glucosylisomaltol were only detected after 15 min, which is the time period commonly used for processing by the industry. Thus, among these indicators, furosine is the only one with utility for monitoring the pre‐baking process. On the other hand, a study of the baking of pre‐baked bread at 220 °C showed that HMF and glucosylisomaltol can be used to monitor the latter process. Copyright © 2004 Society of Chemical Industry     

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.     

感受器辅助微波烘焙的面包性质研究

分别以传统烤箱和微波炉加热为参照,研究了感受器辅助微波对面包烘焙过程中的温度变化、质量损耗、比容、面包芯水分分布、硬度、质构及感官特性的影响,结果表明,与传统微波对照组相比,面包外部温度提高18.80%,内部温度降低15.71%,质量损耗降低2.05%,比容提高18.00%~23.35%,面包芯水分含量提高7.10%~27.42%,硬度值降低80.81%~85.52%,质构和感官特性得到有效改善;但与传统烤箱对照组相比,还有待改进。      

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.     

Investigation of physicochemical properties of breads baked in microwave and infrared-microwave combination ovens during storage

Staling of breads baked in different ovens (microwave, infrared-microwave combination and conventional) was investigated with the help of mechanical (compression measurements), physicochemical (DSC, X-ray, FTIR) and rheological (RVA) methods. The effect of xanthan-guar gum blend addition on bread staling was also studied. Xanthan-guar gum blend at 0.5% concentration was used in bread formulation. The gums were mixed at equal concentrations to obtain the blend. After baking, the staling parameters of breads were monitored over 5 days storage. During storage, it was seen that hardness, retrogradation enthalpies, setback viscosity, crystallinity values, and FTIR outputs related to starch retrogradation of bread samples increased, whereas FTIR outputs related to moisture content of samples decreased significantly with time. The hardness, retrogradation enthalpy, setback viscosity, and crystallinity values of microwave-baked samples were found to be highest among other heating modes. Using IR-microwave combination heating made it possible to produce breads with similar staling degrees as conventionally baked ones in terms of retrogradation enthalpy and FTIR outputs related to starch retrogradation. Addition of xanthan-guar gum blend decreased hardness, retrogradation enthalpy and total mass crystallinity values of bread samples showing that staling was delayed.     

Consumer liking of refined and whole wheat breads

ABSTRACT:  Preference for refined bread is often cited as a reason for the relatively low consumption of whole wheat bread; only a few studies, however, have examined consumer preferences between refined and whole wheat breads, and the results of these studies are inconclusive. Our objective was to determine if refined wheat bread is preferred to whole wheat bread. We hypothesized that people would prefer refined wheat bread. We conducted a taste test with 89 people. They rated their liking of 9 different breads chosen to represent several comparisons between equivalent refined and whole wheat breads. The participants also rated the intensity of 6- n -propylthiouracil (PROP) and completed a questionnaire about their bread preferences and purchasing habits. We classified the participants by their bread preference and their PROP taster status, and then examined the liking patterns of these subgroups. People preferred refined bread to whole wheat bread when both were made using equivalent ingredients and procedures. They liked the commercial samples of refined and whole wheat breads equally well. When people were classified by their bread preference, those who preferred refined bread liked the refined bread better in all comparisons. PROP nontasters liked all refined and whole wheat breads equally. Sensory preferences are a barrier to whole wheat bread consumption, but ingredient or processing modifications can improve liking of whole wheat bread to the level of refined bread.     

A quality comparison of breads baked by conventional versus nonconventional ovens: A review

Undesirable qualities of breads baked in nonconventional ovens have been observed by most researchers. The altered heat and mass transfer patterns and much shorter baking times associated with microwave radiation resulted in a crustless product with tougher, coarser, but less firm texture. Insufficient starch gelatinization, microwave-induced gluten changes, and rapidly generated gas and steam caused by the heating mode could be reasons for quality changes in the microwave-baked breads. Although breads baked in an electrical resistance oven did not brown, their interior characteristics and shelf-life were superior to those of products baked in a conventional oven. Bread with a superior keeping quality was obtained using an air impingement convection oven. The determination and explanation of the physical and biochemical changes that occur in products during baking in conventional versus nonconventional ovens are fruitful areas for future research.     

Macromolecular structure of water-extractable arabinoxylans in endosperm and wholemeal rye breads as factor controlling their extract viscosities

Viscosity is one of the most important attributes of rye-based products related to some health benefits. To identify the factors affecting arabinoxylan-dependent extract viscosity (AX-EV) of rye bread, the structural features of water-extractable arabinoxylans (WE-AXs) and their ammonium sulphate precipitated subfractions were investigated in breads with varied viscosities. Also, an endoxylanase activity in the starting flours was examined. The HPSEC-RI profiles revealed the higher extent of AX depolymerisation in whole-meal bread (WMB) when compared to that in endosperm bread (EB), resulting in its lower AX-EV. This was mostly related to lower molecular weight of the parent WE-AX fraction with distinctly lower proportion of 2-Xylp in the chain. The AX-EV of rye bread decreased with decreasing proportion of AX-I, the major subfraction with 3-Xylp as only branching site. The endoxylanase activity was at least two times lower in endosperm flour than that in WM and negatively correlated with the AX-EV of WMB. The importance of densely substituted AX subfractions with exclusively 2-Xylp and 2,3-Xylp branches, protecting the AX-I from enzymic degradation during bread-making, has been evidenced.     

Homogeneities in in vitro starch digestion of compositionally heterogenous white wheat breads

In vitro starch digestion of five fresh and shelved white wheat breads, compositionally heterogeneous, was investigated for heterogeneities or homogeneities in digestion patterns. The breads were significantly different (P ≤ 0.05) in some chemical and functional properties. The Rapid Visco-Analyser (RVA) revealed different pasting properties in the breads, but the breads showed monophasic starch digestograms, as there were no practical slope changes or discontinuities in the digestograms. The monophasic starch digestograms were suitably described (r² > 0.90; P ≤ 0.05) by five starch digestion kinetic models (the modified first-order kinetic, Peleg, Paolucci-Jeanjean, Logistic, and Weibull), and their parameters were mainly non-significant (P > 0.05) between the breads. The heterogeneous breads were, therefore, homogeneous in their in vitro starch digestion patterns. The study also strengthens a novel modelling approach for starch digestograms to be widely used in starch digestion research, easing inter-laboratory comparisons.     

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.     

Enzymatic extraction of protein from toasted and not toasted soybean meal

The soybean is one import font of vegetable protein, that contains whole the essential amino acids to the human organism. The enzymatic process is a alternative for the protein extraction and offer advantages. In this work, two commercial proteases, Alcalase and Flavourzyme, are used to extract protein from toasted and not toasted degreased soybean meal. The tests (duplicate) are carried out in 40 °C, initial pH of 7,0, enzyme concentration of 1% (protein/protein) and times from 1 up to 24 hours. At the end of the hydrolysis the suspension pH is measured and again corrected for 7,0.     

Nutritional and sensory evaluation of wheat breads supplemented with oleic-rich sunflower seed

Wholegrain and refined (white) wheat breads were prepared with the addition of high-oleic sunflower seed at various levels (8%, 12%, 16% flour basis). The nutritive value of breads was determined by measuring the chemical composition, including the mineral content, the fatty acid composition (saturated, monounsaturated, polyunsaturated, linoleic and linolenic acids) and the contents of tocopherols (α-, β-, γ-, δ-). The obtained data were used to estimate the intakes of nutrients and compare them to the dietary reference intakes (DRIs). The breads made with the addition of sunflower seed were sensorially acceptable, containing significantly more tocopherols, fat, essential fatty acids, crude fibre, copper and zinc. It was estimated that wholegrain supplemented breads would contribute to the corresponding DRIs in the range 33.7–40.8% (adults) for copper and 4.7–18.4% (males), i.e. 6.4–25.3% (females) for zinc, 18.3–26.8% (males), i.e. 25.9–37.9% (females) for linoleic (omega-6) acid, 7.4–7.6% (males), i.e. 10.7–11.0% (females) for alpha-linoleic (omega-3) acid.     

Effect of bioprocessing of wheat bran in wholemeal wheat breads on the colonic SCFA production in vitro and postprandial plasma concentrations in men

The health benefits of whole grain consumption can be partly attributed to the inclusion of the bran or outer-layers of the grain rich in dietary fibre. Fibre is fermented in the colon, leading to the production of beneficial metabolites, such as short-chain fatty acids (SCFA). The effect of five different types of bread on the SCFA production was studied in an in vitro model of human colon. Additionally, the postprandial effects of two selected breads on the SCFA plasma concentrations were investigated in men. A higher in vitro production of butyrate was induced by wholemeal wheat bread with bioprocessed bran than by native bran. The increase in butyrate seemed to be in exchange for propionate, whilst the total SCFA production remained similar. However, differences between the two breads in the postprandial butyrate concentrations could not be detected in peripheral blood of men, probably due to an effective utilisation by colonocytes.