Effect of protease treatment on the baking quality of brown rice bread: From textural and rheological properties to biochemistry and microstructure

Understanding gluten-free dough for reaching breads with physical quality and nutritional balance

In the last decade the development of gluten-free foodstuffs has attracted great attention as a result of better diagnoses of coeliac disease and a greater knowledge of the relationship between gluten-free products and health. The increasing interest has prompted extensive research into the development of gluten-free foodstuffs that resemble gluten-containing foods. This review aims to provide some insights on dough functionality and process conditions regarding bread quality and to point out recent research dealing with the nutritional composition of those products. Gluten-free dough results from the combination of different ingredients, additives, and the processing aids required for building up network structures responsible for bread quality. Some relationships between dough rheology and bread characteristics were established to identify possible predictor parameters. Regarding bread-making processes, the impact of mixing, dough treatment and baking is stated. Nutritional quality is an important asset when developing gluten-free breads, and different strategies for improving it are reviewed. Gluten-free bread quality is dependent on ingredients and additives combination, but also processing can provide a way to improve bread quality. Nutritive value of the gluten-free breads must be always in mind when setting up recipes, for obtaining nutritionally balanced bread with adequate glycaemic index.

Germination of oat and quinoa and evaluation of the malts as gluten free baking ingredients

Germination can be used to improve the sensory and nutritional properties of cereal and pseudocereal grains. Oat and quinoa are rich in minerals, vitamins and fibre while quinoa also contains high amounts of protein of a high nutritional value. In this study, oat and quinoa malts were produced and incorporated in a rice and potato based gluten free formulation. Germination of oat led to a drastic increase of α-amylase activity from 0.3 to 48 U/g, and minor increases in proteolytic and lipolytic activities. Little change was observed in quinoa except a decrease in proteolytic activity from 9.6 to 6.9 U/g. Oat malt addition decreased batter viscosities at both proofing temperature and during heating. These changes led to a decrease in bread density from 0.59 to 0.5 g/ml and the formation of a more open crumb, but overdosing of oat malt deteriorated the product as a result of excessive amylolysis during baking. Quinoa malt had no significant effect on the baking properties due to low α-amylase activity. Despite showing a very different impact on the bread quality, both malts influenced the electrophoretic patterns of rice flour protein similarly. This suggests that malt induced proteolysis does not influence the technological properties of a complex gluten free formulation.

Rheological Innovations for Characterizing Food Material Properties

Rheological methods are continually evolving to encompass novel technologies and measurement methods. This review highlights novel techniques used to analyze the rheological properties of foods over the previous decade. Techniques reviewed include large amplitude oscillatory shear (LAOS) testing and rheological techniques coupled with other measurement methods, such as microscopy and nuclear magnetic resonance (NMR). Novel techniques are briefly overviewed and discussed in terms of advantages and disadvantages, previous use, and suggested future utilization.

Physicochemical properties and consumer acceptance of wheat-germinated brown rice bread during storage time

Selected physicochemical properties and consumer acceptance of bread prepared from composite flour (wheat:germinated brown rice:germinated glutinous brown rice flours at 60:30:10 ratio) were evaluated during storage for 0, 3, and 5 d, and compared with wheat bread (0 d, control). During storage, color profiles and water activity (from 0.947 to 0.932) of crumbs of composite flour breads slightly changed, but moisture content drastically decreased along with increasing crumb hardness (from 4.16 N to 10.37 N). Higher retrogradation in bread crumb was observed particularly for 5-d stored bread (DeltaH = 2.24 J/g) compared to that of the fresh composite bread and the control (DeltaH = 0.70 and 0.51 J/g, respectively). Mean (n = 116) overall liking score of the fresh composite flour bread (0 d) was slightly lower than that of the control (7.1 compared with 7.6 based on a 9-point hedonic scale). At least 76% of consumers would purchase the fresh composite flour bread if commercially available. Breads were differentiated by textural (moistness, smoothness, and softness) acceptability with canonical correlation of 0.84 to 0.87. The signal-to-noise ratio values of the 5-d stored breads were lower than the control, due mainly to the non-JAR (not-enough) intensity responses for moistness, smoothness, and softness; the mean drop of liking scores for these attributes ranged from 2.42 to 2.98. Flavor acceptability and overall liking were factors influencing consumers' purchase intent of composite flour breads based on logistic regression analysis. This study demonstrated feasibility of incorporating up to 40% germinated brown rice flour in a wheat bread formulation. Practical Application: Our previous study revealed that flours from germinated brown rice have better nutritional properties, particularly gamma-aminobutyric acid (GABA), than the nongerminated one. This study demonstrated feasibility of incorporating up to 40% germinated brown rice flour in a wheat bread formulation. In the current U.S. market, this type of bread may be sold as frozen bread that would have a longer shelf life, or may be supplied as a food-service product that would be made-to-order or made fresh daily as currently practiced in some major grocery stores.

Improvements in the bread-making quality of gluten-free rice batter by glutathione

The wide prevalence of celiac disease and wheat allergy has led to a growing demand for gluten-free foods. Rice proteins do not possess the viscoelastic properties typically found in gluten, thus making rice flour unsuitable for the production of yeast-leavened products. In the present study, we found that the addition of glutathione to rice batter improves its gas-retaining properties. Glutathione was found to prevent the formation of the disulfide-linked macromolecular protein barrier, which is reported to confer resistance to the deformation of rice batter in the baking process. Also, glutathione appeared to gelatinize rice starch at lower temperatures. Microstructure analyses of glutathione-added rice bread revealed it to have a perforated structure like wheat bread but with a smoother-looking surface. These data collectively suggest that glutathione facilitates the deformation of rice batter, thus increasing its elasticity in the early stages of bread baking and the volume of the resulting bread.

Sourdough in gluten-free bread-making: an ancient technology to solve a novel issue?

The increasing demand for high quality gluten-free (GF) bread, clean labels and natural products is raising the need for new approaches in GF bread-making. Sourdough is the foremost fermentation used for baking purposes and it has been proven to be ideal for improving the texture, palatability, aroma, shelf life and nutritional value of wheat and rye breads. These characteristic features derive from the complex metabolic activities of the sourdough-resident lactic acid bacteria and yeasts, e.g. acidification, production of exopolysaccharides, proteolytic- amylolytic- and phytase activity, and production of antimicrobial substances. These effects have been extensively studied and well described for traditional baking, whereas little is known about the role of sourdough in GF baking. Yet, the microbiological and qualitative characterisation of local GF fermented products indicate an overlap with the microbiota of wheat/rye fermentation and suggest that the positive metabolic activities of the sourdough microbiota are still retained during fermentation of GF crops. Thus, the use of sourdough in GF baking may be the new frontier for improving the quality, safety and acceptability of GF bread.