Sensory tools for the development of gluten-free bakery foods

The appearance, taste, aroma and texture of food products, including gluten-free bakery products, is very important predictors for whether or not such products would be acceptable for consumers. Food companies that manufacture and supply gluten-free food and beverage products need to utilise a variety of sensory tools for decision making during product development, evaluation of ingredients, processes and products. The six steps to Sensory Evaluation process is a simple to use, stepwise approach to select the right tools to answer questions. Different sensory evaluation tools are used to address questions of the three different types (1) Are two or more products the same or different? (2) What is the nature and size of differences among products? and (3) What are consumers' opinions about a product/s? It is the intention that the discussion in this review would stimulate ideas for application of more advanced sensory tools to further understanding to enhance development of gluten-free foods and ingredients. Some suggestions for future sensory studies on gluten-free bakery products are presented. These include: more research on the acceptance and perception of the sensory properties of gluten-free product options by both coeliac and non-coeliac consumers at different life stages; and evaluation of the sensory properties of gluten-free products in combination with other products, accompaniments and within meals. Also, sensory profiling of the unique properties of naturally gluten-free bakery products, as well as studies to optimize acceptance of these in wider consumer markets. The application of the tools in a systematic manner based on the six steps to sensory testing process presented here will assist researchers to obtain powerful results to answer research questions.     

Chemical Composition and Starch Digestibility of Different Gluten-free Breads

The increasing demand for gluten-free products has favoured the design of numerous gluten-free bakery products which intended to mimic the quality characteristics of wheat bakery products. The objective of this study was to evaluate the nutritional pattern of gluten-free breads representative of the Spanish market for this type of products. The protein, fat and mineral content of the gluten-free breads showed great variation, ranging from 0.90 to 15.5 g/100 g, 2.00 to 26.1 g/100 g and 1.10 to 5.43 g/100 g, respectively. Gluten-free breads had very low contribution to the recommended daily protein intake, with a high contribution to the carbohydrate dietary reference intake. Dietary fiber content also showed great variation varying from 1.30 to 7.20 g/100 g. In vitro enzymatic hydrolysis of starch showed that the most predominant fraction was the rapidly digestible starch that varied from 75.6 to 92.5 g/100 g. Overall, gluten-free breads showed great variation in the nutrient composition, being starchy based foods low in proteins and high in fat content, with high glycaemic index.     

Cereals for developing gluten-free products and analytical tools for gluten detection

Recently, gluten free foods have attracted much research interest motivated by the increasing market. Despite the motivation for developing gluten-free foods it is necessary to have a scientific basis for developing gluten-free foods and the tools for detecting the peptide sequence that could be immune-toxic to some persons. This review will be focused primarily on the cereal-based commodities available for developing gluten free blends, considering naturally gluten-free cereals in addition to oats, and recent transgenic approaches for developing cereals free of immunotoxic gluten. Secondly, the biochemical tools for mimicking gluten network viscoelastic properties will be presented. Finally, special emphasis will be put in compiling the available techniques for gluten detection and quantitation.     

Improvement in gluten-free rice bread quality by protease treatment

The wide prevalence of gluten-related disorders has led to increase in the demand for gluten-free foods. Rice is a gluten-free and less allergenic cereal. However, bread made from rice flour, i.e., gluten-free rice bread, is generally of poor quality because rice flour cannot develop a network with gluten-like properties. In this study, we investigated the effects of protease treatment on gluten-free rice to improve the quality of its bread. Bread treated with a commercial protease from Bacillus stearothermophilus (thermoase) was of higher quality, i.e., good crumb appearance, high volume, and soft texture, depending on the amount of enzyme added. Rice proteins in the protease-treated bread were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, which showed that glutelins and prolamins were hardly digested by thermoase in comparison with other proteins. Scanning electron microscopy revealed that many cellular structures were formed in the thermoase-treated bread; however, these structures were rare in the untreated control. Bread crumb color was not affected by the treatment. The staling rate was much lower for the thermoase-treated bread than for the control. These results indicate that thermoase treatment can be successfully used to improve the quality of gluten-free rice bread by partial digestion of rice proteins.     

Gluten-Free Breads and Cookies of Raw and Popped Amaranth Flours with Attractive Technological and Nutritional Qualities

Gluten-free bakery foodstuffs are a challenge for technologists and nutritionists since alternative ingredients used in their formulations have poor functional and nutritional properties. Therefore, gluten-free bread and cookies using raw and popped amaranth, a grain with high quality nutrients and promising functional properties, were formulated looking for the best combinations. The best formulation for bread included 60–70% popped amaranth flour and 30–40% raw amaranth flour which produced loaves with homogeneous crumb and higher specific volume (3.5 ml/g) than with other gluten-free breads. The best cookies recipe had 20% of popped amaranth flour and 13% of whole-grain popped amaranth. The expansion factor was similar to starch-based controls and the hardness was similar (10.88 N) to other gluten-free cookies. Gluten content of the final products was around 12 ppm. The functionality of amaranth-based doughs was acceptable although hydrocolloids were not added and the final gluten-free products had a high nutritional value.     

Characterisation of gluten-free pasta through conventional and innovative methods: Evaluation of the uncooked products

Formation of a gluten protein network is fundamental for the texture and the overall quality of pasta. Replacement of the gluten network in gluten-free pasta is a major technological challenge, and the conventional technological processes have to be adapted to non-gluten formulations. The wide variety of raw materials and technologies used in the production of commercial gluten-free pasta stems from the – still on-going – search for solutions to these problems. The aim of this study was to evaluate the characteristics of different commercial gluten-free spaghetti currently available on the market, focusing on starch and protein organisation. Taking into account the chemical and biochemical properties of the samples, and their relationships to the physical characteristics of these products we looked at how some molecular properties relate to the final structure and quality of gluten-free pasta. Phenomena related to starch retrogradation were found to play a central role for the final texture of the products. At the same time, the origin of proteins included in the formulation was found to govern the protein–protein interactions, especially in those samples including proteins from different vegetable sources.     

Consumers’ acceptance of optimized gluten-free sorghum-based cakes and their drivers of liking and disliking

Sensory analysis is indispensable in order to promote the project of developing sorghum-based products and, therefore, work on sensory profiles of these products and consumer acceptance is needed to help them succeed. Thus, this study investigated the acceptance of 5 optimized gluten-free sorghum-based and a Reference (with gluten) cakes (prepared from cake premixes), considering their drivers of liking and disliking and their purchase intention. Chocolate and orange flavored gluten-free cakes were prepared based on the numerical optimizations of the formulations (technological, nutritional, functional, technological and nutritional, and technological and functional optimizations). Three sensory evaluation techniques were applied to cakes: acceptance testing, purchase intention and Check-all-that-apply. There was an improvement in the sensory properties of the gluten-free samples in which the nutritional or functional characteristics were optimized together with the technological characteristics, resulting in higher acceptances. It was confirmed that sensory studies are indispensable to confront the challenge of developing sorghum-based foods with sensory characteristics desired by consumers. Therefore, it is concluded that it was possible to offer a gluten-free cake premix that presents good sensory quality, having the potential to be offered as a novelty by the food industry, given that most consumers stated that they did not know sorghum.     

Analysis of barley contamination in oats using R5 and ω-gliadin antibodies

Immunological methods based on monoclonal antibodies with varying specifities towards gluten proteins have been used to control the purity of gluten-free products. Commercially available methods have been developed to detect gluten proteins found in wheat. However, difficulties have occurred in quantifying barley proteins with the same accuracy as wheat proteins. Barley is also a common contaminant in oat products. In this study, oat flour samples were deliberately contaminated with known amounts of barley flour and analysed using two commercial enzyme linked immunosorbent assays (ELISA). The methods were based on an ω-gliadin antibody and an R5 antibody. The results obtained with the R5 antibody were overestimates while the ω-gliadin antibody underestimated the higher barley prolamin content. This study showed that inaccuracies in ELISA assays in quantifying barley contaminations can possibly be eliminated by using a hordein standard. However, it is necessary to know the source of contamination. This would prevent overestimation of the hordein content of gluten-free products. Overestimation unnecessarily reduces the variety of gluten-free products and may decrease compliance to a gluten-free diet.     

Manufacture and characterization of pasta made with wheat flour rendered gluten-free using fungal proteases and selected sourdough lactic acid bacteria

Wheat flour, which was rendered gluten-free by sourdough lactic acid bacteria fermentation and fungal proteases, was used for manufacturing experimental gluten-free pasta (E-GFp), according to a traditional process with low temperature drying cycle. Chemical, technological, structural, nutritional and sensory features were characterized and compared with those of commercial gluten-free (C-GFp) and durum wheat pasta (C-DWp). As shown through immunological analyses, the residual concentration of gluten of the hydrolyzed wheat flour was below 10 ppm. E-GFp showed rapid water uptake and shorter optimal cooking time compared to the other pastas. Despite the absence of the gluten network, the supplementation with pre-gelatinized rice flour allowed structural properties of E-GFp, which were comparable to those of C-GFp. The in vitro protein digestibility of E-GFp resulted the highest. Probably due to proteolysis during sourdough fermentation; chemical scores, essential amino acid profile, biological value and nutritional index of E-GFp were higher than those of C-DWp. The hydrolysis index (HI) of E-GFp was ca. 30% lower than that found for C-GFp. As shown by sensory analysis, the characteristic of E-GFp were acceptable. The manufacture of E-GFp should be promising to expand the choice of gluten-free foods, which combine sensory and nutritional properties.     

Bacillolysin,papain, and subtilisin improve the quality of gluten-free rice bread

Protease has been shown to be an effective food additive for improving the quality of gluten-free rice bread. In this study, we found that bacillolysin (Protin SD-NY10, metallo protease), papain (cysteine protease), and subtilisin (Protin SD-AY10, serine protease) increased the specific volume of gluten-free rice breads by 30–60% compared with untreated breads. These proteases also decreased crumb hardness by 10–30% compared with untreated breads. Many fine bubble cells were observed in the crumb of the protease-treated rice breads using scanning electron microscopy. Optical microscopic observation revealed fine networks of small protein aggregates stained by Coomassie Brilliant Blue (CBB) in the rice batter of the improved gluten-free rice breads. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) of protein in the rice batter suggested that the amount of low molecular weight proteins (less than 10 kDa) increased with the use of Protin SD-NY10, Protin SD-AY10 and papain treatments compared with untreated rice batter. Thus, we considered that the small proteins aggregates were formed through disulfide bonds. This fine network was effective for retaining CO₂ gas during the fermentation process, resulting in an increase in the specific volume and a decrease in the crumb hardness of gluten-free rice bread.     

Optimization of rheological properties of gluten-free pasta dough using mixture design

The rising demand of gluten-free products for celiac people has led to important technological research on the replacement of the gluten matrix in the production of high quality gluten-free foods. The objective of this work was to evaluate the effect of composition (hydrocolloids, water, and proteins) on the rheological and textural properties of gluten-free dough used for producing pasta based on corn-starch and corn flour. Extensibility and rheological properties of gluten-free pasta dough were studied. Rising protein or gum contents produced a marked increase of deformation at break. However protein content was negatively correlated with breaking force. The increase in gums content produced an increase in storage and loss moduli (G′, G″). G′ was always larger than G″ with a small increase of both moduli with frequency. The mechanical relaxation spectrum was predicted from dynamic oscillatory data using the broadened Baumgaertel–Schausberger–Winter model. Application of a mixture design allowed finding the optimal composition to achieve the desirable textural properties using response surface methodology. A formulation containing 35.5% water, 2.5% gums, 4.7% proteins, 42.8% corn-starch, 10.7% corn flour, 1% NaCl, and 2.8% sunflower oil led to the highest values of G′, breaking force, and extensibility according to the optimization analysis performed.     

Volume and texture improvement of gluten-free bread using quinoa white flour

Patients suffering from coeliac disease have to avoid traditional cereals-based products and depend on the availability of gluten-free alternatives. The gluten-free bread matrix and its foam stability are strongly affected by the choice of ingredients. In this study, the impact of quinoa white flour on bread quality parameters, in particular volume, has been investigated. The pseudocereal proved to be a suitable substrate for dough aeration using yeast, since considerably more glucose and a higher activity of α-glucosidase were found in comparison to rice and corn flour. Consequently, quinoa white flour was used to replace 40–100% of the rice and corn flour in a gluten-free control recipe. As a result, quinoa white flour enhanced the specific volume by 33%, which was related to the absence of bran components and the increased α-glucosidase activity. The significance of the latter was proven by separately adding sucrose and fungal amyloglucosidase to the control recipe. Moreover, the crumb featured homogeneous and finely distributed gas bubbles and the taste was not compromised. Thus, it was possible to improve the quality of gluten-free bread by using quinoa white flour, which might be a relief for coeliac patients.     

Comparison of the volatile profiles of the crumb of gluten-free breads by DHE-GC/MS

The aroma of gluten-free bread has been considered of lower quality than that of the common wheat bread. With the aim of improving the aroma of gluten-free bread, the volatile profiles of the crumb of gluten-free breads made from rice, teff, buckwheat, amaranth and quinoa flours as well as corn starch, respectively, were evaluated. Wheat bread was used as a reference and dynamic headspace extraction together with GC/MS was employed. It was found that the whole grain breads, made with teff, quinoa and amaranth flours, presented a stronger aroma with higher number of important aroma contributors. Rice bread was characterised by the highest levels in nonanal and 2,4-decadienal and corn starch bread by 2,3-pentanedione and 2-furaldehyde. Teff presented the highest abundance of ethyl hexanoate and ethyl nonanoate, but also of alcohols and aldehydes from lipid oxidation. Quinoa and amaranth were classified by the highest content in Strecker and Ehrlich aldehydes as well as 1-propanol, 2-methyl-1-propanol, 3-methyl-1-butanol or 3-hydroxy-2-butanone from fermentation. Corn starch bread was the closest to wheat bread in the PCA due to the highest content mainly in 2,3-butanedione and furfural as well as the lowest contents in 1-propanol, 1-hexanol and pentanal.     

Sorghum Pasta and Noodles: Technological and Nutritional Aspects

Plant Foods for Human Nutrition - Sorghum is a major cereal crop with various agronomic advantages, contains health-promoting compounds and is gluten-free. There is a growing tendency to use...     

Determination and Comparison of the Lipid Profile and Sodium Content of Gluten-Free and Gluten-Containing Breads from the Spanish Market

Plant Foods for Human Nutrition - The objective is to verify if gluten-free (GF) and gluten-containing (G) breads differ in their sodium content and lipid profile. Samples of GF...     

Microstructure, fundamental rheology and baking characteristics of batters and breads from different gluten-free flours treated with a microbial transglutaminase

Gluten is a fundamental component for the overall quality and structure of breads. The replacement of the gluten network in the development of gluten-free cereal products is a challenging task for the cereal technologist. The functionality of proteins from gluten-free flours could be modified in order to improve their baking characteristics by promoting protein networks. Transglutaminase (TGase) has been successfully used in food systems to promote protein cross-linking. In this study, TGase was investigated for network forming potential on flours from six different gluten-free cereals (brown rice, buckwheat, corn, oat, sorghum and teff) used in breadmaking. TGase was added at 0, 1 or 10 U/g of proteins present in the recipe. The effect of TGase on batters and breads was evaluated by fundamental rheological tests, Texture Profile Analysis and standard baking tests. Three-dimensional elaborations of Confocal Laser Scanning Microscopy (CLSM) images were performed on both batters and breads to evaluate the influence of TGase on microstructure. Fundamental rheological tests showed a significant increase in the pseudoplastic behaviour of buckwheat and brown rice batters when 10 U of TGase were used. The resulting buckwheat and brown rice breads showed improved baking characteristics as well as overall macroscopic appearance. Three-dimensional CLSM image elaborations confirmed the formation of protein complexes by TGase action. On the other side, TGase showed negative effects on corn flour as its application was detrimental for the elastic properties of the batters. Nevertheless, the resulting breads showed significant improvements in terms of increased specific volume and decreased crumb hardness and chewiness. Under the conditions of this study, no effects of TGase could be observed on breads from oat, sorghum or teff. Overall, the results of this study show that TGase can be successfully applied to gluten-free flours to improve their breadmaking potentials by promoting network formation. However, the protein source is a key element determining the impact of the enzyme.     

Allergenic Content of New Alimentary Pasta Made of Lentils Compared with Lentil Seeds and Analysis of the Impact of Boiling Processing

Plant Foods for Human Nutrition - There is growing interest in legumes such as lentil as healthy ingredients in gluten-free products. In that respect, foods based on lentils, like alimentary pasta,...     

Exploring the potential of arabinoxylan as structuring agent in model systems for gluten-free yeast-leavened breads

Although the beneficial effect of arabinoxylan (AX) has been recognized for breadmaking, the available information about the effect of these compounds in gluten-free systems is scarce. In the present study, maize AX was tested in gluten-free breads using a yeast-leavened lean formulation based on rice flour and corn starch and two shaping models: pans and by dropping dough. The effect of the AX level (0%–5%) and hydration (70%–85%) were determined. Breads produced were analyzed in texture, morphology and crumb structure. The breads from the pan shaping model did not show significant differences in the crumb hardness. Moreover, the control breads presented better springiness, cohesiveness and resilience compared to AX breads. For the breads from the dropping dough model, those containing AX had lower hardness and chewiness and higher 2D area, height, cell density and surface area compared to control breads, especially at higher AX levels. Yet, AX caused a detrimental effect in springiness, cohesiveness and resilience. The hydration affected the hardness, 2D area, height, cell density and mean cell area in breads containing AX, finding better results in breads with 80% water absorption. This research demonstrated that even when AX are capable to improve the hardness and crumb structure of gluten-free breads, they could cause a detrimental effect in other textural characteristics.     

Untargeted Metabolomic Profiling Reveals Variation in Metabolites Associated with Nutritional Values in Tef Accessions

Plant Foods for Human Nutrition - Tef (Eragrostis tef), is a gluten-free orphan cereal, crop of nutritional and economical significance. Here we used untargeted metabolomics to survey metabolite...     

Glycemic index and firming kinetics of partially baked frozen gluten-free bread with sourdough

Gluten-free bread often has low nutritive value, high glycemic index (GI) and short shelf-life. The aim of this research was to investigate the influence of sourdough addition on GI, quality parameters and firming kinetics of gluten-free bread produced by partially baked frozen technology. Sourdough was fermented with a commercial starter of Lactobacillus fermentum and added to bread batter at four levels (7.5; 15; 22.5 or 30%). We determined biochemical characteristics of the sourdough and bread chemical composition, glycemic index in vivo, physical properties and firming kinetics after final rebaking. All breads were enriched with inulin and were high in fiber (>6 g/100 g). Control bread that was prepared without sourdough had medium GI (68). Sourdough addition decreased bread GI. However, only breads with 15 and 22.5% of sourdough had low GI. Moreover, addition of 15 and 22.5% of sourdough had positively affected the quality parameters of partially baked frozen bread: specific volume increased, crumb firmness decreased and firming was delayed. In conclusion, the combined application of sourdough and partially baked frozen technology can decrease glycemic index, improve quality and shelf-life of gluten-free bread. Such breads can be recommended as a part of well balanced gluten-free diet.