Characterisation of gluten-free pasta through conventional and innovative methods: Evaluation of the cooking behaviour

The rapid stiffening of a well-developed gluten network able to entrap swollen starch granules is a key factor for the high quality of durum wheat pasta during cooking. Good resistance and firmness, low stickiness and limited release of organic materials into the cooking water are quality traits of primary importance for traditional pasta. In gluten-free (GF) pasta, the formation of a scaffold of retrograded starch can be an alternative to gluten networking: it confers rigidity to the cooked product and reduces pasta stickiness and loss of soluble materials into the cooking water. In a previous paper, 14 commercial GF spaghetti samples were studied as uncooked products from a chemical, biochemical and physical point of view. The aim of this study was to determine the cooking behaviour of these samples. A durum wheat pasta was also included as reference. Suitable cooking conditions were adopted and different conventional and innovative evaluations (i.e. compression test, creep test) were performed as a function of cooking time. Different behaviours were evidenced, often related to the ultrastructural organization of the uncooked products. In particular, the creep test revealed to be very effective in discriminating among the properties of the different GF spaghetti.     

Characterisation of gluten-free pasta through conventional and innovative methods: Evaluation of the cooking behaviour

The rapid stiffening of a well-developed gluten network able to entrap swollen starch granules is a key factor for the high quality of durum wheat pasta during cooking. Good resistance and firmness, low stickiness and limited release of organic materials into the cooking water are quality traits of primary importance for traditional pasta. In gluten-free (GF) pasta, the formation of a scaffold of retrograded starch can be an alternative to gluten networking: it confers rigidity to the cooked product and reduces pasta stickiness and loss of soluble materials into the cooking water. In a previous paper, 14 commercial GF spaghetti samples were studied as uncooked products from a chemical, biochemical and physical point of view. The aim of this study was to determine the cooking behaviour of these samples. A durum wheat pasta was also included as reference. Suitable cooking conditions were adopted and different conventional and innovative evaluations (i.e. compression test, creep test) were performed as a function of cooking time. Different behaviours were evidenced, often related to the ultrastructural organization of the uncooked products. In particular, the creep test revealed to be very effective in discriminating among the properties of the different GF spaghetti.     

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.     

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.     

Texture,processing and organoleptic properties of chickpea-fortified spaghetti with insights to the underlying mechanisms of traditional durum pasta quality

Nutritionally enhanced spaghetti was prepared from durum semolina fortified with 0–30% desi chickpea ‘besan’ flour. This study examined the dough rheology, processing ease and quality attributes of the fortified spaghetti including protein, starch, texture (firmness, resilience and stickiness), colour, cooking loss, and organoleptic acceptability. Chickpea-fortified spaghetti was acceptable to consumers, had reasonable pasta quality, including lower cooking loss and less stickiness than the control spaghetti and retained firmness better than durum after refrigeration. This study suggests that chickpea-fortified spaghetti may be suited to uses such as fresh pasta, in soups, canning, and microwave re-heating. In addition, this study has added to the understanding of the underlying mechanisms of pasta quality. The main findings were: (1) gluten content/composition appears to be more important than protein content for pasta firmness; (2) the protein–polysaccharide matrix appears to be more important than the starch composition for cooking loss; (3) increased protein and amylose contents were associated with decreased pasta stickiness; (4) cooking loss and stickiness were not necessarily as strongly related as commonly believed. Further research into these theories is necessary to fully understand the underlying mechanisms of pasta quality.     

Rice-based pasta: A comparison between conventional pasta-making and extrusion-cooking

Good quality gluten-free products continue to be in demand among the celiac community and the production of pasta from non-conventional raw materials is a major technological challenge. In this work, the effects of two different pasta-making processes (conventional and extrusion-cooking) were investigated on parboiled brown and milled rice flours. The two processes differentiated for extrusion temperature (conventional extrusion: 50 °C, max; extrusion-cooking: 115 °C), whereas the drying diagram was the same. Starch modifications induced by each pasta-making process were analyzed by using a Micro-ViscoAmylo-graph (MVAG), Differential Scanning Calorimetry (DSC), and X-ray Diffraction. The cooking quality was evaluated by weight increase, solid loss into the cooking water, and texture analysis. Pasta obtained from milled rice using the extrusion-cooking process was characterized by the best cooking behavior. In this sample, starch presented the highest peak and final viscosities, the highest gelatinization temperature and lower enthalpy value, and the lowest crystallinity. The cooking quality of pasta obtained from brown rice appeared less affected by the processing conditions. Therefore, the nature and intensity of starch modifications can be modulated by the processing conditions and might explain the different cooking behaviour of rice pasta.     

Effect of milling,pasta making and cooking on minerals in durum wheat

The effect of technological processing on the contents of eight minerals – i.e., calcium, copper, iron, magnesium, phosphorous, potassium, selenium, and zinc – was investigated in pasta making. Milling of durum wheat as well as pasta making were carried out in a pilot plant by using three different grain samples. Pasta samples purchased on the market were also surveyed to gain information on the mineral content of commercial products. The effect of cooking was also investigated in order to determine the retention of the selected elements in the final ‘ready-to-eat’ product. Analyte concentrations in whole grains, semolina, pasta and cooked pasta were determined by inductively coupled plasma-mass spectrometry.     

Suitability of enzymatic hydrolyzates of extracted gluten from fresh pasta by-product used as bread improvers

Gluten extracted from fresh pasta by-products (PG) was enzymatically hydrolyzed by two different commercial proteases (Alcalase 2.4 L and Pancreatin) to different degrees of hydrolysis (DH 2.0, 4.0 and 8.0%). Commercial gluten (CG) was used as reference. The evaluation of functional properties of hydrolyzates from pasta gluten (PGH) and commercial gluten (CGH) showed that Pancreatin hydrolyzates had the highest emulsifying capacities. Regarding the foaming activity, all hydrolyzates performed better than unhydrolyzed gluten. PGH and CGH were added to wheat flour (1%) and their effects on dough rheology were studied. Most hydrolyzates with DH 8% increased dough thermal stability and elasticity during mixing, accelerated the denaturation rate of the protein network, and delayed the gelatinization speed of starch as the temperature increased. Texture profiles and specific volumes of breads from low quality wheat flour with added Pancreatin hydrolyzates (DH 8%) were comparable to those of breads from high quality flour. This showed the potential suitability of PGH and CGH as bread improvers.     

In vitro digestion kinetics and bioaccessibility of starch in cereal food products

The study of starch digestion in cereal-based products is essential since the extent and rate of hydrolysis affects the glycemic index associated with several food-related diseases. Besides, a unique matrix is usually studied and many variations of in vitro techniques (e.g. enzymes, pH, food:enzymes ratio) are selected, then comparison of results became difficult. The recently published INFOGEST in vitro static method with international consensus (Minekus et al., 2014) was applied to several cereal-based products to address whether it is suitable for analysis of starch hydrolysis kinetics. Bread, pasta and cookies were selected taking into account the analysis of different cereal matrixes, including gluten-free products. White bread presented the highest in vitro starch hydrolysis (87%) showing significant differences compared to gluten-free bread (76.5%). Refined flour sheeted pasta (72.6%), whole-wheat extruded pasta (92.0%) and gluten-free pasta (54.3%) showed differences in the extent and rate of hydrolysis. Cookie samples presented the lowest starch hydrolysis (∼45%). The starch availability was estimated by the dializability method, which measures the maltose equivalents dialyzed after simulating digestion. Starch dializability was 35%, 25% and 15% on average for bread, pasta and cookie samples respectively, with positive correlation with rapidly digested starch. The tested in vitro method allowed discriminating the effect of different processing techniques, product types and formulation of the three most common cereal-food matrixes in starch digestion.     

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.     

Deamidation of gluten proteins and peptides decreases the antibody affinity in gluten analysis assays

Wheat gluten is a widely used ingredient in the food industry due to its unique properties and relatively low price. Modification of wheat gluten makes it a versatile ingredient and, thus, increases its applicability in foods. Therefore, gluten proteins can be found in unexpected sources, and this makes the gluten-free diet challenging to follow. Deamidation is one way to modify protein structure. It increases solubility and surface activity of gluten improving its functionality, but consequently, also influencing the accuracy of quantification by immunoassays. In this study, the effect of deamidation on the antibody recognition with gluten analysis methods based on monoclonal R5, omega-gliadin or G12 antibodies was studied. Random deamidation decreased the intensities to 13–54% of the intensity obtained for the intact peptides. Deamidation representing the transglutaminase deamidation decreased the intensities to 4–8%. Deamidation of gluten proteins abolished the recognition by omega-gliadin and G12 antibodies and decreased the recognition of R5 by 600 times when analyzed by the sandwich method and 125 times by the competitive method. In conclusion, with all of the investigated gluten-specific antibodies, deamidation decreased the affinity of antibodies to gluten peptides and proteins, which needs to be considered when assays and regulations are developed for gluten-free products.     

Innovative approaches towards improved gluten-free bread properties

Up to now, most of the research available to improve gluten-free (GF) bread is based on substituting or imitating the gluten network. Slightly less attention is given to technological approaches that modify batter properties such as consistency. This review summarizes the most recent advances to improve GF bread quality, focusing on latest conventional ingredients (e.g. hydrocolloids) and new innovative approaches to replace the gluten-network (i.e., use of enzymes, alternative polymer network), but especially on novel technological approaches, such as high hydrostatic pressure, sourdough technology and non-conventional heating methods. In general, hydrocolloids are still the most studied and well-known additives to gluten-free products, followed by the use of crosslinking enzymes. Within the review, special focus is given to the application of arabinoxylans, which form a stable carbohydrate network in GF batters that may substitute gluten. However, it was seen that technological approaches provide better solutions for enhancing GF bread properties than the latter, especially when non-conventional baking alternatives are applied. From these, ohmic heating resulted the most promising approach to overcome bread quality issues, while remaining time and energy-efficient.     

Pasta viscoelasticity: Its usefulness in the Canadian durum wheat breeding program

The usefulness of pasta disc viscoelasticity to predict pasta cooking quality in the durum wheat breeding program was evaluated. Cooked pasta disc viscoelasticity (PDV) was calculated from the creep curve of the viscoelastogram. Two sets of samples with different quality characteristics were tested for protein content, sedimentation volume (SV), Mixograph mixing characteristics, cooked gluten viscoelasticity (CGV) and cooked pasta disc viscoelasticity. Pearson correlation coefficients indicated that cooked pasta disc visoelasticity was associated with Mixograph values, SV and CGV, but not with protein content. The results indicate that the PDV test is useful in breeding programs because it requires small quantities of sample, it is simple and more closely mimics rheological tests used on the final product, pasta. The optimal conditions for measuring PDV are discussed.     

In vitro starch digestibility,degree of gelatinization and functional properties of twin screw prepared cereal-legume pasta

The investigation explores the possibility of utilizing legume flour (pigeon pea:10–30%) and brown rice flour (35–45%) for production of pasta using twin screw extruder. RSM was used to analyse the effect of feed moisture (28–36%), barrel temperature (70–110 °C) and legume:brown rice ratio on quality responses (in vitro starch and protein digestibility, degree of starch gelatinization, cooking quality, pasting properties, color and textural properties) of pasta. Extrusion processing significantly enhanced in vitro starch and protein digestibility of prepared pasta. The in vitro starch and protein digestibility of pasta ranged between 15.00 and 26.77 g/100 g and 50.34–84.82 g/100 g respectively. Addition of brown rice flour and pigeon pea flour exhibited dominating positive effect on cooking quality of the pasta. Degree of gelatinization of prepared pasta was found in range of 52.13–90.10 per cent. Color characteristics viz. luminosity, redness and yellowness of pasta enhanced with feed moisture. Pasting properties revealed lower peak and final viscosity at higher processing conditions. Firmness of cooked pasta elevated with an increase in the barrel temperature. Acceptability score of health based pasta on the basis of sensory attributes was 8 as inferred from 9 point hedonic scale.     

Effect of quinoa flour on gluten-free bread batter rheology and bread quality

A new gluten-free bread formulations composed of quinoa, buckwheat, rice flour and potato starch were developed in the present study. Rheological characteristics of the bread batter with increasing amount of quinoa were determined; storage (G′) and loss modulus (G″) values were also measured for investigation of viscoelastic properties. To evaluate the quality of breads; technological and physical (bake loss %, specific volume, texture, microstructure, color), chemical (protein, moisture, ash) and sensory properties were determined. All batter formulations independent of the quinoa amount exhibited pseudoplastic behavior, and G′ values were found to be higher than G″ values in expressing the solid like characteristics of the batter. Amount of quinoa flour addition did not present significant difference on bake loss%, specific volume and protein content (p>0.05); however, 25% quinoa flour bread displayed better results with its higher sensory scores and softer texture. Quinoa and buckwheat flour mixture therefore will be a good alternative for conventional gluten-free bread formulations.     

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.     

Influence of Technological Modifications of the Protein Network from Pasta on in vitro Starch Degradation

The pasta protein network limits starch hydrolysis rate in vivo leading to low post-prandial glycemia. To better understand the mechanisms involved, various pasta products were processed to obtain protein network structures differing from that in reference pasta extruded at 40 °C and dried 17 h at 55 °C. After cooking, pasta strands were submitted to in vitro alpha -amylolysis. Compared to reference pasta, higher extrusion temperature (70 °C), high-temperature drying treatment (2 h at 90 °C) or autoclaving (115 °C for 15 or 40 min) had no marked effect on the rate of dextrin release from pasta particles. Protein enrichment at a 20%-level and flour fractionation-reconstruction with removal of insoluble fibre before pasta extrusion significantly (p<0·05) delayed (≥1 h) the rate of dextrin release (−14% at 8 h). Confocal laser scanning microscopy allowed the three-dimensional structure of the protein network from protein-enriched pasta to be observed, and suggested that increased starch encapsulation may explain the reduced accessibility of starch to alpha -amylases. A stronger cohesiveness between starch and protein, due to insoluble fibre removal, was probably responsible for the decrease of starch accessibility to alpha -amylase in fractionated-reconstructed flour pasta. Modified geometrical characteristics (e.gtortuosity) of the protein network were not correlated with starch degradation rates.     

A novel method to prepare gluten-free dough using a meso-structured whey protein particle system

This paper presents a novel concept for making an elastic dough using a structured protein suspension. The idea behind it is based on the hypothesis that a number of gluten properties originate from a particle structure present in the gluten network. Three different mesoscopically structured whey protein suspensions were produced: whey protein aggregates, a whey protein cold set gel and whey protein particles. Dough mixtures or batters were prepared by mixing the structured protein particle suspension with starch. Farinograph curves, small and large deformation experiments showed that the presence of a mesoscopic protein structure had a large impact on the properties of gluten-free starch mixtures. The whey protein that was structured into a mesoscopic particle suspension changed the starch mixture from a liquid into a cohesive material, having strain hardening properties.     

Rheological properties of wheat flour processed at low levels of hydration: Influence of starch and gluten

The rheological properties of wheat flour under processing such as extrusion (with 28% moisture content, wet basis) are influenced by the molecular changes its components undergo during processing. But, there was no simple relationship between the wheat-flour characteristics and their rheological properties. In order to investigate the quantitative and qualitative effects of the individual flour components on rheological properties, model blends of wheat starch and wheat gluten with different starch/gluten ratios were studied. The effects of gluten and starch quality were also investigated by using different gluten types and by modifying the amylose content of starch, respectively. The shear viscosity of the blends, determined by capillary rheometry under controlled conditions (35% moisture content, 140 °C), was observed to be modified by both gluten and amylose content. The changes undergone by wheat gluten under these conditions were analysed by HPLC, to determine the levels of unextractable polymeric proteins, and by Lab-on-a-Chip analysis of protein composition, to follow the polymerisation of protein under processing. This study indicated that in low hydrated products in the molten state, shear viscosity is affected by the structure of the blends as determined by fluorescence microscopy and by the molecular changes occurring during processing.     

Functional Properties of Gluten-Free Pasta Produced from Amaranth, Quinoa and Buckwheat

The use of amaranth, quinoa and buckwheat for the production of gluten-free pasta was investigated in the present study. The aim of the work was to produce pasta of good textural quality, in particular, low cooking loss, optimal cooking weight and texture firmness. The results demonstrated that pasta produced from amaranth had decreased texture firmness and cooking time, while pasta from quinoa mainly showed increased cooking loss. In buckwheat pasta the least negative effects were observed. By combination of all three raw materials to one flour blend in the ratio of 60% buckwheat, 20% amaranth and 20% quinoa, dough matrix was improved. After decreasing dough moisture to 30%, addition of an increased amount of egg white powder of 6% and addition of 1.2% emulsifier (distilled monoglycerides) texture firmness as well as cooking quality of gluten-free pasta produced from such a flour blend reached acceptable values comparable to wheat pasta.