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BACKGROUND The effect of high-pressure homogenization (HPH) on the rheological and thermal properties, water retention capacity (WRC), morphology and in vitro digestion of wheat starch was evaluated. Starch suspensions (50 g kg-1 , w/w) were treated at increasing pressures (up to 100 MPa) and numbers of cycles (up to 5) to generate a wide range of energy densities (70-500 MJ m-3 ) delivered to the sample during processing. RESULTS High-pressure homogenization induced a partial starch gelatinization confirmed by higher digestibility. Gelatinization degree (GD) was between 13% and 83%, causing a wide range of functional properties. High-pressure homogenization-treated starch samples showed WRC values of 810-1910 g kg-1 . Storage modulus (G') and complex viscosity (η* ) of starch dispersions were almost two and three times higher than the control at 13% and 83% GD, respectively. Positive linear relationships between GD (R = 0.98, P

Polypropylene (PP) based active composite films were prepared by adding butylated hydroxy anisole (BHA), butylated hydroxytoluene (BHT), and tertiary butylated hydroquinone (TBHQ) antioxidants using the extrusion molding process. All concentrations of BHT, 2% to 3% BHA, and 3% TBHQ significantly increased the tensile strength (TS) of the composite films compared with control films. Increasing antioxidant concentration decreased TS values for BHT films, whereas an opposite trend was observed for BHA and TBHQ films. BHA at 2%, and TBHQ at all added concentrations significantly reduced elongation at break (Eb ) of the composite films compared to control films. Water vapor permeability (WVP) of 1% BHT film was not significantly different from control. However, other antioxidants especially at increased concentrations significantly increased WVP values. TBHQ films with 300% to 662% increase had the highest WVP and BHT films with 5% to 81% increase had the lowest WVP among composite films. All three antioxidants had a negative effect on the transparency of the films; however the effect of BHA at higher concentrations was greater. The antioxidants did not change the color attributes of the films. Films containing all antioxidants showed 2,2-diphenyl-1-picrylhydrazyl radical-scavenging activity, which increased with increase in their concentration, especially for those containing 3 wt.% BHT and TBHQ. Overall, incorporating BHA and BHT into a PP matrix improved mechanical, barrier, antioxidant properties, and film appearance and consequently were proposed for the development of antioxidant active PP films. TBHQ film is not recommended for food packaging because of its weak mechanical properties (lower Eb and TS values, higher WVP, and greater migration).

In this study, starch-based films incorporating metal oxide (MO2 ) nanoparticles (NPs) of TiO2 and SiO2 (at a concentration of 1 to 4 wt. %) were produced by solution casting method. In order to exhibit antimicrobial properties, MO2 NPs were modified by synthesizing silver (Ag) ions over the NPs using cationic adsorption method. Ag ions were then reduced to metallic Ag by sodium borohydride solution. Scanning electron microscopy showed a smooth surface for the pure starch film. Incorporating MO2 @Ag NPs in the films increased surface roughness with agglomerated NPs within starch matrix. Energy dispersive X-ray analysis exhibited a uniform dispersion of Ag-loaded MO2 NPs, which increases surface contact between these NPs and the biopolymer matrix leading to improved physical and mechanical properties of the resulting films. With increasing in the NPs concentrations, the tensile strength and elongation at break % of the films increased and decreased, respectively. Incorporating MO2 @Ag NPs into starch matrix decreased solubility in water and water vapor permeability of the obtained films, and significantly inhibited the growth of Escherichia coli and Staphylococcus aureus. The most antibacterial effect was obtained for the films containing higher weight concentrations of Ag-loaded SiO2 -NPs.

Professional pasta cookers are filled with fresh water. The solids leached from the cooked pasta make pasta less firm and stickier while leading to changes in water properties and overflow. Added fresh water then has to be reheated. The effect of continuous cooking on cooked pasta quality and water properties was investigated for the first time by simulating professional pasta cooking on a laboratory scale. RESULTS Continuous cooking procedure of 12 batches led to a solid content of cooking water of 37?g?kg?1, resulting in an increase in shear-thinning behaviour and consistency index. Pasta cooking loss decreased from 52.7 to 35.7?g?kg?1 due to the lower water concentration gradient through the pasta. This was confirmed by a decrease in swelling index from 2.0 ? 10?3 to 1.6 ? 10?3?g?kg?1 during the optimal cooking time (13?min 45?s). Surprisingly, continuous cooking made the pasta firmer while stickiness did not differ significantly (P > 0.05). CONCLUSION Taking batch number 7 as the acceptability threshold, further studies are required to find an optimal solution for retaining cooking water properties highly affecting daily cooking procedures in food service kitchens. ? 2018 Society of Chemical Industry

Durum wheat is the raw material of choice for the manufacture of superior quality pasta products. However, in some parts of the world many pasta producers have to use common wheat to make pasta, which shows a deficiency with respect to quality attributes. In this respect, the functionality of different hydrocolloids in a weak common wheat flour was investigated as a comparative study with the objective to improve pasta-making potential under industrial processing conditions. Six commercial hydrocolloids, sodium alginate (AL), propylene glycol alginate (PGA), xanthan gum, carrageenan, locust bean gum or guar gum were added to wheat flour at 0.5% and 1% substitution. A rheological investigation, based on dynamic small strain tests and large deformation tests (farinograph and amylograph analyses) was performed to evaluate differences in dough structure due to interactions between flour components and hydrocolloids, and related to cooking properties of pasta. All hydrocolloids promoted an increase in elastic interactions in the dough. The strongest doughs were obtained by addition of alginates. Only cooked pasta supplemented with AL, PGA and XG showed an increase in firmness compared with the reference (PGA > AL > XG). The product enriched with 0.5% PGA or 1% AL gave the highest overall acceptability and sensory scores. On the contrary, xanthan gum, carrageenan, locust bean gum or guar gum performed relatively poorly in flour. On the basis of these results alginates were the most effective improvers of pasta quality among different hydrocolloids.

Psyllium seed husk (PSH) is a soluble dietary fibre with interesting health benefits, including reduction in blood glucose level in subjects with type 2 diabetes. Its supplementation in pasta represents a challenge due to a negative impact of high PSH levels on product acceptability. The aim of this work was to investigate the effects of the substitution of semolina with different levels of PSH on cooking properties, microstructure and in vitro glycaemic response of pasta. Dry pasta samples enriched with PSH were produced by replacing durum wheat semolina with 25, 50, 75 and 100 g/kg PSH. Cooked enriched pastas were firmer and sticker than the control. Cooking loss increased with increasing PSH levels above 25 g/kg with values below the technological acceptable limit of 80 g/kg. Semolina substitution with 50–100 g/kg psyllium was effective in lowering the predictive glycaemic response of enriched pasta in comparison with the control. Scanning electron microscopy and dough rheology (dynamic frequency and temperature sweep tests) suggested that this decrease was related to the formation of fibre aggregates limiting starch swelling. Semolina replacement with 50 g/kg PSH has the potential to provide a health benefit with minimal impact on cooking features of functional pasta.

The objective of this study was to investigate the effect of osmotic dehydration (with and without sonication) and the use of different types of edible coating on functional and color parameters of dried apricot. Osmotic pretreatment was carried out in sorbitol solution of 35 °Brix at 55 °C for 30 and 45 min. Two levels of ultrasound frequency (25 and 35 kHz) were tested. Samples were coated using pectin + citric acid (CA), pectin + ascorbic acid (AA) and pectin alone after osmotic treatment and were dried at 60 °C. The results revealed that ultrasound assisted osmotic dehydration (UOD) led to the loss of total phenolic compounds (TPC) and vitamin C compared to osmotic dehydration (OD). TPC and β-carotene contents decreased with the increase in sonication frequency from 25 to 35 kHz. However, UOD pretreated samples showed higher antioxidant capacity and β-carotene content than OD apricots. OD improved color of hot-air dried apricot compared to UOD pretreatment. The use of pectin + AA coating increased TPC and vitamin C retention and total antioxidant activity of OD or UOD pretreated samples compared to pectin or pectin + CA coatings. UOD and pectin + AA coated samples showed lower L* and b*, and higher a* values, whereas coating with CA improved color of dried apricot cubes. Coatings containing CA or AA promoted β-carotene retention in dried apricot pretreated by OD and UOD.

The objective was to evaluate whether an ultrasonic reflectance technique has predictive capacity for breadmaking performance of doughs made under a wide range of formulation conditions. Two flours of contrasting dough strength augmented with different levels of ingredients (inulin, oil, emulsifier or salt) were used to produce different bread doughs with a wide range of properties. Breadmaking performance was evaluated by conventional large-strain rheological tests on the dough and by assessment of loaf quality. The ultrasound tests were performed with a broadband reflectance technique in the frequency range of 0.3-6 MHz.; Results: Principal component analysis showed that ultrasonic attenuation and phase velocity at frequencies between 0.3 and 3 MHz are good predictors for rheological and bread scoring characteristics.; Conclusions: Ultrasonic parameters had predictive capacity for breadmaking performance for a wide range of dough formulations. Lower frequency attenuation coefficients correlated well with conventional quality indices of both the dough and the bread. © 2016 Society of Chemical Industry.; © 2016 Society of Chemical Industry.

The objective was to examine the potential use of resistant starch (RS) as a fibre-enriching ingredient in gluten-free pasta. Pasta was enriched with commercial RS type II (Hi-Maize™ 260) at 100-200 g kg-1 substitution of rice flour. The effects on the rheological properties of dough and pasta quality as a result of RS addition and the loss in RS due to the process were evaluated.; Results: Dough water absorption was not influenced by the addition of RS. The cooking loss (CL) of RS-enriched samples was 30% lower than reference without fibre. The addition of RS significantly increased firmness of cooked pasta, and above 100 g kg-1 RS level of substitution samples showed a lower stickiness value. Dynamic rheological tests on pasta dough showed a higher storage modulus for fibre samples, indicating a higher number of elastically physical interactions. Loss in RS in uncooked pasta was about 31% compared with the initial amount added to the product.; Conclusions: The addition of RS improved the quality of gluten-free pasta owing to its ability to increase the firmness and decrease the CL and stickiness of cooked pasta. The product enriched with 200 g kg-1 RS can be considered a source of DF. © 2016 Society of Chemical Industry.; © 2016 Society of Chemical Industry.

Pasta is a starchy staple food, which is a good carrier of health-promoting ingredients that can manipulate the glycaemic response. Dry pastas supplemented with DFs were produced substituting durum wheat semolina with Barley Balance® (BB), psyllium seed husk (P) or two inulin products with different degrees of polymerisation. The aim was to investigate the effects of soluble DFs on viscoelastic properties of durum wheat dough, pasta-making performance and glycaemic response of pasta. DFs were added individually and in combination to produce samples with large differences in structural/rheological properties and to understand their role in the manipulation of predicted glycaemic response. Dough rheological properties were investigated using frequency and temperature sweep tests in the linear viscoelastic range. DF-enriched doughs showed large differences in elastic properties between 25 and 95 °C due to differences in the number of interactions between components and the swelling of gelatinized starch granules. A correlation between in vitro glycaemic response of pasta and a swelling index obtained from temperature sweep test was observed. Swelling of starch granules decreased with the increase in elasticity and water absorption of fibre-enriched doughs up to a critical value above which only slight changes occurred. Changes in firmness was dependent on dough viscoelasticity. P and long-chain inulin gave lower detrimental effects when incorporated with BB. Pasta containing BB individually added and in combination with psyllium showed an overall sensory acceptability comparable to control and in vivo glycaemic index reduction of 33–37%.

Pasta is traditionally manufactured using only durum wheat semolina, but it is possible to incorporate other flours or ingredients into pasta in order to increase its nutritional value to the consumer, compared to conventional pasta. For this reason, pasta was prepared substituting durum wheat semolina with 15% of enriched dietary fibre flours (Glucagel, inulin Raftiline® HPX, inulin Raftiline® GR, psyllium and oat). Moreover, all dietary fibres (excluded Glucagel) were added in combination in order to evaluate their possible antagonistic or synergic effect on predicted glycaemic response. In general, all enriched dietary fibre pasta sample showed a significant decrease (except for pasta containing a combination of 7.5% inulin Raftiline® GR and 7.5% oat bran flour) in reducing sugars released and standardised AUC values compared to control pasta. However, this study showed that the combination of dietary fibres in pasta formulation led to an antagonistic effect on the predicted glycaemic response.

The production of high quality functional pasta from non-conventional raw materials represents a challenge. A partial substitution (15 g/100 g) of durum wheat semolina with long-chain inulin (HPX) and short-chain inulin (GR), Glucagel, psyllium and oat material (added individually and in combinations) was performed in order to increase the level of dietary fibre intake. The cooking, textural and colour characteristics of the pastas were evaluated and compared to control sample containing exclusively durum wheat semolina. Generally, material addition to the durum wheat pasta increased cooking losses, swelling index and water absorption, whilst reduced firmness and resistance to uniaxial extension of pastas. Raw spaghetti samples resulted significantly darker ( L *) and more redness ( a *) than control pasta. In the cooked pasta, all inulin enriched samples were brighter than semolina pasta. Pasta prepared with 15 g/100 g semolina of oat flour showed the best performance (except for the colour) compared to the other experimental pasta samples, but was significantly different to control durum wheat sample. Combinations of fibre rich additions were studied with the inclusion of inulin GR having a less deteriorating effect when added in combination with oat flour. This illustrates that some fibre rich sources may act better in combinations than separately.

A high density polyethylene (HDPE)/calcium carbonate (CaCO(3)) film containing TiO(2) was prepared via blown film extrusion process. The photocatalytic properties of this film were evaluated by voltammetric, UV-Vis spectrophotometric and gas chromatographic measurements following the decomposition rate of suitably selected molecular probes, such as 4-hydroxybenzoic acid and methylene blue. The film containing 1% w/w of TiO(2) displayed a profitable and reproducible photoinduced degradation activity towards target organic compounds. The effect of packaging photocatalytic activity on the structural and microbiological stability of a short-ripened cheese was studied. Cheese structure was assessed by dynamic, small deformation rheological tests. A container consisting of a multilayer material, where the layer brought in contact with the food, made from the HDPE+CaCO(3)+TiO(2) composite matrix, was able to provide a greater maintenance of the original cheese structure than a rigid container currently used, mainly due to the inhibition of lactic acid bacteria and coliforms.

The effect of high pressure homogenization (HPH) and ultrasound (US) on rheological properties, color, precipitate weight ratio, pectin esterification degree and cell integrity of tomato juices with different soluble solids content (5.0, 7.5, 10.0 °Brix) was studied. Samples were subjected to HPH up to 150 MPa or US up to 30 min. The energy efficiency associated to the processes was also evaluated. Results showed that stress type and product concentration influenced the changes of tomato juice physical properties. In particular, HPH and US treatments were responsible for higher G′ and consistency of processed tomato juices than untreated samples. Increases in sample rheological properties were comparable for the 5.0 and 7.5 °Brix treated HPH and US samples, whereas HPH was more effective than US in the case of 10.0 °Brix sample. These changes were in agreement with other indexes, i.e. precipitate weight ratio increase and cell integrity decrease, and were attributed to stronger of inter-particle interactions. The process energy efficiency showed that lower energy was involved in HPH in comparison to US.

The objective was to evaluate whether an ultrasonic reflectance technique has predictive capacity for breadmaking performance of doughs made under a wide range of formulation conditions. Two flours of contrasting dough strength augmented with different levels of ingredients (inulin, oil, emulsifier or salt) were used to produce different bread doughs with a wide range of properties. Breadmaking performance was evaluated by conventional large-strain rheological tests on the dough and by assessment of loaf quality. The ultrasound tests were performed with a broadband reflectance technique in the frequency range of 0.3-6 MHz.Principal component analysis showed that ultrasonic attenuation and phase velocity at frequencies between 0.3 and 3 MHz are good predictors for rheological and bread scoring characteristics.Ultrasonic parameters had predictive capacity for breadmaking performance for a wide range of dough formulations. Lower frequency attenuation coefficients correlated well with conventional quality indices of both the dough and the bread. © 2016 Society of Chemical Industry.

Stracchino is a short ripened soft cheese mainly produced in the North of Italy. The changes in Stracchino cheese quality are mainly attributable to microbial spoilage and structure breakdown because of enzymatic activity. The aim of this work was to evaluate the effect of different packaging materials on the shelf life of Stracchino cheese, monitoring changes in rheological, microbiological and sensorial properties over 28 days at 4C. Three packaging materials were compared in order to optimize the suitable packaging for Stracchino cheese: (1) paper-polyethylene as a reference package commonly used for this product [R]; (2) commercial high-density polyethylene (HDPE) -based film, mainly composed of calcium carbonate and HDPE (Ovtene® [OV]); and (3) experimental active packaging obtained with addition of potassium sorbate to OV (active Ovtene® [AOV]). The OV and AOV resulted more effective to control microbial spoilage than R, without affecting sensorial and chemical properties. AOV allowed the inhibition of yeast growth, probably because of the activity of potassium sorbate. The gel structure, which characterizes the Stracchino cheese, was maintained until 21 days with the application of AOV, while a liquid-like behavior was associated to the sample packed with the reference material after 14 days. Microbiological, rheological and sensory results demonstrated the effectiveness of AOV in prolonging Stracchino cheese storability. Practical Applications In the last years, the research in food packaging have been focused on the development of active packaging, able to interact with food and surrounding media. These innovative materials could be applied in order to extend shelf life of food products. The application of films with potassium sorbate to a short ripened soft cheese resulted effective to maintain product structure and to control microbial spoilage. Active packaging selected in this study could be used as packaging material for this type of cheese in order to prolong shelf life.

The aim of this work was to investigate the effects of hydrocolloid addition on rheological properties and breadmaking performance of rice-buckwheat batter at different water levels. Xanthan gum (XG) and propylene glycol alginate (PGA) were added to rice-buckwheat blend (60:40) at levels of 0.5–1.5%. Batter rheological properties were investigated using dynamic measurements in the linear viscoelastic range (frequency sweep and time cure tests). The addition of both hydrocolloids significantly enhanced the storage modulus (G′) of batter. XG exerted greater effect on G′ than PGA. Different effects on starch gelatinisation were observed for the two hydrocolloids. PGA breads showed higher improvement in terms of increased specific volume (V s ), decreased crumb firmness and crumb structure than XG breads. Different technological behaviours were explained on the basis of batter rheological properties.

This study investigates the effect of different types of surfactant (glycerol monostearate, Tween 60, and Tween 80) on water vapor permeability (WVP), tensile strength (TS), percentage elongation at breaking (E), and structure of an emulsified edible film composed of cornstarch, methylcellulose, and cocoa butter or soybean oil. Factorial designs at two levels were used to analyze the effect of emulsifier (EM) and lipid content on the functional properties of film. Results showed that the effects of independent variables on WVP, TS, and E depend on surfactant and lipid type. The presence of EM significantly decreased the WVP of cocoa butter films but did not improve the barrier or mechanical properties of soybean oil-based film.

Filled snacks are new industrial co-extruded products made by a dough shell and an internal filler constituted by salty or sweet cream. Due to different rheological characteristics of fillers and dough, it is difficult to choose operational variables capable of guaranteeing a complete filling. This work aims to determine the optimal rheological properties of both filler and dough to make an optimal product without undesired voids. A typical dough and several fillers have been considered and rheologically characterised by means of dynamic oscillation, steady shear flow and creep tests. A dynamic temperature ramp test at 1 Hz was performed to determine temperature dependency of the tested material. A time–temperature shifting technique based on a modification of the Cox–Merz rule and on weak gel model was applied to extend the flow curve range and to overcome temperature experimental difficulties. The obtained data, expressed by a power law correlation, were inserted in a numerical algorithm previously developed, and the internal swelling of the dough followed by a recovery was computed during mixed flow inside the extrusion head. It was suggested that a greater recovery implies a better filling capability because the filler may follow the dough during swelling. Simulations indicated that a complete filling was obtained only for the materials exhibiting a quite stable network during the flow. The experimental results obtained by preparing different industrial filled snacks confirmed the simulative predictions. Quantification of the network shear stability was determined by comparing the loss modulus (G″) and shear viscosity (η) values. In particular G″ versus frequency and η versus shear rate were fitted by a power law model and the best fillers must present a ratio between their exponents close to 1.

Filled snack production has been considered from several point of views. In this work, the effect of the operational variables on the cereal mixture constituting the external part of this product has been studied. A typical flour blend was characterised and used in a previous developed model to simulate the extrusion conditions and to show process damage. Chemical and rheological methods are proposed as experimental techniques capable of measuring the damage induced by the process. The link between chemical contents and mechanical damage was proposed on the basis of the thermal history and of the mechanical power input. The simulation results obtained by a new proposed extrusion model applied to a real twin co-extruder, made it possible to predict damage such as the lysine decrease, and to show the effect of different screw speeds. It appeared that the computed results are in an acceptable agreement with industrial evidence.

Dynamic measurements were made with a controlled stress rheometer to study the viscoelastic properties (G', G', δ) of wheat doughs (45% wb water content) for fresh pasta production prepared with different blends of durum wheat semolina and common wheat flour with different concentrations of sodium chloride. Increasing the semolina and sodium chloride content, increased the strength and the solid-like behaviour of semolina-flour blends. The physical properties of dough were strongly dependent on particle size distribution and salt addition. By manipulating semolina-flour ratio and ionic strength, it was possible to obtain semolina-flour doughs with a rheological behaviour close to that of pure semolina dough.

Cereal products are consumed daily by the majority of the population. Popular belief is that these cereal products, rich in carbohydrates, produce a high glycaemic response and may not be a contributing factor to the obesity epidemic throughout the world. Recently the food industry has investigated ways of improving the overall nutritional balance of carbohydrate rich foods and focused on increasing their dietary fibre (DF) contents at the expense of readily digestible carbohydrates. It is well documented that dietary fibre is involved in disease prevention and enhanced health of consumers. Moreover, the food industry can take advantage of the physicochemical properties of fibre to improve the viscosity, texture, sensory characteristics and shelf-life of their products. The focus of this review paper is on the influence of DFs (inulin, fructo-oligofructose, β-glucans, arabinoxylans and resistant starch) supplementation on the quality and nutritional aspects of common foods containing cereals- pasta, bread, muffins/cakes and extruded snacks. This review reports on the evidence regarding fibre enrichment of cereal foods and looks at the advances and future trends in enriched dietary fibre cereal products.

Gluten films obtained in acid conditions display some protein dispersion difficulties. Ultrasound treatment (UT) could represent an interesting strategy for improving gluten film appearance. Different UT exposure times were applied to film-forming dispersion. The aim of this work was to investigate the effect of ultrasound treatment on gluten-based films at molecular and mesoscopic levels. Distribution in gliadin and glutenins was determined with SE-HPLC. The UT improved protein dispersion and final film appearance. Sonication did not lead to large changes in various gluten fractions, which suggests absence of important protein breakdown at the molecular level. Gluten showed high tolerance to UT. Surface properties of untreated and treated films were investigated by contact angle measurement: sonication promoted hydrophilic surface properties. Industrial relevance Bio-based packaging has been receiving increasing attention in view of its beneficial impact on the environment. Among proteins, gluten resulted as a very interesting film-forming material. Gluten films prepared in acid conditions showed problems in protein dispersion. Sonication represents a physical strategy which allowed us to obtain gluten-based films without the addition of chemical additives, such as sodium sulphite.

The aim of this experimental work was to evaluate the effect of inulin addition on the rheological properties of common wheat doughs and bread quality. Three commercial fructan products of different number average degree of polymerisation (DPn) were used (DPn = 10 for inulin ST; DPn = 23 for inulin HP and HP-gel). Inulin contents from 2.5 to 7.5% on dry matter (wheat flour plus inulin) were used. Dough rheological properties were investigated using farinograph and dynamic rheological measurements. Upon addition of dietary fibre (DF), significant increase in mixing time and stability, and decrease in water absorption were recorded. Inulin ST exerted greater effect on water absorption than HP products. Inulin with high DP determined large changes in linear viscoelastic properties of dough. The storage modulus (G′) gradually increased and tan δ decreased with increasing levels of inulin HP and HP-gel, which contribute to the overall dough elasticity and strength. The increase in solid-like behaviour with DF content prevented expansion of wheat dough during the fermentation stage. No significant differences were observed between sample HP and HP-gel. Enrichment with inulin ST led to lower changes in linear viscoelastic properties of dough at farinograph water absorption than inulin HP. Bread volume was significantly reduced and crumb hardness was enhanced by inulin HP level in the range 5–7.5%. When inulin ST was added to a flour suitable for breadmaking, a trend of increasing bread volume with the increase of DF content was found.

Structure formation in dough systems is the result of an interplay between processing conditions and subsequent interactions in the protein phase. These interactions can be both of a covalent (disulfide bonds) and physical nature and occur at all length scales. The aim of this work was to investigate the effect of simple shear deformation at various shear rates on wheat dough rheological properties, microstructure and GMP fraction. Shear processing was compared with a z-blade mixing. The contribution of disulfide bonds on different length scales was investigated using NEMI as SH-blocker agent. Dough strength and strain hardening decreased with the increase in shear rate leading to dough weakening. Sheared dough at low shear rate exhibited the highest strength among doughs under large deformation conditions. Mixing or shearing in the presence of NEMI strongly reduced fracture properties and GMP content of mixed and sheared doughs. Only the dough that was sheared at low shear rate still exhibited some strength and strain hardening. Large deformation results were integrated with linear viscoelastic properties using low shear rate–long time creep tests. Elastic compliance curves for reference doughs were lower than the dough containing NEMI. Shearing at low and intermediate shear rates gave similar elastic compliance. Dough rheological behaviour was interpreted in the context of polymer gels containing reversible cross-links and physical interactions. Shearing led to the formation of a heterogeneous structure. Very large protein domains were observed for dough at low shear rate, which became smaller upon higher shear rates suggesting that those structures are quite weak. When NEMI was present, large protein structures were lost more easily. The break-up of gluten domains during mixing and shearing was proposed to be a result from a different mechanism.

The rheological properties of edible film-forming dispersions containing corn starch, methylcellulose (MC) and glycerol were studied using oscillatory and steady shear flow tests. The combined effects of glycerol content and blending levels of MC with starch on the rheological properties of dispersion were evaluated. The flow curves showed shear-thinning behaviour. Mechanical spectra and Cox–Merz superposition of steady-shear viscosity and dynamic viscosity were consistent with polymer solutions containing topological entanglement interactions of chains. Dispersion stability results showed total recovery of the viscoelastic properties of dispersions subject to high strains, as expected for entangled polymers. MC was the main factor influencing apparent viscosity and viscoelastic properties.

Filled snack production has been considered and modelled by considering the rheological properties of the different components. The possibility of inserting the filler directly inside the extruder head allows post-extrusion swelling to decrease thus increasing the product quality. To find the optimum position of the filler nozzle with respect to the head extruder orifice, a rheological model was developed by assuming power law behaviour for both dough and filler tangential stresses and a single relaxation time mechanism for the normal stresses shown by dough. The internal swelling was computed numerically for typical industrial conditions and a validation of the model was done by varying around the mass flow rate of dough, the flow indexes of the two components, the consistency index of dough, and finally some geometrical conditions. It was found that the system did not depend too much on the geometry, but is very sensitive to dough and filler rheological properties. The simulation predictions appeared to be in agreement with industrial expectations, predicting a short distance between nozzle and extruder head.

Stress–relaxation behaviours of Mixograph semolina–water doughs prepared from Canadian durum wheat cultivars with diverse gluten strength were investigated and related to mixing characteristics, large deformation properties, and bread- and pasta-making quality. Semolina from «strong» (S) and «moderately strong» (MS) durum wheat cultivars required a longer Mixograph mixing time (4–5 min) and higher work input (140–196 Arbitrary Units) to mix to peak dough resistance (PDR) than «weak» (W) and «very weak» (VW) durum cultivars (2–3 min and 80–117 AU). Extensigraph maximum resistance to extension (R max /E ratio) and Alveograph P/L (tenacity to length ratio) values were higher for doughs from S cultivars than for MS, W, and VW cultivars. Doughs from S cultivars exhibited higher storage modulus (G′) and lower tan δ values at all frequencies, and slower rates of stress relaxation as compared to MS, W, and VW cultivars. Stress relaxation (times to relax 50% (t 50 ) and 75% (t 75 ) of initial stress) indicated that stronger doughs, which had higher proportions of glutenins, took longer to reach these iso-relaxation states, regardless of their initial relaxation modulus value. The parameters t 50 and t 75 were also strongly correlated with dough mixing properties, Extensigraph R max /E, Alveograph P/L, mixing energy, mixing time and loaf volume obtained by a long and a short bread-making process. However, for S cultivars loaf volume was 10 to 20% lower than that expected of bread wheat of comparable protein content. Stress relaxation data demonstrated no simple correlation to pasta cooking quality indicating that stronger gluten did not translate into a superior pasta cooking quality. Results are interpreted in the context of multimodal networks and transient networks with reversible crosslinks.

Non-enzymatic browning (NEB) due to the Maillard reaction (MR) was studied in a closed starch/glucose/lysine model system (20 g kg−1 glucose, 10 g kg−1 lysine) in order to analyse conditions favouring reactivity during an industrial process of pasta VHT (very high temperature) thermal treatment. The closed model pastes gave data on the NEB progress during the pasta drying cycle as a function of temperature, time and water activity (aw). Indicators such as headspace CO 2 , optical density and colour showed an increase of MR as the initial aw increased from 0.50 to 0.91. During the initial stages of drying, a combination of high temperatures and high aw led to the most likely conditions for NEB. © 1999 Society of Chemical Industry

Technological performance of wheat flour varies among different wheat varieties. Gluten plays a key role within the solid phase of dough in the formation and the retention of gas bubbles during breadmaking. Rheological tests are usually performed to predict breadmaking potential. The aim here was to investigate the ability of ultrasound to discriminate wheat doughs based on breadmaking qualities. The ultimate goal is the development of an online quality control system currently unavailable in the baked goods industry, rendering this work innovative. Samples were prepared from a strong wheat flour, with one control sample and one added with inulin and distilled monoglycerides, producing doughs of distinct breadmaking quality. Doughs were subjected to density determination, elongation tests, and ultrasound analysis. The ultrasound tests were performed in the frequency range of 300 kHz – 6 MHz. Ultrasonic phase velocity increased with increasing frequency to about 2 MHz, becoming constant and then decreasing from 3 MHz for the control sample. Distinct differences in attenuation coefficient between the fibre-enriched and control doughs were observed. Ultrasound can potentially add to a better understanding of dough quality and can discriminate between doughs of contrasting properties.

Mayonnaises are oil in water emulsions with a texture that is particularly appreciated by consumers. The actual nutritional trend towards low-calorie foods has increased the interest in fat substitutes without altering the consistency of the product. From this point of view rheological properties may give a quantitative contribution to texture characterization and control when using different formulations. The rheological approach has been applied to typical commercial normal and light mayonnaises with a fat content ranging from 76 to 48%. These materials have shown a viscoelastic behaviour that was measured by means of both oscillatory and creep-recovery tests. The storage modulus, the compliance and the yield stress were found to increase when increasing the fat content. A modified Bolhin theory was used to relate structural parameters to rheological dynamical measurements. Thus the emulsion stability was quantified by means of a pseudoplastic-coordination number (z) and the value of G′ at 1 Hz . From the creep test the value of the yield stress was determined and in the case of the light mayonnaise was very close to a normal emulsion whereas the corresponding viscoelastic properties were very different. This implies that to reproduce an assumed texture, it is necessary to perform all the tests outlined.