Extruded Wheat Starch Research Articles

Effect of extruded starches on the structure, farinograph characteristics and baking behavior of wheat dough

Extruded wheat starch (ES) was obtained by a single-screw extruder to determine its effect on the farinograph, structural properties and baking behaviors of wheat dough. XRD analysis showed that increasing extrusion temperature made the crystalline peaks less pronounced due to the partial gelatinization. In terms of FTIR results, the molecular order of extruded starch was lower than that of native starch. The dough development time was decreased from 3.2 min to 2.7 min while the stability time was increased from 14.4 min to 15.5 min, as 70 ES were added. It was accompanied with increasing levels of α-helix and β-turn transferred from the decreased content of random coil and β -sheet. These effects in bread were to increase loaf volume and reduced loaf hardness. These results indicated that extruded starch had a good potential for producing a high-quality bread.

An evaluation of the mechanical performance of extruded wheat starch loose fill

During the distribution process, products are continuously exposed to dynamic forces resulting from vehicle vibrations as well as drops and shocks from various types of handling. In order to reduce the adverse effects of such loads, protective packaging or cushioning materials are used. Engineered packaging materials are generally petroleum based (plastics) and present significant environmental concerns after their disposal. The use of environmentally friendly, bio‐compostable, alternatives is a logical development; however, if the salient protective characteristics of these materials are not well established, their use may lead to greater losses and a larger environmental impact through product loss. This paper introduces a comprehensive approach for the mechanical characterisation of alternative cushioning materials, which includes the effects of environmental conditions. The procedure is used to compare the performance of loose fill starch beads with a commonly used engineering cushioning material, namely medium density, closed cell polyethylene. The results show that the starch beads can offer a viable alternative to the engineered cushioning materials as they provide reasonable overall cushioning character, albeit over a narrower stress range when compared with the polyethylene cushions. The loose fill was also shown to perform in terms of vibration damping and resistance to sustained dynamic loads for low static stress levels.

Hydrolysed pea proteins mitigate in vitro wheat starch digestibility

Possible inhibitory effects on wheat starch amylolysis of native and hydrolysed pea protein, in an extruded wheat snack matrix were investigated by using a combined in vitro dynamic gastric model (DGM) and a static duodenal digestion model (SDM). The matrix was prepared by blending wheat flour and pea proteins (12%, w/w) in their native or proteolyzed forms. Extruded snacks were ground, mixed with saliva and poured in the DGM-fundus. The slurry in the antrum was released simulating the in vivo emptying of the stomach and subsequently transferred to the SDM. Native pea protein did not influence the release of soluble glucans and glucose after complete gastric emptying into the vessel. However, the addition of hydrolysed pea protein significantly reduced starch amylolysis at the first 40 min of digestion. No inhibitory effect was observed at later digestion times. Fourier-Transform Infrared (FTIR) analysis of the extruded samples clearly indicated enhanced starch-protein interactions, where the magnitude of interaction found to be greatest in the blend with hydrolysed pea protein through hydrogen bonding. At our knowledge, this is the first study using DGM to determine the effect of exogenous protein on the digestibility of extruded wheat starch. The data suggested the possibility of using protease hydrolysed pea protein as an ingredient to formulate low glycemic food products.

Microwave foaming of starch-based materials (II) thermo-mechanical performance

The thermo-mechanical performance of extruded wheat starch/flour containing different additives was examined via microwave-heated thermo-mechanical analysis. Additionally, the dielectric property of the wheat starch-based materials was also studied using a microwave calorimeter. It has been found that when glycerol or polyvinyl alcohol was used as single additive in wheat starch, a content limit existed and using the additives at a concentration higher than the limit will lead to deterioration of the material’s microwave foamability. A good initial thermal expansion is essential for a proper foaming of the wheat starch-based materials; however, high enough dielectric loss factor (ɛ″) is also required for the formation of foam structure under microwave radiation. Glass transition temperature ( Tg) for the extruded wheat starch materials was detected by microwave thermo-mechanical analysis at about 75–95°C when heated at 15°C/min; and for the foamable formulations, the foaming temperature ( Tf) is generally 10–20°C higher than the corresponding Tg. Impurities like proteins play important roles in the microwave foaming of extruded wheat flour. Overall, the extruded wheat flour with additives is more difficult to foam under microwave heating than the wheat starch extruded from the similar formulations.

In-line Measurement of the Viscous Behaviour of Wheat Starch During Extrusion. Application to Starch Cationisation

Abstract A specific twin channel slit die was used to measure in-line the viscous behaviour of an extruded wheat starch. This allows to put in evidence the influences of temperature, water content and specific mechanical energy (SME). The proposed rheological law permits to satisfactorily predict the viscosity of a wheat starch for any processing condition. Original results are presented for the behaviour of cationic starches obtained by reactive extrusion.

Effects of soy protein isolate, acid-hydrolysed vegetable protein and glucose on the volatile components of extruded wheat starch

The volatile components produced in wheat starch containing 1% soy protein isolate (SPI), and wheat starch/1% SPI combined with 1% glucose, 1% acid-hydrolysed vegetable protein (aHVP), or 1% glucose and 1% aHVP, extruded under different processing conditions (temperatures of 150 or 180 °C and moisture content of 16% or 20%), were identified by gas chromatography–mass spectrometry (GC–MS). Gas chromatography olfactometry (GCO) was used to assess the odour intensity of volatile components present in the starch/glucose/SPI and starch/glucose/SPI/aHVP extrudates obtained at 180 °C. In total, 94 compounds were identified in the eight extrudates. The smallest number (31) was found in the extrudate of the starch/glucose/SPI feedstock processed at 150 °C and the largest (64) in the extrudate of the starch/SPI feedstock processed at 180 °C. Lipid degradation products, such as alkanals, 2-alkanones, 2-alkenals and 2,4-alkadienals, were present in all extrudates in significant quantities. Strecker aldehydes were also present in all extrudates; however, in those extrudates containing aHVP, these compounds were quantitatively the dominant components. Maillard reaction products, such as pyrroles, pyrazines and oxazoles, were mainly found in extrudates containing aHVP whereas sulphur-containing aliphatic compounds were found in all extrudates. The production of the Maillard reaction products and sulphur-containing compounds was favoured by extrusion at 180 °C. Sensory analyses showed that each of the eight extrudates had different odours, and that the extrudates containing both glucose and aHVP possessed the highest overall odour intensity. In addition, SPI was found to have a modifying effect on the volatile content and odour of extrudates also containing glucose and aHVP.

Effects of glucose and acid-hydrolysed vegetable protein on the volatile components of extruded wheat starch

The volatile components produced in wheat starch, and wheat starch combined with 1% glucose, 1% acid-hydrolysed vegetable protein (aHVP) or 1% glucose and 1% aHVP, extruded under different processing conditions (temperatures of 150 or 180 °C and moisture content of 16% or 20%) were identified by gas chromatography-mass spectrometry (GC-MS). Gas chromatography olfactometry (GCO) was used to assess the odour intensity of volatile components present in the starch and starch/glucose/aHVP extrudates obtained at 180 °C. In total, 70 compounds were identified in the eight extrudates. The smallest number (24) was found in the extrudate of the starch/glucose mixture and the largest number (67) in the extrudate of the starch/glucose/aHVP mixture, both processed at 180 °C. Lipid degradation products, such as alkanals, 2-alkanones, 2-alkenals and 2,4-alkadienals, were present in all extrudates in significant quantities. However, in those extrudates containing aHVP, Strecker aldehydes were quantitatively the dominant components. Maillard reaction products, such as pyrroles and pyrazines, were only found in extrudates containing both glucose and aHVP whereas sulphur-containing aliphatic compounds were found in all extrudates containing aHVP. The production of the Maillard reaction products and sulphur-containing compounds were favoured by extrusion at 180 °C. Sensory analyses showed that each of the eight extrudates had different odours, and that the extrudates containing both glucose and aHVP possessed the highest overall odour intensity.

Binding of volatiles to extruded starch at low water contents

The binding of volatiles to extruded wheat starch samples in the glassy and rubbery states was studied to determine whether there were substantial differences in binding behaviour between the two states. Theory suggests a significant change in the mobility of some molecules between the rubbery and glassy states which may affect the uptake of volatiles. Extruded samples containing 19-43% water were prepared and characterized by DSC and X-ray diffraction to ensure that samples were comparable in terms of starch gelatinization and had not retrograded. The physical state of samples (glassy or rubbery) was determined by calculation from the Couchman--Karasz equation. Uptake of volatiles was followed by measuring headspace concentration over time using automated sampling, which reduced variability to 5%. Volatile uptake was followed for periods ranging from 2 to 50 hours in starch samples of different water contents in the glassy and rubbery states, with a range of surface areas and also in starch/sucrose extrudates. The binding curves showed rapid initial uptake of diacetyl followed by a further, slower uptake. Heptane and 3-methylbutanal were bound to a lesser extent. The glassy state samples bound diacetyl more slowly than the rubbery samples although there was no available water (as measured by DSC) in either the glassy (19% water) or rubbery (26% water) samples. This suggests that the physical nature of the glassy state, as well as water content, has an effect on volatile binding.

Binding of volatiles to extruded starch at low water contents

The binding of volatiles to extruded wheat starch samples in the glassy and rubbery states was studied to determine whether there were substantial differences in binding behaviour between the two states. Theory suggests a significant change in the mobility of some molecules between the rubbery and glassy states which may affect the uptake of volatiles. Extruded samples containing 19–43% water were prepared and characterized by DSC and X-ray diffraction to ensure that samples were comparable in terms of starch gelatinization and had not retrograded. The physical state of samples (glassy or rubbery) was determined by calculation from the Couchman–Karasz equation. Uptake of volatiles was followed by measuring headspace concentration over time using automated sampling, which reduced variability to 5%. Volatile uptake was followed for periods ranging from 2 to 50 hours in starch samples of different water contents in the glassy and rubbery states, with a range of surface areas and also in starch/sucrose extrudates. The binding curves showed rapid initial uptake of diacetyl followed by a further, slower uptake. Heptane and 3-methylbutanal were bound to a lesser extent. The glassy state samples bound diacetyl more slowly than the rubbery samples although there was no available water (as measured by DSC) in either the glassy (19% water) or rubbery (26% water) samples. This suggests that the physical nature of the glassy state, as well as water content, has an effect on volatile binding. © 1998 John Wiley & Sons, Ltd.

A comparison of wheat starch, whole wheat meal and oat flour in the extrusion cooking process

A comparison of the effect of the process variables temperature and moisture on the extrusion behaviour of wheat starch, whole wheat meal and oat flour was made. The lipids content of wheat starch and whole wheat meal was also adjusted to 4% and 8% using wheat germ oil (WGO) to study its effect and to compare with oat flour, which has an oil level of about 8%. The extruder pressure, torque and specific mechanical energy and extrudate properties of expansion, water absorption index (WAI) and water solubility index (WSI) were analysed. Second-order polynomials were used to model the extruder response and product properties of extruded wheat starch and whole wheat meal with the process variables and WGO level. Wheat starch and meal behaved broadly similarly but differed from oats in pressure, expansion, WSI and WAI in their response to moisture content and temperature. Addition of WGO to wheat starch increased the expansion, whereas it had little effect on the wheat meal. WGO increased the upper bound WSI and decreased the lower bound WAI for starch or meal.

Effect of digestible carbohydrates on protein/energy utilization and on glucose metabolism in rainbow trout ( Salmo gairdneri R.)

Diplicate groups of rainbow trout were fed low-protein (38%) diets containing high levels (38%) of five different carbohydrate sources (raw starch, extruded corn, extruded wheat, extruded corn starch or extruded wheat starch). A modified pair-feeding method was used to allow equal intakes of protein and of digestible energy by each group of fish. Growth parameters were followed over a period of 18 weeks; the digestibility of the diets, nitrogen and energy balances, and the respiratory and ammonia quotients of fish fed the different diets were determined. To study the long-term effects of dietary carbohydrates, plasma glucose profile and its control by bovine insulin was followed in fish fed over 30 weeks with selected test diets. The results show that inclusion of extruded cereals or extruded starch improves availability of dietary energy. High levels of carbohydrates to not adversely affect overall growth or nutrient retention efficiencies. Long-term feeding with carbohydrate-rich d diets does not confer on trout any adaptive capacity to regulate postprandial glycemia levels. Respirometric measurements appear to provide interesting data on the metabolic utilization of body substrates.