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Physical and hydration properties of expanded extrudates from a blue corn, yellow pea and oat bran blend
Abstract
Extrudates were prepared from a blue corn, yellow pea and oat bran blend employing a twin-screw extruder. Response surface methodology was used to evaluate the effect of extrusion-cooking process independent variables: screw speed (SS, 300–400 rpm), die temperature (DT, 120–160 °C) and feed moisture content (FMC, 20–25%) on the system parameters (specific mechanical energy and product temperature), physical properties (sectional and longitudinal expansion indices, porosity, hardness and color attributes), hydration properties (water absorption and solubility indices, and pasting properties), microstructure and x-ray diffraction. Although, system parameters, physical and hydration properties were affected by SS and DT, the greatest effect was due to the FMC. Indicating this way lubricant effect as the preponderant factor controlling extrusion effects on raw material. Decreased FMC increased specific mechanical energy, expansion, soluble compounds; and decreased hardness, time to raw peak viscosity, raw peak, total setback and final viscosities. Data were also analyzed with a principal component analysis, showing that 74.67% of data variability can be explained defining two components corresponding to the 62.10% that was due to mechanical effect and 12.57% that was related to thermic effect. Conditions obtained for multiple optimization were: 158.64 °C, 371.98 rpm, 18.38% FMC.
... The main extrusion cooking variables affecting product quality are the moisture content of the feed material, the extrusion temperature, and the screw speed. Therefore, several studies [65,69,[97][98][99][100][101][102][103] have aimed to find the optimal combination of those parameters to ensure the best quality for each type of branenriched product (Table 1). ...
... Feed moisture content was highlighted as the variable with the highest influence over extrusion parameters and product properties (mainly hardness) in an optimization study [100]. Decreased moisture content increases SME and results in low density and high expansion rate [69,97,100]. ...
... Feed moisture content was highlighted as the variable with the highest influence over extrusion parameters and product properties (mainly hardness) in an optimization study [100]. Decreased moisture content increases SME and results in low density and high expansion rate [69,97,100]. The expansion rate is also affected by die temperature and screw speed: high values for both these variables produce more expanded extrudates [100]. ...
The incorporation of milling by-products, in particular bran, into starch-based extruded snacks allows manufacturers to address two consumer demands at once, i.e., those for goods that are more sustainably produced and of higher nutritional value. However, the higher fiber content in bran than in refined cereal flours poses a limit to the amount that can be included without compromising the quality of extruded snacks, which crucially depends on expansion. Thus, several studies have focused on the effect of bran on the physicochemical characteristics of extruded snacks, leading to the need to review the recent findings in this area. Opportunities, challenges, and potential solutions of bran-enriched snacks are addressed, and several current knowledge gaps are highlighted. Specifically, the first part of the review presents the effects of extrusion cooking on bran’s compositional aspects, focusing on structural changes and product quality. After summarizing the main quality traits of extruded snacks (e.g., expansion rate, bulk density, and textural attributes), the effects of bran enrichment on the physical and sensory characteristics of the final product are discussed. Finally, bran pre-treatments as well as processing optimization are discussed as approaches to improve the quality of bran-enriched snacks.
... Schmid et al. [15] and Menchaca-Armenta et al. [2] suggest that a high moisture content promotes the polymerization of phenolic compounds, which affects their extractability and antioxidant activity. In contrast, processing under a low moisture content (<15%) generates simpler, more extractable forms of the phenolic compounds, and this could be further enhanced in combination with high shear stresses and temperatures [28,30,31]. These chemical changes are associated with structural changes in materials subjected to extrusion or other thermal processes, thereby increasing the release of bioactive compounds contained in the cell wall [2,6,15,27]. ...
... These chemical changes are associated with structural changes in materials subjected to extrusion or other thermal processes, thereby increasing the release of bioactive compounds contained in the cell wall [2,6,15,27]. The processing of blue corn, alone or in a mixture with other ingredients, such as beans, by extrusion-cooking, or in combination with other technologies, has been reported [2,30,32,33]. The physical properties of the food matrix are also dependent on shear stress, temperature, and pressure gen-erated in the extruder chamber. ...
... Intermediate MC values and low temperatures increases the P3GC, while high temperatures and low moisture caused a reduction (Figure 2c). MC increases reduce the degradation of anthocyanins, because water acts as a lubricant during extrusion [27,30,33]. The prediction model shows a saddle behavior with a value of 11.94 mg P3G/kg at 153.08 °C, 29.83% MC, and 62.23 rpm. ...
The effect of extrusion cooking on bioactive compounds in third-generation snacks (TGSE) and microwave-expanded snacks (MWSE) prepared using black bean, blue maize, and chard (FBCS) was evaluated. FBCS was extruded at different moisture contents (MC; 22.2–35.7%), extrusion temperatures (ET; 102–142 °C), and screw speeds (SP; 96–171 rpm). Total anthocyanin content (TAC), contents of individual anthocyanins, viz., cyanidin-3-glucoside, malvidin-3-glucoside, pelargonidin-3-glucoside, pelargonidin-3-5-diglucoside, and delphinidin-3-glucoside chloride, total phenolic content (TPC), antioxidant activity (AA), and color parameters were determined. TAC and individual anthocyanin levels increased with the reduction in ET. ET and MC affected the chemical and color properties; increase in ET caused a significant reduction in TPC and AA. Microwave expansion reduced anthocyanin content and AA, and increased TPC. Extrusion under optimal conditions (29% MC, 111 rpm, and 120 °C) generated products with a high retention of functional compounds, with high TAC (41.81%) and TPC (28.23%). Experimental validation of optimized process parameters yielded an average error of 13.73% from the predicted contents of individual anthocyanins. Results suggest that the TGSE of FBCS obtained by combining extrusion and microwave expansion achieved significant retention of bioactive compounds having potential physiological benefits for humans.
... Debido al auge que han tomado los productos naturales en los últimos tiempos, la producción de botanas busca obtener productos más nutritivos, con un mejor aporte de proteínas, calorías, fibra, ácidos grasos esenciales, vitaminas y minerales. Se han realizado, mediante las combinaciones con leguminosas, muchos intentos para elevar el valor nutritivo de la proteína en los productos a base de maíz (Lazou et al., 2011;Jacques-Fajardo et al., 2017). ...
... El chícharo contiene altos niveles de proteínas, fibras dietéticas, hidratos de carbono complejos, isoflavonas y ácido fólico y es bajo en grasa y sodio. La mayoría de estos componentes también están asociados con beneficios para la salud, como las proteínas con efectos hipocolesterolémicos, y las isoflavonas que ayudan en la prevención de la osteoporosis y ciertos tipos de cáncer (Nayak et al., 2011;Jacques-Fajardo et al., 2017). ...
... Es un subproducto rico en fibra, que contiene las capas externas fragmentadas del grano junto con cantidades variables del endospermo almidonado. En contraste con el salvado de trigo, el salvado de avena es rico en fibra soluble en agua y pobre en celulosa y lignina (Jacques-Fajardo et al., 2017). El mayor inconveniente relacionado con la incorporación de algún tipo de fibra en los alimentos, es el efecto que produce sobre sus propiedades físicas y sensoriales. ...
Resumen El objetivo de este estudio fue evaluar el efecto de la temperatura y tiempo de freído sobre las propiedades fisicoquímicas: porcentaje de humedad, H; cambio neto de color, ΔE; contenido de grasa, G; índices de absorción, IAA; solubilidad en agua, ISA; densidad aparente, DA; y dureza, D, de un alimento frito tipo botana preparado con una mezcla de harinas de maíz nixtamalizado (HMN), harina de chícharo (HC) y salvado de avena (SA), hidratada al 47%. El estudio mostró que DA y H disminuyeron, mientras que ΔE e IAA se incrementaron con el aumento de la temperatura y el tiempo de freído. Los cambios en ISA y D resultaron estadísticamente no significativos. El análisis de componentes principales, mostró que el 83% de la variabilidad de los datos se puede explicar debido a dos componentes: temperatura (56%) y tiempo (28%). El análisis sensorial mostró que la botana elaborada a 165 °C y 198 s obtuvo mayor aceptación, resultando un alimento con alto contenido de proteína y bajo contenido de grasa.
... Moreover, Wani & Kumar, 2016a reported that product responses were significantly affected by blend moisture content, die temperature and screw rotation speed, while extrusion of pea and oat flours (Wani & Kumar, 2016a). However, the existing studies containing blend of pea and oat ingredients are based on milled flours and not enriched-fractions (Jacques-Fajardo et al., 2017;Sajad Ahmad Wani & Kumar, 2016a). Therefore, the goal of this study was to explore the impact of extruder process parameters such as die temperature and blend moisture content on snack quality using peaand oat-rich fractions enriched in starch, protein and fiber. ...
... materials (Jacques-Fajardo et al., 2017;Philipp et al., 2018;Sajad Ahmad Wani & Kumar, 2016b). The raw-material blends were processed in a twin screw extruder (co-rotating KETSE 20/40 Brabender GmbH and Co. KG, Duisburg, Germany) containing a screw diameter of 2 cm and a length of 40 cm (L/D ratio of 20:1). ...
... The range of SME achieved was between 87.9 and 115.8 Wh/Kg, being in agreement with results obtained in this study. Chinnaswamy at al., 1988 and Jacques-Fajardo et al., 2017 also found similar SME values (61.1 and 149.8 Wh/Kg) with a comparable blend composition (pea, oat, corn) and similar process conditions (Chinnaswamy & Hanna, 1988;Jacques-Fajardo et al., 2017). Higher SME values can be linked to the composition of the raw material mix, with for instance, higher content in proteins and lower in starch that is responsible for a decrease in the blend viscosity (Alam et al., 2016). ...
The objective of this study was to explore the production of an expanded snack entirely based on pea- and oat-rich fractions using the extrusion technology. The effect of the die temperature, HZ6 (146–175 °C) and blend moisture content, MC (11.2 and 16.8% dry basis) were investigated aiming at maximizing expansion, while obtaining a good texture and pleasant sensory perception. The best response was obtained with a HZ6 of 160 °C and MC of 11.2%. MC was the parameter that most influenced final extrudate properties/responses. The gross composition of the raw-material was not modified by extrusion processing apart from a decrease in glucose and fructose content attributed to Maillard reactions. The snacks contained 3.5 g of β-glucan per portion. This is high enough for both approved EFSA health claims: lowers cholesterol and reduces post-prandial glucose response.
... is pattern has been reported in several studies of second-generation extruded snacks where the hardness is the average force required for a probe to penetrate the extrudates. Besides that, the hardness of the extrudates increased as the feed moisture content increased [30][31][32][33]. e hardness of the expanded extrudates is associated with the expansion and cell structure of the food products. ...
... Samples F20/O80/M13 and F0/ O100/M13, which were extruded at relatively low tempering moisture contents (13%), had larger cells with lower BD and hardness and higher EI values. Jacques-Fajardo et al. [33] reported that in the extruded samples made from corn, peas, and oat bran, the samples with lower tempering moisture content also had higher EI and larger cells. Bisharat et al. [45] and Silva et al. [8] reported that extrudate expansion results from the internal pressure of water that remains inside the matrix during gelatinization and is released when the product exits the extruder die, causing expansion, larger cells, and thinner cell walls, which in turn reduces the hardness of the extrudates. ...
The oca ( Oxalis tuberosa ) is a tuber with high starch content and excellent antioxidant properties, which can be used in the production of extruded products; however, starch-rich products can be improved nutritionally through the incorporation of fibers that can result in extrudates with beneficial health properties. The aim of this work was to develop a mixture of oca ( Oxalis tuberosa ) and oat extrudate flours and evaluate the antioxidant and physicochemical attributes. The results showed that a higher moisture content increased the hardness, water absorption index, and density of the extrudates; however, the solubility and expansion indexes showed an inverse pattern. The addition of oat fiber had the opposite effect from moisture content on the physicochemical properties mentioned above. The cellular antioxidant activity (CAA) of the extrudates decreased when the oat fiber increased. An inverse pattern was observed when the moisture concentration was increased. The starch hydrolysis percentage and glycemic index decreased significantly when the fiber content increased. Oat fiber contributed 67.29% and 65.04% to these parameters, respectively. Oat fiber exerted a greater effect than moisture on the collets extruded in this study according to factor contributions.
... Between these changes can be mentioned the gelation of starches, denaturation, or reorientation of proteins, fat melting, or expansion of the food structure [15]. As previously mentioned, there have been many studies on the effect of the extrusion process on the physicochemical properties of starch and proteins [14,[16][17][18][19][20]. However, few works have used extrusion to obtain cereal and legume powders as an ingredient. ...
Legumes are a good source of vegetal protein that improves diets worldwide. Cowpea has been used as fortification agents in some traditional corn foods in developing countries such as Colombia. The work aimed to evaluate the physicochemical properties of extruded mixtures of corn and cowpea flours to assess the use of these mixes as vegetable protein ingredients. Corn flour was mixed with 15, 30, and 50% of cowpea flour and extruded for this proposal. After extrusion, mixtures were ground to produce a powder. Techno-functional properties of powders as water content, hygroscopicity, water absorption, fat absorption, water solubility index, swelling index, bulk density , Hausner ratio, Carr index, and porosity were evaluated in the mixtures, extrudates, and obtained powders to assess the effect of the addition of cowpea on these properties. Results showed that processing powder obtained by extrusion and drying could be used as a powder to regenerate with water as a source of protein. Moreover, storing processing samples in sections (pellet format) is convenient to avoid wetting since this format is less hygroscopic and the same mass occupies less storage volume than powders.
... In all extruded products ( Fig. 6-9), there is a significant decrease in fat. According to the authors of [22], this is due to the influence of extrusion, which significantly reduces the content of fatty acids (palmitic, oleic, linoleic, and linolenic acids) and α-, β-and γ-tocopherols compared to control. The authors associate a significant decrease in the content of fatty acids and tocopherols during extrusion with the formation of amylose-lipid complexes [16,23,24]. ...
The object of research reported in this paper is grain and leguminous crops of Kazakhstan. Grains and leguminous crops, as well as products that are made from them, are of great importance in human nutrition because they are sources of protein, fat, carbohydrates, some vitamins, and macro and microelements. They contain plant fibers, as well as a number of biologically active substances necessary for the normal functioning of the entire human body. At the same time, modern technologies for processing and manufacturing products from cereals are associated with significant losses of nutrients embedded in them by nature when producing refined products. The problem that needs to be solved is to study the impact exerted on grain crops by various processing techniques and to propose the most optimal ones that make it possible to maximally preserve the nutrients of grain raw materials laid down by nature. A comparative study of the following grain processing techniques was carried out: micronization, extrusion, germination, and fine grinding. Processing modes have been proposed, which could significantly reduce the loss of useful substances of the grain. The chemical and vitamin composition of processed products has been studied. It was established that fine grinding and extrusion processing are the most acceptable because they allowed the use of grain without separating the shells containing the main nutrients of the grain. The suggested processing modes contribute to the production of grain bases and additives with the most optimal vitamin-mineral formulation. This study's results contributed to a better understanding of the impact of the examined techniques for processing grains and legumes on the vitamin-mineral complex of the resulting products. Grain processing modes can be recommended for practical application.
... However, Gonzalo et al. described different conclusions . [45] They explained that A was the most important factor for FV. This may be related to the low moisture content of raw materials. ...
Rice analog is a kind of ready to eat food prepared by twin-screw extruder. Few people study the drying process of wet-extruded foods and the effects of extrusion parameters on product properties based on multi-level. In this research, the experimental investigation of drying was a two-stage procedure: the evaporation of free water rapidly at first and then expansion at high temperature. The influence of the interaction of extrusion parameters on the physiochemical properties was analyzed by using response surface methodology and principal component analysis. Results showed that with regard to microwave drying in the first step, improving drying efficiency, but made the water distribution uneven. The first and second drying had opposite effects on solubility, peak viscosity, and setback of extruded products. This impact of feeding speed was most evident in hardness. Temperature was the most predominated factor for residence time, final viscosity, water-holding capacity, hardness, adhesiveness, and chewiness. The influence of interaction of extrusion parameters to the properties of rice analogs was orderly. Except for the interaction between feeding speed and screw speed, chewiness was influenced deeply by other interactions. The pasting properties were negatively correlated with elasticity, cohesion, and adhesiveness, but positively correlated with compression work. The adhesiveness had a good reference for optimizing processing parameters and control the properties of extruded foods.
... Optimum conditions for the preparation of snacks were 158.64°C, 371.98 rpm, 18.38% feed moisture. [45] There is a great effect of extrusion processing conditions on the total phenolic contents, antioxidant activity (AA), and pasting properties of the extrudates. An investigation on the effect of extrusion processing conditions such as moisture content (12-16%), barrel temperature (90-110°C), and screw speed (100-200 rpm) was studied for the above said parameters. ...
Malnutrition is directly linked to the economic and social living standard of the people. It is the major cause of morbidity and mortality among the children, especially in the developing countries. The world population is projected to grow to around 9 billion by 2050 which will further escalate malnutrition. Snacks are becoming more and more popular and have a strong association with nutritional status of the young population. Extruded snacks have very low moisture (4–6%) and water activity (0.138) making them shelf stable. Shelf stable, nutrient dense products deemed to be ideal to alleviate malnutrition in the developing world. It is important to consider these healthy snacks for the provision of macro and micronutrients especially to the nutritionally vulnerable segment of population. Modern extrusion technologies have paved the way to use various nutrient-rich constituents to make attractive products. Analysis of supercritical fluid extrusion processed snacks has resulted in superior physical and textural properties while retaining the added macro and micronutrients. Nutrient-rich snacks produced through extrusion processing have been used for nutrition interventions along with community-based educational campaigns to mitigate malnutrition. This literature pertains the prevalence of malnutrition along with the usefulness of healthy extruded snacks against malnutrition.
... including mixing, coking, cooking, kneading, shearing, sharping and forming inside the extruder. The extruder is considered a high-temperature short-time bioreactor that transforms a variety of raw ingredients into modified intermediate and finished food products due to the thermal effect and the sear stress [4,5]. Currently, there are studies on the bioavailability of phenolic compound (PC) promoters in cereals; however, there is no prior research on the ability of EP to increase the content of PCs and antioxidant activity (AOX) in WB [6]. ...
The extrusion process (EP) consists of heat and mechanical treatments under different conditions of moisture, shear, and pressure
and rapidly causes structural alterations and changes in the functional properties of the extruded material. The aim of this study
was to evaluate the effect of extrusion conditions and optimize the wheat bran extrusion conditions to achieve the greatest content
of phenolic compounds and antioxidant activity using response surface methodology. The EP factors evaluated were feed
moisture (FM) (25–33.54%) and final extrusion temperature (T) (140–180 °C). The properties evaluated in the extruded material
were bound total phenol content (BTPC), total phenolic compounds and antioxidant activity (AOX). Analysis of variance
(ANOVA) and response surface methodology were used in the evaluation. The determination coefficients, (FM)2 and (T)2, very
significantly affected the BTPC and bound 2,2-diphenyl-1-picrylhydrazyl content (BDPPHC). The optimization was performed
by overlaying two contour plots to predict the best combination regions. The optimized extrusion conditions were the following:
FM = 30% and T = 140 °C, which provided BTPC = 3547.01 μgGAE/g (predicted: 3589.3 μgGAE/g) and BDPPHC = 9.5
μmolTE/g (predicted: 10.4 μmolTE/g); and FM = 30% and T = 180 °C, which provided BTPC = 3342.3 μgGAE/g (predicted:
3727.7 μgGAE/g) and BDPPHC = 9.5 μmolTE/g (predicted: 9.3 μmolTE/g). The EP increased the phenolic compounds and
AOX, and enhancement of these properties in wheat bran products could make them functional foods.
This study was carried out to produce high‐quality protein expanded extrudates from corn meal‐chickpea flour blends (DCM‐CPF) and corn meal‐yellow pea concentrate blends (DCM‐YPC) by twin‐screw extruder. Effect of barrel temperature and screw speed on DCM and DCM‐CPF, DCM‐YPC ratio and feed moisture content (16%‐20%) on expansion were determined. The higher screw speed (SS) and barrel temperature increase specific mechanical energy (SME), specific longitudinal expansion (SLE), expansion ratio (ER), hardness and reduced piece density (PD) of degermed cornmeal extrudates significantly, and reduce all the viscosities than raw material. When screw speed at 550 rpm and barrel temperature at 130°C, the higher legumes addition decreased the SME value, SLE, ER and increased hardness, PD, all viscosities for DCM‐CPF extruded products, but decreased the SLE, ER and increased SME value, PD, hardness, all viscosities for DCM‐YPC extruded products. The increasing of feed moisture content from 16%‐20% resulted in the PD and hardness increased signicantly (p<0.05) and SME, SLE, ER, peak viscosity values decreased for DCM‐CPF extrudates, whereas SLE, hardness, peak viscosity values increased, ER decreased and there wasn't significantly change in PD for DCM‐YPC extrudates. As compared to DCM‐CPF‐III, DCM‐YPC‐III exhibited better expansion with higher in vivo protein digestibility corrected amino acid score (IV‐PDCAAS) and PD per serving (30 g). This article is protected by copyright. All rights reserved
A mixture of blue corn, black bean, and chard with a moisture content (MC) of 22.3–35.7% was extruded at different extrusion temperatures (ET) (102–142°C) using screw speeds (SP) of 96–172 rpm, and the extruded mixtures were subsequently expanded using microwave radiation to produce third‐generation (3G) snacks. The degree of starch gelatinization (DG); in vitro starch digestibility (SD); specific mechanical energy (SME); physical properties: radial expansion (RE), flexural modulus (Ef), and bulk density (BD); and rheological properties: storage modulus (G′) and loss modulus (G″) were evaluated and optimized. In addition, X‐ray and microstructure analyses were studied to correlate the chemical and structural changes. The SP and MC affected most variables in the unexpanded snack (UETS) and microwave‐expanded snacks (MWES). Increased MC resulted in UETS with low SD, DG, rheological properties and mechanical resistance. An increase in SP at low MC resulted in MWES with high RE, low BD, and Ef while an increase in MC lowered SD. Micrographs and X‐ray diffraction spectra revealed that the extrusion results in a V‐type starch crystalline structure. The optimal conditions (24% MC, 133 rpm, and 122°C) resulted in good expansion and moderate SD, DG, and SME products. This article is protected by copyright. All rights reserved
This research was carried out to produce high‐quality protein breakfast from cornmeal‐chickpea flour (DCM‐CPF) and cornmeal‐yellow pea concentrate (DCM‐YPC) blends by twin‐screw extruder. Effect of CPF level (25%, 50%, 75%) and YPC level (10%, 20%, 40%) and in‐barrel moisture content (IBM) (25%, 28%, 31%) on expansion were determined. Under 25% IBM, the extrudates with higher CPF (75%) and YPC (40%) amount had the lower torque, specific mechanical energy (SME), specific longitudinal expansion (SLE), expansion ratio (ER). And piece density (PD) and bulk density (BD) were higher than low CPF and YPC level significantly (p < 0.05). The increasing of IBM from 25%‐31% resulted in increased of PD, BD, hardness (p < 0.05) and decreased of SLE, ER (p < 0.05) and degree of gelatinization for extrudates. The increase of IBM resulted in the decline of peak viscosity and breakdown. The results showed that high‐quality protein extrudates exhibited acceptable physiochemical properties.
The effects of extrusion on the physicochemical properties of a mixture of blue corn, black bean, and sweet chard (MBBC) used for indirectly extruded snacks (PECB) and microwave-expanded snacks (MEPM) were evaluated. MBBC was conditioned at moisture content (MC) of 22.2–35.7%, extruded at temperature (ET) of 102–142 °C, and screw speed (SP) in the range of 96–171 rpm. The water absorption index (WAI), water solubility index (WSI), expansion index (EI), final viscosity (FV), setback values, total anthocyanin (TAC), hardness, FT-IR, X-ray analysis, and microstructure were evaluated. TAC increased with the reduction of ET of PECB and MEPM. Reductions in MC and increases in SP caused an increase in EI, WAI, and WSI, while PV and setback values showed contrasting behaviors. Micrographs revealed that extrusion destroys the granular structure of starch EMCB-generated. FT-IR showed that extruded samples increased the intensity of bands at 994 and 1016 cm⁻¹ in comparison to raw starch, and can be observed V-type diffraction pattern. The predicted optimal conditions were obtained at 133 rpm, 25% MC, and 122 °C. Under these conditions, extruded products had greater retention of anthocyanins (34%) with adequate rheological parameters, which resulted in a maximum expansion of the extrudates.
In this study, steam explosion (SE) was used to process Qingke (highland hull‐less barley). Under the optimum conditions of steam pressure (P) of 2.34 MPa, processing time (T) of 37.0 sec and initial water content (W) of 10.0%, the optimum values of expansion ratio (ER), unpopped kernel ratio (UKR), total polyphenol content (TPC), total flavone content (TFC) and antioxidant index (ABTS) were 3.24, 0.192, 3.81 mg GA/g DW, 3.24 mg rutin/g DW and 14.0 mg ASC/g DW, respectively. Optimization of physicochemical properties showed that SE resulted in excellent expansion properties of Qingke while preserving its active components and antioxidants. By comparing the analysis results of scanning electron microscopy (SEM), hydration, vitamin E, β‐glucan, pentosan, and dietary fiber of the SE treated Qingke with the raw and traditional roasting treated Qingke, SE has been demonstrated to be a better processing technology for Qingke and could well maintain the nutrients of Qingke.
Widening the range of products produced on the basis of agricultural raw materials and improving the quality of these products and increasing their nutritional value represent urgent challenges. Therefore, the production of new mass consumption products with high nutritional and biological value brings to the fore the use of local nut flour as an enriching supplement in innovative technological processes. The high nutritional value of nuts (nuts, walnuts, and peanuts) is due to their chemical composition, including lipids, a large amount of soluble proteins that are well absorbed by the human body, sufficiently large quantities of vitamin B1 and a small amount of vitamins PP and E. It is known that in peanut grains, lipids have a balanced composition of fats and acids, as well as sufficiently large amounts of essential amino acids, which makes their protein composition closer to that of animal proteins. This study considers the influence of thermoplastic extrusion parameters on the functional and physicochemical properties of extrudates in their formation process. The technological and design parameters of the process and their variation ranges are based on studies conducted on model systems. The ratio of the extrusion mixture components (formulation) is also developed. Based on the methodology for multifactorial experimental design, the variation of the volume weights, expansion rates, and mechanical specific energy expenditure of porous extrudates enriched with starch-based nut flour is studied. It has been established that the best quality indicators of the products are achieved with the minimum volume weight and the maximum expansion rate.
A novel process for the purification and recycling of CO2 (PRCO2) in a pilot scale unit was implemented and validated. The system is a 4-cycle pseudocontinuous process composed of on-line supercritical fluid extraction integrated with fractionation of extracts in three separation vessels, followed by purification of CO2 in adsorption column at subcritical conditions, and subsequent recycling of the purified CO2 with the aid of a storage tank. Turmeric and annatto were the plant matrices used for extraction and oat bran was used as adsorbent. The PRCO2 reduced the consumption of CO2 in 85.24% for annatto and 74.27% for turmeric, representing monetary savings of USD 186.40 and USD 111.83, respectively. Economical evaluation showed that the increasing of the number of cycles decreased the cost of manufacture from USD 349.60/kg to 122.67/kg for the processing of annatto and USD 91.31/kg to USD 36.56/kg for the processing of turmeric.
A central composite design using RMS (Re-sponse Surface Methodology) successfully described the effect of independent variables (feed moisture, die tem-perature and soybean proportion) on the specific param-eters of product quality as expansion index (EI), water absorption index (WAI), water solubility index (WSI) and total color difference (ΔE) studied. The regression model indicated that EI, WAI, WSI and ΔE were signif-icant (p<0.05) with coefficients of determination (R 2) of 0.7371, 0.7588, 0.7622, 0.8150, respectively. The opti-mized processing conditions were obtained with 25.8 % feed moisture, 160 °C die temperature and 58 %/42 % soybean/corn proportion. It was not found statistically changes in amino acid profile due to extrusion process. The electrophoretic profile of extruded soybean/corn mix presented low intensity molecular weight bands, com-pared to the unprocessed sample. The generation of low molecular weight polypeptides was associated to an in-creased in In vitro protein digestibility (IVPD) of the extrudate. The FTIR spectra of the soybean/corn mix before and after extrusion showed that the α-helix struc-ture remained unchanged after extrusion. However, the band associated with β-sheet structure showed to be split into two bands at 1624 and 1640 cm −1 . The changes in the β-sheet structures may be also associated to the increased in IVPD in the extruded sample. Keywords Protein changes . Extrusion cooking of soybean/ corn . Response surface methodology . Amino acid profile and electrophoresis . In vitro protein digestibility . Infra-red spectroscopy (FTIR) Introduction
Blue corn is a potential material for expanded snack production. Whole blue corn meal was mixed with corn starch and processed by extrusion to produce a third-generation snack. Optimum extrusion conditions were calculated with the response surface methodology using expansion index (EI), penetration force (PF), specific mechanical energy (SME) and total anthocyanins content (TAC). Optimum conditions (zone 1, 67°C; cooking zone, 123°C; zone 3, 75°C; feed moisture, 24.6%) were used to extrude the mixture in a single-screw extruder, and EI,PF,SME and TAC of the expanded pellet were compared against predicted optimum values. Starch structural changes in pellets and expanded were analyzed with DSC, viscosity profiles, x-ray diffraction and SEM. Extruded pellet did not differ (p>0.05) from the predicted. However, TAC was lower (p<0.05) in the expanded pellet. Structural analyses showed damage starch granular structure during extrusion and pellet expansion. Blue corn is a promising material for production of third-generation snacks.
Nixtamalized blue corn expanded extrudates were elaborated in a single screw extruder using feed moisture (FM) of 14, 15, 16, 16.5, 18.5 and 20.5%; ground corn with different particle size indexes (PSI, 83.97 and 94.15), and at a final extruder temperature of 130 and 140°C. The physicochemical properties of extrudates evaluated were moisture content, total anthocyanin and cyanidin 3-glucoside (C3G) content, color, density and expansion index. Extrudates processed at 16 and 16.5% of FM showed higher total anthocyanin and C3G contents. The extrudates processed with 16% FM, at 130°C and PSI of 83.97, showed the highest total anthocyanin content (211.1 mg · kg−1). Cyanidin 3-glucoside showed an increase (11.3%) in extrudates when compared with raw corn. The expansion index was higher for those made with FMs of 14, 15, 16 and 16.5%. The total anthocyanin and C3G contents were not correlated with any other parameter.
The effects of different concentrations of calcium hydroxide [Ca(OH)2] and calcium lactate [C6H10O6Ca] on the functional and physical properties of extruded (EF) and nixtamalised (NF) blue maize flours were evaluated. Calcium source and concentration showed no significant effects on the EF expansion index. The water absorption index (WAI) of EF decreased as the concentrations of both calcium sources increased, and NF with C6H10O6Ca had the lowest WAI. The thermal and pasting properties of NFs were higher than those of EF. NF with C6H10O6Ca showed the highest final viscosity (FinV), indicating less damage to the starch granules, and this was correlated with microscopic analysis. In contrast, the FinV of EFs was significantly affected by calcium source and concentration. Extrusion with 0.3% and nixtamalisation at 2.95% of C6H10O6Ca yielded high WAI value and the best rheological properties in maize flour, respectively. These results suggest the use of C6H10O6Ca in extrusion or nixtamalisation to produce blue maize flours for tortilla or snacks with antioxidants.
The aim of this study was to evaluate the effect of barrel temperature (BT, 98.8–141.2°C) and feed moisture (FM, 19.93–34.07%) as independent factors on physicochemical characteristics of microwave-expanded extruded third-generation (3G) snacks obtained from blue corn and corn starch. Single-screw laboratory extruder and a central, composite, rotatable experimental design were used. Both independent factors showed significance (p ≤ 0.01) on most of the analyzed responses. The mathematical models showed values of R2Adj ≥ 0.76 and p of F(model) ≤ 0.001. The optimum area of the extrusion process ranged from 120°C to 126°C for BT and from 23.8% to 25.2% for FM. In optimal conditions, the product showed an expansion index of 4.8, a penetration force of 12.42 N, a specific mechanical energy of 169.08 kJ/kg, and 71.09 mg of total anthocyanin content/kg. The developed 3G snack presented high-quality physicochemical characteristics, with the potential health benefits derived from nutraceutical characteristics (dietary fiber and anthocyanins) of the whole blue corn used.
Helical inclusion complexes of amylose with glycerol monostearate, varying in their supermolecular structure [as assessed by X-ray, differential scanning calorimetry (DSC), and cross-polarization/magic angle spinning 13C nuclear magnetic resonance] were subjected to α-amylolysis in the solid state using the Bacillus subtilis and porcine pancreatic α-amylases. The rate and the extent of hydrolysis of complexes were inversely related to the degree of organization of helices into larger domains of ordered chains in the aggregated structure; complexes with greater crystallinity were more resistant to enzymic degradation. However, even crystalline forms of complexes could be fully degraded under prolonged digestion time and high enzyme levels. Gel permeation chromatography of the enzyme-resistant fractions also revealed distributions of longer chains for the more perfected complex superstructures. The DSC and chromatography data on enzyme-resistant fractions indicated that the B. subtilis α-amylase exerts a more uniform hydrolytic action on the complexes, than on wheat starch granules. Although enzymic breakdown of amorphous amylose chains (complexed and non-complexed chain segments) in the complex structure did not alter the crystallinity of enzyme-resistant fractions substantially, it reduced their thermal stability (lower transition enthalpy and dissociation temperature).
Anthocyanin-based aqueous Andean red sweet potato and purple corn extracts were evaluated under different pH, temperature, and light conditions, and compared to commercial colorants (purple carrot, red grape, red 40, and red 3). Red sweet potato and purple carrot colorants, rich in acylated anthocyanins, showed higher stability than purple corn and red grape colorants, rich in non-acylated anthocyanins. After storage at 20 °C for 138 days, the order of stability in the pH range 0.9–4 was: red sweet potato ⩾ purple carrot > purple corn > red grape. After this storage time, red sweet potato pH 4 extracts maintained a red-violet hue. Half-lives for pH 3 extracts at 98 °C were 4.6, 4.6, 2.4, and 2.0 h for red sweet potato, purple carrot, red grape, and purple corn, respectively. The hues for purple corn pH 3 extracts were similar to those of red 40. Parameters measured included degradation index, polymeric colour, colour retention and spectral data.
Degradation parameters of purified anthocyanins from purple-fleshed potato (cv. Purple Majesty) heated at high temperatures (100-150 °C) were determined. Purified anthocyanins, prepared by removing salts, sugars, and colorless nonanthocyanin phenolics from the crude extract, were monitored and quantified using HPLC and spectrophotometry for heat-induced degradation products. Separation of colorless phenolics from the anthocyanins was confirmed using HPLC at two wavelengths, 280 and 520 nm. The degradation kinetics of purified anthocyanins followed a first-order reaction with reaction rate constants (k values) of 0.0262-0.2855 min(-1), an activation energy of 72.89 kJ/mol, thermal death times (D values) of 8.06-8789 min, and a z value of 47.84 °C over the temperature range of 100-150 °C. The enthalpy and entropy of activation were 59.97 kJ/mol and -116.46 J/mol·K, respectively. The antioxidant capacity in the purified anthocyanins, measured by DPPH and ABTS assays, was increased after the thermal treatment, indicating antioxidant activities of degradation products in the samples.
An adaptive-network-based fuzzy inference system based on color image analysis was used to estimate coffee bean moisture content during roasting in a spouted bed. The neuro-fuzzy model described the grain moisture changes as a function of brightness (L*), browning index (BI) and the distance to a defined standard (ΔE). An image-capture device was designed to monitor color variations in the L*a*b* space for high temperatures samples taken from the reactor. The proposed model was composed of three Gaussian-type fuzzy sets based on the scatter partition method. The neuro-fuzzy model was trained with the Back-propagation algorithm using experimental measurements at three air temperature levels (400, 450 and 500°C). The performance of the neuro-fuzzy model resulted better compared to conventional methods obtaining a coefficient of determination > 0.98, a root mean square error < 0.002 and a modified Schwarz-Rissanen information criterion < 0. The simplicity of the model and its robustness against changes in the input variables make it suitable for monitoring on-line the roasting process.
The effect of extrusion conditions, including feed rate (2.52-6.84 kg/h), feed moisture content (13-19% wet basis), screw speed (150-250 rpm), and extrusion temperature (150-230 degrees C) on structural properties of corn-legume based extrudates was studied. Four different types of legumes, chickpea, mexican bean, white bean, and lentil were used to form mixtures with corn flour in a ratio ranging from 10 to 90% (corn/legume). A simple power model was used to correlate porosity with extrusion conditions and material characteristics. The influence of feed rate in the extrudates porosity is incorporated into mean residence time. Porosity of extrudates was found to increase with temperature and residence time and to decrease with feed moisture content and corn to legume ratio. Screw speed did not affect extrudates properties. Expansion ratio showed a similar behavior with porosity. The addition of legumes (protein source) led to more dense products. Comparatively, the usage of white bean in mixtures for the production of snacks, led to a product with higher porosity than those with other legumes.
Double mashing for wort production is a time-consuming process that can be reduced if pregelatinized adjuncts are used. Optimal extruding conditions were determined to obtain brewing adjuncts from corn and sorghum starch. For corn starch extrusion, a Box-Behnken design was devised in which moisture, screw speed, temperature of the barrel, and concentrations of sodium stearoyl lactylate (SSL) were varied, and sorghum starch was extruded according to a 23 model in which the modified variables were moisture, SSL concentration, and temperature. The aim was to maximize starch damage and minimize resistant starch and final viscosity as determined with a Rapid Visco Analyzer. The treatments that satisfied these requirements were mashed, and wort extract yield was determined. Glucose, maltose, and maltotriose concentrations in the resulting worts were determined by HPLC with a refractive index detector. Feedstock tempering and SSL content were the most important factors affecting the response; for corn starch, treatments with lower moisture (20%) and middle levels of SSL (0.5%) or with high levels of both moisture (40%) and SSL (1%) produced the most desirable samples for mashing, whereas for sorghum starch the best treatment was tempering to 20% moisture and containing middle levels of SSL (0.5%). No statistical differences were found between these experimental treatments and the control.
Extruded products were prepared from a corn flour and dehulled carioca bean (Phaseolus vulgaris, L.) flour blend using a single-screw extruder. A central composite rotate design was used to evaluate the effects of extrusion process variables: screw speed (318.9–392.9 rpm), feed moisture (10.9–21.0 g/100 g) and bean flour level (4.8–55.2 g/100 g) on the specific mechanical energy (SME), sectional expansion index (SEI), longitudinal expansion index (LEI), volumetric expansion index (VEI) and density (D) of the extrudates. The instrumental texture was also analyzed. The independent variables had significant effects on the physical properties (SEI, VEI and density) of extrudates, with the exception of SME and LEI. SEI increased with increasing screw speed, but a higher moisture and bean flour content resulted in decreasing SEI and VEI. The increase of moisture and bean flour increased the density of extrudates. According to texture analysis, some treatments with 30 and 45 g/100 g bean flour did not show significant differences when compared to commercial brand snacks. However, when combined with higher moisture content (≥19 g/100 g) and lower screw speed (≤333 rpm), the results of the expanded product were not satisfactory.
The production of palatable meat analogues using high moisture extrusion cooking is a complex process that depends on both the properties of the protein ingredients and the extrusion conditions. Three commercial pea protein isolates were compared in order to investigate which protein properties affect extruder responses and product texture properties. The comparison revealed that although their basic chemical compositions were similar their functional properties affected the viscosity of the protein mass during the initial heating phase of the extrusion process. The product texture properties depended on the cooking temperature and were basically similar among the proteins, although considerably different energy input was observed during texturization. Our findings show that pea protein isolates are valuable raw materials for the development of fibrous whole-muscle meat alternatives, opening up a wide range of products for different consumer requirements.
The present study examines the addition of dehydrated broccoli or olive paste to corn flour for the production of extrudates with increased value and superior quality. Extrudates were prepared using a twin-screw extruder, operated at different conditions, including screw speed (150 rpm, 200 rpm, 250 rpm) and extrusion temperature (140 °C, 160 °C, 180 °C). The moisture content of the raw mixture was regulated in three levels (14%, 16.5%, 19%), whereas the concentration of the added ingredient was adjusted to 4%, 7% and 10% for broccoli and to 4%, 6% and 8% for olive paste. Structural properties and rehydration were investigated with regard to process conditions and material characteristics. Mathematical models were also used to correlate structural properties with process parameters. Regression analysis showed that the increment of moisture content and broccoli or olive paste concentration, as well as the decrement of temperature and screw speed resulted in denser extrudates with lower porosity. Products with 14% moisture content and 4% material concentration that were extruded at the highest screw speeds (250 rpm) presented the highest degree of expansion. These conclusions were strengthened with the results obtained from mercury porosimetry and scanning electron microscopy. In addition, moisture diffusion coefficient was calculated from the rehydration kinetics and was correlated with process parameters. Diffusion coefficient decreased with moisture content and material concentration, while it increased with temperature and screw speed, indicating positive relationship with extrudates' porosity.
Green banana flour was extruded through a co-rotating twin-screw extruder with constant barrel temperature. The objectives of this study were to determine the effect of extrusion cooking variables (feed moisture, FM, 20% and 50%; screw speed, SS, 200 and 400rpm) and storing of the extruded flours at 4°C for 24h on the physicochemical properties, resistant starch (RS), pasting properties and antioxidant capacities. Extrusion cooking at higher FM and lower SS increased the amylose content, which was expressed in highest RS content. Water adsorption index (WAI) and pasting properties were increased, while water solubility index (WSI), total phenolic content (TPC) and antioxidant activities (FRAP, ABTS(+), DPPH) in free and bound phenolics were decreased compared to the other extruded samples. Storing the extruded flours at 4°C for 24h prior to oven drying was the main factor leading to a further increase in the content of amylose, RS, TPC and WSI values, as well as pasting properties - in particular peak viscosity. Compared to native banana flour, extrusion cooking caused significant changes in all studied properties of the extruded flours, except for soluble DF and antioxidant capacity (ABTS(+) and DPPH) of bound phenolics.
Extrusion cooking of cereals is a complex process, regarding a wide range of food products (snack-foods, baby-foods, cereals for breakfast and pasta). In this work, an analysis of variance (ANOVA) on the extrusion cooking process for cereals in a co-rotating twin-screw extruder was carried out, using a finite-element fluid dynamic simulation model, to study shear rate, residence time and mixing index inside the extruder, varying temperature, screw rotation velocity, flow rate and extruder geometry.Besides, the significance analysis, carried out in this study, have shown several aspects of the process under investigation: (i) the interdependence between shear rate, screw rotation velocity and screw axis ratio seems very strong; (ii) the significance of the effects on shear rate of the variations of temperature and flow rate appears less meaningful; (iii) the influence on the residence time of the flow rate and screw axis ratio is more meaningful respect to the screw speed and temperature.The numerical simulations have revealed numerous aspects that can be used to improve the extrusion process: the flow temperature can be varied without modifying the gelatinization of material that is mainly influenced by screw rotation velocity and screw axis ratio.
The effect of different levels of feed moisture (12–17%) during extrusion cooking, using a co-rotating twin-screw extruder on selected nutritional and physical properties of extruded products was investigated. Four different formulations were used based on wheat flour and corn starch with the addition of 10% brewer’s spent grain (BSG) and red cabbage (RC) trimming reducing the flour and starch. The samples were: wheat flour+BSG (WBSG), corn starch+BSG (CBSG), wheat flour+red cabbage (WRC) and corn starch+red cabbage (CRC). Process conditions utilised were: constant feed rate of 25kg/h, screw speed 200rpm and barrel temperature of 80 and 120°C. The results indicated that increasing the water feed to 15% increased the level of total dietary fibre (TDF) in all the extrudates while extrusion processing increased the level of TDF in WBSG, CBSG and CRC but decreased in WRC products. Extrusion cooking increased the level of total antioxidant capacity (TAC) and total phenolic compounds (TPC) in WRC and CRC. In addition to water feed level affecting the TDF of the extrudates, also affected were the expansion ratio, bulk density, hardness, WSI, SME and colour. The protein level of the products and hardness of extrudates were related to the different formulations.
The formation of starch-lipid complexes during extrusion of model system (rice starch added with oleic acid) and real food (rice starch added with pistachio nut flour) was evaluated. Both formulas were extruded at the same processing conditions (temperature profiles, screw speed and water feed content).The formation of starch-lipid complexes in real food, is strongly dependent on water feed content. In fact, at barrel temperature of 128°C, the highest melting enthalpy of real food (6.7J/g) was obtained only at 21% of water feed content whereas in the model system it was obtained both at 16 and 21%.These results point out the importance to consider all components present in the extruded food in order to study biopolymers modifications that occur during processing.
Effects of nonwaxy (21% amylose, 79% amylopectin) and waxy (100% amylopectin) rice starch-lipid complexes on the rate of in vitro digestibility were determined. Long-chain (greater than or equal to C:18) saturated emulsifiers reduced digestibility more than short-chain (<C:18) saturated and unsaturated emulsifiers when complexed with nonwaxy and waxy rice starch. The largest decrease in digestibility (33%) was achieved with Polyaldo 10-1-2 (100% C18:0 with decaglyceryl monostearate modification) for nonwaxy rice. Waxy rice starch did not complex with most of the emulsifiers, in contrast to nonwaxy rice starch. Most of the emulsifiers that reduced digestibility by 10% or less were composed of unsaturated monoglycerides, including some acetylated and succinylated monoglycerides. The fluid behavior of nonwaxy rice starch-emulsifier solutions was more pseudoplastic than waxy rice starch-emulsifier solutions. The consistency index varied with emulsifiers. The nonwaxy rice starch-emulsifier solutions and some of those prepared using waxy rice starch would Se suitable for semisolid food applications. The waxy rice starch-emulsifier solutions with low consistency (0.4-0.7) and high-flow behavior (0.7-0.8) indices would be suitable for beverage applications.
A large variety of cooked corn products can be prepared on rolls, in extruders or by steamcooking. Slight changes in operating conditions of the cooking equipment can bring about significant changes in absorption, solubility and viscosity properties of the cooked products. Production of processed materials with high water absorption and retaining high cooked paste viscosity appears more difficult by direct steaming than by use of the other methods.Roll-cooking should be better than extrusion-cooking for preparing materials of maximum water absorption and minimum water solubility. Such materials are well suited either for thick gruels or for industrial thickening or gelling agents. Extrusion-cooking should be better for preparing materials of minimum water absorption and maximum water solubility. Such materials are well suited either for beverages or for industrial uses where adhesive properties are desired. Steamcooking should be suitable for preconditioning before roll- or extrusion-cooking, but it appears that heating time must be held to a minimum.
Decorticated meals made from grain sorghum and cowpeas and 33-67% blends of the two were hydrated to 20.5, 23.0, and 25% moisture and extruded at 175°, 190°, and 205°C. Effects of composition, feed moisture, and barrel temperature on product temperature, residence time, expansion ratio, unit bulk density, product moisture, Warner-Bratzler shear force, stress and energy and sensory hardness and brittleness were determined. Most properties could be described by a generalized second order model. Individual models differed widely; however, composition (or its interaction terms) was significant in most cases in which it was a variable. Considering all compositions, temperature was most often significant. Effect of moisture was more significant as the proportion of cowpea in the mixtures increased. Textural properties were compared to those of three commercial snack foods. Experimental extrudates were somewhat tougher than commercial snacks although not drastically different from them.
Blends of barley flour and tomato pomace were processed in a co-rotating twin-screw extruder. Experimental design with die temperature (140–160 °C), screw speed (150–200 rpm) and tomato pomace level (2–10%) as independent variables produced 20 different combinations that were studied using response surface methodology to investigate the effect of these variables on system parameters (SME, die melt temperature and die pressure) and product responses (expansion, bulk density, water absorption and solubility indices, texture and color). Extrudate from five experiments within 20 samples was selected for sensory evaluation in terms of color, texture, taste, off-odor and overall acceptability. Regression equations describing the effect of each variable on the system parameters and product responses were obtained. The system parameters and product responses were most affected by changes in temperature, pomace level and to a lesser extent by screw speed. Extrudates with 2% and 10% tomato pomace levels extruded at 160 °C and 200 rpm had higher preference levels for parameters of color, texture, taste and overall acceptability. The results suggest that tomato pomace can be extruded with barley flour into an acceptable and nutritional snack.
Soy protein supplementation increases the nutritional value of starch-based expanded snacks. A systematic study was conducted to serve as baseline for optimizing the addition of soy protein concentrate (SPC). Physical and microstructural properties of native corn starch–soy protein concentrate (CS–SPC) extrudates were investigated in relation to the macromolecular changes in starch during extrusion. The effects of extruder screw speed (230 and 330 rpm) and SPC concentration (0%, 5%, 10%, 15%, 20%) on the abovementioned parameters were determined. Increasing screw speed resulted in higher specific mechanical energy (SME) and expansion, and lower mechanical strength. On the other hand, addition of 5–20% SPC led to lower SME and expansion, and higher mechanical strength. X-ray micrographs showed smaller yet more cells, and cell wall thickening with SPC addition. Water absorption index increased and water solubility index decreased with increase in screw speed and SPC level. Increasing screw speed resulted in a slight shift towards smaller molecular weight fractions of starch, as determined by gel permeation chromatography.
Extrusion cooking, as a multi-step, multi-functional and thermal/mechanical process, has permitted a large number of food applications. Effects of extrusion cooking on nutritional quality are ambiguous. Beneficial effects include destruction of antinutritional factors, gelatinisation of starch, increased soluble dietary fibre and reduction of lipid oxidation. On the other hand, Maillard reactions between protein and sugars reduce the nutritional value of the protein, depending on the raw material types, their composition and process conditions. Heat-labile vitamins may be lost to varying extents. Changes in proteins and amino acid profile, carbohydrates, dietary fibre, vitamins, mineral content and some non-nutrient healthful components of food may be either beneficial or deleterious. The present paper reviews the mechanisms underlying these changes, as well as the influence of process variables and feed characteristics. Mild extrusion conditions (high moisture content, low residence time, low temperature) improve the nutritional quality, while high extrusion temperatures (200 °C), low moisture contents (<15%) and/or improper formulation (e.g. presence of high-reactive sugars) can impair nutritional quality adversely. To obtain a nutritionally balanced extruded product, careful control of process parameters is essential.
Normal corn starch was extruded with palm, peanut and coconut oils; myristic, stearic and behenic acids and three monoglycerides in a C. W. Brabender single screw laboratory extruder at 140°C barrel temperature, 140rpm screw speed and 22% moisture content. Microstructure of extrudates was studied using a scanning electron mircocope. The pore size distribution, pore volumes and shear strengths of the extrudates were also studied. Addition of lipids resulted in modification of pore size distribution and pore volumes depending on the type of lipid. Complexing lipids gave lower pore volumes, smaller size pores, lower porosities and higher shear strengths of the extrudates. Porosity correlated well with the shear strength values.
Modifizierung der Mikrostruktur von mit ausgewählten Lipiden extrudierter Stärke.
Normale Maisstärke wurde zusammen mit Palm-, Erdnuß- und Kokosnußölen; Myristin-, Stearin- und Behensäuren und drei Monoglyceriden in einem C. W. Brabender Einwellen-Laboratoriums-Extruder bei 140°C Trommeltemperatur extrudiert sowie 140rpm Schneckengeschwindigkeit und 22% Feuchtigkeitsgehalt. Die Mikrostruktur der Extrudate wurde mittels eines Raster-Elektronenmikroskopes untersucht. Der Zusatz von Lipiden ergab eine Modifizierung der Porengrößen-Verteilung und der Porenvolumina, je nach Lipidtyp. Komplexierende Lipide ergaben größere Porenvolumina, kleine Poren und höhere Scherfestigkeiten der Extrudate. Die Porosität stimmte gut mit den Scherfestigkeitswerten überein.
Greater consumer demand for nutritious extruded food products with enhanced bioactive compounds has shifted research focus towards incorporation of bioactive rich ingredients with traditionally extruded starch materials. Recent research has highlighted the importance of bioactive compounds in human health and nutrition. An evaluation of the available literature reveals that the level of bioactive compounds in extruded products is influenced by extrusion process variables. Shear, temperature, resonance time and water content are all factors which contribute to the overall composition of extruded products. In addition, food structure may also exhibit a role in the potential release of functional bioactives. This paper reviews the effect of extrusion on bioactive compounds such as phenolic compounds, anthocyanins, isoflavones and their antioxidant activity. Factors influencing levels and stability during extrusion are also discussed.
The effects of several factors, like screw rpm, die restriction (l/r) and moisture, together with corn endosperm hardness and rice amylose content, on melt viscosity, were analyzed using a Brabender single screw extruder. Bagley’s method was utilized to estimate melt viscosity at the die and to obtain rheological models. Relationships among different responses such as mass output, die pressure, specific mechanical energy consumption, melt viscosity and degree of cooking were discussed. All responses analyzed were found to be dependent on both extrusion conditions and material structural characteristics. Very low values of the exponent of the viscosity power law model “n” were found, particularly at low moisture. This fact is explained on the basis that to get different value pairs of mass output and pressure, rpm has to be changed and, as rpm increases, structural damage (degree of cooking) also increases, which in turn produces a reduction in pressure. It was concluded that “Bagley’s method” should not be used to estimate melt viscosity in cases where pressure and mass output pairs of data obtained do not correspond to samples differing excessively in degree of cooking.
Response surface methodology (RSM) was used to study the effects of feed moisture content (16–18%), screw speed (250–320 rpm), and barrel temperature (150–170 °C) on extruder system parameters (product temperature, die pressure, motor torque, specific mechanical energy, SME) and physical properties (expansion, bulk density, hardness) of a chickpea flour-based snack. Second-order polynomials were used to model the extruder responses and product properties as a function of process variables. Product temperature and die pressure were affected by all three process variables, while motor torque and SME were only influenced by screw speed and barrel temperature. All three variables affected product responses significantly. Desirable products, characterized by high expansion ratio and low bulk density and hardness, were obtained at low feed moisture, high screw speed and medium to high barrel temperature. It was demonstrated that chickpeas can be used to produce nutritious snacks with desirable expansion and texture properties.
Structural properties, such as apparent density, true density, expansion ratio and porosity, of extruded corn grits were measured. Corn grits were extrusion-cooked in a Prism extruder with varied feed rate (1.16–6.44 kg/h), screw speed (150–250 rpm), product temperature (100–260 °C) and feed moisture content (12–25 kg/100 kg wet basis). A simple mathematical model was used to correlate the examined properties with the extrusion conditions. Extruded product apparent density, porosity and expansion ratio were found to be dependent on feed moisture content, residence time and temperature while they were not affected by screw speed. More specifically, the apparent density of extruded products had an increasing trend with feed moisture content and residence time, while it decreased with product temperature. Porosity and expansion ratio of extruded products decreased significantly with feed moisture content and residence time, while temperature rise resulted in products of higher porosity and expansion ratio.
Heated extrusion was tested as an alternative process for incorporating “hard-to-cook” beans into food products. A 32 factorial design was used to evaluate extrusion conditions for a 40/60 (w/w) blend of “hard-to-cook” beans and quality protein maize. Tested extrusion variables were temperature (155, 170 and 185 °C) and moisture content (15.5, 17.5 and 19.5 g/100 g). Screw speed was fixed at 130 rpm. The extrudates obtained at 155 and 170 °C with 15.5% moisture had the best physical characteristics and were chosen for comparative analysis of nutritional changes between the unprocessed “hard-to-cook” bean/quality protein maize flour blend and the resulting extrudates. In vitro protein digestibility was higher in the extrudates (80%) than in the flour blend (76%). In vitro starch digestibility was higher at 155 °C (89%) and 170 °C (92%) than in the flour blend (12%). Processing conditions decreased dietary fibre content by 38% at 155 °C and 44% at 170 °C.
Physicochemical, functional, thermal and pasting properties of flours from field pea (LFP-48 and PG-3) and pigeon pea (AL-15 and AL-201) cultivars were determined and related to each other using Pearson correlation and principal component analysis (PCA). Field pea flours (FPF) were significantly (P < 0.05) different from pigeon pea flours (PPF) in their lower ash and higher fat and protein contents. FPF also exhibited higher L∗, ΔE value, water solubility index (WSI), oil absorption capacity (OAC), foaming capacity (FC) and lower a∗, b∗ value, water absorption index (WAI) and water absorption capacity (WAC) in comparison to PPF. FPF differed significantly from PPF in exhibiting lower transition temperatures (To, Tp, Tc), enthalpy of gelatinization (ΔHgel), peak height index (PHI) and higher gelatinization temperature range (R). PCA showed that LFP-48 and PG-3 flours were located at the far left of the score plot with a large negative score, while the AL-15 and AL-201 flours had large positive scores in the first principal component. Several significant correlations between functional, thermal and pasting properties were revealed, both by Pearson correlation and PCA. Pasting properties of the flours, measured using the rapid visco analyzer (RVA), also differed significantly. PPF were observed to have higher pasting temperature (PT), peak viscosity (PV), trough viscosity (TV), breakdown (BV), final viscosity (FV) and lower setback viscosity (SV) as compared to FPF.
Response surface methodology was used to investigate the effects of extrusion conditions including moisture content (12–18%), temperature (150–175 °C), screw speed (200–280 rpm), and change in feed composition, durum clear flour (8–20%), partially defatted hazelnut flour (PDHF) (5–15%) and fruit waste (3–7%) contents on the physical and functional characteristics of the extruded snack food based on rice grit in combination with fruit waste, durum clear flour and PDHF. Response variables are bulk density, porosity, water absorption and water solubility indices and sensory properties of the extruded snacks. The product responses were most affected by changes in PDHF content and to a lesser extent by fruit waste content. Increasing PDHF content caused increase in bulk density and water solubility index, but decrease in porosity and water absorption index of the extruded snacks. Changing process conditions affected the physical and functional properties of produced snacks. The sensory evaluation of extrudates suggests that extrusion of PDHF, fruit waste and durum clear flour in combination with rice grit can produce acceptable extruded snack.
The barley flour–grape pomace blends were extruded in a 30 mm APV co-rotating twin-screw extruder. Response surface methodology using a central composite design was used to evaluate the effects of independent variables, namely die temperature (140–160 °C), screw speed (150–200 rpm) and pomace level (2–10%, db) on product responses (expansion, bulk density, texture and color). Sensory analysis was carried out for selected extrudates for appearance (color, porosity), taste (bran flavor, bitterness and sweetness), off-odor, texture (hardness, crispness and brittleness) and overall acceptability. Multiple regression equations were obtained to describe the effects of each variable on product responses. The product responses were most affected by changes in temperature, pomace level and to a lesser extent by screw speed. Blends of 2% grape pomace extruded at 160 °C, 200 rpm and 10% grape pomace extruded at 160 °C, 150 rpm had higher preference levels for parameters of appearance, taste, texture and overall acceptability. However, graphical optimization studies resulted in 155–160 °C, 4.47–6.57% pomace level and 150–187 rpm screw speed as optimum variables to produce acceptable extrudates. The results suggest that grape pomace can be extruded with barley flour into an acceptable snack food.
The effects of dietary fiber on small intestinal mucosal mass, morphology, and cytokinetics were studied by feeding three qualitatively different forms of fiber to 40 rats for 4 wk. A fiber-free diet was fed to the control group and a similar diet with either a 20% oat bran, 10% pectin, or 10% guar supplement to the other three groups. All groups of rats exhibited similar caloric intakes and weight gains. Only the guar diet produced a significant increase in mucosal mass, as demonstrated by 19.1% increase in mucosal weight (p less than 0.05), a 16.7% increase in RNA (p less than 0.05) and an increase in DNA from 38.3 +/- 1.8 (SEM) to 44.6 +/- 2.3 micrograms/cm intestine/100 g body weight (p less than 0.05) when compared to the controls. The pectin-diet produced a decrease in villus height from 102.1 +/- 2.4 to 94.3 +/- 2.4 cells but an increase in crypt column length from 25.3 +/- 0.6 to 27.4 +/- 0.4 cells when compared to the controls (p less than 0.05). The shift in labeling index distribution curves for pectin and guar to the right and for oat bran to the left indicated an increase and decrease respectively in labeling index. The higher rate of epithelial cell migration in the pectin- and guar-fed groups shortened their estimated villus cell transit times to 36.4 +/- 0.7 and 37.0 +/- 1.4 h, respectively, when compared with 42.6 +/- 1.2 h in the oat bran and 41.1 +/- 1.0 h in the control (p less than 0.05). These results show that the modulation of small intestinal mucosal structure and growth by dietary fiber appears to be mediated through alterations in cell proliferation and that these changes depend not only on the quantity but also the quality of the fiber present in the diet.
Full-text of this article is not available in this e-prints service. This article was originally published [following peer-review] in Journal of Food Engineering, published by and copyright Elsevier. The effect of extrusion conditions, including feed rate (20–32 kg h−1), feed moisture content (14–22%), screw speed (180–320 rpm), and barrel temperature (100–140 °C) on the functional properties (density, expansion, water absorption index (WAI), and water solubility index (WSI)) and physical properties (density, expansion and textural characteristics) of an expanded wheat snack was investigated. Increasing feed rate results in extrudates with a higher hardness and lower energy to puncture the samples. Increasing feed moisture content results in extrudates with a higher density, lower expansion, lower WAI, higher WSI, higher hardness and lower puncture energy. Increasing screw speed caused slight reduction of density and hardness of wheat extrudate. Higher barrel temperature reduced density, WAI, and hardness, but increased the WSI and puncture energy of extrudate.
The potential of purple corn color (PCC), a natural anthocyanin, to modify colorectal carcinogenesis was investigated in male F344/DuCrj rats, initially treated with 1,2-dimethylhydrazine (DMH), receiving 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in the diet. After DMH initiation, PCC was given at a dietary level of 5.0% in combination with 0.02% PhIP until week 36. No PCC-treatment-related changes in clinical signs, body weight and food consumption were found. Incidences and multiplicities of colorectal adenomas and carcinomas in rats initiated with DMH were clearly increased by PhIP. In contrast, lesion development was suppressed by PCC administration. Furthermore, in the non-DMH initiation groups, induction of aberrant crypt foci by PhIP tended to be decreased by the PCC supplementation. The results thus demonstrate that while PhIP clearly exerts promoting effects on DMH-induced colorectal carcinogenesis, these can be reduced by 5.0% PCC in the diet, under the present experimental conditions.
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