Stability of zearalenone during extrusion of corn grits

The effects of extrusion cooking on the stability of zearalenone (ZEN) in spiked (4.4 microg/g) food-grade corn grits were investigated using a twin screw extruder. A ground rice culture material containing a high level of ZEN was used to spike the corn grits. The extrusion variables were screw type (mixing and nonmixing), temperature (120, 140, and 160 degrees C), and moisture content (18, 22, and 26%). Both unextruded and extruded samples were analyzed for ZEN by high-performance liquid chromatography. Extrusion cooking of the corn grits resulted in significant reductions of ZEN in grits extruded with either mixing screws or nonmixing screws, but use of mixing screws was somewhat more effective (66 to 83%) overall than nonmixing screws (65 to 77%). Greater reduction of ZEN was observed at either 120 or 140 degrees C than at 160 degrees C. The moisture content of corn grits was not a significant factor affecting reduction of ZEN during extrusion with either mixing or nonmixing screws.     

System parameters and product properties response of soybean protein extruded at wide moisture range

In order to explore the effect of water during extrusion process, soybean protein isolate (SPI) was extruded using a pilot-scale twin-screw extruder at 28%, 36%, 44%, 52% and 60% moisture content and 140, 150 and 160 °C cooking temperature. The extrusion system parameters like in-line viscosity at die, mean residence time and specific mechanical energy (SME), product textural properties including tensile strength, hardness, chewiness and degree of texturization, and the molecular weight distribution characterized by SDS–PAGE were investigated. And the interrelationship between system parameters and product properties were analyzed. The results showed that moisture content was a more important factor on system parameters and product properties than cooking temperature. Higher moisture content resulted in lower viscosity of dough in the extruder, shorter residence time and lower conversion ratio of extruder mechanical energy into heat energy, finally reducing significantly the tensile strength, hardness, chewiness and the degree of aggregation. The data from extrusion system parameters and product properties correlate well and could be used to explain and control the characteristics of extrudate.     

Dietary fiber profile of barley flour as affected by extrusion cooking

Barley grains, Phoenix and CDC-Candle, were extruded in a twin-screw extruder at 90−140 °C and 20–50% moisture level. Effects of extrusion conditions on total (TDF), soluble (SDF), and insoluble dietary fiber (IDF) were determined. The content of SDF and TDF increased upon extrusion cooking of both types of barley flours. The changes in IDF content were found to be variety-dependent. Only a minor decrease in IDF content of CDC-Candle barley was found, but an increase in IDF content of Phoenix was observed at all extrusion temperatures. The increase in SDF, in both barleys, could be due to the transformation of some IDF into SDF during extrusion and the formation of additional SDF by transglycosidation. The increase in IDF in Phoenix flour could be due to the formation of retrograded amylose [resistant starch (RS3)] during extrusion cooking and subsequent cooling.     

Extrusion of Hulled Barley Affecting β-Glucan and Properties of Extrudates

Grits from eight different hulled barley cultivars were subjected to extrusion cooking on a twin screw extruder, and the effect of extrusion variables (temperature and moisture) on β-glucan and physicochemical properties was evaluated. The highest bulk density was observed for extrudates extruded at 150 °C and 20% moisture (low temperature high moisture, LTHM) while the highest expansion was observed for the extrudates extruded at 150 °C and 15% moisture (low temperature low moisture). Extrusion reduced the lightness (L*) of the extrudates and the highest decrease observed for LTHM extrudates. Increasing the feed moisture decreased water solubility index (WSI) significantly while increasing the extrusion temperature significantly increased WSI. The high temperature high moisture (HTHM) extrudates exhibited the highest water absorption capacity. The total β-glucan content was not affected by extrusion cooking, but a significant increase in soluble β-glucan was observed with the highest in high temperature low moisture extrudates. The ratio of soluble to insoluble β-glucan varied from 0.7 to 1.5 in the control barley, but after extrusion cooking, the ratio was changed from 1.2 to 3.1. The β-glucan extractability increased by up to 8% after extrusion with extrudates from HTHM showing the highest extractability. The extent of starch gelatinization varied from 80% to 100% upon extrusion, and the highest was observed in HTHM extrudates. A significant decrease in the peak and final viscosity of the extrudates at all the extrusion conditions was observed.     

Reduction of Aflatoxins by Extrusion-Cooking of Rice Meal

ABSTRACT: The objective of this work was to determine the reduction of aflatoxin B₁ (AFB₁), B₂ (AFB₂), G₁ (AFG₁), and G₂ (AFG₂) as a function of initial moisture content of samples (24%, 27%, and 30%), barrel temperature (140, 170, and 200 °C), and residence time (30 to 70 s) when artificially contaminated rice meal was extrusion‐cooked. Extruded and unextruded samples were analyzed by high‐performance liquid chromatography (HPLC). Extrusion‐cooking was observed to reduce aflatoxin (AF) content, which ranged from 51% to 95% depending on the type of AF and the studied variables. Only in the case of AFG₂ was it found that the higher the temperature, the higher the moisture content, and the longer the residence time, the greater the reduction. Moisture content had a significant influence on reducing AFB₂, AFG₁, and AFG₂ whereas it was not a significant factor affecting the levels of AFB₁. Regardless of the type of AF, the lowest reductions were achieved at a temperature of 140 °C. Even though theoretically greater losses would be expected at highest temperature, AFB₁ and AFB₂ were more reduced by 170 °C than by 200 °C while AFG₁ reductions were not statistically different when processing at 170 °C and 200 °C. The decrease of AF followed 1st‐order kinetics; the fastest treatment in reducing AF was that at 200 °C when samples containing AFG₂ were wetted to 24% and when samples containing AFB₁, AFB₂, and AFG₁ were hydrated to 27%. By contrast, the slowest treatments were observed at a barrel temperature of 140 °C.     

Uniaxial Extensional Viscosity During Extrusion Cooking from Entrance Pressure Drop Method

Uniaxial extensional viscosity of corn meal at moisture contents of 30 and 35% (dry weight basis) and temerature of 160 and 180°C was estimated from entrance pressure'drop measurements during extrusion cooking. The value of the shear component of the entrance pressure drop was an order of magnitude below that of the extensional component. Food doughs exhibited shear thinning and extension thinning behavior during processing conditions used. Increasing moisture and temperature decreased extensional viscosity at higher extension rates. The Trouton ratio ranged from 25 to 50 and was affected by product moisture content, barrel temperature, and deformation rate.     

Extrusion Process Parameters, Sensory Characteristics, and Structural Properties of a High Moisture Soy Protein Meat Analog

ABSTRACT: Soy protein isolate and wheat starch at 9:1 ratio were extruded at 60%, 65%, and 70% moisture contents and 138, 149 and 160 °C cooking temperatures. The results indicated that moisture content was a more important factor than cooking temperature for both extrusion process parameters and product sensory characteristics. Extrusion at a lower moisture content resulted in a higher product temperature and higher die pressure. The resultant products were tougher, chewier, and more cohesive and had a more layered and fibrous structure. Water absorption capacity increased with both higher extrusion moisture and higher cooking temperature.     

Effects of extrusion variables on the properties of waxy hulless barley extrudates

The objective of this research was to investigate the extrudability of waxy hulless barley flour under various extrusion conditions. Waxy hulless barley flour was processed in a laboratory-scale corotating twin-screw extruder with different levels of feed moisture content (22.3, 26.8, and 30.7%) and die temperature (130, 150, and 170 degrees C) to develop a snack food with high beta-glucan content. The effects of extrusion condition variables (screw configuration, moisture, and temperature) on the system variables (pressure and specific mechanical energy), the extrudate physical properties (sectional expansion index, bulk density), starch gelatinization, pasting properties (cold peak viscosity, trough viscosity, and final viscosity), and beta-glucan contents were determined. Results were evaluated by using response surface methodology. Increased extrusion temperature and feed moisture content resulted in decreases in exit die pressure and specific mechanical energy values. For extrudates extruded under low shear screw configuration (LS), increased barrel temperature decreased sectional expansion index (SEI) values at both low and high moisture contents. The feed moisture seems to have an inverse relationship with SEI over the range studied. Bulk density was higher at higher moisture contents, for both low and high barrel temperatures, for samples extruded under high shear screw configuration (HS) and LS. Cold peak viscosities (CV) were observed in all samples. The CV increased with the increase in extrusion temperature and feed moisture content. Although beta-glucan contents of the LS extrudates were comparable to that of barley flour sample, HS samples had generally lower beta-glucan contents. The extrusion cooking technique seems to be promising for the production of snack foods with high beta-glucan content, especially using LS conditions.     

Antioxidant activity of barley as affected by extrusion cooking

Grit from different hulled barley cultivars was subjected to extrusion cooking and the effect of extrusion moisture and temperature on the antioxidant properties was studied. A significant decrease in the total phenolic content (TPC) and total flavonoid content (TFC) was observed upon extrusion and a further decrease of 8-29% in TPC and 13-27% in TFC was observed when both the feed moisture and extrusion temperature were increased. The antioxidant activity (AOA) increased significantly upon extrusion and this increase was the highest (36-69%) at 150 °C and 20% feed moisture. The increase in feed moisture and temperature significantly increased the metal chelating activity. The reducing power decreased significantly upon extrusion as compared to their corresponding control samples. Extrusion lead to a greater increase in non-enzymatic browning (NEB) index however, increasing the moisture content of feed decreased the NEB index by 3-29% (at 180 °C) and 1-17% (150 °C), while increasing the temperature increased the NEB significantly.     

Characterization of water state and distribution in textured soybean protein using DSC and NMR

To explore the role of water during extrusion cooking and the scientific basis for demarcating low-intermediate moisture and high-moisture extrusion technique, soybean protein isolate (SPI) was processed using a pilot-scale twin-screw extruder under 28–60% moisture content and 140–160 °C cooking temperature. The state of water in textured soybean protein (TSP) with different treatments were analyzed by using differential scanning calorimetry (DSC) and low field nuclear magnetic resonance (LF-NMR) together. The distribution of water in TSP was characterized by using magnetic resonance imaging (MRI). The results showed that there were at least two categories of water with different states or mobility in TSP, and the results of water state and critical water content in TSP measured by DSC and NMR were consistent. The distribution of water in TSP was homogeneous, and the intensity of distribution increased markedly with total water content increasing.     

Bacterial spore injury during extrusion cooking of corn/soybean mixtures

This study examined the potential for injury of Bacillus globigii (Bacillus subtilis var. niger, strain ATCC9372) spores during extrusion cooking of a corn/soybean (70/30%, w/v) mixture. The barrel temperature in zone 1 was kept constant at 80 degrees C while it was varied from 100 to 120 and 140 degrees C in zone 2. Recovery and enumeration of spores surviving the extrusion cooking process were conducted with five culture media ranging from minimal to rich in nutrient composition. Numbers of spores counted with a minimal culture medium after extrusion at the low temperature were lower compared to recovery with more complete media. All culture media, including minimal and richer, were equally effective in recovering untreated spores. At the higher extrusion temperatures all media were equally effective in recovering the small numbers of viable spores. The results indicated that the spores of the organism may be injured at lower extrusion temperatures.     

Physico‐chemical and antioxidant properties of extrudates developed from honey and barley

Barley flour and honey, being concentrated source of nutrients, were used to develop extruded product using twin‐screw extruder. Response surface methodology was applied to study the effects of honey (5–25%), moisture content (17–21%) temperature (120–160 °C) and screw speed (180–220 rpm) on product responses. The variation in moisture content and die temperature affected the physicochemical properties of extrudate but screw speed had significant effect only on hardness. It was established that with increase in honey levels from 5% to 20%, there was increase in antioxidant activity (up to 106.9%), total phenolic content (up to 90.2%) and total flavonoid content (up to 89.2%) in interaction with other extrusion cooking variables. The optimal condition corresponds to honey content of 18.86%, feed moisture of 18%, die temperature of 148.62 °C and screw speed of 209.99 rpm. The results suggest that honey can be extruded with barley flour into a healthful snack food.     

Ochratoxin A reduction in meat sausages using processing methods practiced in households

The aim of this study was to investigate the possibilities of ochratoxin A (OTA) reduction in home-made meat products. Meat sausages (n = 50) produced from raw materials coming from pigs exposed to OTA-contaminated feed, were subject to common heat processes practiced in households (cooking, frying and baking). Concentrations of OTA in pre- and post-processed products were quantified using a validated immunoassay method, enzyme-linked immunosorbent assay, and confirmed using a high-performance liquid chromatography with fluorescence detection. In line with the differences in recipes used and the degree of OTA accumulation in raw materials, OTA concentrations established in Mediterranean and roast sausages were lower than those found in liver and blood sausages. Baking of contaminated sausages at the temperatures of 190–220°C (for 60 min) resulted in significant reduction of OTA levels (75.8%), while 30-min cooking (at 100°C) and frying (at 170°C) proved to be significantly less effective (e.g. yielding OTA reductions of 7.4% and 12.6%, respectively). The results pointed out that despite high OTA stability, heat processes are capable of reducing its concentration in home-made meat products, depending on the processing modality used.     

Diet and Health: Apple Polyphenols as Antioxidants

Abstract

Although primarily used at low moisture levels, extrusion cooking with twin‐screw extruders also applies to food mixes with 40–80% moisture. Such levels reduce or prevent viscous dissipation of energy and product expansion, but facilitate operations such as fat emulsification, sterilization, protein gelation, restructuring and shaping of comminuted meat or fish, and microcoagulation and/or fibrillation of specific protein constituents. Fibrous gelled structures are obtained from (a) defatted soy flours or concentrates; (b) wheat gluten; and (c) mixes containing 70–80% surimi plus 30–20% soy concentrate or gluten, by extrusion cooking at 50–70% moisture, at barrel temperatures above 140°C, using long cooling dies. The continuous gelled bands are highly resistant to stretching in the longitudinal direction. They display a multilayer and partly fibrous structure. An extruded crab analog with a finely fibrous texture, made from Alaska pollack surimi plus egg white and 1% starch, is already commercialized in Japan. Three main phenomena are involved in the formation of these structures: (a) protein plastification (“melting”) within the extruder, which requires a barrel temperature of 140–180°C (at 60–70% water), a residence time close to 150 s, and high shear forces; (b) stability of extrusion conditions, without surging (often difficult to achieve); (c) presence of a long cooling die, exerting essential functions: upstream pressure generation, enabling high temperature, channel filling, and extrudate continuity; progressive reduction of the mechanical and thermal energy of the food mix, permitting proper shaping, while avoiding product expansion; alignment of dispersed protein particules along the shear gradient in the narrow die channel, leading to layer and fiber formation. The restructuring of mechanically deboned meat can be achieved through extrusion cooking (40–50% water) in the presence of high levels of binders such as starch or cereal flours. Such experiments were carried out without a cooling die and without fiber formation. Emulsified and gelled cheese analogs, with textures ranging from hard blocks to soft spreads, can be obtained with a single extruder pass, starting from cheddar or from caseinate plus various fats. The extents of fat emulsification and of casein “reassociation,” and the melting ability, depend on composition and process parameters. The extrusion of fibrous products similar to mozzarella‐based string cheese is attempted. Fat substitutes with a smooth and spread‐like consistency are also prepared by thermomechanical processing of caseinate and/or whey proteins in a twin‐screw extruder at an acid or neutral pH. Shear forces and several biochemical mechanisms concur to induce the “microcoagulation” of β‐lactoglobulin as small‐size particles (<20 μm). Other potential moist extrusion processes include the coagulation of skim milk powder into an insoluble acid casein coprecipitate, the encapsulation of small molecules into protein gels, and the formation of edible thin protein films.     

Degradation of aflatoxins by extrusion cooking: Effects on nutritional quality of extrudates

Extrusion of artificially contaminated food is reported to degrade aflatoxins to varying degrees depending on the extrusion conditions. This work sought to determine the (1) efficacy of extrusion cooking in destroying naturally contaminated peanuts and (2) nutritional quality of decontaminated peanut meal. Naturally contaminated peanut meal was extruded by varying the moisture (20, 28, 35 g/100 g), pH (7.5, 9.5) and extruder die diameter (2.5, 3, 3.5, 4.0 mm). Aflatoxins levels in the extrudates were determined using HPLC procedures, and the nutritional quality was assessed using in-vitro methods. The highest aflatoxin reduction in naturally contaminated peanut meal was 59% at feed moisture content of 35 g/100 g. Higher (91%) reduction was achieved in the artificially contaminated peanut meal at moisture of 20 g/100 g. In-vitro protein digestibility and Fluorodinitrobenzene (FDNB)-available lysine of the extrudates were not significantly different from non-extruded peanut meal. Extrusion conditions for aflatoxin reduction did not adversely affect protein nutritional quality.     

挤压处理对豌豆淀粉的流变特性和体外消化率的影响

目的：研究挤压条件（豌豆淀粉水分质量分数：25%、35%、40%、45%和55%;剪切温度：50、60、70、80 ℃和90 ℃;螺杆转速：100、120、140、160 r/min和180 r/min）对豌豆淀粉的体外消化率和流变特性的影响。方法：采用体外消化法测定了豌豆淀粉的水解度,并通过稳态剪切实验、频率扫描实验和温度扫描实验测定了豌豆淀粉的流变特性。结果：挤压后水解度和慢消化淀粉（slowly digestible starch,SDS）相对含量增加,抗性淀粉（resistant starch,RS）相对含量降低;在水分质量分数为25%的条件下（螺杆转速140 r/min、剪切温度70 ℃）,SDS相对含量最高,为34.41%;在螺杆转速为180 r/min时（水分质量分数40%、剪切温度70 ℃）,RS相对含量最低,为10.49%。粒径与SDS相对含量和稠度系数K呈显著正相关（P＜0.05）,相关系数分别为0.60和0.61。挤压的豌豆淀粉溶液为假塑性流体;在频率和温度扫描实验中,储存和损耗模量随豌豆淀粉挤压损坏程度增加而增加。结论：挤压后的豌豆淀粉结构增强并表现出弹性凝胶特性。因此,挤压工艺可能通过影响豌豆淀粉的体外消化率和流变性能来改善食品的功能性和品质。     

REDUCED/OXIDIZED GLUTATHIONE INDEX AS A TOOL FOR FOOD MONITORITY OXIDATIVE STRESS DURING EXTRUSION COOKING

Reduced and oxidized glutathione was assayed in wheat, barley, rye, oats and buckwheat before and after extrusion cooking. The results obtained indicate that GSH/GSSG ratio was decreased from 1.91 and 10.72 for raw oat and buckwheat grains to the 1.13, 1.01, 1.10 and 4.72, 3.89, 3.89 for extruded material, respectively, in temperature used of 120, 160 and 200C. These results indicate that the oxidative stress is least developed during extrusion cooking of oat and buckwheat grains. Wheat and barley grains were more prone to oxidative damage, and the observed decrease of the ratio ranged from 6.84 and 4.89 (wheat cv. Almari and barley cv. Mobek, raw material) to the 1.89 and 2.07 (after extrusion cooking at 200C, respectively). No significance differences were found between two cultivars of wheat and barley being used in the experiment. The most decreased ratio up to five times was found in rye grain extrudates. The extrusion performed under barrel temperature profile of 80–100–120–120–120C caused significant decrease in GSH content when compared to raw material. The next higher barrel temperature profiles of 100–130–160–160–120C and 120–160–200–200–120C led to further GSH decrease in extruded wheat grains. In contrast, the two high temperature profiles did not     

Gelatinization Characteristics of a Cassava/Corn Starch Based Blend during Extrusion Cooking Employing Response Surface Methodology

The gelatinization characteristics of a cassava/corn starch based blend with relatively high moisture content during cooking extrusion were studied. The study was carried out by using Response Surface Methodology. The results showed that the die temperature T_d (°C) was the main influencing factor for the starch gelatinization, and the feed rate of the materials V_f (g/min) was another minor one. Because of the high material moisture content during extrusion the moisture content M_c (%) influenced the gelatinization degree not so obviously. The residence time distribution of the mass during extrusion were studied as well as discussed as a influencing factor on the gelatinization results.     

Physical and Functional Properties of Arrowroot Starch Extrudates

ABSTRACT:  Arrowroot starch, a commercially underexploited tuber starch but having potential digestive and medicinal properties, has been subjected to extrusion cooking using a single screw food extruder. Different levels of feed moisture (12%, 14%, and 16%) and extrusion temperatures (140, 150, 160, 170, 180, and 190 °C) were used for extrusion. The physical properties—bulk density, true density, porosity, and expansion ratio; functional properties such as water absorption index, water solubility index, oil absorption index, pasting, rheological, and textural properties; and in vitro enzyme digestibility of the extrudates were determined. The expansion ratio of the extrudates ranged from 3.22 to 6.09. The water absorption index (6.52 to 8.85 g gel/g dry sample), water solubility index (15.92% to 41.31%), and oil absorption index (0.50 to 1.70 g/g) were higher for the extrudates in comparison to native starch (1.81 g gel/g dry sample, 1.16% and 0.60 g/g, respectively). The rheological properties, storage modulus, and loss modulus of the gelatinized powdered extrudates were significantly lower ( P < 0.05) and these behaved like solutions rather than a paste or a gel. Hardness and toughness were more for the samples extruded at higher feed moisture and lower extrusion temperature, whereas snap force and energy were higher at lower feed moisture and temperature. There was a significant decrease in the percentage digestibility of arrowroot starch (30.07% after 30 min of incubation with the enzyme) after extrusion (25.27% to 30.56%). Extrusion cooking of arrowroot starch resulted in products with very good expansion, color, and lower digestibility, which can be exploited for its potential use as a snack food.     

Kinetics of Thermomechanical Destruction of Thiamin During Extrusion Cooking

Maize grits were extrusion cooked in a CM45-F conical, counter-rotating twin-screw extruder, at different barrel temperatures (140–200°C), feed moistures (11.8–14.2% w.b.), feed rates (37–51 kg/h), screw speeds (65–81 rpm), and initial thiamin concentrations (9–93 mg/kg). Residence time distribution was measured by a dye tracer technique. A first-order rate equation was used to model the reaction kinetics, which allowed the calculation of the destruction rate constant using residence time distribution curves. The k-values were most dependent on barrel temperature, feed moisture, and screw speed. The destruction rate constant of thiamin during extrusion cooking was a function of product temperature and shear stress.