Effects of extrusion cooking conditions and chemical leavening agents on lysine loss as determined by furosine content in corn based extrudates

The aim of this study was to investigate the effects of different variables on lysine loss as determined by furosine content in corn-based extrudates. Three formulations were prepared to study the effects of different chemical leavening agents, processing conditions (feed moisture content: 22, 24 or 26%; exit die temperature: 110 or 150 °C), and extrusion cooking methods (with/without CO₂ injection) on furosine formation. Furosine levels of extrudates from both extrusion methods decreased around 20% when feed moisture content was increased from 22% to 26%. Amadori compounds (precursor of furosine) are formed in the early stages of the Maillard reaction, and later they are converted to further products. Consequently, furosine contents of extrudates significantly decreased as exit die temperature increased from 110 to 150 °C. Furosine contents of extrudates produced with sodium- and ammonium-bicarbonate at 150 °C exit die temperature significantly decreased, while the ones produced at 110 °C significantly increased. This may be due to accelerated formation of fructosyllysine at higher pH values followed by early degradation at 150 °C. The CO₂ injection method did not have a significantly different effect on furosine content of extrudates than that produced by the conventional extrusion method, but had a positive effect on the physical properties of extrudates.     

Triticale extrudates – Changes of macrostructure,mechanical properties and molecular water dynamics during hydration

The effect of hydration (in the range of aw 0.981–0.090) on changes of macroscopic and mechanical features of triticale snacks produced in different conditions (feed moisture - 16 and 20%; extrusion temperature - 135 and 175 °C) was analysed. Changes of snacks depended both on the hydration level and the extrusion process conditions.As a result of storage at the highest hydration level (aw = 0.981) contraction of snacks was observed. The shrinkage was more pronounced in case of extrudates obtained from raw material containing 16% of water regardless of the extrusion temperature. The hardness of extrudates depended both on the feed moisture and hydration. Samples obtained from the raw material containing 20% moisture were harder than those prepared at the feed moisture of 16%. Based on the results of molecular dynamics study by low field NMR technique, a model of hydration was developed and critical hydration value of extruded snacks was calculated. Higher values of the critical hydration were obtained for snacks extruded at temperature 135 °C than for those obtained at 175 °C. The feed moisture level affected critical hydration values to a lesser extent. Obtained results suggest that the state of water in extrudates depends on extrusion process conditions.     

Preparation, physicochemical and texture properties of texturized rice produce by Improved Extrusion Cooking Technology

Using broken rice and rice bran as raw material, texturized rice (TR) was prepared by Improved Extrusion Cooking Technology (IECT) in which gelatinization is formed by means of low temperature and high pressure. The expansion of extrudate was hardly changed so that TR showed similar texture properties and shape with polished rices. The effect of rice bran addition (0% and 4%) and IECT conditions, including feed moisture content (26.6-33.4%), screw speed (20.1-32.6 rpm) and shearing compression metering zone temperature (SCMT, 69.8-120.2 °C) on the physicochemical, texture and nutritional characteristics of TR, were investigated by response surface methodology using Central Composite Design. When the bran addition was 4%, feed moisture content was 30%, screw speed was 26.6 rpm, SCMT was 95 °C, prepared TR contained 16.61 ± 0.02% of total dietary fiber, 9.40 ± 0.04% of protein, 3.68 ± 0.03% of fat, 2.42 ± 0.02 μg/g of thiamin, 0.52 ± 0.01 μg/g of riboflavin and 16.07 ± 0.12 mg/100 g of γ-oryzanol (dry matter content). The content increase of TDF for TR was 15.81% and the content increases of nutrients for thiamin, riboflavin, and γ-oryzanol were 1.39 μg/g, 0.24 μg/g, and 8.99 mg/g dry matter content, respectively, compared with those of polished rice.     

Proximate composition and some functional properties of extrusion cooked soybean and sweet potato blends

Mixtures of sweet potato flour and soy flour were made in a pilot mixer. They were moisturized with 18, 25, and 30% water and extruded in a single screw extruder at 80 rpm, using a die of 6mm. Extrusion temperature was maintained at 100 ± 3^°C. Effects of adding soy flour into sweet potato flour, as well as variation in feed moisture on the composition and some functional properties of the extrudates were investigated. Increase in sweet potato content increased carbohydrate values. Protein increased with increase in soy flour. Feed moisture did not significantly ( p 0.05) affect extrudate composition. Increase in sweet potato content and feed moisture increased expansion ratio. Bulk density decreased with decrease in feed moisture, but increased with increase in soy flour. Starch content increased as sweet potato content increased. Degree of gelatinization increased with sweet potato content. Lower feed moisture enhanced gelatinization. Water absorption index (WAI) increased as sweet potato content increased. Feed moisture had a slight effect on WAI and water solubility index (WSI). Amylose increased with increase in sweet potato content. Increase in soy flour led to an increase in yellowness (b^*) of extrudates.     

Proximate composition and some functional properties of extrusion cooked soybean and sweet potato blends.

Mixtures of sweet potato flour and soy flour were made in a pilot mixer. They were moisturized with 18, 25, and 30% water and extruded in a single screw extruder at 80 rpm, using a die of 6mm. Extrusion temperature was maintained at 100 +/- 3 degrees C. Effects of adding soy flour into sweet potato flour, as well as variation in feed moisture on the composition and some functional properties of the extrudates were investigated. Increase in sweet potato content increased carbohydrate values. Protein increased with increase in soy flour. Feed moisture did not significantly (p < or = 0.05) affect extrudate composition. Increase in sweet potato content and feed moisture increased expansion ratio. Bulk density decreased with decrease in feed moisture, but increased with increase in soy flour. Starch content increased as sweet potato content increased. Degree of gelatinization increased with sweet potato content. Lower feed moisture enhanced gelatinization. Water absorption index (WAI) increased as sweet potato content increased. Feed moisture had a slight effect on WAI and water solubility index (WSI). Amylose increased with increase in sweet potato content. Increase in soy flour led to an increase in yellowness (b*) of extrudates.     

Extrusion of a model sorghum-barley blend: Starch digestibility and associated properties

Blending cereals can maximise their food values, and understanding material-processing-property relationships guides this. A sorghum-barley (60:40) blend was extruded at different conditions to investigate the effects on extruder responses and extrudate properties. Starch digestion in the extrudates was more than in the non-extrudates, but extrusion feed rate did not significantly (P > 0.05) affect the digestibility. Specific mechanical energy reduced with the feed rate, which suggested suppressed molecular and/or structural transformations in a full extruder. Extrudate properties essentially exhibited a significant (P < 0.05) quadratic relationship with the moisture, with 30 ± 4.3% as the critical moisture, above which, the extrusion was high moisture, rate of starch digestion reduced, indices of water binding and solubility reduced, and extrudates were denser. Extrusion temperature had no significant (P > 0.05) effects on starch digestibility, but with more supplied heat as the temperature increased, water binding properties and transverse expansion increased. The increased frictional heat with the screw speed enhanced the transverse expansion also, and the browning, rate of starch digestion and rapidly digestible starch of the extrudates. There were significant Pearson correlations between the extrudate properties and with the extruder responses, which can assist in selecting conditions for desirable extrudate properties.     

Effect of extrusion cooking on chemical structure,morphology, crystallinity and thermal properties of sorghum flour extrudates

The effect of feed moisture content (10, 14 and 18%) and die temperature (110 and 160 °C) on functional properties, specific mechanical energy (SME), morphology, thermal properties, X-ray diffraction pattern (XRD), Fourier transform infrared spectroscopy (FTIR) and amylose-lipid complex formation of extruded sorghum flour was investigated. Results showed that the extrusion cooking significantly changed the functional properties of extruded sorghum flour. Increasing feed moisture increased the peak gelatinization temperature (T_p), the degree of gelatinization (%) and starch crystallinity (%) while it decreased the gelatinization temperature ranges (T_c - T₀), starch gelatinization enthalpy (ΔH_G) and amylose-lipid complex (%) formation. With increasing die temperature, the degree of gelatinization and amylose-lipid complex formation increased and the starch T_p, T_c-T₀, ΔH_G and crystallinity decreased. The FTIR spectra also showed that the extrusion cooking did not create new functional groups or eliminate them in sorghum protein, whereas the sorghum extrudate protein had random coil conformation.     

Use of amaranth,quinoa and kañiwa in extruded corn-based snacks

Amaranth (Amaranthus caudatus), quinoa (Chenopodium quinoa) and kañiwa (Chenopodium pallidicaule) are pseudocereals regarded as good gluten-free sources of protein and fiber. A co-rotating twin screw extruder was used to obtain corn-based extrudates containing amaranth/quinoa/kañiwa (20% of solids). Box–Behnken experimental design with three independent variables was used: water content of mass (WCM, 15–19%), screw speed (SS, 200–500 rpm) and temperature of the die (TEM, 150–170 °C). Milled and whole samples were stored in open headspace vials at 11 and 76% relative humidity (RH) for a week before being sealed and stored for 9 weeks in the dark. Hexanal content was determined by using headspace gas chromatography. Extrudates containing amaranth presented the highest sectional expansion index (SEI) (p < 0.01) while pure corn extrudates (control) presented the lowest SEI and greatest hardness (p < 0.01). SEI increased with increasing SS and decreasing WCM. In storage, whole extrudates exposed to 76% RH presented the lowest formation of hexanal. This study proved that it was possible to increase SEI by adding amaranth, quinoa and kañiwa to pure corn flour. The evaluation of lipid oxidation suggested a remarkable stability of whole extrudates after exposure to high RH.     

Sodium hydroxide and trimetaphosphate levels affect properties of starch extrudates

In addition to being consumed as food, starch is considered for replacement of petroleum-based plastics, but imparts negative effect like water absorption and solubilization in water. In this study, the effects of sodium hydroxide and sodium trimetaphosphate concentrations on the water absorption and solubility indices of starch cross-linked by sodium hydroxide and sodium were evaluated. Starch was granulated, and 0.3 kg granulated starch was mixed with 65 ml sodium hydroxide at three concentrations (0.2, 0.6, and 1.0 M), sodium trimetaphosphate at two levels (0.015 and 0.045 kg sodium trimetaphosphate corresponding to 5 and 15% of starch), and water to adjust moisture content to 40% (dry basis). The samples were extruded in a single-screw extruder at a barrel temperature of 130 °C and screw speed of 140 rpm. Phosphorus content and pasting viscosity of starch extrudates showed that starch was cross-linked with phosphorus that was incorporated into starch during extrusion. The extrusion and cross-linking of starch with 5% sodium trimetaphosphate reduced water absorption index, and increasing sodium trimetaphosphate percentage reduced water absorption index further at high levels of sodium hydroxide. On the other hand, the reduction in water solubility of starch extrudates required the extrusion of starch with more than 5% sodium trimetaphosphate, but increasing the sodium hydroxide level increased the water solubility index of extrudates.     

Ukrainian Dietary Bread with Selenium-Enriched Soya Malt

The production of bread with addition of selenium-enriched soya malt was studied. Processing of this soya malt included soaking of the soya beans in the solution of hydroselenite with concentration 1.5 mg Se/L (20 μg of Se per 1 g of soya beans), then 4 days of beans germination at 20 °C, drying at 50 °C until moisture content 8%, separation from the sprouts and grinding. The soya malt was a powder containing 15–18 μg of Se in 1 g. The accumulated selenium was mainly in the protein fraction of soya malt. Addition of selenium-enriched soya malt to leaven intensified activity of yeasts and lactic acid bacteria. The quality of the wheat bread with selenium-enriched soya malt was better than that of the bread in control. The enriched bread had specific pleasant smell and soft texture. The daily intake of 277 g of bread with the selenium-enriched soya malt, which is added in quantity of 1.0–1.75% to mass of plain flour, ensures the consumption of 30–50% of selenium recommended daily allowance for 17 million population of the northern and northwestern Ukraine.

     

CO2 fertilization does not affect biomass production and nutritive value of a C4 tropical grass in short timeframe

Increased atmospheric carbon dioxide (CO₂) is a consequence of recent anthropogenic environmental changes, and few studies have evaluated its effects on tropical grasses used in Brazilian pastures, the main feed source for major part of ruminant livestock. This study evaluated forage production, chemical composition, in vitro total gas production and organic matter degradability of Brachiaria brizantha under contrasting CO₂ atmospheric conditions in a free air carbon dioxide enrichment (FACE) facility. The forage plants were sown in each of the 12 octagonal rings of the FACE facility: six under ambient atmospheric CO₂ concentration of approximately 390 μmol/mol, hereafter referred to as control (CON) plots, and other six rings enriched with pure CO₂ flux to achieve a target CO₂ concentration of 550 μmol/mol, hereafter called elevated CO₂ (eCO₂) plots. Soil samples were collected to determine carbon and nitrogen concentrations. After seventy days of sowing, a standardization cutting was performed and then at regular intervals of 21 days the forage was harvested (ten harvest dates) and forwarded to laboratorial analyses. Forage above‐ground biomass production (dry matter (DM): 6,143 vs. 6,554 kg/ha), as well as morphological characteristics (leaves: 71% vs. 68%; stem: 28% vs. 31%), chemical composition (crude protein: 162.9 vs. 161.8; neutral detergent fibre: 663.8 vs. 664.3; acid detergent fibre: 369.5 vs. 381; lignin: 60.1 vs. 64.1 g/kg DM; total C: 45.9 vs. 45.9; total N: 2.8 vs. 2.8; total S: 0.2% vs. 0.2%), organic matter in vitro degradability (573.5 vs. 585.3 g/kg), methane (5.7 vs. 4.3 ml/g DM) and total gas (128.3 vs. 94.5 ml/g DM) production did not differ significantly between CON and eCO₂ treatments (p > .05). The results indicated that at least under short‐term enrichment, B. brizantha was not affected by eCO₂.     

Extrusion processing characteristics of quinoa (Chenopodium quinoa Willd.) var. Cherry Vanilla

Extrusion processing characteristics of Cherry Vanilla quinoa flour (Chenopodium quinoa Willd) were investigated using a three factor response surface design to assess the impact of feed moisture, temperature, and screw speed on the physicochemical properties of quinoa extrudates. Specific mechanical energy (SME) required to extrude this quinoa variety was higher (250–500 kJ/kg) than previously reported for quinoa. The following characteristics of the extrudates were observed: expansion ratio (1.17–1.55 g/cm³), unit density (0.45–1.02 g/cm³), water absorption index (WAI) (2.33–3.05 g/g), and water solubility index (WSI) (14.5–15.87%). This quinoa flour had relatively low direct expansion compared to cereal grains such as corn or wheat, suggesting that it is not well suited for the making of direct expanded products. The study further suggests that there is a need to understand the processing characteristics of new quinoa varieties for cultivation. Understanding extrusion and other quality traits in advance will help to select the appropriate varieties that would allow food processors to meet consumer needs.     

Effects of selected extrusion parameters on physicochemical properties and in vitro starch digestibility and β-glucan extractability of whole grain oats

Whole grain oat flour was extruded under different moisture contents (15%, 18%, 21%), barrel temperatures (100 °C, 130 °C), and screw speeds (160 rpm, 300 rpm, 450 rpm), and selected physicochemical properties, in vitro starch digestibility, and β-glucan extractability of the extrudates were analyzed. An increase in screw speed resulted in an increase in radial expansion index, water absorption index, and water solubility index. Screw speed significantly affected slowly and rapidly digestible starch. Moderate screw speed (300 rpm) led to higher slowly digestible starch with an accompanying decrease in rapidly digestible starch. Low moisture conditions (15%) resulted in the highest resistant starch and water-extractable β-glucan. Under the conditions used in this study, extrusion did not result in changes in water-extractable β-glucan molecular weight. Thus, extrusion might be beneficial in improving functionality and consumer acceptability by affecting physicochemical properties, in vitro starch digestibility, and β-glucan extractability of oat extrudates.     

Bacillus subtilis SPB1 biosurfactant: Production optimization and insecticidal activity against the carob moth Ectomyelois ceratoniae

Bacillus subtilis SPB1 was shown to produce a lipopeptide biosurfactant. The insecticidal activity of this biosurfactant was evaluated against Ectomyelois ceratoniae Zeller, a moth pest of stored dates in Tunisia. The LC₅₀ and LC₉₀ values after six days of contact were 152 μg/g and 641 μg/g, respectively. To promote an economical production of this highly effective bioinsecticide, statistical experimental designs and response surface methodology were employed to optimize the concentrations of agro-industrial residues and humidity, for lipopeptide biosurfactant production by B. subtilis SPB1 under solid state fermentation. The optimal medium leading to a production yield near to 28 mg of crude lipopeptide preparation per g of wet solid material was composed of a mixture of 4.34 g of tuna fish flour and 5.66 g of potato waste flour with a moisture content of 76%.     

Oil extraction from lesquerella seeds by dry extrusion and expelling

Whole lesquerella seeds with 6% (as is) and 12% moisture content (MC) were extruded at different residence times by varying screw speeds and feed rates. The temperature of the extrudate was recorded and its MC was determined. The extent of seed cooking was evaluated by measuring the protein solubility and thioglucosidase (TGSase) activity in the extrudate. Uncooked whole seeds (UWS), whole seeds cooked in seed cooker (CWS), and extrusion-cooked seeds (ECS) were screw pressed and the crude oils were analyzed for foots, free fatty acid (FFA), phosphorus, calcium, magnesium, and sulfur. The screw speed and feed rates employed resulted in residence times ranging from 22 to 110 s. The corresponding exit temperatures of the extrudates ranged from 88 to143 °C. Seeds with 6% initial MC dried to 4.3% at extrudate temperatures ≤125 °C regardless of residence time, while seeds with 12% initial MC came out at 7–9% MC, Extruding seeds with 6 and 12% starting MC for 34 and 41 s, respectively, provided the same degree of cooking as that of 12% MC CWS. All CWS and ECS tested negative for TGSase activity. ECS with 6% initial MC generated much higher foots (6.4–9.4%) in the oil compared with that of the 12% MC ECS (1–1.7%). The crude oils from CWS had the lowest FFA content at 1.25%. Crude oils from UWS and ECS had FFA ranging from 1.4–2.8%. The crude oil from 12% MC CWS had 374 ppm sulfur which was 3–8× higher than what were found in crude oils from 6% MC CWS and ECS. The highest P (23 ppm), Ca (14 ppm), and Mg (6 ppm) levels in the crude oil were from 12% MC CWS, which were comparable to total degummed oils. An 81% oil recovery from 6% MC ECS (22 s residence time) was obtained at 19 rpm expeller screw speed. Increasing the expeller's screw speed from 19 to 37 rpm decreased the oil recovery by 0.2%/rpm, increased the throughput by 3.3 kg/rpm from 70 to 130 kg/h, and reduced the press load from 91 to 67%.     

Moisture migration in a cereal composite food at high water activity: Effects of initial porosity and fat content

Water sorption isotherms and effective moisture diffusivities were determined at 20 °C for sponge cakes at high water activity as a function of their initial porosity, in the range 86 and 52% (0 g/g dry basis fat content), and of their fat content, ranging between 0 and 0.30 g/g dry basis (67% initial porosity). The equilibrium moisture values were not affected by food structure and decreased with increasing fat content. The effective moisture diffusivity decreased from 7.5 to 0.3×10⁻¹⁰ m²/s with increasing moisture content from 0.30 to 2.20 g/g dry basis. Decreasing initial porosity from 86 to 52% decreased effective moisture diffusivity by more than four orders of magnitude. This behaviour was related to differences of water transfer mechanisms, with the contribution from liquid water diffusion in the solid matrix and from vapour water diffusion in pores. Increasing fat content of 0.30 g/g dry basis in sponge cake, independently of porosity, decreased effective moisture diffusivity by more than five orders of magnitude. A predictive mathematical model was used to simulate moisture intake in two-composite food systems: sponge cakes with varying initial porosities and fat contents and an agar gel as a model of a non-rate limiting water source. Increasing the density of the structure or addition of fat in the cereal-based phase could increase shelf life of composite foods.     

Characteristics of destarched corn fiber extrudates for ethanol production

The effect of extrusion on characteristics of destarched corn fiber was investigated. Extrusion was conducted at a screw speed of 300 rpm, feed rate of 100 g/min, feed moisture content of 30%, melt temperature of 140 °C and die diameter of 3 mm. After extrusion, characteristics of raw and extruded destarched corn fiber were compared. Raw and extruded destarched corn fibers were enzymatically saccharified and fermented using Saccharomyces cerevisiae (ATCC 24858). Extrusion pretreatment resulted in low crystallinity index, significant decrease in degree of polymerization and microstructure disruption of destarched corn fiber for enzymatic saccharification. This provides a significant increase in xylose yield for fermentation. Significant increase in protein digestibility and free amino nitrogen were additional benefits of extrusion for yeast nutrient in fermentation. Therefore, extruded destarched corn fiber significantly increased (p < 0.05) ethanol yield (29.08 g/L) and higher conversion (88.79%) by improving the physiochemical and functional properties for saccharification and fermentation.     

Enzymatic modification and particle size reduction of wheat bran improves the mechanical properties and structure of bran-enriched expanded extrudates

The aim of this study was to examine enzymatic modification of wheat bran, performed in a low-moisture process, and the reduction of bran particle size as means of improving the technological performance of wheat bran in expanded extrudates. Modification of bran by hydrolytic enzymes increased the crispiness and decreased the hardness and piece density of extrudates containing wheat bran and endosperm rye flour in 20:80 ratio. These improvements correlated (P < 0.01 or 0.05) with an increased content of water extractable arabinoxylan and decreased water holding capacity of the bran, as well as with increased longitudinal expansion of the extrudates. Furthermore, bran with a fine average particle size (84 μm) produced extrudates with improved mechanical properties and higher radial expansion than coarse bran (particle size 702 μm). The impact of bran particle size was also observed in the cellular structure of the extrudates as differences in cell size and homogeneity. The bran drying method, oven or freeze drying after enzymatic modification, did not have a major impact on the properties of the extrudates. The study showed that the functionality of wheat bran in extrusion can be improved by enzymatic modification using a low-water process and by reduction of bran particle size.     

Kinetics of starch digestion and functional properties of twin-screw extruded sorghum

The time-course of starch digestion in twin-screw extruded milled sorghum grain was investigated using an in-vitro procedure based on glucometry. The sorghum grains were hammer-milled, and extruded at three levels each of moisture and screw speed. Irrespective of the extrusion conditions, extruded and non-extruded milled sorghum grain exhibited monophasic digestograms, and the modified first-order kinetic and Peleg models adequately described the digestograms. Extrusion increased the rate of digestion by about ten times compared with non-extrudates. Starch gelatinisation varied in the extrudates, and microscopy revealed a mixture of raw, gelatinised and destructured starch and protein components in the extrudates. Starch digestion parameters significantly (p < 0.05) correlated with extruder response and various functional properties of the extrudates. Extrusion conditions for maximum starch gelatinisation in milled sorghum grain for fastest digestion as an efficient animal feed were interpolated, as well as the conditions for directly-expanded extrudates with potential for human food, where minimum starch digestion is desired.