Extrusion studies of mixtures containing certain meat offals: Part 2-textural properties

Thermoplastically extruded products prepared from soy grits alone, and from those containing 20% or 35% of bovine or porcine offal, at various temperatures of extrusion, were subjected to instrumental texture profile analysis (hardness, elasticity, cohesiveness, gumminess, chewiness) and shear force measurements. The offal sources were untreated, or alkali-extracted, protein from bovine and porcine lung and bovine tripe (rumen and reticulum) and protein in extracted by sodium dodecyl sulphate (SDS) from bovine tripe. For products prepared from soy grits alone, hardness, gumminess, chewiness and shear force showed maxima at 170°C, whereas elasticity and cohesiveness increased progressively in the temperature range studied (140-190°C). Products containing SDS-extracted tripe protein required more force to shear, and were more hard, gummy and chewy, than products containing untreated offal, and values for all parameters were greater in the latter than in products containing alkali-extracted offal protein. The effect of extrusion temperature on the textural parameters of the products was less than that due to the mode of offal preparation used (untreated, alkali- or SDS-extracted) or the level of incorporation. Offal source was relatively unimportant. Products containing alkali-extracted offal protein had poor internal structure and were brittle; those containing SDS-extracted protein were tough. The different textural properties of the extracted products might determine their relative suitability for use either alone, as analogues or as extenders.     

Selected properties of native or modified maize starch/soy protein mixtures extruded at varying screw speed

Mixtures of soy protein isolate and native or modified (crosslinked) maize starch were extruded in a twin‐screw extruder at screw speeds of 80, 120 and 160 rpm and a moisture content of 250 g kg^?1 (dry basis). Increasing screw speed did not affect the specific mechanical energy and water solubility and absorption indices but did affect the sectional expansion index and bulk density, as the flow rate of the feed was not held constant during extrusion. The sectional expansion indices of modified starch/soy protein mixtures were higher than those of native starch/soy protein mixtures, suggesting an effect of feed material in addition to phase transition on the expansion of extrudates containing soybean. Since the bulk densities of modified starch/soy protein mixtures were lower than those of native starch/soy protein mixtures, it appears that bulk densities of extrudates containing high percentages of soy protein can be reduced by the presence of crosslinked starch in the feed. Copyright © 2005 Society of Chemical Industry     

Role of carbohydrates in soya extrusion

When extruded under similar processing conditions, soya flour yielded a far more regular, honeycombed structure than soya isolate, though both had similar expansion ratios. At low concentrations both extrudates were almost totally soluble in solutions containing sodium dodecyl sulphate (SDS) plus 2-mercaptoethanol (ME), although in SDS or ME the extrudates were only partially soluble. These results suggest that, in both cases, the extrudates are primarily stabilized by disulphide bonds and hydrophobic interactions.
When rehydrated in water at temperatures in the range 20–120°C all the extrudates exhibited decreasing toughness and increasing protein solubility with increasing temperature. Also, the soya flour extrudates, but not those prepared from the isolate, exhibited a phenomenon at the lower temperatures characterized by minimum hydratability, pH and carbohydrate solubility at about 30–40°C. It is suggested that the soya flour extrudates are additionally stabilized, compared to the extrudates prepared from the isolate, by hydrophobic interactions involving the embedded carbohydrate.     

Mechanical and microstructural properties of soy protein – high amylose corn starch extrudates in relation to physiochemical changes of starch during extrusion

Mechanical and microstructural properties of expanded extrudates prepared from blends of high amylose corn (Zeamays L. ssp. Mays) starch (HACS) and soy protein concentrate (SPC) were studied in relation to the physicochemical changes in starch. Effects of screw speed (230 and 330 rpm) and SPC level (10%, 20%, 30% and 50%) on expansion and mechanical properties were determined. Compared with 230 rpm, screw speed at 330 rpm resulted in increased specific mechanical energy, expansion ratio, water absorption and water solubility indices and decreased bulk density and piece density. Varying screw speeds did not significantly affect the mechanical strength of extrudates or starch molecular weight distribution. Bulk and piece densities, and water absorption index (WAI) only slightly increased or exhibited no significant trends as SPC level increased to 20%. A substantial increase in bulk and piece densities and decrease in expansion ratio and WAI were observed as SPC level increased from 20% to 30%. The trends were either reversed or moderated as SPC increased to 50%. These results in combination with average crushing force and water solubility index data provided a significant insight into the interactions between HACS and SPC during extrusion processing. As compared to an earlier baseline study by our research group on normal corn starch – SPC extrudates, results from the current study indicated that the expansion of extrudate containing HACS alone was lower than that of extrudates containing normal corn starch. However, expansion of the HACS–SPC blends was not significantly impacted at 10–20% SPC levels, whereas the expansion of normal corn starch was significantly reduced.     

Use of sesame oil cake (Sesamum indicum L.) on corn expanded extrudates

In the production of oil from sesame (Sesamum indicum L.) seeds, a coproduct is obtained which is rich in protein and fiber contents. Mixtures of semi-defatted sesame cake (SDSC) (0–20%) and corn grits were processed in a single screw extruder at screw speed ranging from 324 to 387 rpm to improve the nutritional value of corn expanded extrudates. Chemical composition of raw and extruded materials, sectional expansion index (SEI), texture properties, color, paste viscosity, microstructure and sensory analysis of the extrudates were performed. The addition of SDSC increased protein, fat and ash content of corn extrudates, whereas carbohydrate content was reduced. The addition of SDSC reduced the sectional expansion of the corn extrudates and increased puncture force. SDSC–corn extrudates were darker than non-SDSC–corn extrudates. Increasing SDSC increased the number of cells similar to those of commercial corn extrudates with small cells. Sensory analysis showed 20% SDSC-corn extrudates to be acceptable and nutritional balanced. The use of SDSC on corn extrudates up to 20% is an alternative to improve nutritional value keeping good sensory characteristics.     

Extrusion of Rice,Bean and Corn Starches: Extrudate Structure and Molecular Changes in Amylose and Amylopectin

The objective of this study was to evaluate the effects of starch source and amylose content on the expansion ratio, density, and texture of expanded extrudates, as well as to investigate the structural and molecular changes that occur in starch granules as a function of extrusion. The starches employed were rice starches (8%, 20%, and 32% amylose), carioca bean starch (35% amylose), and Hylon V^® corn starch (55% amylose). The extrudates from rice starches containing 20% and 32% amylose exhibited the highest expansion ratio, while, extrudates from Hylon V^® corn starch containing 55% amylose exhibited the lowest expansion ratio. The hardness values of the extrudates with 55% amylose were twice those of the extrudates with 20%, 32%, and 35% amylose. An additional finding was that although the amylopectin promoted the expansion of the gelatinized starch matrix, it failed to strengthen and sustain the walls of the extrudate bubbles during expansion.     

Development of protein-Rich Sorghum-Based Expanded Snacks Using Extrusion Technology

Sorghum is an important staple crop in semi-arid regions of Africa and India because of its drought tolerance. But low protein content and quality limit its widespread use. This project focused on developing sorghum-based extruded snacks. Results from preliminary lab-scale extrusion experiments were used to design a 2×5 factorial pilot-scale study. Two blends of sorghum flour and corn flour were prepared (6:1 and 5:2 w/w ratios) as the controls. Three different sources of protein—whey protein isolate, defatted soy flour, and mixed legume flour—were added to the sorghum/corn flour blends at 30%. A 50:50 blend of defatted soy flour and whey protein isolate was also added at 30% to the sorghum/corn flour blends. The resultant ten formulations were extruded on a pilot-scale twin-screw extruder to investigate the effects of sorghum/corn flour ratio and protein addition on product expansion, microstructure, mechanical properties, and sensory attributes. Expansion ratio of extruded product increased at the higher level of corn flour, and decreased with the incorporation of protein sources. Extrudates with defatted soy flour had a lower expansion ratio (5.3–5.4) than those with whey protein isolate (7.7–7.9), legume flour (7.1–9.9), or whey protein isolate-defatted soy flour (6.1–6.9). Extrudate microstructure, obtained by X-ray microtomography, corresponded well with expansion characteristics. Extrudates with defatted soy flour had the lowest cell diameter. Average crushing force (ranging from 40.9 to 154.87 N) was lower for extrudates with a higher level of corn flour. However, contrary to expectations, crushing force and crispness work both decreased with incorporation of protein sources. Consumer acceptability results showed that the addition of protein sources enhanced taste and overall acceptability of the extruded snacks, with the treatment sorghum/corn flour 5:2 and whey protein isolate-defatted soy flour as the protein source having significantly higher ratings than the other treatments.     

Nutritional,physicochemical, and textural properties of gluten-free extruded snacks containing cowpea and whey protein concentrate

Ready-to-eat extruded snacks with high protein and fibre were developed from a composite flour comprising rice flour, cowpea flour and whey protein concentrate (WPC). Nutritional, physicochemical, and textural properties of extrudates were evaluated, at five ratios of cowpea: WPC (10:0, 15:05, 20:10, 25:15, 30:20); rice flour was used as a control. The protein and fibre content in the extrudates significantly increased (P ≤ 0.05) with cowpea (10%–30%) and WPC (5%–20%) incorporation compared to the control. The extrudates with higher levels of cowpea and WPC showed a significant increase in bulk density and hardness. A slight decrease of 12% was observed in the expansion of 15% cowpea and 5% WPC fortified extrudates compared to the control. The number of peaks during compression increased with incorporations of cowpea and WPC. All cowpea and WPC containing snacks were darker than the control. Significant correlations were found between the protein, fibre, colour values and textural properties. The essential and non-essential amino acid profiles increased in the extrudates, proportionally to the cowpea and WPC fortification.     

Twin-Screw Extrusion Texturization of Acid and Alkali Denatured Soy Proteins

Effect of pH on functional characteristics of soy protein was investigated by modifying soy flour through acid (HCl) or alkali (NaOH) addition. Acid- and alkali-treated proteins were evaluated and texturized by twin-screw extrusion. Products were analyzed by rheological, functional, and ultrastructural methods. Acid-modified texturized protein had little expansion, increased peak force, increased work of shearing, and a nonoriented fiber arrangement. Slightly alkaline extrudates had increased rehydration but poorer texture. Stronger alkaline treatment resulted in denser products with high peak force measurements, which disintegrated when extrudates were rehydrated. The physicochemical state of soy protein, particularly conformation and protein-water interactions as affected by pH, may influence expansion of textured products and development of plexilamellar structure.     

Evaluation of Corn Protein Concentrate: Extrusion Study

Functional properties of corn protein concentrate were evaluated after extrusion with a laboratory Brabender and a Wenger X-25 extruder. Bulk density, water content and hardness after rehydration were used as criteria for textural comparison among extrudates. Results indicated that corn protein concentrates resulting from either aqueous (CPC-A) or ethyl acetate (CPC-E) extraction were more suitable for extrusion applications than the one resulting from hexane extraction. A blend containing corn protein concentrate and soy flour at the ratio of 15:85 was good for chunks and granules extrusion in the pH range 7.0 - 7.3. In a dry spinning process which requires a dough with high cohesiveness for fiber formation, a blend containing 21% of corn protein concentrate, 20% soy isolate, and 59% soy concentrate at a natural pH was satisfactory.     

EXTRUSION BEHAVIOUR AND PRODUCT CHARACTERISTICS OF BROWN AND MILLED RICE GRITS

ABSTRACT

Extrusion behaviour of milled and brown rice grits obtained from six rice cultivars (Jaya, IR-8, PR-103, PR-106, Pusa No.1 and Basmati 385) was investigated using Brabender single screw extruder. Feed moisture of the grits was adjusted to 16%, and extrusion cooking was done at barrel temperature of 150°C and screw speed of 100 rpm. The milled and brown rice grits from different rice cultivars differed significantly with respect to extrusion behaviour and extrudate characteristi cs. Extrudates obtained from milled rice grits showed higher die pressure, expansion, water absorption index (WAI) and water solubility index (WSI) as compared to those from brown rice. WSI of extrudates varied from 3.38 to 10.5%, WAI from 5.20 to 6.90, die pressure from 6068 to 9325 kPa and expansion from 7.52 to 11.30 respectively. The grits from cultivars which had lower length-breadth ratio and mealy endosperm resulted into more expanded extrudates and hence were found to be more suitable from extrusion.     

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

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

Extrusion Studies of Aquaculture Feed using Distillers Dried Grains with Solubles and Whey

Three isocaloric (3.5 kcal/g) ingredient blends containing 20, 30, and 40% distiller-dried grains with solubles (DDGS) along with 5% whey were prepared with a net protein content adjusted to 28% (wet basis [wb]). Other ingredients in the blends included soy flour, corn flour, fish meal, vitamin, and mineral mix. These blends were extruded in a single-screw extruder at 15, 20, and 25% (wb) moisture content and at 130 and 160 rpm screw speeds. Compared to previous research, the durability and unit density of the extrudates in this study were found to increase substantially by the addition of whey to the blends. Increasing the DDGS content from 20 to 40% resulted in a 5.8 and 16.8% increase in extrudate moisture content and redness, respectively, but produced a decrease of 11.2% in brightness and 3.6% in yellowness of the extrudates. Increasing the moisture content of the ingredient blends from 15 to 25% resulted in an increase of 16.1, 8.7, and 9.3% in moisture content, durability, and redness, respectively, but a decrease of 9.8 and 5.6%, respectively, in brightness and yellowness of the extrudates. Neither DDGS level nor screw speed significantly affected extrudate durability or unit density. In fact, changing the screw speed had no significant effect on many of the properties of the extrudates studied, except for moisture content, redness, and yellowness. As demonstrated in this study, ingredient moisture content and screw speed are critical considerations when producing extrudates with feed blends containing DDGS; further work is needed to optimize processing conditions and to produce floating feeds.     

The effects of extrusion conditions and the addition of volatile compounds and flavour enhancers to corn grits on the retention of the volatile compounds and texture of the extrudates

Corn grits that were supplemented with isovaleraldehyde, ethyl butyrate, butyric acid and flavour enhancers were extruded under different processing conditions. Volatile compounds retained in the extrudates were isolated by dynamic headspace and analysed using gas chromatography–mass spectrometry. The expansion ratio, density and cut force to break down the extrudates were evaluated and aroma intensity was assessed using a multisample difference test. Butyric acid showed the greatest retention (96.4%), regardless of the extrusion conditions. All compounds were better retained when samples were extruded at 20% feed moisture and 90 °C processing temperature (2.9–81.0%), conditions that also resulted in greater aromatic intensity (moderate to moderate‐strong intensity). The addition of volatile compounds reduced the expansion ratio and cut force, whereas the addition of flavour enhancers increased the expansion ratio but reduced ethyl butyrate and butyric acid retention.     

蜂蜡和甘油含量对大豆蛋白膜机械性能和阻隔性能的影响

研究添加蜂蜡(质量分数分别为1%、2%、3%、4%、6%、8%和10%)和甘油(质量分数分别为40%和50%)交互作用对大豆蛋白膜机械性能和阻隔性能的影响。结果表明,蜂蜡以固体小颗粒的状态分散于大豆蛋白膜中,能够提高大豆蛋白膜的抗张强度、氧气透过率、阻水性能和表面接触角,降低水蒸气透过率以及断裂延伸率。甘油浓度升高有助于蜂蜡与大豆蛋白分子相结合,提高大豆蛋白膜的综合性能。     

Effect of the extrusion process on allergen reduction and the texture change of soybean protein isolate-corn and soybean flour-corn mixtures

Soy protein and corn meal are widely used as main ingredients in the cereal and snack industries. We studied the effect of extrusion processing on the immunoreactivity of proteins in soy protein isolate-corn meal (SPI-corn) blends and soy flour-corn meal (SF-corn) blends using a full-factorial design with two levels of temperature, moisture, and screw speed (SS). The changes in protein solubility, protein secondary structure and physical properties, such as the expansion ratio, specific volume, water hydration capacity (WHC), texture, and color, were also studied. The western blotting results illustrated that extrusion processing decreased the immunoreactivity of proteins in SPI-corn and SF-corn blends and eliminated certain allergenic proteins in SF-corn extrudates. The enzyme-linked immunosorbent assay (ELISA) results indicated that different extrusion conditions decreased the immunoreactivities of SPI-corn and SF-corn blends in the ranges of 53%–68% and 80%–86%, respectively, compared with the raw material. The protein solubility decreased after extrusion by >58.7% for SPI-corn extrudates and by 66.3% for SF-corn extrudates compared with the initial materials and decreased significantly for both SPI-corn and SF-corn extrudates with the increase in extrusion temperature (P < 0.05). The α-helix structure decreased and β-strand structure increased after extrusion for both SPI-corn and SF-corn blends. Higher moisture significantly decreased the expansion ratio, specific volume and WHC of SPI-corn and SF-corn extrudates, as well as increased the energy required to cut the samples. Thus, the effect of extrusion on allergenic proteins using the human plasma of subjects allergic to soybean and corn showed that moisture had a clear effect on their reduction. Product treated with low moisture (20%), regardless of the starting material used, was the most effective based on the reduction of allergenic proteins.     

EXTRUSION OF MINCED CATFISH WITH CORN AND DEFATTED SOY FLOURS FOR SNACK FOODS

Response surface methodology (RSM) with a rotatable central composite design was used to determine an extrusion condition that would produce extrudates of a maximal expansion ratio from blends of catfish flesh (20%), corn flour and defatted soy flour (DSF) using a single‐screw laboratory extruder. Feed moisture, process temperature and DSF level were selected as independent variables. Analyses of the response indicated that the combination of 26.9% moisture, 160.1C and 4.95% DSF would result in extrudates with maximal expansion. The snack food made with the aforementioned combination and 74.74% corn flour in feed was slightly less dense than malted milk balls and much less hard than cocktail peanuts, according to a trained sensory panel. “Grain complex” was the most intense flavor note. When 1% garlic or onion powder was added to the feed formulation, the spice flavor notes were detected in extrudates. No fish flavor note was perceived in any of the extrudates.     

DEVELOPMENT AND EVALUATION OF AN EXTRUSION-TEXTURIZED PEANUT PROTEIN

A commercial defatted peanut flour was analyzed for texturization properties in a Wenger X-25 extruder. Extrusion of the flour with addition of sodium stearoyl-2-lactylate resulted in a steady state operation and uniform texturized products. Functional properties of the extrudates such as water retention, hardness, and product integrity upon retorting: were similar to those of textured soy protein. Organoleptic properties of prepared patties (30:70 hydrated textured protein to meat ratio) were not different from the all-meat control for the analyzed sample; cooking losses and shrinkage were lower. Flavor was the most limiting factor for higher levels of incorporation and acceptance. A scanning electron microscopy study showed correlation between microstructure and the properties of the extrudates.     

Air Classification and Extrusion of Navy Bean Fractions

Pilot plant air classification or raw beans (Phaseolus vulgaris) produced high-protein fractions (HPF) containing 51.4% protein and high-starch fractions (HSF) having about 50% starch. Particle size distribution analyses and scanning electron micrographs confinned the fractionation of starchy and proteinaceous materials. Extruded corn/HSF blends had lower water absorption and water solubility indices, higher protein content, and a better balanced amino acid pattern than pure corn extrudates. Extrusion-texturized vegetable proteins obtained by substituting HPF for defatted soy flour at levels of 10, 20 and 30% had similar functional properties as the 100% texturized soy. Air classification followed by extrusion-cooking is a feasible alternative for dry-processing of beans into products for human consumption.     

Effect of Pre-Treatments on Mechanical Oil Expression of Soybean Using a Commercial Oil Expeller

The effect of expeller screw press and pre-treatments on the quality and quantity of soybean oil and cake was studied using a commercial oil expeller. The pretreatments included whole soybean crushing, soy grits crushing, and crushing of soy grits extruded at 135°C. The screw speeds were 28, 35, and 45 rpm. The moisture content of soybean used in the experiment was 10% wet basis. The average capacity of the oil expeller was found to be 145 kg/h, 110 kg/h, and 120 kg/h for whole, grits, and extrudate, respectively at 45 rpm. The average capacity of oil expression from whole soybean did not vary significantly from 28 to 45 rpm. In the case of soy grits, however, the capacity was higher when the expeller speed was lowest, i.e., 28 rpm. In the case of extrudate, even in a single pass, the recovery was higher, i.e., to 71% at both 45 and 35 rpm. The color of oil from soy grits was lighter followed by extrudate, and the color of oil obtained from whole soybean was dark. The FFA in oil from all the samples was below 1%, however the lowest percentage was for oil obtained from extrudate at 0.5%. The urease activity of the extruded cake was 0.15 pH units, and the protein and oil content were about 48% and 5%, respectively. The optimum process variables for mechanical expelling of soybean were found to be extrusion as a pretreatment and speed of expeller screw at 45 rpm, which yielded throughput capacity 103 kg/h, oil recovery of 70.5%, and urease activity of the cake at 0.15.