Evaluation of the protein quality of legume flours obtained by roasting in heated beds

Roasted flours from cowpea, canavalia and washed lupin were prepared by a thermic treatment in fluid sand beds at 150, 200 and 250 degrees C for 2.0 and 2.5 minutes, followed by dehulling and grinding. A flour produced by pressure cooking at 121 degrees C for 30 min followed by drying was used as reference. The flours were evaluated through residual levels of antitryptic activity, tannin content, available lysine, NPR and protein digestibility. The roasting and the pressure cooking processes increased NPR values. Nevertheless, the NPR values of all legume flours were significantly lower than the NPR casein values. The roasting process carried out under the conditions indicated inactivated trypsin inhibitor activity significantly. A small decrease in tannin content was also observed, with small insignificant changes in available lysine. The protein digestibility of all products was high with lupin, digestibility being equal to that observed for casein. The roasting process in a fluid granular bed allows the production of products of acceptable protein quality with low levels of antiphysiological factors.     

Handling properties of cereal materials in the presence of moisture and oil

A powder flow analyzer attached to a Texture Analyser (Stable Micro Systems, UK) was used to compare the flow behaviour of four cereals systems: maize and wheat (in both starch and flour forms), as functions of particle size and distribution, water content and the addition of different types of oil. It was expected that the smaller the particle size the higher the tendency to stick (because of less free volume between the particles), but that was not the case. The results showed that wheat starch used, with bigger particle size than maize starch, had higher cohesion properties and as water content increases the cohesion increases by the same magnitude. This was attributed to the differences in granular shape as well as protein quantity and quality. Caking strength for both starches was influenced by the water content; in particular at 30% water content (w/w), neither cohesion nor caking indices could be measured for wheat starch because of the high stickiness of the particles.Although the two flours had particles of very similar sizes, with differences in the distributions only, maize showed higher cohesion indices compared to wheat flour. These values decreased with increasing water content. The caking property for maize was not significantly affected by water content with values of approximately 100 ± 5. The caking strength increased for wheat flour from 8 to 500 as moisture increased from 12.5 to 30%. This was ascribed to the differences in hydration properties of the two flours. For wheat flour and as the water content increased, gluten started to form and would require more than 30% to form a homogenous, visco-elastic mass.Generally, cohesivity and cake forming ability were affected by water content as well as the physical state of the oil i.e. by the solid/liquid ratios. As water content increases, wheat starch showed the greatest packing and cohesive behaviour, with and without the oil, while maize flour exhibited the weakest packing and cohesive properties.     

Yield and functional properties of air-classified protein and starch fractions from eight legume flours

Eight legumes were pin-milled and air-classified into protein (fine) and starch (coarse) fractions and their functional properties compared with those of soybean and lupine flours. The fine material which represented 22.5 to 29% of the original flours contained from 29 to 66% protein as well as a high proportion of the flour lipids and ash. The coarse material contained 51 to 68% starch and much of the crude fiber which was dense and concentrated in the starch fraction. Generally legumes which showed highly efficient starch fractionation gave lower recoveries of protein in the fine material. High values for oil absorption, oil emulsification, whippability and foam stability were characteristics of the protein fractions, while starch fractions gave high water absorptions, peak and cold viscosities. Gelation occurred in both air-classified fractions. Pea and northern bean, chickpea and lima bean flours, and airclassified fractions gave generally higher values in the functional property tests, while fababean, field pea, mung bean and lentil gave high protein fractionation in the air classification process.     

Effect of processing and amino acids supplementation on the protein quality of amaranth (Amaranthus caudatus)

The present study was undertaken to evaluate the effect of thermic processing on the protein quality of amaranth (A. caudatus). It was also intended to establish the order of essential amino acid deficiencies suggested by the chemical score as limiting protein quality. The A. caudatus grain was cooked in water in the autoclave at 15 lb pressure during 0, 10, 20, 30, 40, 50 and 60 min. Once cooked, the samples were dehydrated with hot air at 60 degrees C and ground into flours. These were analyzed for: tannins, trypsin inhibitors, hemagglutinins (with cow, sheep, and human erythrocytes), damaged starch, available lysine, protein quality (by the NPR method), and true digestibility. Results indicated that the flours (0 to 60 min cooked) did not contain trypsin inhibitors and that their small tannin content, expressed as catechin, disappeared after 30 min of cooking. The quantities of these antiphysiological substances in the raw material are so small that they do not constitute a factor that may cause a decrease of the product's quality. A positive response was obtained for hemagglutinins, stronger with human erythrocytes, which disappeared with cow's and sheep's erythrocytes after 10 min of cooking and with human erythrocytes, after 20 min. As expected, cooking time increased the damaged starch and a slight increase was observed in available lysine, a finding which was impossible to explain satisfactorily. There were no important changes in true protein digestibility with respect to cooking time. Once again, results demonstrated the positive effect thermic treatment had on protein quality, suggesting the presence of antiphysiological active substances or a low nutrient bioavailability in raw samples. Longer cooking times did not alter substantially the protein quality (NPR and digestibility) and it was concluded that 10 min of cooking is an adequate time for the type of processing used. A sample of processed A. caudatus was utilized for the supplementation studies carried out with threonine, methionine, leucine, individually, or with the three amino acids together at 8.0, 9.5 and 1.0% protein in the diet. According to the results obtained, higher NPR values were observed with 9.0 and 9.5% protein content in the diet. No clear effects were detected when the amino acids were added, but there was an interaction between protein in the diet and amino acids. No effect occurred when leucine was added, suggesting that it is not a limiting amino acid. Possibly, threonine is a more limiting amino acid, but the effects were not as high, probably due to the level added to the diets.(ABSTRACT TRUNCATED AT 400 WORDS)     

Evaluation of two methods to determine the polyphenol content in raw and cooked beans and its effect on protein digestibility]

The polyphenolic compounds present in raw and cooked, and dried, with and without the cooking broth of common white, black and red beans (Phaseolus vulgaris) were measured by the Folin-Denis method for total polyphenols, and by the protein precipitation method of Hagerman-Butler, which measures their biological activity. The polyphenol content was measured during 20 consecutive days on the same sample, using three different extracts of volume from each sample. Statistical analysis of the results by the Folin-Denis method indicated that variability among the three aliquots was different for each bean color. A non-parametric analysis, however, indicated that the average in the three levels of concentration for beans of all colors, was the same. A similar analysis of the results by the Hagerman-Butler method demonstrated that variability and average values for the three aliquots were equal for black and red beans but not for white beans. The coefficient of variation was lower for the higher aliquot of the extract. A significant correlation (r = 0.72, P less than 0.05, n = 60) was found between the two methods for all beans using the larger aliquot of the extract. The correlation was highly significant (r = 0.84, P less than 0.05) when white bean values were eliminated. The polyphenolic content varied with seed color and the thermic process reduced their content, as measured by the two methods. The losses in polyphenolics as measured by the Folin-Denis in the cooked beans dried with broth, varied from 31.4 to 36.3%, and from 39.8 to 51.1% for the cooked bean flour dried without broth. The losses by the Hagerman-Butler method were from 25.0 to 93.5% in the cooked bean flours dried with cooking broth, and from 33.3 to 95.7% when dried without the broth. The higher losses were recorded for red beans. In vivo digestibility for cooked bean flours, dried and without broth, were 73.2, 69.6 and 64.5%, and 71.9, 71.9 and 68.8% for white, red and black beans, respectively. A negative correlation (r = -0.39) and significant (p less than 0.05) was found between polyphenolic content in the diet and in vivo protein digestibility.     

Twin-screw extrusion texturization of extruded-expelled soybean flour

Texturized soy proteins (TSP) have been produced from hexane-extracted soy flours having a narrow range of characteristics. The objective of this study was to determine the influence of protein dispersibility index (PDI) and residual oil content on extrusion texturization of partially defatted soy flours produced by extruding-expelling (E-E). Ten E-E processed soy flours having residual oil contents and PDI values of 5.5–12.7% and 35.3–69.1%, respectively, were texturized using a twin-screw extruder. Water-holding capacities were greater for TSP prepared from E-E processed soy flours with lower residual oil contents. Bulk densities were significantly lower for TSP prepared from E-E processed soy flours compared with a commercial product made from hexane-extracted soy flour. The texture characteristics of extended ground beef patties containing texturized E-E processed soy flour were similar to that of 19% fat ground beef. Flavor acceptability was directly correlated (R=0.761) with residual oil content of the E-E processed soy flours. However, lower residual oil and higher PDI flours exhibited better texturization and extrudate qualities.     

Functional properties of extruded-expelled soybean flours from value-enhanced soybeans

The functional properties (protein solubility, emulsification characteristics, foaming characteristics, water- and fatbinding capacities) of extruded-expelled (EE) soy flours originating from six varieties of value-enhanced soybeans (high-sucrose, high-cysteine, low-linolenic, low-saturated FA, high-oleic, and lipoxygenase-null) and two commodity soybeans were determined. The soy flours varied in protein disperisibility index (PDI) and residual oil (RO), with PDI values ranging from 32 to 50% and RO values ranging from 7.0 to 11.7%. Protein solubility was reduced at pH values near the isoelectric region and was higher at both low and high pH. There were no significant differences for water-holding capacity, fat-binding capacity, emulsification activity, or emulsification stability. Only the high-oleic soy flour had significantly lower emulsification capacity. In general, the PDI and RO values of EE soy flours originating from value-enhanced and commodity soybeans had the greatest influence on protein functionality. The genetic modifications largely did not affect functional properties.     

Extruded rice flour as a gluten substitute in the poduction of rice bread

Research regarding the production of gluten-free bread (GFB) is very important nutritionally, technically and economically speaking, both to celiac patients and to developing countries who import wheat. The main technological problem in the production of GFB is obtaining a gluten substitute that is both inexpensive and capable of retaining gas during bread fermentation and baking. The use of gelatinized starch as an alternative for gluten seems promising. In this project, rice bread was made using pregelatinized extruded rice flour as a gluten substitute. Pre-gelatinized rice flours (PRF) were manufactured in a single screw Brabender extruder, varying extrusion temperature (108-192 degrees C) and the moisture of the raw material (19.2 - 24.8%), and were used in a proportion of 10 g for every 100 g of raw rice flour, in the production of gluten-free bread. Results showed that rice flour extruded at a high temperature (180 degrees) and low moisture content (20%), rendered bread with the best technological characteristics, presenting crust and crumb color similar to those of conventional wheat bread, although with volume and texture not as satisfactory in the same comparison.     

Optimal Operating Conditions to Produce Nutritious Partially Parboiled Brown Rice in a Humidified Hot Air Fluidized Bed Dryer

V-type amylose–lipid complexes present in partially parboiled rice can decrease starch digestibility. Formation of such complexes can be accomplished using high-temperature fluidized bed drying; the degree of the complexes depends on the thermal condition. The effects of drying media (hot air and humidified hot air), operating conditions (drying air temperature and relative humidity [RH]), and the initial moisture content on the degree of V-type crystallinity and subsequent starch digestibility (or glycemic index, GI) and brown rice texture were examined experimentally. The results showed that paddy drying with humidified hot air (HHA) requires a longer time than hot air (HA). Higher drying air temperature, RH, and initial moisture content of paddy yield higher degrees of starch gelatinization and V-type amylose–lipid complexes. The brown rice dried by HA or HHA had lower starch digestibility and a harder texture than the reference sample. Within the range of parameters studied, to obtain the lowest GI for the dried brown rice, paddy at an initial moisture content of 33% (db) should be dried by HHA at 150°C and 6.4% RH.     

Evaluation of the starch fraction in corn products consumed regionally

The purpose of this study was to evaluate through conventional analytical procedures, the degree of modification of the starch fraction of regional products based on corn, such as grits, flours, precooked grits, flakes, precooked flour, "frangollo" and "locrillo." Based on the interpretation of changes in the starch fraction, the following conclusions are reached. Corn grits, flours, "frangollo" and "locrillo" are raw corn products subjected to physical processes such as shelling, degermination and size reduction. They do not show changes in their physicochemical characteristics. Precooked grits present certain structural modification (among others, changes in their rheologic behavior) and partial molecular change (among others, changes in the insoluble carbohydrate fraction), indicating that they have been subjected to processes wherein factors such as temperature, moisture and/or pressure intervene. Corn flakes and precooked flours show a high enzyme digestibility and a high degree of change in their functional properties (mainly, in regard to solubility, absorption and viscosity). These changes indicate modification at granular and molecular level.     

Nutritive value of lupine and its potential as human food

The chemical composition and some indices of protein quality were measured in two species of sweet lupine Lupinus albus and Lupinus luteus grown at the Experimental Station in Gorbea, Chile: both samples showed a high protein content (39.5 and 44.6%). The protein efficiency ratio (PER) was measured in the rat and found to be 0.48 and 0.71, respectively, as compared to 2.57 for casein. Supplementation with 0.3% DL-methionine increased significantly those values, thus indicating that lupine protein is deficient in said amino acid. In another experiment the effect of cooking-extrusion on lupine flour (L. albus) was investigated and the chemical composition, protein efficiency ratio, methionine supplementation and digestibility of the protein were measured. The chemical composition was not changed but PER increased from 0.50 for raw lupine to 0.76 for processed lupine (P less than 0.05). Both values increased significantly with the addition of 0.3% DL-methionine. The protein digestibility of the supplemented lupine was not affected by the cooking extrusion process (76.5 and 77.8%, respectively). Supplementation of wheat flour with 5, 10, 15 and 20% lupine flour increased the PER of wheat flour from 0.92, to 1.39 for wheat flour supplemented with 10% lupine flour, and to 1.60 for the 15% level of the supplement. These studies seem to support the conclusion that sweet lupine is an interesting protein resource for human nutrition.     

Mechanical and physical properties of protein-starch based plastics produced by extrusion and injection molding

Processing conditions, ingredient ratio, and moisture content were optimized for making soy protein/starch based plastics using a twin-screw extruder and an injection molding machine. A metering pump and a high speed mixer were used for ingredient mixing. The optimal processing temperature for injection molding was 130°C, and the moisture content of extruded pellets was 10–14%. Processing effects were investigated by measuring the tensile properties and water resistance of specimens. Reduction of water and glycerol in mixtures increased the barrel pressure of the extruder. Mold release was improved by incorporating 0.25 parts tallow per 100 parts of solid material (soy protein and starch). The water absorption of the specimens was reduced by adding acids to adjust the pH to the isoelectric point of soy proteins (pH 4.5). Effects of storage at different relative humidities were studied. The processibility of pellets was stable after a 4-wk-storage period, despite some moisture loss. Injection-molded specimens, after being stored for up to 6 mon at dry conditions [50 and 11% relative humidity (RH)] at room temperature and for 4 wk in a 50°C oven, showed no surface crack. However, humid (93% RH) storage at room temperature promoted fungal growth after storage for 3 mon, indicating that preservatives such as potassium sorbate and propionic acid were needed.     

Effect of moisture content on tensile properties of starch/poly(hydroxyester ether) composite materials

The effect of moisture content on the mechanical properties of starch/poly(hydroxyester ether) (PHEE) composite materials has been characterized. Cornstarch with either 1 or 10% moisture content was extruded with PHEE. Total moisture content (TMC) during subsequent injection molding ranged from 1.0 to 10% (total solids basis). Starch granule structure, determined by X-ray diffraction and scanning electron microscopy, was progressively disrupted but not completely destroyed (as in thermoplastic starch) as TMC during molding increased. Tensile strength and modulus values were not significantly impacted when the TMC was 6% or less. As TMC increased above 6%, both properties decreased rapidly, while strain to break increased. Tensile strength increased when samples prepared at high TMC were equilibrated to a lower value. Changes in weight average molecular weight of the PHEE during processing were not significant as measured by gel permeation chromatography, even at the highest moisture contents. The effects of TMC on mechanical properties of starch/PHEE materials are shown to be due to changes in the viscoelastic response of the PHEE matrix, by comparison of starch/PHEE results to those of neat PHEE [Polymer 42 (2001) 5643].     

Supplementation of wheat flour with chickpea (Cicer arietinum) flour. II. Chemical composition and biological quality of breads made with blends of the same

Experimental bread made of wheat flour complemented with 5, 10 and 15% chick-pea flour was studied, using wheat bread as control. Samples were analyzed for their proximal chemical composition and amino acids content. Crude fiber and protein increased from 0.36% to 0.55%, and from 14% to 17.6%, respectively, when 15% chick-pea flour was added. The lysine content increased as the level of supplementation was raised. Biological quality of proteins was measured in rats as protein efficiency ratio (PER) as well as apparent digestibility resulting in an increase of PER values from 0.90 to 1.34 and small variations in bread protein digestibility. Bread nutritive value was significantly improved by adding chick-pea flour.     

ABS树脂湿法挤出工艺及产品力学性能的研究

采用湿法挤出工艺,即将乳液聚合合成的经凝聚和过滤的丙烯腈-丁二烯-苯乙烯（ABS）湿粉料与苯乙烯-丙烯腈共聚物（SAN）树脂以一定的比例投入湿法挤出机内挤出造粒,直接获得了ABS树脂。考察了ABS粉料含水量、ABS树脂中橡胶含量、抗氧剂含量、挤出机温度及螺杆转速等因素对ABS树脂力学性能的影响。结果表明,挤出温度过高明显引起物料降解,ABS树脂的冲击强度减小,拉伸强度降低;ABS粉料含水量对ABS树脂的性能没有明显影响;透射电子显微镜分析表明,橡胶粒子在SAN基体中分散均匀;湿法挤出的最佳工艺参数为,挤出温度：180 ℃,螺杆转速：200 r/min,抗氧剂含量：0.154 %（质量分数,下同）。     

Protein functionality modification by extrusion cooking

Cooking extruders process high-protein materials into palatable foods. New applications have been developed for protein extrusion during the past decade. Improvements in functional characteristics of proteins may be achieved through modification of temperature, screw speed, moisture content, and other extrusion parameters. Flavors and odors may be removed during expansion at the extruder die. Extrusion can improve the digestibility of proteins, while reducing gossypol, proteinase inhibitors, allergens, aflatoxins, and other undesirable compounds. In the future the use of extruders as chemical reactors for both animal and plant proteins will provide new food ingredients as well as novel, nutritious foods. Presented at the 81st AOCS Annual Meeting, Baltimore, 1990.     

The effects of extruder variables on the gelatinisation of corn starch

The first stage of a study of the extrusion of starch-based materials is described. The chemical and physical changes which occur in the extrusion of a corn starch-water system relative to fifteen extruder variables have been investigated. A mathematical model of the extruder has been obtained from analysis of the data. The important variables were found to be moisture, barrel and die temperatures, screw speed and screw geometry. A strong interaction between moisture and barrel temperature was found to occur. These variables in the model account for 90.5% of the variance in the data obtained. The effects of the variables on the gelatinisation and shearing mechanical degradation of starch are discussed.     

Tailored biodegradable films via extrusion blow molding using PBS,PBAT, and TPS

Research to replace synthetic polymers with biodegradable polymers is on the rise because common plastics have generated serious ecosystem problems. Films with thermoplastic starch (TPS), poly(butylene succinate) (PBS), poly(butylene adipate-co-butylene terephthalate (PBAT), and citric acid (CA) were produced by blown extrusion. They were characterized by blow-up ratio (BUR), water vapor permeability (WVP), soluble ratio (SR), water sorption isotherm, and thermogravimetric (TG) techniques. Films were uniform and showed BUR > 205%. The different proportions of PBS and PBAT significantly influenced the WVP of the films. All samples had WVP with an order of magnitude similar to other blends with high starch content (10⁻⁶ g m⁻¹ day⁻¹ Pa⁻¹). CA efficiently decreased the WVP of the PBS/PBAT/TPS formulations (15/15/70% and 20/10/70% by mass) by 25.2% and 24.7% compared to the acid-free formulations. There was no significant difference in SR (19.0%–20.1%). These materials were sensitive to moisture since the equilibrium moisture content increased pronouncedly from water activity of 0.5. Films showed good thermal stability, with a maximum decomposition temperature close to pure polyesters. CA did not increase the thermal stability of blends, probably because of the low content used (0.1%). Given the outcomes of this study, these films could be deemed appropriate for applications in food packaging.     

Nutritional evaluation of roasted, flaked and popped A. caudatus

A study was carried out with a selection of A. caudatus CAC-064, which was processed in three different forms: popped, flaked and roasted. The popped sample was prepared by subjecting the grains to a temperature between 175 and 195 degrees C for 15-25 seconds. The flaked sample was obtained by adjusting moisture content to 26% and using heated (200 degrees C) rotating drums for a contact time of 1-3 seconds, and roasting was achieved by heating the grain at 150 degrees C for a lapse of 60-90 seconds. All samples, including a raw sample, were analyzed for proximate chemical composition, minerals, available lysine and tryptophan content, as well as damaged starch, calories, soluble and insoluble fiber, and protein quality. Differences in chemical composition due to the processing applied were small and insignificant, except for lower available lysine values, and insoluble fiber with higher values in the roasted sample than in the flaked and popped samples. Likewise, the roasted sample had higher levels of damaged starch. Protein quality was highest in the popped sample (NPR 3.19), followed by the flaked (NPR 2.78), the roasted (NPR 2.24) and the raw (NPR 1.73) samples. These values were related to available lysine. Protein digestibility was lowest in the roasted material followed by the flaked and the popped products. It is concluded that establishment of optimum processing conditions is necessary in order to achieve maximum utilization of amaranth grain.