Effect of germination time and temperature on the functionality and protein solubility of sorghum flour

Sorghum was germinated for different time (12, 24, 36 and 48 h) at different temperatures (25, 30 and 35 °C) and the changes in their nutritional and functional properties of germinated sorghum flour were assessed and compared with native sorghum flour. Germination inversely affects the crude protein, fat, fibre and ash content. A decrease in water absorption and swelling power and increase in oil absorption capacity was observed due to enzymatic starch modification as the germination duration progressed. Germination of sorghum increased the gel consistency while paste clarity was decreased as compared to native flour. Proteins were modified by action of enzymes during higher germination time and temperature conditions, which results in significantly higher protein solubility of germinated sorghum flour, which also result in enhancing the foaming and emulsifying properties of the flour. Lowest % synersis value and least gelation concentrations were observed in native sorghum has, which increased during germination and were highest in sorghum germinated for 48 h at 35 °C. Germination in overall can be used as low cost natural bio-processing technique for the preparation of modified flour with enhanced function properties without chemical modification or genetic engineering.     

Biochemical and sensory evaluation of wheat bran supplemented sorghum bread

Addition of wheat bran to sorghum flour (Dabar cultivar) at two extraction rates 72% and 80% resulted in lowering reducing sugars. The percent decreasewas 75.6% compared with the control at the end of fermentation period. There was a highly significant (p 0.05) increase in crude fiber content as a result of addition of wheat bran. The increase was from 0.8 to 5.2 and from 0.5 to 5.3% for the 80% S/WB and 72% S/WB blends, respectively. Sorghum bread containing wheat bran was lower in reducing sugars and showed a significant increase (p 0.05) in starch content. Sorghum bread containing wheat bran resulted in a lower in vitro protein and starch digestibilities.     

Sorghum for human food – A review

A brief review of literature on sorghum for human foods and on the relationship among some kernel characteristics and food quality is presented. The chief foods prepared with sorghum, such as tortilla, porridge, couscous and baked goods are described. Tortillas, prepared with 75% of whole sorghum and 25% of yellow maize, are better than those prepared with whole sorghum alone. A porridge formulation with a 30:40:30 mix of sorghum, maize and cassava respectively, has been shown to be the most acceptable combination. The cooked porridge Aceda has lower protein digestibility and higher biological value than the uncooked porridge Aceda. Sorghum is not considered breadmaking flour but the addition of 30% sorghum flour to wheat flour of 72% extraction rate produces a bread, evaluated as good to excellent.     

Characterization of sorghum grain and evaluation of sorghum flour in a Chinese egg noodle system

Sorghum is a gluten free grain that has potential to be used as an alternative to wheat flour for the Celiac Sprue market. There are thousands of sorghum lines that have not been characterized for grain, flour or end product quality. The objective of the research was to gain an understanding among grain sorghum quality factors and Chinese egg noodles quality. Four sorghum hybrids were characterized and evaluated for kernel characteristics, proximate analysis, flour composition and end product in a Chinese egg noodle system. Kernel size and weight affected the flour particle size and the amount of starch damage. Flour with fine particle size and high starch damage conferred noodles with high firmness and high tensile strength. Water uptake was highest for flour with smaller particle size (38 μm at 50% volume) and higher starch damage (6.14%). Cooking losses for all samples were below 10%. Starch of particle size <5 μm (C-type) contributed to firmer and higher tensile strength noodles. Water absorption was significantly affected by flour particle size, starch particle size and starch damage. Through control of sorghum grain and flour quality characteristics it is possible to manufacture a Chinese egg noodle with good physical attributes.     

Comparison of different rice flour- and wheat flour-based butter cookies for acrylamide formation

Acrylamide (AcA) contents of different rice flour- and wheat flour-based butter cookies baked at 130 °C for 20, 55, or 90 min were investigated. AcA contents of different flour-based cookies increased with baking time. Color parameters in terms of CIE L*, b*, C*, and ΔE values showed significant opposite correlation to the AcA formation in each of the raw flour cookie. The cookies based on white rice flour had the lowest AcA contents ranging from not detectable (ND) to 204 μg/kg, followed by cookies based on brown rice flour (ND to 450 μg/kg), white wheat flour (155 μg/kg to 661 μg/kg), and whole wheat flour (306 μg/kg to 982 μg/kg). Considerably lower AcA levels were found in the rice flour-based cookies than in the wheat flour-based cookies, as well as in the milled flour-based cookies than in the whole-grain cookies. Although the flour source was considered to play a primary role in determining the AcA content, AcA content was apparently not dependent on the quantities of reducing sugars and free asparagine in the starting raw flour and cookies during baking. In summary, given its reducing potential for AcA formation, rice flour could be used in the production of cookies safe from heat-induced contaminants.     

Effect of extrusion cooking of sorghum flour on rheology,morphology and heating rate of sorghum–wheat composite dough

Addition of a gluten-free flour such as sorghum has negative impact on the quality of wheat dough for bread making. One of the methods which can be used to promote the quality of sorghum-wheat composite dough is to extrude the sorghum flour before incorporation. In this regard, to produce a dough with appropriate bakery properties sorghum flour was extruded at 110 °C and 160 °C die temperature with 10%, 14% and 18% feed moisture. The effect of extruded sorghum flour incorporation (10%) on rheological (farinography and stress relaxation behavior), morphological and temperature profile of sorghum-wheat composite dough were evaluated. Extrusion cooking altered the sorghum-wheat composite dough properties through partial gelatinization of starch granules. Addition of extruded sorghum flour increased the water absorption and dough development time but it decreased the dough stability. Native sorghum-wheat composite dough showed viscoelastic liquid-like behavior whereas addition of sorghum flour extrudate changed dough to a more viscoelastic solid-like structure. Maxwell model was more appropriate than Peleg model to describe the viscoelasticity of the sorghum-wheat composite dough. Extrusion cooking decreased composite dough elasticity and viscosity. Sorghum extrudate increased the heating rate of composite dough crumb during baking. Addition of extruded sorghum flour formed a non-uniform and less compact dough structure. As a result, dough containing extruded sorghum flour had a good potential for producing a high-yielding bread in a short time of baking.     

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.     

Acceptability of wheat-sorghum composite flour products: An assessment

The acceptability of sorghum as human food has been a problem in Tanzania even in regions showing promising potential for its production and utilization. Reasons given for low acceptability of sorghum products as human foods include unpleasant colour, aroma, mouthfeel, taste, unpleasant aftertaste and stomachfeel. An acceptability test of selected sorghum products was, therefore, conducted in the Department of Food Science and Technology, Sokoine University of Agriculture, Morogoro, Tanzania. The objective of the test was to determine consumers' preference for the following wheat-sorghum composite flour products: bread and buns or maandazi. The products were prepared using sorghum flour composited with wheat flour in the following proportions: 100% brown sorghum flour (standard products); and 80:20%; 60:40%; 40:60% and 20:80% for wheat/sorghum (white and brown) composite flours. Results indicated that in the case of composite flour bread, preference for the product improved as the amount of sorghum flour decreased. In the case of buns or maandazi the 100% sorghum flour products of both white and brown were equally preferred. Buns prepared from 100% sorghum flour of white and brown varieties showed promising potential in the improvement of the acceptability of sorghum products. Taking advantage of such products, especially in villages, could enhance sorghum utilization in rural communities.     

戊二醛改性提高大豆胶粘剂耐水性能

以脱脂大豆粉(SF)为原料,选用十二烷基硫酸钠(SDS)和戊二醛(GA)作为改性试剂,制备出具有较好耐水性能的木材用胶粘剂,并应用于杨木胶合板,分别研究了pH值、戊二醛用量、反应时间以及最终改性胶粘剂贮存时间对耐水胶合性能及表观粘度的影响,并采用十二烷基硫酸钠.聚丙烯酰胺凝胶电泳(SDS-PAGE)和傅屯叶变换红外光谱(FT-IR)分析手段探讨了改性胶粘剂耐水性能增强机理.结果表明:较佳合成工艺为:pH值为12.0,GA添加量0.80wt%(基于脱脂豆粉质量),反应时间1.0 h,反应温度30.0℃.按照GB/T 9846-2004胶合板中Ⅱ类板标准检测,耐水胶合强度可达0.68MPa.SDS-PAGE谱图说明蛋白质分子间形成化学键交联,FT-IR分析表明有环状吡啶结构生成,这些可能是改性胶粘剂耐水性能提高的原因.     

酒石酸酰化改性制备低固体含量大豆蛋白胶黏剂的研究

以L-酒石酸和乙酰氯在极少量磷酸做催化剂的条件下制备二乙酰基酒石酸,之后将二乙酰基酒石酸溶于乙醇中制备改性剂,加入到制备好的p H10.50~10.90低浓度大豆分离蛋白预处理液中,制备胶黏剂。测试胶黏剂的固体物含量、DSC、胶合强度以及胶黏剂横切面。结果表明:p H10.7~10.8时,200 m L大豆分离蛋白预处理液中加入0.4 g二乙酰基酒石酸和10 m L无水乙醇制备的改性剂,最终得到的胶黏剂有良好的耐水性,胶合强度2 MPa,远超过国家对Ⅱ类胶合板胶合强度的要求(≥0.7 MPa)。     

Carotenoid bioaccessibility from whole grain and decorticated yellow endosperm sorghum porridge

Sorghum is a staple crop and a potential dietary source of carotenoids in semi-arid regions of Africa, but information on the bioavailability of these pigments is limited. This study aimed at exploring the effects of agronomic manipulation on sorghum carotenoid contents at selected stages of kernel development and maturation and assessing carotenoid bioaccessibility from matured yellow-endosperm sorghum varieties (P88 and P1222), by comparing porridge made from sorghum whole and decorticated milled grains. Carotenoid content of sorghum milled fractions ranged from 2.90 to 7.22 mg/kg in P88 unbagged decorticated flour, at 50 and 30 days after half bloom (DAHB) respectively, to 9.87-13.69 mg/kg in bagged decorticated bran fractions in P88, at 50 and 30 DAHB respectively. Maize milled fractions were significantly (P < 0.05) higher in carotenoid content than all sorghum products. Bagging increased sorghum carotenoid content by 8-184% vs. unbagged panicles. Carotenoid bioaccessibility was generally higher from sorghum (63-81%) compared to maize (45-47%). Micellarization of xanthophylls (75%) was more efficient than carotenes (52%) in sorghum, while they were similar in maize (40-49%). These results suggest that the higher bioaccessibility of sorghum carotenoids combined with efforts to enhance sorghum carotenoid content may allow for sorghum to provide similar levels of bioaccessible carotenoid pigments as common yellow maize.     

Grain of high digestible,high lysine (HDHL) sorghum contains kafirins which enhance the protein network of composite dough and bread

The aim of this study was to determine whether protein body-free kafirins in high digestibility, high-lysine (HDHL) sorghum flour can participate as viscoelastic proteins in sorghum-wheat composite dough and bread. Dough extensibility tests revealed that maximum resistance to extension (g) and time to dough breakage (sec) at 35 °C for HDHL sorghum-wheat composite doughs were substantially greater (p < 0.01) than for normal sorghum-wheat composite doughs at 30 and 60% substitution levels. Functional changes in HDHL kafirin occurred upon exceeding its T_g. Normal sorghum showed a clear decrease in strain hardening at 60% substitution, whereas HDHL sorghum maintained a level similar to wheat dough. Significantly higher loaf volumes resulted for HDHL sorghum-wheat composites compared to normal sorghum-wheat composites at substitution levels above 30% and up to 56%, with the largest difference at 42%. HDHL sorghum-wheat composite bread exhibited lower hardness values, lower compressibility and higher springiness than normal sorghum-wheat composite bread. Finally, HDHL sorghum flour mixed with 18% vital wheat gluten produced viscoelastic dough while normal sorghum did not. These results clearly show that kafirin in HDHL sorghum flour contributes to the formation of an improved protein network with viscoelastic properties that leads to better quality composite doughs and breads.     

Sweet sorghum productivity for biofuels under increased soil salinity and reduced irrigation

Sweet sorghum (Sorghum bicolor (L.) Moench.) is a drought-tolerant crop with high resistance to saline-alkaline soils, and sweet sorghum may serve as an alternative summer crop for biofuel production in areas where irrigation water is limited. A two-year study was conducted in Northern Greece to assess the productivity (biomass, juice, total sugar and theoretical ethanol yields) of four sweet sorghum cultivars (Sugar graze, M-81E, Urja and Topper-76-6), one grain sorghum cultivar (KN-300) and one grass sorghum cultivar (Susu) grown in intermediate (3.2 dS m⁻¹) or in high (6.9 dS m⁻¹) soil salinity with either low (120 mm) or intermediate (210 mm) irrigation water supply (supplemented with 142–261 mm of rainfall during growth). The soil salinity and irrigation water supply effects on the sorghum chlorophyll content index, photosystem II quantum yield, stomatal conductance and leaf K/Na ratio were also determined. The sorghum emergence averaged 75,083 plants ha⁻¹ and 59,917 plants ha⁻¹ in a soil salinity of 3.2 dS m⁻¹ and 6.9 dS m⁻¹, respectively. The most affected cultivar, as averaged across the two soil salinity levels, was the Susu grass sorghum emerging at 53,250 plants ha⁻¹, followed by the Topper-76-6 sweet sorghum emerging at 61,250 plants ha⁻¹. The leaf K/Na ratio decreased with decreasing irrigation water supply, in most cases, but it was not significantly affected by soil salinity. The dry biomass, juice and total sugar yields of sorghum that received 210 mm of irrigation water was 49–88% greater than the yields of sorghum that received the 120 mm of irrigation water. Sorghum plants grown in a soil salinity of 3.2 dS m⁻¹ produced 42–58% greater dry biomass, juice and total sugar yields than the yields of sorghum plants grown in a soil salinity of 6.9 dS m⁻¹. The greatest theoretical ethanol yield was produced by sweet sorghum plants grown in a soil salinity of 3.2 dS m⁻¹ with 210 mm of irrigation water (6130 L ha⁻¹, as averaged across cultivar), and the Urja and Sugar graze cultivars produced the most ethanol (7620 L ha⁻¹ and 6528 L ha⁻¹, respectively). Conclusively, sweet sorghum provided sufficient juice, total sugar and ethanol yields in fields with a soil salinity of 3.2 dS m⁻¹, even if the plants received 50–75% of the irrigation water typically applied to sorghum.     

Effect of suppressing the synthesis of different kafirin sub-classes on grain endosperm texture, protein body structure and protein nutritional quality in improved sorghum lines

To improve sorghum grain protein nutritional quality, improved sorghum lines were transformed to suppress the synthesis of different kafirin sub-classes, or backcrossed into transgenic lines with improved protein quality. Co-suppression of the alpha-, gamma- and delta-kafirin sub-classes and removal of the tannin trait resulted in transgenic sorghum lines with high cooked protein digestibility (±80%), improved Amino Acid Score (0.8) and Protein Digestibility Corrected Amino Acid Score (0.7) compared to the non-transgenic null controls (±50%, 0.4 and 0.2, respectively). These high protein quality lines had a floury endosperm. They also had modified protein body structure, where the protein bodies were irregular shaped with few to numerous invaginations and were less densely packed, with a dense protein matrix visible around the protein bodies. When fewer sub-classes were suppressed, i.e. gamma 1 and delta 2, the endosperm was corneous with normal protein body structure but the improvement in cooked protein digestibility appeared to be less. Apparently, co-suppression of several kafirin sub-classes is required to obtain high protein nutritional quality sorghum lines, but this seems to result in floury-type grain endosperm texture.     

Properties of field-sprouted sorghum and its performance in ethanol production

The objective of this research was to investigate physicochemical and biochemical characteristics of field-sprouted grain sorghum and its fermentation performance in ethanol production. Five field-sprouted grain sorghum varieties, which received abnormally high rainfall during harvest, were used in this study. Enzyme activities, microstructure, flour pasting properties, kernel hardness, kernel weight, kernel size, flour size and particle distribution of field-sprouted grain sorghum were analyzed. The effect of germination (i.e., sprouting) on conversion of grain sorghum to ethanol was determined by using a laboratory dry-grind ethanol fermentation procedure. Sprouted sorghum had increased α-amylase activity; degraded starch granules and endosperm cell walls; decreased kernel hardness, kernel weight, kernel size, and particle size; and decreased pasting temperature and peak and final viscosities compared with non-sprouted grain sorghum. The major finding is that the time required for sprouted sorghum to complete fermentation was only about half that of non-sprouted sorghum. Also, ethanol yield from sprouted sorghum was higher (416–423 L/ton) than that from non-sprouted sorghum (409 L/ton) on a 14% moisture basis.     

Sorghum extrusion process combined with biofortified sweet potato contributed for high iron bioavailability in Wistar rats

This study aimed to evaluate the effect of sorghum and sweet potato on the bioavailability of iron, gene expression of proteins involved in iron metabolism and the plasma antioxidant capacity in animals fed with whole sorghum grains processed by dry heat or extrusion, combined or not with sweet potato flour with high content of carotenoids. Five experimental groups were tested (n = 7): dry heat sorghum flour (DS); extruded sorghum flour (ES); whole sorghum flour + sweet potato flour (DS + SP); extruded sorghum flour + sweet potato flour (ES + SP) and positive control (FS). The evaluations included: hemoglobin gain, hemoglobin regeneration efficiency, gene expression of divalente metal transporter 1 (DMT-1), duodenal citochroma B (DcytB), ferroportin, hephaestin, transferrin and ferritin and total plasma antioxidant capacity (TAC). The ES + SP group showed higher (p < 0.05) expression of DcytB, ferroportin and hephaestin when compared to the control group. The DS group showed high (p < 0.05) expression of DMT-1 and the ES showed high mRNA expression of transferrin and ferritin. The changes in the sorghum physicochemical properties from extrusion process reduced the iron and phytate content, and increased the gene expression of proteins involved in iron metabolism, improving iron bioavailability. The combination of sweet potato and sorghum flour (dry or extruded) improved the iron capture and total antioxidant capacity, probably due to the presence of β-carotene and antioxidant compounds.     

Fractionation and characterization of teff proteins

The protein fractions in three different teff types were studied in comparison to sorghum to explain teff’s superior bread making quality. The proportion of aqueous alcohol-soluble teff protein was approx 40% and it was rich in glutamine and leucine. Hence, contrary to previous reports, prolamin is the major teff grain storage protein. With SDS-PAGE under non-reducing and reducing conditions, teff prolamins showed broad bands at approx. 20.3 and 22.8 kDa. Other bands were at approx. 36.1, 50.2, 66.2 and 90.0 kDa, respectively under non-reducing conditions, but were absent under reducing conditions, indicating that these polypeptides are disulphide bonded. The presence of broad monomeric prolamin bands in teff under non-reducing conditions indicates that teff prolamin is less polymerized than sorghum prolamin. Estimated free energy of hydration of teff prolamins was −161.3 kcal/mol compared to −139.8 kcal/mol for sorghum prolamin. By 2-D electrophoresis, teff protein contained more polypeptides than maize or sorghum. Teff contained a higher proportion of basic polypeptides than maize. With differential scanning calorimetry, teff prolamin exhibited a single endothermic peak at 69.85 °C, while no peak was detected for sorghum prolamin. The lower polymerization, hydrophobicity and denaturation temperature of teff prolamins probably make them somewhat functional in bread making.     

Effect of fermentation on sorghum protein fractions and in vitro protein digestibility

Changes in pH, titratable acidity, total soluble solids and proteins ofDabar sorghum (Sorghum bicolor (Linn) Moench.) during naturalfermentation at 37 ^°C for up to 36 h were monitored. The pH ofthe fermenting material decreased sharply with a concomitant increase in the titratable acidity. Total soluble solids increased with progressivefermentation time. The crude protein and non-protein nitrogen slightlyincreased during the last stages of fermentation. The in vitroprotein digestibility markedly increased as a result of fermentation.The globulin plus albumin fractions increased significantly (p 0.05)during the first 8 h of fermentation. Kaffirin fraction decreasedduring the first 8 h of fermentation but increased sharply as fermentationprogressed. Cross-linked kaffirins fluctuated during the fermentationprocess. Glutelin like protein, which was the minor fraction, trueglutelins, the second most abundant fraction, together with non-extractableproteins fluctuated during the fermentation process.     

Preparation and properties of flours and protein concentrates from raw, fermented and germinated fluted pumpkin (Telfairia occidentalis Hook) seeds

In vitro protein digestibility, chemical composition and selected functional properties of flours and protein concentrates prepared from raw, fermented and germinated fluted pumpkin (Telfairia occidentalis Hook) seeds were studied. Protein concentrates prepared by an alkaline extraction process had increased crude protein contents (61.5–70.8%) compared to flour samples (46.4–52.7%). The yields of protein concentrates ranged from 24.5% to 29.4% while values for protein recoveries varied between 64.8% and 65.2%. Protein concentrates also had increased foam volume and decreased foam stability (100% decrease over a 2 h period), compared to flour samples. Fermentation and germination were observed to significantly (p<0.05) lower polyphenol and phytic acid contents, but increased protein digestibility of fluted pumpkin seed flours and concentrates. Both raw flour and concentrate were significantly (p<0.05) higher in water absorption capacity than germinated or fermented flours and concentrates. Protein concentrates had comparatively better fat absorption properties than the flour samples. Hence protein concentrates may prove to have useful applications in ground meat formulations.     

Physical and nutritional qualities of extruded weaning foods containing sorghum,pearl millet,or finger millet blended with mung beans and nonfat dried milk

Sorghum, pearl millet, and finger millet flours (60% of each) were blended with toasted mung bean flour (30%) and nonfat dry milk (10%) and extruded (Brabender single screw) to make precooked, ready-to-eat, weaning foods. The extruded foods had high cold paste viscosity, but their cooked paste viscosity was lower than that of the respective blends. Chemical scores of the extruded foods were 78 for sorghum, 80 for pearl millet, and 96 for finger millet. Protein digstibility corrected amino acid scores (PD-CAS) were similar for pearl millet (68%) and finger millet (69%); PD-CAS for sorghum was 57%. Total dietary fiber content of the foods ranged from 7.6 to 10.1%, with the soluble dietary fiber content of the foods being about 10% higher than that of the corresponding blends. Extrusion enhanced the in vitro protein digestibility of foods, but no marked difference occurred in the in vitro carbohydrate digestibility among the unprocessed blends and the extruded foods. The net protein ratio, protein efficiency ratio, and biological values were higher for the finger millet food than for the pearl millet food, probably because of the higher lysine content of the finger millet protein.Contribution No. 95-253-J of the Kansas Agricultural Experiment Station.