Acceptability and keeping quality of soymilk in Tanzania

Acceptability and keeping quality of two soymilk samples produced by hot water grinding and by presoaking in NaHCO₃ was determined in Morogoro town. In terms of flavour and taste the two samples were significantly different from cow's milk (p<0.05) but when vanilla was added (0.5 ml/l) the two samples were not significantly different from cow's milk. As estimated by using pH, titratable acidity and standard Plate Count, the milk samples could be kept at room temperature (25±2 °C) for up to 12 hours. To destroy 99% of the trypsin inhibitors in the soymilk samples, 45 minutes at 98 °C were needed for the alkaline presoaked milk while 75 minutes were needed for the plain water presoaked soymilk.     

Evaluation of sorghum flour as extender in plywood adhesives for sprayline coaters or foam extrusion

This study was conducted to evaluate sorghum flour as protein extender in phenol-formaldehyde-based plywood adhesive for sprayline coaters or foam extrusion. Defatted sorghum flour, containing 0.2% (db) residual oil and 12.0% (db) crude protein, was analyzed for solubility and foaming properties. Sorghum flour proteins were least soluble (≤12%) under acidic pH, most soluble (72%) at pH 10, and produced substantial and highly stable foam at pH 10. Sorghum flour was substituted (on protein content basis) for wheat flour in the standard glue mix. Mixing properties and bond strength of the sorghum-based glue were compared with those of the industry standard glue. The sorghum flour-based adhesive had mixing properties and appearance that were superior to those of the standard wheat flour-based plywood glue, but its viscosity and bond strength were markedly less. Doubling the amount of protein contributed by sorghum flour in the glue mix markedly improved both viscosity (1104 cP) and adhesion strength (1.37 MPa) of the sorghum-based plywood glue to acceptable levels. The modified sorghum flour-based plywood glue also produced foam that remained stable up to 3 h. These results demonstrated that sorghum flour is a viable extender in plywood glues for sprayline coater or foam extrusion.     

Quinoa flour in baked products

The performance of quinoa-wheat flour blends (5/95, 10/90, 20/80, 30/70) were evaluated in breads, cakes and cookies. Breads baked with 5% and 10% quinoa flour were of good quality. Loaf volume decreased, crumb grain became more open and the texture slightly harsh at higher usage levels of quinoa flour. A bitter aftertaste was noted at the 30% level. Cake quality was acceptable with 5% and 10% of quinoa flour. Cake grain became more open and the texture less silky as the level of quinoa substitution increased. Cake taste improved with either 5% or 10% quinoa flour in the blend. Cookie spread and top grain scores decreased with increasing levels of quinoa flour blended with high-spread cookie flour. Flavor improved up to 20% quinoa flour in the blend. Cookie spread and cookie appearance was improved with a quinoa/low-spread flour blend by using 2% lecithin.     

Quality attributes of fermented yam flour supplemented with processed soy flour

Pretreated soy flour was used to replace 10, 20, 30 and 40% of fermented yam flour as a protein supplement. The effect of the supplementation on the physicochemical and sensory properties of amala, a popular West African food made from rehydrated yam flour, was investigated. Blanching (10 min in boiling water) and subsequent fermentation (24 h) as pretreatment methods produced flour that was lighter in color than the unfermented samples. Protein content of the yam-soy mixture increased from 3.5% in the control to 19.7% for 40% soy fortification. Water binding capacity increased from 212.6 g/100 g for the yam flour control to 257.3 g/100 g for the blend with 40% soy flour. However, swelling capacity and solubility were adversely affected with increased soy flour addition as dough became sticky and soft. There was no significant difference in color, taste, flavor or overall acceptability when compared with the control up to 20% soy substitution. Dough with 20% soy flour is a possibility for increasing the protein content of yam flour in human feeding.     

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.     

Antiradical properties of sorghum (Sorghum bicolor L. Moench) flour extracts

Epidemiological studies support the belief that whole grains are protective against several chronic diseases. The health benefits of whole grains are attributed in part to their unique phytochemical composition. Major phytochemicals in grains include various classes of phenolic compounds, flavonoids and coumarin derivatives, etc. Phenolic compounds present in grains possess antioxidant properties that are associated with the health benefits of grains and grain products. Sorghum is one of the main staple cereal grains in hot dry tropics and ranks fifth among cereal crops in the world. Although sorghum is rich in phenolics and tannins which are proven anticancer and cardioprotective constituents, human consumption of sorghum is limited. To our knowledge, there is limited literature on the profile of antioxidant phytochemicals in the local white variety of sorghum. Hence, the objective of this study was to investigate the antioxidant property of white sorghum flour extracts in vitro and also to identify the fractions responsible for the antioxidant activity. In the present study, we analyzed the antioxidative properties of various extracts (water, 60% methanol, 60% ethanol, and 60% t-butanol) of white sorghum flour employing the 1,1-diphenyl-2-picrylhydrazyl (DPPH) model system. Phenolics, antiradical and antioxidant activities were also examined in chromatographic sub-fractions of the soxhlet methanolic extract. Our results indicated that the various extracts exhibited significant antioxidant activity that did not correlate with the phenolic content. Further, two sub-fractions eluted with methanol and acetone/methanol were found to possess strong antioxidant activity in two assay systems. Our results suggest that a diet rich in sorghum may be useful in combating diseases in which free radical production plays a key role.     

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.     

Dynamics of phytate-zinc balance of fungi fermented cassava products (gari and flour)

Parsley is one of the medicinal herbs used by diabetics in Turkey. It has been reported to reduce blood glucose levels. In this study the effects of feeding parsley on diabetes-induced free radical mediated injury in rat aorta and heart tissues were investigated. Swiss albino rats were divided into six groups: Control, diabetic, parsley, diabetic + parsley, glibornurid, and diabetic + glibornurid. Rats were subjected to i.p. streptozotocin (STZ, 65 mg/kg) to induce diabetes. On the fourteenth day of the study, either parsley (2 g/kg) or glibornurid (5 mg/kg) were given for 28 days to the diabetic rats. Aorta and heart tissue lipid peroxidation and glutathione levels as well as blood glucose levels were determined. The results of the present study indicate that lipid peroxidation was increased and glutathione levels were decreased in both aorta and heart tissue of the diabetic rats. However, treatment of the diabetic rats with either parsley or glibornurid reversed the effects of diabetes on blood glucose, and tissue lipid peroxidation and glutathione levels.     

Effects of infrared heating on phenolic compounds and Maillard reaction products in maize flour

Maize grains were heated by infrared radiation for 50–100 s, than flaked and milled. The output was set to 110, 115, 120 and 140 °C to determine the effect of temperature on the formation of acrylamide, 5-hydroxymethylfurfural (HMF) and furosine, as well as the level of phenolic compounds in maize flour and its total antioxidant capacity (TAC). Acrylamide and HMF levels were increased as the load of the heat treatment was increased in grains, while furosine concentration was rapidly increased to an apparent maximum (34.96 μg/g) followed by decrease during heating. Acrylamide, as well as HMF variables correlated very well with TAC of heat-treated flour (r² = 0.98 and 0.86). The process of infrared heating had a great influence on the reduction of phenolic compound contents. However, new antioxidants that were formed as a result of the Maillard reaction increased the total antioxidant capacity of heat-treated maize flour.     

Tannic acid content in sorghum (Sorghum bicolour M.): Effects of processing

Some simple treatments were employed to reduce the tannin content in locally consumed sorghum grain. The treatments included overnight soaking of sorghum in 2% NaHCO₃, soaking in different alkalis, ammoniation and autoclaving. Of the above treatments, ammoniation was best for complete removal of tannins. Soaking the seeds in alkalis was also effective. Soaking the sorghum seeds for 18 hours in mixed salt solution (containing 1.5% NaHCO₃+0.5% Na₂CO₃ and 0.75% citric acid in w/v ratio) was also found to be effective.     

Use of peanut and cowpea in wheat-based products containing composite flours

Cowpeas and peanuts are legumes of major dietary and economic importance. They are favored worldwide because of their palatability, contribution to nutritional status, and low cost as a protein source compared to animal protein. Flours processed from cowpeas and peanuts have unique physico-chemical and sensory properties when used in composite flour mixtures. Appropriate blends of cowpea and peanut flours to replace wheat flour in Chinese-type noodles, muffins, and tortillas were determined using modelling and optimization procedures. For noodles, 15% peanut flour and 8% cowpea flour supplementation produced an acceptable product with high protein content (21%). For wheat flour replacement in muffins, up to 43% cowpea and up to 44% peanut flours may be used. However, when wheat flour replacement is 50% or greater, cassava flour should comprise 56 to 72% of the blend with a few exceptions. In tortillas, 24% cowpea and 46% peanut flours produced products similar in quality characteristics to those made from 100% wheat flour. The systematic approach used in these studies is more efficient than the traditional substitution method to optimize sensory qualities of wheat-based products containing composite flours.     

Protein and starch digestibilities and mineral availability of products developed from potato,soy and corn flour

A technique for development of potato flour was standardized. Five products viz. cake, biscuit, weaning food, panjiri and ladoo were prepared incorporating potato flour, defatted soy flour and corn flour. Baking and roasting were the major processing techniques employed for the development of these products. Protein, ash and fat contents of potato flour were almost similar to those of raw potatoes. Significant differences in protein, ash and fat contents of all the products were observed. Protein and starch digestibility of potato flour was significantly higher than that of raw potatoes. Protein digestibility increased by 12 to 17 percent on baking or roasting of products. Processed products had significantly higher starch digestibility and mineral availability compared to raw products. Thus, it can be concluded that roasting and baking are effective means of improving starch and protein digestibility and mineral availability of products.     

Tannins in utilization of sorghum grains in Burkina Faso

The study of thirty sorghum varieties used for food in Burkina Faso showed a relationship between tannin level and utilization of sorghum grain. High tannin level varieties (more than 0.2%) are generally used for local alcoholic drink, instead low tannin level varieties (under 0.2%) are used for cooking and for non fermented drinks.     

Effect of barley and oat flour types and sourdoughs on dough rheology and bread quality of composite wheat bread

The potential of sourdough to improve bread quality of barley and oat enriched wheat breads may depend on the characteristics of the added flour (cereal type, variety, extraction rate). We compared the effect of different barley flours and oat bran (substitution level 40%), unfermented and as sourdoughs (20% of total flour), on composite wheat dough and bread characteristics by combining empirical rheological analyses (DoughLab, SMS/Kieffer Dough and Gluten Extensibility Rig) with small-scale baking of hearth loaves. Whole grain barley flour sourdough increased resistance to extension (Rmax) of the dough and improved the form ratio of hearth loaves compared to unfermented whole grain barley flour. However, sourdough showed little effect on the breads prepared with sifted barley flour or oat bran. The breads made with oat bran showed highest bread volume, lowest crumb firmness and highest β-glucan calcofluor weight average molecular weight (MW). The heat treatment of oat bran inactivated endogenous enzymes resulting in less β-glucan degradation. High MW β-glucans will increase the viscosity of the doughs water phase, which in turn may stabilise gas cells and may therefore be the reason for the higher bread volume of the oat bran breads observed in our study.     

The fermentation of trahanas: a milk-wheat flour combination

The fermented food, trahanas (a milk-wheat flour combination prepared in Greece), was studied to determine the microbiological and chemical changes that occur during fermentation. It is a lactic acid bacterial fermentation in whichStreptococcus lactis, Streptococcus diacetylactis, Leuconostoc cremoris, Lactobacillus lactis, Lactobacillus casei, Lactobacillus bulgaricus andLactobacillus acidophilus play the major acid- and aroma-producing role. The whole fermentation lasts about 50 hours. The pH of the final dried trahanas was 4.07–4.75, the acidity 0.60–1.00%, the moisture content 8.6–11.5% and the protein content 10.4–13.6%. The product offers possibilities as an increased nutritive value or high-protein food.     

Fermentation of pearl millet flour with yeasts and lactobacilli:in vitro digestibility and utilisation of fermented flour for weaning mixtures

Single as well as mixed culture fermentations by yeasts (S. diastaticus;S. cerevistiae) and lactobacilli (L. brevis;L. fermentum) at 30 °C for 72 h improved the starch and protein digestibility (in vitro) of pearl millet flour significantly. The flour fermented bySaccharomyces diastaticus, a starch hydrolysing yeast, had the highest starch digestibility whereas fermentation bySaccharomyces cerevisiae enhanced the in vitro protein digestibility of the flour significantly. Weaning mixtures prepared from the fermented flour were also found to be organoleptically acceptable.     

Studies on the baking properties of wheat: Pigeonpea flour blends

Pigeonpea flour was substituted at levels of 0, 5, 10, 15,20, 25% to wheat flour and whole wheat meal for bread andChapatti making, respectively. Blends were prepared up to50% for cookie making. Increasing levels of pigeonpeas inthe blends significantly increased the protein and mineralcontent of the baked products. The bread from 10%pigeonpea flour blend with 2–3% vital gluten and 0.5%SSL had high loaf volume and loaf quality. Blends containing 15% pigeonpea flour were acceptable for Chapatti and 30% pigeonpea flour with 0.25% SSL wereacceptable for cookie making.     

Particle size heterogeneity in milled barley and sorghum grains: Effects on physico-chemical properties and starch digestibility

The average particle size of ground grains is known to influence properties related to processing (e.g. water absorption and solubility) and nutritional value (e.g. starch digestion rate) of human foods and animal feeds. The purpose of this study was to identify the contributions made by individual size fractions of hammer-milled barley and sorghum grains to average bulk compositional, hydration, rheological, and enzyme susceptibility properties. Barley and sorghum grains were each hammer-milled through a 4 mm screen and subsequently fractionated on a set of eight sieves ranging from 0.125 mm to 2.8 mm. Individual fractions were characterised for (1) starch, aNDF, and water content, (2) water absorption index (WAI) and water solubility index (WSI), (3) viscosity profile during cooking and cooling in excess water, and (4) in vitro starch digestibility. Weighted average values based on fraction yields and property values for WAI, WSI, and starch digestibility were not significantly different from values obtained for non-fractionated ground grains of both barley and sorghum. Glucose yields from starch digestion varied about ten-fold between the smallest and largest particle fractions, and WAI and WSI had value ranges of 1.9–2.8 g/g (sorghum), 2.1–4.0 g/g (barley) and 1.3–4.5% (sorghum), 0.7–10.3% (barley), respectively. Viscosity profiles for milled sorghum grain fractions were dominated by starch swelling which became increasingly restricted as particle sizes increased. Viscosity profiles for milled barley grain fractions did not exhibit typical starch-based behaviour and were most likely dominated by soluble fibres. Taken together, the results show that there is considerable potential for designing combinations of hydration, rheological and digestibility properties of ground grains through informed selection of appropriate grains and particle size distributions.     

The nutritive quality of maize-soybean (70:30) tempe flour

The nutritive quality of maize-soybean (70:30) tempe flour manufactured by fermentation withRhizopus oligosporus: Rhizopus orysae (1:1) was determined using weanling rats. Mould fermentation of maize-soybean mixture did not significantly affect its proximate composition. It increased the content of reducing sugars, total acids and aminonitrogen by about 43, 195 and 482 percent, respectively, and decreased phytate content by 46 percent. In vitro iron absorption for maize flour and maize-soybean tempe flour was 2.46 and 5.51 percent, respectively. Protein Efficiency Ratio (PER) and Net Protein Ratio (NPR) for maize-soybean tempe flour and skim-milk diets were 2.71 and 2.96, respectively, for PER, and 3.31 and 3.51, respectively, for NPR. In vivo protein digestibility of the two products was 95.0 and 98.0 percent, respectively.     

Preferential binding of sorghum tannins with γ-kafirin and the influence of tannin binding on kafirin digestibility and biodegradation

Kafirins, sorghum prolamins bind with sorghum condensed tannins (CTs). The binding of different kafirin species with sorghum CTs was investigated. Analysis by chemical assay and by sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE), reversed-phase high-performance liquid chromatography (RP-HPLC), and free zone capillary electrophoresis (FZCE), showed that γ-kafirin bound more CTs than the other kafirin species. SDS–PAGE suggested that the γ-kafirin-bound tannins were in the form of aggregates of molecular size >200k. RP-HPLC and FZCE revealed that sample preparation and drying the kafirins prior to the binding assays had a significant impact on γ-kafirin solubility. The effect of tannin binding on kafirin and kafirin film digestibility and film biodegradation was determined. Kafirins bound to tannins had lower digestibilities than unbound kafirins. Films made from tannin-bound kafirin had much lower digestibility and were less biodegradable than films made from unbound kafirin. The increase in kafirin film life by tannin modification appears to be due to a decrease in protein digestibility caused by kafirin–tannin binding. These findings suggest that γ-kafirin content in sorghum may be manipulated to either reduce or increase tannin binding in order to change the functionality of the kafirin in food, feed or film applications.