Biological evaluation of pearl millet protein: effect of different treatments and storage

Whole grain flour of one variety (HC-4) of pearl millet (Pennisetum americanum L. Leeke) after giving different treatments (defatting, butylated hydroxyanisole, ascorbic acid and thermal) was stored in earthen pots at prevailing room temperature (28–34°C) and relative humidity (70–80%) for 30 days. The flour samples were evaluated for protein quality using rats. Storage of flour for 30 days markedly reduced the protein quality. The values of protein efficiency ratio, true digestibility, biological value, net protein retention and net protein utilisation were significantly (P<0.05) higher in fresh and treated flour than untreated flour. Among treated flours, defatted flour showed best growth followed by butylated hydroxyanisole, thermal and ascorbic acid treated flour.     

Biological utilisation of pearl millet fluor fermented with yeasts and lactobacilli

Mixed culture fermentation of pearl millet flour withSaccharomyces diastaticus, Saccharomyces cerevisiae, Lactobacillus brevis andLactobacillus fermentum brought about an improvement in its biological utilisation in rats. Protein efficiency ratio, feed efficiency ratio, apparent protein digestibility, true protein digestibility, net protein utilisation, net protein retention, protein retention efficiency and utilisable protein values in case of pure culture fermented pearl millet four were higher than the control. Feeding of the fermented products did not bring about physiological, histopathological and haematological changes in rats.Chapaties and cutlets prepared from the fermented products were organoleptically acceptable.     

Effect of treatment on composition and protein and energy utilization of rice and mung bean by rats

Yellow rice derived from stack-burned unthreshed grains had lower lysine content than white milled rice. Stack burning did not affect energy digestibility in growing rats but decreased true nitrogen digestibility and net protein utilization (NPU). Increasing parboiling time from 20 to 60 min had no adverse effect on energy and protein utilization of parboiled milled rice. Defatting of rice bran-polish with petroleum ether at 50°C had no effect on protein utilization but decreased energy content and utilization. Mechanical dehulling of mung bean (Vigna radiata [L.] Wilczek) reduced fiber content, increased energy and protein digestibility but decreased biological value (BV) and NPU. Toasting and winnowing the bean reduced lysine content, improved digestible energy but decreased BV and NPU. Cooking the bean preparations improved the biological value only in mechanically dehulled bean with resultant higher NPU than that of whole bean.     

Nutrient composition and protein quality of minor millets

Nutrient composition of five minor millets produced and consumed in dry land regions and tribal areas of Andhra Pradesh, India, was evaluated. The millets analysed were Italian millet (Setaria Italica), French millet (Panicum miliaceum), Barnyard millet (Echinachloa colona), Kodo millet (Paspalum scrobiculatum) and little millet (Panicum miliare). The nutrients analysed were proximate principles, amino acids, fibre components, calcium, Phosphorus and Iron. Protein and energy were evaluated by true digestability (TD), biological value (BV), net protein utilization (NPU) and digestible energy (DE) in rats. The protein content was higher and lysine content lower, when compared to major millets. Dehusked millets had lower total dietary fibre (TDF) and tannin. The TD of protein ranged between 95.0 to 99.3, whereas the BV was between 48.3 and 56.5. All the millets were poor sources of calcium, phosphorus and iron, with the exception of french millet.     

Protein,energy and mineral utilization in rats fed rice-legume diets

Protein, energy and mineral utilization were examined in growing rats fed cooked, dry legume seeds in combination with polished rice. The legumes tested included 3 varieties of common beans, black, white and brown (Phaseolus vulgaris), lentils (Lens esculenta) and peas (Pisum sativum). The rice:legume mixtures (1:1 N ratio) were the only dietary sources of protein, Zn, Fe and Cu. The rice:black bean mixture was also tested at a 4:1 N ratio. Nutrient utilization was studied by balance trials and mineral utilization was further assessed by tissue analyses. True protein digestibility (TD) and energy digestibility of the rice:legume (1:1) mixtures were high. Biological value (BV) varied only little but was lowest in the rice:lentil mixture. The rice:brown bean mixture had the lowest amount of utilizable protein (UP). The (1:1) rice:legume mixtures did not adversely affect Fe status, as measured by liver Fe content and blood hemoglobin and hematocrit, or Cu status, as measured by liver Cu content and plasma ceruloplasmin. However, femur zinc content indicated a sub-optimal Zn status. Increasing the dietary N from rice in combination with black beans resulted in a substantial improvement of BV, NPU and Zn status of the animals but had a negative effect on UP and Fe status of the rats.     

Biological evaluation of protein quality of sorghum as affected by insect infestation

Protein quality of sorghum grains having 25, 50 and 75% infestation caused by mixed population ofTrogoderma granarium Everts andRhizopertha dominica Fabricius was biologically evaluated by rat growth and nitrogen balance studies. Feeding of diet containing insect infested sorghum grains (50 and 75%) resulted in marked decrease in food intake, protein intake, gain in body weight, food efficiency ratio, protein efficiency ratio, nitrogen consumption, nitrogen absorption, biological value, net protein utilization, dry matter digestibility, net protein retention and protein retention efficiency. These parameters showed negative association with insect infestation levels. However, 25% level of grain infestation did not affect these parameters significantly.     

Effect of heat processing on in vitro protein digestibility and some chemical properties of African breadfruit (Treculia africana Decne) seeds

The effects of dry heat (roasting) and moist heat (boiling) on in vitro protein digestibility, protein fractions and other chemical properties of African breadfruit (Treculia africana Decne) seed that affect their utilization as a source of human food were investigated. Chemical analyses showed that the crude protein and fat contents of the unprocessed (raw) seeds were 20.1% and 13.7%, respectively. The level of phytic acid in the raw seed (1.19 mg/g) was lower than the levels found in some commonly consumed pulses in Nigeria. Albumin and globulin protein fractions were found to be the major seed proteins of African breadfruit seed, constituting 67.8% of the total protein of the raw seed. There were no significant (p<0.05) differences between crude protein, ash and fat contents of the raw and heat processed samples. Boiling proved more effective than roasting for improving protein digestibility and for reducing the levels of trypsin inhibitor, phytic acid and polyphenols of the samples. The complete removal of these antinutrients, however, would require a more severe heat treatment of the seed, which in turn would profoundly reduce the nutritional value and availability of proteins, as demonstrated by the low values obtained for in vitro protein digestibility, protein fractions and protein extractability.     

Protein quality of some Nigerian traditional diets based on the African yambean (Sphenostylis stenocarpa) and pigeon pea (Cajanus cajan)

The protein quality of Nigerian traditional diets based on the African yambean (AYB) and pigeon pea (PP) were performed by in vivo and in vitro bioassays. The individual foods were processed, cooked, dried and mixed to resemble the traditional diets. Weanling male Wistar rats (45–55 g) were used for the bioassay. The rats were fed ad libitum for 35 days of which 28 days were for growth and 7 days for N-balance. All the eleven diets including casein (control) provided 1.6 g N/100 g diet. The parameters tested include PER, growth, N-balance, BV, NPU and apparent digestibility (AD). The rats fed the AYB diets, except AYB: Agidi (Ag), showed superiority in most of the parameters tested. There were significant positive correlations between PER and NPU (r=0.925;p<0.001); PER and AD (r=0.908;p<0.001); PER and body weight gain (r=0.969;p<0.001). The in vitro protein digestibility of the diets was significantly correlated (r=0.80;p<0.01) with the in vivo apparent digestibility. These parameters were used to rank the various diets. Crayfish protein was a better supplement to legume/cereal or legume starchy staple mixtures than leguminous oil seed. However, supplementation of PP: steamed corn (SC) diet with crayfish did not prove beneficial. The result showed that diets based on the African yambean, an under-exploited legume, are nutritious. The need for its reintroduction into the fare of the populace through increased production and appropriate processing technology is stressed. The results of this study can form a base for the standardization of Nigerian diets based on these legumes.     

Biological utilization of vegetable peas: Effect of cooking and varietal differences

The flour of raw as well as cooked vegetable pea cultivars (Arkal and Bonneville) was used for biological evaluation of their protein quality. Cooking did not have a significant influence on the food intake. There were some differences in the food as well as protein intake and gain in body weights of rats when fed uncooked or cooked pea flour diets. Varietal differences did not seem to influence on apparent digestibility, true digestibility, biological value, net protein utilization and utilisable protein but cooking brought a significant (p<0.05) improvement in all of above mentioned parameters. Varietal differences as well as cooking exhibited no influence or serum protein concentration.     

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.     

Sequential fermentation of pearl millet by yeasts and lactobacilli—effect on the antinutrients andin vitro digestibility

Sequential culture fermentation by yeasts (S. diastaticus orS. cerevisiae) at 30°C for 72 hr and then followed by lactobacilli fermentation (L. brevis orL. fermentum) at 30°C for 72 h more resulted in a significant reduction in phytic acid and polyphenol content of pearl millet flour. Fermentation byS. diastaticus andL. brevis combination almost eliminated phytic acid from pearl millet flour. The combinations ofS. diastaticus with both the lactobacilli reduced phytic acid more effectively than those ofS. cerevisiae. The products fermented byS. cerevisiae andL. brevis and byS. diastaticus andL. brevis combinations had the highest protein and starch digestibility (in vitro).     

The protein quality of lupins (Lupinus mutabilis) alone and in combination with other protein sources

The chemical compositions, of raw and treated lupine flour were determined and compared with other plant protein sources. The protein content in the dry matter was 47.7% in untreated seeds ofLupinus mutabilis and about 56% in debittered seeds. The oil-cake contained 65.3% protein. The amino acid analysis showed that lupine protein is characterized by a low level of S-amino acids, the content of which amounts to only 50% of that of the FAO standard reference pattern. The protein quality was measured using the biological tests PER (Protein Efficiency Ratio), NPU (net protein utilization), and BV (biological value) in rats on diets with and without DL-methionine supplementation. PER determinations gave low values for the non-supplemented lupine proteins (1.34, semi-sweet variety; 1.53, water-extracted seeds; 1.19, oil-cake; 3.09, casein), but the PER's were improved by the addition of 0.2% DL-methionine to the diets (3.05, 2.69, 2.81, respectively). Raw as well as processed lupine protein showed an excellent apparent digestibility (80.0–85.8%; casein, 87.1%). The observed NPU and BV values confirmed the importance of methionine supplementation. The true digestibility of 92% was equivalent to that of casein. The complementation effects of mixing lupine protein with proteins from wheat, oat, barley, rice, maize, potato, quinua or fish were investigated by determination of the PER values of the respective mixtures. Feeding lupine protein with cereal proteins resulted in PER values that exceeded by far those of the proteins fed separately (true complementation). This result was not observed for the mixture of potato and lupine. High quality proteins like quinua and fish protein also showed no complementation effect with lupine protein but did improve the quality of the lupine protein to a great extent. The best results could be obtained with combinations of three different plant proteins, in which lupine protein always contributed one third of total protein. These mixtures resulted in PER values equal to those for casein or other animal proteins and may be applied as an economical way to prevent and combat malnutrition.     

The nutritive value of some selected Tanzanian plant food sources

The chemical composition of different varieties of field beans (Vicia faba L.), cowpeas (Vigna unguiculata), groundnuts (Voandzeia subterranea), and sorghum (Sorghum vulgare) were determined. Nutrients analysed in these materials included amino acids, starch, sugar, fibre, minerals and antinutritional factors. All the materials were further tested in balance trials with rats; true protein digestibility (TD), biological value (BV), net protein utilization (NPU) and digestible energy (DE) were evaluated. Based on the chemical analyses as well as on the biological data, the nutritive value of plant materials between species as well as between varieties within species differed considerably. Therefore, more quality evaluation studies along with plant breeding programmes are needed to select the most promising varieties from the nutritional point of view.     

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.     

Chemical composition and protein quality of lentils (Lens) consumed in Egypt

Three local cultivars of lentil (Lens) seeds (Giza 9, Family 91, and Family 195) as well as one imported Pakistani variety were studied. Moisture, protein, fat, carbohydrate, ash, fiber, thiamine, riboflavin, amino acids and some protein fractions were determined on the unpeeled and peeled seeds. The protein quality was evaluated by determining the protein efficiency ratio, net protein utilization, biological value, and true digestibility coefficient. All components were increased by peeling, except the ash, the fiber content, and the residual nitrogen content of the insoluble protein fraction. The latter was markedly decreased by peeling. Giza 9 lentil seeds were found to contain the highest protein and thiamine contents. They showed the highest protein quality and proved to be nutritionally superior to other varieties. Generally, the three local cultivars were found to be chemically and biologically superior to the imported Pakistani cultivar.     

Effect of sesame seed flour on millet biscuit characteristics

Defatted sesame seed flour replaced millet flour at 30, 40, and 50% and was used to prepare biscuits. Protein content of the biscuits was significantly (p 0.05) increased by replacement with sesame seed flour. Millet flour biscuits were heavier than those from the blends. Diameters and weights of biscuits were reduced and thicknesses and spread factors were increased with increasing level of sesame replacement. Sensory evaluation results showed that the biscuits were highly rated for flavor and crispiness but considered poor in color.     

Chemical composition and nutrient digestibility of pearl millet (Pennisetum glaucum) fed to growing pigs

Pearl millet grown at two different locations in the U.S.A., pearl millet A (PMA) and pearl millet B (PMB), were analyzed for chemical composition and nutrient content and compared to corn. The two samples of pearl millet and corn were incorporated into diets and fed to 24 growing pigs in a metabolism trial to determine nitrogen and mineral balance and digestibilities of energy, fat and amino acids. Pearl millet (PMA and PMB) was found to be richer in crude protein, gross energy, ether extract, acid detergent fiber, amino acid profile and mineral content than corn. However, digestibilities of dry matter (corn, 86·8%; PMA, 80·5%; PMB, 82·0%) and energy (corn, 85·3%; PMA, 78·8%; PMB, 80·5%) were higher (P<0·05) for corn than either of the pearl millet samples. Fat digestibility was much higher in pearl millet than corn. Although nitrogen intake and absorption were higher (P<0·05) for pearl millet, the digestibility of nitrogen was similar for pearl millet and corn. Net protein utilization was lower (P<0·05) in pearl millet when compared to corn (corn, 44·8%; PMA, 34·6%; PMB, 39·9%). Digestibilities of the essential amino acids, arginine, threonine, valine, isoleucine and lysine were higher in pearl millet than corn. Phosphorus retention, expressed as a percentage of intake and absorption, was higher in corn than pearl millet. Calcium intake and absorption were similar for pearl millet and corn. Intake and absorption of magnesium and managanese were also similar in pearl millet and corn. Zinc and copper retention, when expressed as a percentage of intake, were higher in corn, but absorption for both minerals was similar in corn and pearl millet. Pearl millet was found to supersede corn in nutrient content and amino acid digestibility.     

Nutritional improvement of lentils,chick pea,rice and wheat by natural fermentation

Effect of natural fermentation process (4 days) on the non-protein nitrogen, crude and true protein, amino acids content and in vitro digestibility of two kinds of legumes (lentils and chick pea) and two kinds of cereals (rice and wheat) was investigated. Non-protein nitrogen increased significantly (p<0.001) in the fermented products. Little increase has occured in the crude protein while no significant change was observed in the fermented true protein samples. It was observed that methionine and cystine which are considered the limiting amino acids in legume seeds were close to those of FAO/WHO patterns. Also, lysine content (the first limiting amino acid in cereals was higher in fermented rice than that of FAO/WHO pattern. Moreover, fermentation process improved significantly, the in vitro digestibility of both legume and cereal products.     

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.     

In vitro starch and protein digestibility and iron availability in weaning foods as affected by processing methods

In the present investigation, four weaning foods were formulated using locally available cereals and pulses such as wheat (Triticum aestivum), barley (Hordeum vulgare) and green gram (Vigna radiata). Cereal, pulse and jaggery were used in the proportion of 70:30:25. Domestic processing technique like roasting and malting were used to process cereals and pulses for development of weaning foods. All the four blends had a nutrient composition within the range prescribed by the Indian Standard Institute (ISI) for processed weaning foods. The processing of grains resulted in 16–20% increase in starch digestibility and 17–32% increase in protein digestibility. Also 16–32% increase in iron availability was observed on processing. The effect was more remarkable in malted weaning foods as compared to roasted ones.