Evaluation of the fixed nitrogen-to-protein (N:P) conversion factor (6.25) versus ingredient specific N:P conversion factors in feedstuffs

BACKGROUND: The crude protein (CP) of feedstuffs is important as an indicator of essential and non‐essential amino acids for livestock. The protein (P) level needs to be known accurately, to minimize the feeding of excess nitrogen (N) and to reduce N pollution. Laboratory methods for determining N content report N from amino acids, but also N from ammonia and from non‐amino acid sources. The determined CP based on 6.25 × N level typically overestimates the true protein of feedstuffs. RESULTS: Determined ingredient‐specific N:P conversion factors k_A, k_P and k were not equal to the standard 6.25 factor. The k_A had the highest value in all ingredients, which leads to the estimation of specific crude protein (SCP), which is closer to true protein (the summation of the total amino acid residues from amino acid analyses). The SCP(k_A) was lower than CP and true protein in all ingredients, demonstrating that CP might overestimate the actual protein in feedstuffs. CONCLUSION: Based on data from 677 feedstuff samples from 2009, it is concluded that the mean k_A should be 5.68 for corn, 5.64 for soybean meal, 5.74 for corn DDGS, 5.45 for poultry by‐product meal and 5.37 for meat and bone meal. Copyright © 2011 Society of Chemical Industry     

Japanese barnyard millet (Echinochloa frumentacea): Protein content,quality and SDS–PAGE of protein fractions

Total protein from five varieties of Japanese barnyard millet (Echinochloa frumentacea,) was separated into albumin/globulin, prolamin and glutelin fractions. The protein fractions were examined by sodium dodecylsulphate polyacrylamide gel electrophoresis. Total protein of the varieties ranged from 110·5 to 139·3 mg g^?1 of which 11·3–17·2% was albumin/globulins, 6·8–9·3% prolamins, 7·5–11·6% prolamin–like, 5·9–9·1% glutelin-like and 39·3–54·4% true glutelins. Amino acid analyses of the total protein showed that the varieties had essentially the same ammo acid composition. With the exception of lysine the amino acid levels adequately matched the provisional FAO scoring pattern. The amino acid composition of the protein fractions was also very similar. Electrophoretic analysis showed that the albumin/globulin fraction contained three or four components; the prolamin and glutelin fractions each had five components. The glutelin fraction had higher molecular weight components than the other two fractions.     

Relationships between amino acid composition and nitrogen of foxtail (Italian) millet (Setaria italica) grain of different varieties

The amino acid composition of 13 samples of foxtail millet (Setaria italica L) from six Chinese and one French varieties was determined as a function of their N content (N), which ranged from 1·82 to 3·65 g per 100 g of grain DM. The levels of amino acids in grain DM increased linearly with N with correlation coefficients close to 1 for most of them regardless of foxtail millet genotype or phenotype. Thus simply knowing N enables one to predict the amino acid composition of any foxtail millet grain sample. Amino acids in crude protein of grain (g 16 g^?1N)changed as quadratic functions of N, which decreased for glycine, cysteine, tysine, histidine and arginine, remained nearly constant for valine, threonine, tyrosine, methionine and aspartate plus asparagine, and increased for other amino acids. Foxtail millet appeared as the only cereal in which lysine is the only limiting essential amino acid. However, the lysine score was low and intermediate between that of maize and sorghum, falling from 48 to 31 % when N increased from 1·82 to 3·65 g per WO g DM. The N-to-protein conversion factor strongly increased with N and was the highest of all cereals within the N range studied. The results also showed that the composition of storage proteins accumulated in grains remained constant, with a prolamin to glutelin ratio close to three and independent of grain protein content.     

Seed protein contents and nitrogen-to-protein conversion factors for some uncultivated tropical plant seeds

Seed protein contents and nitrogen-to-protein conversion factors were calculated for 13 lesser-known tropical plant seeds based on total nitrogen and the summation of total amino acids. The total protein content, calculated from total amino acid residue, ranged from 4.90 in Diospyros mespiliformis to 32.47 g/100 g fresh weight in Gliricidia sepium. Resulting data gave a mean true conversion factor of 4.97±1.07 for the leguminoseae. In some seeds, comparisons indicated significant differences between the protein content based on the traditional factor 6.25 and that from amino acid analysis. An average of 22% of the total seed nitrogen appeared to be non-proteinogenic. In general, a conversion factor of 5.5 appears to provide a much more accurate estimate of the seed proteins. It is concluded that the conversion factor based on the total amino acid, rather than the traditional factor 6.25, is more valid for estimating protein contents in terms of nutritional benefits.     

Amino acid profiles and protein quality of cooked cassava leaves or ‘saka‐saka’

Cassava (Manihot esculenta Crantz) leaves form the main source of protein in a diet consisting of processed cassava roots as sole staple food in konzo‐affected areas of the Democratic Republic of Congo. Pounded cassava leaves were hydrolysed and analysed by HPLC before and after cooking to assess amino acid profiles and protein quality. An average of about 58% loss of total protein content was observed in five different cooked samples. The protein content in cassava leaves was high, an average of 285.9 g kg^?1 dry weight in the raw and 119.2 g kg^?1 dry weight in the cooked samples, but of poor quality, with sulphur amino acids as the most limiting amino acids. Lysine and leucine were also limiting amino acids in some of the raw samples. Lysine, histidine, leucine and isoleucine were limiting amino acids in the cooked samples besides the sulphur amino acids. The consumption of cassava leaves does not compensate the dietary deficiency of sulphur amino acids in the roots that are the staple food in konzo‐affected areas. Sulphur amino acids are essential for detoxification of the residual cyanogens remaining in insufficiently processed cassava roots. Cereals and legumes, as sources of sulphur amino acids and lysine respectively, should be promoted as part of the diet in those areas to prevent the paralytic neuro‐toxico‐nutritional disease konzo among the poor population. Copyright © 2003 Society of Chemical Industry     

Nutrient contents,rumen protein degradability and antinutritional factors in some colour- and white-flowering cultivars of Vicia faba beans

Six colour-flowering (Scirocco, Alfred, Carola, Condor, Tina and Herz Freya) and six white-flowering (Caspar, Albatros, Gloria, Tyrol, Vasco and Cresta) cultivars of Vicia faba were studied. The crude protein contents of colour- and white-flowering cultivars were 267±13·6 and 283±18·8 g kg⁻¹, respectively, which did not differ significantly at P<0·05. The levels of lipids, crude fibre, starch and ash varied from 14 to 22 g kg⁻¹, 88 to 143 g kg⁻¹, 407 to 485 g kg⁻¹ and 32 to 42 g kg⁻¹, respectively. The calculated organic matter digestibility (OMD) and metabolisable energy (ME) of the white-flowering cultivars were significantly higher (P<0·001) than those of the colour-flowering cultivars (OMD: 889·1±26·6 g kg⁻¹ vs 797·5±17·1 g kg⁻¹; ME: 13·97±0·49 vs 12·30±0·34 MJ kg⁻¹). In all cultivars, sulphur amino acids were lower than adequate concentration when compared with recommended amino acid pattern of FAO/WHO/UNO reference protein for a 2–5-year-old child. The in vitro rumen nitrogen degradability of colour-flowering cultivars was significantly lower (P<0·01) compared to that of white-flowering cultivars (71·4±9·3% vs 88·0±11·1%). Amongst colour-flowering varieties, the contents of total phenols (TP), tannins (T) and condensed tannins (CT) were highest in Alfred (28·3, 21·0 and 35·4 g kg⁻¹, respectively). The contents of TP and T were similar (about 15 and 10 g kg⁻¹, respectively) in Carola, Tina and Herz Freya, and the CT were in the order: Condor>Herz Freya>Carola. The CT were not detected in white-flowering varieties, T were virtually absent and TP were extremely low (4·0–4·9 g kg⁻¹). The activities of other antinutritional factors (white- and colour-flowering cultivars, respectively: trypsin inhibitor activity 3·05±0·34 and 1·85±0·09 mg trypsin inhibited g⁻¹; lectin 27·2±9·4 and 27·1±5·1 mg ml⁻¹ assay medium producing haemagglutination; phytate 15·0±2·7 and 16·6±2·3 g kg⁻¹) were very low. A strong negative correlation (r=-0·92, P<0·001) between tannins and in vitro rumen protein degradability was observed which suggested that tannins have adverse effect on protein degradability. Similarly negative correlations between tannin levels and metabolisable energy (r=-0·89; P<0·001) and organic matter digestibility (r=-0·89; P<0·001) were observed. The correlation coefficient between trypsin inhibitor activity and tannins was negative and highly significant (r=-0·88, P<0·001), whereas between tannins and saponins it was significantly positive (r=0·96, P<0·001). ©1997 SCI     

Wet Milling Comparison of Quality Protein Maize and Normal Maize

Quality protein maize (QPM) experimental hybrids and normal maize possessing different physical and chemical properties were studied as the raw material for wet milling. Maize samples were steeped for 36 h in a 600-ml solution containing 15 g kg⁻¹ lactic acid and 0·5 g kg⁻¹ SO₂ followed by 12 h in a second 600-ml solution containing 5 g kg⁻¹ lactic acid and 1 g kg⁻¹ SO₂. The steeped grain was then wet milled and the yields and purity of fractions were analysed. Water-soluble solids, kernel size, quality protein, total dietary fibre and ash content were higher in QPM samples than in normal maize. Water-soluble solids were positively correlated to kernel size ( r =0·97, P< 0·05), test weight ( r =0·83, P< 0·05) and density ( r =0·57, P< 0·05). Total fraction recovery for the five hybrids tested ranged from 921 to 955 g kg⁻¹, with the highest values corresponding to QPM hybrids. QPM hybrids yielded slightly higher starch content than normal maize. Gluten yields of QPM-HO (high oil) presented the highest values. The lysine contents of kernel, gluten and milling solubles were highest for QPM hybrids. QPM contained more palmitic acid than the other hybrids. The H-137 normal maize and QPM yellow dent-HO contained more oleic and linolenic acids than the other samples, and the QPM white-C (corneous) contained more linoleic acid than QPM-HO and normal maize.     

Nitrogen solubility in three solvents and in situ protein degradability of ruminant feedstuffs

Feedstuffs commonly fed to ruminants were assayed for nitrogen solubility by using McDougall's buffer, 0·02 M sodium hydroxide (NaOH), or 0·15 M sodium chloride (NaCl) as solvents. In addition, in situ dry matter and protein disappearance from the same feedstuffs were determined using the nylon bag technique in ruminally cannulated sheep for varying times of incubation. The mean effective nitrogen disappearance ranged from 235 for maize to 894 g kg⁻¹ of total N for lupins, and dry matter disappearance from 240 for meat and bone meal to 793 g kg⁻¹ for lupins. Protein solubility was lowest (<10% of total N) for oilseed by-products and animal and fish by-products, intermediate (15–30% of total N) for some cereals and highest (35–45% of total N) for wheat varieties and plant protein sources. Furthermore, solubility and degradability data for various feed proteins are presented which demonstrate the variability in solubility and degradability of ruminant feedstuffs due to protein type or processing. © 1997 SCI.     

Gross composition,amino acid,phytic acid and trace element contents of thirteen cowpea cultivars and their nutritional significance

Thirteen cultivars of cowpea (Vigna unguiculata (L) Walp) were analysed for their proximate composition, amino acid, trace element and phytic acid contents. Crude protein values ranged from 206·8 to 283·8 g kg^?1 DM. The mean contents (g kg^?1) of other major nutrients were ether extract, 18·6; ash, 38·8; total dietary fibre, 121·8 and carbohydrates, 573·4. When compared with the provisional amino acid scoring pattern of FAO, all cultivars were low in methionine and high in lysine, isoleucine, leucine and phenylalanine plus tyrosine. Values for threonine and valine were variable compared with the pattern. The range of values for the chemical score was 0·61–0·74. Phytic acid values ranged from 5·10 to 10·27 g kg^?1, and the phytate: zinc molar ratios were all higher than that (15:1) above which zinc deficiency can be induced. Most of the trace elements showed wide variation in their occurrence among the cultivars. The values for zinc and iron showed less variation. The toxic elements mercury and selenium were present in varying amounts in more than half of the cultivars while tin was found in only one variety.     

Characterisation of storage protein from selected varieties of foxtail millet (Setaria italica (L) Beauv)

Protein content of the three selected varieties of Setaria italica (L) Beauv ranged from 91·7 to 112·0 g kg⁻¹. Fractionation of seed protein showed that prolamin is the major storage protein and the differences in protein content among them is mainly due to differences in the total prolamin accumulation. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) pattern of different protein fractions; namely, albumin/globulin, prolamins and glutelins and RP-HPLC (reversed-phase high-performance liquid chromato-graphy) of the total prolamins showed great similarity among the three selected varieties. Accumulation of total protein and protein fractions during seed maturation was studied in all the three selected varieties. Fractionation of total protein in the grain collected at 5, 10, 15, 20, 25, 36 days after anthesis revealed that prolamin is the major storage protein ( > 50% of total protein) during all the stages of seed development. The SDS-PAGE pattern of the total prolamin at different stages of seed development showed no variation among the selected varieties. Prolamin polypeptide synthesis commenced as early as 5 days after flowering (DAF) and completed before 10 DAF. Thereafter, only quantitative increase was observed. Immunoblotting of the total prolamin from S italica probed with 20 kDa prolamin protein antibody of kodo millet (Paspalum scrobiculatum) showed that the two millets are immunologically related to one another. © 1998 SCI.     

Response of nutrient digestibilities to feeding diets with low and high levels of soybean trypsin inhibitors in growing pigs

Studies were carried out to determine the effect of dietary soybean trypsin inhibitor (SBTI) content on nutrient and energy digestibilities in growing pigs. Six barrows, average initial body weight (BW) 47·8±4·0 kg, were fitted with a simple T-cannula at the distal ileum and fed two diets according to a crossover design. Two maize starch-based diets were formulated to contain 200 g crude protein (CP) kg⁻¹ from either Nutrisoy (a food-grade defatted soy flour) or autoclaved Nutrisoy. The contents of SBTI in the Nutrisoy and autoclaved Nutrisoy diets were 13·4 and 3·0 g kg⁻¹, respectively. The experiment consisted of two periods of 12 days each. The average BW at the start of the first and second experimental periods were 53·3±3·7 and 61·0±5·1 kg, respectively. The average BW at the conclusion of the experiment was 71·8±7·6 kg. The ileal digestibilities of dry matter (DM), organic (OM), energy, CP and all amino acids measured were higher (P<0·01) in pigs fed the autoclaved Nutrisoy diet. The energy digestibility increased from 66·0 to 77·9%, and the CP digestibility increased from 37·4 to 77·1%. The increases in ileal digestibilities of the indispensable amino acids ranged from 27·0 (methionine) to 49·2 (leucine) percentage units. The increases in ileal digestibilities of the dispensable amino acids ranged from 30·2 (aspartic acid) to 50·8 (tyrosine) percentage units. The faecal digestibilities of all criteria measured were also higher (P<0·01) in pigs fed the autoclaved Nutrisoy diet. Furthermore, there was a greater (P<0·01) net disappearance (g kg⁻¹ DM intake) of DM, OM, CP, energy and all amino acids in the large intestine of pigs fed the Nutrisoy diet. In conclusion, feeding diets containing high levels of SBTI decreased both ileal and faecal digestibilities of all criteria measured. The formation of SBTI-enzyme complexes is likely to be responsible for the reduction in protein digestion and amino acid absorption. © 1998 SCI.     

The Nutritional Value of High-Lysine Barley Determined in Rats,Young Pigs and Growing Pigs

Three experiments, the first with rats, the second with young pigs and the third with growing pigs, were carried out to compare the nutritional value of cv Lysimax, a newly developed high-lysine barley, to cv Lami, a conventional barley grown in Denmark. In the diets for rats and growing pigs the barleys were the sole protein source while in the experiment with young pigs the barleys made up to 649 g kg^-1 of the respective diets. The lysine content of cv Lysimax was 52·6% higher than that of cv Lami; 4·99 g 16 g N^-1 compared to 3·27 g 16 g N^-1. The contents of threonine, tryptophane, methionine and cystine of cv Lysimax were 3·80, 1·41, 1·80 and 2·27 g 16 g N^-1, respectively; being 18·4, 8·5, 9·8 and 5·1% higher than in cv Lami. Conversely, the contents of glutamic acid and proline in cv Lysimax were 15·79 and 7·40 g 16 g N^-1, respectively, being 36·1 and 40·0% lower than in cv Lami. In the experiment with rats, the higher lysine content and the lower content of glutamic acid and proline in cv Lysimax resulted in a 34·8% increase (P<0·05) in biological value (BV); 0·867 for cv Lysimax compared to 0·643 for cv Lami. True protein digestibilities and energy digestibilities in rats fed cv Lysimax were 0·019 and 0·010 units lower (P<0·05) than for cv Lami. For young pigs the increased lysine content and the lower content of glutamic acid and proline of cv Lysimax increased (P<0·05) nitrogen (N) retention from 10·9 to 12·4 g day^-1, respectively, and increased (P<0·05) apparent BV from 0·690 to 0·734, respectively. The digestibility of energy was 0·030 units lower (P<0·05) for the diets with cv Lysimax than for the diets with cv Lami. Likewise, with growing pigs the increased lysine content and the lower content of glutamic acid and proline increased (P<0·05) N retention from 6·4 to 10·8 g day^-1 and apparent BV from 0·271 to 0·495, respectively. The apparent ileal digestibilities of lysine, threonine, tryptophane, methionine and cystine were similar (P>0·05) between the barleys. It is concluded that the development of high-lysine barley varieties could be beneficial for meeting the requirements of essential amino acids for monogastrics. Moreover, N excretion into the environment was substantially reduced due a reduction in the prolamine fraction which is rich in glutamic acid and proline. © 1997 SCI.     

Nutritional Value of Cassava for Use as a Staple Food and Recent Advances for Improvement

ABSTRACT: Cassava is a drought‐tolerant, staple food crop grown in tropical and subtropical areas where many people are afflicted with undernutrition, making it a potentially valuable food source for developing countries. Cassava roots are a good source of energy while the leaves provide protein, vitamins, and minerals. However, cassava roots and leaves are deficient in sulfur‐containing amino acids (methionine and cysteine) and some nutrients are not optimally distributed within the plant. Cassava also contains antinutrients that can have either positive or adverse effects on health depending upon the amount ingested. Although some of these compounds act as antioxidants and anticarcinogens, they can interfere with nutrient absorption and utilization and may have toxic side effects. Efforts to add nutritional value to cassava (biofortification) by increasing the contents of protein, minerals, starch, and β‐carotene are underway. The transfer of a 284 bp synthetic gene coding for a storage protein rich in essential amino acids and the crossbreeding of wild‐type cassava varieties with Manihot dichotoma or Manihot oligantha have shown promising results regarding cassava protein content. Enhancing ADP glucose pyrophosphorylase activity in cassava roots or adding amylase to cassava gruels increases cassava energy density. Moreover, carotenoid‐rich yellow and orange cassava may be a foodstuff for delivering provitamin A to vitamin A–depleted populations. Researchers are currently investigating the effects of cassava processing techniques on carotenoid stability and isomerization, as well as the vitamin A value of different varieties of cassava. Biofortified cassava could alleviate some aspects of food insecurity in developing countries if widely adopted.     

Cyanogenic potential of randomly sampled fresh and processed cassava on retail sale in Singapore

A random sample of fresh cassava roots and cassava products, purchased at various retail outlets in Singapore during 2016–2017, had total cyanogenic potential (CNp–expressed as mean ± standard deviation, mg kg⁻¹ HCN, fresh weight basis) as follows: fresh roots (n = 66) from three SE Asian countries, 59.0 ± 19.2; peeled chilled root pieces from Malaysia (20 × 1-kg packs), 38.5 ± 16.5; cassava flour from Indonesia (8 × 1-kg packs), 11.7 ± 8.2; dried Indonesian chips for home frying (5 × 250 g packs), 61.6 ± 16.5; one pack (120 g) of Malaysian ready-to-eat (RTE) chips, 17.1 ± 3.2. CNp in all flour and RTE chips was below 20 mg kg⁻¹. The majority of fresh roots (59.1%) and packs of dried chips (80%), and 15% of packs of peeled chilled root parenchyma, exceeded the Codex Alimentarius limit (50 mg kg⁻¹) for ‘sweet’ (boil-and-eat) cassava.     

Evaluation of Flour and Extruded Noodles from Eight Cassava Mosaic Disease (CMD)-Resistant Varieties

Flours processed from eight cassava roots were selected from recently developed Cassava Mosaic Disease resistant varieties (92b/00061, 95/0289, 92/0057, 96/1632, 98/0505, 97/2205, TME419 and 92/0326). They were evaluated for proximate composition, hydrogen cyanide, vitamin A and functional properties. They were also processed into noodles adapting a locally fabricated cold extruder as a single-screw extruder. The extruded cassava noodles were cooked and subjected to sensory analysis. Principal component and cluster analyses of the parameters were adopted using the correlation matrix with the objective of grouping the varieties into functional groups. The proximate composition showed that mean protein value ranged from 1.93% (98/0505) to 2.60% (96/1632) and fat ranged from 0.46% (92/0326 and 95/0289) to 0.95% (96/1632). The principal component analysis showed that PC₁, PC₂ and PC₃ were key components contributing 90.90% of the variables. Vitamin A determined as carotenoid ranged from 1.94 (92/0057) to 2.40 μg/g (TME419) while hydrogen cyanide concentration ranged from 8.20 (92/0057) to 11.14 mg/kg (96/1632). Noodles made from 95/0289 CMD variety had the least acceptable sensory properties while those made from 98/0505 were most generally acceptable. No significant (P ≥ 0.05) differences were noticed in taste, colour and general acceptability of all the samples. The sensory evaluation of noodles made from the eight cassava varieties (colour, taste, flavour, texture and general acceptability) produced two principal components which accounted for 85.80% while the functional properties explained 81.30% of the variations. The key sensory properties with significant eigenvalues based on their loadings (≥0.5) were colour, taste, texture and general acceptability. Compared to raw samples, dried noodles were about 1.98 times, while cooked noodles were up to three times greater in diameter, respectively. The result showed that cassava flour could serve as a good substitute to wheat flour in noodle production and utilisation.     

Purification,crystallisation and characterisation of carboxypeptidase from wheat bran

A carboxypeptidase was purified and crystallised from wheat bran. Disc gel electrophoresis at pH 4·0 and ultracentrifugal analysis revealed that the enzyme was essentially homogeneous. The sedimentation constant and isoelectric point were determined to be 6·3 S and 6·0, respectively. The molecular weight of the enzyme was estimated to be 118,000 by a gel filtration method. The enzyme liberated carboxyl terminal amino acid residues from a wide range of N-substituted dipeptides and tripeptides which contain l-proline. It had a pH optimum at pH 4·0 for Z-Glu-Tyr (Z-benzyloxycarbonyl). The K_m and k_cat values for Z-Glu-Tyr at pH 4·0 and 30°C were 0·19 mm and 20 s^?1, respectively. The enzyme hydrolysed Z-Gly-Pro-Leu-Gly-Pro and bradykinin sequentially at pH 4·0 from their carboxyl terminal amino acid residues. The enzyme activity was completely inhibited by DFP.     

Isolation and characterisation of invertase inhibitor from sweet potato storage roots

BACKGROUND: Plant invertases play important roles in sucrose metabolism. Cell wall invertase has been reported to participate in phloem loading and unloading. Soluble invertases are involved in hexose level regulation in mature tissues and in utilisation of stored sucrose within vacuoles. Invertase inhibitory proteins have been described as one of the possible components for invertase activity regulation in some plant species. RESULTS: In this work an invertase inhibitor (ITI) coding sequence was cloned by differential display from sweet potato (SP) storage roots. SPITI codes for a protein of 192 amino acids with a predicted molecular mass of 20 624 Da containing a 20‐amino‐acid signal peptide and four cysteines. Computer analysis of the deduced amino acid sequences of the conserved domain revealed that the protein belonged to the plant invertase/pectin methylesterase inhibitor. Both the corresponding mRNA and protein levels were found to be highest in storage roots, followed by veins. Recombinant SPITI protein from the storage root cDNA clone overproduced in Escherichia coli (M15) was purified by affinity chromatography. This protein effectively inhibited the invertase activity in a dose‐dependent manner. The results presented in the Lineweaver‐Burk plots indicated that the invertase inhibitor displayed a mode of competitive inhibition towards the invertase tested, with a K_i of 3.82 × 10^?6 mol L^?1. CONCLUSION: These results suggested that SPITI is a novel member of the ITI family in plants. SPITI genes of sweet potato storage roots display differential gene expression patterns, which may be associated with sucrose metabolism to cope with particular developmental requirements. Copyright © 2008 Society of Chemical Industry     

Progress in protein quality of maize

The protein quality of some improved protein quality maize varieties grown in Mexico was measured chemically (including amino acid analyses) and biologically, in N-balance experiments with growing rats. The protein content ranged from 10.61 to 12.84%. Lysine 100 g^?1 protein varied between 2.63% for a normal variety to 4.18% for one of the improved varieties. The tryptophan content in the improved varieties was increased by 40-100%. There was a highly significant (P<0.001) positive correlation (r=0.98) between biological value and lysine 100 g^?1 protein whereas the relationship between protein and available carbohydrate was not significant. True protein digestibility was very high and above 95% in all samples. Biological value, however, was higher by 10-15 percentage units in the improved materials compared to the normal maize.     

Proximate,Fatty Acid and Sterol Compositions of Aboriginal Peanut (Arachis hypogaea L) Seeds from Bolivia

Oil, protein, ash, carbohydrate, iodine value, fatty acid and sterol compositions were studied in 46 aboriginal Arachis hypogaea cultivars originating from Bolivia. The oil and protein contents varied between 440 and 547 g kg^-1 and 242 and 547 g kg^-1, respectively. Results showed a lower protein content in the variety hypogaea (264·4 g kg^-1) than in the varieties fastigiata (299·7 g kg^-1) and peruviana (294 g kg^-1). The carbohydrate content ranged between 86 and 216 g kg^-1. The principal fatty acids were oleic (358–536 g kg^-1) and linoleic (250–462 g kg^-1). The variety hypogaea exhibited higher concentrations of oleic acid (449·0 g kg^-1). The sterol composition showed higher concentration of β-sitosterol (554–632 g kg^-1) following by campesterol (139–180 g kg^-1), stigmasterol (82–130 g kg^-1) and Δ⁵-avenasterol (86–138 g kg^-1). © 1997 SCI.     

Accumulation of Fumonisins in Maize Hybrids Inoculated under Field Conditions with Fusarium moniliforme Sheldon

The accumulation of fumonisin B₁ (FB₁) and fumonisin B₂ (FB₂) after inoculation of 14 maize hybrids with Fusarium moniliforme has been examined in Poland during the seasons 1992–1995. Fumonisins have been detected in all 14 hybrids in amounts ranging from 0·09 mg kg^-1 FB₁+0·02 mg kg^-1 FB₂ to 93·2 mg kg^-1 FB₁+15·8 mg kg^-1 FB₂. Inoculated ears contained from <1% up to 60% of Fusarium damaged (=mouldy) kernels (FDK). Fumonisins' levels in FDK ranged from 5·1 mg kg^-1 FB₁+1·4 mg kg^-1 FB₂ up to 196·0 mg kg^-1 FB₁+62·0 mg kg^-1 FB₂. Significant influence of the year of inoculation on ear infection and fumonisins accumulation was observed. Only one hybrid (Mona) exhibited low disease score, low percentage of FDK (1·1–2·6%) and low levels of fumonisins (FB₁ from 0·09 to 1·66 mg kg^-1 and FB₂ from 0·02 to 0·42 mg kg^-1) during 3 years of experiments. © 1997 SCI.