Genetic and environmental variability in starch,fatty acids and mineral nutrients composition in cowpea (Vigna unguiculata (L) Walp)

Fifteen cowpea cultivars grown in three locations (Kano (12°00′N 8°31′E), Mokwa (9°17′N 5°04′E) and Ago-Iwoye (6°58′N 4°00′)) between 1993 and 1994 were analysed for genotype, environmental and genotype×environment variability for starch (g kg⁻¹), fatty acids (% of total oil) and mineral nutrients (g kg⁻¹) composition. There were significant environmental as well as genetic effects on these nutritional qualities. The environmental effect accounted largely for the variability observed in starch (60%), palmitic acid (80%), arachidic acid (100%), potassium (100%), phosphorus (81%) and manganese (86%), while the genotypic effect accounted largely for the variability observed in linoleic acid (50%), linolenic acid (50%) and copper (68%) contents. Correlation coefficient (pooled data) from the three locations indicated that starch was positively correlated to palmitic acid (r = 0·21, 0·01< P < 0·05), potassium (r = 0·80, P < 0·001) and phosphorus (r = 0·65, P < 0·001), but negatively correlated to oleic (r = −0·23, 0·01< P < 0·05), linoleic (r = −0·67, P < 0·001) and linolenic acid (r = −0·74, P < 0·001) contents. Starch showed a strong positive correlation with magnesium content (r = 0·75) and a strong negative correlation with copper (r = −0·73) and iron (r = −0·62) at the genetic level. This research established the degree of variability for these characters in cowpea. © 1998 Society of Chemical Industry.     

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.     

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     

Genotype × environment influence on cowpea (Vigna unguiculata (L) walp) antinutritional factors: 1 – trypsin inhibitors,tannins, phytic acid and haemagglutinin

The relative influence of genotype, environment and genotype×environment effects on four antinutritional factors (g kg⁻¹) of importance in cowpea were studied using 15 local and improved cowpea genotypes grown in 12 environments, comprising three locations over four seasons per location. The locations Ago‐Iwoye (6°58′N4°00′E), Mokwa (9°17′N5°04E) and Kano (12°00′N8°31′E) were representatives of the major agroecological zones where cowpeas are produced. Genotypes effects were strongest in controlling trypsin inhibitor content, while the environment was the major source of variation for tannins, haemagglutinin and phytic acid contents. Thus, the variability in the levels of these antinutritional factors in cowpea seeds depends largely on the environment where they are grown. This implies that a cowpea genotype grown and consumed safely in an environment can be poisonous when grown and consumed in another environment. Genotype×environment effects were significant for tannins, haemagglutinins and trypsin inhibitor contents. Correlation coefficients (pooled data) from the three locations indicated that trypsin inhibitor was positively correlated to phytic acid (r=0.59, 0.001<P<0.05) and haemagglutinins (r=0.64, 0.001<P<0.05) but negatively correlated to tannin contents ( r=−0.79, 0.001<P<0.05). © 1999 Society of Chemical Industry     

Relationships between the back-scatter of polarised light and the fibre-optic detection of connective tissue fluorescence in beef

The back-scatter of light (400–800 nm) from bovine m longissimus lumborum (n=47) was measured with a fibre-optic probe fitted with crossed polarisers to exclude Fresnel reflectance. Unlike normal fibre-optic spectra (which may be relatively flat), back-scatter was approximately proportional to wavelength, being low at 400 nm and high at 800 nm. The shape of the spectrum was modified by myoglobin absorbance, with a Soret minimum at 430 nm. Connective tissue fluorescence (365 nm excitation, 400–550 nm emission) was measured through a single optical fibre moving down the longitudinal axis of the muscle. Back-scatter at 430 nm was correlated positively with minimum fluorescence (r=0·73, P<0·001), the area under the fluorescence signal cm⁻¹ (r=0·81, P<0·001) and fluorescence peaks cm⁻¹ (r=0·46, P<0·005). Back-scatter at 800 nm was correlated weakly and negatively with minimum fluorescence (r=-0·28, P<0·05) and peaks cm⁻¹ (r=-0·26, P<0·05). Thus, in the probe detection of connective tissue fluorescence in meat, errors caused by differences in myoglobin concentration may exceed those caused by differences in pH-related light scattering. © 1997 SCI.     

Instrumental Assessments of Japanese White Salted Noodle Quality

Strong correlations were found between some sensory evaluation results and instrumentally (Instron, Model 4301) assessed quality parameters for Japanese white salted noodles made from 32 Australian wheats. The sensory texture parameter, softness, had a strong negative correlation (r=-0·74, P<0·001) with the instrumental texture parameter, cutting force peak area divided by time. Other sensory texture parameters, smoothness and elasticity, showed significant correlations with another instrumental parameter, compression force peak area divided by time (r=-0·58, P<0·001 and r=0·52, P<0·01 respectively). Brightness, yellowness and discolouration of both raw and cooked noodles were measured using a colorimeter (Minolta, Model CR310). Strong correlations were observed between yellowness and discolouration of raw noodles and CIELAB b* (r=-0·79, P<0·001) and L*a* (r=-0·63, P<0·001) values, respectively. Similar relationships were found for cooked noodles (r=-0·74, P<0·001 for yellowness and r=-0·53, P<0·01 for discolouration). Both flour pasting properties including the flour swelling test and mixograph dough properties showed strong correlations with instrumental measures of noodle texture. Protein and ash content significantly affected noodle colour. In an attempt to simplify objective noodle quality measurements instrumental texture tests were carried out on flour gels. Textural measurements of flour gels showed that sensory softness of cooked noodles was correlated with an instrumental parameter, cutting peak force divided by time (r=-0·46, P<0·01). However, in this study no strong correlations were found between the smoothness and elasticity of noodles and any parameters of compression force-time profiles derived from gels. Yellowness of flour gels measured by a colorimeter showed a significant correlation with that of cooked noodles (r=-0·68, P<0·001). © 1997 SCI.     

Effects of cooking on content of amino acids and antinutrients in three Chinese indigenous legume seeds

The effects of domestic cooking on the content of amino acids and antinutrients of Phaseolus angularis, Phaseolus calcaratus and Dolichos lablab seeds were evaluated. Heat treatment (30 min) caused significant declines (P<0·05) in the apparent recovery of most of the essential amino acids except leucine and phenylalanine for P angularis, and except phenylalanine for P calcaratus. Cooking D lablab seeds (60 min) also resulted in a significant reduction (P<0·05) in the apparent recovery of all the essential amino acids except leucine, histidine, lysine and threonine. Increased cooking time for P angularis (60 min), P calcaratus (60 min) and D lablab (120 min) led to a lower apparent recovery of methionine (28·9–31·6%) and cystine (17·1–19·3%). Even with increased cooking times, the total essential amino acid levels in all three cooked seeds remained higher than that of the FAO/WHO requirement, except for methionine and cystine. Cooking (60 min) was found to be effective in reducing the tannin contents of P angularis, P calcaratus and D lablab seeds by 70·6, 64·6 and 74·6%, respectively. Upon cooking, phytate and trypsin inhibitory activity in different seeds were also reduced to different extents depending on the cooking times. ©1997 SCI     

Comparative composition of aerial and subterranean potato tubers (Solanum tuberosum L)

The composition of aerial and subterranean tubers of two potato genotypes cvs Desiree (red skin) and Epicure (white skin) was compared immediately after harvest using a range of analytical methods. Irrespective of genotype, aspartic acid, arginine, glycine, glutamic acid, histidine, leucine, serine, threonine and total amino acid concentrations were significantly higher (P<0·05) in aerial compared with subterranean tuber tissue. Significant increases (P<0·05) in valine in aerial tubers, but no significant differences in alanine, tyrosine and iso-leucine, when compared with subterranean tubers of cv Desiree, were found. In cv Epicure, alanine, tyrosine and iso-leucine were significantly higher in aerial tubers (P<0·05); however, no significant differences in valine were recorded. There was no significant increases in lysine and phenylalanine between tuber types. Regardless of genotype α-solanine, α-chaconine, chlorogenic acid, chlorophyll and crude protein concentrations were significantly higher in aerial tubers compared with subterranean ones (P<0·01). No significant increases in total lipids between tuber types were found. In cv Desiree, ascorbic acid content was not significantly different between aerial and subterranean tuber tissue, but in cv Epicure concentrations were significantly higher (P<0·01) in aerial tubers. Starch concentrations were significantly higher in subterranean tubers of both cultivars (P<0·05). Sugar content was significantly higher in aerial tubers of cv Epicure (P<0·01), but not significantly different between aerial and subterranean tubers of cv Desiree. Regardless of genotype, phosphorus, magnesium, potassium, zinc, manganese and sodium concentrations were significantly higher (P<0·05) in aerial tubers. Iron and copper concentrations were significantly higher in aerial tubers of cv Desiree (P<0·01), but significantly less in cv Epicure compared with subterranean tubers (P<0·01, P<0·05). Calcium concentrations were not significantly different between aerial and subterranean tubers of cv Desiree, but significantly higher in aerial tuber tissue of cv Epicure (P<0·01). Total gross energy (mJ kg⁻¹ FW) was higher in aerial tubers of cv Desiree compared with subterranean tubers (P>0·05), but not significantly different between aerial and subterranean tubers of cv Epicure. The potential applications of aerial tubers for industrial purposes are discussed. © 1997 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.     

Thermal Effects on Net Protein Ratio of Red Kidney Beans (Phaseolus vulgaris L)

Net protein ratio (NPR), predicted-protein efficiency ratio (P-PER), relative NPR (RNPR), and corrected RNPR (CRNPR) of thermally processed red kidney beans were estimated in rats and compared to in vitro protein digestibility-corrected amino acid score (AAS_IVDP), and computed-protein efficiency ratio (C-PER). Thermal processing had a significant effect on protein intake, NPR, P-PER and CRNPR values of beans. Changes in protein intake suggest that heat processing had an effect on the palatability of the beans. Home-cooked beans and commercially canned beans had higher NPR values than beans autoclaved at 128°C for 20 min, while beans autoclaved at 121°C for 10–90 min had intermediate values. High correlation coefficients between P-PER and C-PER, CRNPR and C-PER, and CRNPR and AAS_IVDP (r=0·990, 0·992 and 0·960, respectively, P<0·001) were observed.     

Effects of intraruminal infusions of propionate and butyrate with two different protein supplements on milk production and blood metabolites in dairy cows receiving grass silage-based diet

Four cows were used in a balanced 4×4 Latin square with 2 week experimental periods to investigate the effects of intraruminal infusions of volatile fatty acids and protein source on milk production and blood metabolites. The four treatments in a 2×2 factorial arrangement were isoenergetic intraruminal infusions of propionate (500 g day⁻¹) or butyrate (417 g day⁻¹) each given with isonitrogenous protein supplementation of fish meal (FM) or barley protein (BP). The cows were fed restrictively with 9 kg dry matter day⁻¹ of formic acid treated grass silage and 8 kg day⁻¹ of concentrate. Propionate infusion increased milk yield (24·9 vs 23·4 kg day⁻¹; P<0·05), milk protein yield (832 vs 778 g day⁻¹; P=0·05) and milk lactose content (44·7 vs 43·5 g kg⁻¹; P<0·05) and yield (1113 vs 1023 g day⁻¹; P<0·01), whereas butyrate infusion was associated with a higher milk fat content (44·7 vs 39·4 g kg⁻¹; P<0·01) and yield (1033 vs 974 g day⁻¹; P<0·01). FM tended (P<0·10) to increase milk yield, but had no significant effects on milk composition or milk component yields compared with BP. Butyrate infusion increased blood ketones, plasma non-esterified fatty acids and glycine relative to propionate infusion. The concentrations of ammonia N in rumen fluid and urea in plasma and milk were similar for both protein supplements. The profile of amino acids in plasma was similar for both protein supplements except for the higher concentrations of phenylalanine, proline and tyrosine with BP. The results show that protein utilisation can be improved by increasing the supply of propionate from rumen fermentation in cows given a grass silage-based diet. © 1998 SCI.     

Caecal metabolites and microbial populations in chickens consuming diets containing a mined humate compound

The objectives of this study were to compare the short-chain fatty acid (SCFA) concentrations, amino acid concentrations and key carbohydrate-fermenting anaerobic bacterial populations in the caeca of chickens consuming either control diets or a mined humate compound (MH; Menefee Humate^TM). Dietary MH at concentrations of 0, 5 or 10 g kg⁻¹ did not affect (P ⩾ 0·05) the caecal concentrations of SCFA and amino acids. Regardless of treatment, acetate was found to be the predominant SCFA in the caecum followed by propionate (P < 0·05). MH had no effect on the caecal concentrations of 17 amino acids compared with control birds but, when analysed across treatments, glutamate was found to be the predominant free amino acid in the caecum, followed by alanine (P < 0·05). MH did not significantly influence any of the anaerobic microbial populations but Escherichia coli populations from birds receiving either 10 or 50 g kg⁻¹ MH were between 10 and 100 times greater than control birds (P < 0·05). It appears that MH does not influence concentrations of fermentation acids or amino acids in the caecum but may influence levels of individual microbial populations. © 1998 SCI.     

Dietary manipulation of the yield and composition of milk: Effects of dietary inclusions of barley and oats in untreated or formaldehyde-treated forms on milk fatty acid composition

Eight 1st-lactation cows were given four dietary treatments in a duplicated 4×4 Latin square experiment. Diets consisted of hay and soya bean meal together with barley, formaldehyde-treated barley, oats or formaldehydetreated oats (approximately 34:12:54 on a dry matter basis). Barley diets supplied 211 g fatty acids d^?1, oats diets supplied 537 g d^?1. The fatty acid composition (g kg^?1 total fatty acids) for barley diets was: 300 (16:0); 20 (18:0); 150 (18:1); 470 (18:2); 60 (18:3). Corresponding values for oats diets were 180, 20, 390, 380 and 30 g kg^?1. Formaldehyde treatment of the cereals tended to increase milk yield and reduce milk fat content (P<0·01 for barley) but did not affect milk fatty acid composition. Feeding oats in replacement for barley significantly (P<0·05) increased milk yield and lactose yield and reduced milk fat content (P<0·05 for the untreated cereals) and protein contents (P<0·01) without significant effects on milk fat or protein yields. Oats diets led to significant (P<0·001) reductions in the content of 8:0–16:0 fatty acids in milk fat with associated increases (P<0·001) in the content of 18:0 and 18:1. Changes in milk fat content of 18:2 and 18:3 acids were small. The results show the inclusion of oats in the cow's diet to be a means of reducing the saturated fatty acid content of milk fat thereby improving the nutritional value of milk and milk products and their appeal to the health-conscious consumer.     

Effects of High Hydrostatic Pressure on the Physical,Microbial, and Chemical Attributes of Oysters (Crassostrea virginica)

The change in the quality attributes (physical, microbial, and chemical) of oysters (Crassostrea virginica) after high hydrostatic pressure (HHP) treatment at 300 MPa at room temperature (RT, 25 °C) 300, 450, and 500 MPa at 0 °C for 2 min and control oysters without treatment were evaluated over 3 wk. The texture and tissue yield percentages of oysters HHP treated at 300 MPa, RT increased significantly (P < 0.05) compared to control. Aerobic and psychrotrophic bacteria in control oysters reached the spoilage point of 7 log CFU/g after 15 d. Coliform counts (log MPN/g) were low during storage with total and fecal coliforms less than 3.5 and 1.0. High pressure treated oysters at 500 MPa at 0 °C were significantly higher (P < 0.05) than oysters HHP treated at 300 MPa at 0 °C in lipid oxidation values. The highest pressure (500 MPa) treatment in this study, significantly (P < 0.05) decreased unsaturated fatty acid percentage compared to control. The glycogen content of control oysters at 3 wk was significantly higher (P < 0.05) when compared to HHP treated oysters [300 MPa, (RT); 450 MPa (0 °C); and 500 MPa (0 °C)]. HHP treatments of oysters were not significantly different in pH, percent salt extractable protein (SEP), and total lipid values compared to control. Based on our results, HHP prolongs the physical, microbial, and chemical quality of oysters.     

The apparent ileal digestibility of amino acids and the digestible energy content of naked oats (Avena sativa cv Bandicoot) fed to growing pigs

An experiment was conducted to determine the apparent ileal digestibility of amino acids and the digestible energy (DE) content of two samples of naked oats (Avena sativa cv Bandicoot) and to compare these parameters in wheat (Triticum aestivum cv Machete) and dehulled oats (groats; Avena sativa cv Echidna). Four Large White male pigs were fitted with simple T-piece ileal cannulae and allocated to experimental diets in a 4×4 Latin square design. Amino acid digestibility coefficients were determined after continuous eight hour collections of digesta over two consecutive days using acid-insoluble ash as an indigestible marker. Digestible energy was determined using grab samples of faeces. No significant difference between the four test cereals was found in the digestibility of all amino acids, except for proline and lysine. The apparent ileal digestibility of lysine in wheat (0·87) and two samples of naked oats (0·89 and 0·82, respectively) was lower (P<0·05) than dehulled oats (0·91). The mean DE value of the naked oats samples was 16·96 MJ kg⁻¹ (air-dry basis). The results suggest that Bandicoot naked oats and dehulled oats are superior amino acid and DE sources to wheat and have potential for use in weaner and grower pig diets. © 1998 SCI.     

Chemical Composition,Amino Acid Content and Protein Quality of the Little-Known Legume Bauhinia purpurea L

Some nutritional and antinutritional characteristics and biological value of Bauhinia purpurea L seeds were studied. The mature seeds contained (g kg^-1 as is) 271·7 crude protein, 58·7 crude fibre, 124·5 crude fat, 29·3 ash and 515·3 carbohydrates. Potassium, phosphorus and iron occurred in higher concentrations when compared with commonly consumed legumes. The globulins and albumins together constituted major storage proteins (82% total protein). The essential amino acid profile of total seed proteins compared well with the FAO/WHO reference pattern except for a deficiency of sulphur-containing amino acids and tryptophan. When compared with the globulins, the albumins appeared to be a rich source of cystine, methionine, threonine, lysine and tryptophan. Seed lipids contained high levels of the unsaturated fatty acids, oleic and linoleic, which accounted for 62·6% of total fatty acids recovered. Both dry heating and autoclaving significantly reduced the antinutritional compounds. The in vitro protein digestibilities of raw, dry-heated and autoclaved seeds were 59·5, 72·3 and 78·7%, respectively. True digestibility and net protein utilisation were significantly higher in processed seed samples compared with raw seeds. Regarding utilisable protein, autoclaved samples exhibited relatively higher values than raw seeds. © 1997 SCI.     

Effects of Silage Fermentation and Post-ruminal Casein Supplementation in Lactating Dairy Cows: 1—Diet Digestion and Milk Production

Two silages were prepared from the first-cut sward of timothy-meadow fescue and wilted to a dry matter (DM) content of 300 g kg^-1. One was ensiled with the addition of a formic-acid-based additive (4 litres formic acid (FA) per tonne) and the other with the addition of a bacterial inoculant (LAB) at a rate of 5×10⁶ colony forming units g^-1. Both silages were well preserved, but the extent of fermentation was greater in LAB-silage than in FA-silage as indicated by a lower concentration of water soluble carbohydrates (68 vs 177 g kg^-1 DM) and a higher concentration of lactic acid (147 vs 32 g kg^-1 DM). Four Ayrshire cows were used in a 4×4 Latin square experiment with 21-day periods to study the effects of silage fermentation and postruminal casein supplementation on silage intake, nutrient supply and milk production. The four treatments were FA-silage without casein (FA-0), LAB-silage without casein (LAB-0), FA-silage with casein (FA-C) and LAB-silage with casein (LAB-C). Both silages were given ad libitum with 8 kg day^-1 of barley without or with 400 g day^-1 of casein infused into the duodenum. Organic matter digestibility was lower (0·723 vs 0·753; P<0·01) for FA-silage than for LAB-silage. Cows offered FA-silage had a higher molar proportion of acetate and a lower proportion of propionate in ruminal fluid than cows offered LAB-silage. Microbial protein synthesis estimated from the output of purine derivatives in urine was greater (288 vs 260 g N day^-1; P<0·05) for cows given FA-silage compared with LAB-silage. Feeding LAB-treated silage tended (P<0·10) to decrease silage DM intake compared with FA-treated silage (10·61 vs 11·77 kg DM day^-1). Silage composition did not affect significantly milk yield or milk composition. Casein infusion increased milk yield (25·1 vs 27·1 kg day^-1; P<0·05), milk protein content (32·4 vs 33·8 g kg^-1; P<0·05) and protein yield (808 vs 905 g day^-1; P<0·01). The responses were similar for both silages. © 1997 SCI.     

Characterisation of Lignin from Parenchyma and Sclerenchyma Cell Walls of the Maize Internode

Internodes of maize (Zea mays L, Co125), harvested 5 days after anthesis, were sectioned into five equal parts and samples of sclerenchyma and parenchyma cells mechanically isolated from each section. Phenolic acids and syringyl and guaiacyl degradation products of lignin were released from the walls of the two cell types by microwave digestion with 4 M NaOH. Aryl ether bonded units were selectively released by thioacidolysis. Total phenolic content of cell walls from the youngest (basal) sections were approximately two-thirds of those of the oldest, topmost sections (parenchyma 70·8–99·0 and sclerenchyma 72·5–114·1 mg g^-1) indicating that the process of lignification was already well advanced amongst most of the cell walls of the youngest section. The total phenolic content was marginally, but significantly, greater (P<0·05) in sclerenchyma walls than in parenchyma walls at all stages of maturity. There was no significant difference in phenolic acid concentrations between cell types from the same section but p-coumaric acid concentration increased with maturity (P<0·001) in walls from both cell types. The increase in p-coumarate with age was matched by an increased recovery of syringyl units resulting in a constant coumaroyl: syringyl molar ratio. Recovery of acetosyringone was significantly greater (P<0·001) from sclerenchyma than parenchyma walls and, in sclerenchyma, acetosyringone as a proportion of total syringyl recovery, increased significantly with age (P=0·015). Digestion with NaOH and thioacidolysis released comparable amounts of guaiacyl residues but NaOH digestion released approximately twice the amount of syringyl residues. This difference may be explained by the retention of the ester-bond between p-coumaric acid and syringyl units during thioacidolysis but not during digestion with 4 M alkali. The similarity in phenolic composition suggested that both cell types, despite their considerable anatomical differences, were exposed to a common flux of lignin precursors during the later stages of lignification as illustrated by the internode sections. Differences between cell walls arose because of differences in the regiochemistry of precursor incorporation. © 1997 SCI.     

Effects of ingredients on the characteristics of rice cakes

Steamed leavened rice cakes made from rice flour, sugar, water, yeast or baking powder were used to study the effects of ingredients on cereal-based cakes. Volume expansion linearly correlates to amylopectin and negatively correlates to amylose content (r²=0·84), with an optimum amylose/amylopectin ratio of approximately 1: 8. Higher amylopectin content resulted in sticky, elastic and unacceptable cake. The optimum water content for volume expansion was in the range of 90±5% by weight of rice flour. Sugar content correlates linearly with volume expansion and tenderness of chemically leavened rice cakes (CLRC) (r²=0·99 and 0·92, respectively). Sugar content above 50% of rice flour weight decreased volume and softness of yeast-leavened rice cakes (YLRC). Tenderness of YLRC correlates linearly to fat content (r²=0·98), but volume expansions correlates negatively to the square root of fat content (r²=0·81 and 0·97 for the two rice cakes). Both tenderness (r²>0·92) and volume expansion (r²>0·93) correlates linearly with emulsifier content up to 3% by weight of rice flour, above which the cake becomes crumbly. A little salt increased hardness, but further increase reduced both volume expansion and hardness of rice cakes. Skimmed milk powder greatly increased the expansion of CLRC. Ovalbumin content correlates linearly to volume expansion of YLRC (r²=0·87) but negatively to the expansion of CLRC (r²=0·96). The proteins that improved the textures of rice cakes were skimmed milk and egg white with an optimum content of 2–4%. Egg yolk, soya protein, whey powder and wheat gluten reduced both tenderness and volume expansion. The effects of the various ingredients interacting together were studied and the optimum formulations was determined using a Random Centroid Optimisation Program. © 1998 SCI.     

Combined Effect of Drying Time and Slice Thickness on the Solar Drying of Okra

The effect of slice thickness and drying time on colour, viscosity, microbial load, moisture, crude fibre, vitamin C and ash contents of okra (Hibiscus esculentus) during solar drying was studied using three slice thicknesses (5·0 mm, 10·0 mm, 15·0 mm) obtained from a survey and five drying times (0, 24, 48, 72 and 96 h). The results showed that slice thickness had a significant effect (P<0·01) on moisture, crude fibre and ash contents but not on vitamin C content, viscosity, colour and microbial load. However, the effect of drying time was highly significant (P<0·01) on all the parameters determined. The combined effects of slice thickness and drying time were observed to be highly significant (P<0·05) on ash, crude fibre and moisture contents, viscosity and microbial load but had no significant effect (P<0·05) on colour and vitamin C content. There was a strong correlation between moisture content and ash (R=-0·926), crude fibre (R=-0·94), vitamin C contents (R=0·928) and viscosity (R=-0·963) in all samples during drying. The study showed that a slice thickness of 10·0 mm and a drying time of 48 h was suitable for the solar drying of okra. © 1997 SCI.