Effects of explant source,culture medium: Strength and growth regulators on the in-vitro propagation of three Jamaican yams: (Dioscorea cayenensis,D trifida and d rotundata)

Explants of tuber, meristem and vines from three widely cultivated yam species in Jamaica—D cayenensis, D rotundata and D trifida—were examined for their responses to mineral media strength, inorganic ammonium and growth regulator supplements. Tuber pieces (5mm³) showed some positive growth responses but did not produce in-vitro plantlets on all the media tested. Meristem tips of D trifida grew rapidly on basal media (BM) supplemented with either 0.1 mglitre^?1 6-benzylamino purine (BAP) and 0.01 mg litre^?1indole butyric acid or 0.2 mg litre^?1 BAP and 1.0 mg litre^?1 naphthalene acetic acid (NAA) producing plantlets by 28 weeks. The nodal explants grew rapidly with plantlets obtained from all the cultivars within 4 weeks. Use of young, vigorously growing vines of 8 weeks or less, as explant source, gave low contamination levels (16–25%) in culture when sterilised for 30 min in 200 g litre^?1 NaOCl in the case of D trifida and 300 g litre^?1 NaOCl in the case of D cayenesis prior to culturing. Initiation of growth was optimal when explants were taken from monopodial vines grown in October or January and placed on BM supplemented with 0.5 mg litre^?1 BAP (BM0.5BAP). Addition of 0.5 mg litre^?1 kinetin to the BM or 0.05 mg litre^?1 NAA to BM0.5BAP depressed shoot production, while 5.0 mg litre^?1 kinetin increased swelling of the nodal region in explants from sympodial shoots and from vines grown in March. The results suggest that nodal segments excised from young, fast growing vines of these species are the best explant source for the purpose of commercial micropropagation.     

Studies on the effect of protectants on Lactobacillus acidophilus strain dehydrated under controlled low-temperature vacuum dehydration and freeze-drying by using response surface methodology

Ca²⁺ (0–60 g litre^?1), glycerol (0–100 g litre^?1), and non-fat dry milk solids (NFDMS, 0–140 g litre^?1) were combined to study their effects on the survival of Lactobacillus acidophilus in controlled low-temperature vacuum dehydration and freeze-drying. A three-variable (each at three-levels) design method was used and analysed by fitting a quadratic response surface. These factors were found to be significantly effective on survival. Fitted quadratic regression equations were plotted using a graphing software package. Conditions for the best survival of freeze-drying was found to be Ca²⁺ 5.34 g litre^?1. NFDMS 100.8 g litre^?1, and glycerol 41.5 g litre^?1 and that of controlled low-temperature vacuum dehydration was Ca²⁺ 5.67 g litre^?1, NFDMS 107.1 g litre^?1, and glycerol 41.0 g litre^?1. Models obtained were tested using t-tests. Survival of freezing under different conditions was found to be not significantly different.     

Inhibitory effect of Aspergillus niger on the growth of Aspergillus ochraceus and Aspergillus flavus,and on aflatoxin formation

Aspergillus ochraceus and A flavus were grown on synthetic media (SM) supplemented with 50 or 200 ml litre^?1 SM on which A niger had been grown previously ( ‘A niger medium’ = ANM). Controls included SM acidified to pH 6.0 or 4.4, SM diluted with 50 or 200 ml litre^?1 water, and diluted-acidified SM. For both fungi, higher growth inhibition was recorded on ANM-containing SM than in the controls. Aflatoxin formation was markedly inhibited on SM to which 20 ml litre^?1 ANM extract (in methanol/chloroform, 2:1 v) had been added, although the growth of A flavus on that medium was almost the same as that in the control. It is concluded that the inhibitory effect of A niger on the growth of fungi should not be attributed merely to pH reduction, but also, mainly, to metabolites produced by the fungus in the growth medium, even at early stages of its growth.     

Effect of temperature,carbon dioxide enrichment,nitrogen form and rate of nitrogen fertiliser on the yield and nitrate content of two varieties of glasshouse lettuce

Head weight of winter glasshouse lettuce was increased slightly by higher temperature (7°C day/4°C night and 10°C day/7°C night) and carbon dioxide enrichment (350 and 1000 μl litre^?1) but, despite faster growth, plant nitrate concentration was unaffected. Addition at the lowest rate (138 kg ha^?1 N) of ammonium nitrate, calcium nitrate and urea increased plant nitrate by a similar amount compared with nil fertilizer nitrogen, but addition of more fertilizer (276 kg ha^?1 N) had no further effect. Urea produced a lower yield than the other two N sources. Coated controlled-release nitrogen produced both low yields and low plant nitrate concentrations because its nitrogen release rate was too slow to keep pace with plant growth. The most effective material in terms of high yield and low plant nitrate was one containing a nitrification inhibitor within the fertiliser granules.     

The yeast flora of ensiled whole-crop maize

The yeast flora in samples of 13 different whole-crop maize silages was shown to be predominated by Candida krusei, C. lambica, Saccharomyces dairensis, S. exiguus, C. holmii or C. milleri. All these strains fermented glucose but, except for the latter three species, not sucrose, α-trehalose or raffinose. Under conditions resembling those in silage, i.e. at pH 4.0 in the presence of a complex nitrogen source, all strains assimilated lactic and acetic acids. This result suggests that the predominant yeasts in silage should not be distinguished into lactate utilisers and lactate non-utilisers. All strains, except those of Saccharomyces dairensis, tolerated acetic acid (5 g litre^?1) and grew at pH 4.0 in a mineral salts medium containing lactic acid (10 g litre^?1), acetic acid (5 g litre^?1) and yeast extract (1 g litre^?1). Growth in this medium was completely inhibited by the cationic detergent Arquad C33W (20 mg litre^?1), propionic acid (5 g litre^?1), benzoic acid (5 g litre^?1) or salicylic acid (10 g litre^?1).     

Cassava leaves as animal feed: Potential and limitations

The nutrient composition and potential productivity of cassava (Manihot esculenta Crantz) leaves are examined, and their usefulness as a protein supplement in animal nutrition in the tropics is reviewed. On average, meal prepared from cassava leaves contains (on a dry matter basis) 210 g kg^?1 crude protein, 250 g kg^?1 acid detergent fibre, 85 g kg^?1 ash, 14.5 g kg^?1 calcium and 4.5 g kg^?1 phosphorus. Cassava leaf protein is well balanced, except for a deficiency of sulphur-containing amino acids. The presence of hydrocyanic acid and tannins is considered, but a leaf meal with low levels of these anti-nutritional factors may be prepared using simple processing techniques. The most immediate prospects for the use of cassava leaf products are in the following areas: (i) low level inclusion of leaf meal in feed formulations for monogastric animals, and (ii) fresh forage as a protein supplement to low-quality roughages in ruminant feeding. Relevant future research needs are also identified.     

Potential phytotoxic components of pulverised fuel ash

The release of aluminium, arsenic, boron, cobalt, copper, chromium, manganese, nickel, lead and zinc from pulverised fuel ash (PFA) and a standard Wellesbourne soil were studied by extraction with nitric acid and EDTA and by anaerobic incubation with grass meal. According to each of the criteria, only aluminium, arsenic, boron and copper were released in appreciably greater quantities from PFA than from soil. There were considerable variations in pH and the total content of soluble salts, mainly sodium, potassium, magnesium and calcium sulphates, between samples of ash. pH varied from 4.6 to 9.3 and the conductivity declined from 4.75 × 10^?3 to 3.2 × 10^?3 ohm^?1 cm^?1 with increased pH. The pH of the ash also influenced the concentration of other ions in water in equilibrium with it. When the pH was low the concentrations of aluminium and copper were large but those of arsenic were small. By contrast, when pH was high, the concentrations of arsenic were substantial and those of aluminium and copper small. The concentrations of boron, though always substantial, declined with increase in pH. It is concluded that, in addition to sulphate and boron, aluminium, copper and arsenic are potential causes of phytotoxicity.     

Post-harvest application of diphenylamine and ethoxyquin for the control of superficial scald on Bramley's seedling apples

Recent changes in the antioxidant regulations in the UK and the need to evaluate the effectiveness of scald control chemicals in the presence of other post-harvest chemicals led to a comparative study of the effects of diphenylamine (DPA) and ethoxyquin on scald development in Bramley's Seedling apples. A range of concentrations (1000–4000 mg litre^?1 a.i.) of DPA completely controlled scald on Bramley apples kept in controlled atmosphere storage for 241 days; ethoxyquin at equivalent rates was less effective. Only partial control of scald was achieved with 500 mg litre^?1 a.i. DPA. None of the treatments injured the fruit. Control of scald by 2000 mg litre^?1 a.i. DPA or ethoxyquin was not impaired by adding thiophanate-methyl (l g litre^?1 a.i.) or calcium chloride (10 g litre^?1) although the measure of control was reduced when both fungicide and calcium chloride were added. Calcium chloride caused lenticel injury which was aggravated by adding ethoxyquin but reduced by incorporating DPA. The concentrations of ethoxyquin and DPA residues on the fruit immediately after treatment were within the limits required by UK legislation (see reference 1) of 3 mg kg^?1 and 10 mg kg^?1, respectively, even where 4000 mg litre^?1 had been applied. An initial residue concentration of 2.3 mg kg^?1 DPA was associated with complete control of scald. Residue levels, particularly of DPA, declined rapidly during the first month of storage.     

Hydroxycinnamates of Vitis vinifera: Sensory assessment in relation to bitterness in white wines

The bitter and astringent taste properties of hydroxycinnamoyl tartaric acids have been responsible for incorrect speculation that these compounds influence the taste of wine. The sensory contribution of the major hydroxycinnamates found in wine was evaluated by duo—trio difference tests in model wine solutions and in white wine. The major hydroxycinnamate compound, trans-caffeoyl tartaric acid, was not detectable when added at the highest level at which it has been found in wine, 150 mg litre^?1. Similarly, no significant difference in taste was produced when caffeic acid and p-coumaric acid were added at 120 mg litre^?1 and 30 mg litre^?1, respectively. Trans-2-S-glutathionyl caffeoyl tartaric acid, a product of oxidase activity in must, was not detectable at 50 mg litre^?1. It was concluded that the hydroxycinnamates do not play any direct role in the taste of wines.     

Preliminary studies on acidity-astringency interactions in model solutions and wines

Intensity of astringency in model solutions and wines varying in total acid and total phenols was evaluated by paired comparisons by 10 trained judges. Model solutions consisted of tannic (500, 1000, 2000 mg litre^?1) and tartaric (0, 2, 4, 6 g litre^?1) acids dissolved in aqueous solutions of ethanol (120 ml litre^?1) and sucrose (5 g litre^?1). Wine solutions were prepared by addition of citric acid (0, 0.5, 1, 2, 3 g litre^?1 as tartaric acid) to a high phenol-red wine (2645 mg litre^?1 GAE) and a moderate phenol-white wine (800 mg litre^?1 GAE). At all three levels of tannic acid, astringency of model solutions increased significantly (P<0.001) with tartaric acid concentration. Astringency of white wine also increased significantly (P<0.05) with citric acid concentration. A negative linear relation was found between relative astringency and pH at a given tannin level for both model solutions and white wine. As pH was reduced, more phenolic molecules were in the phenol form thereby increasing the likelihood of hydrogen bonding between hydroxyl groups of wine tannins and ketoimide groups of mouth proteins. The preliminary hypothesis that hydrogen bonding is the main reaction involved in the formation of protein-tannin complexes resulting in the sensation of astringency was reinforced.     

Determination of ascorbic acid in vegetables and fruits by differential pulse polarography

A method for the determination of ascorbic acid in vegetables and fruits using differential pulse polarography has been developed. The extraction medium recommended is a mixture of oxalic acid (1%), trichloroacetic acid (2%) and sodium sulphate (1%), and simple filtration is used to remove the residue. An acetate buffer (2M) is recommended to keep the pH at 4.5. The polarograms were recorded using a modulation amplitude of 50mV, a scan rate of 2mVs^?1, and a drop time of 1 s. The precision of the procedure was found to be 1.4% at the 1 mg litre^?1 level of ascorbic acid. The calibration graph was linear in the range of 0–20 mg litre ^?1 of ascorbic acid with a slope of 0.48μA mg litre^?1. Most common anions and cations did not interfere, however, Fe³⁺ and EDTA interfered, and Br^? and I^? seriously interfered with the determination. The method was applied to determine the ascorbic acid content of a number of vegetables and fruits using the standard-addition calibration.     

Injury,Inhibition and Inactivation ofEscherichia coli O157:H7 by Potassium Sorbate and Sodium Nitrite as Affected by pH and Temperature

The effect of potassium sorbate (0–2 g litre⁻¹) and sodium nitrite (0–1 g litre⁻¹) on the growth of four strains of Escherichia coli O157: H7 in tryptic soya broth at various pH levels (pH 4·0–7·0 for sorbate, pH 5·0–8·0 for nitrite) were determined at 37°C and 4°C. Among the pH levels tested, sorbate and nitrite exhibited the highest antimicrobial activity at pH 4·0 and 5·0, respectively. At pH 5·0 and 37°C, the presence of 500 mg litre⁻¹ sorbate or 200 mg litre⁻¹ nitrite completely inhibited the growth of E coli O157: H7. While at higher pH levels, 2 g litre⁻¹ sorbate or 1 g litre⁻¹, nitrite, the highest concentration tested, did not show significant antimicrobial action against the test organisms. At 4°C and pH 5·0, the inoculated test organisms did not showed any significant growth in preservative-free control media. Different degree of inactivation and injury was observed when E coli O157: H7 strain 933 was stored in TSB (pH 5·0) containing 1 g litre⁻¹ sorbate or nitrite at 37°C. At 4°C, inactivation and injury of E coli O157: H7 cells was not observed in the medium containing sorbate or nitrite throughout the 24 h experimental period.     

Automated analytical method for the determination of individual sugars in mixtures of glucose,fructose and sucrose

An automated colorimetric method, using p-hydroxybenzoic acid hydrazide and 2-thiobarbituric acid as colour reagents for the determination of total reducing sugars and fructose respectively, is described. The normal measurement range of reducing sugars is 50–1500 mg litre^?1, but with a simple modification of the autoanalyser arrangement it can be reduced to 1–30 mg litre^?1 or increased to 500–6000 mg litre^?1 without affecting the linearity of the calibration curve. Recovery of sugars by the known addition technique using this method range from 97 to 104%. The method is applicable for the joint determination of glucose, fructose and sucrose in fruits, vegetables and fermentation liquors.     

Effect of triacontanol on sprout growth in potatoes (Solanum tuberosum)

The effects of a 3-min dip in various concentrations (0–1–100 mg litre^?1) of a triacontanol emulsion on sprout growth from single-eye pieces of seed potato (Solanum tuberosum L) tubers were assessed after 10 days' growth in acid-washed sand. Treatment effects were compared with those resulting from immersion for 3 min in a mixture of gibberellic acid (6 mg litre^?1) and ethrel (4 mg litre^?1). Triacontanol dips were more effective than gibberellic acid and ethrel. Treatments increased the fresh weight of sprouts but had little effect on sprout number per tuber fragment. The optimum concentration of triacontanol was 10 mg litre^?1.     

Gamma irradiation as a means to eliminate Listeria monocytogenes from frozen chicken meat

Cells of Listeria monocytogenes ATCC 35152 were sensitive to gamma irradiation in phosphate buffer, pH 7.00 (D₁₀, dose required for 10% survival—0.15 kGy) at 0–5°C. The cells showed higher radiation survival when irradiated under frozen condition, with a D₁₀ of 0.3 kGy. The protection offered by shrimp/chicken/kheema homogenates (100 g litre^?1) was evidenced by even higher D₁₀ values (0.5 kGy) at both 0–5°C and cryogenic temperature. Boneless chicken meat samples were artificially inoculated with L monocytogenes ATCC 35152 cells at low (5 × 10³) colony-forming unit (cfu) g^?1 and high (5 × 10⁶ cfu g^?1) concentrations and irradiated at 1, 3, 4, 6 kGy doses under cryogenic conditions. The efficacy of the radiation process was evaluated by detecting L monocytogenes during storage at 2–4°C in the irradiated samples. These studies, when repeated with three other serotypes of L monocytogenes, clearly suggested the need for a dose of 3 kGy for elimination of 10³ cfu cells of L monocytogenes g^?1 from air-packed frozen chicken meat.     

Effect of drought and irrigation on the fate of nitrogen applied to cut permanent grass swards in lysimeters: Leaching losses

Nitrogen losses were measured in water draining from cut permanent grass swards growing in monolith lysimeters containing clay loam (Salop series) or silt loam (Bromyard series) soils. The swards were cut at 6-week intervals during the summer and were fertilised with calcium nitrate at rates of 0 and 400 kg N ha^?1 in each of five successive years (1977–81); in the first year the fertiliser was labelled with ¹⁵N. Four differing rainfall regimes were imposed from spring to autumn in each year. Mean annual losses of nitrogen by leaching from unfertilised swards were 3.8 kg N ha^?1 with mean nitrate-N concentrations in the water of about 1 mg N litre^?1. In fertilised lysimeters where rainfall distribution was that of the long-term average the mean annual total nitrogen losses were 41 kg N ha^?1 in the Salop soil and 15 kg N ha^?1 for the Bromyard soil; mean nitrate-N concentrations were 11.6 mg N litre^?1 and 5.1 mg N litre^?1, respectively. Losses of nitrogen and nitrate concentrations were similar to these quantities when irrigation increased the rainfall total to 120% of average. Where a drought was imposed for 2 weeks before and after each cut, mean nitrate-N concentrations increased to 20.3 mg N litre^?1 on Salop soil and 13.1 mg N litre^?1 on Bromyard soils; total annual nitrogen losses were 74 kg N ha and 33 kg N ha^?1, respectively. The largest losses were recorded when the drought period extended for four weeks before each cut and mean nitrate-N concentrations increases to 28.8 mg N litre^?1 on Salop soil and 34 mg N litre^?1 on Bromyard soil, with total annual nitrogen losses of 104 kg N ha^?1 and 109 kg N ha^?1, respectively. Losses of nitrogen derived from the fertiliser labelled with ¹⁵N were 7.3–8.4% of that applied in the Salop soil (29–33 kg N ha^?1), with little effect by the differing rainfall distributions. On the Bromyard soil, losses were 3.7% (14 kg N ha^?1) of the applied fertiliser in lysimeters not subjected to droughts. When the period of the drought extended before and after each cut, losses were 8.2% (32 kg N ha^?1) and increased to 17.9% (70 kg N ha^?1) when the drought period occurred entirely before each cut. Fertiliser nitrogen contributed 48–69% of the total nitrogen in drainage water from both soils in the first year.     

Lead and arsenic levels in wines produced from vineyards where lead arsenate sprays are used for caterpillar control

Twenty-seven dry table wines from 14 wineries throughout Victoria were analysed for lead and arsenic. Wines originating from vineyards using lead arsenate insecticide for caterpillar control had mean levels of 0.31 mg litre^?-1 lead and 0.08 mg litre^?-1 arsenic. The mean levels in similar wines from wineries not using lead arsenate sprays were 0.03 mg litre^?-1 and less than 0.01 mg litre^?-1 respectively.     

The effects of urea and artificial saliva on rumen bacterial protein synthesis in sheep receiving a high-cereal diet

Four sheep fitted with cannulas in the rumen and duodenum and given a basal diet of 18% chopped hay, 41% rolled barley and 41% flaked maize, known to be associated with low rates of bacterial protein synthesis in the rumen, were used in a 4 × 4 Latin Square experiment to study the effects of continuous intraruminal infusions of water (2 litres day^?1; control), urea solution (7.5 g urea litre^?1, 2 litres day^?1; urea), artificial saliva (4 litres day^?1; saliva) and artificial saliva with added urea (3.75 g urea litre^?1, 4 litres day^?1; saliva+urea) on rumen ammonia-nitrogen concentration, pH, liquid clearance rates and bacterial protein synthesis. Rumen ammonia-nitrogen concentrations for control, urea, saliva and saliva + urea treatments were 81, 158, 38 and 151 mg litre^?1, respectively. Corresponding mean values for rumen pH were 6.18, 6.09, 6.37 and 6.41 units and for rumen liquid clearance rates 0.082, 0.057, 0.062 and 0.051 h^?1. The mean rate of bacterial protein synthesis in the rumen, estimated from the duodenal entry of α-?-diaminopimelic acid, for the control treatment was 163 g crude protein (CP) kg^?1 organic matter (OM) apparently digested in the stomach. Corresponding rates for the saliva and saliva + urea treatments were 169 g CP kg^?1 OM apparently digested and 215 g CP kg^?1 OM apparently digested, indicating responses in protein synthesis to the urea+saliva treatment but not to the saliva alone treatment. Infusion of urea solution increased the mean rate of protein synthesis to 204 g CP kg^?1 OM apparently digested in the stomach but the responses were variable between animals and in three of the animals were small. It is concluded that with the type of diet used an enhanced entry of saliva into the rumen is necessary to ensure that supplementary urea produces a consistent improvement in ruminal protein synthesis.     

The effects of defaunation on the metabolism of lactic acid in the rumen

Two experiments examined the effects of defaunation on the ruminal metabolism of lactate. Three rumen-cannulated sheep given a diet of molassed sugar beet pulp and barley (80:20) were used to study the effects of defaunation (with manoxol-OT) on the metabolism of lactic acid produced endogenously from rumen fermentation. Defaunation increased mean ruminal concentrations of lactate from 3.4 mmol litre^?1 to 8.9 mmol litre^?1 but other rumen measurements remained virtually unchanged: pH, 6.3 and 6.3; molar proportions of acetic acid, 645 and 645 mmol mol^?1; propionic acid, 189 and 197 mmol mol^?1 and butyric acid 142 and 115 mmol mol^?1 for the faunated and defaunated states respectively. In a second experiment, two groups each of four rumen-cannulated sheep were used to study the effect of defaunation on the ruminal metabolism of added Na-D, L lactate. One group of four was defaunated using a rumen-washing technique whilst the other group of four remained faunated. The animals were given a diet of rolled barley and hay (60:40) and were given a series of intraruminal doses of Na-D, L lactate from 0 to 100 g day^?1, increasing by 20 g day^?1 every third day. Disappearance of added lactate was much more rapid in faunated animals: at the 100 g day^?1 dose rate, L-lactate concentrations had fallen from a peak of 6 g litre^?1 to >1 g litre^?1 after 3 h whereas in defaunated sheep the peak of 6.5 g litre^?1 was reduced to >1 g litre^?1 only after 7 h. In faunated animals lactate addition caused an increase in the ruminal concentration of total volatile fatty acids (VFA) from 147 to 217 mmol litre^?1 between the zero and 100 g day^?1 dose rates, accompanied by an increase in the molar proportion of propionic acid from 190 to 320 mmol mol^?1. However, in defaunated animals there was only a small increase in total VFA concentrations from 94 to 106 mmol ml^?1 with no change in the molar proportion of propionic acid and a small increase in butryric acid from 140 to 180 mmol mol^?1.     

The influence of solution concentration of aluminium,arsenic, boron and copper on root growth in relation to the phytotoxicity of pulverised fuel ash

To find whether the concentrations of aluminium, arsenic, boron or copper and soluble sulphate salts which have previously been found in the aqueous phase of water saturated pulverised fuel ash (PFA) are sufficiently high to restrict growth, lettuce seedlings were grown on filter paper saturated with a solution containing various concentrations of each of the different ions. Over a period of five days root growth was reduced by half when the concentration of aluminium was increased to 2.0 mg/litre, arsenic (As³⁺) to 1.6 mg/litre, boron to 90 mg/litre or copper to 0.3 mg/litre or when the soluble sulphate salts were increased to 100 mEq/litre (conductivity 8 × 10^?3 ohm^?1 cm^?1 at 20°C). The concentrations of ions in the aqueous phase of wet PFA depend on pH which varies greatly from one batch of ash to another. The concentrations of aluminium and copper in equilibrium with acid batches of ash and those of arsenic in equilibrium with alkaline batches of ash were sufficiently high to restrict growth. The concentrations of boron and soluble salts were always at phytotoxic levels irrespective of the pH of the ash.