Physico-chemical aspects of the vaailability of pesticides in soil. II. Controlled release of pesticides from granular formulations

The extent to which formulation factors control the release of a toxicant from granular formulations, under the leaching action of rain, has been investigated. Using granules prepared by an agglomeration process and containing the herbicide chlorthiamid, the rate of release can be varied by changing the filler base and by the use of different binding agents. By varying the binding agent a considerable degree of control can be exercised over the release of chlorthiamid. The release of toxicant is partly by direct leaching from the granule and partly by disintegration of the granule in water which renders the toxicant more accessible. The extent to which the release of other toxicants may be controlled in a similar way has been examined using ‘Bidrin’, fenuron, 2,4-D, chlorfenvinphos and N-tritylmorpholine. Toxicant release appeared to be governed by the filler/binding agent combination used in the granule and by the water solubility of the toxicant. Where the toxicant solubility is high, control over release is difficult to achieve but where the solubility is below 2000 ppm, a considerable control is possible.     

The Starch of Amaranthus — Physico-chemical Properties and Functional Characteristics

Starch from four varieties of amaranth grain were examined by scanning electron microscopy. Physico-chemical properties, including swelling power, solubility, water binding capacity, enzyme susceptibility, amylograph viscosity, and amylose, were determined. Functional characteristics, including bread and cake baking performance were studied. The granules of starch isolated from seeds of Amaranthus cruentus and Amaranthus hypochondriacus were found to be very small in size. They were angular and polygonal in shape. Compared to corn starch, the amaranth starches had a higher swelling power, a lower solubility, a greater water binding capacity, a lower susceptibility to α-amylase, a higher amylograph viscosity and much lower amylose content. The amaranth starches produced very poor quality breads and cakes. The breads and cakes were low in volume, lacked symmetry, and had inferior grain, texture and crumb color.     

Pesticides residues in foodstuffs in Great Britain. VI.—Mercury residues in rice

Analyses of samples of rice from United Kingdom importers and from retail sources show that levels of mercury are often negligible, although they may rise to 0.01 ppm and occasionally to 0.015 ppm.     

Texture of cooked potato I.—Introduction

The literature describing the relationships between texture and chemical composition of the tuber is discussed.     

Available lysine. I.—Determination of non-N-terminal lysine in protein

An improved quantitative method for estimating ?-DNP-lysine is described. This method is applied to the determination of ?-DNP-lysine produced by the hydrolysis of dinitrophenylated proteins. The effect of the conditions of hydrolysis and of traces of chromic acid present during hydrolysis is presented. The use of dinitrophenylation as a method of determining non-N-terminal lysine was tested on three purified proteins and the results are discussed.     

Physico-chemical studies on agricultural sprays VIII.—Viscosity and spray drop size of water-in-oil emulsions

The effect of the viscosity of the spray fluid on the size of drops produced from fan-jet nozzles is complex; an increase in viscosity can lead to either an increase or a decrease in the drop size. With water-in-oil emulsions the value of the viscosity governing spray behaviour is the limiting value measured under conditions of very high shear. The factors which influence the limiting value of the viscosity include the disperse phase ratio, the method of mixing and the degree to which the two phases are mixed, the nature and concentration of the emulsifying agents used and the type of toxicant incorporated in the emulsion. Within certain limits, it is shown that the disperse phase ratio provides a convenient means of varying the viscosity of the emulsions and that the viscosity may also be varied by variations in the emulsifying agents and toxicants. Although the method of mixing has a considerable effect on the viscosity of the emulsion, the further mixing that takes place in the spray nozzle governs the effective viscosity of the spray fluid that is emitted from the nozzle. The practical application of the theoretical expressions which describe the formation of drops from fanjet nozzles has been discussed and the relationship between disperse phase ratio, viscosity, nozzle size and operating pressures has been illustrated for several typical water-in-oil emulsions.     

Synthesis and pesticidal evaluation of phenazines I.—Halophenazines

The synthesis and biological activity of twenty-six halophenazines is described. the Wohl-Aue reaction and the new method for cyclisation of 2-nitrodiphenylamines by oleum were found to be the most convenient methods of synthesis. Phytotoxicity of a characteristic type was higher in foliar spray than in pre-emergence tests. Chlorine substitution appeared to confer higher activity than other halogen substituents, and in the chlorophenazines activity decreased with increasing substitution. Both 1-and 2-chlorophenazine were highly effective herbicides. Acaricidal and fungicidal activity showed similar responses to structural changes, and optimum activity, together with a low level of phytotoxicity, was reached with 1, 4-dichlorophenazine.     

Breakdown of the herbicide 14C-chlorthiamid I.—Laboratory studies of the breakdown in soils

Chlorthiamid (‘Prefix’, 2,6-dichlorothiobenzamide) with a ¹⁴C label was added at 10 ppm (on a wet weight basis, equivalent to nearly 20 lb/acre) to moist clay, loam, peat, sand, and brick earth in tightly stoppered bottles. After six months at room temperature (22°) all of the chlorthiamid had broken down. The major products were 2,6-dichlorobenzamide (3-8 ppm), and dichlobenil (‘Casoron’, 2,6-dichlorobenzo-nitrile, 0.8-3.7 ppm) together with traces (0.6 to < 0.01 ppm) of two unidentified compounds. No 2,6-dichlorobenzoic acid could be detected in the soils. Whilst dichlobenil is an active herbicide the benzamide is only weakly active.     

The differential determination of lysine in heated milk. I.—In vitro methods

Lysine content and availability were determined in a set of milk samples which had sustained increasing heat treatments. Lysine content was measured after acid hydrolysis of the sample (TLV or x-value), lysine availability by an enzymic digestion procedure (ALV-e or y-value) and by two modifications of the fluorodinitrobenzene method: the direct method (ALV-f I or z-value) and Carpenter's corrected straight acid procedure (ALV-f II or v-value). The four procedures gave strongly correlated, but numerically quite different results. The enzymic procedure and Carpenter's chemical method produced very similar results for lysine availability. In all heated samples, lysine content was much higher than lysine availability. The direct fluorodinitrobenzene method yielded values intermediate between those for lysine content and ‘true’ lysine availability. A nomograph is presented which accounts for the different conditions of lysine in heated milk and allows the interconversion of the x, y, z and v-values.     

Pink discoloration in canned pears I.—Role of tin in pigment formation

The major pigment in discoloured canned pears is identified as a purple-pink insoluble tin-anthocyanin complex from the effect of reagents for anthocyanins on the spectra of solid and syrup fractions of the product. This characterisation is supported by significant correlations between the intensity of reflected colour and the insoluble tin content of the solid fraction. It is suggested that formation of a tin complex is essential for the occurrence of pink discolorations in canned pears, and experiments are described designed to vary the intensity of discoloration by modifying the conditions controlling complex formation.     

Annealing of Granular Rice Starches — Interpretation of the Effect on Phase Transitions Associated with Gelatinization

The effects of annealing on phase transitions associated with gelatinization at different moisture contents of an atypical non-waxy rice starch exhibiting a clearer-than-usual glass transition were studied by differential scanning calorimetry. Consistent with observations on synthetic glassy polymers, annealing at temperatures below the glass transition for limited periods caused an elevation of T_g which is attributed to the slow relaxation of the amorphous regions of the starch granules to their equilibrium glassy states. The crystalline regions were significantly affected only after annealing at temperatures above the glass transition, the resulting increase in crystallite melting temperatures and narrowing of the gelatinization range being ascribed to crystal growth and/or perfection. Passage through the glass transition (which precedes crystallite melting) appears to give rise to an apparent endotherm which becomes even more prominent on sub-T_g annealing of samples at low moisture contents. Annealing of an ordinary rice starch (with no clearly discernible glass transition) at a temperature below its onset gelatinization temperature (T₀) produced effects which paralleled those observed after sub-T_g annealing of the atypical rice starch. The conclusion drawn is that a glass transition is superposed on the crystalline melt at the leading edge of the single endothermic peak observed at high moisture contents. Where biphasic endotherms at intermediate moisture levels are concerned, however, the present results suggest that the first or G endotherm very likely arises from a glassy-to-rubbery state transformation while the second or M₁ endotherm is associated with crystallite melting.     

Deterioration of β-carotene in certain hydrogenated fats. I.—Incidence of green discoloration during storage

An investigation of the stability of β-carotene in 111 samples of hydrogenated edible fats revealed that during storage at temperatures in the range of +20° to —20°, green discoloration of the yellow fats occurred in 38 samples during the first year of storage. The green discoloration was found mostly in hydrogenated palm kernel oil and coconut oil; samples of hydrogenated marine and soyabean oils were much less susceptible to colour change. The rate of development of the colour change was generally a maximum in the temperature range +6° to —6° and decreased rapidly as the temperature was raised.     

Freeze-drying of raw beef I.—Influence of some raw material variables

The effect of raw material variables, such as breed, sex, age, fat content of muscle and ageing time, upon the quality of the reconstituted product were studied in multifactorial experiments of a preliminary nature. The effects observed were in fair agreement with general experience with unprocessed raw beef and with the limited published data for reconstituted freeze-dried raw beef.     

Ensilage of whole-crop barley. I.—Effects of variety and stage of growth

The chemical composition and nutritive value of each of eight varieties of barley were examined at seven stages of growth. There were differences between some varieties at certain stages of growth but these were small. Dry matter content increased with increasing maturity while water-soluble carbohydrate content increased to the milky ripe stage and then fell sharply. In vitro organic matter digestibility was a maximum at the mealy ripe stages of growth. The optimum stage of growth for cutting barley for ensilage is discussed. Silage was made from barley cut at the early mealy ripe stage of growth, in small tower silos. There was no effluent, and fermentation losses were low. The in vivo digestibility of the silage organic matter was 65.5%.     

Stability of agricultural chemicals. I.—Hydrolytic and thermal stabilities of phosphorylated crotonamides

The chemical stability of organo-phosphorus insecticides is important in determining both the shelf life of their formulations and their rates of decay after application. In common with most organic esters, they are liable to hydrolyse and their stability is considerably impaired by increase in temperature. The hydrolysis of 3-(dimethoxyphosphinyloxy)-N, N-dimethyl-cis-crotonamide (‘Bidrid’*) and the corresponding N-monomethyl derivative (‘Azodrin’*) has been examined at various temperatures and under various pH conditions. Rate constants have been calculated and indicate that the alkaline hydrolysis occurs much more rapidly (approximately 17 times) than acidic hydrolysis. The breakdown mechanism differs between the two cases; acidic hydrolysis produces as its main decomposition products methylphosphoric acid and N-mono- or N, N-di-methylacetoacetamide while alkaline hydrolysis produces dimethyl phosphate, methyl alcohol and acetone. Both materials are highly susceptible to increase in temperature and the rates for this decomposition and their significance have been studied. Both the nature of the decomposition products and the rate of thermal breakdown are affected considerably by small quantities of water and free acid in the insecticide. The results are discussed in relation to the existing literature on the decomposition of organo-phosphorus insecticides and a mechanism of thermal breakdown for both materials is suggested.     

The in vitro hydrolysis of leaf proteins. I.—The action of papain on protein extracted from the leaves of Zea mays

Maize leaf protein is not digested by papain at 37°, under conditions in which casein is hydrolysed. An increase in temperature has more effect on both the initial rate of reaction, and the final amount of hydrolysis, than an increase in enzyme concentration. Maximum digestion is observed at pH 6-6 and 70° using KCN-activated papain: 70% of the substrate N is hydrolysed to non-protein N. De-fatting of the protein by neutral solvent mixtures results in only a slight increase in digestion. Soluble N-containing fractions precipitable by TCA occur at all pH values, but most at pH 7.5 and above. Digestion leads to almost complete solution of the leaf protein at pH 8.6 but the percentage of hydrolysis never exceeds that at pH 6.6. These soluble fractions resemble those found in similar digests of seed proteins. Though in vivo experiments show that protein made from mature wheat leaves has a higher nutritive value than protein from young leaves, there is no corresponding increase in the in vitro digestibility of protein extracted from maize leaves of increasing maturity.     

Investigations on starches from major starch crops grown in Ghana I.—Hot paste viscosity and gel-forming power

The most important rheological properties of starches of several major starch crops grown in Ghana were examined. the consistency changes during the whole pasting cycle and the gel-forming power were tested with starches of several species of yams (Dioscorea), plantain (Musa paradisiaca) cultivars, cocoyams (both Xanthosoma sagittifolium and Colocasia antiquorum) and several local varieties of cassava (Manihot utilissima). Most of the yam starches gave very viscous pastes yielding very strong and ‘short’ gels on cooling, some of them with a very high retrogradation tendency. the rheological properties of plantain starches were similar to those of yam starches; cocoyam starches produced pastes which had lower viscosity and exhibited some breakdown on prolonged heating and stirring and a poorer setback on cooling. With ‘new’ cocoyam (Xanthosoma sagittifolium) the gel-forming power, however, was higher than that of cassava and sweet-potato starches.     

Evaluation of carrot varieties for production of deep fried carrot chips — II. Sensory aspects

Carrot variety had a significant (P ≤ 0.0005) influence on colour, sweet taste, fruity taste, acid taste, bitter taste, earthy taste, juiciness and crispness, while cultivation site (environmental conditions) had a significant (P ≤ 0.0005) influence on colour, sweet taste, bitter taste, earthy taste, aftertaste, juiciness and crispness. Sensory attributes of raw carrots could predict the quality of carrot chips by means of two factors when PLS has been applied. Factor 1 was explained mainly by cultivation site, but also by variety, while factor 2 was explained by variety.     

Soil salinity studies. II.—The relation of plant growth to salinity in soil and soil mixtures of differing physical properties

Lettuce plants were grown at six levels of salinity in soil and in mixtures of soil with peat and sand. Soil salinity was determined in saturation pastes and paste extracts, and in 2.5 : 1 extracts prepared by weight and by volume, with and without added calcium sulphate. The correlations between plant growth (fresh weight) and salinity were calculated from two sets of data, each based on four lettuce crops. Sampling by volume rather than by weight for salinity measurements improved the correlations with growth, and gave a reasonably satisfactory measure of salinity over the range of growth media examined (bulk density 0.82-1.37 after air-drying and grinding). Still higher correlations resulted (r = —0.95 to —0.98) when corrections were applied for differences in bulk density. It is concluded that 2.5: 1 extracts prepared by volume, saturated with calcium sulphate and corrected where necessary for bulk density, can provide a rapid and reliable estimate of high salinity levels in soils differing considerably in moisture-retaining properties.