Physico-chemical aspects of the availability of pesticides in the soil. I.—Leaching of Pesticides from Granular Formulations

The way in which a pesticide is leached from a granular formulation differs from the way in which it is leached from a spray or dust formulation. This difference arises because granular applications do not provide the uniformity of coverage of the soil surface attainable with applications of finely divided sprays and dusts. This means that, besides the climatic factors such as temperature and quantity and intensity of rainfall that affect leaching, with granular formulations the distribution of granules over the soil is equally important. Thus the quantity of pesticide applied, the granule size, the pesticide content of the granules and their density may all affect the rate at which a pesticide is leached from the formulation. The inter-relation between these factors has been considered theoretically and the theoretical conclusions have been tested using granules prepared by agglomeration and containing the herbicide ‘Prefix’ (2,6-dichlorothiobenzamide). The effect of solubility of the pesticide in water has been studied using various pesticides having a range of water solubilities. As expected, the results show that the rate at which the pesticide is leached depends upon its solubility, but that the extent to which the granules break down under the influence of water can also be important.     

Resistant starches. Part II. Physico-chemical and technological aspects solution medico-biological problems

This paper is a review of the recent literature data related to structure, composition and physico-chemical properties of starches as well as the special methods of processing of the starch containing raw sources producing the food products with increasing content of resistant starches. The prognosis is made about usefulness of such resistant starches for control of some metabolic disorder in human organism and for prophylactic aims.     

Facilitated transport of dioxins in soil following unintentional release of pesticide-surfactant formulations

Colloids such as surfactant micelles can act as transport facilitators for highly lipophilic, generally immobile contaminants in soil. Following a fire at a pesticide facility, this study investigated vertical and lateral migration of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in heterogeneous soil beneath bunded ponds, where contaminated wastewater containing high surfactant loads was stored until remediation. Initially, surface and subsurface soil was obtained during excavation, and subsequently intact cores to 5.7 m were collected. ΣPCDD/F concentrations were elevated in the wastewater (15-81 ng/L) and correspondingly in pond surface soils (6.1-61 ng/g). Maximum ΣPCDD/F concentrations were, however, observed at 2-2.5 m depth (68-130 ng/g), far below their expected mobility range based on physicochemical properties. Congener specific analysis further indicated that PCDD/F mobility was reversed, with the least water-soluble congener migrating to the greatest extent. The presence of higher chlorinated PCDD/Fs throughout a core collected in the direction of groundwater flow indicated subsequent lateral transport. These results provide field evidence for rapid vertical migration (2.4 m in <4 months) of highly lipophilic PCDD/Fs and suggest surfactant facilitated transport as the dominant transport mechanism. Quantification and evaluation of such fundamental changes in contaminant transport and fate in the presence of surfactants is required to identify areas at risk of groundwater contamination.     

Controlled release of dehydroacetic acid sodium salt for the stability improvement of cosmetic formulations*

The kinetics of decomposition of the sodium salt of dehydroacetic acid (DHA.Na) in presence of formaldehyde and formaldehyde donors was investigated. The possibility of preparing systems capable of providing the cosmetic preparation with increasing amounts of DHA.Na corresponding to portions interacted with formaldehyde was explored. Data relevant to matrices prepared from ethylcellulose and polyethylene by casting and moulding process, respectively, are reported and discussed. Experimental data demonstrate the possibility of preparing polymeric systems able to control in terms of rate and duration the relase of DHA.Na, according to time and concentration needs of a typical cosmetic formulation.     

Controlled release of thymol from zein based film

Active packaging materials, able to release antimicrobial compounds into foodstuffs, can be used in order to inhibit or slow down bacterial growth during storage. Zein-based mono and multilayer films were loaded with spelt bran and thymol (35% w/w) to obtain edible composite polymeric materials. Various composite systems were developed to control the release of thymol. In particular, the thickness of the layers and the biodegradable fibres amount were varied. Results highlight that thymol release rate decreased with the increase of the film thickness for both mono and multilayer films, without spelt bran addition. Conversely, a significant increase of thymol release rate with the increase of the bran concentration is recorded for both mono and multilayer films.Industrial relevanceIn recent years, food safety is an important area of concern to the food industry. This fact requires packaging to be an integral part of the preservation concept. Consequently additional antimicrobial activity from the packaging material can aid in shelf life extension. The present work is focused on the development of controlled release systems based on zein incorporated with an active compound, thymol and natural fibres. Release rate of thymol from the developed mono and multilayer films, as affected by layers thickness and fibres amount, was evaluated.     

Controlled release of antimicrobial compounds from highly swellable polymers

The suitability of antimicrobial release films made from highly swellable polymers for use in food packaging was evaluated. The possibility of modulating the release kinetics of active compounds either by regulating the degree of cross-link of the polymer matrix or by using multilayer structures was addressed. The release kinetics of lysozyme, nisin, and sodium benzoate (active compounds with different molecular weights) were determined at ambient temperature (25 degrees C). The effectiveness of the proposed active films in inhibiting microbial growth was addressed by determining the antimicrobial efficiency of the released active compounds. Micrococcus lysodeikticus, Alicyclobacillus acidoterrestris, and Saccharomyces cerevisiae were used to test the antimicrobial efficiency of released lysozyme, nisin, and sodium benzoate, respectively. Results indicate that the release kinetics of both lysozyme and nisin can be modulated through the degree of cross-link of the polymer matrix, whereas multilayer structures need to be used to control the release kinetics of sodium benzoate. All the active compounds released from the investigated active films were effective in inhibiting microbial growth.     

Organochlorine pesticides in agricultural soil and vegetables from Tianjin, China

Samples of eight types of vegetables, the rhizosphere soils, and bulk soils were collected from two sites (A and B) in Tianjin, China for the determination of hexachlorocyclohexane isomers (HCHs) and dichlorodiphenyltrichloroethane and metabolites (DDXs). The average concentrations of total HCHs and DDXs in the bulk soils were 3.6 and 80.1 ng/g for site A and 102 and 235 ng/g for site B, respectively. Relative accumulations of HCHs and DDXs in the rhizosphere soil from site A but not site B were demonstrated. The concentrations of total HCHs and DDXs in vegetable roots were 3.6-60 and 4.2-73 ng/g for site A and 15-152 and 7.1-136 ng/g for site B, respectively. Difference in bioaccumulation among various vegetables, especially between tuber and fibrous vegetables was significant. DDXs in spinach and cauliflower from site B and lindane (gamma-HCH) in cauliflower from both sites and violet from site B exceeded the maximum residual limits. Linear correlation of log-transformed HCHs and DDXs contents between the vegetable roots and the rhizosphere soils suggests the direct uptake of HCHs and DDXs.     

Physico-chemical properties of skim milk retentates from microfiltration.

Physico-chemical properties of retentates obtained from selective concentration of skim milk up to 8 times its original weight using a microfiltration system were studied. The effects of process variables, namely concentration (8.6 to 27 wt.%), temperature (20 to 50 degrees C) and pH (6.0, 6.3, and 6.5) on density (rho), apparent viscosity (mu(a)), consistency coefficient (K), flow behavior index (n), and activation energy (Ea) of the retentates were examined. Depending on pH, retentates showed significant increase in apparent viscosity, deviated from classical Newtonian behavior and exhibited shear-thinning between 11 to 17% solids concentration. No yield stress was detected in the range of concentration studied. The power law parameters (n and K) followed a similar trend. An Arrhenius-type equation described well the effect of temperature on apparent viscosity. Although activation energy increased 120 to 130% for a threefold increase in solids concentration, it was not significantly different from that of other types of concentrated milk at approximately the same concentration. Increasing solids were responsible for change in flow properties with concentration, while the effect of pH was attributed to differential protein (primarily casein) retention and the change in solvation properties and voluminosity of casein micelles. Models relating concentration, temperature, and pH to retentate apparent viscosity and consistency coefficient were identified. Skim milk microfiltration with in-process pH adjustment produces retentates depleted in whey proteins and calcium with significantly altered properties.     

Kinetics of contaminant desorption from soil: comparison of model formulations using the Akaike information criterion

Desorption of organic contaminants from soil can be modeled by dividing the desorption time-concentration profile into three distinct regimes. These are characterized by desorption that occurs faster than the experimental sampling scheme, at a rate that is captured by it, and at a rate for which the duration of the experiment and data uncertainty obscures the rate. Batch desorption curves for atrazine and naphthalene on four soils were experimentally generated to demonstrate the existence of discrete observational desorption regimes. Nine mathematical models, each containing mechanisms formulated to describe at least one of the three regimes, were fit to each contaminant-soil combination using the Gauss-Newton method for parameter estimation. Each of the nine models was ranked using the small-sample-corrected Akaike information criterion (AICc). By interpretation of the AICc values, the atrazine desorption data were best described by three regimes, while the naphthalene desorption data were best described by two regimes. Furthermore, for a given number of regimes, we could find no general basis to suggest that a particular type of rate model (chemical, physical, kinetic, or statistical) is intrinsically superior over another.     

Modeling spatial variation in microbial degradation of pesticides in soil

Currently, no general guidance is available on suitable approaches for dealing with spatial variation in the first-order pesticide degradation rate constant k even though it is a very sensitive parameter and often highly variable at the field, catchment, and regional scales. Supported by some mechanistic reasoning, we propose a simple general modeling approach to predict k from the sorption constant, which reflects bioavailability, and easily measurable surrogate variables for microbial biomass/activity (organic carbon and clay contents). The soil depth was also explicitly included as an additional predictor variable. This approach was tested in a meta-analysis of available literature data using bootstrapped partial least-squares regression. It explained 73% of the variation in k for the 19 pesticide-study combinations (n = 212) in the database. When 4 of the 19 pesticide-study combinations were excluded (n = 169), the approach explained 80% of the variation in the degradation rate constant. We conclude that the approach shows promise as an effective way to account for the effects of bioavailability and microbial activity on microbial pesticide degradation in large-scale model applications.     

Controlled release of thiram pesticide from poly (L-lactic acid) nanofibers

Controlled release of pesticides is eco-friendly and cost-effective. Thiram is a pesticide for fighting fungi and protection of cultivated products. This research aimed at controlled release of thiram pesticide from Poly (L-lactic acid) (PLLA) nanofibrous matrix. Solutions of PLLA (9% w/v) in chloroform-methanol (80–20 v/v) containing 5, 10, 15, 20, and 25% (w/w) thiram relative to the PLLA were electrospun. FESEM, FTIR, and XRD were employed to characterize the electrospun nanofibers. UV spectrophotometry was employed to study the release of thiram from PLLA nanofibers in deionized water. The results showed that the controlled release of thiram from PLLA nanofibers without annealing followed Fick mechanism, but after annealing, non-Fick mechanism prevailed. It was also observed that annealing led to lower level and lower initial rate of controlled release. It is concluded that electrospun PLLA-thiram nanofibers can be used for the controlled release of thiram in long-term periods in agriculture.     

Controlled release of Doxorubicin embedded in carboxymethyl chitosan nanofibers

This paper reports the fabrication of carboxymethyl chitosan (CMCH) nanofibers containing Doxorubicin anti-cancer drug and studies the controlled release of Doxorubicin from the electrospun nanofibrous CMCH matrix. CMCH-Doxorubicin nanofibrous mats were electrospun from solutions containing 16.7, 25 and 34% (W/W) Doxorubicin. The diameter of the electrospun nanofibers lied in the range of 390–460 nm. It was found that increasing the share of Doxorubicin leads to higher diameter of the electrospun nanofibers. Fourier transform infrared spectroscopy analysis showed no reaction between Doxorubicin and carboxymethyl chitosan. X-ray diffractions showed that Doxorubicin was distributed as crystallites in the crystalline CMCH matrix. High performance liquid chromatography investigations proved that CMCH nanofibers containing Doxorubicin have the capability of controlled release of the drug. It was also found that depending on the amount of Doxorubicin in the CMCH matrix, the release of the drug occurs according to non-Fick or Fick diffusion mechanism.     

New aspects on the chemistry of tea and coffee. II

Zusammenfassung Als Fortsetzung der Übersicht aus den Jahren 1982/1983 werden nunmehr neuere Veröffentlichungen aus den Jahren 1983/1984 zur Chemie und Technologie von Tee (Blatt, grün und schwarz) und Kaffee (roh, geröstet und instantlöslich) referiert, besonders über die Veränderung der Zusammensetzung während der Herstellung und Lagerung und der Einfluß der Zusammensetzung auf die Qualität der Getränke (155 Referenzen).

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New aspects on the chemistry of tea and coffee. II

Summary As a continuation of the previous review for 1982/83, recent publications (1983/1984) on the chemistry and technology of tea (leaf, green and black) and coffee (raw, roasted and instant), with particular reference to composition and changes during manufacture, and the effects of composition on the quality of the beverage are now reviewed (155 references).

     

Occurence of pesticides in fish tissues,water and soil sediment from Manzala Lake and River Nile

Pesticides constitute the major source of potential environmental hazard to man and animal as they are present and concentrated in the food chain. This study was conducted on 136 samples of water, sediment and fish for detection and determination of pesticide residues in this ecosystem. Highly significant differences were found in levels of lindan, heptachlor, endrin, dieldrin, P,P′-DDE and propoxur in River Nile water when compared with that of Manzala Lake. Levels of lindan, endrin, malathion and diazinon were significantly higher in soil sediment of Manzala Lake, while the levels of heptachlor, aldrine, P,P′-DDE, DDT, parathion, propoxur and zectran were significantly higher in soil sediment of River Nile. Boury fish of Manzala Lake contained higher levels of heptachlor, aldrin, P,P′-DDE and malathion, while boury fish of River Nile contained a higher level of zectran only. This survey, thus indicated that Manzala Lake and even the River Nile which was used as control are heavily contaminated with chlorinated hydrocarbons (lindan, heptachlor, aldrin, endrin, dieldrin, P,P′-DDE and DDT), organic phosphorus compounds (malathion, dimethoat, diazinon and parathion) and carbamate pesticides (propoxur and zectran).     

Controlled production of Camembert-type cheeses. Part II. Changes in the concentration of the more volatile compounds

Flavour generation in cheese is a major aspect of ripening. In order to enhance aromatic qualities it is necessary to better understand the chemical and microbiological changes. Experimental Camembert-type cheeses were prepared in duplicate from pasteurized milk inoculated with Kluyveromyces lactis, Geotrichum candidum, Penicillium camemberti and Brevibacterium linens under aseptic conditions. Two replicates performed under controlled conditions of temperature (12 degrees C), relative humidity (95 +/- 2%), and atmosphere showed similar ripening characteristics. The evolutions of metabolite concentrations were studied during ripening. The volatile components were extracted by dynamic headspace extraction, separated and quantified by gas chromatography and identified by mass spectrometry. For each cheese the volatile concentrations varied with the part considered (rind or core). Except for ethyl acetate and 2-pentanone, the volatile quantities observed were higher than their perception thresholds. The flavour component production was best correlated with the starter strains. During the first 10 days the ester formations (ethyl, butyl and isoamyl acetates) were associated with the concentrations of K. lactis and G. candidum. The rind quantity of esters was lower than that observed in core probably due to (1) a diffusion from the core to the surface and (2) evaporation from the surface to the chamber atmosphere. G. candidum and Brev. linens association produced 3 methyl butanol and methyl 3-butanal from leucine, respectively. DMDS came from the methionine catabolism due to Brev. linens. Styrene production was attributed to Pen. camemberti. 2-Pentanone evolution was associated with Pen. camemberti spores and G. candidum. 2-Heptanone changes were not directly related to flora activities while 2-octanone production was essentially due to G. candidum. This study also demonstrates the determining role of volatile component diffusion.     

Physico-chemical properties in honey from different regions of Turkey

The present study was undertaken to determine the physico-chemical parameters of honey samples obtained from retailers in Marmara Region (Site 1) and East Anatolia (Site 2) of Turkey. The 70 samples were analysed for parameters including moisture, total acidity, diastase activity, hydroxymethylfurfural (HMF), invert sugar, sucrose, ash, commercial glucose and starch. 10 of 70 (14.3%) honey samples were of unacceptable quality based on recommended criteria of moisture (3 of 70, 4.29%), diastase activity (3 of 70, 4.29%), HMF (2 of 70, 2.86%), invert sugar (4 of 70, 5.71%) and sucrose (2 of 70, 2.86%) by Turkish Food Codex and European Commission Regulation. The results of study indicated that 85.7% of honey samples were at good quality. It is important that the essential precautions should be taken to ensure standardisation and rationalisation of beekeeping techniques, manufacturing procedures and storing processes to improve honey quality.     

Controlled release of sorbic acid from bacterial cellulose based mono and multilayer antimicrobial films

Biodegradable bacterial cellulose (BC) based films, incorporating sorbic acid (SA) as antimicrobial agent, have been obtained. Monolayer films, prepared using powdered BC (BCP) and poly(vinyl) alcohol (PVA), were coated with BC membrane to obtain multilayer films. Tests indicated that both SA and BCP concentration influenced sensitivity to water, release rate and antimicrobial ability of mono and multilayer films. Swelling degree, water vapour permeability and water solubility increased with SA content, but decreased with BCP addition. However in case of multilayer films, water solubility was negligible. Colour measurements indicated no degradation of SA during film preparation. The release of SA was faster when BCP concentration was higher but significantly slower, as a consequence of formed crystals dissolution, when antimicrobial concentration was increased. Furthermore, compared to the results for the monolayer films, an important decrease of SA release rate through the multilayer films was determined. The antimicrobial effect was tested against Escherichia coli K12-MG1655. The results obtained indicated that the new biocomposite films could be promising antimicrobial food packaging materials.