Trichloroethylene uptake into fruits and vegetables: three-year field monitoring study

Trichloroethylene (TCE) contaminated groundwater migrating into communities surrounding Hill Air Force Base (HAFB) in northern Utah prompted a multiyear monitoring program (2001-2003) to examine the extent of TCE uptake and transfer into edible fruits. During the initial sampling in fall 2001, TCE was detected in a small fraction of the 167 fruit and tree core samples collected from 17 private residences. Samples were analyzed using headspace gas chromatography (GC) with electron capture detection (ECD) with limited confirmation by mass spectrometry (MS) in selected ion monitoring mode. In fall 2002, over 300 samples were collected from the same general locations sampled in 2001. No TCE was found in any of the fruit or vegetable samples above the method detection limit (MDL) for the headspace GC/MS method (approximately 0.1 microg/ kg fresh weight, depending on sample size), but TCE was again detected in several fruit tree trunk core samples. The detection of TCE in fruit in 2001, but not in 2002, may have been due to improvements in the analytical procedure or changes in the environmental conditions impacting transfer to fruit. The 2003 monitoring focused on repeated sampling over several months at five locations that were selected to represent the range of exposure scenarios evaluated during the previous years. No TCE was identified in any of the fruit above the MDL during 2003, however TCE was again found in tree core samples as observed in 2001 and 2002.     

Pesticide residues in foodstuffs in Great Britain. IX. Aldrin, dieldrin and other organochlorine pesticide residues in potatoes and carrots

Potatoes from 186 commercial crops from fields treated with aldrin or dieldrin in the year of cropping contained mean residues of aldrin plus dieldrin of 0.01 ppm in the flesh and 0.1 ppm in the skin. Seventy crops from fields that had been treated with aldrin or dieldrin in years previous to the year of cropping and forty-four crops from reputedly untreated fields contained mean residues of aldrin/dieldrin of less than 0.01 ppm in the flesh and 0.02 ppm in the skin. Alpha- and/or gamma-BHC were detected in trace or greater amounts in 73% and pp' DDE in 10% of the samples. Carrots from 97 commercial crops from fields treated with aldrin or dieldrin in the year of cropping contained mean residues of aldrin plus dieldrin of less than 0.01 ppm in the flesh and 0.21 ppm in the skin. Fifty crops from fields that had been treated with aldrin or dieldrin in years previous to the year of cropping contained mean residues of aldrin/dieldrin of less than 0.01 ppm in the flesh and 0.07 ppm in the skin. Six crops from reputedly untreated fields contained a mean residue of less than 0.01 ppm dieldrin in the skin only. Alpha- and gamma-BHC were found in the majority of the samples (mean total residue of less than 0.01 ppm in the flesh and 0.03 ppm in the skin) but pp' DDE and/or pp' DDT were detected in only 12% of the samples.     

Field experiments on the magnesium requirement of cereals,potatoes and sugar beet in relation to nitrogen and potassium application

In 43 experiments on a range of soils there was little indication that magnesium sulphate applied to the seedbed increased yield of cereals, potatoes or sugar beet. In one experiment only, on potatoes, a very high rate of muriate of potash induced magnesium deficiency. Different rates of ammonium sulphate, compared on cereals only, did not affect crop response to magnesium. The magnesium content of barley foliage and the effects of magnesium sulphate and ammonium sulphate on this content were shown to be related to soil potassium and magnesium levels.     

熟化甘薯热风干燥特性及数学模型研究

利用热风干燥试验台对熟化甘薯的热风干燥特性进行研究,探讨不同干燥温度、热风风速、铺料密度对干燥速率的影响,其影响因素大小依序为：干燥温度＞干燥风速＞铺料密度.利用3种不同干燥速率模型对实验数据进行拟合,发现甘薯热风干燥符合Page方程,即,模型拟合F值为1 102.35,呈极显著.     

Glycoalkaloids in potatoes

The glycoalkaloids present in the cultivated potato plant might result in their being unacceptable by present-day food standards, if that vegetable were introduced today. The alkaloids are derived biosynthetically from cholesterol. The range of glycoalkaloids found in nature is given. Two main methods of determining these alkaloids have been developed, enabling a general screening procedure to be employed by growers. The advent of protoplast techniques has opened up the possibility of many new species and they present the chemist with new problems. There can be a conflict between the requirement of pest- and disease-resistant potatoes and those with low levels of glycoalkaloids. Damage and microbial infection to potatoes may cause glycoalkaloids to develop. In the end, the consumer must be the final arbiter.     

Cell wall modifications during cooking of potatoes and sweet potatoes

Sweet potato (Ipomoea batatas L) tissue, when cooked at 70 °C to activate β‐amylase and break down starch, takes on a distinctive firm, brittle texture and does not show the cell separation that occurs in, for example, cooked potato (Solanum tuberosum L). Similar cooking conditions increase firmness in other plants by activating pectin methyl esterase which de‐esterifies pectic polysaccharides and protects them from thermal depolymerisation. We therefore isolated cell walls from both potatoes and sweet potatoes cooked at 70 °C and 100 °C and determined the remaining degree of methyl esterification of their pectins. Pectins from both species were demethylated to a similar extent at 70 °C and 100 °C. Since cooking sweet potato at 100 °C induced cell separation and softening, it is concluded that β‐amylase is rapidly inactivated at that temperature and swollen starch distends and separates the cells, whereas the firm texture obtained by cooking that species at 70 °C is not the result of pectin demethylation but is caused by the breakdown of starch to oligomers that can escape from the cell. © 2000 Society of Chemical Industry     

Thermal properties of potatoes and a computer simulation model of a blanching process

Thermal conductivity and specific heat were experimentally determined in Bintje potatoes. The methods used were a transient hot-strip method and differential scanning calorimetry respectively. The results from the experiments were used in a theoretical calculation model using the finite element technique. Temperature profiles and heat transfer coefficients were simulated and the theoretical calculations were compared with experimental data for the blanching process. The correlation between experi-mental data and theoretical calculations was good if the heat transfer coefficient was assumed to be 750 W/m²°C.     

Beyond meat and potatoes: A review essay

Harvey Levenstein. Revolution at the Table: The Transformation of the American Diet. New York: Oxford University Press, 1988.     

Texture of cooked potatoes: The effect of ions and ph on the compressive strength of cooked potatoes

It was shown from experiments on disks cooked in solutions of calcium chloride and calcium acetate, and in buffered solutions of calcium chloride at various pHs (sodium concentration constant) and from experiments where the ratios of disks to calcium chloride were varied, that the effect of calcium in increasing the compressive strength of the disks was small compared to the effect of reduced pH. The interaction of sodium and calcium was investigated at pH 6 (≈? the pH of cooked potato tissue). The effect of sodium in reducing compressive strength of the disks outweighed the effect of calcium in increasing compressive strength. Sodium and potassium chloride had a similar effect on loss of compressive strength on cooking. Increased compressive strength due to pH or the presence of calcium was overcome by extending the length of cooking. It is suggested that transelimination, ion exchange and hydrogen bond breakage may be more important factors than the chelation of calcium by naturally occurring phytin, in the breakdown of pectic substances and loss of intercellular adhesion during normal cooking of toes.     

Microbiology of potatoes and potato products: a review

Many types of spoilage and pathogenic microorganisms exist on fresh, minimally processed, and fully processed potato products. Potatoes are processed into many products including frozen, dried, ready-to-eat, and minimally processed. The microbiological quality of finished potato products is influenced by the natural microflora, processing, handling, and human contact. The natural microflora of potatoes are influenced by soil and airborne inocula, agricultural practices, harvesting methods, and storage conditions. The microflora of processed products are influenced by all of the factors and conditions affecting the natural microflora as well as the processes applied to the product. Increased consumer demand for new and existing potato products highlights the importance of ensuring their microbiological safety. This review considers the sources of microorganisms, microflora, foodborne disease pathogens, and outbreaks associated with, and selected microbiological research involving, potatoes and potato products.     

Pesticide sorption and desorption by lignin described by an intraparticle diffusion model

Lignin was used as a model compound for soil organic matter to gain insight into the mechanisms that control the kinetics of pesticide sorption and desorption. Hydrolytic lignin was immobilized in a matrix of alginate gel, and sorption-desorption experiments were undertaken with isoproturon. Sorption increased with time and was close to equilibrium after 14 days. Desorption was measured after sorption for different time intervals and for a number of successive desorption steps of different lengths. The results showed strong differences between the sorption and desorption isotherms. The ratio of sorbed to dissolved pesticide approached and even exceeded the equilibrium ratio, depending on the number of desorption steps and the length of each equilibration period. A numerical diffusion model was developed to describe radial diffusion into the lignin particles in combination with Freundlich sorption inside the particles. Key model parameters were adjusted to fit the sorption data, and the same parameters were then used to predict stepwise desorption. Desorption was well described by the model, which suggests that sorption and desorption were driven by the same mechanism and occurred at the same rate. The observed difference between the sorption and desorption isotherms could be fully explained by the nonattainment of equilibrium due to slow diffusion into and out of the lignin particles.     

Modeling atmospheric vegetation uptake of PBDEs using field measurements

Polybrominated diphenyl ethers (PBDEs) are flame retardants used in a variety of consumables. Models indicate that air-vegetation exchange plays an important role in their global distribution. The present study surveyed PBDEs in spruce needles and air (gaseous and particulate-bound) over an annual cycle to model accumulation of PBDEs in vegetation. Air-particulate distributions revealed that penta and higher BDE congeners were mainly associated with particulates even in warmer temperatures, whereas for the tri- and tetra-BDE congeners, a significant temperature dependence was observed. Using measured vegetation and atmospheric concentrations from bud burst 2004 to June 2005, a modeling concept was developed to determine PBDE deposition velocities to vegetation. Particulate-bound deposition velocity was calculated to be 3.8 m/h. Net gaseous transfer velocities ranged from 2.4 to 62.2 m/h and correlated significantly with log K(OA). These derived values were used to model PBDE accumulation by vegetation through time, and these agreed well with measured values. This study provides the necessary background for modeling PBDE transport between air and coniferous vegetation globally.     

Acrylamide in home-prepared roasted potatoes

Potato is one of the world's most widely grown tuber crop, in which starch is the predominant form of carbohydrates. Potatoes can be prepared in many ways: boiled, fried or roasted. Frying and roasting potatoes at high temperatures result in an appetizing crust, but at the same time acrylamide can form. In this study, the concentrations of the acrylamide precursors, asparagine and sugars, were determined in five different Swedish-grown potato varieties, together with the acrylamide content after typical home-cooking procedures; oven-roasting of potato wedges and pan-frying of cubes of boiled potatoes. Pan-frying of boiled potato cubes resulted in higher levels of acrylamide (530-1100 microg/kg) than in the wedges (140-250 microg/kg). Blanching combined with a shorter roasting time was shown to be an efficient way of reducing the acrylamide content in roasted potato wedges, especially in the experiments performed after long-term storage, where the acrylamide content was reduced from 110-260 to 50-140 microg/kg. No correlation was found between precursor content and acrylamide content, and this finding emphasizes the need for further studies on factors affecting acrylamide formation, for example, the availability of precursors at the surface during cooking.     

Emission of di-2-ethylhexyl phthalate from PVC flooring into air and uptake in dust: emission and sorption experiments in FLEC and CLIMPAQ

The emission of di-2-ethylhexyl phthalate (DEHP) from a PVC flooring was studied for up to 472 days in both the FLEC (Field and Laboratory Emission Cell) and the CLIMPAQ (Chamberfor Laboratory Investigations of Materials, Pollution, and Air Quality). The loading of the CLIMPAQs was varied but was constant in the FLECs. The sorption properties of FLEC and CLIMPAQ were investigated using different methods. In addition, the uptake of DEHP by office floor dust on the PVC flooring was studied in CLIMPAQ experiments. The concentration versus time curves in both FLECs and CLIMPAQs increased slowly over about 150 days and reached a quasi-static equilibrium at 1 microg m(-3). The main conclusions were that (i) the emission rate of DEHP was limited by gas-phase mass transport and (ii) the dust layer increased the emission rate by increasing the external concentration gradient above the surface of the PVC. These conclusions were based on the facts that the specific emission rate was inversely proportional to the loading and that the dust had sorbed about four times as much DEHP over a 68-day period as emitted in the gas-phase experiments. About one-half of the emitted DEHP was deposited on the internal surfaces of both the FLEC and the CLIMPAQ.     

Arsenic in soil and irrigation water affects arsenic uptake by rice: complementary insights from field and pot studies

Groundwater rich in arsenic (As) is extensively used for dry season boro rice cultivation in Bangladesh, leading to long-term As accumulation in soils. This may result in increasing levels of As in rice straw and grain, and eventually, in decreasing rice yields due to As phytotoxicity. In this study, we investigated the As contents of rice straw and grain over three consecutive harvest seasons (2005-2007) in a paddy field in Munshiganj, Bangladesh, which exhibits a documented gradient in soil As caused by annual irrigation with As-rich groundwater since the early 1990s. The field data revealed that straw and grain As concentrations were elevated in the field and highest near the irrigation water inlet, where As concentrations in both soil and irrigation water were highest. Additionally, a pot experiment with soils and rice seeds from the field site was carried out in which soil and irrigation water As were varied in a full factorial design. The results suggested that both soil As accumulated in previous years and As freshly introduced with irrigation water influence As uptake during rice growth. At similar soil As contents, plants grown in pots exhibited similar grain and straw As contents as plants grown in the field. This suggested that the results from pot experiments performed at higher soil As levels can be used to assess the effect of continuing soil As accumulation on As content and yield of rice. On the basis of a recently published scenario of long-term As accumulation at the study site, we estimate that, under unchanged irrigation practice, average grain As concentrations will increase from currently ～0.15 mg As kg(-1) to 0.25-0.58 mg As kg(-1) by the year 2050. This translates to a 1.5-3.8 times higher As intake by the local population via rice, possibly exceeding the provisional tolerable As intake value defined by FAO/WHO.     

Pesticide residues in foodstuffs in Great Britain. VII. Demeton-methyl and dimethoate residues in Brussels sprouts, lettuce, green peas and French beans, potatoes and strawberries

Samples of Brussels sprouts, lettuce, green peas and French beans, potatoes and strawberries from commercial crops that had been treated with demeton-methyl, oxydemeton-methyl, dimethoate and/or formothion were analysed at the time of harvest. 168 of 191 samples (88%) contained residues of these pesticides not exceeding 0.2 ppm; the residues in the remainder did not exceed 0.8 ppm.     

Dietary fibre in sweet potatoes

The dietary fibre content of sweet potatoes grown in southwestern Ontario was found to be equivalent to that in roots produced in the United States. Based on a 3-year survey (1989, 1990, 1992) of three cultivars (Beauregard, Georgia Jet and Jewel), the total dietary fibre ranged from 9·07–12·16% for cured roots. Soluble and insoluble dietary fibre averaged 5·30% and 5·43%, respectively. Five cultivars were analysed, of each in green, cured and stored states, from the 1989 crop-year. With the exception of Southern Delite, whose fibre increased over 3% when stored, the analyses showed very little change in each cultivar's total dietary fibre in any state.     

Research Watch: Pesticide contamination

Water.     

Research Watch: Pesticide contamination

Soil Remediation.     

Research Watch: Pesticide mobility

Soil.