Prevalence of cpe-positive Clostridium perfringens in surface-attached soil of commercially available potatoes and its significance as a potential source of food poisoning.

OBJECTIVE: We aimed to examine the surface-attached soil of commercially available potatoes in Japan to determine the association between foodborne infection and the circulation of Clostridium perfringens through vegetables, soil, and environments. METHODS: C. perfringens spores were isolated from 30 surface-attached soil samples of potatoes obtained from six regions in Japan. We performed multiplex polymerase chain reaction (PCR) and sequencing to detect the presence of six toxin and plasmid-related genes in the isolates. RESULTS: Sulfite-reducing clostridial spores were detected in 28 (93%) of 30 potato samples, and toxin gene PCR was performed using 613 isolates. The C. perfringens α toxin gene (cpa) was detected in 288 isolates (288/613; 47%) from 25 potato samples (83%), and these isolates were presumed to be the strains of C. perfringens. The toxin types of C. perfringens were classified into type A, in which 73% of isolates had only cpa, followed by type F in 20%, type C in 6%, and type E in 0.003% (1 isolate). The enterotoxin gene (cpe) related to food poisoning was detected in 64 isolates from 9 potato samples (3%). Of these, 59 isolates had cpa and cpe, whereas five had cpa, C. perfringens ß toxin gene, and cpe. All tested cpe-positive isolates had plasmid-type cpe. CONCLUSIONS: The isolation of culturable cpe-positive C. perfringens from the surface-attached soil of commercially available potatoes indicates that potatoes are a potential source of foodborne transmission of C. perfringens.

Response of Carrot (Daucus carota L.) to Multi-Contaminated Soil from Historic Mining and Smelting Activities.

A pot experiment was undertaken to investigate the effect of Cd, Pb and Zn multi-contamination on the physiological and metabolic response of carrot (Daucus carota L.) after 98 days of growth under greenhouse conditions. Multi-contamination had a higher negative influence on leaves (the highest Cd and Zn accumulation) compared to the roots, which showed no visible change in terms of anatomy and morphology. The results showed the following: (i) significantly higher accumulation of Cd, Zn, and Pb in the multi-contaminated variant (Multi) compared to the control; (ii) significant metabolic responses-an increase in the malondialdehyde content of the Multi variant compared to the control in the roots (by 20%), as well as in the leaves (by 53%); carotenoid content in roots decreased by 31% in the Multi variant compared with the control; and changes in free amino acids, especially those related to plant stress responses. The determination of hydroxyproline and sarcosine may reflect the higher sensitivity of carrot leaves to multi-contamination in comparison to roots. A similar trend was observed for the content of free methionine (significant increase of 31% only in leaves); (iii) physiological responses (significant decreases in biomass, changes in gas-exchange parameters and chlorophyll a); and (iv) significant changes in enzymatic activities (chitinase, alanine aminopeptidase, acid phosphatase) in the root zone.

Microbiome of root vegetables-a source of gluten-degrading bacteria.

Gluten is a cereal protein that is incompletely digested by human proteolytic enzymes that create immunogenic peptides that accumulate in the gastrointestinal tract (GIT). Although both environmental and human bacteria have been shown to expedite gluten hydrolysis, gluten intolerance is a growing concern. Here we hypothesize that together with food, we acquire environmental bacteria that could impact our GIT with gluten-degrading bacteria. Using in vitro gastrointestinal simulation conditions, we evaluated the capacity of endophytic bacteria that inhabit root vegetables, potato (Solanum tuberosum), carrot (Daucus sativus), beet (Beta vulgaris), and topinambur (Jerusalem artichoke) (Helianthus tuberosus), to resist these conditions and degrade gluten. By 16S rDNA sequencing, we discovered that bacteria from the families Enterobacteriaceae, Bacillaceae, and Clostridiaceae most effectively multiply in conditions similar to the human GIT (microoxic conditions, 37 °C) while utilizing vegetable material and gluten as nutrients. Additionally, we used stomach simulation (1 h, pH 3) and intestinal simulation (1 h, bile salts 0.4%) treatments. The bacteria that survived this treatment retained the ability to degrade gluten epitopes but at lower levels. Four bacterial strains belonging to species Bacillus pumilus, Clostridium subterminale, and Clostridium sporogenes isolated from vegetable roots produced proteases with postproline cleaving activity that successfully neutralized the toxic immunogenic epitopes. KEY POINTS: • Bacteria from root vegetables can degrade gluten. • Some of these bacteria can resist conditions mimicking gastrointestinal tract.

Rapid quantification of dissolved solids and bioactives in dried root vegetable extracts using near infrared spectroscopy.

Artificial neural networks (ANN) were developed for prediction of total dissolved solids, polyphenol content and antioxidant capacity of root vegetables (celery, fennel, carrot, yellow carrot, purple carrot and parsley) extracts prepared from the (i) fresh vegetables, (ii) vegetables dried conventionally at 50 °C and 70 °C, and (iii) the lyophilised vegetables. Two types of solvents were used: organic solvents (acetone mixtures and methanol mixtures) and water. Near-infrared (NIR) spectra were recorded for all samples. Principal Component Analysis (PCA) of the pre-treated spectra using Savitzky-Golay smoothing showed specific grouping of samples in two clusters (1st: extracts prepared using methanol mixtures and water as the solvents; 2nd: extracts prepared using acetone mixtures as the solvents) for all four types of extracts. Furthermore, obtained results showed that the developed ANN models can reliably be used for prediction of total dissolved solids, polyphenol content and antioxidant capacity of dried root vegetable extracts in relation to the recorded NIR spectra.

Proper management of lead-contaminated agricultural lands against the exceedance of lead in agricultural produce: Derivation of local soil criteria.

The Measures for Management of Soil Environment in Agricultural Land (Trial, Nov. 01, 2017, China) recently came into effect and highlighted the proper management of contaminated croplands to lower risks of exceedances of contaminants, especially toxic trace metals in agricultural produce. We aimed to develop local soil criteria for lead (Pb) in Hezhang county of southwestern China by the inverse use of reliable models linking Pb contamination levels between soils and vegetables. Dilute nitric acid (0.43 M) extraction, a new ISO standard (ISO-17586:2016) for extracting the geochemically reactive Pb fraction (PbNA), and calcium chloride (0.01 M) extraction (ISO-14255: 1998) for estimating the plant-available Pb (PbCC) were performed in fifty historically polluted and newly Pb-spiked soils with differing soil types, properties (pH 4.1-8.0), and total soil Pb levels (PbT, 20-6153 mg kg-1). Greenhouse experiments for Brassica pekinensis L., and in-situ soil porewater measurement for Pb were conducted to investigate the mechanism of Pb uptake, and to establish reliable Pb soil-plant relationships. The results indicated that about 83% of the variation for Pb concentrations in vegetable (PbCL, 0.009-1.06 mg kg-1) was contributable to free Pb2+ activity in soil porewater, which was mainly influenced by pH and dissolved organic matter. PbCL was satisfactorily predicted using PbNA and key soil properties (adj. R2 0.852). Soil Pb criteria for PbT and PbNA are then derived based on food standard. The full implementation of criteria derived for PbNA (i.e., 27-127 mg kg-1, soil pH 5.5-8.0) can avoid the exceedance of Pb in 95% of cabbage samples in this study, 95% of cabbage cultivars by model extrapolation, and one widely cultivated root vegetable, radish, in the study region. We provide a successful case study that has effectively tackled the challenge for the complexity of the soil management in contaminated croplands.

Efficacy of sodium hypochlorite and acidified sodium chlorite in preventing browning and microbial growth on fresh-cut produce.

The use of suitable sanitizers can increase the quality of fresh-cut produce and reduce the risk of foodborne illnesses. The objective of this study was to compare the washing effects of 100 mg/L sodium hypochlorite (SH) and 500 mg/L acidified sodium chlorite (ASC) on the prevention of enzymatic browning and the growth of microbial populations, including aerobic plate counts, E. coli, and coliforms, throughout storage at 4°C and 10°C. Fresh-cut zucchini, cucumbers, green bell peppers, and root vegetables such as potatoes, sweet potatoes, carrots, and radishes were used. Compared to SH washing, ASC washing significantly (p<0.05) reduced microbial contamination on the fresh-cut produce and prevented browning of fresh-cut potatoes and sweet potatoes during storage. More effective inhibition of aerobic plate counts and coliforms growth was observed on fresh-cut produce treated with ASC during storage at 10°C. Polyphenol oxidase (PPO) activity of fresh-cut potatoes and sweet potatoes was more effectively inhibited after washing with ASC. The use of 500 mg/L ASC can provide effective antimicrobial and anti-browning treatments of fresh-cut produce, including processed root vegetables.