Assessment of azole fungicides as a tool to control growth of Aspergillus flavus and aflatoxin B1 and B2 production in maize

ABSTRACT

Aspergillus flavus is a highly aflatoxin (AF)-producing species infecting maize and other crops. It is dominant in tropical regions, but it is also considered an emerging problem associated with climate change in Europe. The aim of this study was to assess the efficacy of azole fungicides (prochloraz, tebuconazole and a 2:1 (w/w) mixture of prochloraz plus tebuconazole) to control the growth of A. flavus and AF production in yeast-extract–sucrose (YES) agar and in maize kernels under different water activities (a_w) and temperatures. Aflatoxins B₁ and B₂ were determined by LC with fluorescence detection and post-column derivatisation of AFB₁. In YES medium and maize grains inoculated with conidia of A. flavus, the growth rate (GR) of the fungus and AFB₁ and AFB₂ production were significantly influenced by temperature and treatment. In YES medium and maize kernels, optimal temperatures for GR and AF production were 37 and 25°C, respectively. In maize kernels, spore germination was not detected at the combination 37ºC/0.95 a_w; however, under these conditions germination was found in YES medium. All fungicides were more effective at 0.99 than 0.95 a_w, and at 37 than 25ºC. Fungicides effectiveness was prochloraz > prochloraz plus tebuconazole (2:1) > tebuconazole. AFs were not detected in cultures containing the highest fungicide doses, and only very low AF levels were found in cultures containing 0.1 mg l^–1 prochloraz or 5.0 mg l^–1 tebuconazole. Azoles proved to be highly efficient in reducing A. flavus growth and AF production, although stimulation of AF production was found under particular conditions and low-dosage treatments. Maize kernels were a more favourable substrate for AF biosynthesis than YES medium. This paper is the first comparative study on the effects of different azole formulations against A. flavus and AF production in a semi-synthetic medium and in maize grain under different environmental conditions.     

Local post-harvest practices associated with aflatoxin and fumonisin contamination of maize in three agro ecological zones of Tanzania

A survey was undertaken of a total of 120 farmers, 40 from each of the three studied agro-ecological zones of Tanzania, to determine local post-harvest management practices associated with aflatoxin (AF) and fumonisin (FB) contamination of maize. Data on practices (collected using a structured questionnaire) and maize samples were obtained from each of the 120 farmers. FB and AF contamination in the samples were analysed by HPLC. A total of 45% and 85% of maize samples were positive for AF and FB respectively, with levels ranging from 0.1 to 269 μg kg^?1 for AF and from 49 to 18 273 μg kg^?1 for FBs. Significant differences in contamination level were observed among the three agro-ecological zones. Farmers in the three agro-ecological zones practised similar practices in varying degrees. Drying, sorting and protecting maize against insect infestation are practices that showed significant association with AF or FB contamination of maize. Drying maize on mat/raised platform, sorting (damaged, discoloured and moulded grains) and application of synthetic insecticides during storage are practices that were associated with less contamination of maize with AF and FB. The results can be used to advise on effective post-harvest strategies for prevention of AF and FB contamination of maize in rural Tanzania.     

Multimycotoxin and fungal analysis of maize grains from south and southwestern Ethiopia

The natural occurrence of fungi, mycotoxins and fungal metabolites was investigated in 100 samples of maize grains collected from south and southwestern Ethiopia in 2015. The maize samples were contaminated by Fusarium, Aspergillus and Penicillium species. Using liquid chromatography tandem mass spectrometry 127 secondary metabolites were analysed. Zearalenone was the most prevalent mycotoxin, occurring in about 96% of the samples. Zearalenone sulfate was the second most prevalent, present in 81% of the samples. Fumonisin B1 was detected in 70% of the samples with a mean level of 606 μg kg^?1 in positive samples, while FB2, FB3 and FB4 were detected in 62%, 51% and 60% of the maize samples with mean levels of 202, 136 and 85 μg kg^?1, respectively. Up to 8% of the samples were contaminated with aflatoxins, with a maximum level of aflatoxin B1 of 513 μg kg^?1. Results were higher than earlier reports for maize from Ethiopia.     

Ecophysiology of Fusarium temperatum isolated from maize in Argentina

The effect of water activity (a_w = 0.95, 0.98 and 0.995), temperature (15, 25 and 30°C), incubation time (7, 14, 21 and 28 days), and their interactions on growth and moniliformin (MON), beauvericin (BEA), fusaproliferin (FUS) and fumonisin B₁ (FB₁) production by two strains of Fusarium temperatum isolated from Argentinean maize were determined in vitro on sterile layers of maize grains. The results showed that there was a wide range of conditions for growth and mycotoxins production by F. temperatum. Both strains were found to grow faster with increasing a_w and at 30°C. In relation to mycotoxin production, the two strains produced more FUS than the other mycotoxins regardless of a_w or temperature evaluated (maximum = 50 000 μg g^?1). For FUS, MON and BEA, the maximum levels were observed at 0.98 a_w and 30°C (50 000, 5000 and 2000 μg g^?1 respectively). The lowest levels for these three mycotoxins were detected at 15°C and 0.95 a_w (1700 and 100 μg g^?1 for FUS and MON respectively), and at 0.98 a_w (400 μg g^?1 for BEA). The maximum levels of FB₁ were produced at 15°C and 0.98 a_w (1000 μg g^?1). At all a_w and temperatures combinations evaluated there was an increase in toxin concentrations with time incubation. The maximum levels were detected at 21 days. Statistical analyses of a_w, temperature, incubation time, and the two- and three-way interactions between them showed significant effects on mycotoxins production by F. temperatum. For its versatility on growth and mycotoxin production, F. temperatum represents a toxicological risk for maize in the field and also during grain storage.     

Quality and safety of maize (Zea mays L.) from Rondônia state storage units,Northern Brazil

The quality and safety of maize (Zea mays L.) from different grain storage units (GSUs), located in the main producing region of Rondônia State, Northern Brazil, were evaluated. Maize grains (n = 76) stored in four GSUs were collected from July to November 2014 and evaluated for grain damages, humidity, fungi and fumonisins (FBs) content. The climate conditions data were also obtained from plant growing to storage periods. Regarding the moisture content and water activity (a_w), these varied from 10.0% to 16.1% and 0.5 to 0.8, respectively. As expected, fungi spores were present in 94.8% of the samples, prevailing Fusarium genera, with a fungi colony maximum of 2.2 × 10⁴ CFU g^?1. Regarding FBs, 60.5% of the samples were contaminated, below Brazilian and United States maximum limits, but 9.2% had levels higher than the European legislation.     

Biocomposite Films Based on κ-Carrageenan/Locust Bean Gum Blends and Clays: Physical and Antimicrobial Properties

The aims of this work were to evaluate the physical and antimicrobial properties of biodegradable films composed of mixtures of κ-carrageenan (κ-car) and locust bean gum (LBG) when organically modified clay Cloisite 30B (C30B) was dispersed in the biopolymer matrix. Film-forming solutions were prepared by adding C30B (ranging from 0 to 16 wt.%) into the κ-car/LBG solution (40/60 wt.%) with 0.3 % (w/v) of glycerol. Barrier properties (water vapour permeability, P _vapour; CO₂ and O₂ permeabilities), mechanical properties (tensile strength, TS, and elongation-at-break, EB) and thermal stability of the resulting films were determined and related with the incorporation of C30B. Also, X-ray diffraction (XRD) was done in order to investigate the effect of C30B in film structure. Antimicrobial effects of these films against Listeria monocytogenes, Escherichia coli and Salmonella enterica were also evaluated. The increase of clay concentration causes a decrease of P _vapour (from 5.34?×?10^?11 to 3.19?×?10^?11 g (m s?Pa)^?1) and an increase of the CO₂ permeability (from 2.26?×?10^?14 to 2.91?×?10^?14 g (m s?Pa)^?1) and did not changed significantly the O₂ permeability for films with 0 and 16 wt.% C30B, respectively. Films with 16 wt.% clay exhibited the highest values of TS (33.82 MPa) and EB (29.82 %). XRD patterns of the films indicated that a degree of exfoliation is attained depending on clay concentration. κ-car/LBG–C30B films exhibited an inhibitory effect only against L. monocytogenes. κ-car/LBG–C30B composite films are a promising alternative to synthetic films in order to improve the shelf life and safety of food products.     

Lemon (Citrus limon, Burm.f.) essential oil enhances the trans-epidermal release of lipid-(A, E) and water-(B6, C) soluble vitamins from topical emulsions in reconstructed human epidermis

Topical bioavailability of lipid‐ and water‐soluble vitamins is a critical issue for protecting or anti‐ageing formulations. Using 17‐day‐old SkinEthic^® reconstructed human epidermis, we investigated (at 34°C) the role of lemon EO in enhancing the penetration of α‐tocopherol (E) and retinyl acetate (A), pyridoxine (B₆) and ascorbic acid (C), released from O/W or W/O emulsions. D‐limonene, α‐pinene and p‐cymene (65.9, 2.2 and 0.5%w/w of the oil) had skin permeability coefficients Ps (10^?3 cm h^?1) of 0.56 ± 0.03 (or 0.73 ± 0.02), 0.72 ± 0.05 (or 0.98 ± 0.05) and 0.84 ± 0.04 (or 1.14 ± 0.04), respectively, when incorporated in a W/O (or O/W) emulsion. Vitamins B6, C and A had Ps values of (3.0 ± 0.4) × 10^?3, (7.9 ± 0.6) × 10^?3 and (0.37 ± 0.02) × 10^?5 cm h^?1, respectively, and their flux through the skin was enhanced by a factor of 4.1, 3.4 and 5.8, respectively, in the presence of lemon EO. The penetration of vitamin E was nine‐fold enhanced. Lemon EO produced only reversible modification of TEWL, and it is a safe and effective penetration enhancer for topical administration of lipid‐ and water‐soluble vitamins.     

Selection of Universal Primers for PCR Quantification of Total Bacteria Associated With Fish Fillets

An optimal universal primer pair DG74/RW01 for quantitative PCR detection of the mixed bacterial flora from fish fillets was selected from five pairs of primers. The minimum detection limits with GelStar? and ethidium bromide (EB) used as agarose stains for DNA bands with these primers were found to be 5 and 1 × 10² CFU/PCR, respectively. The liner range of DNA amplification was from 50 to 1 × 10⁵ with GelStar? and from 5 × 10² to 1 × 10⁵ with EB.     

Natural occurrence of fumonisins B1 and B2 in corn in four provinces of China

Fumonisin B₁ (FB₁) and fumonisin B₂ (FB₂) are the most abundant fumonisins (FBs) occurring worldwide in maize, infected mainly by Fusarium verticillioides and F. proliferatum. A total of 307 corn kernel samples were collected from 45 districts of Gansu, Shandong, Ningxia and the Inner Mongolia provinces of the north and northwest China. The samples were analysed for FB₁ and FB₂ by high-performance liquid chromatography. The FBs (FB₁+ FB₂) incidence rate in samples from Gansu, Shandong, Ningxia and Inner Mongolia were 31.5%, 81.1%, 46.2% and 53.6%, respectively. Average FBs concentration was 703 μg/kg and the concentrations ranged from ≤11 to 13,110 μg kg^?1. Results were compared with the European Commission (EC) regulation for FB₁+ FB₂ in unprocessed maize for human consumption of 4 mg kg^?1. Contamination in 17 samples was higher than these levels. More than 80% of the samples from Liaocheng county, which is located in the Shandong province, were contaminated with FBs, with a mean total FB concentration of 2496 μg/kg. The result was significantly different from that of the Inner Mongolia (1399 μg/kg), Ningxia (373 μg/kg) and Gansu (175 μg/kg). Average exposure to FBs (0.12 μg/kg body weight/day) is within the provisional maximum tolerable daily intake of 2.0 mg/kg of body weight set by the Joint Food and Agriculture Organization and World Health Organization Expert Committee on Food Additives.     

Molecular Background of Technological Properties of Selected Starches

Selected starches, i.e. waxy maize, amaranth, quinoa, wheat, millet and buckwheat starches, were investigated with respect to their technological properties such as gelatinization, stability to mechanical stress, resistance to conditions and stability in continuous freeze/thaw cycles. Technological properties are correlated with molecular features such as branching characteristics in terms of iodine-complexing potential, molar mass, occupied glucan-coil volume, packing density of glucan coils and rheological properties. Waxy maize and amaranth starches were found to be amylopectin-type short-chain branched (scb) glucans with weight average molar masses M_w = 17 × 10⁶ g/mol and 12 × 10⁶ g/mol, respectively. Waxy maize starch had a high gelatinization potential, high viscosity at 95 °C (340 mPas) low stability at acidic conditions, average stability to shearing and good freeze/thaw stability. For amaranth starch a viscosity of 122 mPas at 95 °C, low resistance to acid, but high stability to applied shearing and even high freeze/thaw stability was determined. Investigated quinoa starch was classified as scb-type glucan, however, the branches are significantly longer than those of waxy maize and amaranth. With a M_w = 11 × 10⁶ g/mol and a viscosity of 187 mPas at 95 °C, this sample is comparably resistant to acidic conditions and to shearing, but instable in freeze/thaw experiments. Wheat, millet and buckwheat starches contain significant percentages of amylose-type long-chain branched (lcb) glucans (22.1, 32.1 and 24.3 %, respectively) with M_w values of 5 × 10⁶ g/mol, 12 × 10⁶ g/mol and 15 × 10⁶ g/mol, respectively. Wheat starch, with a viscosity of 107 mPas at 95 °C, shows low stability under acidic conditions, but high stability to shearing. Wheat and millet starches, but not buckwheat starch, form weak gels in the course of subsequent freeze/thaw cycles. Millet starch, with a viscosity of 101 mPas at 95 °C was found to be moderately stable under acidic conditions and to shearing. Buckwheat starch with a viscosity of 230 mPas at 95 °C shows no acid resistance and is instable upon shearing but performs very well in freeze/thaw experiments.     

Influence of storage environment on maize grain: CO2 production,dry matter losses and aflatoxins contamination

Poor storage of cereals, such as maize can lead to both nutritional losses and mycotoxin contamination. The aim of this study was to examine the respiration of maize either naturally contaminated or inoculated with Aspergillus flavus to examine whether this might be an early and sensitive indicator of aflatoxin (AF) contamination and relative storability risk. We thus examined the relationship between different interacting storage environmental conditions (0.80–0.99 water activity (a_w) and 15–35°C) in naturally contaminated and irradiated maize grain + A. flavus on relative respiration rates (R), dry matter losses (DMLs) and aflatoxin B1 and B2 (AFB1-B2) contamination. Temporal respiration and total CO₂ production were analysed by GC-TCD, and results used to calculate the DMLs due to colonisation. AFs contamination was quantified at the end of the storage period by HPLC MS/MS. The highest respiration rates occurred at 0.95 a_w and 30–35°C representing between 0.5% and 18% DMLs. Optimum AFs contamination was at the same a_w at 30°C. Highest AFs contamination occurred in maize colonised only by A. flavus. A significant positive correlation between % DMLs and AFB1 contamination was obtained (r = 0.866, p < 0.001) in the irradiated maize treatments inoculated with A. flavus. In naturally contaminated maize + A. flavus inoculum loss of only 0.56% DML resulted in AFB1 contamination levels exceeding the EU legislative limits for food. This suggests that there is a very low threshold tolerance during storage of maize to minimise AFB1 contamination. This data can be used to develop models that can be effectively used in enhancing management for storage of maize to minimise risks of mycotoxin contamination.     

The UPLC–ESI–QqQLIT–MS/MS method for quantitative determination of phytochemicals in ethanolic extracts of different parts of eight Ficus species: Development and validation

Ficus and validation of the ultra performance liquid chromatography–electrospray ionization hybrid triple quadrupole–linear ion trap–tandem mass spectrometry (UPLC–ESI–QqQ_LIT–MS/MS) method in a multiple-reaction monitoring (MRM) mode for the quantitative determination of 19 phytochemicals. The chromatographic separation of targeted phytochemicals was performed using the Waters ACQUITY UPLC BEH? C18 column (1.7 μm, 2.1 mm × 50 mm) with 0.1% formic acid with water and acetonitrile as a mobile phase at a flow rate of 0.25 mL/min. The validation parameters showed the overall recoveries from 95.78?101.44% (RSD ≤ 3.25%), precision (intra-day: RSD ≤ 2.96%; inter-day: RSD ≤ 2.89%), linearity (R² ≥ 0.9982), limit of detection (8.60 × 10^–10?2.18 × 10^–6 mg/mL), and the limit of quantitation (2.60 × 10^–9–6.63 × 10^–6 mg/mL) in the concentration range from 0.5 to 1000 × 10^–6 mg/mL. This method was successfully applied in ethanolic extracts of different parts (fruits, leaves, and barks) of selected eight Ficus species. Quinic acid was predominant followed by rutin and chlorogenic acid among the studied nineteen phytochemicals. Ficus benjamina showed the maximum total content in fruits and leaves. The UPLC–ESI–QqQ_LIT–MS/MS method combined with principal component analysis (PCA) was successfully used for Ficus species discrimination on the basis of the contents of 15 compounds. The UPLC–ESI–QqQ_LIT–MS/MS method combined with PCA could be used for quality control.     

An SEC−MALLS Study of Molecular Features of Water‐soluble Amylopectin and Amylose of Tef [Eragrostis tef (Zucc.) Trotter] Starches

The molecular features of five tef starches along with those of commercial normal maize starch were investigated by size‐exclusion chromatography with multi‐angle laser light scattering‐differential refractive index detection (SEC/MALLS‐DRI) after solubilization in water by cooking in a household pressure cooker. The weight‐average molar mass ( ) and weight‐average root‐mean square radius of gyration (<R_g>_w) of the amylopectin (AP) of tef starches ranged from 10.1×10⁷ g/mol (156 nm) to 16.5×10⁷ g/mol (205 nm) with a mean of 13.9×10⁷ g/mol (186 nm). The AP of the tef starches was considerably smaller than that of maize starch ( = 19.6×10⁷ g/mol, <R_g>_w = 207 nm). These considerably smaller AP molecules in tef starches were most probably responsible for the low paste viscosity of tef starches as compared to maize starch. In most tef starches, the polydispersity index (PI) of the AP was broader than that of the AP of maize starch. The intermediate fraction (IN) 1.0−1.6, mean = 1.1) of most tef starches were similar to those of the IN of maize starch. The amylose (AM) (range 1.5×10⁶−3.0×10⁶ g/mol, mean = 2.2×10⁶ g/mol) and size (range 176−214 nm, mean = 191 nm) of most tef starches was also apparently similar to that of the maize starch ( = 2.3×10⁶ g/mol, <R_g>_w = 193 nm), but the polymer distribution was narrower. The AM−iodine complex of the tef starches had a λ_max range of 611−679 nm and the absorption shifted toward longer wavelengths by 8−14 nm as compared to the maize starch AM−iodine complex. The blue value (absorption at λ_max) for 1 mg/mL of tef AM had a range of 2.3−2.8 (mean = 2.5), whereas for the maize starch, the mean was 2.2. The branched nature of tef starches was also investigated by debranching with isoamylase and determination of chain lengths (DP_n) of the branches by size exclusion chromatography with refractive index detector (SEC‐RI). The AP in tef starches had a polymodal distribution with a periodicity similar to that of cereal starches. The branches had DP_n values of A = 11, B1 = 16, B2 = 46 (range 46−47), B3 = 70 (range 69−72) and B4 = 118 (range 113−123). The outer (A + B1) chains were shorter than those of maize starch AP with abundance (74%, w/w) only slightly less than that of the maize starch (75%, w/w). The slow rate of retrogradation, the slightly lower percent crystallinity, the lower gelatinization temperatures and the lower gelatinization enthalpy observed for tef starches (as compared to maize starch) are probably related to the shorter outer (A + B1) chain lengths of their amylopectin molecules, and may be the foundation of the comparably good keeping quality of tef injera, the main staple in the Ethiopian diet.     

Relative severity of fumonisin contamination of cereal crops in West Africa

Traditional and improved varieties of maize, pearl millet and sorghum were planted by small-scale farmers under the direction of the International Institute for Tropical Agriculture in two Nigerian agro-ecological zones: the Sudan Savanna and the Northern Guinea Savanna. Samples were collected for the determination of Fusarium infection and fumonisin (B₁, B₂ and B₃) contamination. A previous paper reported Aspergillus infection and aflatoxin contamination of these samples. Fusarium infection levels, measured by per cent kernels infected, were modest with mean levels for the above cereals of 16% ± 11% (SD), 12% ± 7% and 13% ± 16%, respectively. However, the Fusarium species recovered from maize were predominantly the fumonisin producers F. verticillioides and F. proliferatum, together making an infection rate of 15% ± 10%, whereas these species were present to a limited extent only in the other two cereals, 1% ± 1% for pearl millet and 2% ± 6% for sorghum. Fumonisin contamination was variable but reflected the diversity of Fusarium producers in these three cereals. Mean levels were 228 ± 579 µg kg^–1 (range < 5–2860 µg kg^–1) for maize, 18 ± 7 µg kg^–1 (range = 6–29 µg kg^–1) for pearl millet and 131 ± 270 µg kg^–1 (range < 5–1340 µg kg^–1) for sorghum. Together with previous results on aflatoxin, this study confirmed the co-occurrence of aflatoxins and fumonisins in maize as well as in the traditional African cereals, millet and sorghum (89% co-occurrence across all three cereals). The low fumonisin levels may be ascribed to the use of good agricultural practices. Of the Fusarium species present, those in maize consisted mainly of fumonisin producers, the opposite of what was observed in pearl millet and sorghum. It is concluded that replacement of maize by pearl millet and sorghum could improve food safety with regards to aflatoxin B and fumonisin B exposure.     

Mycotoxin contamination of sorghum and its contribution to human dietary exposure in four sub-Saharan countries

This research aimed at evaluating the safety, and the type, level and prevalence of mycotoxins in grain sorghum of four sub-Saharan African (SSA) countries (Burkina Faso, Ethiopia, Mali and Sudan). A multi-analyte LC-MS/MS method for quantification of 23 mycotoxins (nivalenol, deoxynivalenol, fusarenon X, neosolaniol, 3-acetyl deoxynivalenol, 15-acetyl deoxynivalenol, diacetoxyscirpenol, roquefortine C, HT-2 toxin, alternariol, T-2 toxin, FB1, FB2, FB3, zearalenone, aflatoxin G₁, aflatoxin G₂, aflatoxin B₁, aflatoxin B₂, sterigmatocystin, OTA, altenuene, alternariol monomethylether) was applied to different sorghum matrices. Of the 1533 analysed samples, 33% were contaminated with at least one of the following mycotoxins: aflatoxins, fumonisins, sterigmatocystin, Alternaria toxins, OTA and zearalenone. Country of origin, colour, source and collection period of sorghum samples significantly influenced the type, level and prevalence of mycotoxins. Sterigmatocystin (15%), fumonisins (17%) and aflatoxins (13%) were the most prevalent. FB1 (274 ± 585 µg/kg) had the highest mean concentration followed by FB2 (214 ± 308 µg/kg) while diacetoxyscirpenol (8.12 ± 19.2 µg/kg) and HT-2 (11.9 ± 0.00 µg/kg) had the lowest concentrations. Neosolaniol, fusarenon-X, 3-acetyl deoxynivalenol, 15-acetyl deoxynivalenol, T-2 toxin, nivalenol and roquefortine C were not detected in any of the samples. Sudan had the lowest prevalence and mean concentration of all mycotoxins. Pink sorghum had the highest concentrations of fumonisins and aflatoxins. Mycotoxins from Aspergillus spp. and Alternaria spp. are the mycotoxins of concern in SSA grain sorghum with regard to prevalence, concentration and possible health risk from exposure. Based on the performed risk characterisation, daily consumption of sorghum containing aflatoxins, alternariol, alternariol monomethyl ether, sterigmatocystin and OTA could result in exceeding the established health-based guidance values for these toxins.     

Effects of infrared heating on drying kinetics,antioxidant activity,phenolic content,and color of jujube fruit

This study investigated the effects of different infrared power (IP) levels (62, 88, and 125 W) and a pretreatment (soaking in a solution of 5 % potassium carbonate and 0.5 % olive oil) on the drying kinetics and some quality parameters of jujube fruit. The drying characteristics of jujube were greatly influenced by the pretreatment and IP level. The models of Lewis, Logarithmic, Page, and Aghbashlo et al. were fitted to the obtained experimental data using nonlinear regression analysis. The Page model showed a better fit to the experimental drying data when compared to the other models. The effective moisture diffusivity, calculated using Fick’s second law, ranged from 4.75 × 10^?10 to 4.17 × 10^?9 m²/s. Significantly, higher total phenolic content (TPC) and antioxidant capacity values were obtained for the pretreated samples subjected to higher IP levels. The total color change (ΔE) of the dried samples significantly increased with increasing IP level. Jujube fruits should be pretreated and then dried at 88 W IP to reduce phenolic degradation and undesired color changes and to increase the quality of the dried product.     

Mycotoxin contamination of home-grown maize in rural northern South Africa (Limpopo and Mpumalanga Provinces)

The aim of this study was to assess mycotoxin contamination of crops grown by rural subsistence farmers over two seasons (2011 and 2012) in two districts, Vhembe District Municipality (VDM, Limpopo Province) and Gert Sibande District Municiality (GSDM, Mpumalanga Province), in northern South Africa and to evaluate its impact on farmers’ productivity and human and animal health. A total of 114 maize samples were collected from 39 households over the two seasons and were analysed using a validated liquid chromatography-tandem mass spectrometry mycotoxins method. Aflatoxin B₁ (AFB₁) occurrence ranged from 1 to 133 µg kg^?1 in VDM while AFB₁ levels in GSDM were less than 1.0 µg kg^?1 in all maize samples. Fumonisin B₁ levels ranged from 12 to 8514 µg kg^?1 (VDM) and 11–18924 µg kg^?1 (GSDM) in 92% and 47% positive samples, respectively, over both seasons. Natural occurrence and contamination with both fumonisins and aflatoxins in stored home-grown maize from VDM was significantly (p < 0.0001) higher than from GSDM over both seasons.     

Impact of environment and interactions of Fusarium verticillioides and Fusarium proliferatum with Aspergillus parasiticus on fumonisin B1 and aflatoxins on maize grain

Fusarium verticillioides and F proliferatum isolates were inoculated in mixed cultures with Aspergillus parasiticus on irradiated maize grain at two different inoculum concentrations (2 × 10⁵ and 2 × 10² conidia g^?1 dry maize). The treatments were 0.93–0.98 water activity (a_w) and 15 and 25 °C for 28 days. A complex relationship was found between a_w, temperature, inoculum concentration and the interactions which took place between fumonisin and aflatoxin producers. In general, A parasiticus reduced F verticillioides and F proliferatum populations (by 6–36%) but did not affect fumonisin B₁ production by these species. In contrast, while the Fusarium species were not able to decrease A parasiticus populations, they significantly reduced aflatoxin B₁ accumulation (by 30–93%). © 2001 Society of Chemical Industry     

Inhibitory effects of selected pesticides on peroxidases purified by affinity chromatography

The objective of this study was to determine the in vitro inhibition effects of seven commonly used pesticides including 2,4-d-acid dimethylamine, fenoxaprop-p-ethyl, glyphosate isopropylamine, haloxyfop-p-methyl, cypermethrin, λ-cyhalothrin, and dichlorvos on the peroxidase purified from turnip (Brassica rapa L.) and black radish (Raphanus sativus L.) using 4-amino benzohydrazide affinity column chromatography. The purification factors for the turnip and black radish peroxidases were found to be 263.29-fold (with a yield of 12.89%) and 36.20-fold (with a yield of 6.90%), respectively. Among these compounds, λ-cyhalothrin showed the strongest inhibitory effect against turnip peroxidase (K_i: 1.23 × 10^?2 ± 0.21 × 10^?2 mM) as noncompetitive inhibition. On the other hand, cypermethrin demonstrated the highest inhibition effect against black radish peroxidase (K_i: 2.14 × 10^?2 ± 0.08 × 10^?2 mM) as competitive inhibition.     

Physicochemical properties of starch isolated from Antiaris africana seeds in comparison with maize starch

Antiaris africana seeds yielded 29.6% starch which showed appreciable high contents of ash, protein, and fat. The average diameter of A. africana starch granules was 3.98 µm compared to 8.93 µm for maize starch. A. africana starch had a C‐type XRD pattern and crystallinity of 41.5%. A. africana starch had higher AM content (24.1%) than maize starch (20.9%). The gelatinization onset temperature of A. africana starch (66.7°C) was higher than maize starch (63.1°C), but its gelatinization temperature range (8.57°C) and enthalpy (13.97 J/g) were lower than the values for maize starch (14.02°C, 14.65 J/g). The pasting temperature (P_t) and setback (V_s) were lower and breakdown (V_b) higher for A. africana starch (P_t = 82.5°C, V_s = 173.8 RVU, and V_b = 121.42 RVU) than for maize starch (P_t = 84.9°C, V_s = 183.73 RVU, and V_b = 78.58 RVU). The GPC analysis gave M_w of 2.18 × 10⁷ g/mol and radius of gyration of 95.1 nm for Antiaris starch. Antiaris starch paste exhibited poor freeze‐thaw stability but its small granule size indicates potential for application as dusting starch.