Evaluation of food grade antioxidant formulation for sustained antifungal,antiaflatoxigenic and insecticidal activities on peanut conditioned at different water activities

The aim of this study was to investigate antifungal and insecticidal activity of two microencapsulated antioxidants: 2(3)-tert-butyl-4 hydroxyanisole (BHA) and 2,6-di(tert-butyl)-p-cresol (BHT) against Aspergillus section Flavi and Oryzaephilus surinamensis (L.), a vector carrier of aflatoxigenic fungi on stored peanuts. Susceptibility of Aspergillus section Flavi, insects, and aflatoxin B₁ accumulation in sterile peanut kernels conditioned at two different water activities (a_w) (0.83 a_w and 0.95 a_w) was determined with different doses of antioxidant formulations (10, 20 and 30 mM) during 45 days. Moreover, Aspergillus section Flavi isolation frequency from live and dead insects was evaluated. The BHA formulation completely inhibited Aspergillus section Flavi development regardless of a_w and doses assayed. Antifungal effect of microencapsulated BHT was highly dependent on a_w, with 86–100% fungal inhibition at 20 and 30 mM, at the lowest a_w (0.83 a_w) and at the end of the experiment. No aflatoxin accumulation was detected in samples treated with the BHA formulation. In general, low levels of Aspergillus section Flavi were detected in dead insects. Our results show efficacy for 45 days, in addition microencapsulated BHT could be an alternative to control peanut pests in dry kernels.     

Simultaneous voltammetric determination of phenolic antioxidants in food using a boron-doped diamond electrode

A method for the simultaneous determination of butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) in food was developed using square-wave voltammetry (SWV). The determination of these phenolic antioxidants was carried out using a cathodically pre-treated boron-doped diamond electrode (BDD) and an aqueous-ethanolic (30% ethanol, v/v) 10 mmol L⁻¹ KNO₃ solution (pH_cond. 1.5) as supporting electrolyte. In the SWV measurements using the BDD electrode, the oxidation peak potentials of BHA and BHT present in binary mixtures were separated by about 0.3 V. The attained detection limits for the simultaneous determination of BHA and BHT (0.14 and 0.25 μmol L⁻¹, respectively) are lower than the ones by voltammetric techniques reported in the literature. The proposed method was successfully applied in the simultaneous determination of BHA and BHT in food products, with results similar to those obtained using a high-performance liquid chromatography method, at a 95% confidence level.     

Residue levels of food-grade antioxidants in postharvest treated in-pod peanuts during five months of storage

In order to investigate residue levels of butylated hydroxyanisole (BHA), propyl paraben (PP) and butylated hydroxytoluene (BHT) during storage, eight-hundred kilograms of bulk peanuts were treated with the following antioxidant emulsions: BHA (1802 μg g⁻¹), BHA–PP (1802 μg g⁻¹ + 1802 μg g⁻¹) M1 and BHA–PP–BHT mixtures (1802 μg g⁻¹ + 901 μg g⁻¹ + 2204 μg g⁻¹) M2 and (1802 μg g⁻¹ + 1802 μg g⁻¹ + 2204 μg g⁻¹) M3. Residues were determined in peanut pod and seed tissues at 1-month intervals during the storage. While the reduction levels of BHA and PP in pods at the end of the storage period ranged from 66% to 76%, BHT levels were decreased extensively (86%). Twenty-four hours after peanuts were treated, antioxidant emulsions effectively seeped into the seeds and low levels of these chemicals were detected during the assay. Residues of PP in seeds were lower (62%) than the other antioxidants. Although the doses used were higher than those approved for food-grade antioxidants in stored peanuts, the residue levels in seeds (32.8–0.02 μg g⁻¹) did not exceed the maximum residue limits during the storage period.     

Antiaflatoxigenic property of food grade antioxidants under different conditions of water activity in peanut grains

Analytical grade (AG) and industrial grade (IG) of three-food grade antioxidants butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and propyl paraben (PP) were analyzed to prove their fungitoxic effect on Aspergillus section Flavi strains. The effect of interactions among 10 antioxidant treatments at water activity levels (0.982, 0.955, 0.937 a(W)) for 11 and 35 days of incubation and at 25 degrees C in peanut grains on mycelial growth (CFU g(-1)) and aflatoxin B(1) (AFB(1)) accumulation were evaluated. Both antioxidant grade treatments had a significant effect (P<0.001) on fungal count. All antioxidant treatments showed the highest effectiveness on control of growth of peanut aflatoxigenic strains at 0.937 a(W) and at 11 days of incubation. Overall, AG and IG binary mixtures M3 (20+10 mM), M4 (20+20 mM) and ternary mixtures M5 (10+10+10 mM), M6 (10+20+10 mM), M7 (20+10+10 mM) and M8 (20+20+10 mM) were the treatments most effective at inhibiting growth of Aspergillus section Flavi strains. Industrial grade BHA 10 and 20 mM, binary mixtures M1 (10+10 mM), M2 (10+20 mM), M3 (20+10 mM), M4 (20+20 mM) and ternary mixtures M5 (10+10+10 mM), M6 (10+20+10 mM), M7 (20+10+10 mM) and M8 (20+20+10 mM) completely inhibited AFB(1) production. The studied results suggest that IG antioxidant mixtures have potential for controlling growth of these mycotoxigenic species and prevent aflatoxin accumulation at the peanut storage system.     

Water availability and calcium propionate affect fungal population and aflatoxins production in broiler finisher feed during storage

The aim of this study was to investigate the effects of calcium propionate, water activity (a_w) and incubation time on the total fungal count and aflatoxins B₁ (AFB₁), B₂ (AFB₂), G₁ (AFG₁) and G₂ (AFG₂) production in the broiler finisher feed. The feed was added with calcium propionate (5 g kg^–1), adjusted to 0.85, 0.90 and 0.95 a_w and stored for 28 days at 25°C, analysing for mould growth and aflatoxins production every 7 days. Analysis of variance indicated that all the factors (preservative, a_w and storage time) alone and in combination significantly (p < 0.001) affected the total fungal count and aflatoxins production in the feed. Minimum total fungal counts (1.99 × 10² CFU g^–1) were observed in calcium propionate feed at 0.85 a_w on day 1 and the highest (4.36 × 10⁹ CFUs g^–1) in control sample at 0.95 a_w on day 28 of storage. During the storage period, AFB₁ content in control samples increased from 11.35 to 73.44, from 11.58 to 81.81 and from 11.54 to 102.68 ng g^–1, whereas in preserved feed the content of B₁ increased from 11.47 to 37.83, from 11.54 to 49.07 and from 11.20 to 53.14 ng g^–1 at 0.85, 0.90 and 0.95 a_w, respectively. Similar patterns were noted for AFB₂, AFG₁ and AFG₂ contents. All the aflatoxins readily increased over storage time; however, the increase was much slower in preserved feed that contained a lower amount of available water. This study reveals that calcium propionate addition to poultry litter along with water activity amelioration is an effective tool for controlling mould incidence and aflatoxin production in poultry feed.     

Effect of synthetic antioxidants on stored maize grain mycoflora in situ

BACKGROUND: The influence of a mixture of butylated hydroxyanisole (BHA) and propyl paraben (PP) (each at a concentration of 20 mmol L^?1) on mycoflora and Aspergillus section Flavi populations in stored maize grain was evaluated. A survey of 120 maize samples was carried out from June to November 2005. RESULTS: The predominant populations in non‐treated (control) maize between the first and sixth sampling periods were Aspergillus section Flavi and Penicillium. Aspergillus flavus was the fungus most frequently isolated from both control and antioxidant‐treated kernels. All samples of control and antioxidant‐treated maize kernels were negative for aflatoxins during the 6 month storage period. Aspergillus flavus and A. parasiticus strains showed a variable ability to produce aflatoxins. The contribution of the strains to silo community toxigenicity was higher for A. flavus L (large) and S (small) strains in the fourth sampling period. CONCLUSION: Antioxidant treatment negatively affected natural maize mycoflora and Aspergillus section Flavi populations between the second and sixth months of storage. Copyright © 2007 Society of Chemical Industry     

Application of essential oils in maize grain: impact on Aspergillus section Flavi growth parameters and aflatoxin accumulation

The antifungal activity of Pimpinella anisum L. (anise), Pëumus boldus Mol (boldus), Hedeoma multiflora Benth (mountain thyme), Syzygium aromaticum L. (clove), and Lippia turbinate var. integrifolia (griseb) (poleo) essential oils (EOs) against Aspergillus section Flavi was evaluated in sterile maize grain under different water activity (a_w) condition (0.982, 0.955, and 0.90). The effect of EOs added to maize grains on growth rate, lag phase, and aflatoxin B₁ (AFB₁) accumulation of Aspergillus section Flavi were evaluated at different water activity conditions. The five EOs analyzed have been shown to influence lag phase and growth rate. Their efficacy depended mainly on the essential oil concentrations and substrate water activity conditions. All EOs showed significant impact on AFB₁ accumulation. This effect was closely dependent on the water activity, concentration, and incubation periods. Important reduction of AFB₁ accumulation was observed in the majority of EO treatments at 11 days of incubation. Boldus, poleo, and mountain thyme EO completely inhibited AFB₁ at 2000 and 3000 μg g⁻¹. Inhibition of AFB₁ accumulation was also observed when aflatoxigenic isolates grew with different concentration of EOs during 35 days.     

Effect of BHA, BHT, TBHQ and PG on Growth and Toxigenesis of Selected Aspergilli

The antifungal effect of butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), tertiary butylhydroquinone (TBHQ) and propyl gallate (PC) alone or in combination on three toxigenic strains of aspergilli (NRRL 2999, NRRL 4123, NRRL 5835) and three nontoxigenic strains of aspergilli (NRRL 5521, NRRL 5917, NRRL 5918) was examined in a solid medium and in salami. BHT and PG (0.001,0.005,0.01,0.02g per plate) did not inhibit growth, sporulation, and toxigenesis of all six cultures. Aflatoxin production by toxigenic aspergilli (B₁, B₂, G₁ and G₂) in the presence of BHA, TBHQ, and a combination of BHA and TBHQ was reduced significantly (P < 0.05). In salami BHA, TBHQ alone or in combination at 100 ppm significantly (P < 0.05) decreased the aflatoxin production by aspergilli when compared to control samples. A combination of BHA and TBHQ showed synergistic inhibition in both studies (solid medium and salami studies).     

Aspergillus species from section Flavi isolated from soil at planting and harvest time in peanut‐growing regions of Argentina

Aspergillus species from section Flavi were isolated from soil samples in three peanut‐growing regions of Córdoba Province, Argentina. The samples were collected during the planting and harvest periods. Both total fungal population and Aspergillus species from section Flavi showed no significant differences between planting and harvest time in two of the regions evaluated. Only in one region were there significant differences in cfu g^?1 of total fungal population and Aspergillus species from section Flavi. A flavus was the dominant species isolated in all three localities during the planting and harvest periods. There were significant differences (p < 0.05) in the ratio of toxigenic and atoxigenic strains dependent on the period and the region evaluated. In one region, higher frequencies of toxigenic A flavus and A parasiticus in soil were found and a high contamination level of aflatoxins was detected in peanut seeds. Copyright © 2003 Society of Chemical Industry     

Efficiency and safety evaluation of photodegradation of Aflatoxin B1 on peanut surface

A photodegradation study of Aflatoxin B₁ (AFB₁) on peanut surface was performed under UV irradiation at different UV irradiation intensities. With an initial quantity of 10 ng of AFB_1, it can be degraded thoroughly within 80 min under the intensity of 800 μw cm^?2. The photodegradation pathway of AFB₁ on the peanut surface was proposed. Mutagenesis and cytotoxicity were assessed after exposure to different concentrations of AFB₁ and the mixtures of photodegradation products on the peanut surface. The results of the Ames and in vitro cytotoxicity assay, providing clues to the assessment of safety issues of UV method applied in AFB₁ decontamination, indicate that photodegradation products on the peanut surface has no toxicity, which can be explained by the differences in the chemical nature of the test compounds before and after UV irradiation.     

Impact of volatile compounds generated by essential oils on Aspergillus section Flavi growth parameters and aflatoxin accumulation

BACKGROUND: The advantage of essential oils is their bioactivity in the vapour phase, a characteristic that makes them attractive as possible fumigants for stored grain protection. In this study the antifungal and antiaflatoxigenic effects of the volatile fractions of five essential oils (EOs) were evaluated by vapour contact on Aspergillus section Flavi isolates. RESULTS: In maize meal extract agar the volatile fractions of Pimpinella anisum L. (anise), Pëumus boldus Mol. (boldus), Hedeoma multiflora Benth. (mountain thyme), Lippia turbinata var. integrifolia (Griseb.) (poleo) and Syzygium aromaticum L. (clove) were able to decrease the growth rate and lag phase of aflatoxigenic isolates. Boldus EO showed the best antifungal effect on Aspergillus section Flavi growth rate. In sterilised maize grains, boldus and poleo EOs showed antifungal effects on growth rate and aflatoxin accumulation. The volatile fraction of boldus EO completely inhibited the growth of isolates at water activity (a_w) levels of 0.955, 0.930 and 0.900, while poleo EO showed this effect only at the lower a_w levels (0.930 and 0.900). All aflatoxigenic isolates showed reduced total aflatoxin accumulation in the presence of boldus EO under all a_w conditions. CONCLUSION: These findings clearly indicate that the volatile fraction of boldus EO could be used to control aflatoxigenic fungi in stored maize. Copyright © 2009 Society of Chemical Industry     

Determination of synthetic phenolic antioxidants in soft drinks by stir-bar sorptive extraction coupled to gas chromatography-mass spectrometry

The synthetic phenolic antioxidants butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and tert-butyl hydroquinone (TBHQ) were pre-concentrated by stir-bar sorptive extraction and thermally desorbed (SBSE-TD) before analysis by GC-MS. Several parameters affecting the derivatisation step and both SBSE extraction and thermal desorption were carefully optimised. When the analyses of BHA and TBHQ in their acetylated, silylated and underivatised forms were compared, the best results were obtained when the in-situ derivatisation procedure with acetic anhydride was employed. Quantification was carried out using carvacrol as the internal standard, providing quantification limits of between 0.11 and 0.15 ng ml^?1, depending on the compound. Recovery assays for samples spiked at two concentration levels, 1 and 5 ng ml^?1, provided recoveries in the 81–117% range. The proposed method was applied in the analysis canned soft drinks and the analytes were found in five of the 10 samples analysed.     

Effectiveness of antioxidants on the stability of banana chips

The effectiveness of butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) in improving the stability of banana chips stored at 65°C were compared. Criteria used in the assessment of the stability of the chips included the determinations of peroxide, p-anisidine, acid and iodine values, E_1cm ^1% at 232 amd 268 nm and the C18:2/C16:0 ratio of oil extracted from banana chips. It was found that chips fried in refined, bleached and deodorised (RBD) olein containing BHA or BHT were more stable than chips fried in RBD olein without antioxidants. BHT was more effective than BHA in prolonging the shelf-life of of banana chips. The same order of effectiveness of the antioxidants was observed at 65°C and at room temperature (25°C).     

Kultur vonAspergillus parasiticus im Apfelsaft II. Einflu? von Butylhydroxyanisol (BHA) and Butylhydroxytoluol (BHT) auf Pilzwachstum and Aflatoxin-Biosynthese

Zusammenfassung Aspergillus parasiticus NRRL 2999 wurde im Apfelsaft (aus Sirup) in Gegenwart von BHA bzw. BHT (100, 200, 300 oder 400 mg/1) bis zu 15 Tage bei 25 °C ruhend bebrütet. Myceltrockengewicht, pH and Konzentrationen der Aflatoxine B₁ und G₁ wurden in dreitägigen Abständen bestimmt. Der pH-Anfangswert von 2,5 blieb durchwegs unverändert. BHA unterdrückte das Wachstum and die Toxinanhäufung in der beobachteten Zeitspanne. Es kam jedoch zu konzentrationsabhängigen Wachstumsverzögerungen und zu früheren Toxin-Höchst-werten als in der Kontrollreihe, was auf eine Anpassung ans Milieu hinweist. BHT führte erst ab 200 mg/l zu einer ca. 25%igen Wachstumshemmung (Löslich-keitsgrenze von BHT zwischen 200 and 300 mg/1) und bei 200 mg/l zur ca. 45%igen Hemmung der Toxinanhäufung. Bei 100 mg/l wirkte BHT fördernd auf die Toxinsynthese (1,90 mal mehr G1 and 6,65 mal mehr B₁ als in der Kontrollreihe). Bei allen getesteten Konzentrationen von BHA bzw. BHT sowie in der Kontrollreihe wurde Aflatoxin G₁ starker als B₁ angehauft.

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The cultivation ofAspergillus parasiticus on apple juice II. Influence of butylated hydroxyanisole and butylated hydroxytoluene on fungal growth and aflatoxin biosynthesis

Summary Aspergillus parasiticus (NRRL 2999) was incubated in apple juice (from syrup), quiescently at 25 °C for up to 15 days in the presence of butylated hydroxyanisole (BHA) or butylated hydroxytoluene (BHT) at concentrations of 100, 200, 300, or 400 mg/l. Mycelial dry weight, pH and concentration of aflatoxin B₁ and G₁ were measured every 3 days with the initial pH of 2.5 remaining unchanged in all samples. BHA suppressed fungal growth and toxin accumulation during the observed incubation period. However, a concentration-dependent growth delay and earlier peaks of toxin accumulation suggested environmental adaptation of the mould. BHT (from 200 mg/l onwards), led to growth inhibition by about 25% (solubility limit of BHT lies between 200 and 300 mg/1), and at a concentration of 200 mg/1, it led to a reduction of toxin accumulation by approximately 45%. At 100 mg/l, however, BHT stimulated aflatoxin production (1.90 times more G, and 6.65 times more B₁ than in the controls). At all tested concentrations of BHA or BHT, as well as in the controls, the accumulation of aflatoxin G₁, without exception, surpassed that of B₁.

     

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.     

Kinetics of mould growth in the stored barley ecosystem contaminated with Aspergillus westerdijkiae,Penicillium viridicatum and Fusarium poae at 23–30 °C

BACKGROUND: Owing to the lack of a rapid method for determining fungi on cereals, the best way to enhance the safety and nutritive value of stored grain is to develop prognostic tools based on the relationship between easily measurable online parameters, e.g. water activity (a_w) and temperature (t) of grain, and fungal growth. This study examined the effect of unfavourable temperature (23 and 30 °C) and humidity (0.80–0.94 a_w) storage conditions on mould growth in the stored barley ecosystem with its adverse microbiological state provided by contamination with Aspergillus westerdijkiae, Penicillium viridicatum and Fusarium poae. RESULTS: Among the applied storage parameters, a_w turned out to be the main factor affecting mould development. The longest lag phase and period of fungal activation were observed for grain with 0.80 a_w, which was not threatened with fungal development for at least 30 days. However, in grain with 0.92 and 0.94 a_w, fungal activation occurred within 24–48 h. CONCLUSION: The obtained data and the identification of critical points in mould growth may be used to develop a control system for the postharvest preservation of barley based on a_w and temperature of grain, which are easy to measure in practice. © 2012 Society of Chemical Industry     

Escherichia coli O157: H7 Growth in Laboratory Media as Affected by Phenolic Antioxidants

Five strains of Escherichia coli O157:H7 with ATCC 11775 E. coli were grown in brain heart infusion (BHI) broth (pH 5.8, adjusted with citric acid) and treated with butylated hydroxyanisole (BHA), butylated hy-droxytoluene (BHT), tertiary butylhydroquinone (TBHQ), and propyl gallate (PG) individually or combined. Additives ranged from 100–400 ppm with inocula levels between 5 and 104 CFU/mL in tissue culture plates or in flasks; samples were incubated at 4°C or 37°C for 24 hr. Additive antimicrobial efficacy varied with inoculum level and incubation temperature. BHA at <200 ppm was bactericidal on all strains. Poly-hydroxyl additives (TBHQ, PG) were less effective at 4°C. BHA-BHT combinations were synergistic at 4°C.     

Integrated management of insect vectors of Aspergillus flavus in stored maize, using synthetic antioxidants and natural phytochemicals

The purpose of this study was to investigate the insecticidal activity of two benzoic acids 2(3)-tert-butyl-4 hydroxyanisole (BHA) and 2,6-di(tert-butyl)-p-cresol (BHT); two phenolic acids 3-phenyl-2-propenoic acid (CA) and trans-4-hydroxy-3-methoxycinnamic acid (FA) and two essential oils of Eugenia caryophyllata (clove tree) and Thymus vulgaris (thyme) against Sitophilus zeamais, Tribolium confusum and Rhyzopertha dominica, vector carriers of aflatoxigenic fungi in stored maize. The susceptibility of insects, the frequency of isolation of Aspergillus section Flavi in insects and maize, and the analysis of aflatoxin B₁ in maize were determined. BHA, BHT, BHA/BHT mixture and the natural phytochemicals AF and AF/AC mixture showed the highest insecticidal activity against S. zeamais, T. confusum and R. dominica after 120 days of incubation. The insecticidal efficacy of the volatile fraction of essential oils of clove and thyme showed less inhibition. There was no contamination of Aspergillus section Flavi in dead and live insects collected from maize treated with BHA. No aflatoxin B₁ accumulation was detected in the control and treatments. The information obtained shows that these substances have the potential to control pest insect vectors of aflatoxigenic fungi in stored maize in microcosms during 120 days.     

Effect of antioxidants and competing mycoflora on Fusarium verticillioides and F. proliferatum populations and fumonisin production on maize grain

This study was carried out to determine the temporal effect of the antioxidants butylated hydroxyanisol (BHA) and propyl paraben (PP) at doses of 500 and 1000 μg/g on the growth of Fusarium verticillioides and F. proliferatum inoculated on natural maize grain in the presence of the competing mycoflora and fumonisin production at 0.98 and 0.95 water activity (a_w) over a 28-day storage period. The reduction in the log colony forming units (CFU) of Penicillium, Aspergillus and Fusarium populations was 10-100 fold depending on dose of BHA or PP, a_w and time. However, the populations of all three groups were higher at 0.98 a_w than 0.95 a_w. BHA at 500 μg/g and 0.95 a_w reduced the fumonisin content by 82% after 7-14 days incubation, but at the end of the experimental period the reduction was only 32%. A higher reduction in the level of fumonisin produced (77%) was achieved with BHA at 1000 μg/g after 28 days. PP at 500 and 1000 μg/g decreased fumonisin production throughout the incubation period in the drier treatment, but at 0.98 a_w control of toxin production was only achieved after 7-14 days. The reduction in the fumonisin levels could be due to the combined effect of antioxidants, and the competing mycoflora, mainly Aspergillus and Penicillium species.     

Environmental factors affect efficacy of some essential oils and resveratrol to control growth and ochratoxin A production by Penicillium verrucosum and Aspergillus westerdijkiae on wheat grain

This study determined the efficacy of three essential oils (bay, clove and cinnamon oil) and the antioxidant resveratrol (0–500 μg g⁻¹) on the control of growth and ochratoxin A (OTA) production by Penicillium verrucosum and Aspergillus westerdijkiae (=A. ochraceus) under different water activity (a_w, 0.90, 0.95, 0.995), and temperature (15, 25 °C) conditions on irradiated wheat grain. The most effective treatment (resveratrol) was then tested on natural grain. The ED₅₀ values for growth inhibition by the oils were 200–300 μg g⁻¹ at the a_w and the temperatures tested. For resveratrol, this varied from <50 μg g⁻¹ at 0.90–0.95 a_w to >350 at 0.995a_w at both temperatures. The ED₅₀ values for the control of OTA were slightly lower than for control of growth, with approx. 200 μg g⁻¹ required for the oils and 50–100 μg g⁻¹ of the antioxidant, at 0.90/0.95a_w and both temperatures. In wet grain (0.995a_w), higher concentrations were required. For growth there were statistically significant effects of single-, two- and three-way interactions between treatments except for concentration×temperature and concentration×temperature×essential oil/antioxidant treatment. For OTA control, statistically significant treatments were a_w, temperature×a_w, concentration×temperature, treatment×concentration, and three-way interaction of concentration×a_w×treatment for P. verrucosum and A. westerdijkiae. Subsequent studies were done with the best treatment (resveratrol, 200 μg g⁻¹) on natural wheat grain with either P. verrucosum or A. westerdijkiae at 0.85–0.995a_w and 15/25 °C over 28 days storage. This showed that the populations of the mycotoxigenic species and OTA contamination could be reduced by >60% by this treatment at the end of the storage period.