Inhibitory effect of Cynara cardunculus L. extract on aflatoxin B1 production by Aspergillus parasiticus in sesame (Sesamum indicum L.)

Aflatoxin B₁ has been considered as the most potent liver carcinogen for humans. One factor that stimulates the production of aflatoxins in oilseed products, such as sesame seeds and their products is the presence of high levels of fatty acids. This work presents further evidence that sesame is a favorable substrate for aflatoxin B₁ production by Aspergillus parasiticus. Moreover, the use of wild artichoke (Cynara cardunculus L.) extract was examined showing inhibition of aflatoxin B₁ production in both sesame and yeast extract sucrose medium, inoculated with A. parasiticus. More specifically, the inhibition of aflatoxin B₁ production by A. parasiticus in sesame seeds paste was 99.6% and in yeast extract sucrose medium it was 99.4%.     

Susceptibility of Date Fruits (Phoenix dactylifera) to Aflatoxin Production

Segments of fruits from 12 varieties of date (Phoenix dactylifera) and three stages of maturation were inoculated with a toxigenic strain of Aspergillus parasiticus. During growth at 28°C for 10 days, 8 varieties supported appreciable aflatoxin production at the Khalal stage—the most popular stage for direct human consumption, with a maximum value in excess of 300 μg g^-1 of fruit. Marked differences in susceptibility to infection and/or aflatoxin production were observed between varieties and/or stage of maturation. It was concluded that toxigenic aspergilli could proliferate on any date fruits that suffered mechanical damage in the field or during harvesting, and hence that such fruits should be considered as likely to be unfit for human or animal consumption. © 1997 SCI.     

Aspergillus Parasiticus Growth and Aflatoxin Production on Dehydrated Taro

A study was made of Aspergillus parasiticus growth and aflatoxin production on four taro media. The critical equilibrium relative humidity (ERH) for natural mold growth on unsterilized dehydrated taro was 88% at 20°C. However, nontoxigenic A. parasiticus NRRL 1957 did not grow at this ERH on dehydrated raw taro incubated at 20°, 30°, or 40°C. Instead, the growth of A. parasiticus NRRL 1957 on dehydrated taro was optimum at 30°C and an ERH of 96%. Aflatoxin production by toxigenic A. parasiticus NRRL 2999 was investigated on four taro media under optimal growth conditions. Only moderate quantities of aflatoxins were produced by A. parasiticus NRRL 2999 on uncooked dehydrated taro, but cooking or supplementation with peptone stimualted mycelial growth and aflatoxin production slightly. Nevertheless, growth and aflatoxin production on cooked or peptone-supplemented taro media was low.     

Effects of pulsed electric field processing on the quality and microbial inactivation of sour cherry juice

Pulsed electric fields (PEF) processing of sour cherry juice with the measurement of pH, ºBrix, titratable acidity, conductivity, colour (L*, a* and b*), nonenzymatic browning index, metal ion concentration, total ascorbic acid and total antocyanin content as well as microbial inactivation were searched in the study. Applied PEF treatment parameters did not cause any significant difference on measured properties of sour cherry juice (P > 0.05). On the other hand, inactivation of Escherichia coli O157:H7, Staphylococcus aureus, Listeria monocytogenes, Erwinia carotowora, Pseudomonas syringae subs. syringae, Botrytis cinerea and Penicillum expansum significantly increased with increased electric field strength and treatment time (P ≤ 0.05). It was revealed that PEF is a viable option to process sour cherry juice with significant amount of microbial inactivation and without adversely affecting important physical and quality parameters.     

Aflatoxin production in three selected samples of triticale,wheat and rye grown in Argentina

Little is known about mycotoxin contamination of triticale, a hybrid resulting from crossing wheat and rye. The purpose of the present work was to evaluate triticale as a substrate for aflatoxin accumulation in comparison with its parents. Aflatoxin (B₁, B₂, G₁ and G₂) accumulation curves were obtained for the three substrates inoculated with Aspergillus parasiticus NRRL 2999 and incubated at 25 °C and water activity 0.925 for 10 weeks. Wheat and triticale were poor substrates for aflatoxin production. Rye was more prone than the other substrates to fast colonisation by A parasiticus and accumulated larger aflatoxin quantities over the whole incubation period. The maximum aflatoxin concentration in rye (11 840 µg kg⁻¹) was significantly larger (p < 0.05) than those obtained in wheat (2150 µg kg⁻¹) and triticale (2850 µg kg⁻¹). © 2000 Society of Chemical Industry     

Physico-Chemical,antioxidant activities,textural, and sensory properties of yoghurt fortified with different states and rates of pomegranate seeds (Punica granatum L.)

This study examines the effects of incorporating fresh, frozen, osmodehydrated, and dried pomegranate seeds, at different concentrations (5, 10, and 20%) on the physicochemical, antioxidant, textural, and sensory properties of yoghurt. Antioxidant activity, pH, acidity, syneresis, and color of yoghurt were also evaluated during the storage (28 days) at 4°C. The principal component analysis (PCA) was performed to assess the correlations between different yoghurt formulation and their sensory attributes. Data showed that the addition of pomegranate seeds reduced pH and modified the chromatics coordinate (L*, a*, b*, C*, h°) and firmness of the yoghurt samples. In addition, acidity, °Brix, and syneresis increased compared to the control. Thanks to their high anthocyanin content, pomegranate seeds considerably improved the antioxidant activity essentially for yoghurt enriched with frozen seeds. In addition, the supplementation of 20% of frozen seeds into yoghurt was the most appreciated by panelists and improved the sensory properties in comparison to other formulation. According to PCA, taste and appearance were the main criteria for the overall acceptability of yoghurt. After 28 days of storage, the reddish color was reinforced; however, the antioxidant activity of yoghurts was reduced. Overall, it can be concluded that pomegranate seeds can be used as a natural ingredient to develop a novel yoghurt with high nutritional properties.     

Potential of aflatoxin B1 production by Aspergillus flavus strains on commercially important food grains

In this study, we investigated the potential of aflatoxin B₁ (AFB1) production by five Aspergillus flavus strains previously isolated from sorghum grains on cereals (barley, maize, rice, wheat and sorghum), oilseeds (peanuts and sesame) and pulses (greengram and horsegram). Five strains of A. flavus were inoculated on all food grains and incubated at 25 °C for 7 days; AFB1 was extracted and estimated by enzyme‐linked immunosorbent assay. All A. flavus strains produced AFB1 on all food grains ranging from 245.4 to 15 645.2 μg kg^?1. Of the five strains tested, strain Af 003 produced the highest amount of AFB1 on all commodities ranging from 2245.2 to 15 645.2 μg kg^?1. Comparatively, the AFB1 accumulation was high on rice grains ranging from 3125.2 to 15 645.2 μg kg^?1, followed by peanuts ranging from 2206.2 to 12 466.5 μg kg^?1. Less AFB1 accumulation was observed in greengram and sesame seeds ranging from 645.8 to 2245.2 and 245.4 to 2890.6 μg kg^?1, respectively. Our results showed that all food grains tested are susceptible to A. flavus growth and subsequent AFB1 production.     

Ultraviolet and Pulsed Electric Field Treatments Have Additive Effect on Inactivation of E. coli in Apple Juice

ABSTRACT: Apple juice inoculated with Escherichia coli ATCC 23472 was processed continuously using either ultraviolet (UV), high‐voltage pulsed electric field (PEF), or a combination of the PEF and UV treatment systems. Apple juice was pumped through either of the systems at 3 flow rates (8, 14, and 20 mL/min). E. coli was reduced by 3.46 log CFU/mL when exposed in a 50 cm length of UV treatment chamber at 8 mL/min (2.94 s treatment time with a product temperature increase of 13 °C). E. coli inactivation of 4.87 log CFU/mL was achieved with a peak electric field strength of 60 kV/cm and 11.3 pulses (average pulse width of 3.5 μs, product temperature increased to 52 °C). E. coli reductions resulting from a combination treatment of UV and PEF applied sequentially were evaluated. A maximum E. coli reduction of 5.35 log CFU/mL was achieved using PEF (electrical field strength of 60 kV/cm, specific energy of 162 J/mL, and 11.3 pulses) and UV treatments (length of 50 cm, treatment time of 2.94 s, and flow rate of 8 mL/min). An additive effect was observed for the combination treatments (PEF and UV), regardless of the order of treatment (P > 0.05). E. coli reductions of 5.35 and 5.30 log CFU/mL with PEF treatment (electrical field strength of 60 kV/cm, specific energy of 162 J/mL, and 11.3 pulses) followed by UV (length of 30 cm, treatment time of 1.8 s, and flow rate of 8 mL/min) and UV treatment followed by PEF (same treatment conditions), respectively. No synergistic effect was observed.     

Effects of Pulsed Electric Fields on the Activities of Microorganisms and Pectin Methyl Esterase in Orange Juice

Orange juice was treated with pulsed electric fields (PEF) in a pilot‐plant system to optimize PEF‐processing conditions for maximum microbial inactivation and to investigate the effects of PEF on pectin methyl esterase (PME) activity. Electric‐field strengths of 20,25,30, and 35 kV/cm and total treatment times of 39, 49, and 59 μs were used. Higher electric‐field strengths and longer total treatment times were more effective to inactivate microorganisms and PME (p < 0.05). PEF treatment of orange juice at 35 kV/cm for 59 μs caused 7–log reductions in total aerobic plate count and yeast and mold counts. About 90% of PME activity was inactivated by PEF treatment at 35 kV/cm for 59 μs. PEF‐treated orange juice at 35 kV/cm for 59 ms did not allow growth of microorganisms and recovery of PME at 4, 22, and 37 °C for 112 d.     

Induction of chitinase in response to Aspergillus infection in sorghum (Sorghum bicolor (L) Moench)

Chitinase is an antifungal protein which is induced in higher plants during infection and stress. In this paper the induction of chitinase activity in response to infection by Aspergillus parasiticus (NRRL 2999) in six sorghum (Sorghum bicolor (L) Moench) genotypes and its association with aflatoxin production were investigated. Chitinase was induced in all six genotypes (two each of red, yellow and white sorghum) when infected by A parasiticus (NRRL 2999). The induction of chitinase activity was highest in the white cultivars, followed by the yellow and red genotypes, compared with healthy grains. In the white cultivars the chitinase activity increased on the 6th and 9th days after infection and was four‐ to fivefold higher than in healthy grains. The total aflatoxin produced was lower in the red genotypes than in the yellow and white genotypes. The white genotypes showed maximum total aflatoxin production at 6 days after infection. The aflatoxins produced in the white genotypes were comparable to those in the red genotypes. There was a significant positive correlation between chitinase activity and aflatoxin production in red sorghum (r² = 0.600, p ≤ 0.001) and white sorghum (r² = 0.411, p ≤ 0.001). Maximum chitinase activity was observed on day 12 in all genotypes under healthy conditions. Copyright © 2004 Society of Chemical Industry     

Inhibitory effect of phenolics extracted from sorghum genotypes on Aspergillus parasiticus (NRRL 2999) growth and aflatoxin production

The inhibitory activity of bioactive polyphenols present in six sorghum genotypes—two red (AON 486 and IS 620), two yellow (LPJ and IS 17779) and two white (SPV 86 and SPV 462) varieties—on Aspergillus parasiticus (NRRL 2999) growth and aflatoxin production was evaluated. In the first experiment the production of aflatoxins in the six sorghum genotypes after removal of surface phenolics by acidic methanol treatment was studied and compared with that in untreated grains. Aflatoxin production was found to be fourfold higher in treated grains. The total phenols and bioactive polyphenols extracted by acidic methanol were quantified using the Folin–Denis method and the bovine serum albumin–benzidine conjugate procedure respectively. In the second experiment the effect of extracted sorghum phenolics under in vitro conditions on fungal growth and aflatoxin production was studied at two concentrations (0.01% and 0.1%) of phenolics. Extracted phenolics added to yeast extract sucrose (YES) medium at 0.1% concentration showed an inhibitory effect on aflatoxin production. At 0.01% phenolic concentration, aflatoxin production was minimal on day 3 after infection. At other time points the aflatoxin content was similar to that in the control. At 9 days after infection the fungal biomass in IS 620 was significantly lower than that in the control. At 0.1% phenolic concentration, aflatoxin production was minimal and the red genotype IS 620 showed maximum resistance. Fungal biomass was lowest at all growth stages in IS 620 as compared with the control. Polyphenol oxidase (PPO) activity was not detected in A. parasiticus grown on YES medium (control). PPO activity was not induced in A. parasiticus by the addition of phenolics to the liquid culture medium (no PPO activity was detected in the culture medium). The inhibitory activity of bioactive polyphenols could be attributed to the lack of PPO enzyme in this fungus. Copyright © 2007 Society of Chemical Industry     

Production of aflatoxins in sausage,salami, sucuk and kavurma

Forty nine meat product samples were examined for the fungal genera. Penicillium sp. was detected in 74.8% of samples. No sample contained Aspergillus parasiticus or Aspergillus flavus. Production of aflatoxins in sausage, salami, sucuk and kavurma by A. parasiticus and A. flavus was studied at different temperatures. A. parasiticus and A. flavus produced no aflatoxins on meat products samples at 15°C. Sucuk was a poor substrate for A. parasiticus and A. flavus at 25°C. Sausage, salami and kavurma were favorable substrates for aflatoxin production by A. parasiticus at 25°C.     

Inactivation of Yersinia enterocolitica by pulsed electric fields

The influence of growth conditions, treatment medium characteristics and PEF process parameters on the lethal effect on Yersinia enterocolitica of pulsed electric fields (PEF) treatments in batch has been investigated. Growth phase, temperature of growth, pH, conductivity of the treatment medium, pulse width and frequency of pulses did not influence the sensitivity of Y. enterocolitica to PEF. However, an A_w decrease from >0.99 to 0.93 of the treatment medium increased the PEF resistance of Y. enterocolitica with 3.5 log₁₀ cycles after a treatment of 22 kV/cm, 800 μs and 880 kJ/kg. Inactivation of Y. enterocolitica increased with the field strength, treatment time and total specific energy up to a maximum of 6 log₁₀ cycles after 28 kV/cm, 2000 μs and 3559 kJ/kg. A nonlinear relationship was found among the survival fraction and the treatment time or the specific energy that was accurately described by a mathematical model based on the Weibull distribution. The inactivation of Y. enterocolitica by PEF was characterized by maximum field strength thresholds. Above these thresholds, specific energy necessary to obtain a given level of inactivation scarcely decreased by increasing the electric field strength, and inactivation of Y. enterocolitica only depended on the specific energy applied.     

Optimising the inactivation of grape juice spoilage organisms by pulse electric fields

The effect of some pulsed electric field (PEF) processing parameters (electric field strength, pulse frequency and treatment time), on a mixture of microorganisms (Kloeckera apiculata, Saccharomyces cerevisiae, Lactobacillus plantarum, Lactobacillus hilgardii and Gluconobacter oxydans) typically present in grape juice and wine were evaluated. An experimental design based on response surface methodology (RSM) was used and results were also compared with those of a factorially designed experiment. The relationship between the levels of inactivation of microorganisms and the energy applied to the grape juice was analysed. Yeast and bacteria were inactivated by the PEF treatments, with reductions that ranged from 2.24 to 3.94 log units. All PEF parameters affected microbial inactivation. Optimal inactivation of the mixture of spoilage microorganisms was predicted by the RSM models at 35.0 kV cm^− 1 with 303 Hz pulse width for 1 ms. Inactivation was greater for yeasts than for bacteria, as was predicted by the RSM. The maximum efficacy of the PEF treatment for inactivation of microorganisms in grape juice was observed around 1500 MJ L^− 1 for all the microorganisms investigated. The RSM could be used in the fruit juice industry to optimise the inactivation of spoilage microorganisms by PEF.     

Aspergillus and aflatoxin in groundnut (Arachis hypogaea L.) and groundnut cake in Eastern Ethiopia

This study was conducted to assess major Aspergillus species and aflatoxins associated with groundnut seeds and cake in Eastern Ethiopia and evaluate growers’ management practices. A total of 160 groundnut seed samples from farmers’ stores and 50 groundnut cake samples from cafe and restaurants were collected. Fungal isolation was done from groundnut seed samples. Aspergillus flavus was the dominant species followed by Aspergillus parasiticus. Aflatoxin analyses of groundnut seed samples were performed using ultra performance liquid chromatography; 22.5% and 41.3% of samples were positive, with total aflatoxin concentrations of 786 and 3135 ng g^?1 from 2013/2014 and 2014/2015 samples, respectively. The level of specific aflatoxin concentration varied between 0.1 and 2526 ng g^?1 for B₂ and B₁, respectively. Among contaminated samples of groundnut cake, 68% exhibited aflatoxin concentration below 20 ng g^?1, while as high as 158 ng g^?1 aflatoxin B₁ was recorded. The study confirms high contamination of groundnut products in East Ethiopia.     

Effect of Cycling Temperatures on Aflatoxin Production by Aspergillus parasiticus and Aspergillus flavus in Rice and Cheddar Cheese

Initiation of growth, sporulation and aflatoxin production at cycling temperatures took less time than at 15°C but more than at 18°C and 25°C. A. parasiticus produced more aflatoxins on rice under cycling temperatures than at 25°C, 18°C or 15°C, while A. flavus produced less aflatoxin under cycling temperatures. A. parasiticus produced more aflatoxins on cheese under cycling temperatures than at 18°C or 15°C, but much less than at 25°C. A. flavus produced less aflatoxins on cheese under cycling temperatures than at 18°C and 25°C. Both organisms produced trace amounts of toxins at 15°C on cheese. Preincubation at 25°C for 2 days before temperature cycling did not increase aflatoxin production on rice but increased production on cheese. The rate of aflatoxin production on cheese decreased as the temperature decreased. No growth, sporulation or aflatoxin production was observed at 5°C on either rice or cheese.     

INACTIVATION OF ESCHERICHIA COLI IN SKIM MILK BY HIGH INTENSITY PULSED ELECTRIC FIELDS

The inactivation of microorganisms is the most important function in the processing of milk and dairy products. Traditionally, this purpose is realized by thermal treatment, but heat produces alterations to flavor and taste in addition to nutrient loss. The high intensity pulsed electric field (PEF) treatment should be a good alternative to heat because demonstrations have shown PEF can reduce the Escherichia coli survival fraction in aqueous solutions and model foods. In this study, PEF treatment was found to inactivate E. coli in skim milk (inoculum 10⁹ CFU/mL) at 15C. The microorganism inactivation satisfied Hülsheger's model following a first order kinetic for both the electric field intensity and number of pulses when skim milk inoculated with E. coli was treated in a static or continuous flow chamber. PEF treatment in a continuous system when the critical electric field (E_c) and minimum number of pulses (n_min) were 12.34 kV/cm and 2.7 at 30 kV/cm and 30 pulses (0.7–1.8 μs pulse width) inactivated more microorganisms than in a static system. It has also been proven that increasing the pulse duration increases the E. coli inactivation. The inactivation of E. coli using PEF is more limited in skim milk than in a buffer solution when exposed to similar treatment conditions of field intensity and number of pulses due to the complex composition of skim milk, its lower electrical resistivity and the presence of proteins.     

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     

Microbial inactivation of E. coli cells by a combined PEF–HPCD treatment in a continuous flow system

A laboratory scale continuous flow unit was set up and used to study the effect of pulsed electric fields (PEF) pre-treatments on microbial inactivation by high pressure carbon dioxide (HPCD) processing with the aim of investigating the synergistic effect of the combined treatment. McIlvaine buffer solution inoculated with Escherichia coli cells ATCC26 was pre-treated with PEF (25 °C) at different field strength (E = 6–12 kV/cm) and energy input (W_T = 10–40 J/mL) and then processed with HPCD (25 °C) at pressures of 8.0, 14.0 and 20.0 MPa and holding times of 4, 7 and 11 min.Results showed that treating the microbial suspension only with PEF, the inactivation level slightly increased with increasing the field strength and energy input with no significant effect of the pressure applied. The maximum inactivation level obtained was 2.25 Log-cycles at 12 kV/cm and 40 J/mL. When the bacterial cells were treated only with HPCD, the inactivation level was almost independent on the pressure of CO₂, and gradually increased with increasing the holding time up to a maximum value of 2.41 Log-cycles. The combination of PEF and HPCD treatment resulted in a marked increase of the microbial inactivation with increasing the field strength, energy input, holding time and operative pressure. A clear synergistic effect was evident when holding time was longer than 4 min, regardless the intensity of the PEF treatment applied.Industrial relevanceConsumers demand for fresh and natural products forces food manufacturers to investigate milder preservation processes and stimulate the current trend to use hurdle technologies. Pulsed electric field (PEF) and high pressure carbon dioxide (HPCD) are emerging non-thermal technologies which have antimicrobial capabilities when applied alone or in combination with other physicochemical hurdles. The present work demonstrated, for the first time, the feasibility of combined PEF-HCPD process based on the coupling of a PEF pretreatment stage to HPCD treatment in a continuous flow unit. The results support the view that the combined process is able to induce substantial microbial inactivation at mild treatment conditions and at room temperature suggesting the idea that this process could be applied to foods with thermosensitive components.