Physicochemical treatments for the reduction of aflatoxins and Aspergillus niger in corn grains (Zea mays)

Abstract

BACKGROUND Corn grains are commonly contaminated with mycotoxins and fungi. The purpose of this study was to evaluate the reduction of aflatoxins B1, B2, G1, and G2 and the inhibition of Aspergillus niger in corn grains using ultrasound, ultraviolet (UV) radiation, electrolyzed water, and sodium bicarbonate. The determination of aflatoxins was performed by high‐performance liquid chromatography with fluorescence detection and postcolumn derivatization, and analysis of A. niger was performed by evaluating mycelial growth in potato dextrose agar. The best treatment for reducing aflatoxins and inhibiting mycelial growth was evaluated in corn contaminated with A. niger. RESULTS The results show a significant reduction in aflatoxins in the following order: sodium bicarbonate > ultrasound > UV > electrolyzed water for aflatoxins B1, B2, and G2. For aflatoxin G1, the order of reduction was sodium bicarbonate > ultrasound > electrolyzed water > UV, with maximum values between 70.50% and 87.03% reached with sodium bicarbonate; for the other treatments, the reduction was between 51.51% and 65.44%. Regarding the fungus, the order of inhibition in the control of mycelial growth was sodium bicarbonate > ultrasound > electrolyzed water > UV in corn grains, and inhibition of mycelial growth was obtained at a sodium bicarbonate concentration of 3.0 g L−1. CONCLUSION Sodium bicarbonate, electrolyzed water, ultrasound, and UV radiation inhibited the growth of A. niger on potato dextrose agar and reduced the contents of aflatoxins B1, B2, G1, and G2 in vitro. Sodium bicarbonate showed an ability to inhibit mycelial growth in corn grains. © 2020 Society of Chemical Industry

Isolation, identification, biological characteristics, and antifungal efficacy of sodium bicarbonate combined with natamycin on Aspergillus niger from Shengzhou nane (Prunus salicina var. taoxingli) fruit

“…Similarly, SBC also showed a good ability to inhibit germ tube elongation, mycelial expansion, and hypha production of Penicillium expansum , thus affecting the survival of microbial cells ( Lai et al, 2015 ). Castro-Ríos et al (2021) reported that 3.0 g/L SBC presented a significant reduction in A. niger growth 72 h after inoculation. Some researchers speculated that pH may be involved in the inhibitory activity of SBC since SBC could change the pH of the growth environment of microbes ( Lyousfi et al, 2022 ).…”

“…Moreover, previous studies showed that bicarbonate (HCO 3 − ) also could dissipate the transmembrane pH gradient and dissipate ∆ψm and ∆pH, indicating that it was a selective dissipater of the pH gradient of the proton motive force across the cytoplasmic membrane of bacteria ( Farha et al, 2017 ). Additionally, SBC can inactivate fungal extracellular enzymes since they can act directly on cell membranes and lead to an alteration of cellular physiology Castro-Ríos et al, 2021 . In addition, bicarbonate salts could reduce the intense pressure of fungal cells by increasing osmotic stress and causing the collapse and contraction of hyphae and spores ( Alvindia, 2013 ).…”

Ultraviolet radiation and generally recognized as safe (GRAS) preservatives for inactivation of Aspergillus niger in vitro and corn dough

“…The concentrations were selected following the recommendations for food additives for human consumption (Food and Agriculture Organization, 2018). The UV treatment was carried out by exposing a fragment of the fungus to radiation for 10 min, later inoculated on the PDA agar according to the methodology of Castro-Ríos et al (2021).…”

“…A portion of the mycelium of A. niger was taken with a stylet and was inoculated by a central puncture in the PDA Agar with the treatment of interest (Table 1); in addition, they were incubated at 22 °C, for 72 h (Castro-Ríos et al, 2021). The evaluations were carried out by measuring mycelial radial growth of the central colony in millimeters at 24, 48, and 72 h. When satellite colonies were present, these were not measured; a simple macroscopic description of them was made, and their presence was reported.…”

“…Montville & Shih (1991) assessed the inhibition of A. ochraceus with 1% and 2% of sodium bicarbonate in re-hydrated corn up to 23% of humidity; the authors found that this salt had an inhibitory effect on the fungus. Castro-Ríos et al (2021) recently evaluated chemical treatments like sodium bicarbonate, electrolyzed water, and physical treatment ultrasound and UV in the reduction of inhibition in the control of mycelial growth of A. niger in corn grains and reduction of Aflatoxins in vitro; sodium bicarbonate achieved complete inhibition of the fungus and a reduction of 87.03% of aflatoxins. The inhibition of microorganisms by bicarbonate has been attributed to an impact on germination, mycelial growth, and inactivation of enzymes, due to an increase in pH in the medium (Alvindia, 2013;Smilanick et al, 1999).…”