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Methyl bromide as a microbicidal fumigant for tree nuts
Abstract:
Methyl bromide (MeBr) has broad microbicidal activity, but its use as a disinfectant for food is limited by the resulting bromide residues. Increasing the MeBr concentration, exposure temperature, or exposure period of a treatment tended to increase both the microbicidal efficacy of MeBr and the bromide residues. Its sporicidal activity was less at high than at low relative humidity within the range of 20 to 99%. Both the efficacy and the resulting residues of a MeBr treatment varied inversely with the load of product in a fumigation chamber due to sorption of the fumigant. Fumigation tests with almond kernels inoculated with Escherichia coli or Salmonella typhimurium indicated that MeBr can be used to disinfect whole nut kernels without resulting in excessive bromide residues, although the MeBr level necessary is higher than that normally used for insect control.
Insights
Methyl bromide (MeBr) effectively disinfects food but leaves residues. Higher concentrations increase efficacy and residues, while humidity and product load affect results. Almond kernels can be disinfected with higher MeBr levels.
Area of Science:
- Food science
- Microbiology
- Chemical fumigation
Background:
- Methyl bromide (MeBr) exhibits broad microbicidal activity, making it a potential food disinfectant.
- However, its application is constrained by the generation of undesirable bromide residues.
- Factors influencing MeBr efficacy and residue levels require detailed investigation for safe food applications.
Purpose of the Study:
- To evaluate the efficacy of methyl bromide as a food disinfectant.
- To assess the impact of various factors on MeBr microbicidal activity and bromide residue formation.
- To determine optimal conditions for using MeBr to disinfect food products, specifically whole nut kernels.
Main Methods:
- Investigated the effect of MeBr concentration, exposure temperature, and duration on microbicidal efficacy and bromide residues.
- Assessed the influence of relative humidity (20-99%) on MeBr's sporicidal activity.
- Examined the impact of product load in a fumigation chamber on MeBr sorption, efficacy, and residues.
- Conducted fumigation tests using almond kernels inoculated with Escherichia coli and Salmonella typhimurium.
Main Results:
- Increased MeBr concentration, temperature, or exposure time enhanced both microbicidal efficacy and bromide residues.
- Sporicidal activity of MeBr was reduced at higher relative humidity levels.
- Higher product load in fumigation chambers led to decreased MeBr efficacy and residue levels due to sorption.
- Disinfection of almond kernels with MeBr was feasible without excessive bromide residues, though higher concentrations than typically used for insect control were necessary.
Conclusions:
- Methyl bromide can be utilized for disinfecting whole nut kernels, such as almonds.
- Optimizing MeBr treatment requires careful consideration of concentration, temperature, exposure time, humidity, and product load to balance efficacy and minimize residues.
- Further research may refine MeBr application protocols for food disinfection, ensuring safety and compliance with residue limits.