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Uniform Strategy for Decontamination of Stored Food

Investigators
Yalamanchili, Rattaya
Institutions
Lynntech, Inc
Start date
2005
End date
2006
Objective
More than 400 million tons (15 billion bushels) of grain are stored every year in the United States. Insects and fungi create serious quality problems in stored grains, and annual storage losses are estimated at more than $500 million. , These infestations not only cause physical degradation of the food; they also create ideal conditions for the post-harvest production and accumulation of mycotoxins, specifically the highly regulated aflatoxins. Further, numerous chemically-diverse mycotoxins may be present in the harvested grain prior to storage, thereby devaluing the grain and requiring the product to be blended, remediated, or destroyed. In 1987, the International Agency for Research on Cancer (IARC) classified aflatoxin B1 (AfB1) as a probable human carcinogen and maintains that status to date. Surprisingly, only two registered fumigants are available to combat insect pests in stored grain products: methyl bromide (CH3Br) and phosphine (PH3). The environmental impact and health risks associated with the use of these fumigants have focused national attention on our food safety practices. In 2000, the EPA reported a case that involved a methyl bromide leak that killed a 32 year old mother and sickened a child. The US government has mandated that methyl bromide will be completely eliminated from use by the year 2005 with partial reduction starting in 1999.1 This leaves phosphine as the only licensed fumigant to protect stored food grain from a multitude of insects, thus dramatically increasing the risk of insect resistance. Some stored-product insects already exhibit some levels of phosphine resistance.1, , In addition to this compounding problem, toxic phosphine residues create another health risk to the consumer. Banks et al have discovered that a significant portion of fumigated grain had phosphine levels higher than the Maximum Residue Limit (MRL) of 0.1 ppm, even after three transfers and 6 weeks post-fumigation. As the line of defense against food storage contaminants rapidly narrows, food safety personnel are searching frantically for alternative, safe treatment measures. Several non-residual control methods are currently being explored, however, each is not without drawbacks. For instance, Controlled Atmosphere (CA) technologies can be costly and induce a significant financial blow on an already economic stricken industry. As long as phosphine is cheaply available without regulatory limitations on its use, CAs will continue to play a background role. Despite the use of CAs for insect mitigation, no uniform method has been developed that will also eliminate other microbial and chemical contaminants in stored grain product. The ideal broad spectrum treatment process would be low cost, non-toxic, non-residual, and highly effective against a broad range of contaminants without the need for major renovations or altering the nutritional value of the commodity. Lynntech, Inc. proposes to develop a universal protective processing step to fulfill these needs. The proposed treatment method will incorporate the use of electrochemically-generated ozone (O3) gas as the fumigating agent.
More information
NON-TECHNICAL SUMMARY: The impact of acute and chronic disease via exposure to pathogens and chemical contaminants in food as well as financial losses incurred from such contaminants is significant. In an effort to increase the safety of foods, many intervention strategies have been developed, though none have been successful for uniform reduction of diverse food-derived chemical and biological contaminants in foods. Ozone (O3) has been shown to be a safe and effective decontaminating agent in many post-harvest and food processing applications and has grown in popularity due to the lack of chemical persistence, the broad susceptibility of organisms, and the ability to synthesize the disinfectant on-demand. Despite the promising economic and decontamination capabilities of ozone as a food decontaminant, the generation and uniform delivery of O3 gas throughout grains and oilseeds remains a challenge. The uniform decontamination process described here in offers unparalleled advantages over existing post-harvest treatment methods currently available. The Phase I research effort will prove that this process is capable of rapidly reducing significant populations of a wide range of naturally-occurring, stored food contaminants while focusing on user safety, food quality, and system flexibility. With the decontaminating agent generated on-site/on-demand, this treatment process can be easily transferred to rural agricultural settings for extended periods of time. The combined features and benefits of this process will attract potential corporate alliances for further development and optimization.

APPROACH:
TASK 1. Design and Development of a Flexible Laboratory Test System. A laboratory test system consisting of a multistage fluidized-bed reactor for batch-mode treatment grain. Fluidization is accomplished by injection of electrochemically-generated ozone in combination with air or an optional make-up gas. It has also been designed to facilitate the ease of scale-up of the system. The gas mixture will be fed to the fluidized-bed through a metered manifold. The grains will be fed to the top of the reactor from a hopper and the gas directed to the bottom of the reactor. The grain flow will follow a multi-stage pattern downward through the reactor. Each stage of the multistage fluidized-bed contains a support structure on which a fine mesh is placed. It ensures that the residence time for all the particles in the foodstuff are approximately the same. In addition, fluidization of the particles will ensure that the entire surface area of each individual grain particle is being treated. The gas exiting the fluidized-bed reactor will be passed through a destruct system to ensure that any excess ozone present in the system is converted to oxygen. The treated grains coming out of the fluidized-bed will be collected in a hopper. The process conditions in the fluidized system such as temperature, pressure drop, gas flow rate, feed-rate, number of stages in the fluidized-bed will be monitored and controlled with the help of a Lynntech Industries I/O box and personal computer.

TASK 2. Fabrication of the Flexible Laboratory Test System. The design will be critically evaluated for its manufacturability, assembly, and cost. Any modifications made to the designs at this stage will not in any way affect the functionality of the device, but will help in reducing the cost and weight of the device which we anticipate will be one of the critical factors in market penetration.

TASK 3. Mechanical and Functional Performance Testing. A Failure Mode and Effect Analysis (FMEA) will be performed. This will determine the reliability of each individual subsystem component and the overall system. The FMEA will help us determine the effect of individual component failure on the overall performance of the device and the reliability of the various components and subsystems. Statistical analysis tools will be used to ascertain the life of the critical components of the systems (which are determined from the failure mode and effect analysis).

TASK 4. Challenge Testing with Multiple Foodborne Contaminants. In order to establish the broad decontamination activity of the proposed process, tests will be conducted with clinically significant toxins, vegetative bacteria, bacterial spores, fungi, and insects that have been prevalent or pose a potential threat in stored food commodities. Corn naturally contaminated with aflatoxin B1 will be obtained from a local grain elevator and utilized for the detoxification experiments. Clean wheat and yellow field corn will be used for the remaining experiments as seeded carriers and a background load. All contaminants will be individually tested in accordance with the variable parametric settings of the GEN I system discussed in Task 3.

PROGRESS: 2005/05 TO 2006/12
More than 400 million tons (15 billion bushels) of grain are stored every year in the United States. Insects and fungi create serious quality problems in stored grains, and annual storage losses are estimated at more than $500 million. These infestations not only cause physical degradation of the food; they also create ideal conditions for the post-harvest production and accumulation of mycotoxins, specifically the highly regulated aflatoxins. Further, numerous chemically-diverse mycotoxins may be present in the harvested grain prior to storage, thereby devaluing the grain and requiring the product to be blended, remediated, or destroyed. Some stored-product insects already exhibit some levels of phosphine resistance. In addition to this compounding problem, toxic phosphine residues create another health risk to the consumer and do not decontaminate mycotoxins, bacteria, or molds. An ideal broad spectrum treatment process would be low cost, non-toxic, non-residual, and highly effective against a broad range of contaminants without the need for major renovations or altering the nutritional value of the commodity. In Phase I, Lynntech, Inc. developed a universal protective lab-scale processing protocol to fulfill these needs. The treatment method incorporated the use of electrochemically-generated ozone (O3) gas as the fumigating agent. The benefits of ozone in food safety have not gone unnoticed. Since its approval as a direct food additive for the treatment, storage, and processing of food in 2001, ozone has created a great deal of interest among academic researchers and food processors. The key challenges to the proper utilization of ozone gas are due to the physical and chemical characteristics of ozone gas: 1.Ozone is a highly reactive gas with a very short half-life in air (24 hours); 2.Ozone (O3) readily decomposes into oxygen (O2) which is accelerated by heat because the gas is temperature sensitive; 3.For corona discharge systems that do not use (liquid or) gaseous oxygen as a feed gas, concentrations of ozone are very low - typically less than 2 wt%; 4.Its high reactivity means that in most engineered treatment systems - for water, solids, or air - the gas is quickly consumed by or catalytically destroyed by all molecules within the treatment matrix. The consumption of ozone by non-target molecules in any food or feed treatment system (i.e., grain pericarp, "fines", soil/clay particles, metal oxides/rust) are always in competition with the targets of the decontamination process (bacteria, insects and larvae, fungal spores and mycelia and their associated mycotoxins). Therefore, uniform delivery of gaseous ozone to food remains an engineering obstacle for development of proper ozone-based commodity treatment hardware. In Phase I, we have successfully advanced the development of a critical engineering design scenario by using aflatoxin destruction as the benchmark of successful ozone treatment in corn. Aflatoxin represents a "worst case scenario" because it is the toughest, most challenging contaminants to address, when compared to bacteria and insects.

IMPACT: 2005/05 TO 2006/12
This Phase I innovation provides stored crop protection by reducing the impact of plant pathogens, human pathogens, insect pests, storage molds, and harmful toxins by developing proven, efficient and environmentally safe pesticide alternative. By developing a dynamic ozone treatment test system, the Phase I project provided key insight into a pilot scale engineering design that would add value to post-harvest handling quality preservation of staple crops (corn, wheat, soy, canola, cottonseed) and potentially for specialty crops (amaranth, meadowfoam, nutraceutical herbs, spices). Importantly, the innovation provides an environmentally friendly alternative to other chemically persistent fumigants, in that ozone is easily broken down into harmless oxygen. By proving the comprehensive decontamination capability of ozone, the technical approach can be used as both a preventative fumigant for pre-storage treatment and as a remediation tool for chemically and/or biologically contaminated grains and oilseeds.

Funding Source
Nat'l. Inst. of Food and Agriculture
Project source
View this project
Project number
TEXK-2005-00233
Accession number
202940
Categories
Natural Toxins
Bacterial Pathogens
Chemical Contaminants
Mycotoxins