Project : USDA ARS

ARS Home » Northeast Area » Wyndmoor, Pennsylvania » Eastern Regional Research Center » Microbial and Chemical Food Safety » Research » Research Project #440207

Research Project: Integration and Validation of Alternative and Multiple Intervention Technologies to Enhance Microbial Safety, Quality, and Shelf-life of Food

Location: Microbial and Chemical Food Safety

2022 Annual Report

Objectives
Objective 1: Utilize novel biological, chemical, and physical technologies to inactivate microbial contamination in and on various food products, which can include and is not limited to produce, nuts, meats and ready-to-eat foods. Directly utilize the hurdle concept to develop processing methods which have a direct application to the need of the industry. Optimize the processes to allow scale-up to commercial treatment levels, appreciating the complexity of the interventions in terms of the food to be treated, the processing conditions, the equipment necessary, and the sensory and nutritional qualities of the food types treated. Sub-objective 1. Investigate surface characteristics of food and bacteria, bacterial attachment, biofilm formation, and pathogen inactivation mechanisms for potential effective chemical and physical interventions. Sub-objective 2. Develop and optimize biological, chemical, physical and packaging decontamination interventions that do not affect food quality, making use of pathogen microbial ecology information generated under sub-objective 1 Sub-objective 3. Establish protocols for combination treatments and develop hurdle interventions to achieve additive or synergistic effects on pathogen reduction by combining biological, chemical and physical interventions developed in sub-objective 2, while maintaining or improving the quality and shelf-life of foods. Sub-objective 4. Conduct scaled-up studies of effective single or hurdle interventions demonstrated in sub-objectives 2 and 3, to facilitate commercialization of the technologies.

Approach
This project will progress in four phases: elucidate pathogen ecology and inactivation mechanisms; evaluate single interventions; apply a combination of interventions; and conduct pilot scale studies (Fig. 1). Initially, we will investigate bacterial attachment, biofilm formation, and bacterial inactivation mechanisms as affected by potential interventions. This knowledge will aid us in choosing and optimizing biological, chemical, packaging and physical control strategies. Selection of intervention technologies will also be based on earlier research conducted by our own group and by others. The optimized interventions will be strategically integrated to achieve additive and synergistic effects on pathogen reduction. The effects of these processing technologies on product quality attributes will be evaluated using instruments to measure quality aspects in conjunction with sensory panels. Both individual and combination intervention technologies capable of achieving the desired performance standards for pathogen reduction, quality and shelf life will be optimized and validated in scaled up studies in our unique BSL-2 pilot plant for large-scale trials where large volumes of foods can be treated. The types of foods evaluated in the project will be those frequently involved in outbreaks of foodborne illnesses or associated with emerging pathogens, fresh produce items that are hard to sanitize due to surface characteristics, and foods that cannot be subjected to traditional wash treatments. To facilitate commercialization of effective interventions, collaborations with the food industry will be established by actively fostering interactions with stakeholders. Stakeholders will be updated via direct interactions, site visits, annual scientific meetings and trade shows regarding research goals and objectives of the project, and inputs will be solicited to identify key problems to be solved so that the technologies will be more relevant and applicable. Although much of the effort will be on hurdle technologies that combine various individual interventions, effective individual treatments along with integrated ones will be tested in pilot scale studies. In addition, even though the project will be conducted in a progressive 4-stage process, the flow or order of research accomplishments will not be strictly chronological as there will be opportunities for technologies to be implemented by the industry at every stage of the project via establishment of research and development agreements and technology transfer.

Progress Report
Progress has been made on Objectives 1 and 2, which falls under National Program 108, Component I, Foodborne Contaminants, and National Action Plan Problem Statement 5, Intervention and Control Strategies. A detailed description of progress is as follows. There is an increasing demand for novel, environmentally friendly antimicrobials from renewable resources produced by clean and sustainable technologies. Experiments were conducted to evaluate antimicrobial properties of various phenolic fatty acids derived from vegetable oils, fatty acids, amino acids, and natural phenolic compounds. Minimum inhibitory and minimum bactericidal concentrations were measured using the microdilution method against Gram-positive and Gram-negative bacteria. In addition, the compounds were applied on apple surfaces for their efficacy against Gram-positive bacteria. Furthermore, selected biobased compounds were photosensitized by ultraviolet light A (UV-A) light for synergistic inactivation of bacteria. A new type of chitosan coating and film with organic acids and hydrogen peroxide were developed and evaluated. The film was able to reduce up to 99.9999% of Escherichia coli (E. coli) in peptone water after 48 hours of exposure, while the coating inhibited the growth of spoilage microflora on vacuum-packaged fresh carrots stored at 10 C. The combination of washing, coating and antimicrobial packaging film for inactivating E. coli and spoilage microflora on fresh produce is being investigated. To determine bacterial survival, cell recovery on produce and produce wash-water was quantified at two storage temperatures (5 C and 25 C) to document the attachment of bacteria on fresh produce. Cells with loose attachment were washed-off with water or produce rinses, while cells with greater attachment adhered to the produce. Recovery of Salmonella on produce and in wash-water varied. On alfalfa sprouts and in wash-water, no Salmonella was recovered at either temperature. While Salmonella (37%) was recovered on carrots at 5 C storage, no pathogen was detected from carrot wash-water. At 25 C, pathogen recovery on carrots and from produce wash-water was similar, indicating less attachment on carrots at higher temperature. These results imply potential for pathogen attachment on produce at the above-mentioned conditions. There are limited data on the extent to which aerobic microbiota populations on produce surfaces may enhance or retard pathogen attachment. Investigations are underway to determine if bacterial attachment on produce surfaces may be predisposed by the existence of aerobic populations and other microbiota relative to produce samples devoid of native microflora by treatments with disinfectants. Understanding the inactivation mechanisms of various intervention technologies are vital to develop effective means of minimizing the risk of human pathogen contamination, and most importantly to rationally design hurdle strategies. In collaboration with other ARS scientists, studies are being conducted on combining antimicrobial sanitizers developed by our group with other non-thermal intervention technologies, such as cold plasma and UV-light, and minimal thermal treatments.

Accomplishments
1. High humidity is critical for gaseous ozone treatments to preserve quality and enhance antimicrobial efficacy. Outbreaks of foodborne illnesses and recalls associated with fresh produce continue to occur in recent years. Effective intervention technologies to inactivate foodborne pathogen are needed. ARS scientists at Wyndmoor, Pennsylvania, evaluated the impact of relative humidity on the efficacy of ozone against Salmonella and on changes in quality of tomatoes during storage. Results demonstrated that increasing humidity during ozone treatment not only increased the efficacy of ozone against Salmonella by 99.9% on tomatoes, but also minimized the ozone-induced deterioration in sensory and nutritional quality of the fruit. This information is of value for the produce industry to implement the FDA-approved technology to preserve the quality of fresh produce, while enhancing microbial safety.

2. Strength of bacterial attachment on produce surfaces affects decontamination. Understanding the strength of bacterial attachment and survival on produce surfaces is important in developing non-thermal processing interventions to enhance food safety. Researchers at Wyndmoor, Pennsylvania, determined the strength of Salmonella attachment on apple and tomato surfaces after washing treatments. Irrespective of attachment strength, a multi-organic acids solution developed by the researchers was up to 90% more effective than chlorine (a commonly used sanitizer) in reducing attached populations of Salmonella and aerobic mesophilic bacteria on contaminated apples and tomatoes. Therefore, the novel organic acid sanitizer solution will be a welcome addition to the arsenal of sanitizers for the produce industry to combat pathogen contamination.

3. Edible coating enhances microbial safety and extends shelf life of tomatoes. Multiple outbreaks and recalls associated with fresh tomatoes have been reported. Hence, it is necessary to apply antimicrobial treatments on tomatoes. ARS scientists at Wyndmoor, Pennsylvania, investigated the antimicrobial efficacy of chitosan coating combined with organic acids and an essential oil against foodborne pathogens on tomatoes. Coating treatments reduced over 99.9% Salmonella and Listeria monocytogenes populations, as well as spoilage bacteria, molds and yeasts. There was no significant difference in texture and color among all tomato samples during 21-day storage at 10 C. This study suggests that chitosan-acid coating is suitable for extending the shelf-life and enhancing the safety of tomatoes.

4. Reduction of Salmonella on produce by low-dose gamma ray radiation. Postharvest interventions to mitigate Salmonella contamination on produce is crucial for food safety. Researchers at Wyndmoor, Pennsylvania, determined the survival of Salmonella on carrots and tomatoes following low-dose gamma ray radiation treatments (0-1 kilogray). Salmonella populations were reduced by at least 99.99% on both carrots and tomatoes after irradiation treatments at 5 C and 25 C. This under-utilized technology can be used to enhance the safety of postharvest carrots and tomatoes, if applied appropriately.

U.S. DEPARTMENT OF AGRICULTURE

Microbial and Chemical Food Safety: Wyndmoor, PA