Enhancement of forced-air cooling to reduce Listeria monocytogenes, Salmonella and/or total surface microbiota on cantaloupes.

During the cooling process, there is a unique opportunity of antimicrobial intervention to eliminate foodborne pathogens and/or spoilage organisms contaminating the surface of harvested cantaloupe. A cost-effective sanitizing process using a novel combination of ultrasonic atomization technology and antimicrobial formulation is proposed to integrate into commercial forced-air cooling systems. Different antimicrobial formulations and various operative conditions, including vaporizing rate, air-flow rate and treatment duration, will be investigated using our experimental systems to optimize the process and improve effectiveness against Listeria monocytogenes or salmonellae. Advantages of this process include: (1) Only minimal modification is required to current forced air-cooling methods by adding an ultrasonic device which is commercially available at low cost; and (2) Aerosolized antimicrobials absorb heat during evaporation and the new system can increase the cooling efficiency of an existing cooling system. To reduce operational cost, only Generally Recognized As Safe (GRAS) and commercial available antimicrobials with low cost will be tested. In addition, the impacts of this treatment on quality and shelf life of cantaloupes will be thoroughly investigated. A cost-effective intervention to reduce L. monocytogenes and Salmonella contamination would be quite valuable during the cooling process of harvested cantaloupes.

Cantaloupes have been associated with foodborne disease outbreaks in the US and are now considered to be a high risk commodity. During the forced air cooling of cantaloupes, there is an opportunity for antimicrobial intervention to reduce foodborne pathogens contaminating the surface of harvested cantaloupe. We propose to evaluate the efficacy of antimicrobial formulation using ultrasonic atomization technology in the forced-air cooling to reduce populations of Listeria monocytogenes, Salmonella and/or spoilage microbiota by at least 3 log/cm2 on the surfaces of inoculated cantaloupes. The antimicrobial formulations will be developed based on chlorine, selected plant essentials, organic acids, hydrogen peroxide and foodgrade surfactants to take advantages of any synergism of different antimicrobials to inactivate foodborne pathogens on the surface of cantaloupes. Different antimicrobial formulations and the various operative conditions, including temperature, concentration of sanitizer, air-flow rate and treatment duration, will also be investigated to optimize the process and achieve the desired cost-effectiveness with assistance from our industry collaborator. The antimicrobial formulations are vaporized by ultrasonication (to L. monocytogenes and Salmonella contamination would be quite valuable during the cooling process of harvested cantaloupes. All microbial experiments will be conducted with the outbreak related pathogenic microorganisms of interest (not surrogates) in a biosafety level-3 facility. The advantages of this process include: (1) Only minimal modifications are required to existing forced air-cooling methods by addition of an ultrasonic device which is commercially available at low cost; and (2) Aerosolized antimicrobials absorb heat during evaporation, so the new system can increase the cooling efficiency of an existing cooling system. The overall objective of our proposed research is to develop a cost-effective sanitizing process which can be integrated into commercial forced-air cooling systems. The novel combination of ultrasonic atomization technology and effective antimicrobial formulations should reduce L. monocytogenes, Salmonella and/or spoilage organisms during the cooling of cantaloupes without affecting final quality and sensory attributes.

1. To identify optimal treatment conditions to reduce L. monocytogenes, Salmonella and/or spoilage microbiota contamination of cantaloupes during the cooling step using an experimental system. 

2. To assess the effects of optimal treatment conditions on the reduction of natural spoilage microorganisms, as well as determine the degree of any changes to the quality and sensory properties of cantaloupes after cooling in our experimental system.

With a novel combination of ultrasonic atomization and antimicrobial formulation, our approaches could significantly reduce Salmonella or L. monocytogenes contaminating the surface of cantaloupes placed inside a Regular carton during their forced air cooling process.The aerosolized antimicrobials were able to pass through the opening holes of a carton to inactivate foodborne pathogens or spoilage organisms. Higher inactivation efficacy was generally observed on grape tomatoes when compared with findings on cantaloupes. The approaches had little or minimal risk of cross-contamination. This process can provide a unique opportunity for antimicrobial intervention to reduce foodborne pathogens and spoilage organisms contaminating the surface of harvested produce while maintaining its quality. More extensive and novel research are still needed to understand better the big variations of Salmonella or L. monocytogenes reductions in some treatments, and validate the treatment efficacy in a larger scale.