Submitted to: Biocontrol Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/11/2016
Publication Date: 3/16/2016
Citation: Olanya, O.M., Sites, J.E., Hoshide, A.K. 2016. Cost modeling of pseudomonoas fluorescens and pseudomonoas chlororphis biocontrol for competitive exclusion of salmonella enterica on tomatoes. Biocontrol Science and Technology. 26:651-664.
Interpretive Summary: Theoretical understanding of biocontrol processes such as competitive exclusion microbes (CEM) against foodborne pathogens may provide useful insights on specific costs associated with post-harvest interventions and enhance planning decisions on alternative technologies. Biocontrol approaches may reduce contamination of foodborne pathogens on produce at postharvest based on competition for nutrients and space (competitive exclusion) with pathogenic bacteria, or due to the presence of antimicrobial compounds. Although cost estimates for pulsed electric field (PEF) or thermal pasteurization of food products and other similar technologies have been documented, there is limited published data on cost estimates for CEM applications for pathogen control. We estimated the application rates of CEM for biocontrol of Salmonella enterica on tomatoes. Due to the variation in application rates of up to 30 percentage, the unit costs of CEM biocontrol product may range from US$ 0.05-$0.95 per kg of tomato for the small-scale and from US$ 0.0041-$0.0075 per kg for the large CEM production models. The total variable costs for CEM were 95% of total production costs, while fixed costs were only 5% of total costs. This indicates that there is limited capital investment in producing CEM at small scale. Overall, the estimated total annual costs of applying CEM technology for control of Salmonella enterica on tomatoes (US$ 0.0058 to 0.073 per kg) is greater than competing technologies such as chlorine wash (sodium hypochlorite) which averaged US$ 0.00046 per kg or gaseous chlorine dioxide with computed values of US$ 0.02 to US$ 0.21 per kg. For high value produce, CEM may complement existing technologies if efficacy and delivery systems can be optimized and its effects on gut miccroflora and associated factors are evaluated.
Technical Abstract: Biocontrol measures may enhance postharvest interventions, however; published research on process-based models for biocontrol of foodborne pathogens on produce is limited. The aim of this research was to develop cost model estimates for competitive exclusion process using Pseudomonas fluorescens and P. chlororaphis (non-plant pathogenic and non-human pathogen) as biocontrol microbes against S. enterica on tomatoes. Cost estimates were based on material inputs, equipment, facilities, and projected processing conditions similar to that of postharvest packaging of tomatoes or vegetables. The microbiological data for inactivation of S. enterica was based on published data and biocontrol bacteria were grown on Trypticase soy broth (TSB) in a processing unit (self contained growth chamber). The small scale processing facility was assumed to have a processing capacity of 2,000 kg of tomatoes per hour for 16 h per day and operational 6 days a week and for a 3-month period per year while the large scale facility was assumed to have a processing capacity of 100,000 kg of tomatoes per hour for the same operational period. The estimated initial capital investment costs for both a small-scale and large-scale models (production facility) were US$ 391,000 and US$ 2.1 million. Total annual costs (operational plus ownership) of US$ 162,000 and US$ 2 million were estimated for small and large-scale models, respectively. The total annual cost for application of a competitive exclusion process for biocontrol of S. enterica on tomato was estimated at US$ 0.0058 to 0.073 per kg of tomato during commercial processing operations. This exceeds technologies such as chlorine wash (sodium hypochlorite) estimated at US$ 0.00046 per kg and gaseous chlorine dioxide at approximately ranged from US$ 0.02-0.21 per kg. For high value produce, CEM may complement existing technologies if efficacy and delivery systems can be optimized and key questions on CEM effects on gut microflora and associated factors are thoroughly evaluated. CEM may increase food safety, reduce storage loses, and extend shelf-life of produce.