Evaluation of food additives as alternative or complementary chemicals to conventional fungicides for the control of major postharvest diseases of stone fruit for the control of major postharvest diseases of stone fruit

Authors: PALOU, LLUIS - IVIA, VALENCIA SPAIN; Smilanick, Joseph; CRISOSTO, CARLOS - UC DAVIS

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/19/2008
Publication Date: 4/1/2009
Citation: Palou, L., Smilanick, J.L., Crisosto, C. 2009. Evaluation of food additives as alternative or complementary chemicals to conventional fungicides for the control of major postharvest diseases of stone fruit for the control of major postharvest diseases of stone fruit. Journal of Food Protection. 72(5):1037-1046.

Interpretive Summary: Unless actions are taken to minimize decay losses, a high proportion of peaches rot after harvest because they are attacked by decay fungi. The method employed to minimize these losses is to apply fungicides to the fruit both before and after harvest. Some commercial buyers and consumers are concerned about this practice, because of the presence of fungicide residues on the fruit. Furthermore, repeated use of the fungicides can lead to the development of fungicide resistant populations of the decay fungi. In this work, a variety of common food preservatives, such as potassium benzoate that is used in soft drinks, and salts, such as sodium bicarbonate or baking soda, were evaluated to control the decay fungi. This work showed that some have modest performance in this role, although some injured the fruit, and that hot water treatments of the fruit alone were about as effective as these compounds.

Technical Abstract: Among more than twenty food additives and GRAS (generally regarded as safe) compounds that were tested at three concentrations in in vivo primary screenings with several cultivars of California peaches, nectarines, and plums that had been artificially inoculated with seven major postharvest pathogens (Monilinia fructicola, Botrytis cinerea, Geotrichum candidum, Alternaria alternata, Penicillium expansum, Mucor piriformis, and Rhizopus stolonifer), 200 mM potassium sorbate, sodium benzoate, and sodium sorbate, 100 mM 2-deoxy-D-glucose, 400 mM sodium carbonate, and 250 mM potassium carbonate had the best overall performance as possible alternatives to conventional fungicides to control decay. Sodium and ammonium molybdates, acid lactic, and hydrogen peroxide were somewhat effective but phytotoxic to fruit skin tissues. The selected compounds, however, lacked sufficient effectiveness and persistence when tested against brown rot in small-scale trials as 60 s dips in aqueous solutions at ambient temperatures. Rinsing treated fruit with tap water slightly reduced the efficacy of the compounds. In contrast, heating the solutions to 55 or 60ºC significantly increased treatment efficacy, but the effectiveness of the solutions was not superior to water alone at these temperatures. In semicommercial trials, mixtures of fludioxonil with potassium sorbate, sodium benzoate, or 2-deoxy-D-glucose applied as fruit coatings on a packingline were not synergistic in effectiveness to control brown rot, gray mold, and sour rot. Although effective in vitro, commercial use of these compounds is not promising with the methods of application we evaluated.