Microencapsulation of Peumus boldus oil by complex coacervation to provide peanut seeds protection against fungal pathogens

GIRARDI, NATALIA S.; GARCÍA, DAIANA; PASSONE, MARíA A.; NESCI, ANDREA; ETCHEVERRY, MIRIAM

Barcelona

Congreso; VI International Conference of Environmental, Industrial and Applied Microbiology ? BioMicro World 2015; 2015

Boldoessential oil (EO) (Peumus boldusMol.) has proven to be effective in controlling peanut storage fungi [1].However, fast decreases of boldo residues were observed after the oil wasapplied on the grain surfaces [2]. Inthis study, boldo EO microcapsules were prepared using the complex coacervationtechnique with gelatin/gum arabic, in order to enhance the dwellperiod of this preservative in the storage system.Theeffect of gelatin bloom (220 and 240) and the crosslinking conditions:  type of crosslinking agent (withoutcrosslinking agent (WCA), formaldehyde (F) and glutaraldehyde (G)) andcrosslinking time (0, 10, 60 and 120 min), on the size and encapsulationefficiency (EE%) of the microcapsules were studied. The release of boldo EOfrom the microcapsules that showed the higher EE% was evaluated at differenttemperatures (4 and 25 °C) and on peanut grains conditioned at three wateractivities (0.65, 0.85 and 0.95 aW). Boldo EO formulation, was appliedin a dose of 3000 ppm on peanut kernels intended for seeds -medium and low PG, with and without seed treatment methyl thiophanate 10% + metalaxyl 1.33% + micronutrients[Co and Mo]-), which were stored at roomtemperature (20-25 °C) for 114 days. BoldoEO microcapsules showed a mean diameter of 7.61 ìm and the EE% ranged between 67 and 97%. Moreover, microencapsulated EOshowed very low release rates (between 4 x 10-3 and 4 x 10-5%) after 10 days of storage. When boldo EO formulation was applied on peanutkernels, significant fungal count reductions were observed, especially when theapplication was made after seed treatment (69.5%). Microencapsulated boldo EOalso exerted an adverse effect on the ability of seed germination, withreductions of PG estimated between 88 and 95%.In conclusion, the complex coacervation techniqueallowed encapsulating boldo EO with high efficiency percentages, without affectthe antifungal capacity. The treatment with boldo EO microcapsules after theapplication of seed fungicide treatments could increase the seed protectionagainst fungal pathogens during a storage period of 114 days. To avoid theeffect on seed PG, the application of boldo EO formulation on unshelled stored peanutbefore fungicide treatment will be evaluated in future studies.