Evaluation of lethality temperature and use of different wall materials in the microencapsulation process of Trichoderma asperellum conidias by spray drying

Abstract

The microencapsulation process of Trichoderma spp. by spray drying (SD) aims at the protection and suitability of these to the use in agriculture as controllers of phytopathogens. The objective of this study was to evaluate the lethality temperature of Trichoderma asperellum conidia by spray drying, studying the use of sucrose (SU), maltodextrin DE20 (MD20), gum arabic (GA), whey powder (WH) and lactose (LA) as wall materials (WM) in the microencapsulation process. The lethality curves of Trichoderma asperellum conidia dry in SD without wall material were analyzed between the drying temperatures of 60 to 120 °C. The microcapsules with the various wall materials were dried at 80, 90 and 100 °C. The five different wall materials were characterized for their moisture, water activity, hygroscopicity, water solubility and viscosity in suspension. The microcapsules produced were evaluated for moisture, water activity, conidial viability (CV), survival percentage (SP) and scanning electron microscopy (SEM). The highest percentages of conidial lethality were observed at drying temperatures above 90 °C, both for the tests with and without the wall materials. Among the wall materials studied, the highest percentage of conidia survival with 90 °C drying air temperature was maltodextrin DE20 (92.89 ± 1.47%), followed by whey (82.84 ± 2.35%), sucrose (82.55 ± 2.01%), gum arabic (81.59 ± 0.37%) and lactose (44.73 ± 0.40%). After obtaining the results it was verified that the MD20 presented high potential for the microencapsulation process, thus, the lethality curves of the conidia microencapsulated with MD20 were made by varying the inlet air temperature from 60 to 120 °C. The data obtained showed that even with the addition of wall material, when air inlet temperatures above 90 °C were used, it was not possible to maintain the cell viability of the conidia.