Microencapsulation of Thymus vulgaris and Tagetes minuta essential oils: Volatile release behavior, antibacterial activity and effect on potato yield

Abstract

Thymus vulgaris and Tagetes minuta essential oils (EOs) are recognized due to their antibacterial activity against Streptomyces scabiei, the main causal agent of potato common scab disease. However, EOs have phytotoxic characteristics and are susceptible to degradation by environmental factors, which make their storage and application difficult. Microencapsulation technology represents an alternative for EOs handle, allowing their protection and gradual spread of their compounds. In the present work, microcapsules of maltodextrin and hydroxypropyl methylcellulose containing T. minuta and T. vulgaris EOs were evaluated, analyzing their features, their stability at storage conditions and the control release of their volatile compounds when they are applied on humid substrate. Additionally, the in vitro antibacterial activity of microencapsulated EOs against S. scabiei, and their effects on potato crop yield were evaluated. The obtained microcapsules presented good yield (48.28–51.01 %), low moisture (3.87–3.98 %), spherical shape, and variable size. The release rate of volatiles was high and constant over the 29 days of storage, for almost every compound detected from microcapsules containing T. vulgaris EO. Additionally, the microcapsules containing T. minuta EO showed a variable but high release rate of its main compound dihydrotagetone. The application of microcapsules on humid substrate resulted in a greater release of volatiles for 14 days. The application of T. vulgaris and T. minuta EOs on potato plants (var. Spunta) showed no effect on plant growth and photosynthetic activity, but reduced tuber yield (9.07 and 9.40 g tubers fresh weight/ plant, respectively). The microencapsulation of these EOs reduced this effect (10.14 and 10.29 g tubers fresh weight/plant, respectively), and maintained the bacteriostatic activity on S. scabiei, making them a promising tool for potato common scab control.