Encapsulation of Holy Basil Essential Oil in Gelatin: Effects of Palmitic Acid in Carboxymethyl Cellulose Emulsion Coating on Antioxidant and Antimicrobial Activities

The challenge of using essential oils possessing antioxidant and antimicrobial properties in food industry is to maintain their chemical stability. This research examined the roles of emulsion coating in preventing the degradation of holy basil essential oils (HBEO) during storage. The uncoated HBEO-loaded gelatin microcapsules and those coated with 1, 2, and 3 % palmitic acid emulsified in carboxymethyl cellulose, denoted as UC, C-1P, C-2P, and C-3P, respectively, had HBEO contents of 76.35, 76.09, 68.96, and 59.39 % with the surface oils of 1.31, 0.65, 0.65, and 0.84 %, respectively. The increase in the palmitic acid concentrations caused a significant increase in the L ^* values (p?<?0.05). After 90 days of storage at 30 °C, the surface oils of UC, C-1P, C-2P, and C-3P significantly increased to 3.65, 2.43, 2.15, and 3.03 %, respectively, coincident with the decrease in the L ^* values. X-ray diffraction studies revealed that the crystalline structures of the microcapsules were influenced by gelatin renaturation and palmitic acid polymorphism. The antioxidant activities, expressed as IC₅₀, of the free and encapsulated HBEO before storage were 0.30 mg/ml. After storage, IC₅₀ of only C-2P remained constant, while those of the rest significantly increased (p?<?0.05). The minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of all the samples against pathogenic bacteria did not change over storage. C-3P exhibited the strongest antimicrobial activity of MIC of 0.625 mg/ml and MBC of 1.25 mg/ml. These findings suggest that the emulsion coating enables shelf life extension of HBEO-loaded gelatin microcapsules.