Application of microencapsulated essential oil extracted from Thymus schimperi for its antibacterial and antioxidant activity on minced meat

Abstract

This study investigated the antibacterial and antioxidant properties of Thymus schimperi essential oil (EO) microencapsulated using spray-drying (SD) and freeze-drying (FD) methods. The effectiveness of these encapsulated EOs was compared to sodium nitrite and an untreated meat sample, serving as a negative control, over a 15-day refrigerated storage period (4 °C). In vitro antioxidant activity, evaluated using DPPH, ABTS, and FRAP assays, revealed higher values for SD-encapsulated T. schimperi EO compared to FD-encapsulated EO. DPPH radical scavenging activity for SD-encapsulated EO ranged from 4.6 to 45.15%, while FD-encapsulated EO exhibited activity from 2.73 to 39.81%. ABTS radical scavenging activity for SD-encapsulated EO ranged from 10.45 to 35.12%, and for FD-encapsulated EO from 7.24 to 29.82%. FRAP values were 0.68 mg TE/g for SD-encapsulated EO and 0.73 mg TE/g for FD-encapsulated EO. Antibacterial activity, determined by minimum inhibitory concentration (MIC), indicated that SD-encapsulated T. schimperi EO demonstrated greater efficacy against Escherichia coli and Salmonella typhimurium (MIC: 4 mg/mL) and Staphylococcus aureus and Streptococcus epidermidis (MIC: 8 mg/mL), compared to FD-encapsulated EO (E. coli and Salmonella typhimurium: 8 mg/mL; Staphylococcus aureus: 16 mg/mL; Streptococcus epidermidis: 8 mg/mL). In situ antibacterial activity during refrigerated storage demonstrated the following order of efficacy: sodium nitrite > free T. schimperi EO > SD-encapsulated EO > FD-encapsulated EO > untreated control. These findings suggest that SD-encapsulated T. schimperi EO possesses better antibacterial and antioxidant properties compared to FD-encapsulated EO, indicating its potential as a promising natural preservative for meat products.