Czech J. Food Sci., 2026, 44(2):150-156 | DOI: 10.17221/129/2025-CJFS

Microwave-assisted extraction of annatto: Effects of pH and time on antibacterial activityOriginal Paper

Isti Handayani ORCID...1, Aisyah Tri Septiana ORCID...1, Budi Sustriawan ORCID...1, Karseno ORCID...1
1 Department of Agricultural Technology, Faculty of Agriculture, Jenderal Soedirman University, Purwokerto, Indonesia

Annatto seeds possess antimicrobial properties, but extraction methods may degrade bioactive compounds. This study investigated the impact of pH-adjusted microwave-assisted extraction using distilled water on antibacterial activity to obtain safe food-grade extracts. Extractions were performed at pH values of 4, 7, and 9 for extraction times of 2, 4, and 6 min, using a microwave power setting of 100 W. The antimicrobial activity of the extracts was assessed against Escherichia coli and Staphylococcus aureus through inhibition zone analysis and viable bacterial cell count reduction. In parallel, the total phenolic content of each extract was quantified to examine the correlations between phenolic concentration and antibacterial activity. The findings revealed that extraction at pH 4 for 2 min yielded the most pronounced antibacterial activity with a minimum inhibitory concentration (MIC) of 5%. The application of a 20% annatto extract resulted in the lowest viable cell counts of both E. coli and S. aureus. Variations in pH and extraction time did not result in significant differences in total phenolic content, suggesting that antimicrobial efficacy may be influenced not only by phenolic concentration but also by the specific profile of active compounds.

Keywords: Bixa orellana seeds; food-grade extract; phenolic compounds; Escherichia coli; Staphylococcus aureus

Received: August 6, 2025; Revised: February 10, 2026; Accepted: February 13, 2026; Prepublished online: April 27, 2026; Published: April 29, 2026  Show citation

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Handayani I, Septiana AT, Sustriawan B, Karseno. Microwave-assisted extraction of annatto: Effects of pH and time on antibacterial activity. Czech Journal of Food Sciences. 2026;44(2):150-156. doi: 10.17221/129/2025-CJFS.
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