Cinnamon Essential Oil and Nanoemulsions for Inhibiting Pseudomonas paracarnis and Pigment Production in Fresh Cheese

Abstract

Pseudomonas spp. is one of the main spoilage bacteria in dairy products, particularly fresh cheese, leading to significant economic losses and food waste. This study evaluated cinnamon essential oil (CEO) and its nanoemulsions as sustainable strategies to inhibit Pseudomonas paracarnis A006, both in vitro and in a fresh cheese-mimicking matrix. CEO exhibited the highest antibacterial activity among the 20 screened essential oil (EO), with a minimum inhibitory concentration (MIC) and a minimum bactericidal concentration of 0.625 µL/mL. Gas chromatography–mass spectrometry identified cinnamaldehyde as the main active component (82.55%). Cinnamaldehyde, when tested at the same proportion found in CEO (82.55%), exhibited an equivalent MIC and antimicrobial efficacy both in vitro and in model cheeses, underscoring its role as the primary contributor to CEO’s activity. Nanoemulsions were optimized by using response surface methodology, achieving a droplet size of 164.33 nm with 4.26 min of sonication and 2.79% soy lecithin. In situ, treatments with cinnamaldehyde, free CEO, and nanoemulsions at 4 × MIC reduced Pseudomonas counts by 2.24, 1.55, and 1.46 log colony-forming units/g, respectively, after 7 days of storage. However, nanoemulsion efficacy was compromised by interactions with the cheese matrix, leading to reduced cinnamaldehyde release and the development of blue spots. These results highlight CEO as a promising natural preservative, while nanoemulsion formulations require further optimization to improve their applicability in complex food systems.