Chitosan Nanoencapsulation of Zenian (Carum copticum) Essential Oil for the Control of Kluyveromyces marxianus Spoilage in Doogh

This study explores the efficacy of chitosan nanoencapsulation of Zenian (Carum copticum) essential oil (ZEO) in controlling Kluyveromyces marxianus spoilage in Doogh, a traditional Iranian fermented milk beverage. K. marxianus, a prevalent yeast in dairy products, compromises Doogh’s shelf life by producing off-flavors, gas, and bloating. Addressing limitations of ZEO’s poor water solubility and degradation, chitosan-Zenian nanoemulsions (CZN) were synthesized via ionic gelation, incorporating ZEO at ratios of 1:0, 1:0.25, 1:0.5, and 1:1 (ZEO: chitosan). Physicochemical characterization revealed high encapsulation efficiencies (76–81%), with particle sizes increasing from 29.2 nm (1:0) to 339.2 nm (1:1), and zeta potential shifting from -18.8 mV to +20.3 mV, optimizing stability at 1:0.5. SEM and FTIR analyses confirmed ZEO integration and morphological changes with increased ZEO loading. Antimicrobial assays demonstrated significant inhibition, with the 1:0.5 ratio yielding the largest inhibition zone (52.70 mm) and reducing K. marxianus in Doogh to 3.8 log CFU/mL by day 14, compared to 7.142 log CFU/mL in controls. Sensory evaluation indicated an initial preference for lower ZEO ratios (1:0.25), while higher ratios (1:0.5, 1:1) better preserved taste and odor over 14 days (p<0.02). Microbiological tests confirmed Doogh''s safety, with no detectable pathogens. These findings highlight CZN, particularly at the 1:0.5 ratio, as a potent, natural preservative, balancing antimicrobial efficacy, stability, and sensory acceptability. This approach offers a scalable solution for extending Doogh''s shelf life, aligning with consumer demand for clean-label dairy products.