Gaseous Ozone as a Potentially Sustainable Approach for Surface Microbial Control in Semi-Hard Cheese

The increasing demand for food products and the implementation of sustainable development principles have encouraged the search for technological solutions that can reduce food losses and the environmental burden of food processing. Milk and dairy products are nutrient-rich matrices, but they also provide favourable conditions for microbial growth. Therefore, ensuring microbial safety during cheese production, ripening, and storage is essential. This study aimed to evaluate the potential application of gaseous ozone as a low-residue and potentially more sustainable approach for controlling surface microbial contamination in semi-hard cheese during ripening or storage. Ozone is characterized by low cost, strong oxidative properties, antimicrobial activity, and rapid decomposition into oxygen without leaving persistent chemical residues. Semi-hard cheese samples were treated with gaseous ozone at a concentration of 4.84 ± 0.22 parts per million (ppm) for 10, 30, 60, 90, and 150 min. After treatment, the counts of aerobic microorganisms, yeasts, and moulds were determined, and changes in moisture, fat, and protein content were assessed. After only 10 min of ozonation, aerobic microorganism counts decreased from 2826 ± 1911 × 104 to 275 ± 184 × 104 colony-forming units per gram (CFU/g). In contrast, a reduction in yeast counts was observed only after a longer treatment duration of 60 min. No clear treatment-dependent changes were detected in mould counts or in total fat and protein contents. Cheese moisture content decreased significantly after 10 min of ozonation and continued to decline as the ozonation duration increased. The results suggest that gaseous ozone may be used as an additional microbial control approach for semi-hard cheese during ripening or storage. However, the findings only partially confirmed a significant effect of gaseous ozone on surface microorganisms and its neutrality with respect to product proximate composition.