Effect of ozone on microbial, chemical and sensory attributes of shucked mussels

The effect of ozonation in aqueous solution (O3 concentration=1mg/l, time of ozonation: 60 and 90min) on the shelf-life of shucked, vacuum-packaged mussels, stored under refrigeration was studied by monitoring the microbiological, chemical and sensory changes occurring in mussel samples, for a period of 12 days. Non-ozonated vacuum-packaged mussels served as the control sample. Ozonation affected populations of bacteria namely, aerobic plate count (APC) (0.7–2.1log cycle reduction), Pseudomonas spp. (0.5–1.1log cycle reduction) and H2S-producing bacteria (1.1–2.5log cycle reduction), Brochothrix thermosphacta (0.3–1.4log cycle reduction), lactic acid bacteria (0.3–0.8log cycle reduction) and Enterobacteriaceae (0.5–1.5log cycle reduction). The effect of ozonation was more pronounced at the longer time of ozonation. Of the chemical indicators of spoilage monitored, trimethylamine values of all mussel samples remained relatively low throughout the entire storage period, attaining values of 7.5, 6.0 and 6.4mg N/100g for the control and ozonated for 60 and 90min samples, respectively, on day 12 of storage. Total volatile basic nitrogen (TVB-N) values similarly remained relatively low (⩽20mg N/100g) until day 6 of storage, and increased to 31.9, 24.2 and 26.9mg N/100g mussel meat for the control and ozonated for 60 and 90min samples, respectively, on day 12 of storage. Initial TBA values were surprisingly high (30–35mg MA/kg) and decreased to 23.0, 21.7 and 13.3mg MA/kg mussel meat on day 12 of storage for the control and the ozonated for 60 and 90min samples, respectively. Sensory evaluation (odor, taste and texture) of cooked mussels showed a good correlation with bacterial populations. On the basis of sensory analyses, a shelf-life of 12 days was obtained for vacuum-packaged mussels ozonated for 90min as compared to a shelf-life of 9 days for the control sample.