Optimization of packaging and storage conditions of a freeze‐dried Pantoea agglomerans formulation for controlling postharvest diseases in fruit

AIMS: This study aimed to evaluate different packaging strategies to extend the shelf life of a freeze‐dried formulation of the biocontrol agent Pantoea agglomerans strain CPA‐2. METHODS AND RESULTS: Different materials and atmosphere packaging conditions (vacuum and air) were analysed on formulated P. agglomerans cells stored at 25, 5 and −20°C. Results showed the viability of CPA‐2 cells stored at 5 or −20°C was significantly higher than when stored at 25°C. The highest viabilities were observed with the plastic material designated as Bottle 1, in nonvacuum packaging in all storage temperatures: 50% after 3 months at 25°C, 100% after 8 months at 5°C and 100 and 74% after 12 and 18 months, respectively, at −20°C; the final concentration was 10¹² CFU g⁻¹, a good concentration for a commercial product. The efficacy to control blue and green mould on apples and oranges, respectively, of these packed and stored cells was similar to fresh CPA‐2 cells. CONCLUSIONS: This work showed a suitable packaging strategy for a freeze‐dried formulation of the CPA‐2, providing a good shelf life and efficacy against the major postharvest diseases of apples and citrus based on a plastic bottle stored at cold or frozen storage conditions. SIGNIFICANCE AND IMPACT OF THE STUDY: The last phase of the commercial development process for biocontrol agents is presented in this work. A bacterium‐based product that ensures the efficacy, stability and easy application of the antagonist to control postharvest fungal diseases on fruit was successfully obtained.