Growth of Listeria monocytogenes in Fresh-Cut Coconut as Affected by Storage Conditions and Inoculum Size

In this study, the effects of packaging atmosphere (air and modified atmosphere, 65% N₂, 30% CO₂, and 5% O₂), temperature (2, 4, 8, and 12°C) and inoculum size (low inoculum, 10² CFU/g; high inoculum, 5 × 10⁵ CFU/g) on the growth of Listeria monocytogenes in minimally processed coconut were investigated. Growth data were fitted to the Gompertz equation, and the sanitary risk time (the time, in days, necessary to observe an increase of 2 log CFU/g in the level of the pathogen) was also calculated. At a higher inoculum level, the health risk was more marked; moreover, as shown by parameter A of the Gompertz equation (maximum increase of cell load data), the sanitary risk time seemed not to be influenced by temperature or by atmosphere type. At a low inoculum level in the air-stored product, the sanitary risk time was strongly influenced by temperature, and a modified atmosphere caused a significant increase in the maximum cell load reached in the stationary phase. The results show that L. monocytogenes not only survives but is able to proliferate on fresh-cut coconut stored in air as well as in a modified atmosphere, even at a very low temperature (2°C); moreover, the presence of a high cell load can lead to a health risk because this pathogen can grow to risk level during the shelf life of the product.