Product development led to understanding of scaling aspects and improvement of quality and taste for particularly dry healthy snack applications (fruits and vegetables) and industrial food applications such as instant foods (vegetables), bakery applications (fruits) and seasoning (herbs). Along the project, several scale-up hurdles have been taken and removed as risks for further implementation, including (food-grade) design aspects, product stability aspects. Product quality aspects have been addressed via sensory trials, through qualified panels and a range of audience groups along the food chain, including shelf-life testing.
Food safety benefits were further investigated at two lab scales and a pilot scale. Microbial inactivation was tested for coriander, apple and strawberry at lab scale for important pathogenic microorganisms (E. coli O157:H7, S. enterica, S. aureus, and L. monocytogenes), resulting 4-6 log CFE/g reductions, confirming that scCO2 drying is an efficient technology to reduce the microbial contamination in different food matrices at lab scale. Further food safety issues were determined, such as the effect of the process on fungal spores, the potential resistance of bacterial spores and the potential influence of the food pH on any resistance were investigated as well as potential presence of injured but viable cells that could retain their ability to produce toxins during the storage. Overall, these lab studies indicated that although CO2 drying has limitations regarding spores inactivation and removal of toxins, it is a promising technique for decontamination of vegetative cells and fungal spores. Large scale trials (160 liter) confirmed the inactivation capability for naturally present microorganisms, such as aerobic mesophilics, coliforms and enterobacteria. Using a risk assessment, the microbial safety and long term shelf life of CO2 dried foods was demonstrated using above data, showing it to have the potential to considerably raise the microbiological quality of dried products.
Demonstration of products such as apple and beetroot was performed in a near-industrial environment and products presented at a number of fairs, interested parties for review on taste, appearance and appeal, with overall positive review.
It can consequently be concluded that CO2 drying can interesting low-temperature drying technology with benefits in terms of environmental performance, food safety and food structure.
