STRATEGIES TO ENHANCE FOOD SAFETY IN FRESH APPLE PACKING PROCESS

Ewa   Pietrysiak

STRATEGIES TO ENHANCE FOOD SAFETY IN FRESH APPLE PACKING PROCESS Abstract by Ewa Pietrysiak, Ph.D. Washington State University December 2019 Chair: Girish M Ganjyal Apples are one of the most valuable fruit crops in the United States, and a critical component to the Washington state economy. Approximately 70% of the produced apples are consumed as fresh or minimally processed. The post-harvest packing process of fresh apples does not include any “kill step” that would inactivate or eliminate all pathogenic bacteria of concern. Recent listeriosis outbreaks revealed that insufficient cleaning and sanitation practices in fresh apple packing houses may lead to contamination of fruit with Listeria monocytogenes. Therefore, there is a need for improvement of food safety systems in the fresh apple packing industry. The aim of this dissertation was to develop strategies to reduce microbial load on fresh apples in packing process. This goal was approached by (1) assessment of existing methods of microbial reduction in fresh produce and their applicability in apple industry, (2) investigation of the relationship between apple fruit surface morphology and bacteria attachment, and (3) the development of new decontamination methods appropriate for use in fresh apple packing process. Removal of bacteria from the surface of an apple fruit is difficult due to its morphology. The irregular shape of apples, the hydrophobic character of the surface of the wax layer, and the presence of microstructures on the apple peel surface facilitate bacterial attachment. Bacteria harbored in surface microstructures may be protected from cleaning interventions, thus reducing the effectiveness of cleaning treatment. The so-called hurdle technology may give the best results and improve the decontamination efficiency, however more research is needed for the development of effective strategies of reducing microbial loads on fresh apples. The application of surfactants combined with sanitizer followed by hot air impingement drying helped to decrease the bacterial count on apple surfaces and reduced the time needed to dry apples. The addition of surfactants reduced the surface tension of cleaning solutions, improved their spread on the apple surface and facilitated detachment and deactivation of the Listeria. Outcomes of this dissertation provide applicable knowledge that can help to improve food safety systems in the fresh apple packing industry.

STRATEGIES TO ENHANCE FOOD SAFETY IN FRESH APPLE PACKING PROCESS

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