Modeling Distribution and Dissipation Kinetics of Pesticides in Peel and Medulla Tissues of Postharvest Tuber Crops

To
evaluate pesticide distribution and dissipation patterns in
postharvest tubers, a peel model under open-environment conditions
was developed, which could specify the fate of pesticides in the peel
and medulla (pulp) compartments. The simulated results for over 700
pesticides in potatoes indicated that the pesticide degradability
in crop tissues contributed the most to the overall dissipation in
the medulla compartment than other physiochemical properties. The
dissipation process in potato medullas was diminished by the peel
compartment, indicating that the peel acts as a protective layer,
particularly for highly lipophilic pesticides with high peel-to-medulla
concentration ratios at harvest. In addition, the simulated results
showed that the peel-to-medulla pesticide concentration ratios decreased
significantly immediately after potatoes were harvested (e.g., 1 or
3 days after harvest), which was consistent with the field observations,
indicating that pesticide distribution in the peel and medulla compartments
achieved steady state if the source of the pesticide was blocked (i.e.,
pesticide residues in soil). Furthermore, the simulated reduction
factors of pesticides in potato medullas were parametrized using the
nonpeel model, which helped derive the equivalent half-lives of pesticides
in potato medullas after accounting for the peel effect. It was concluded
that the tuber peel can act as a protective layer to reduce residue
dissipation in medulla tissues, and the dissipation half-lives of
pesticides in cold storage (e.g., 5 °C) can be over two times
longer than those at room temperature. The present study provides
a modeling perspective on pesticide dissipation kinetics in postharvest
tuber crops, and the simulated results can be combined with other
food processing factors to evaluate the fate of pesticide residues
in the tuber food supply chain.