Abstract
Perforation-mediated modified atmosphere packaging (PM-MAP) consists of packing fresh produce in an airtight package perforated by one or more tubes. The interplay between the product respiration rate (RR) and the rate of gas exchange through the tube(s) promotes an increase in CO[sub2] and a decrease in O[sub2] concentration, the atmosphere eventually levelling off. The objective of this work was to design and validate a package for shredded carrots, based on mathematical models earlier developed for predicting RR and gas exchange rate. Different amounts of produce and tube dimensions were selected and experiments were performed at 10 ordm;C (50 ordm;F). Predicted and experimental gas compositions were quite different and anaerobiosis was observed in almost every package. This might be explained by an increase of RR during storage, as earlier reported for shredded carrots stored in air. Another set of experiments was then performed, halving the amount of produce, and the equilibrium gas composition was in the recommended range. The RR at steady state was calculated by a mass balance and it was found that the values were approximately three-fold those obtained with the predictive model, which explains the difference between prediction and validation results. The respiratory quotient was however similar, approximately one, which shows that storage time increases RR but does not influence the underlying mechanisms. It can therefore be concluded that the design of MAP for shredded carrots needs to take the effect of storage time on RR into consideration. As a rule of thumb, package design might be based on the triple of RR predicted by existing models.
