Multifunctional starch-based active packaging film with pH-triggered release of tea tree oil for blueberry preservation

The traditional methods used for storing fresh blueberries fresh are expensive and do not always maintain food safety. In this study, tea tree oil (TTO) was first packed into a covalent organic framework (CTT), and this CTT@TTO was blended into a starch matrix to create a multifunctional film for packaging blueberries. The CTT exhibited an exceptional TTO loading capacity of 1113.9 ± 1.1 mg/g. Compared to the starch film, the starch film with 4% CTT@TTO increased the tensile strength by 82.9%, reduced water vapor permeability by 19.2% and oxygen transmission rate by 24.3%, and achieved bacterial inhibition rates 98.8%, 99.9%, and 100% against Escherichia coli, Staphylococcus aureus, and Botrytis cinerea , respectively. The observed enhancements can be attributed to the establishment of robust hydrogen bonds between CTT@TTO and the starch matrix. The release kinetics of TTO from the starch matrix conformed to Avrami models. The release rate at pH 3 was faster than that at pH 6. Blueberries wrapped in the starch film with 4% CTT@TTO maintained significantly higher quality after 9 days of storage. The developed starch/CTT@TTO film shows potential value for increasing the shelf life of blueberries.