Infrared thermographic investigation of the use of microcrystalline wax to preserve apples from thermal shocks

Abstract

This paper aims to prove the feasibility and effectiveness of using microcrystalline wax in order to preserve fruit from thermal shocks due to temperature changes or thermal excursions during food supply chain. Wax is a natural substance which covers the surface of some species of fruits such as the apples. This wax layer protects the fruit against parasites, atmospheric agents, thermal excursions, moisture loss, mechanical damage and microbiological infections. These singular features are currently object of studies and research activities aimed to develop new synthetic substances obtained by natural extracts or essences.Active infrared thermography has been used in this work to study the thermal response of apples to ambient temperature changes. The experimentation has been performed on the Golden Delicious variety. Two different apple sets have been considered. The first set was composed of apples covered by their own natural wax layer. The second set was composed of apples coated with an additional artificial microcrystalline wax layer. Their thermal responses have been put in comparison after a cooling process inside a climatic chamber. Measurements have been performed under controlled environmental conditions to assure the repeatability and reproducibility of data. By using an infrared camera, the thermal response of the two apple sets has been recorded and the heating rates have been compared. The wax coated apples have showed a slower heating rate due to the thicker wax layer. As a consequence, the coated apples have shown a reduced influence to external temperature variations. The final aim of this study is to reproduce artificially bio-wax films in order to cover and protect fruits during their life cycle from the tree to the table.