Polymorphism and Microstructural Changes in Avocado Pulp (<i>Persea americana</i> Mill.) After Scraped-Surface Heat Exchanger Processing

Abstract

Avocado (Persea americana Mill.) is a fruit with a high content of unsaturated fatty acids and bioactive compounds, whose consumption has considerably increased in the USA and Europe. Thus, the conservation of the avocado mesocarp (pulp) has become more relevant. Avocado pulp was processed using a scraped-surface heat exchanger (SSHE) system to extend the shelf-life of the mesocarp. Through analysis with X-ray diffraction and HRTEM, it was possible to identify crystalline-type structures in the avocado pulp processed and stored at 4 °C. The 2θ-angles and d-spacing of the structures that reported the highest diffraction intensity are comparable to the polymorphs β′ reported in the literature for fatty acid mixtures processed under similar conditions. Furthermore, the X-ray signals suggest the presence of polymorphs α and β in all samples processed and stored at different temperatures. Calorimetry analysis showed curves with first-order phase changes as indicative of crystallization-type transitions. The shelf-life evaluation of the avocado pulp showed that the crystallization process minimized the losses of antioxidant capacity and prevented color change, while the enzyme polyphenol oxidase remained inactivated. The changes induced by the SSHE continuous processing applied might represent an alternative to obtaining avocado products that preserve avocado’s properties and extend its shelf-life.

Keywords

• polymorphism
• X-ray diffraction
• HRTEM
• avocado
• scraped-surface heat exchanger