Processing and quality characteristics of apple slices under simultaneous infrared dry-blanching and dehydration with continuous heating

Abstract

This study investigated the effects of various processing parameters on apple slices exposed to infrared (IR) radiation heating in a continuous heating mode for achieving simultaneous infrared dry-blanching and dehydration (SIRDBD). The investigated parameters were radiation intensity, slice thickness and processing time. A three-factor factorial experiment design was conducted to determine the influence of parameters on the heating and drying rates, product temperature, moisture reduction, residual polyphenol oxidase (PPO) and peroxidase (POD) activities and surface color change (Δ E). High radiation intensity and/or thin slices had faster increase of product temperature, and quicker moisture removal and inactivation of PPO and POD, than did low radiation intensity and/or thick slices. The simple page model performed well for describing drying behavior during SIRDBD. The first-order kinetics and the fractional conversion models fitted well for PPO and POD inactivation curves, respectively. Surface color changes of apple slices were mainly due to the decrease of L value and increase of a value, which corresponded to enzymatic browning occurred during the process. To achieve 1 log reduction of POD, the SIRDBD treatments resulted in moisture reductions of 15.35–49.29% and Δ E between 2.030 and 5.518. It has been concluded that SIRDBD with continuous heating could be used as an alternative to the current processing methods for producing high-quality blanched and partially dehydrated fruits and vegetables.