|Pan, Zhongli - John|
Submitted to: Proceedings of the American Society of Agricultural and Biological Engineers International (ASABE)
Publication Type: Proceedings
Publication Acceptance Date: 5/20/2008
Publication Date: 6/29/2008
Citation: Zhu, Y., Pan, Z. 2008. Comparison Between the Continuous and Intermittent Heating Methods for Simultaneous Infrared Dry-Blanching and Dehydration of Apple Slices. Proceedings of the American Society of Agricultural and Biological Engineers International (ASABE). Paper No. 084053. 1-10. Interpretive Summary: This paper reported the processing and product characteristics of apple slices under infrared heating with two different heating modes. The recommended processing method has been suggested to achieve desired product quality.
Technical Abstract: Simultaneous infrared dry-blanching and dehydration (SIRDBD) can be operated in two heating modes, continuous and intermittent heating. Under continuous heating, infrared radiation intensity was kept constant while the product temperature remained constant under intermittent heating in this study. Both heating modes showed success in blanching and partially dehydrating apple slices. The objective of this study was to compare the product quality under the two heating modes and provide recommendations of processing conditions for different manufacturing purposes. The three-factor factorial experimental design was used to investigate the effects of processing parameters, including apple slice thickness, processing time, and radiation intensity for continuous heating or slice surface temperature for intermittent heating, on final product quality in terms of surface color, moisture reduction, and polyphenol oxidase (PPO) and peroxidase (POD) activities. The results showed that the continuous heating mode resulted in a shorter processing time, lower moisture reduction, and similar overall surface color change than the intermittent heating mode to achieve about 90% POD inactivation. When prolonged heating was needed (e.g., more than a 1 log reduction of POD), the intermittent heating mode was more advantageous in the preservation of surface color than the continuous heating mode since no severe darkening occurred. To achieve a 1 log reduction of POD, the continuous heating mode resulted in moisture reductions in the range of 15.35% to 49.29% and overall surface color change (delta E) of 2.030 and 5.518, while the intermittent heating mode led to moisture reductions of 19.78% to 59.48% and delta E of 2.274 and 5.5880. For quick blanching purposes, the recommended processing conditions are continuous heating under medium to high radiation intensities (4000-5000 W/m2) for 5 to 13 mm thick slices. If large moisture reduction is desired at the same time of blanching, intermittent heating at 75ºC is suggested.