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United States Department of Agriculture

Agricultural Research Service

Research Project: NEW TECHNOLOGIES TO PROCESS VALUE-ADDED, HEALTHY FOODS FROM FRUITS AND VEGETABLES Title: Simultaneous Infrared Dry-Blanching and Dehydration of apple slices Controlled by Intermittent Heating Mode

Authors
item Zhu, Yi - UC DAVIS, DAVIS, CA
item Pan, Zhongli

Submitted to: Annual Meeting of the Institute of Food Technologists
Publication Type: Abstract Only
Publication Acceptance Date: March 1, 2007
Publication Date: July 28, 2007
Citation: Zhu, Y., Pan, Z. 2007. Simultaneous Infrared Dry-Blanching and Dehydration of Apple Slices Controlled by Intermittent Heating Mode. Annual Meeting of the Institute of Food Technologists. July 28-August 1, 2007. Chicago, IL

Interpretive Summary: Infrared heating controlled by intermittent heating mode was found to be able to achieve simultaneous dry-blanching and dehydration of apple slices with a desirable quality. In order to better understand the performance of intermittent heating for simultaneous dry-blanching and dehydration (SIDBD), the relationship between process variables and product quality was investigated. It is concluded that intermittent infrared heating can be used to simultaneously blanch and dehydrate fruits and vegetables since it satisfactorily inactivates the enzymes and removes a desirable amount of moisture while preserving surface color.

Technical Abstract: Infrared heating controlled by intermittent heating mode was found to be able to achieve simultaneous dry-blanching and dehydration of apple slices with a desirable quality. In order to better understand the performance of intermittent heating for simultaneous dry-blanching and dehydration (SIDBD), the relationship between process variables and product quality was investigated. The objective of this research was to study the influence of processing parameters of SIDBD with intermittent heating mode on processing characteristics and product quality. An infrared dry-blancher/dehydrator equipped with two catalytic IR emitters powered with natural gas was used. Apple slices were heated from both top and bottom sides with constant product surface temperature maintained by controlling the on and off time of natural gas supply to the emitters. Three studied processing parameters were surface temperature (70, 75, 80°C), processing duration (from 0 to 40 min), and sample thickness (5, 9, 13 mm). The measured processing characteristics were moisture removal, drying and heating rates, and product quality, including residual enzyme activity of polyphenol oxidase (PPO) and peroxidase (POD), and surface color change. Our results showed that higher surface temperature (80°C) resulted in higher center temperature, faster inactivation of enzymes and less change in surface color than lower surface temperature (70°C). After 10 min, all the processing conditions resulted in more than 90% inactivation of PPO but the residual POD activities were still high (4~23%). Compared to continuous heating, intermittent heating took longer time to reach the same level of enzyme inactivation but never caused the burning of samples. It is concluded that intermittent infrared heating can be used to simultaneously blanch and dehydrate fruits and vegetables since it satisfactorily inactivates the enzymes and removes a desirable amount of moisture while preserving surface color.

Last Modified: 11/28/2014