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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

Location: Healthy Processed Foods Research

Title: Quality Characteristics of Dried Bananas Produced with Infrared Radiation Technology

Authors
item Pekke, Milly - 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: Pekke, M., Pan, Z. 2007. Quality Characteristics of Dried Bananas Produced with Infrared Radiation Technology. Annual Meeting of the Institute of Food Technologists. July 28-August 1, 2007, Chicago, IL

Interpretive Summary: This study was to investigate quality characteristics of bananas dried using infrared radiation with natural convection as compared to conventional hot air drying with forced convection. Results show that drying with IR with natural convection does not reduce drying time compared with conventional hot air drying when the product temperature is kept constant. However, a lighter product color and complete inactivation of polyphenol oxidase can be achieved with the use of IR radiation for drying.

Technical Abstract: Browning of fruits during drying is a major quality concern. The enzyme polyphenol oxidase has been found to be the main cause of browning in bananas. Infrared radiation (IR) drying could be used to minimize enzymatic browning hence eliminating the need for pre-treatments. This study was to investigate quality characteristics of bananas dried using infrared radiation with natural convection as compared to conventional hot air drying with forced convection. Cavendish bananas of 8 mm thickness were dried with infrared and hot air dryers at 60 degrees C, 70 degrees C and 80 degrees C product temperature. Changes in residual polyphenol oxidase (PPO) activity, color, moisture content and water activity were measured after four hours of drying. Freshly cut bananas were used as a control. Total inactivation of polyphenol oxidase was achieved with IR at all temperatures but only 3% reduction was reached with hot air at 60 degrees C. L-value was reduced to 72%, 73% and 61% in IR dried bananas and 60%, 65% and 71% in hot air at 60 degrees C, 70 degrees C and 80 degrees C respectively. IR drying reduced water activities (Aw) to 0.72, 0.65 and 0.52 whereas with hot air they reduced to 0.69, 0.55 and 0.45 at 60 degrees C, 70 degrees C and 80 degrees C respectively. After 4 hours of drying, moisture content in hot air dried bananas reduced to 19%, 12% and 8% (db) and to 27%, 21% and 12% in IR at 60 degrees C, 70 degrees C and 80 degrees C respectively. Nevertheless, drying rates were higher during IR than hot air drying at least during the first 20 minutes of drying. Results show that drying with IR with natural convection does not reduce drying time compared with conventional hot air drying when the product temperature is kept constant. However, a lighter product color and complete inactivation of polyphenol oxidase can be achieved with use of IR radiation for drying.

Last Modified: 8/22/2014
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