Quality characteristics of carrot puree processed by continuous flow microwave heating as compared to conventional heating

Gulsah Bakir, Purdue University

Abstract

Continuous flow microwave heating is an emerging technology in thermal processing of liquid, viscous, or pumpable food products such as carrot puree. Carrot (Daucus carota) is one of the world's leading vegetable crops. Consumption of carrot has increased due to its pleasant flavor, nutritious content and perceived health benefits related to vitamin A. Conventional thermal processing of carrot puree requires long processing times at high temperatures to inactivate Clostridium botulinum and achieve commercial sterility during the shelf life of the product. The excessive heat treatment causes degradation of nutrients, color, flavor, and texture. Microwave heating has advantages over conventional heating such as short come-up time, fast and efficient volumetrically heating. In the present study, carrot puree was thermally processed by a lab-scale 6-kW continuous flow microwave system at 90°C and 141°C at different holding times. Carrot puree was also processed conventionally by a tubular heat exchanger to compare with microwave processing. In spite of differences in processing conditions, the effects of continuous flow microwave heating on color and carotenoids (&agr;-, β-carotene) content of carrot puree were found superior as compared to conventional heating. At high sterilization temperatures isomerization of β-carotene which could contribute to lower vitamin A activity was significantly lower (55%) in microwave processed carrot puree than its conventionally heated counterparts. In addition, in-vitro bioaccessibility studies indicated that heating of carrot puree increased the bioaccessibility of α- and β-carotenes between 5 to 22%, and thus their potential bioavailability. These findings support that efficacy of continuous flow microwave heating in preserving quality of carrot puree as compared to conventional heating methods.

Degree

M.S.

Advisors

Martin-Gonzalez, Purdue University.

Subject Area

Food Science

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