Journal
JOURNAL OF FOOD ENGINEERING
Volume 79, Issue 2, Pages 553-560Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.jfoodeng.2006.02.015
Keywords
colour; thermal treatment; high pressure treatment; tomato; strawberry
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Visual colour degradation of tomato puree and strawberry juice at three different pH values (2.5, 3.7 and 5) during thermal (100140 degrees C, 0-120 min) and high pressure thermal (300-700 MPa, 60 min, 65 degrees C) treatments were studied. Hunter colour scale values L*, a* and b* of each treated sample were measured. Results indicated that the thermal degradation of tomato and strawberry colour followed first order kinetics (fractional conversion model). The L*a*/b* parameter combination described best the colour change of all samples. The activation energies for the different material were 129.12, 181.40, 162.60, 85.77 kJ/mol x 10(-2) for tomato puree, strawberry at pH 2.5, strawberry at pH 3.7, and strawberry at pH 5, respectively. Colour of strawberry at pH 5 was less heat stable but the degradation constants were less sensitive to temperature changes. No colour degradation of tomato appeared under combined thermal and high pressure treatment; a maximum increase of 8.8% in L*a*/b* parameter was found for strawberry samples (pH 5). (c) 2006 Elsevier Ltd. All rights reserved.
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