Changes in β-carotene, chlorophyll and color of spinach puree during ohmic heating
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Date
2010
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Abstract
The spinach puree was heated from 30C to prescribed temperatures (60, 70, 80 or 90C) ohmically and conventionally. Ohmic heating was performed by application of four different voltage gradients in the range of 10-40 V/cm, while conventional heating was conducted at constant temperature in a water bath. Although ohmic heating time required from 30 to 70C was similar for water heating (129 ± 7 s) and ohmic heating by 20 V/cm (127 ± 2 s), faster heating (51 ± 0.5 s) could be obtained as the voltage gradient for ohmic heating increased to 30 V/cm. Ohmic heating caused browning more than conventional water heating for the same temperature range. The effect of voltage gradient applied was not found statistically significant on chlorophyll (total, a and b), β-carotene and color values (L, a, b, Lb/a, Lba, hue angle) (P < 0.05). On the other hand, temperature (60, 70, 80 or 90C) at constant voltage gradient (30 V/cm) affected color values of spinach puree (P < 0.05), whereas holding time (0 and 600 s) at constant temperature increased chlorophyll-a and β-carotene contents (P < 0.05). This increase could be caused by the possible enhancing effect of ohmic heating on β-carotene biosynthesis and formation of chlorophyll derivatives. It was concluded that ohmic heating could be applied to vegetable purees, resulting in high retention of color attributes and β-carotene. © 2009 Wiley Periodicals, Inc.
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Keywords
Spinacia oleracea , Biochemistry , Chlorophyll , Color , Color computer graphics , Heating equipment , Porphyrins , Chlorophyll a , Chlorophyll derivative , Color attributes , Color values , Constant temperature , Constant voltage , Conventional heating , Enhancing effect , Holding time , Ohmic heating , Temperature range , Voltage gradient , Water baths , Water heating , Heating