Abstract
The effects of heat blanching and UV-C light followed by heat on Portuguese cabbage peroxidase (POD), colour and texture were studied in the temperature range of 80-95 °C. POD inactivation, lightness (L) and yellowness (b) colour changes were described by a first-order reaction model. The greenness (a) colour and texture (firmness) changes followed a two fraction kinetic model behaviour. The temperature effect was well described by the Arrhenius law.At lower temperatures the combined treatment showed higher POD inactivation. Colour and texture parameters did not show significant differences between treatments. Long processing times turned the leaves slightly darker, decreased greenness, yellowness and firmness. Short processing times increased the firmness and greenness of the leaves. The treatment at 80 °C for 90 seconds reduced 90% of POD, retaining 98% of lightness and 92% of yellowness and improved the green colour (130%) and firmness (125%). At 80 °C the heat blanching required 7.4 min to inactivate 90% of the enzyme activity, reducing lightness, greenness, yellowness and firmness to 92%, 68%, 62% and 61%, respectively. The present findings will help to optimize the Portuguese cabbage blanching conditions.
Highlights
Portuguese cabbage (Brassica oleracea L. var. costata DC) is a very popular cabbage in Portugal together with galega cabbage, all very rich in vitamins and mineral salts, being the major ingredient in the traditional kale soup and in the “cozidoa portuguesa”
On the basis of these considerations and the few studies available in the literature reporting the effect of blanching treatments on cabbage leaves (Alvarez-Jubete, Valverde, Patras, Mullen, & Marcos, 2014; Jaiswal, Gupta, & Abu-Ghannam, 2012), the aim of this work was to evaluate the kinetics of Portuguese cabbage POD inactivation, colour and texture changes during heat blanching and an alternative blanching process (UV-C light followed by heat blanching) and with the findings help to optimize the Portuguese cabbage blanching conditions
The samples were separated in two groups according to the treatment to be applied: UV-C light followed by heat blanching group and the heat blanching group
Summary
Portuguese cabbage (Brassica oleracea L. var. costata DC) is a very popular cabbage in Portugal together with galega cabbage, all very rich in vitamins and mineral salts, being the major ingredient in the traditional kale soup and in the “cozidoa portuguesa” (traditional dish consist-ing of boiled cabbage with sausages, beef and pork). The application of physical factors, such as temperature and/or pressure, combined with UV-C light, may result in the increase of the enzymatic activity, followed by further inactivation These techniques used in combination (or sequentially), normally referred to as hurdle technologies, have been used as less severe heat treatments, resulting in higher quality and safer products than traditional treatments (Manzocco, Dri, & Quarta, 2009). On the basis of these considerations and the few studies available in the literature reporting the effect of blanching treatments on cabbage leaves (Alvarez-Jubete, Valverde, Patras, Mullen, & Marcos, 2014; Jaiswal, Gupta, & Abu-Ghannam, 2012), the aim of this work was to evaluate the kinetics of Portuguese cabbage POD inactivation, colour and texture changes during heat blanching and an alternative blanching process (UV-C light followed by heat blanching) and with the findings help to optimize the Portuguese cabbage blanching conditions
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