Effect of selected thermal processes on antioxidant properties of berry fruit homogenates
Journal Title: Żywność. Nauka. Technologia. Jakość - Year 2016, Vol 23, Issue 2
Abstract
The objective of the research study was to determine the effect of various heating and freezing techniques, as well as of the defrosting and frozen storage on the antioxidant properties of berry fruit homogenates. The experimental material consisted of strawberry, blackcurrant, cranberry, and chokeberry homogenates. The raw material was thermally treated, i.e. it was heated (using a gas stove, a microwave oven, and a Thermomix multifunction device) and frozen. The frozen samples were stored at a temperature of -24 ºC: 1) for 3 days, to determine the effect of freezing process on the antioxidant properties of homogenates; 2) for 90 days to determine the effect of frozen storage on those properties. Prior to the analysis, the samples were defrosted in air (at a temperature of approx. 21 ºC) and in a microwave oven. In the raw material, there were assayed: content of vitamin C, reducing power, and ability to scavenge free radicals. The blackcurrant homogenate contained the highest amount of vitamin C (6.4 mg/g of dry matter), whereas the strawberry homogenate was characterized by the highest reducing capability (670.2 mg of ascorbic acid/g of dry matter). The thermally treated chokeberry homogenates were the most effective scavengers of free radicals (EC50 = 1.52 g of dry matter/g of DPPH). A temperature above 950C caused the highest losses in vitamin C in the blackcurrant homogenates; those losses were lower in the microwave-heated homogenates than in the conventionally heated ones. The heating caused the reducing properties and free radical-scavenging activity to increase; the increase was higher when heating by a traditional method. The frozen storage caused the content of vitamin C and the scavenging capability of free radicals to decrease. As for the reducing power, the effect of storage depended on the raw material. A decrease was reported in the reducing power of the blackcurrant and strawberry homogenates, while the reducing power of cranberry and chokeberry homogenates increased.
Authors and Affiliations
Grzegorz Fiutak, Ewa Hajduk, Magda Filipczak-Fiutak, Ryszard Macura, Bożena Firek
Keywords
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- EP ID EP144115
- DOI 10.15193/zntj/2016/105/119
- Views 63
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