The effect of addition of chokeberry, flowering quince fruits and rhubarb juice to strawberry jams on their polyphenol content, antioxidant activity and colour |
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Authors: | Aneta Wojdy?o Jan Oszmiański Irena Bober |
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Affiliation: | (1) Department of Fruit, Vegetable and Cereals Technology, Wroclaw Environmental and Life Science University, 25 Norwida Street, 50-375 Wroclaw, Poland |
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Abstract: | The aim of the study was to establish whether the addition of berries (flowering quince, chokeberry) and rhubarb juice during
jam processing improves its colour and enriches jams in polyphenol compounds other than those found in strawberries. The sum
of phenolic compounds determined by HPLC was distributed in a wide concentration range depending on the cultivar. Jams prepared
from Elkat cultivar had 27% more total phenolic compounds than jams prepared from Senga Sengana. The following compounds were
identified in jams prepared from strawberries: p-coumaric, ferulic and ellagic acids, quercetin, kaempferol, anthocyanins, (+)-catechin, (−)-epicatechin and proanthocyanidins.
Proanthocyanidins and ellagic acid are the major polyphenol compounds of all strawberries jams. The Elkat cultivar (47.34 mg/100 g)
contained higher amounts of proanthocyanidins compared to Senga Sengana (29.95 mg/100 g). The addition of 10% of flowering
quince and chokeberry to jams during their preparation resulted in the increase in the content of phenolic components in final
products, especially for proanthocyanidins. The highest level of total polyphenols (P < 0.05) was found in strawberry mixed with chokeberry, 237.82 mg/100 g for Senga Sengana and 260.61 mg/100 g for Elkat. There
has been a marked increase of proanthocyanidins content (5.4 and 4.0 times) in jams made from Senga Sengana and Elkat cultivars
mixed with chokeberry. However, the addition of rhubarb juice did not increase the content of polyphenol in Senga Sengana
jam (not statistically significant). Antioxidant activity of strawberry jam was determined by 2,2′azinobis-(3-ethylbenzthiazoline-6-sulphonic
acid (ABTS), 1,1-Diphenyl-2-picrylhydrazyl radical (DPPH) and ferric reducing/antioxidant power methods (FRAP). The antioxidant
activity of this mixed jam was more than two times higher (P < 0.05) than control sample of strawberry jam. Rhubarb juice had high effect on L* (lightness) value in case of all strawberry varieties. The redness (a*), and yellowness (b*) were significantly different in jams with supplement. Strawberry jam with chokeberries had smaller L* value than control and other samples, and the lowest a* and b* values. This variation could be due to the nature of the pigments in these fruit cultivars and the content of anthocyanins
which resulted in more reddish colour. |
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Keywords: | Strawberry jams Polyphenols Antioxidant activity Colour Chokeberry Flowering quince Rhubarb |
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