Tag Archives: phenolic compounds

1546-1554 R. Zarins, Z. Kruma, L. Tomsone, S. Kampuse, I. Skrabule and I.H. Konosonoka
Comparison of phenolic compounds and antioxidant activity of fresh and freeze-dried potatoes
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Comparison of phenolic compounds and antioxidant activity of fresh and freeze-dried potatoes

R. Zarins¹, Z. Kruma¹*, L. Tomsone¹, S. Kampuse¹, I. Skrabule² and I.H. Konosonoka²

¹Latvia University of Agriculture, Faculty of Food Technology, Department of Food Technology, Rigas iela 22, LV-3004 Jelgava, Latvia
²Institute of Agricultural Resources and Economics, Zinātne iela 2, Priekuli, Priekuli municipality, LV-4126 Latvia
*Correspondence: zanda.kruma@llu.lv

Abstract:

Potatoes (Solanum tuberosum L.) contain a wide range of compounds with health benefits, and different techniques have been developed for the determination of these compounds. Freeze-drying is a common method for the preservation and preparation of samples for the analyses of bioactive compounds, but it is well known that drying influences the composition of food products. The aim of the current study was to compare phenolic compounds and antioxidant activity of fresh and freeze-dried potatoes. In the experiment 11 cultivar potatoes grown in experimental fields of the Institute of Agricultural Resources and Economics in 2016 were analysed. Potatoes were freeze-dried. Homogenized fresh and freeze-dried samples were extracted with an ethanol/water (80/20 w/w) solution. Total phenolic content (TPC) was determined using the Folin-Ciocalteu method, and the antioxidant activity was evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH˙) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) assays. The highest TPC and radical scavenging activity were determined in cultivars ‘Peru Purple’ and ‘Blue Congo’ potatoes. Freeze-drying influenced all the tested parameters but more significantly the TPC, and for certain cultivars a reduction of more than 30% was observed. A strong correlation between TPC, DPPH and ABTS in fresh and freeze-dried samples was observed, r = 0.81, r=0.93, r = 0.92, respectively. It could be concluded that the effect of freeze-drying on TPC and antioxidant activity is cultivar dependent.

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1316–1329 L. Klavins, J. Kviesis, M. Klavins
Comparison of methods of extraction of phenolic compounds from American cranberry (Vaccinium macrocarpon L.) press residues
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Comparison of methods of extraction of phenolic compounds from American cranberry (Vaccinium macrocarpon L.) press residues

L. Klavins, J. Kviesis, M. Klavins*

University of Latvia, 19 Raina Blvd., LV–1586, Riga, Latvia
*Correspondence: maris.klavins@lu.lv

Abstract:

American cranberries (Vaccinium macrocarpon L.) contain significant quantities of
various phenolic compounds. Most of these compounds are recovered when berry juice is
produced. However, a considerable part of polyphenols remain in berry press residues and are
discarded as food industry waste. The aim of the study was to compare the methods of extraction
of polyphenols (ultrasound, microwave-assisted, Soxhlet) from press residues of American
cranberry. The impact of main extraction parameters (e.g., extraction time, solid/solvent ratio,
solvent type) on the yield of extracted polyphenols. Ultrasound-assisted extraction showed the
highest potential from all studied methods, given its fast, convenient use and low cost. Aqueous
ethanol and methanol in the presence of acid (anthocyanin extractions should be assisted with
trifluoroacetic acid, polyphenol extractions – with HCl) were assessed as the best solvents for
extraction. The obtained extracts were characterised using the Folin-Ciocaulteu method for
determination of total phenolics and the pH-differential method for determination of total
anthocyanins, and UPLC–PDA was used to determine the content of individual anthocyanins.
Cyanidin-3-O-arabinoside, peonidin-3-O-galactoside, peonidin-3-O-glucoside and peonidin-3-
O-arabinoside were identified as the main anthocyanins in cranberry press residue extracts.

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