Antioxidantes uvas

Scientia Horticulturae 111 (2007) 235–241 www.elsevier.com/locate/scihorti

Total antioxidant activities, phenolics, anthocyanins, polyphenoloxidase activities of selected red grape cultivars and their correlations
¨ H. Hulya Orak *
˘ ˘ Trakya University, Tekirdag Agricultural Faculty, Food Technology Department of Vocational College, Tekirdag, Turkey Received 17 November 2005; received inrevised form 13 June 2006; accepted 24 October 2006

Abstract ¨ ¨ ¨ ¨ ˘ ¸ ¨ Sixteen red grape cultivars (Md. Jean Matthias, Okuzgozu, Muscat Hamburg, Cabarnet Sauvignon, Tekirdag Cekirdeksizi, Gewurztraminer, ´ ˘ 2B/56, Kalecik karası, Carignan, Kokulu Siyah, Alfonse Lavallee, Bogazkere, Adakarası, Papazkarası, Mourvedre and Cinsaut) which are grown ˘ in Tekirdag Viticulture Research Institutewere analyzed for determination of antioxidant activities, total phenolics, anthocyanins, external colour, polyphenoloxidase activities, sugar and acidity. The lowest antioxidant activity (percentage of inhibition on peroxidation in linoleic acid system; ˘ ¸ AA) was determined in Tekirdag cekirdeksiz extracts as 87.58% and the highest AA was in Mourvedre (93.78%). Total phenolic content (TP) variedfrom 817 to 3062 mg/ml GAE in the same varieties, respectively. The total anthocyanin (TA) content ranged from 40.3 to 990.8 mg/l fresh ˘ weight. The lowest PPO activity was found in Bogazkere and the highest was in Kalecik karası. The total sugar content in the analyzed varieties varied between 13.29 and 24.46%. There was stronger correlation between AA and TP than AA and TA. # 2006 Elsevier B.V.All rights reserved.
Keywords: Antioxidant activity; Total phenolic; Anthocyanin; Polyphenoloxidase activity; Red grape varieties; Correlations

1. Introduction The grape is one of the most important fruit commodities as an economic plant with good agricultural characteristics. It is mainly processed to juice, wine or raisins and cultivated largely for the wine industry. The grape is becomingincreasingly popular as a fruit and is a significant source of nutritional antioxidants, such as polyphenols, anthocyanins as well as biologically active dietary components. According to Macheix et al. (1990) grapes are among the fruits containing the highest content of phenolic substances. The phenolic compounds occurring in red wine, grapes and grape juice include flavonoids, notably flavan-3-ols(catechins and procyanidins), anthocyanins and flavonols as well as nonflavonoid compounds such as hydroxycinnamic acids, hydroxybenzoic acids (Singleton, 1982; Macheix et al., 1990; Palomino et al., 2000). Percival (1998) explained that antioxidants are our first line of defense against free radical damage, and are critical for maintaining optimum health and well-being. The need for antioxidantsbecomes even more critical with increased

* Tel.: +90 282 293 14 38; fax: +90 282 293 14 60. E-mail address: horak@trakya.edu.tr. 0304-4238/$ – see front matter # 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.scienta.2006.10.019

exposure to free radicals. The antioxidant activity of wine, fresh grapes or grape juice is thus attributable to different types of phenolic constituents, and theantioxidant effectiveness on LDL lipid peroxidation is correlated to distinct types of phenolics and their relative concentrations in various samples (Frankel et al., 1995; Meyer et al., 1997; Ghiselli et al., 1998; Teissedre and Landrault, 2000). According to many authors, antioxidant activity of fruits results mainly from phenolics, particularly flavonoids. Flavonoids have been demonstrated tohave anti-inflammatory, antiallergenic, anti-viral, anti-aging and anti-carcinogenic activity (Kuhnau, 1976; Havsteen, 1983). Anthocyanins are natural pigments, responsible for a wide range of colours in grape and red wines. Wang et al. (1997) reported that anthocyanins contribute greatly to the antioxidant properties of certain colourful foods, such as grapes and cranberries and cyanidin is the...