Relationship Between Antioxidant Capacity, Proanthocyanidin and Anthocyanin Content During Grape Maturation of Touriga Nacional and Tinta Roriz Grape Varieties

Abstract

To investigate antioxidant capacity in seeds and skins during grape maturation and its relationship with anthocyanin and proanthocyanidin content, two Portuguese red grape varieties, Touriga Nacional and Tinta Roriz (Vitis vinifera L.) were studied. Two analytical methods were used for antioxidant capacity analysis: the DPPH and ABTS methods. Proanthocyanidins from seeds and skins were separated into monomers, oligomers and polymers, while 13 individual anthocyanins from the skins were also evaluated by HPLC. For both grape varieties studied, antioxidant capacity from the skins and seeds was characterised during grape maturation by a general decrease, mainly in the first weeks after véraison, followed by stabilisation and a slight increase in the values in the last three weeks of ripening. A similar tendency was observed for the amount of all the different proanthocyanidin fractions quantified. Our results also showed that seeds are an important source of proanthocyanidins with respect to the grape berry skins. Seeds were also the grape berry fraction with the highest antioxidant capacity when compared to the antioxidant capacity content of the skins. For the 13 individual monomeric anthocyanins quantified during grape maturation, evolution was generally characterised by a continuous increase in the values. However, for some of the individual anthocyanins, the continuous increase was followed by stabilisation or a decrease in the values in the last weeks of ripening. Finally, there was a positive relationship between the different proanthocyanidin fractions and antioxidant capacity of both grape varieties studied; while a negative relationship during grape maturation was obtained for individual anthocyanins. INTRODUCTIONGrapes have long been appreciated for their rich content of phenolic compounds such as gallic acid, catechin, anthocyanins and resveratrol, and a wide variety of procyanidins (Cheynier & Rigaud, 1986;Ricardo-da-Silva et al., 1992a;Jordão et al., 1998aJordão et al., , 1998bKennedy et al., 2000aKennedy et al., , 2001 Jordão et al., 2001a,b;Sun et al., 2001). Phenolic compounds can be classified into two groups: flavonoids and nonflavonoids. The main C 6 -C 3 -C 6 flavonoids in wine include conjugates of the flavonols, quercetin and myricetin; flavin-3-ols (+)-catechin and (-)-epicatechin; and anthocyanins. The nonflavonoids incorporate the C 6 -C 1 hydroxy-benzoic acids, and gallic and ellagic acids; the C 6 -C 3 hydroxycinnamates caffeic, caftaric and p-coumaric acids, and the C 6 -C 2 -C 6 stilbenes trans-resveratrol, cis-resveratrol, and trans-resveratrol glucoside.In the grape berry, flavonoids such as anthocyanins are located mainly in the skins (Jordão et al., 1998a), while the flavan-3-ols (catechins and proanthocyanidins) are present in the skins, seeds and stems (Ribéreau-Gayon, 1972; Ricardoda-Silva et al., 1992b;Fuleki & Ricardo-da-Silva, 1997;Kennedy et al., 2000aKennedy et al., , 2000b Jordão et al., 2001a,b;Sun et al., 2001).Anthocyanin accumulation in the vacuoles of the skin begins ...

Phenolic composition of Nebbiolo grape (Vitis vinifera L.) from Piedmont: characterization during ripening of grapes selected in different geographic areas and comparison with Uva Rara and Vespolina cv.

“…Our results are consistent with literature data reporting anthocyanins reach the maximum content around the harvest period [35]. Nevertheless, several works highlighted that anthocyanin concentration may slightly decrease in the last weeks of ripening or during over-maturation [6,7]. Vian et al, which studied the anthocyanin composition of Syrah grapes, observed that the maximum anthocyanin content is reached about 30 days after veraison [36].…”

“…In a general way, the antioxidant activity remained constant during grape development, having observed a significant increase from T1 to T3 only in the case of NBTCr sample. Previously, Jordão and Correia [6] observed a general decrease in both skins and seeds antioxidant activity in the early stages of maturation, followed by the stabilization of the values at the last weeks of ripening. Bordiga et al [9] evaluated the radical scavenging activity of polymeric proanthocyanidins from seeds and skins of Nebbiolo and other five grape cultivars, but did not observe any significant evolution of the antiradical values during ripening.…”

“…As observed for anthocyanins, Vespolina demonstrated the highest tannins content; on the contrary, the lowest values were observed for Uva Rara. Several authors studied tannins concentration in grape skins and/ or seeds during ripening, using different quantification methods (both extraction and analytical protocols) and obtaining different patterns of variation [6,9,24,30,31]. The content is much higher in seeds than in skin [32], but it was also observed that skin tannins are more readily extractable than those from seeds; the tannin extractability from grapes during the winemaking process is particularly important because of the influence on the sensory properties of the final product (astringency and bitterness).…”

“…In the case of anthocyanins, they appear during veraison and reach a maximum concentration during ripening [5], even if the anthocyanin concentration may slightly decrease in the last weeks of ripening or during over-maturation [6,7]. Previous papers reported the evolution and concentration of phenolic compounds in both seeds and/or skins of different grape berry varieties during ripening, evidencing a significant varietal effect [8,9].…”

Antioxidant Capacity of Anthocyanin Pigments

“…Anthocyanins are the pigments responsible for the attractive colour of red wine and are one of the main flavonolic compounds with antioxidant activity, which is why red wine has a greater antioxidant activity than white wine [307][308][309][310]. Its antioxidant capacity can be up to 10 times stronger than that of white wine [205].…”