Characterization of Bioactive Compounds in Lees from New Zealand Wines with Different Vinification Backgrounds

Abstract

Wine lees are one of the main by-products produced during winemaking. Little is known about the effect of the vinification technique on the phenolic compounds and the biological activity of wine lees extracts. Wine lees collected at varying vinification sources of two grape varieties, Riesling (RL) and Pinot Noir (PN), were analyzed for total phenolic content (TPC), tannin content (TTC), their anthocyanin and phenolic profile, and the antioxidant and antimicrobial activities of their extracts. The results showed a low TPC and TTC in RL lees, which could be attributed to the varietal characteristic of RL grapes and to less skin contact during vinification. Vinification techniques modified the composition of the phenolic compounds in the lees. The results showed a good linear relationship between the antioxidant activities and the TPC and TTC, indicating that PN lees were better sources of phenolics and antioxidant activity than RL lees. The antimicrobial activity of wine lees was related to the phenolic composition rather than the quantity of total phenolics. Knowing the grape and wine processing conditions can provide some insights into the potential composition of wine lees and, hence, determine the potential economic use of the by-product.

Studies on the Effect of Oxidation on Bioactivity of Phenolics and Wine Lees Extracts

“…For the oxidation of the fresh lees samples, 38.46 g of PN1 (13.0% DM), 61.35 g of PN2 (8.2% DM), 133.87 g of RL1 (22.4% DM) and 191 g of RL2 (15.7% DM), were weighed and then topped up to 200 g by adding 12% ethanol followed by adding 192 mL 260 mM TRIS buffer (pH 7.5). The reason for weighing the wine lees above was to ensure there was enough wine lees and phenolic compounds for sample extraction and chemical analyses [ 13 ]. Preliminary studies indicated that the oxidation of the lees was found to be optimal when HRP was 500 U.…”

“…The reaction was carried out in Schott bottles. The mixture was mixed and left at room temperature for 24 h. At the end of the oxidation time, the wine lees extracts were extracted as described by Ye et al [ 13 ] and Mercurio et al [ 15 ]. The freeze-dried lees samples (Virtis Freezemobile 12SL, New York, NY, USA; at a pressure of 0.5 mbar) underwent a two-step extraction using acidified 50% ethanol ( v / v containing 1% v / v HCl) ( Table 2 ).…”

“…The method is based on the acid-catalyzed cleavage of proanthocyanidin in the presence of excess phloroglucinol followed by chromatographic analysis of the reaction products. The lees samples were prepared according to Ye et al [ 13 ]. The freeze-dried lees was extracted using 50% ethanol ( v / v ) followed by centrifugation at 3000× g for 5 min using a Megafuge 1.0 with a Siehe rotor (Kendro Laboratory Products, Hamburg, Germany).…”

“…Flavan-3-ols are abundant in wine by-products [ 2 ]. The majority of studies that investigated wine wastes focus on grape pomace, skin and seeds [ 1 , 2 , 3 , 4 , 5 , 6 ], and little attention has been paid to the wine lees [ 12 , 13 ]. Ye et al [ 12 , 13 ] characterized wine lees from different vinification backgrounds and reported that flavan-3-ols were the primary flavonoids in the PN lees; and gallic acid (0.5–2.2 mg/g DM extract) was the predominant non-flavonoid.…”

“…The majority of studies that investigated wine wastes focus on grape pomace, skin and seeds [ 1 , 2 , 3 , 4 , 5 , 6 ], and little attention has been paid to the wine lees [ 12 , 13 ]. Ye et al [ 12 , 13 ] characterized wine lees from different vinification backgrounds and reported that flavan-3-ols were the primary flavonoids in the PN lees; and gallic acid (0.5–2.2 mg/g DM extract) was the predominant non-flavonoid. The concentrations of catechin, epicatechin and total procyanidins in the PN lees were 0.4 to 8.0 mg/g DM extract, 0.9–5.8 mg/g DM extract, and 1.4–4.8 mg/g DM extract, respectively.…”