Temperature and storage effects on antioxidant activity of juice from red and white grapes

The effect of temperature and storage time on the phenolic composition and on the antioxidant activity of grape (Vitis vinifera L.) juices made using a red (Sangiovese, SG) and a white (Muscat of Alexandria, MA) variety was studied. Total phenolics, flavonoids, flavan‐3‐ols and hydroxycinnamoyl‐tartrates (HCT) were determined on grape extracts (GE) and juices. Total anthocyanins and anthocyanins composition were measured on GE. The antioxidant activity was assessed by means of two different in vitro tests: scavenging of the stable 2,2‐diphenyl‐1‐picrylhydrazyl radical and the inhibition of tyrosine nitration mediated by authentic peroxynitrite (ONOO^?). All the juices were analysed after 24 h and 2 weeks of storage by means of two‐way anova (factors being cultivar and temperature). Anthocyanins were not detected in MA extract, whereas in SG their content was 534 mg malvidin‐equivalent per 100 g of dry matter (d.m.) and malvidin derivatives (glycosylated and coumaroylated) were the most represented (respectively 169 and 41 malvidin‐equivalent per 100 g of d.m.). HCT content of the extracts was higher in SG (overall +33%). Also in grape juices, HCT were lower in MA and in this variety, the trans‐fertaric and cis‐coutaric acids were also undetectable. Cultivar effect proved to be highly significant, while no significant differences in the phenolic composition were observed for storage temperatures (4 and ?20 °C) and cultivar × temperature interaction. However, when statistical analysis was focused on each cultivar, MA was found to be more sensible to storage conditions and a significant reduction in total phenolics (?20%) and flavonoids (?53%) content and in the ONOO^? scavenging potential (?32%) was evident after 2 weeks at 4 °C (when compared with the same storage temperature after 24 h). On the contrary, SG juices did not show significant differences among the four storage treatments investigated. These results could be explained suggesting that anthocyanins presence in red grape plays a key role in juice stability.     

Biochemical characterization and process stability of polyphenoloxidase extracted from Victoria grape (Vitis vinifera ssp. Sativa)

Polyphenol oxidase (PPO) was isolated from Victoria grapes (Vitis vinifera ssp. Sativa) grown in South Africa and its biochemical characteristics were studied. Optimum pH and temperature for grape PPO activity were pH 5.0 and T = 25 °C with 10 mM catechol in McIlvaine buffer as substrate. PPO showed activity using the following substances: catechol, 4 methyl catechol, d, l-DOPA, (+) catechin and chlorogenic acid. K_m and V_max values were 52.6 ± 0.00436 mM and 653 ± 24.0 OD_400 nm/min in the case of 10 mM catechol as a substrate. Eight inhibitors were tested in this study and the most effective inhibitors were found to be ascorbic acid, l-cysteine and sodium metabisulfite. Kinetic studies showed that the thermal inactivation of Victoria grape PPO followed first-order kinetics, with an activation energy, E_a = 225 ± 13.5 of kJ/mol. Both in semipurified extract and in grape juice, PPO showed a pronounced high pressure stability.     

Protective effect of HV-P411, an herbal mixture,on carbon tetrachloride-induced liver fibrosis

This study was performed to examine the anti-fibrotic activity of HV-P411, an herbal mixture of seeds of Vitis vinifera, Schisandra chinensis and Taraxacum officinale extract, against carbon tetrachloride (CCl₄)-induced liver fibrosis. Hepatic fibrosis was induced by intraperitoneal injection of CCl₄ (0.5 ml/kg, twice weekly) for 8 weeks. Rats were treated orally with HV-P411 at 50, 100, 200, and 400 mg/kg once a day. After chronic exposure to CCl₄, the levels of hydroxyproline were markedly increased; these were significantly reduced by HV-P411 at all dose levels. The level of serum aminotransferases and lipid peroxidation were increased after the CCl₄ treatment, while reduced glutathione was decreased. These changes were attenuated by HV-P411. In addition, HV-P411 attenuated CCl₄-induced raised serum concentration of transforming growth factor-β1, and the levels of matrix metalloprotease-2 and tissue inhibitor of metalloprotease-1 mRNAs. Our results suggest that HV-P411 may prevent liver fibrosis by modulating fibrogenesis and fibrolysis.     

不同澄清方法对毛葡萄干型酒澄清效果的影响

采用明胶、皂土、蛋清3种澄清剂对毛葡萄干型酒进行澄清处理,结果表明,皂土可以明显提高酒的澄清度,降低总酚和可溶性蛋白质的含量,对酒有明显的脱色作用;明胶澄清效果次之,但可以有效降低单宁的含量;蛋清澄清效果一般.     

Volatile Components of Aqueous Liquid Smokes from Vitis viniferaL Shoots and Fagus sylvaticaL Wood

Vitis vinifera L shoots and Fagus sylvatica L wood were used to obtain aqueous smoke flavouring preparations. Both flavourings have a gold colour and pleasant odour. The flavour components of both samples are extracted with dichloromethane. The identification and quantitation of the components of the extracts are carried out by means of gas chromatography/mass spectrometry, and gas chromatography with flame ionisation detection. In both preparations carbonyl derivatives are in higher concentrations than phenol derivatives. Compounds that confer sweet, burnt and pungent flavours are in higher concentrations in the Vitis vinifera L shoots smoke flavouring, and compounds that give smoky flavours are in higher concentrations in the Fagus sylvatica L wood smoke flavouring. Ratios between the concentrations of the main components are proposed as parameters in order to characterise smoke and smoke flavourings, manufactured under specific conditions, from a specific wood. Finally, the yield of some components from a fixed amount of wood is also given.     

酿酒圆叶葡萄Noble和Carlos浆果挥发性成分分析

采用固相微萃取-气相色谱-质谱法(SPME-GC-MS)对酿酒圆叶葡萄品种Noble和Carlos浆果中挥发性成分进行鉴定,共鉴定出49种化合物,其中含有醇类、酯类、醛类、酮类等成分。Noble的挥发性成分总含量高于Carlos,2个品种中含量最高的成分都是(E)-2-甲基环戊醇和4-羟基-2-丁酮,二者在挥发性组分种类和含量上有一定的相似性。     

秋水仙素对刺葡萄萌发种子诱变的影响

本试验以刺葡萄已萌发的种子为试材,用不同浓度的秋水仙素(0、0.2%、0.3%、0.4%)处理不同时间(0、24h、36h、48h、60h),观察其诱变效果。结果表明,0.3%秋水仙素处理48h的诱变率在所有处理中为最高(36.8%),0.4%秋水仙素处理48h次之(33.3%),但二者存在极显著差异;0.4%秋水仙素的不同时间处理中,致死率随处理时间延长而增高,诱变植株数递减。     

刺葡萄皮色素色价测定及提取工艺研究

对湖南湘西刺葡萄及新疆的巨峰、红提两个葡萄品种的果皮进行了色价测定和对照，研究了刺葡萄皮色素的最佳提取工艺，结果表明：湘西刺葡萄皮的色价远高于对照品种，其色价是巨峰葡萄皮的21．75倍，红提葡萄皮的2．87倍；得出刺葡萄皮色素提取的最佳工艺条件为：以1．5mol／L的盐酸-95％乙醇（v/v=3：17）混合液为提取剂，提取时间为100min，提取温度为50℃，物料比为1：20（g／mL）。     

乙醇沉淀法提取葡萄多糖的研究

利用乙醇沉淀法提取葡萄多糖。研究表明此法提取葡萄多糖的最佳条件为:温度90℃,时间2h,料液体积比1∶2,次数为3。在提取液浓缩至原体积1/10的基础上用6倍体积的体积浓度95%乙醇进行沉淀。根据最佳提取工艺可使葡萄多糖的提取率达到99.9%。