山西乡宁葡萄酒采收期酚类物质对葡萄酒的影响

山西乡宁地区葡萄采收时间对葡萄及葡萄酒酚类物质与抗氧化活性影响

EFFECT OF HARVEST TIME ON PHENOLIC CONTENTS AND ANTIOXIDANT PROPERTIES OF GRAPE AND WINES IN

XIANGNING COUNTY,SHANXI PROVINCE

作者：孟江飞　　导师：房玉林

西北农林科技大学　　发酵工程2011届硕士

摘　要

山西省乡宁县为中国一个新兴的葡萄与葡萄酒产区，其独特的气候条件受到国内外葡萄酒行业人士的关注。该地区葡萄酒产业刚刚起步，一切仍在完善与探索之中。本研究旨在为当地酿酒葡萄最佳采收期的确定提供研究基础。本研究以山西省乡宁县赤霞珠与梅尔诺两个葡萄品种为实验材料，按时间段进行6次采样，同时将各时期采摘的葡萄用相同的酿造工艺酿成酒精度为12度的干型葡萄酒，并对其基本理化成分进行分析。另外对各采收期葡萄果皮、种子以及葡萄酒中的酚类物质（总酚，总类黄酮，总黄烷醇及总花色苷）与抗氧化活性（DPPH清除力，铜离子还原力，铁氰化钾还原力，羟自由基清除力及金属螯合力）进行评估。最后使用主成分分析法对葡萄与葡萄酒中基本理化成分、酚类物质含量及抗氧化活性进行综合评价，从而确定这两个葡萄品种在山西省乡宁县地区的最佳采收期。实验过程中发现该地区葡萄有皱缩（Berry shrivel）现象，这种现象在国际上已经引起了极大的关注，本实验也对其进行了研究。试验取得以下主要结果：

（1）使用1%盐酸酸化的80%甲醇溶液分别提取两个品种果皮及种子中的酚类物质，分别使用福临——肖卡法、亚硝酸盐—氯化铝法、p-DMACA法、pH示差法测定了果皮与种子中的总酚、类黄酮、总黄烷醇及总花色苷含量。同时使用DPPH清除力、铜离子还原力、铁氰化钾还原力、羟自由基清除力及金属螯合力五种方法来测定葡萄果实的抗氧化能力，再结合葡萄果实的基本理化成分，利用主成分分析法对各采收期的葡萄果实进行综合评价。结果表明：赤霞珠果实综合品质排名依次为CS 9-16，CS 9-21，CS 9-26，CS 10-15，CS 9-30，CS 10-6；梅尔诺果实综合品质排名依次为ML 10-6，ML 10-9，ML 9-30，ML 9-26，ML 9-21，ML 9-16。

（2）分别使用福林—肖卡法、亚硝酸盐-氯化铝法、p-DMACA法、pH示差法测定了不同采收期葡萄酒中总酚、类黄酮、总黄烷醇以及总花色苷含量。同时使用DPPH清除力、铜离子还原力、铁氰化钾还原力、羟自由基清除力四种抗氧化方法，来反映各采收期葡萄酒的抗氧化能力。最后结合葡萄酒的基本理化成分，利用主成分分析法对两品种各采收期的葡萄酒进行综合评价。结果表明：赤霞珠葡萄酒综合品质排名为：CS 9-16，CS 9-21，CS 10-6，CS 10-15，CS 9-30，CS 9-26；梅尔诺葡萄酒综合品质排名为：ML 10-9，ML 10-6，ML 9-16，ML 9-30，ML 9-21，ML 9-26。

（3）赤霞珠为晚熟品种，但研究结果显示，其葡萄与葡萄酒综合评价值均在9月16日最高。可能在葡萄不能完全成熟情况下，较早采收对赤霞珠葡萄酒更有利。梅尔诺为中晚熟品种，对其果实与葡萄酒的研究表明，葡萄果实在10月6日综合评价值最高，葡萄酒在10月9日评价值最高，所以该品种在山西乡宁县地区的最佳采收期应在10月6日至9日左右。

（4）浆果皱缩（Berry shrivel）是在转色期以后发生的一种浆果生理失调现象。目前该现象已在世界范围内发现并会影响葡萄与葡萄酒的质量。但是，到目前为止，这种现象在中国未见报道。本实验的目的在于研究山西乡宁县葡萄在果实皱缩期间其酚类物质及抗氧化活性变化。研究结果显示：皱缩会导致果实基本成分诸如糖、酸浓度的增加；适度皱缩有益于葡萄中酚类物质浓度及抗氧化活性的提高，但是深度皱缩会使抗氧化能力显著降低。另外，由于所受光照程度不同，皱缩对阴面葡萄与阳面葡萄中酚类物质、抗氧化活性的影响不同。

关键词　采收期　赤霞珠　梅尔诺　酚类物质　抗氧化能力

Abstract

The Xiangning County,Shanxi Province is a nascent producing area for grape and wine,and being focused on by a great number of grape and wine researchers due to its unique condition in geography and climate. However,its wine industry is still at an initial stage and everything is being fumbling for. The purpose of this study was to provide academic guidance for local wine production. In this research,two genotypes of grape varieties,Cabernet Sauvignon (sampling at Sep. 16,21,26 and 30,Oct. 6 and 15,2010) and Merlot (sampling at Sep. 16,21,26 and 30,Oct. 6 and 9,2010) were chosen as experimental materials,and used to make dry wine (about 12%) through the same technology. In addition,the physicochemical properties of these wines were detected. Then,the grape skins,seeds and wine from these two varieties harvested at different time were studied for their phenolic compounds,such as total phenolics,total flavonoid,total flavanol and total anthocyanin,and antioxidant activity using several assays based on different characteristics,such as DPPH scavenging capacity,cupric reducing power,Potassium ferricyanide reducing activity,hydroxyl radical scavenging activity and metal chelating capacity. And optimal harvest time about the two varieties in Xiangning County was identified through analyzing all these indicators using the principal component analysis. Moreover,it was found that the berry shrivel (BS) phenomenon,which has aroused great concern,also occurred in Xiangning County. In this research,the BS was studied for its impact on phenolics and antioxidant capacity of grape berries. The primary conclusions were as follows:

(1) Phenolic compounds were extracted from grape skins and seeds using acidified methanol (1 M HCl in 80% methanol),respectively. The extracts solution was used to analyze total phenolics,total flavonoid,total flavanol and total anthocyanin,and antioxidant activity using several assays mentioned above. Then combined with basic physicochemical composition,we applied the method of the principal component analysis to make comprehensive evaluation of the quality of each grape sample from different harvest time. The results show that grape quality was in the decreasing order as follows: Cabernet Sauvigon,CS 9-16，CS 9-21，CS 9-26，CS 10-15，CS 9-30，CS 10-6;Merlot,ML 10-6，ML 10-9，ML 9-30，ML 9-26，ML 9-21，ML 9-16.

(2) All wine samples were used to analyze phenolic compounds and antioxidant activity using several assays mentioned above. Then combined with basic physicochemical composition in each wine sample,we applied the method of the principal component analysis to make comprehensive evaluation of the quality of each wine sample from different harvest time. The results show that wine quality was in the decreasing order as follows: Cabernet Sauvigon,CS 9-16，CS 9-21，CS 10-6，CS 10-15，CS 9-30，CS 9-26;Merlot,ML 10-9，ML 10-6，ML 9-16，ML 9-30，ML 9-21，ML 9-26.

(3) Cabernet Sauvignon is a late-mature cultivars,however,the optimal harvest time for Cabernet Sauvignon is about Sep. 16 according with the study on grape and wine mentioned above. It is more beneficial to wine quality that Cabernet Sauvignon was harvested earlier when it is impossible to reach complete maturity. Merlot is middle-late mature varieties,and the optimal harvest time for Merlot is about Oct. 6～9 according with the study on grape and wine mentioned above.

(4) Berry shrivel (BS),a berry development disorder,appears soon after veraison. It occurs worldwide and affects the quality of grape berries and wine. However,it had not been reported in China until recently. This study aimed to investigate the changes in berry composition and antioxidant activity of Cabernet Sauvignon grapes from Xiangning Valley,Shanxi Province,China,during BS. Shrinkage contributed to an increase in the concentration of basic grape ingredients such as sugar and acid. An appropriate degree of shrinkage was apparently helpful in improving the phenolic content and increasing the antioxidant activity,but the berries that continued to shrivel showed a low antioxidant activity. Further,the results indicated distinct differences between the berries harvested from the southern side of the canopy and those harvested from the northern side,presumably due to variations in sunlight exposure.

Key words　Harvest time　Cabernet Sauvignon　Merlot　Phenolic compounds　Antioxidant activity