Susan E. Ebeler

The present and future of the international wine industry

Wine production is both art and science, a blend of individual creativity and innovative technology. But wine production is also business, with economic factors driving manufacturing practices. To be successful in the modern marketplace, a winemaker must integrate the artistic and economic aspects of wine production, and possess a solid understanding of the intrinsic and extrinsic factors that underlie purchase motivation.

ANALYTICAL CHEMISTRY: UNLOCKING THE SECRETS OF WINE FLAVOR

Knowledge of wine flavor has paralleled developments in analytical chemistry. In the 19th century, analytical methods focused on the determination of major wine components such as ethanol, organic acids, and sugars. The development of chromatographic techniques in the early 1900s and particularly development of gas chromatography in the early 1950s ushered in a new era of discovery for analytical chemists. Currently, more than 1300 volatile compounds have been identified in alcoholic beverages and new compounds continue to be discovered. At the beginning of the 21st century, the focus is beginning to shift away from identification and quantification of new flavor compounds and toward developing dynamic analytical techniques that can model the complex relationships between volatile composition and sensory properties. In addition, rapid, readily automated techniques that can be used to optimize agricultural (viticultural) practices and processing or aging conditions are being evaluated and developed. Primarily, this review provides a discussion of the major volatile compounds involved in wine flavor and an overview of the analytical techniques that have been instrumental in investigating the flavor of wines made from Vitis vinifera grapes. Secondarily, a brief discussion of the flavor contributions and analysis of nonvolatiles is also presented.

Postharvest life and flavor quality of three strawberry cultivars kept at 5 °C in air or air+20 kPa CO2

The postharvest life and flavor quality of three strawberry (Fragaria x ananassa D.) cultivars (Aromas, Diamante and Selva) kept at 5 8C in air or air� /20 kPa CO2 for up to 15 days were investigated. ‘Diamante’ and ‘Selva’ had better flavor quality than ‘Aromas’ strawberries, as indicated by levels of titratable acidity and total soluble solids, organic acids, sugars and some aroma compounds and by a consumer preference test. Flesh firmness was maintained in ‘Aromas’ and increased in ‘Diamante’ and ‘Selva’ strawberries during storage at 5 8C in both air and air� /20 kPa CO2. Fruit color was not affected by CO2 treatments. The postharvest life based on appearance was 7, 9 and 9 days for ‘Aromas’, ‘Diamante’ and ‘Selva’ fruits stored in air and it was extended by 2, 2 and 4 days, respectively, by the CO2enriched atmosphere. However, the level and proportion of flavor components (sugars, organic acids, aroma compounds) and fermentative metabolites, as well as the results of sensory evaluations, indicated that the flavor life was shorter than postharvest life based on appearance in ‘Aromas’ fruit stored in air (5 vs. 7 days) and in CO2-stored ‘Aromas’ (7 vs. 9 days) and ‘Selva’ (11 vs. 13 days) fruit. ‘Selva’ and ‘Diamante’ strawberries retained their flavor quality during storage at 5 8C in air for 9 days and CO2-stored ‘Diamante’ fruit for 11 days. # 2002 Elsevier Science B.V. All rights reserved.

Comparative analysis of topoisomerase IB inhibition and DNA intercalation by flavonoids and similar compounds: structural determinates of activity

Flavonoids and other polyphenolic compounds have been shown to inhibit human topoisomerase IB (topo I) through both inhibition of relaxation activity and through stabilization of the cleavable complex (poisoning). Some flavonoids have also been shown to intercalate DNA, and an association of topoisomerase inhibition with intercalation has been noted. We surveyed 34 polyphenolic compounds, primarily flavonoid glycones and aglycones, for their ability to inhibit topo I and to intercalate DNA using an in vitro gel electrophoresis method. We show that the most potent topo I poisons are the flavones and flavonols, and that these generally, but not always, are found to be DNA intercalators. There was no clear correlation, however, of topo-I-poisoning activity with the degree of DNA unwinding. Surprisingly, both DNA intercalation and topo I poisoning were shown to occur with some flavone glycones, including the C-glycosylflavone orientin. Inhibition of relaxation activity by flavonoids was found to be difficult to quantify and was most likely to be due to non-specific inhibition through flavonoid aggregation. As part of a structure-activity analysis, we also investigated the acid-base chemistry of flavonoids and determined that many flavonoids show acid-base activity with a pK(a) in the physiological pH region. For this reason, subtle pH changes can have significant effects on solution activity of flavonoids and their concomitant biological activity. In addition, these effects may be complicated by pH-dependent aggregation and oxidative degradation. Finally, we develop a simple model for the intercalation of flavonoids into DNA and discuss possible consequences of intercalation and topoisomerase inhibition on a number of cellular processes.

Analysis of 2,4,6-trichloroanisole in wines using solid-phase microextraction coupled to gas chromatography-mass spectrometry.

Cork taint in wine is a serious problem which is exacerbated by the difficulty of its assessment. Current analytical procedures are costly, time consuming and require the use of large amounts of solvents. We developed and evaluated a rapid method for the detection of the cork taint compound, 2,4,6-trichloroanisole (TCA), in wine samples. The method employs solid-phase microextraction, a solventless, automated sampling procedure, coupled to GC-MS-selected ion monitoring analysis. Quantification is enabled by a fully deuterated [2H5]TCA analog used as an internal standard. Accuracy (+/- 8%), precision (R.S.D. 5-13%), and limit of quantification (5 ng/l) are comparable to existing methods.

Interactions between Wine Volatile Compounds and Grape and Wine Matrix Components Influence Aroma Compound Headspace Partitioning

A full-factorial design was used to assess the matrix effects of ethanol, glucose, glycerol, catechin, and proline on the volatile partitioning of 20 volatile compounds considered to play a role in wine aroma. Analysis of variance showed that the two-way interactions of ethanol and glucose, ethanol and glycerol, and glycerol and catechin significantly influenced headspace partitioning of volatiles. Experiments were conducted to observe the effect of varied ethanol and glucose concentrations on headspace partitioning of a constant concentration of volatiles. Analysis of variance and linear regression analysis showed that the presence of glucose increased the concentration of volatiles in the headspace, whereas increasing ethanol concentration was negatively correlated with headspace partitioning of volatiles. A subsequent study assessed the effect of diluting white and red wines with water and ethanol. It was again observed that increased ethanol concentration significantly reduced the relative abundance of volatile compounds in the sample headspace. This study investigates some of the complex matrix interactions of the major components of grape and wine that influence volatile compound headspace partitioning. The magnitude of each matrix-volatile interaction was ethanol > glucose > glycerol > catechin, whereas proline showed no apparent interaction. The results clearly identify that increasing ethanol concentrations significantly reduce the headspace concentration of volatile aroma compounds, which may contribute to explaining recent sensory research observations that indicate ethanol can suppress the fruit aroma attributes in wine.

Origins of Grape and Wine Aroma. Part 1. Chemical Components and Viticultural Impacts

Wine is an ancient beverage and has been prized throughout time for its unique and pleasing flavor. Wine flavor arises from a mixture of hundreds of chemical components interacting with our sense organs, producing a neural response that is processed in the brain and resulting in a psychophysical percept that we readily describe as “wine.” The chemical components of wine are derived from multiple sources; during fermentation grape flavor components are extracted into the wine and new compounds are formed by numerous chemical and biochemical processes. In this review we discuss the various classes of chemical compounds in grapes and wines and the chemical and biochemical processes that influence their formation and concentrations. The overall aim is to highlight the current state of knowledge in the area of grape and wine aroma chemistry.

Quantitative analysis by gas chromatography of volatile carbonyl compounds in expired air from mice and human

Formaldehyde, acetaldehyde and acetone expired from tumor-bearing transgenic mice and formaldehyde exhaled from breast cancer patients were analyzed using gas chromatography. The tumor-bearing mice expired significantly more formaldehyde per unit metabolic size (1.43-2.98 micromol) than did control mice (0.77-1.01 micromol). There was no detectable difference in the levels of expired acetaldehyde and acetone between the two groups of mice. The exhaled formaldehyde levels from three women with breast cancer and from three healthy women were satisfactorily determined using the method developed in this study. The results suggest that these carbonyl compounds may be used as a biomarker.

Wine Chemistry and Flavor: Looking into the Crystal Glass

Over the past century, advances in analytical chemistry have played a significant role in understanding wine chemistry and flavor. Whereas the focus in the 19th and early 20th centuries was on determining major components (ethanol, organic acids, sugars) and detecting fraud, more recently the emphasis has been on quantifying trace compounds including those that may be related to varietal flavors. In addition, over the past 15 years, applications of combined analytical and sensory techniques (e.g., gas chromatography-olfactometry) have improved the ability to relate chemical composition to sensory properties, whether identifying impact compounds or elucidating matrix effects. Many challenges remain, however. This paper discusses some of the recent research aimed at understanding how viticultural and enological practices influence grape and wine volatiles. In addition, the challenges in linking composition to sensory properties will also be reviewed. Finally, future advances in linking grape, yeast, and human genomics to wine chemistry and flavor will be briefly discussed.

Effect of Dietary Constituents With Chemopreventive Potential on Adduct Formation of a Low Dose of the Heterocyclic Amines PhIP and IQ and Phase II Hepatic Enzymes

We conducted a study to evaluate dietary chemopreventive strategies to reduce genotoxic effects of the carcinogens 2-amino-1-methyl-6-phenyl-imidazo[4,5-b]pyridine (PhIP) and 2-amino-3-methylimidazo[4,5-f]quinoline (IQ). PhIP and IQ are heterocyclic amines (HCAs) that are found in cooked meat and may be risk factors for cancer. Typical chemoprevention studies have used carcinogen doses many thousand-fold higher than usual human daily intake. Therefore, we administered a low dose of [14C] PhIPand [3H] IQand utilized accelerator mass spectrometry to quantify PhIP adducts in the liver, colon, prostate, and blood plasma and IQadducts in the liver and blood plasma with high sensitivity. Diets supplemented with phenethylisothiocyanate (PEITC), genistein, chlorophyllin, or lycopene were evaluated for their ability to decrease adduct formation of [14C] PhIPand [3H] IQin rats. We also examined the effect of treatments on the activity of the phase II detoxification enzymes glutathione S-transferase (GST), UDP-glucuronyltransferase (UGT), phenol sulfotransferase (SULT) and quinone reductase (QR). PEITC and chlorophyllin significantly decreased PhIP-DNA adduct levels in all tissues examined, which was reflected by similar changes in PhIP binding to albumin in the blood. In contrast, genistein and lycopene tended to increase PhIP adduct levels. The treatments did not significantly alter the level of IQ-DNA or -protein adducts in the liver.With the exception of lycopene, the treatments had some effect on the activity of one or more hepatic phase II detoxification enzymes. We conclude that PEITC and chlorophyllin are protective of PhIP-induced genotoxicity after a low exposure dose of carcinogen, possibly through modification of HCA metabolism.