Calag Archive

The culture of grapes and the making and aging of wine are often incorrectly visualized as ancient practices that have not changed and cannot change much. True, grapes have “always” been grown and converted to fermented fluid, and certain practices are fundamental to keeping it wine and not vinegar. Grape growing and winemaking were two of the more technologically advanced processes from ancient times to the dawn of the Scientific Revolution by the mid-1800s. Nevertheless, within the past century every operation in winemaking or viticulture has become either highly modified or at least much better understood and managed. Many new steps or whole techniques leading to new types of wine have been introduced. New varieties of grapes have been developed and vineyard management made much more rational and efficient.

Quality in any wine is a function of the potential quality in the grape and the skill of the enologist in converting that grape to wine. The first control of ultimate wine quality starts with analyses of the grapes in the vineyard, where two attributes are of primary importance. To be palatably balanced—that is, not thin or overly alcoholic—the wine must be made from grapes containing the appropriate concentration of natural sugars. Too little sugar results in watery, thin, and unpalatable wines. Too much alcohol results from grapes left on the vine until they are overripe; these wines, perhaps suitable as dessert accompaniments, are simply too alcoholic to be used with meals.

Over the past 100 years the art of sensory evaluation of wines has been advanced to a science, in large part through research performed at the University of California. Initially, sensory evaluation was a necessary but informal and perfunctory part of assessing wine quality. However, even as an unrefined observational tool, it contributed to early grape and wine research.

The current problems of the California wine industry all have parallels in the industry's earlier days. Its history is a fabric of high and low profits, overplanting and underplanting, surplus and shortage, and ascending and descending preferences. The industry has become robust and exceedingly complex but has never really resolved the problem of the profitable coordination of grape production and wine sales.

It can be said that wine microbiology began about 100 years ago, if we think of it as being concerned mainly with alcoholic fermentation and selection of yeasts, malo-lactic fermentation and the bacteria involved, and problems with microbiological spoilage. Louis Pasteur's first edition of Etudes sur le Vin was published in 1866, and in 1889 Kulisch presented the first evidence that malo-lactic fermentation was microbiological. However, the major contributions by the University of California in wine microbiology did not begin until early in this century.

It rained hard and long during the winter and spring of 1884 in Anaheim…and those extraordinary rains turned out to be harbingers of the first recorded serious disease epidemic in California vineyards. A new and mysterious malady of the vines, later to be known as Pierce's disease, dealt damaging blows to the grape industry established by German settlers around the little town southeast of Los Angeles, and local wineries had to close down as more than 35,000 acres of vines disappeared over the following decade.

Grape plants live for many years, and we might say, if we consider vegetative propagation, that they live for centuries. Vegetative propagation, which perpetuates the mother plant by cuttings or buds, is important for maintaining trueness of grape cultivars to type, because perennial woody species do not breed true from seed as is the case with annual crops.

It is seldom that some measurable wine quality attribute cannot be correlated with a chemical composition change. Sometimes, chemists' analytical tools are not precise enough to detect the chemical changes. Some vineyard treatments and practices that cause noticeable variations in wine are grape variety, climate, crop level, maturity, rootstock, irrigation, chemical vineyard sprays and dusts, harvesting techniques, and transport to the winery. Other indirect treatments may also alter the chemical makeup of the fruit and possibly cause quality changes.

The United States leads the world in raisin production, accounting for nearly 40 percent of the global crop. All U. S. raisins are produced in California, where the Thompson Seedless variety, harvested on 100,000 acres annually, constitutes 90 percent of the raisin production. This variety is distinctive, because it is dried in the sun between vineyard rows without treatment.

Essentially all the controlled-climate research with grapevines in California has been done in the past 20 years. A stationary and a rotating phytotron unit became available in 1961 and 1965, respectively, for plant research at the University of California, Davis. The phytotron rooms precisely control day and night temperatures as well as humidity. Solar radiation is the source of light and can be controlled to some extent with shade fabrics, filters, and the like. More recently, large temperature-controlled water baths have been added to the rooms so that root and air temperatures can be varied independently of each other and their interaction studied.

The first crosses to produce new grape varieties were made in 1931, 2 years after the University began the breeding project. During the past 50 years, over 300,000 vines of known parentage have been grown to the fruiting stage. The first new varieties were introduced in 1946.

From the inception of commercial vineyards in California, insects and mites have been a problem. The abundance of pests may be attributed to the fact that most grape pests were native to America, and the extensive plantings and mild climate favored development of a considerable number of pests. Some of the insects have remained a problem in the vineyards to the present time, while other species have become less important. The introduced grape phylloxera, Daktulosphaira vitifoliae (Fitch), and the native grape leafhopper, Erythroneura elegantula Osb., were present in the early years of viticulture and are still considered major problems. Insects such as the sphinx moths, Pholus achemon (Drury) and Celerio lineata (Fabr.), and the western grape rootworm, Adoxus obscurus (Linn.), which previously caused considerable damage to vines, have become minor problems, whereas the omnivorous leaf roller, Platynota stultana Wlshm., the orange tortrix, Argyrotaenia citrana (Fernald), and the western grapeleaf skeletonizer, Harrisina brillians B. and McD., have become serious pests.

Since the 1920s, girdling of Thompson Seedless vines has been used to increase the size of the table grapes. Research on growth regulators started in 1949 when 31 different hormones were tested on Black Corinth and Thompson Seedless grapes. The two most promising regulators of the auxin type (a plant growth hormone regulating cell division) were 4-chlorophenoxyacetic acid (4-CPA) and benzothiazole-2-oxyacetic acid (BOA). For several years 4-CPA was used commercially, but it is no longer registered for use on grapes; BOA has never been used commercially.

Grapevines are propagated primarily by cuttings just as they have been for years. The use of seeds for propagation is not satisfactory, because the seedling does not resemble the parent vine. Work by F. T. Bioletti in the 1920s indicated that production of new vineyards was the same whether or not the original cuttings arose from vines that bore heavy crops or light crops. The difference was caused by the environment and was not inherited.

Brandy production in California began with the Spanish missionaries, who made brandy almost as soon as their first grape plantings started to bear fruit. Development of the industry in the San Joaquin Valley, however, did not occur until the late 1800s, and University of California contributions to brandy research really began after Prohibition ended.

In the wild, the grapevine is often supported at great heights by adjacent trees; the shoots cling to branches by means of tendrils and trail for considerable lengths. A favorable light environment is essential for annual growth, so lower or interior areas are characterized by rope-like “trunks,” devoid of leaves, extending from the ground upward to the canopies of trees. Not only is the fruit difficult to locate and harvest, it consists of a myriad of small straggly clusters. Productivity is erratic from year to year.

Grape growers have long used hedging or mowing to remove part of the wood on vines trained to cordons. This pre-pruning of superfluous one-year-old wood facilitates the work of the pruners, who then remove all but 10 to 20 spurs per vine selected for fruiting.

Table grapes (Vitis vinifera L.) are physiologically a relatively durable fruit. They have a low respiration rate and can therefore live a long time after harvest. However, they are extremely susceptible to decay, can be injured easily, and lose water readily. Modern technology has alleviated these problems so that table grapes can be sold most of the year and in most of the major world markets.

The early trellis systems for growing raisin and wine grapes were quite simple. For head-trained, spur-pruned vines, a single 2- by 2-inch split redwood stake or other wood was placed at each vine, and the vine was then trained to the stake. For cordon- or head-trained, cane-pruned vines, one or two wires were fastened to a 5-or 6-foot stake at each vine 34 to 48 inches from the ground and held taut by firmly set end posts. This type of trellis in California has withstood the test of time and is probably the most widely used for growing raisin and wine grapes; however, the trend now is to place the wires higher to facilitate mechanical harvesting.

Both spring and fall low temperature injury to vines is common in parts of California. Temperatures that cause winter kill of fully dormant vines—10° F (−12° C)—rarely occur in the grape-growing regions.