Making Wine At Home Is Easy
Fermentation problems may arise from numerous sources, including deficiencies in the fruit and processing (Fig. 1). Difficulties may arise from a combination of factors and a variety of sources. It is often the impact of two or more conditions that cause a problem of greater significance than would be predicted by a single parameter alone. Once yeast fermentative vigor and vitality have diminished, revitalization may be difficult, if not impossible. Thus, winemakers must approach each winemaking step with as complete an understanding as possible. The following is a review of practical issues influencing fermentation.
Acetobacter is also a member of this group of gramnegative bacteria. This organism oxidizes alcohol to acetic acid. In making vinegar it is desirable however, in making wine it is the most important organism causing souring. Photobacterium can cause phosphorescence of meat and fish when incubated in suitable conditions. Halobacterium can grow in salt concentrations as high as 30 . It can produce pigments and spoil salty fish.
Most grape growing and winemaking decisions can influence FAN concentration. These include grape variety (14,41,42) and rootstock selection (43), climate, soil type (41,44), fertilization, and irrigation practices (45-47). Arginine and proline are the main amino acids in the fruit if the fertilization of the vine is low. With higher fertilization ( 3 g N plant), the amino acid amide glutamine increases dramatically (7). Therefore, the nitrogen available for yeast fermentation can be different in distinct wine growing regions of the world (7). Grape maturity is also an important issue influencing the concentration of FAN, in that underripe and overripe fruit may be low in FAN (23). Butzke (48) evaluated the yeast-assimilable nitrogen status of Vitis vinifera musts from the western United States in 1996. The concentration ranged from 40 to 559 mg N L, with an average of 213 mg N L. Primary amino acid content ranged from 29 to 370 mg N L (average, 135 mg N L) whereas ammonium (NH4+)...
Yeast-assimable nitrogenous compound deficiency in fermenting juice must is often corrected by the addition of assimilable nitrogen in the form of diammonium phosphate, or DAP (25.8 NH3, 74.2 PO4 w w), and or one of several commercially available nitrogen supplements. Commercial nitrogen supplements typically contain DAP (25-50 w w) in addition to more complex forms of nitrogen such as yeast extract, vitamins, and yeast hulls. Because the concentration of nitrogen compounds may vary with the product, it is recommended that winemakers consult the Material Safety Data Sheet (MSDS) for formulation information prior to use. Traditionally, winemakers employing nitrogen supplementation add the product along with yeasts at the start of fermentation. As noted, incorporation
F. (1996) Yeast and biochemistry of ethanol formation in Principles and Practices of Winemaking (Boulton, R. B., Singleton, V. L., Bisson, L. F., and Kunkee, R. E., eds.), Chapman & Hall, New York, p. 140. 20. Wahlstrom, V. L. and Fugelsang, K. C. (1988) Utilization of Yeast Hulls in Winemaking. Calif. Agric. Tech. Inst. Bull. 880103. California State University, Fresno.
Epicatechin by dry weight as well as other flavonoids and their glycosides (26). Thearubigins, highly colored catechin oxidation products and their gallate are of major significance in determining the quality and flavor of tea. Black tea as consumed by humans contains about 36 thearubigins, 3 theaflavins, 5 epigallocatechin gallate, and 1 gallic acid by dry weight. Due to the large amounts of these phenolic compounds in tea, heavy drinkers of tea in Japan may consume 1 g of epigallocatechin gallate per day per person. Dry whole cocoa beans contain approximately 12 to 18 phenolic compounds and the major compound is epicatechin (27). Phenolic compounds in roasted coffee beans are produced during thermal processing from carbohydrates, chlorogenic acid, and lignins. Phenolic compounds in beer that contribute to bitterness, astringency, harshness, and the formation of haze are catechin and epicatechin (approximately 40 mg L), gallocatechin (less than 15 mg L), and hydroxycoumarins and...
Fermentation is a gradual chemical change caused by the enzymes of some bacteria, moulds, and yeasts. Fermented beverages were ubiquitous in the earliest civilisations of Mesopotamia and Egypt. Not only did wine facilitate conviviality, it was usually more potable than the available water. Winemaking also served as a means of storing nutrients from grapes almost indefinitely. Similarly, Asian steppe dwellers turned mare's milk into koumiss, a fermented beverage that keeps much longer than unprocessed milk. Many cheeses with a long shelf life are produced by lactic-acid fermentation. One means of pickling, a very early form of food preservation, is to treat foods with vinegar, a liquid obtained by further fermenting alcoholic beverages.
Sulfites can effectively prevent or minimize nonenzymatic browning by forming stable hydroxysulfonates with car-bonyls and reducing sugars as mentioned in the previous section. In this respect, sulfites are widely used in wine making and in dehydrated fruits and vegetables to prevent the discoloration of the finished products (3,7,8). Sulfites can also inhibit some oxidative enzymes such as polyphen-oloxidase, ascorbate oxidase, lipogenase, and peroxidase (6) and therefore can retard the enzymatic browning resulting from polyphenoloxidase. In addition, sulfites can form stable hydroxysulfonates with browning intermediates such as quinones, and prevent further reaction to form browning pigment (6). Thus, sulfites are commonly used in fresh vegetables for salad bars (this application has been banned by USFDA), peeled and sliced potatoes, apple dice and other fruits used in bakery products, fresh mushroom for processing, and table grapes and fresh shrimp, where enzymatic browning...
The key to the success of single-culture fermentation is to provide the culture with a sterile substrate and environment with no contamination during the fermentation process. Examples include wine making, beer making, bread making, production of single-culture fermented dairy products, and vinegar production. In this type of fermentation the viable cells increase in a typical growth curve sequence of lag phase, log phase, stationary phase, and death phase. Primary metabolites (alcohol, acid, etc) are made during the log phase, and secondary products (antibiotics, toxins, etc) are made after the culture reaches the stationary phase.
Methods by which strains of the same species can be differentiated have been shown to be very important for yeast strain characterization. In winemaking, several studies have analyzed the diverse microflora of grapes and musts and several interesting methods have been developed (Figure 2).
Some studies have evaluated the phenolic contents in fruits at more than one ripening stage. In the case of plums as well as with red grapes intended for wine making, a marked increase in the content of phenolics of potential antioxidant potency was seen in the fully ripe stage in comparison with the less ripe stage.2,3 In contrast, no clear differences were observed in other fruits, e.g. peaches and
By definition, wine is a fermented product from fruits. By far the most important wine is produced from grapes, although it can be produced from apples, pears, berries, and other fruits. Vitis vinifera and V. labrusca are the most important species. Grape growing is a science itself (viticulture), and wine making is called enology.
With respect to the role played by these non-Saccharomyces species in wine quality, they are known to have the capability to improve the wine aroma (Charoenchai et al. 1997 Esteve-Zarzoso et al. 1998). The available aromas in the grape impart and define the characteristics and the final quality of wine. Terpenic compounds account for most of these aromas. Grape processing liberates small quantities of aromatic terpenols however, odorless precursors in the grape present a large, untapped reserve for wine aromas. Not only is the aroma an important quality factor in wine but also the intensity of the color is another very important quality factor in red wine, where anthocyanins are the main pigments. Various enzyme activities can improve the process of winemaking and enhance wine quality. The yeasts involved in wine making could be important producers of these enzymes (for a review see Table 1).
After grape harvest, American winemakers usually first destem the grapes. Destemming in some European cellars is a current enological practice. Destemming grape clusters produces wines with less catechins and procyanidins. Some evidence indicates only a small reduction in epicatechins as compared to about a 25 reduction in catechin and procyanidins in wines from destemmed grapes.
Pectinases are a group of hydrolytic enzymes, usually referred as pectolytic enzymes, which find important applications in the food and beverages industries, in addition to various other industries. Pectolytic enzymes degrade pectic material and reduce the viscosity of a solution, making it easier to handle. They are used industrially in fruit processing to facilitate pressing and to help in the separation of the flocculent precipitate by sedimentation, filtration, or centrifugation in the extraction of the clarified juice (95). Pectinases are used for the elimination of pectin in wine making, coffee and tea processing plants, and maceration of vegetable tissue (93,94). Pectinases comprise hydrolases, lyases, and oxidases, and can be obtained from higher plants, microorganisms, and insects (96). Pectinases can be obtained from several fungi, bacteria (including alkalophilic), actinomycetes, and yeast, such as alkalophilic bacteria, actinomycetes, Aspergillus versicolor, A. niger, A....
Strain differences among Saccharomyces sp. may be significant in terms of nitrogen requirements, the time frame for uptake and release of specific amino acids during fermentation, and the ability to ferment to dryness. Henschke and Jiranek (9) reported that the Montrachet strain had the highest nitrogen demand and exhibited the highest rate of amino acid and ammonium ion accumulation relative to sugar fermented among several strains studied. When considering utilizing unfamiliar strains, the winemaker is urged to consult the supplier's technical representatives.
Specifically, wines produced from high-N musts have a higher concentration of esters and lower concentration of fusel alcohols. Both are positive factors contributing to wine quality. Successful management of nitrogen deficiency requires that the winemaker identify the potential for problems early in the winemaking process. Routine and easily performed estimates of assimilable nitrogen (FAN + NH4+) during juice and must processing would be a valuable tool for the winemaker. Historically, several analytical methods have been proposed to measure total nitrogen. These have included ninhydrin (66) and the trinitrobenzene sulfonic (TNBS) method described by Crowell et al. (67). Utilization of TNBS has largely been discontinued because of difficulties in obtaining the chemical as well as waste-management issues. Further, these methods yield erroneously high results because of the inclusion of variable concentrations of protein and peptide nitrogen,...
Some red Spanish wines, such as pinot noir and merlot, have been reported to have average levels of trans-resveratrol of 5 and 4 mg L, respectively (8). The cis isomer of resveratrol has not been reported as a natural product in wine, but it is present and probably occurs from light exposure during winemaking and or during storage (8).
Since antiquity grapes have played an important role in the European diet. They were eaten fresh, especially in the grape-growing areas, added to dishes dried or in the form of grape juice, or they were made into wine, the drink of choice for anybody who could afford it. The wild grapevine, a climbing plant like the later cultivars, was indigenous to the area between the Black Sea and Afghanistan. The Phoenicians introduced the vine to Greece sometime after 1000 b.c. from there it spread throughout the Mediterranean. The ancient Egyptians grew grapes, as did the Romans, who were especially fond of various grape syrups in their cuisine. Among them were defrutum, or boiled-down unfermented grape juice, passum, a cooking wine that was even sweeter, and mulsum, a mixture of white wine and honey. As the Roman Empire expanded across Europe, so did the cultivation of grapes, and the art of wine making. In the Middle Ages, great quantities of wine were produced, traded, and consumed in...
Nitrogen compounds in grapes play important roles as nutrients for microorganisms involved in winemaking and wine spoilage and as aroma and aroma precursors (7). Nitrogen is taken up by the vine roots as nitrate and reduced by the nitrate reductases system to ammonia, transported and stored subsequently as amino acids (7). Compared with fermentable carbon generally present in grapes at 20 (w v), total nitrogen levels range from 0.006 to 0.24 , of which only 0.0021-0.08 is biologically available to fermenting yeasts (8). Thus, nitrogen may become an important growth-limiting constraint for microorganisms.
Making Your Own Wine
At one time or another you must have sent away for something. A