Wednesday, July 29, 2009
Pinot Noir Winemaking 101 decision Chart from Oregon Pinot Camp
A few wine terms worth knowing
Saignée (the French word for the medieval medical process of bleeding) is used when a winemaker desires to impart more tannin and color to a red wine. The process involves the removal of some almost-colorless juice from the must in the fermenter at a very early stage – it is also known as “bleeding” the fermenter. The red wine is intensified as a result of the bleeding because the volume of juice in the must is reduced relative to the surface area of remaining grape skins. And in some senses, the must involved in the maceration is concentrated. (Typically, the removed juice is fermented separately, producing a rosé wine as a byproduct.)
The winemaker may choose to have some or all of the clusters go through a destemmer that removes the individual berries from the stem. Those clusters go into a destemmer or destemmer-crusher. This is simply a device that tumbles the entire clusters inside a perforated drum, allowing the berries to fall through the perforations and the stems to exit separately out the other end into a bin for disposal. In some machines, the berries then pass between two long, soft rotating cylinders with a variable slot that serves to “pop” varying percentages of the berries before exiting the bottom. Gentleness, capacity, and ease of cleaning are the primary differences in these machines. Some winemakers choose to use a percentage of un-destemmed whole clusters in their fermentation. This is achieved by bypassing the destemmer and simply dumping the chosen amount of clusters directly into the fermenter.
SO2 is added to almost every must and wine and is one of the most basic and important quality control measures available to the winemaker. SO2 acts as both an oxidase enzyme inhibitor and as a microbial growth inhibitor. SO2 is added to the must early (within minutes or hours) to prevent browning and to inhibit native flora. If the native bacteria and yeast grow out of control, the result can lead to higher volatile acidity (VA), off flavors and aromas, and possibly fermentations that stop with sugar still in the wine (stuck fermentation).
The impact of SO2 additions is strongly affected by the pH of the must. If tartaric acid additions have been made, the acidity and pH will change, affecting the activity of the SO2. Almost all of the SO2 added to the must will be bound up during the fermentation and eliminated at pressing. It is almost always added again at the end of malolactic fermentation to protect the young wine from oxidation during the aging process.
Yeast and Yeast nutrients
Once a suitable environment has been created in the fermenter, yeast can be added to start active fermentation, or yeast will not be added at all if the winemaker has decided to let the ferment go native. There are many types of commercial yeast available to winemakers, all with their own special characteristics, from aromatic enhancement to high alcohol tolerance. The timing and quantity of yeast additions affects how quickly the fermentation starts and how rapidly it progresses.
Yeasts require a wide variety of nutrients to grow and perform their job of converting sugar to alcohol. Acid, high temperatures, and alcohol stress the yeast and can lead to off aromas and yeast death. Grape musts can vary dramatically in the level of these nutrients and are often deficient in one or more essential elements. An analysis can be done to determine whether and by how much the must is deficient in the major nutrients required for yeast to grow and complete fermentation. Once fermentation begins, the required amounts of nutrients can be added to the must. This practice ensures healthy fermentations that go to dryness and produce low amounts of off aromas such as sulfides.
Roto-fermenters are horizontal, closed tanks that can be rotated to mix the cap with the must in a pre-programmed manner. They require minimal attention and are easy to empty, but are very expensive to purchase and can lead to over-extraction.
Pigeage (literally “by foot”). In a shallow tank this involves walking on the fermenting must to mix the cap. In larger tanks, it involves immersing most of your body in the wine and mixing in any way possible as you swim or crawl around. A very low-tech approach, it is the most personal cap management tool.
Fining and Filtration
Fining and filtration are tools for clarification and for tannin and flavor modification of wine. Wines can have a high volume of suspended solids that will not clarify by settling and need to be removed prior to bottling. Some wines have bitter and unpleasant tannins or other negative flavor compounds that need to be removed or modified. The decision to fine or filter a wine depends on the specific problem that needs to be addressed. The choice of what to do is often based on small experiments called bench trials. The winemaker takes small samples of wine and adds various fining agents or combinations of fining agents to determine their effectiveness in solving the problem. That information is then used to treat the entire lot. The most common fining agents are egg whites, gelatin, milk and whey, and isinglass (protein from the air bladder of a sturgeon). These are often effective in extremely small doses, measured in ounces per one thousand gallons.
Bitterness is one of the more common problems addressed by adding fining agents. As wines age and develop, tannin molecules connect into chains of varying lengths. Some of these are perceived as bitter or astringent and can be removed by adding specific proteins to the wine. Unfortunately, there is no laboratory test to analyze exactly what tannins are causing the problems or what treatments are most effective in their removal. Luckily there are a wide variety of fining agents and the best treatment can be determined by bench trials using specific agents at varying doses. Although effective in removing undesired tannins, fining a wine always removes some positive flavor components. The goal in fermenting, pressing and aging is to end up with all of the extracts and flavors that the winemaker wants and nothing extra. That way, nothing will have to be removed. In certain circumstances filtration is necessary. White wines are commonly filtered.