Carboys are filled to minimize oxygen exposure during storage. Keeping the carboys in a cool area also helps maintain freshness. Photo by Denise M. Gardner
Home winemaking and home brewing can be some fun hobbies for enthusiasts or amateur growers and winemakers. However, most home winemakers experience the same set of problems year after year without practical solutions for how to fix their wines or avoid challenges during production.
Using Concentrate, Fresh Juice, or Grapes to Start Primary Fermentation
Concentrates are produced and manufactured with a pretty high success rate that the fermentation will complete with some sort of noticeable quality resembling wine. These end up being the best product to use as an introductory fermentation base for those just starting to learn about the winemaking process. The concentrate is simple to use: pour into the fermentation vessel and "just add water and yeast."
The problem with concentrates is that they are easily identifiable during sensory analysis. This indicates that finished wines produced from a starting concentrate have a specific taste and quality that is noticeable sensorially regardless of the variety or source (i.e., country of origin) of the concentrate. These wines will likely appear "simple" with nuanced fruit characteristics and a strong perception of alcohol. This is also true for home winemakers that make hard cider from an apple concentrate.
However, when home winemakers switch to purchasing bulk juice or grapes, many experience new fermentation and production problems that were not associated with the use of concentrates. This is due to the fact that bulk juices (purchased from a broker or home winemaking supply store) may contain preservatives (i.e., sulfur dioxide) that can make the initiation of fermentation more challenging. Additionally, juice and grape quality is dependent on the source (i.e., country or region of origin) and how long the material was in storage before it arrived to the home winemaker's fermentation vessel.
With juice and grapes, the native microflora (e.g., yeast and bacteria), some of which can also be spoilage microorganisms, may have numerous effects on fermentation kinetics and the finished wine quality.
However, using grapes or bulk juice as the starting base will provide a finished product that is more representative of where the grapes were grown (i.e., terroir representation based on the country or region of origin) and provide the winemaker with more options for making the product unique.
Many home winemakers struggle with basic sanitation practices during processing, fermentation, aging, and wine storage. While most commercial sanitizers are not available to home winemakers, basic cleaning and sanitizing principles can easily be applied to home winemaking practices.
First, always make sure equipment is cleaned and sanitized before and after processing. For example, harvest equipment like crusher-destemmers or a wine press should be cleaned and sanitized before the grapes are put into the machines and after all of the grapes are processed. Another example includes adding substances to the wine or removing wine samples from a carboy. The equipment used to make the addition or to remove the wine should always be sanitized before it touches the wine.
For complex equipment (i.e., crusher-destemmers, presses) pulled apart and fully clean with hot water, a very small amount of non-scented dish soap, and some good, old fashioned elbow grease. All detergents should be thoroughly rinsed off the equipment with hot water to avoid contaminating your wine with soap. Removing debris and build up from all of the processing equipment improves the efficacy of a sanitizer. Cleaning is at least 95% of the sanitation process during commercial winemaking operations, and this theory is true in home winemaking as well.
After the equipment is properly cleaned and rinsed with hot water, sanitation can follow Using a citric acid-sulfur dioxide blend in cold water is a good no-rinse sanitizer that home winemakers can utilize if they are making wine in a well-ventilated area. It is important that home winemakers take the care and precaution to ensure safety associated with using volatile sulfur dioxide. Volatile sulfur dioxide is a lung irritant and can cause serious health issues if used improperly. People with asthma or other lung-related conditions should not come in contact with potassium metabisulfite or sulfur dioxide. For more information pertaining to how to properly use sulfur dioxide, please refer to Penn State's Wine Made Easy Fact Sheet on Sulfur Dioxide Managementand your potassium metabisulfite supplier.
The citric acid-sulfur dioxide sanitizer is a no-rinse sanitizer. This means that after the equipment has been exposed to the sanitizer and sanitized, the juice or wine can come in contact with the equipment without any worry by the home winemaker. Both citric acid and sulfur dioxide are naturally found in wine, so its use should not alter the flavor of the wine in any way.
Use Nutrients During Primary Fermentation
Many home winemakers use non-specific yeast nutrients purchased at a small home winemaking supply store during fermentation.
However, current research shows that nutrient additions need to be specific towards the fermentation. Home winemakers considering going into commercial production should get comfortable with commercially available nutrient supplements. Some home winemaking supply stores will carry small quantities of commercial products for a slightly more expensive price, but they are worth the investment when trying to make a higher quality wine.
At minimum, using a yeast hydration nutrient (like GoFerm or an equivalent) will help to start the fermentation positively. Complex nutrients (like Fermaid K or an equivalent) are typically recommended (up to a certain point) before using diammonium phosphate (DAP).
If you can find a way to measure yeast assimilable nitrogen, or YAN, then nutrient additions can be made in specific quantities throughout the duration of primary fermentation, using specific products (i.e., hydration nutrients, complex nutrients, or DAP). Hydration nutrients are added to the yeast slurry during yeast hydration, and prior to inoculation. Complex nutrients and DAP are, at minimum, added when 1/3 of the original sugar concentration (Brix) has dropped during primary fermentation. This is usually within 24-48 hours following inoculation unless the fermentation is progressing in a cool environment. Utilizing the supplier's guidelines for the rates of additions of your products, based on the starting YAN concentration, is a good way to minimize the risk of the wine tasting like rotten eggs or canned vegetables. For more information on yeast nutrition during primary fermentation, please refer to Penn State's Wine Made Easy Fact Sheet on Nutrient Management.
Avoid Excessive Oxygen Exposure
Winemaking is a tedious process. It requires regular attention and monitoring procedures (i.e., documenting sugar depletion during fermentation, daily monitoring of malolactic fermentation) to ensure that things have not gone awry.
Home winemakers should try their best to minimize long-term oxygen exposure. Using vessels to minimize surface area at the wine-oxygen interface will help reduce the risk of acetic acid bacteria contamination and growth, which contribute to the volatile acidity (i.e., the acetic acid - or vinegar - and nail polish flavors) of a wine. For this reason, carboys are usually recommend as opposed to open-top buckets.
If you need to "top up" carboys, use sanitize marbles and then add them to the carboy to "push" the volume of the wine up into the neck of the carboy. This helps minimize the surface area at the oxygen interface.
Avoid letting the wine "sit" when it is not going through an active primary fermentation or malolactic fermentation (MLF). If the wine does not need to go through MLF, make sure proper potassium metabisulfite additions are made to the wine to ensure preservation and stability. If the wine undergoes MLF, add potassium metabisulfite following the end of MLF. Sulfur dioxide levels in the wine are fluid and change regularly throughout the winemaking process. When a wine is being aged or stored, the sulfur dioxide concentration should be measured at least every other week. Future sulfur dioxide additions should be based on the pH of the wine to ensure that its addition is reaching its full antimicrobial protection.
Additionally, keeping the wines stored in a cool location will help minimize bacterial growth or yeast spoilage, while also preserving the wine.
Bottling the wines as soon as you can post-production can help ensure quality and stability and minimize excessive oxygen exposure.
Avoid Making Wines in an Aromatic Environment
One problem that some home winemakers face is aromatic absorption associated with the odor of the environment in which the wine was produced. This tends to be a problem when wines are made in an unfinished basement.
Wines are alcoholic solutions, which can absorb surrounding odors. As unfinished basements tend to have that "wet basement" odor, the wine will likely absorb that aroma and flavor into the finished product. However, many people may not be aware of the flavor until after the wine is removed from the odorous environment.
For more information on winemaking basics, please browse the Penn State Wine Made Easy fact sheet series. These products were written for both home winemaking and commercial production.