by Michelle Sadler, Dairy One
Do you know if the nutrient additions you make during the winemaking process are correct or even necessary at all? The Finger Lakes Wine Laboratory is here to help, offering tests on must and wine to provide you with information that allows you to make informed decisions throughout the winemaking process. Early evaluation of must can help avoid delayed or stuck fermentations and later evaluation can test for the completion of the secondary malolactic fermentation.
Nitrogen/Nutrient Content
It is well-known that not having enough nutrition for the yeast in a fermentation can yield some very undesirable results, usually in the form of hydrogen sulfide formation (a reductive, rotten egg smell) or a stuck or sluggish fermentation, and is almost always accompanied by a healthy dose of frustration. In order to prevent either of these scenarios, many vintners have adopted a policy of adding more than enough nutrient to the must. Until recently, the negative effects of having too much nutrient have not been widely explored. Certainly those effects can’t be as bad as hydrogen sulfide or a stuck fermentation, right? While they aren’t as immediately pronounced or obvious as the aforementioned issues, they do exist. The Finger Lakes Wine Lab can analyze your must for yeast assimilable nitrogen (YAN) in order to prevent both deficiency and excess of nutrition.
The first negative effect of a must with excessive nutrient is, fittingly, the opposite of a stuck fermentation: an excessively vigorous fermentation. A fermentation that has excessive vigor will produce carbon dioxide gas at a very fast rate and will also maintain a higher temperature. This forces many other volatile — but also desirable — aromatic compounds to be pushed out of the wine as well. This illustrates the old adage that states if your winery smells like fantastic wine, your wine may not.
Too much nutrient in a must will also mean that there will be excess nutrient still present in the must after the fermentation has completed. This excess nutrient can serve as food for spoilage organisms later on. These organisms include yeast strains such as Brettanomyces and Candida, lactic acid bacteria and acetic acid bacteria. Ironically, excess nitrogen has also been linked to an increased risk of inhibition of malolactic fermentation. Knowing your must’s nutrient content allows for optimizing your fermentation to be both predictable and efficient. It will provide added confidence during a busy harvest season, and could also make the need for primary, secondary, or tertiary nutrient additions disappear, freeing up valuable time for cellar staff. It may also mean cost savings on nutrient additives.
Malic Acid Content
The primary (alcoholic) fermentation is an important event for every wine, regardless of location, variety, or style, but another important fermentation for some wines is the secondary (malolactic) fermentation. This previously mentioned type of fermentation is a bit more delicate than its alcoholic counterpart and different in important ways. The bacteria responsible for this fermentation do not create a large amount of gas, the changes in flavors and aromas during their fermentation are more subtle and most importantly, a wine cannot be preserved with sulfur dioxide to prevent spoilage during this fermentation. A vintner must perform a balancing act when ushering a wine through malolactic fermentation. Adding sulfur dioxide before the fermentation is complete will cause it to stop, but if it is not added soon after completion, there is risk of oxidation or microbial spoilage. Knowing when the fermentation is complete is key. Tracking the rate of the fermentation can provide valuable information and allow for better planning as well.
How do I start testing?
The Finger Lakes Wine Laboratory can become a valuable resource and help provide information that you can use to make efficient decisions throughout the winemaking process. The lab provides testing containers, labeling, and shipping materials upon request. Visit for information about ordering these supplies. The lab also offers a free courier service for sample pick-up within a 50-mile radius of our Ithaca, NY location. Contact us by phone at 800-244-2697, extension 2174, or by e-mail at for more information.