There are a number of spoilage microorganisms and yeasts that grow rapidly and play havoc in the winemaking process. Although the mature grapes harbour these spoilage microbes, however, the bigger problem occurs when winery equipment is infected. These microbes produce volatile phenols and acetic acids giving white wines medicinal aroma and red wine leathery aroma. Other bad aromas include tar, tobacco, plastic and barnyard.
During the fermentation process of winemaking, the presence of such microbes can be indicated by a sluggish fermentation or spontaneous malolactic fermentation, volatile acidity or other off-odours. Due to the presence of these spoilage microbes every winery has incorporated microbiological techniques and sanitation monitoring into their production practices.
Here are some of the techniques used to detect the spoilage microbes.
- Microscopy or Epifluorescence
A microscope is capable of 1000x magnification is needed to view yeast and bacteria, but they can cost anywhere from $1000-$3000 or more which is quite expensive. However, there is a solution to this as well, winemakers can use their smartphone as a microscope. The high-quality USB microscope accessories are available online to conveniently convert the smartphone into a high powered microscope. Winemakers just need to have proper training and knowledge to identify the microorganism. Just prepare the slides and take high-quality images and videos of your findings and share them too with other winemakers and researchers. In addition to identifying spoilage microbes, it can also be used to monitor yeast populations.
Using smartphones as microscopes have an added advantage too as they are portable and can be carried along to the field to check for the spoilage microbes on the grapes. You can then share the photos and videos of the microbes through the portable digital microscope USB and implement preventative steps for contamination of your wine.
Membrane Filter Method
This method is used to isolate small number of microbes from the liquid sample and sterile cellulose nitrate membrane is placed on a vacuum flask and filtered. Using sterile technique, the nitrate membrane is placed on the culture plate and monitored for microbial growth. This method could be used to check bottle sterility.
This is a swab test method and is used for semi-quantitative analysis. Sterile cotton swabs are moistened with sterile saline and used to monitor dry areas, on the other hand, dry swabs are used to test moist areas. The swabs can then be used to inoculate the proper agar medium, depending on the organism you want to detect. Agar plates can also be used to airborne organism’s detection at critical winery locations. Agar plates are left open for 30 minutes to 2 hours and then incubated. Airborne organisms that settle on the plate will grow and can be further identified using microscopes.
The above-mentioned are the preventative solutions to control the contamination of spoilage microbes.