Since the beginning of the 20th century, the decrease in total acidity in wines rich in malic acid has been one of the most studied biological processes in oenology. When refining wines, the malic degradation of acidity is an indispensable condition that, in turn, increases wine complexity and quality.
In the winemaking process, there is an increasing trend towards optimizing microbiological aspects, both to control the fermentation process, and to avoid compounds with a health risk such as biogenic amines.
In this post, we will discuss lactic bacteria, increasingly used in wineries to improve wines from an organoleptic point of view, while also limiting the production of compounds that can carry health risks.
The Agrovin Technical Department has developed a specific product based on lactic bacteria for controlling malolactic fermentation with the aim of obtaining excellent quality wines that are healthier and with a bioprotective character, while managing to reduce the amount of sulphide necessary for their conservation.
But first, let’s learn more about this type of fermentation. Let’s get started:
In malolactic fermentation, the predominant bacteria are those of the species Oenococcus oeni. During the course of malolactic fermentation, a series of changes occur due to the metabolism of the bacteria that allow them to dominate the entire fermentation process. Oenococcus oeni bacteria have special characteristics that make them suitable for winemaking, because they adapt more effectively to the conditions of the wine, especially those more complex wines with pH of 3.5 or lower, high ethanol content and those that have a greater resistance to sulphur dioxide (SO2).
Advantages of liquid crops
For malolactic fermentation to take place, a number of conditions have to be met.
The lack of lactic bacteria or the lack of optimal conditions means that it does not always occur spontaneously.
To accelerate the beginning of malolactic fermentation, a selected culture can be used, with bacteria that have a great implantation power. The advantage of liquid crops is that there is no need to rehydrate the bacteria, since they are ready for use and adapted to the wine environment.
What is malolactic fermentation?
It is the fermentation that gives rise to a deacidification of the wines. In this case, sugar is not the substrate, but malic acid.
There is always a certain amount of L-malic acid in the must, which produces a harsh sensation in the mouth. After alcoholic fermentation (which can sometimes occur simultaneously), lactic bacteria are responsible for producing the decarboxylation of the L-malic into L-lactic acid, with CO2 detachment.
The benefits of malolactic fermentation are both gustatory and aromatic. The volatile compounds that bring complexity to the aroma synthesizing, also modifying certain physical-chemical parameters of the wine that can affect the color of red wines.
One of these transformations involves citric acid, whose maximum initial concentration is in the order of 0.25 g/L. This leads to the formation of diacetyl (a molecule with an aroma of butter) that obviously participates in the wine’s bouquet, provided that it is not excessively perceived.
What factors affect malolactic fermentation?
Malolactic fermentation is conditioned by the following factors:
- Temperature: the optimal temperature for malolactic fermentation is between 20ºC-25ºC
- Low pH results in problems during the onset of malolactic fermentation.
- Lactic acid bacteria are especially sensitive to free sulphur.
- Alcoholic content.
- Content in IPT.
- Available nutrients.
What are the benefits of malolactic fermentation?
- Improved flavor. Malolactic fermentation causes a considerable improvement from the gustatory point of view, providing more oiliness and thickness to red wines. This is due to the decrease in acid indices and the substitution of an acid with a very pronounced taste, malic acid, with another that’s a little less aggressive to the taste buds, i.e. lactic acid.
- Aromatic profile. At the aromatic level, the most significant phenomenon related to malolactic fermentation are the hints of butter in the aromatic profile resulting from the moderate production of diacetyl.
- Another characteristic of note is the formation of ethyl esters (ethyl lactate and ethyl succinate) that provide volume and roundness to the wine with touches of milk and coffee.
- Microbiological stability. The conversion of malic acid into lactic acid leads to microbiological stability in the finished wines, since lactic acid, unlike its precursor, is not a substrate for microbial action.
What problems could occur during malolactic fermentation?
- Increased volatile acidity
The production of acetic acid results in an increase in volatile acidity.
- Loss of color in red wines
After malolactic fermentation, red wines could change in color due to a rise in pH, which is manifested by a loss of vivacity and a decrease in color intensity with a fewer blue tones.
There may also be a decrease in color through absorption of the lees generated. Therefore, it is advisable to work with lactic bacteria whose cell walls has a low affinity for anthocyanins.
- Loss of varietal aroma
Varietal aromas can be affected during malolactic fermentation. A significant decrease in these aromas can occur due to an excess of diacetyl or the presence of biogenic amines that mask these aromas in the wine. Another cause may be due to the reduction of esters caused by bacteria.
- Production of biogenic amines
These compounds are responsible for producing a decrease in the sensation of fruit in the wine, and in high concentrations, these compounds can cause unpleasant aromas of putrid meat, which, in extreme situations, can even cause intoxication. These compounds are generated from the decarboxylation of amino acids. Controlling the concentration of these biogenic amines is fundamental in the oenological sector to produce quality wines. The most relevant biological amine is histamine and its presence at certain levels in wine may lead to restrictions on its import into some countries.
VINIFERM OE AG-20 from Agrovin for the control of malolactic fermentation
Agrovin’s technical team has developed a proprietary product called Viniferm OE AG-20, which helps control malolactic fermentation. This product consists of second-generation lactic bacteria for the production of quality wines, respecting as much as possible the varietal character of the wine both at an analytical and sensory level.
It works by controlling spontaneous malolactic fermentations, limiting the development of undesirable microorganisms and eliminating the risk of producing biogenic amines even in wines with high alcohol content and high pH.
Where do we get these bacteria?
Viniferm OE AG-20 consists of bacteria of the genus Oenococcus oeni, naturally selected from wines and musts of the Tempranillo variety from the D.O. Ribera del Duero.
What is the purpose of selection?
The AGROVIN Technical and R&D&i Department has been working for several years to select native lactic bacteria in order to produce healthy, bioprotective wines, thus avoiding possible microbiological deviations and thus reduce sulphur doses during storage, which can significantly increase the organoleptic quality of the wines.
They are used to make wines with a high alcohol content, with a lot of color or wines with a low pH.
The following comparison considers the levels of histamine in wine during four vintages, comparing the differences between inoculated, non-inoculated and co-inoculated wines, while also evaluating the alcoholic strength of each, a factor related to the wines’ histamine content. The following results were obtained:
Graph 1. Histamine content during several vintages based on the alcoholic strength and the inoculation (or not) of selected lactic bacteria
It can be observed that throughout the vintages, the histamine content decreases in all wines, regardless of the alcohol content, with the selected strain being that which is predominant in the winery in both inoculated and non-inoculated wines.
What are its oenological properties?
- Fast and safe fermentation.
- Optimal fermentation temperature, 22-25 °C
- Total sulphur tolerance < 60 mg/l.
- Tolerance of free sulphur content < 10 mg/l.
- Alcoholic Tolerance <16%vol.
- PH tolerance > 3,4
- Low Volatile Acidity Production
- High fermentation kinetics
- Low production of biogenic amines with zero histamine production.
- High propagation and multiplication capacity in the wine environment.
- Bioprotective nature: Its high prevalence avoids microbiological deviations due to other microorganisms (Brett). Highly effective in imposing itself against other lactic bacteria, avoiding the presence of histamines.
What are its organoleptic qualities?
- It enhances the varietal aromatic characteristics.
- It allows the wine to maintain the fruity and floral expression after malolactic fermentation.
- It maintains the characteristic fruity expression, due to the absence of dairy aromas (diacetyl, acetoin)
- It accentuates sensations of body and volume in the mouth.
- Due to its low impact on acidity, it helps to slow the evolution of color.
- No color loss due to absorption.
How is it applied?
It is particularly suitable for high-quality red wines with good evolution over time and made with all kinds of varieties, such as Ganache, Merlot, Tempranillo, Syrah, etc.
It shows excellent results in malolactic fermentation in barrels, maintaining the wine’s aromatic and chromatic qualities.
It is also suitable for sequential fermentation and co-inoculation.
For more information: comercial@agrovin.com