13.7 General Winemaking Options: Malolactic Conversion

Question 1

What is malolactic conversion?

Answer 1

• the result of lactic acid bacteria converting malic acid into lactic acid and carbon dioxide, produces heat

Question 2

When does malolactic conversion typically occur?

Answer 2

After, sometimes during, alcoholic fermentation

Question 3

What conditions encourage malolactic conversion?

What can be done to initiate it in the winery?

Answer 3

• 18–22°C (64–72°F)
• a moderate pH (3.3–3.5)
• low total SO2
• can be started by adding (‘inoculating with’) cultured lactic acid bacteria in the presence of these conditions

Question 4

How will a winemaker initiate malo conversion in the wine?

Answer 4

• can be started by adding (‘inoculating with’) cultured lactic acid bacteria and making sure that the optimum conditions are available

Question 5

What conditions prevent malolactic conversion?

Answer 5

• temperature below 15°C (59°F)
• low pH
• moderate levels of SO2

Question 6

If a producer wants to ensure that malo does not occur, what can they do?

Answer 6

• add the enzyme lysozyme, which kills lactic acid bacteria
• move any batch of wine going through malolactic conversion to another part of the winery to avoid the spread of lactic acid bacteria
• lactic acid bacteria filtered out

Question 7

What types of wines go through malolactic conversion?

Answer 7

• Red wines routinely go through malolactic conversion

- It is a winemaker’s choice for white wines

Question 8

What are the 4 main outcomes of malolactic conversion?

Answer 8

1. Reduction in acidity and rise in pH
2. Some colour loss in red wines
3. Greater microbial stability
4. Modification of the flavour - butter notes, but also increase in volatile acidity

Question 9

Why does MLF result in a reduction in acidity and rise in pH? In what types of wines may this be desirable? What is the end result?

Answer 9

• Lactic acid is a weaker acid than malic acid
• May be desirable in overly acidic wines (e.g. Chardonnay grown in a cool climate such as Chablis) but not in wines that are already relatively low in acidity
• It results in a softer, smoother style of wine

Question 10

How does MLC stabilize a wine?

Answer 10

• prevents malolactic conversion from spontaneously happening later (e.g. when the wine is in the bottle) when it would be undesirable.

negative impacts:
- where the pH of the wine is high, raising the pH slightly makes the wine more vulnerable to spoilage organisms

Question 11

When a wine’s ph is high, why might MLF be undesirable?

Answer 11

• Raising the pH slightly makes the wine more vulnerable to spoilage organisms
• May create a wine that is not refreshing because the acidity will have been decreased.

Question 12

How does MLF affect the flavor a wine?

Answer 12

• slight loss of fruit character may occur
• addition of buttery notes (notably in white wine)
• increase volatile acidity

Question 13

What are the advantages /disadvantages of conducting MLF in small barrels as opposed to large tanks?

Answer 13

• the ability to be able to stir the lees at the same time
• promote better integration of the flavours

Disadvantage
- more work because barrels may be at different temperatures and so will need monitoring individually.

Question 14

Why might a winemaker prefer to promote malolactic conversion at the same time as alcoholic fermentation?

Answer 14

• in an attempt to reduce the loss of fruity characteristics

- reduce production times, saving money as wines can be finished and sold earlier