August 27, 2014

ML what?

MLF … as in malolactic fermentation. It’s not a true fermentation. It’s a metabolic process enabled by lactic acid bacteria which convert sharp-tasting malic acid into the softer lactic acid. Malic acid is the primary acid found in, for example, Granny Smith apples while lactic acid is commonly found in milk products. In wine, it is the second-most important acid after tartaric acid. Malic acid can be present at high levels in cool-climate regions or in a poor, cold, wet vintage. The idea here is to “soften” the wine’s acidity (TA) and reduce overall total acidity. Reds benefit from acidity reduction especially when there are aggressive tannins. Tannins impart bitterness in young wine, and acidity heightens the taste of bitterness. MLF can also increase aroma and flavor complexity.

There are as many opinions as winemakers as to the timing of inoculation for MLF; some like to co-inoculate, i.e. concurrent alcohol (AF) and malolactic fermentation, some prefer to inoculate midway through the AF so as to reduce competition between yeasts and bacteria, and others, like me, prefer to wait until the end of the AF to inoculate to completely eliminate any competition. Competition between yeasts and bacteria can be detrimental to one fermentation or the other. The key word here is “can” as many trials, including my own, have shown that concurrent inoculation can lead to greater wines in some cases.

Today, processing included racking the wines off their gross lees so as to avoid any potential hydrogen sulfide (H2S) formation. I ended up with 12 liters (just over 3 gallons) of each vintage in a carboy topped with a little press wine. I also ended up with roughly 2 liters (just over half a gallon) each of press wine, and so I blended them into a single container. Since it is partially filled, I purged the air out with some CO2 to protect the wine during the MLF sojourn.

I racked using a positive-displacement diaphragm pump that has served me very well over the last 20 years. Notice that I used an inline strainer to catch pips and any leftover grape solids to avoid damaging the pump. I let the wine splash in the bucket and then transferred it to carboys with a vigorous splash. I wanted to introduce some oxygen into the wine to start the magic of polyphenol polymerization.

Table 1

Before I inoculate, I need to measure some key parameters to assess the impact of AF and gauge potential impacts from MLF. More important, I need to ensure that everything is favorable for a successful MLF; malolactic bacteria can be very finicky. Important parameters are free/total SO2, alcohol level, pH and temperature. Everything seems good for a GO. Here are today’s numbers in Table 1 along with Day 1 numbers for comparison.

And here are Brix progression numbers since Day 1 in Table 2:

Table 2

From Table 1, it can be concluded that the AF is essentially complete and that the wines are dry. Brix will probably decrease another 0.2 to 0.4 or more. However, the numbers reveal other interesting information.

First, the 2011 vintage shows a marked decrease in pH down to 3.48, which would suggest possibly a sharp increase in TA. In fact, TA shot up from 4.2 to 8.5 g/L! Quite a drastic increase. I did not expect this. This was also my first opportunity to taste the wine. The tannins are relatively softer than I would have expected but the acidity is definitely very present. This has the making of a great wine.

The 2013 shows only a slight decrease in pH but, surprisingly, a marked increased in TA. My first taste test confirms high acidity but very firm tannins. Color and taste are outstanding — another great wine in the making.

The color on both vintages is spectacular; with the pH in ideal range, the color will hold nicely.

The TA increase is nothing to worry about since the MLF and cold stabilization will bring down TA numbers. The sharp increases can be attributed to grape solids, and esp. uncrushed whole berries, releasing some of their acids. I will confer with the enologist at Vino Superiore to get his take on these TA numbers. pH numbers are looking good.

Free SO2 numbers are also looking good and well within the range for MLF inoculation. It looks like fermentation produced very little SO2 though most probably quite a bit dissipated into the atmosphere. What’s most interesting though is that I was able to get a free SO2 reading for the 2011, which I could not when I received the must; however, there is still some interference causing a skewed total SO2 measurement. This has got me scratching my head. I’ll have to dig deep in wine chemistry to figure this one out. I’ll also contact the enologist at Vino Superiore to get his take on this. All very interesting.

I have chosen Laffort’s SB3 Instant lactic acid bacteria for the MLF … well, that’s what I found in the freezer. The package says “direct incoluation” but it needs to be rehydrated first. While rehydrating, I added OptiMalo (nutrients for the ML bacteria) to the wine at a rate of 20 g/hL, or roughly 1 tsp per carboy.

I have taken the bacteria sachet out of freezer and allowed it to reach room temperature – approximately 1 hour and a bit. Then, I rehydrated the culture in tap water for approximately 20 minutes before inoculating the carboys. Malolactic bacteria is very sensitive to oxygen, so I stirred VERY gently. I’ll keep temperature around 20C (68F) until the end of MLF. I’ll monitor MLF using a strong flashlight against the neck of the carboy looking for bubbles. When there are no more bubbles, I will test for the presence of any remaining malic acid using a paper chromatography kit. When it’s all over, I will sulfite promptly to avoid spoilage problems.

All so very exciting!