February WOTM: Malolactic Fermentation

By: Mackenzie Brisbois

Often called malo or MLF for short, malolactic fermentation is an optional technique employed by winemakers. It is a conversion of malic acid to lactic acid, which reduces the acidic perception of the wine on the palate. Malic acid tastes like green apples, whereas lactic acid tastes buttery or creamy. Many winemakers add commercial bacteria to complete this action, but at Trail Estate we just let the natural bacteria present in the wine carry out this activity. 

The main bacteria are called Oenococcus Oeni, although there are other species, like pediococcus and leuconocos that can operate at a high pH level, often causing undesirable by-products. Within each species of bacteria there are also different strains, which can give different outcomes. Winemakers employ MLF on wines like Chardonnay or Cabernet Franc to make wines softer and creamier. If a winemaker wants to craft a fruity, crisp wine, often they will inhibit MLF. This can be done through an addition of sulphur and sterile filtration.
I don’t filter my wines so they all go through MLF. If they don’t before bottling — like in the case of the petillant naturals — they will go through this process at some point in bottle and will alter the flavour and composition of the wine (increasing the potential for foaming over).

MLF bacteria thrive within certain parameters and seeing a wine to completion can sometimes be challenging. The bacteria love a higher pH, a warmer temperature, a few extra nutrients and a large population. Conversely, aging minimal intervention wines is best done at lower pH and cool storage conditions. Total opposites! 

We want malic bacteria to be happy and complete MLF, but the wine can only be warmed up to a certain point. If the pH is too high and the temperature is too warm, the wine is perfect for a lot of spoilage. We try to find a happy medium and give the wine time!

FOXCROFT VINEYARD

Located about 5 km from Lake Ontario, the Foxcroft Vineyard sits just towards the top of the escarpment, sitting at 110 meters elevation. Winemakers like Thomas Bachelder have worked tirelessly to showcase the different reflections of terroir from this vineyard which is situated on a desirable band of land in the Twenty Mile Bench appellation. The terroir comes from old marine soils, giving wines a great mineral component. The Cabernet Franc at Foxcroft, slopes slightly south, giving this site ample sunshine required to ripen the later red variety.  

Foxcroft Cabernet Franc 2017
VQA Twenty Mile Bench

harvest date: November 22, 2017
brix: 24.8
cases produced: 142
alc./vol.: 14.5%
ph: 3.25
ta: 7.74g/L
residual sugar: 0.2g/L
drinking window: 2024-2030
barrels used: 20% 2^nd fill French oak, 80% 3^rd fill
va: 0.60g/L

winemaking: Harvested towards the end of November in 2017 this wine is the definition of slow wine. The grapes were extremely cold and this is the one of the only years the wine would not ferment. I intervened and inoculated with a neutral yeast strain. Pressed after a month maceration and put to barrel in January of 2018. Left unsulphured until November of 2019, two years after harvest. Still fresh and vibrant this wine tasted of freshly fermented grapes for most of its life. Finally gaining some characteristic traits of the Foxcroft Vineyard it was pulled from barrel, 20ppm total sulphur was added and bottle in December of 2019.

tasting note: A fruitier and leaner Cabernet Franc than normal from the Foxcroft Vineyard. Notes of raspberries and red berries intermingle with moderate tannins on the palate. A slow wine to make and a slow wine to develop. Decant now to open up the full spectrum of flavours.   

mlf check: August 9, 2019 
malic bacteria: 0.3g/L

MLF is considered finished when malic acid reads <0.05g/L but I think less than 0.3g/L is pretty good for this wine considering the long aging conditions. The VA (volatile acidity) read out at 0.6g/L and the RS (residual sugar) read 0.2g/L so I was happy to wait an additional 4 months to put this wine to bottle, just to give the wine time to move through a little more malic acid. I tasted this wine in January 2022 with the cellar crew at Gabrielskloof in South Africa and it was funny to see the descriptions that rolled around from Old World to New World! It was a tough wine for them to place!  

Foxcroft Cabernet Franc 2019
VQA Twenty Mile Bench

harvest date: November 9, 2019
brix: 22.8
cases produced: 200
alc./vol.: 14.5%
ph: 3.43
ta: 6.68g/L
residual sugar: <3g/L
drinking window: 2023-2026
barrels used: 25% 2^nd fill French oak, 75% neutral
va: 0.58g/L   

winemaking: Fruit was hand harvested from the Foxcroft Vineyard. Destemmed fruit had a temperature of 6°C and a was warmed up to start ferment naturally. The ferment took almost 10 days to get going with pumpovers daily to incorporate oxygen. During fermentation the cap was punched down twice daily — with about 1 month maceration total. Pressed and racked to barrel to age for 19 months. Bottled unfined and unfiltered. 

tasting note: A bold and perfumed Cabernet Franc with leather, menthol and black pepper on the nose. The palate is full with bright acidity, medium grained tannins and a lingering finish. This wine will drink best if decanted or aged for a few years. Best drinking is 2023-2026.  

mlf check: August 24, 2021
malic bacteria: 0.411 g/L

Given the high malic acid level I could have left this wine to age a little bit longer. With 19 months ageing under it’s belt I didn’t want to wait so long that this wine oxidized and took a bit of a leap and put it to bottle. With a VA of 0.58g/L the wine was relatively safe to age a bit longer had I decided to go that route. I did add more sulphur to this than to the 2017 to inhibit any futher MLF. An addition of 50ppm total sulphur was added at bottling.