What is wet process?
Broadly, “wet” processing refers to coffee that is depulped and then the coffee is either fermented “dry” without the addition of water as is common in Latin America and places where water scarcity or preservation are concerns, or “submerged” where the coffee mass is covered with clean water and then allowed to ferment. This methodology precipitates two phenomena: demucilagination of the pulped coffee and the development of flavor precursors for your coffee. These 2 steps are traditionally called fermentation.
What is fermentation?
- In coffee, fermentation is a biological process carried out by micro-organisms mainly yeasts and bacteria. During the coffee maceration, the LALCAFÉ™ yeasts help firstly to degrade the mucilage from the coffee (demucilagination) due to their specific enzymatic activities and secondly, at the onset of fermentation, the yeasts, due to their specific metabolism, they reveal and enhance the sensory potential of the coffee.
- Fermentation and extended maceration have considerable impact on the final coffee quality, because they contribute directly to the sensory profile of the coffee. LALCAFÉ™ yeasts control the fermentation, yielding a higher quality and more predictable product due to their efficiency and metabolic profile.
What is the dry process?
Dry processing refers to coffee that is processed while leaving the fruit intact or what the coffee industry generally refers to as “naturals”. For clarity’s sake, we refer to this as “whole fruit processing”. Fermentation in this method of processing still occurs, though somewhat differently than in pulped or “wet” processing. LALCAFÉ™ Yeasts can be successfully employed in this mode of processing with just a bit of ingenuity.
Why control the fermentation with LALCAFÉ™ yeasts?
- During the maceration (the step after demucilagination, which should be roughly half of your standard fermentation time when using LALCAFÉ™ yeasts) , the LALCAFÉ™ yeasts help to protect the coffee from the growth of undesirable indigenous microflora that can produce spoilage characteristics, defects or simply unwanted flavors.
- With a maceration step in processing, LALCAFÉ™ yeasts will help reveal the unique varietal aromatic character of your coffee.
What makes the yeast different?
- Each yeast is unique and has its own metabolism which will impact the demucilagination and the final sensory quality.
- LALCAFÉ™ yeasts have been characterized and selected for their capabilities to maintain and improve coffee fermentation and quality during coffee processing. Many studies carried out by several research and technical centers recognized by the coffee sector (CIRAD, WASI…) have confirmed the positive impact of selected yeasts on coffee quality.
Why use LALCAFÉ™ yeasts in coffee fermentation?
They will help to:
- Better control the fermentation (avoid over fermentation, and spoilage indigenous flora contamination),
- Accelerate coffee demucilagination,
- Facilitate washing (reduction in water used),
- Depending on the LALCAFÉ™ yeasts used and the duration of the maceration, they will more or less impact the aroma expression of your coffee. These impacts have been shown on wine, beer and other fermented beverages.
How long is the fermentation for maximum yeasts impact?
- We recommend fermentation duration of 18 to 48h; the optimum will vary depending on desired flavor profile, the size of the fermentation mass, and environmental conditions at the wet mill.
- Even though demucilagination is complete, continued contact may benefit flavor development, LALCAFÉ™ yeasts need more time to reveal the coffee aromas.
How do I use LALCAFÉ™ yeasts?
- Yeasts are produced in dry form (active dry yeast) to make their transportation and storage easier. They need to be rehydrated before use.
- First, they must be rehydrated in 10 time the volume of water (10 liters for 1kg).
- The rehydration water must be clean (no smell, no chemicals inside), and between 15 and 37°C except for LALCAFÉ INTENSO™ (25-37°C).
- Stir in gently the yeast into the water to avoid lumps.
- Leave for 20 minutes.
What if lumps are present?
Lumps are formed because yeast was added too quickly or it was too cold. To solve this problem, you should stir again (gently) after 10 minutes of rehydration then let another 10 minutes to complete the rehydration.
What if I do not see foam?
There is no relation between foam (which could appear during rehydration) and the fermentation activities of the yeast. This is just a physical phenomenon of CO2 released which may be trapped by the yeast during the drying process. So foam does not impact the activities of the rehydrated yeast and they can be inoculated and used for coffee fermentation.
What LALCAFÉ™ dose should I use?
The optimal dosage is 1 g per kilo of coffee. This holds for pulped processes as well as whole fruit. If processing whole fruit, 1g/kg of fruit, if processing pulped coffee 1g/kg of pulped coffee. . If the water quality is doubtful, an adjustment of the dosage is required. For example, recycled water (brown color, smell of fermentation, alcohol…) you will need to increase the dosage to 1.5 g per kilo. Best practice is to use clean water.
How and when should the coffee be inoculated?
- Inoculation (adding the yeast for the coffee fermentation) is done as soon as possible after receiving fruit at the mill. For whole fruit we recommend utilizing a tank as one would with depulped processing to facilitate inoculation. . How the yeast is added to the fermentation tank is determined by the style of processing and the quantity of coffee to ferment:
- Up to 1,000 kg: put coffee in the tank then add the yeast at once then stir. The tank must be free of any chemicals or other compounds which could contaminate the coffee.
- From 1,000 kg to 5,000 kg, split the yeast addition. Add half of the yeast dosage when the tank is half-filled and then add the rest of the yeast addition once the tank is filled.
- “Dry” processing (depulped or whole fruit with no additional water except for the rehydration liquid)
- Introduce 25% of the rehydrated yeast as soon as the tank is 25% filled and stir to ensure even distribution. Continue with 25% increments until tank is full. If processing whole fruit, it may be wise to utilize a sprayer to ensure coverage and prevent unnecessarily damaging the coffee skin if the vessel is larger than 30L.
- Once yeast is rehydrated never leave it at ambient temperature for more than 30 minutes. You should prepare the yeast in function of the filling of the fermentation tank. If a tank takes 4h to be filled and you would like to make 3 inoculations, it will be better to do the yeast rehydration just before each inoculation.
Why should I use a wet process?
Adding water to cover the coffee has several benefits like reduction of the temperature variation. It also gives a better mixing of the medium which is more favorable for yeast growth. However, it is not completely necessary and “dry” fermentations can be effectively inoculated. The choice is as much about desired end cup profile as it is mill infrastructure.
How much water do I have to add to the tank and at which moment in the process?
Only add enough water to cover the fermentation mass (between 1 and 2 cm above the level of coffee) in order to ensure brix concentrations stay relatively high.
Does it need to be clear?
Yes, the water used to submerge the coffee must be as clear as possible. If you are using recycling water, never use water recycled more than two times.
Must I do my fermentation with LALCAFÉ™ yeasts in closed tank?
You do not need to cover or close your fermentation tank, though it is one of the many ways you can modulate the end cup profile of your coffee.
May I re-use water of fermentation?
Once fermentation is over or stopped, there is a great likelihood that there will be an imbalance in the substrate (glucose and sucrose) which compromises the yeast’s ability to continue do their work effectively. If survival factors are compromised, the impact of the yeast becomes unpredictable and we do not encourage this. Secondly, as coffee is rich in nutrients, this means that spoilage micro-organisms can also grow well at the same time. It’s best not to re-use the water as this can have a compounding risk effect where spoilage micro-organisms are present.
What happens in case of yeast overdosing?
- Overdosing will have no impact on end coffee quality.
- It will not reduce fermentation time.
- On the other hand, using too low of a yeast dosage will show no difference compared to your normal process or your coffee quality.
How to store the active dry yeast?
- You must keep yeast in a cold and dry place (the best condition is at 4°C). Shelf-life is 2 years for LALCAFÉ CIMA™, 3 years for LALCAFÉ INTENSO™, 4 years for LALCAFÉ ORO™ and LALCAFÉ BSC™.
- Avoid storage in hot place (up to 30°C) for more than 6 months.
- Once the bag is opened, use as rapidly as possible (during the following 15 days and it is best to close it and keep it at 4°C away from humidity).