No, you don't have to. You can just sprinkle in the yeast as is.
If you do, brewers need to make sure rehydrated yeast is within 5°C (9°F) of your wort temp to avoid subjecting the yeast to temperature shock.
Once rehydrated, immediately adjust the temperature of your rehydrated yeast by slowly mixing in small volumes of wort, staggering the additions by leaving 2-3 minutes between each adjustment, ensuring not to adjust the temperature by more than 10 °C with each addition. Do not allow the rehydrated yeast to attemperate by natural heat loss.
There has been some discussion out there that rehydrating the yeast increases the viability of the yeast, but also increases the risk of infection.
So it would need to be decided by you as the brewer as to how you would like to proceed.
If you are using the Mangrove Jack's M05 Mead Yeast and choose to rehydrate, we strongly recommend using the Mangrove Jack's Yeast Nutrient when you do so.
While honey is high in fermentable sugars, it is low in minerals and nutrients and has mild antiseptic properties, which makes fermentation more challenging for yeast. To ensure a healthy fermentation, additional nutrients is recommended.
Mangrove Jack’s Mead Yeast & Nutrients Rehydration Instructions
These yeast rehydration instructions are for 1x sachet (10 g) of Mangrove Jack’s M05 Mead Yeast;
Important note: We recommend using pre-boiled, sterilised water and sanitising all equipment before rehydrating your yeast.
Here's how to prepare the yeast:
- Santise all your equipment with pre-boiled, sterilised water.
- Mix 12 grams of Mangrove Jack’s Mead Yeast Nutrient in 200 ml of hot water (around 122°F or 50°C).
- Let it cool to 104°F (40°C), then add the M05 Mead Yeast.
- Let it sit for 15 minutes, then gently stir it. Wait another 5 minutes.
- Gradually blend 100 ml of your must into the rehydrated yeast slurry to temper it.
- Keep repeating step 5 every 5 minutes until the yeast mixture is within 10°F (5°C) of your must's temperature.
- Pour the yeast mixture into your fermentation container and let it ferment at the right temperature.
1 x 10 g packet of M05 Mead Yeast has enough yeast to ferment up to 17 L of must.
You can adjust the amounts if you're fermenting smaller amounts of must, based on how much yeast you need.