Yeasts:
As a substitute for the White Labs Bastogne Belgian Ale WLP510 you can use Abbey Ale Yeast WLP530 (Westmalle). As the yeasts are the star of the show I would not try to cut corners here.
The WLP650 Brettanomyces Bruxellensis yeast is only added for secondary fermentation. As an alternative you could add the dregs from two bottles of Orval and add this to save some costs. Add the brettanomyces after primary fermentation and leave it for about 8 weeks to condition in the fermentation tank. Please note that Brett could infect your plastic equipment so use dedicated equipment to prevent future infections. Dry hop at the end of these 8 weeks.
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Malts, fermentables and substitutes:
- Try to use continental grains for the most authentic result. Belgian pilsner is perfect, but German will work just fine.
- Caravienne can be replaced by a caramalt of 50 EBC or 20 Lavibond. For example CaraRed
- Instead of Belgian candi you can also use normal granulated sugar. In both cases they can be added 15 before the end of the boil.
Mash schedule:
Belgian beers benefit from a step mash. Use the following schedule if possible:
1) bring your mash water to 38°C and add the malts
2) bring it to 61°C (142°F) for 15 minutes
3) bring it to 68°C (154°F) for 25 minutes
4) bring it to 72°C (162°F) for 30 minutes
5) bring it to 77°C (170°F) for 10 minutes
6) sparge at 77°C (170°F)