The boiled water (100oC) is brought to the suitable temperature for the yeast to work as 10 - 15oC. This temperature depends on the type of yeast and the type of beer. We actually wrote a complete guidebook about buying in Ho Chi Minh Metropolis that you should consider if https://edwinrvwwx.blogrenanda.com/39042384/5-simple-statements-about-saigonlist-explained