The ratio of main components of miso plays a big role in the time of fermentation and it’s final flavor. Altering those ratios can result in different outcomes even if using the same type of koji and beans.
The amount of koji mixed with the beans translates to the amount of enzymes that are gonna work on breaking down the beans into umami agents. The higher amount of koji, the sweeter flavors of your miso will be. The proportions will also result in different fermentation time. More koji – less time.
Playing with the ratio of salt added to the paste results in different time of aging your miso. The lowest amount you should put to make sure the batch won’t spoil is around 4% of the total weigh (beans+koji). This will also encourage lactic acid bacterias to propagate a bit more, giving your miso some funky flavors. High salt content (up to even 16%) will slow down the process that might then take up to 2 years. The trade off here is that you will get a deep strong savory miso so concentrated that only a tiny amount of it might be a game changer in your cooking.
Basic recipes would call for equal amounts of koji and the beans. With a standard 6% of salt it should take around 6 months to get the miso ready.
The miso on the upper photo has been made with 3 parts barley koji to 1 part mushrooms. Salt content of 8% and fermentation time of roughly 4 weeks resulted in an interesting savory flavors. Be aware that lowest ranges of salt will shorten the shelf life of miso and might allow pathogens to develop in the batch.