Why it’s good to know your SP.
Rice is composed mainly of starch and when you’re making makgeolli it’s the nuruk’s job to break that starch down into smaller sugars for yeast to convert to alcohol. But all nuruk is not created equal. Some nuruk are able to break down starch super fast while others at a slower pace. This means that if you use a fast acting nuruk you won’t need as much of it and a slower nuruk will need more.
So, how do you know how much nuruk to add? Luckily on each bag of nuruk they will display the nuruk’s saccharogenic power, or SP. The SP is defined as the amount of starch that one unit of enzymes can break down in a given amount of time (Kim et al., 2011). Most ordinary nuruks like Songhak and Jinju will have an SP of about 300 while enhanced nuruk (개랑누룩)can have an SP of 1200! This means that you only need a ¼ of the recommended amount of nuruk and it breaks down the rice quicker so you can taste your sweet brew sooner.
You might be wondering, how is enhanced nuruk different than regular nuruk? First, let’s look at what molds are in nuruk. Nuruk contains Aspergillus, Rhizopus, and Litchemia species (Song et al., 2013). These molds produce alpha-amylase and glucoamylase which breaks down amylose and amylopectin, the main components of starch. These organisms all produce different amounts of alpha-amylase and glucoamylase, so, some work better than others. There are even differences in the amount of these enzymes between different strains of the same species. Enhanced nuruk contains a strain of Rhizopus that produces a lot of these enzymes. This super nuruk can even be used to digest raw rice (Park et al.2012)
SP is a pretty important aspect to the makgeolli making process. So, next time you get a new bag of nuruk make sure you check the SP!
Park, J.H.,Yeo, S.H., Choi, J.H., Jeong, S.T., Choi, H.S., 2012. Production of Makgeolli Using Rice Treated with Gaeryang-Nuruk (for Non-steaming Process) Extract. Korean J Food Preserv 19(1), 144-152.
Kim, H.R., Kim, J.H., Bai, D.H., Ahn, B.H., 2011. Identification and characterization of useful fungi with α-amylase activity from the korean traditional nuruk. Mycobiology 39, 278–282. doi:10.5941/MYCO.2011.39.4.278
Song, S.H., Lee, C., Lee, S., Park, J.M., Lee, H.J., Bai, D.H., Yoon, S.S., Choi, J.B., Park, Y.S., 2013. Analysis of microflora profile in Korean traditional Nuruk. J. Microbiol. Biotechnol. 23, 40–46. doi:10.4014/jmb.1210.10001