What chemical is necessary for the formation of MBT?

The formation of MBT, or 3-methyl-2-butane-1-thiol, is directly linked to the presence of 3-methyl-2-butane-1-thiol itself. This compound is a type of mercaptan that serves as a key contributor to certain off-flavors in beer, often described as a skunky aroma.

In the context of beer chemistry, the production of MBT typically involves the interaction of light with certain compounds in the presence of sulfur, which leads to the off-flavors commonly associated with beer that has been exposed to light. The other options provided do not contribute to the formation of MBT in the same way. Isohumulones are byproducts of the hops during the brewing process, riboflavin is a vitamin that does not play a role in MBT formation, and alpha acids are the bittering compounds from hops, which are unrelated to the thiol formation process related to skunky aromas.

Thus, 3-methyl-2-butane-1-thiol is the specific chemical compound at the center of this process, confirming it as the necessary chemical for MBT formation.