What biochemical change occurs during kilning involving S-methyl Methionine (SMM)?

The correct answer highlights the transformation of S-methyl Methionine (SMM) into Dimethyl Sulfide (DMS) during the kilning process in brewing. During kilning, the temperature increases, which activates processes that lead to the breakdown of compounds within the grain. SMM, a precursor found in malted barley, is particularly relevant because when subjected to heat, it converts into DMS, a compound that can impart a characteristic aroma and flavor to the beer.

This conversion is critical because DMS can contribute to the beer's overall sensory profile, influencing the perception of flavor and aroma. Understanding this biochemical change helps brewers manage flavor characteristics and optimize the sensory qualities of the final product.

In contrast, the other options do not pertain to the role of SMM in the kilning process. Protein conversion to starch, starch conversion to sugar, and alcohol formation from yeast involve different biochemical pathways and processes unrelated to the transformation of SMM to DMS, which is specifically related to the impact of kilning on flavor development in brewing.