A Kinetic Study on the Formation of 2- and 3-Methylbutanal

2-Methylbutanal (2-MB) and 3-methylbutanal (3-MB) are highly volatile compounds and typical beer aging compounds. The development of a kinetic model of the formation of 2- and 3-MB is useful to estimate the wort flavor during the wort boiling and the flavor stability of beer. A model experiment was performed, using d-glucose/d-maltose and l-leucine/isoleucine to study Maillard reaction in a buffer solution of a pH value of 5.2. The simulated solution was heated at different time (0–360 min) and temperature (90–130 °C). The concentrations of d-glucose/d-maltose, l-leucine/isoleucine and 2- and 3-MB were determined by HPLC and GC. This kinetic model is based on the correlation between the concentration of 2- and 3-MB and the concentration of l-leucine/isoleucine. In this paper, the multistep formation method of 2-MB/3-MB is simplified to a three-step reaction. The kinetic parameters E_a, A and k were calculated for each reaction step. It was found that the formation of 2- and 3-MB has a sequence like this: GL > ML > GI > MI. The total activation energies for the formation of 2- and 3-MB are ranging from 107.87 to 178.88 kJ/mol. The developed kinetic model gives a good fit with the experimental data. This study is useful for the control of the wort quality during the boiling process and could also be interesting for food and beverage industries. Practical Applications: Maillard reactions are responsible for the formation of most wort flavors. In addition to this there exist intermediates, which lead to the development of off-flavors during shelf life. The 2- and 3-MB are the Strecker aldehydes and have typical wort flavors. Wort boiling is not only the midpoint of the brewhouse, it is also one of the most important steps in producing an excellent beer. The kinetic study of the formation of 2- and 3-MB is very useful for the control of wort boiling parameters. This result is helpful to calculate a suitable wort boiling time for different raw materials under brewing process conditions.