The aim of this study was to test whether it is possible to estimate the heat stability of Aspergillus oryzae alpha-amylase (a-amylase) based on the amount of hydroxyl (OH) groups provided in a buffer solution. The thermal stability of the enzyme in a presence of different sugars (sucrose and trehalose) and polyols (mannitol, sorbitol, lactitol and glycerol) was investigated in the temperature range of 62-68C on a kinetic basis. It was investigated if the protective effect of additional substances was correlated to the number of hydroxyl groups (nOH) provided by each of them (per volume unit of the enzyme solution nOH). All additives showed a protective effect on the enzyme's heat stability, which was strongly dependent on the added compound concentration. Among all stabilizing compounds investigated, sucrose exhibited the largest protective effect. The decimal reduction time of a-amylase activity increased by 33.9 times when 420 mg/mL of sucrose was added to the environment. When the same concentration of trehalose was used, the D-value increased by 6.4 times compared to the value in the buffer system. The nOH provided in the enzyme solution could not be related to the D-values for the enzyme thermal inactivation, meaning that the enzyme heat stability was not dependent on the nOH.