Assessment of the resistance of porcine diamine oxidase enzyme to temperature and pH

The diamine oxidase (DAO) enzyme is naturally produced by humans and allows histamine decomposition. However, when a deficiency of this enzyme exists intolerance or intoxication can occur. The goal of the work was to evaluate the conditions at which the DAO enzyme could be introduced in the processes of preparation of foods rich in histamine, as an alternative to the pharmacological approach. For that purpose, the enzymatic activity of the porcine diamine oxidase (DAO) was studied after treatments at different conditions of pH and temperature. The resistance to pH was analyzed by exposing the enzyme to pH 3, 5, 7, 9 buffer solutions for 1 hour, 7 days and 60 days at 4°C. The resistance analysis to storage temperature conditions was carried out by keeping the enzyme samples in a neutral buffer solution (pH 7.2) at ‐18°C and at room temperature (23±1°C) for 1 hour and 7 days. The resistance analysis at temperature conditions of thermal treatments was carried out by keeping the enzyme samples in a neutral buffer solution (pH 7.2) at 40°C, 60°C, 70°C and 80°C for 2 (only for 80°C), 5, 10, 15 and 20 minutes. The enzyme activity of untreated samples was also studied, in order to make comparisons between samples before and after any treatment. The experiments were conducted in triplicate, in each case. The average enzyme activity in terms of U (μmol of degraded histamine/min) and the residual enzyme activity (%) were estimated by a colorimetric method for each treatment. Statistical analysis were carried out in order to find significant differences between treatments and interactions between the factors. Results showed that the porcine DAO enzyme is only active in neutral or basic media and in these conditions its activity increases during time, specifically up to 60 days of storage at 4°C. Considering storage conditions in neutral buffer: the enzyme maintains its original activity if stored either at -18°C or at room temperature (23±1°C) up to one week of time. Finally, after thermal treatments in neutral buffer at 70°C and 80°C, the DAO activity decreases significantly. Whereas the DAO activity is enhanced at 40°C after 20 minutes of incubation. Consequent industrial practices should be set to guarantee the desired DAO preservation.