Pineapple fruit bromelain affinity to different protein substrates

► Optimum conditions for fruit bromelain activity on five substrates were determined. ► Optimum activity at 55 °C and pH 7.5 for azoalbumin and 6.5 for azocasein was obtained. ► Bromelain activity on casein and sodium caseinate shown optimum at 59 °C and pH of 7.7 and 6.5 respectively and pH 2.9 and 37 °C for haemoglobin. ► Azoalbumin and azocasein are the most recommended substrates for the enzyme evaluation due to their kinetic behavior. ► Results obtained show a new assay technique for the standardization of enzymes preparations and the measurement of enzymatic activities.