Summary The effect of different technological practices on ulluco ( ullucus tuberosus ) and Opuntia dillenii has been scrutinised. Their stability at different pH s and temperatures of storage or processing over time was monitored. Our aim was focused on the determination of individual betalains and antioxidant activity, not previously conducted in conjunction with these raw materials. On the basis of the results, it could be asserted that the ullucus tuberosus and Opuntia dillenii were more suitable for being added to low‐acidic foods ( pH 5 and 6), in the light of the higher values of betalains and antioxidant capacity (1.3‐fold higher compared with pH 4). With regard to the temperature, cold storage conditions (4 °C) were optimal to increase or maintain as possible the initial content of betalains and antioxidant capacity. After cooking (80 °C), the identified betalains completely disappeared, but the low‐acidic conditions ( pH 6) favoured the greater antioxidant activity when kept at that temperature.