Caldas-Cueva J. P., Morales P., Ludeña F., Betalleluz-Pallardel I., Chirinos R., Noratto G., Campos D., Stability of Betacyanin Pigments and Antioxidants in Ayrampo (Opuntia soehrensii Britton and Rose) Seed Extracts and as a Yogurt Natural Colorant, Journal of Food Processing and Preservation, 2016, 40(3):541-549, doi: 10.1111/jfpp.12633
The experiments examine the stability of pigment extracts and the colouring of yoghurt. The authors compare the effects of pH, temperature, product matrix and storage time.