3.4. UHPH effect on soya milk isoflavones
The content and composition of isoflavones in the UHPH-treated soya milks (mg/L) are shown in Table 3. Total isoflavones determined varied among samples from 149.42 mg/L in BP to 159.83–191.62 mg/L in UHPH-treated soya milks. Isoflavone content can vary depending on the variety of the soya bean and also of the obtaining process. Similar total isoflavone contents were found in soya milk by Prabhakaran and Perera (2006) in a pilot plant scale soya milks and by Chen and Wei (2008) in commercial soya milks. The total isoflavones in UHPH-treated samples was statistically higher than BP samples. A direct correlation between the total isoflavone determined and the intensity of the treatment applied (pressure and temperature) can be observed. Isoflavones are associated to soluble proteins and could be released when soya proteins are denatured, which occurs under pressure and temperature (Rickert, Meyer, Hu, & Murphy, 2004). This fact could explain why the total isoflavone content was higher when higher temperatures and pressures were applied to the UHPH-treated soya milk (Table 3).