Combined adjustment of pH and ultrasound treatments modify techno-functionalities of pea protein concentrates

Abstract

Plant proteins, and particularly pea proteins, have become more and more crucial as ingredient for food industries, due to ecological concerns, health benefits and even religious reasons. Although literature reports addressing the use of high intensity ultrasound (HUS) to improve tecnho-functionalities of pea proteins at different pH can be found, such studies involved HUS power/time combinations corresponding to different total energy inputs. In this manner, it is still unclear if HUS energy rates received by proteins have an effect on their techno-functional properties, rather than the total energy. To shed light on this question, here we studied the effects of HUS energy rates on pea protein concentrates (PPCs), treated according to the HUS power/time binomials: 412.5 W/581.82 s, 487.5 W/492.31 s, 562.5 W/426.66 s, 637.5 W/376.47 s, 712.5 W/336.84 s (total energy input constant = 240 kJ), with pHs adjusted to 2.8, 4.3, 6.8, and without pH adjustment. None of the HUS/pH tratments harmed the in vitro diggestibility of PPCs, suggesting that proteins were nutritionally preserved. For all physicochemical properties assessed, different HUS power/time binomials triggered different results, at a given pH, indicating that the energy application rate may be indeed relevant for PPC ultrasonic processing. It is noteworthy that when using the HUS treatment 562.5 W/426.66 s, at pH 6,8, the emulsifying properties of PCC were greatly improved. On the other hand, whatever the HUS treatment, at pH 2.8, PPCs had both higher water dispersibility and better emulsifying properties. Weaker techno-functionalities were evidenced for PPCs at pH 4.3, although slightly differences due to different HUS power/time binomials were observed. All these results were detailed, discussed, and explained based on differences of exposed proteins’ hydrophobic surfaces, free -SH groups, dispersibility, ζ-potential, and average hydrodynamic diameters of protein particles in aqueous dispersions, submitted to different combined pH/HUS treatments.