Effect of pH and Ionic Strength Modifications on Thermal Denaturation of the 11S Globulin of Sunflower (Helianthus annuus)

Abstract

Helianthinin, the main storage protein of sunflowers, has low water solubility and does not form a gel when heated; this behavior is different from other 11S globulins and limits its food applications. To understand this particular behavior, changes on helianthinin association-dissociation state induced by modifications in pH and ionic strength were analyzed. The influence of these different medium conditions on its thermal stability and tendency to form aggregates was also studied. Helianthinin behavior at different pH values and ionic strengths is similar to other 11S globulins except that it remains in a trimeric form at pH 11. Helianthinin thermal stability is higher than other 11S globulins but is lower than oat 11S globulin. Alkaline pH produces a 10 degrees C decrease of its denaturation temperature and also of the cooperativity of denaturation process, but it does not affect the denaturation activation energy. The decrease in thermal stability with the pH increase is also manifested by its tendency to form aggregates by SH/SS interchange reactions. When thermal treatments at alkaline pH are performed, all helianthinin subunits form aggregates, characterized by a higher proportion of beta-polypeptides than alpha-polypeptides, which is an indication that aggregation is accompanied by dissociation. Treatments at 80 degrees C are sufficient to induce aggregation but not to produce denaturation, and in these conditions hexameric forms remain after the treatment.

Sunflower storage proteins are transported in dense vesicles that contain proteins homologous to the pumpkin vacuolar sorting receptor PV 72

“…of electron dense aggregates starts to be observed in the ER (Figure 3a, arrows). This phenomenon has not been observed in other developing seeds such as soybean and can be related to the highest hydrophobicity and lower water solubility of sunflower 11S globulins (Molina et al 2004). In developing soybean cotyledons, in which expression of 7S globulins, that are highly soluble, is suppressed; unusual aggregation of 11S globulin is observed also in the ER (Mori et al 2004).…”

Physicochemical and structural properties of amaranth protein isolates treated with high pressure

“…Denaturation enthalpies (ΔH d ) and peak temperatures (T d in°C) were calculated from the corresponding thermograms (Universal Analysis V4.2E, TA Instruments, New Castle, Del., USA). Enthalpy values were expressed as J g − 1 protein, taking into account the dry weight (determined by perforating the pans and heating overnight at 105°C) and the protein content of sample (Molina, Petruccelli, & Añón, 2004). All assays were conducted in duplicate for each replicate.…”

A new way of valorizing biomaterials: The use of sunflower protein for α-tocopherol microencapsulation

“…Nevertheless, in recent years, interest in improving the production of phenolic free sunflower protein compounds has increased significantly (Pickardt et al, 2009;Salgado et al, 2012). This agricultural by-product with reduced phenolic component content could be useful for food applications because sunflower proteins, like soybean proteins, possess interesting functional and physico-chemical properties such as solubility, emulsifying, foaming and gelling capacities (Gonzalez-Perez & Vereijken, 2007;Gonzalez-Perez, Vereijken, Koningsveld, Gruppen, & Voragen, 2005;Molina, Petruccelli, & Anon, 2004;Patino et al, 2007).…”