Effect of pH and NaCl on the Emulsifying Properties of a Napin Protein Isolate

Abstract

The physicochemical and emulsifying properties of a napin protein isolate (NPI) were examined as a function of pH (3.0, 5.0 and 7.0) and NaCl content (0, 50 and 100 mM). Specifically, surface charge and hydrophobicity, interfacial tension (IT), solubility, and the emulsifying activity (EAI) and stability (ESI) indices were studied. Surface charge in the absence of NaCl ranged between~+10 mV to~−5 mV depending on the pH, becoming electrically neutral at pH 6.6. Overall, surface hydrophobicity decreased as the pH increased, whereas it increased as NaCl levels were raised. Solubility was high (~93-100 %) regardless of the conditions. NPI's ability to reduce IT was enhanced at higher pHs, however the effect of NaCl was pH dependent with the addition of NaCl enhancing and decreasing NPI's ability to reduce IT at pH 3.0 and 7.0, respectively. Overall, EAI values were similar in magnitude at pH 3.0 and 5.0, and lower at pH 7.0. The effect of NaCl on EAI was similar at pH 3.0 and 7.0, where EAI at the 0 mM and 100 mM NaCl level were similar in magnitude, but increased significantly at the addition of 50 mM NaCl. However, the EAI values at pH 5.0 decreased as the level of NaCl increased. Overall, the stability of NPIstabilized emulsions degraded rapidly and the addition of salt induced faster emulsion instability.

Canola/rapeseed protein-functionality and nutrition

“…Presence of phytates in canola protein isolate composed of cruciferin and napin (70% globulin, 30% albumin and ∼1% phytic acid) may cause stable electrostatic protein-phytate complexes thus reduces surface activity of protein molecules (Krause and Schwenke, 2001) and enhance interface stabilization. Working with somewhat pure protein, Wu and Muir (2008) and Cheung et al (2014) showed cruciferin (>80% purity) possesses better emulsifying ability than napin (Cheung et al, 2015). Wijesundera et al (2013) demonstrated that canola protein extracted at alkaline pH (12) and recovered by precipitating at pH 6.5 can stabilize O/W emulsions.…”

Multi-Response Optimization in the Formulation of a Topical Cream from Natural Ingredients

“…However, there is an increasing consumer demand for more natural, environmentally friendly, and sustainable commercial products [7]. Many manufacturers are reformulating their products to replace the synthetic surfactants with more label-friendly natural alternatives [8] or to replace animal proteins from with plant proteins [9,10]. Generally, manufacturers would often like to create new products entirely from natural ingredients so that they can make "all-natural" claims on their labels.…”

Solubility of a cruciferin‐rich protein product purified from rapeseed pressed cake (Brassica napus L.) by an aqueous processing method

“…) and due to the innate behaviour related to the process set‐up. Enhanced solubility of NRP by the addition of NaCl is not expected, as also previously described in literature (Cheung et al ., ). NRP has therefore not been further examined in this study.…”

“…(), reporting that varying solubility at similar pH values is found. Different laboratory‐scale studies have analysed the possibility to enhance the solubility of rapeseed protein by, for example, partial hydrolysis (Vioque et al ., , ) and the addition of NaCl (Cheung et al ., , ).…”