Hemp globulin forms colloidal nanocomplexes with sodium caseinate during pH-cycling

Chih-Chieh Chuang; Aiqian Ye; Skelte G Anema; Simon M Loveday

doi:10.1016/j.foodres.2021.110810

Hemp globulin forms colloidal nanocomplexes with sodium caseinate during pH-cycling

Food Res Int. 2021 Dec;150(Pt B):110810. doi: 10.1016/j.foodres.2021.110810. Epub 2021 Nov 16.

Authors

Chih-Chieh Chuang¹, Aiqian Ye², Skelte G Anema³, Simon M Loveday⁴

Affiliations

¹ Riddet Institute Centre of Research Excellence, Massey University, Private Bag 11 222, Palmerston North, New Zealand. Electronic address: c.chuang@massey.ac.nz.
² Riddet Institute Centre of Research Excellence, Massey University, Private Bag 11 222, Palmerston North, New Zealand.
³ Riddet Institute Centre of Research Excellence, Massey University, Private Bag 11 222, Palmerston North, New Zealand; Fonterra Research and Development Centre, Private Bag 11029, Dairy Farm Road, Palmerston North 4442, New Zealand; School of Food and Advanced Technology, Massey University, Private Bag 11 222, Palmerston North, New Zealand.
⁴ Riddet Institute Centre of Research Excellence, Massey University, Private Bag 11 222, Palmerston North, New Zealand; Smart Foods Innovation Centre of Excellence, AgResearch Limited, Private Bag 11008, Palmerston North 4442, New Zealand.

PMID: 34863500
DOI: 10.1016/j.foodres.2021.110810

Abstract

Seed from industrial hemp (Cannabis sativa L.) contains around 25% protein (mainly globulins) which is easily digested, but the low solubility of hemp globulins (HG) limits their application in many food systems. In this study, the solubility of HG was improved by blending HG with sodium caseinate (SC) and treating with a pH-cycling process. The pH-cycling involved adjusting the pH to 12 and reacting for 1 hr, followed by neutralisation to pH 7. Nanoparticles composed of HG and SC (Z-average diameter ≈ 130 nm) were formed after the pH-cycling, and the solubility of HG increased to > 80% when there was more than 1% of SC for 1% of HG. These HG|SC nanoparticles were monodisperse (PDI < 0.17) and ζ-potential was ≈ -17 mV. Hydrogen bonding is the main forces that assembles HG|SC nanoparticles because the nanoparticles dissociated by heat treatment (up to 60 °C) or urea, which is an effective hydrogen bond breaker. HG|SC nanoparticles will aggregate irreversibly above 60 °C, possibly due to thiol-disulphide exchange. The nanoparticles were heat-stable as the Z-average diameter was only 229 nm after heating (90 °C, 30 min). N-ethylmaleimide blocked free thiol groups on HG and resulted in less disulphide-linked HG aggregation after pH- cycling, which in turn lead to smaller HG|SC nanoparticles and a bimodal particle size distribution, indicating the importance of disulphide bond for the formation of monodisperse HG|SC nanoparticles. The soluble and heat-stable HG|SC nanoparticles could be used to increase the hemp protein content in beverages and emulsions.

Keywords: Casein; Hemp protein; Protein functionality; Protein nanoparticles; Protein–protein interactions; Solubility; pH-cycling.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Cannabis*
Caseins
Globulins*
Hydrogen-Ion Concentration

Substances

Caseins
Globulins