Impact of Ultrasound Treatment and pH-Shifting on Physicochemical Properties of Protein-Enriched Barley Fraction and Barley Protein Isolate.

Nesli Sozer,Pia Silventoinen

doi:10.3390/foods9081055

Nesli Sozer, Pia Silventoinen

Open Access

https://doi.org/10.3390/foods9081055

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Abstract

Ultrasonication alone or in combination with a pH-shifting method could be applied as means for improving the techno-functional properties and performance of barley protein ingredients in liquid food matrix. Ultrasound technology was utilised with and without pH-shifting to 3, 7 and 9 aiming at investigating their impact on primary protein structure, protein solubility, particle size and colloidal stability of an air-classified protein-enriched barley fraction and a barley protein isolate. Shifting the pH of sample dispersion to 9 followed by neutralisation to pH 7 improved protein solubility and colloidal stability of the isolate whereas it had less impact on the protein-enriched fraction. Ultrasound treatment improved both protein solubility and colloidal stability of the protein-enriched fraction at alkaline pH and particle size reduction by ultrasonication was observed at all the studied pH-values. For protein isolate, ultrasonication improved protein solubility at all pH-values and colloidal stability was improved at acidic and neutral pH whereas the sample was inherently stable at alkaline pH. The protein profiles of both ingredients remained unaffected by ultrasound treatment. The results suggest adopting ultrasonication as a promising tool for improving applicability of barley protein ingredients in liquid food systems.

Highlights

Barley is a globally important crop, ranking fourth in production among cereals [1]
Air classification of the barley endosperm fraction resulted in protein enrichment from 8.3% in the raw material to 24.0% in the protein-enriched barley fraction (PEBF) (Table 1)
The impact was mainly due to the decrease in particle size as no impact on the primary protein structure was observed by SDS-PAGE analysis

Summary

Introduction

Barley is a globally important crop, ranking fourth in production among cereals [1]. Food use of barley ingredients, especially barley protein, is limited, as barley is mainly utilised for brewing or as feed. Considering the acute global challenges such as population growth and climate change, it is necessary to develop alternatives to animal-based proteins [2]. Plant-based proteins and ingredients provide a more sustainable option for food ingredients. Plant proteins are known to exhibit poor techno-functional properties, which hinder their applicability in food products [3]. Food use of barley proteins is restricted by their low solubility in water (9–29%) at food relevant pH ranging from 3 to

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