Physicochemical properties of whey protein hydrolysates and their applications in infant formula

Whey protein hydrolysates (WPHs) play a pivotal role in infant formula development, offering enhanced functionality and nutritional benefits. WPHs produced using various enzymes were characterised and applied in infant formula model emulsions. This study aimed to fill the gaps in the current knowledge of the production and properties of WPHs, as well as the properties of their application in infant formulas. Real-time hydrolysis of whey protein isolate by bromelain was monitored using in-flow small-angle X-ray scattering (SAXS). Whey protein molecules were measured with an average size of ~ 20 Å. During hydrolysis, structural transformations including the conversion of globular whey protein isolate molecules into Gaussian polypeptides were examined. SAXS is a powerful tool to track protein hydrolysis dynamics and study structural modifications. WPHs produced via bromelain hydrolysis were investigated to stabilise infant formula model emulsions. WPHs with lower degrees of hydrolysis (< 10%) exhibited superior emulsion stabilisation, smaller oil droplet sizes, decreased viscosity and improved storage stability. The proteins/peptides (10 – 15 kDa) in WPHs could be adsorbed on the oil droplets and stabilise emulsions. Different WPHs prepared using various enzymes (trypsin, pepsin, bromelain, papain and flavourzyme) and their role in stabilising infant formula model emulsions were investigated. Unique peptide sequences with high expression on interfacial proteins/peptides in WPHs were identified, which strongly depended on their chain length (10 – 20), molecular weight, higher net charge, higher isoelectric point and amphipathy (positive hydrophobicity). These descriptions would offer insights for WPHs tailored in infant formula development. A novel technique, ultrasound pre-treatment, was used to assist with enzymatic hydrolysis of whey protein using different enzymes (trypsin, pepsin, bromelain and papain). The synergy enhanced hydrolysis efficiency, modified protein structures, and improved functional properties, as well as effectively reduced allergenicity of βlactoglobulin in intact whey protein. These findings were strongly associated with enzyme specificity. The enhancement of ultrasound-assisted enzymatic hydrolysis would be considered to apply in infant formula. Overall, the understanding of WPHs and their potential application in infant formula development would offer insights into optimising infant formula formulations.

Name thesis:degree_name

PhD

Level thesis:degree_level

Doctoral

Discipline thesis:degree_discipline

Food Science

Grantor dc:publisher

ResearchSpace@Auckland

Year dc:date.issued

2024

Author dc:creator

• Li, Jiecheng

Advisors dc:contributor.advisor

• Zhu, Fan
• Hartinger, Christian

Statement dc:rights

• Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated.

Licence dc:rights.uri

• https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm

Handle dc:identifier.uri

https://hdl.handle.net/2292/68436

OAI identifier oai:identifier

oai:researchspace.auckland.ac.nz:2292/68436