Structural and compositional changes during UHT fouling removal-Possible mechanisms of the cleaning process
Journal article, 2019

Ultra-high temperature (UHT) treatment of milk forms a deposit or fouling in the processing equipment that is mineral-based with an enclosed protein network. This study addresses the fundamental mechanisms that control the removal of this deposit. For this purpose, the structural and compositional changes during the cleaning process have been studied. The structure analysis was performed with scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) on samples that were quenched at different stages of the cleaning process. It was found for acid cleaning that the mineral content is rapidly decreasing in the fouling layer as the cleaning continues, but there is still an intact protein structure with the similar thickness as the original fouling. For alkali cleaning, part of the protein structure was subsequently removed from the outside towards the stainless steel as a function of time, while the mineral structure was mostly remaining. The break-up of the organic network structure, which likely involves depolyrnerization of protein aggregates, were found to control the cleaning efficiency. The weakening of the protein network facilitates the removal of the UHT fouling layer during the acid cleaning step and allow for an efficient cleaning cycle. The chemical reactions that occur within the fouling layer between the hydroxyl ions and the protein network was modeled according to a depolymerization reaction and a mechanistic model of the cleaning process is presented.

Protein depolymerization

Fouling structure

Mineral deposit

Mechanistic model

Protein net-work

Milk fouling

Cleaning

Author

Carin Hagsten

Lund University

RISE Research Institutes of Sweden

Annika Altskar

RISE Research Institutes of Sweden

Stefan Gustafsson

Chalmers, Physics

Niklas Lorén

RISE Research Institutes of Sweden

Chalmers, Physics, Eva Olsson Group

Christian Tragardh

Lund University

Fredrik Innings

Tetra Pak

Lars Hamberg

RISE Research Institutes of Sweden

Marie Paulsson

Lund University

Tommy Nylander

Lund University

Food Structure

2213-3291 (ISSN)

Vol. 21 UNSP 100118

Subject Categories

Physical Chemistry

Materials Chemistry

Biophysics

DOI

10.1016/j.foostr.2019.100118

More information

Latest update

8/19/2020