Surface engineering for cheese processing equipment

Abstract

As awareness of the environmental and health issues associated with PFAS materials production, the EU has encouraged industries to search for alternatives to traditional PTFE coatings. This thesis, conducted in collaboration with Tetra Pak as a part of PFAS free project, investigates surface engineering treatments for stainless steel used in cheese processing equipment. The goal is to identify replacements for PTFE coatings that maintain similar frictional and wetting properties under production relevant conditions.
Three primary surface treatments were studied: (i) pre-treatment (bead blasting, micro peening), (ii) post-treatment (electropolishing, passivation),and (iii) coatings (Nedox3k, CS1331, 3129ES). Surface roughness parameters were measured using Alicona, while friction tests were performed against rubber and cheese using a texture analyzer, under both dry and lubricated conditions. Wettability was measured by contact angle with distilled water.
Samples that has been pre treated by Bead blasting and post treated by electropolishing demonstrated the closest frictional performance to PTFE coated samples in dry contact conditions. When tested against cheese under wet conditions, samples that has been bead-blasted alone exhibited similar friction behavior to PTFE. The tests also revealed a relation between 3D Surface roughness parameter, reduced peak height (Spk) and coefficient of friction, while contact angle measurements to show all treatments remained hydrophilic.

Popular Abstract

PFAS (per-and polyfluoroalkyl substances) have been used in industrial applications for their exceptional non-stick and chemical-resistant properties. In cheese production, PTFE (a type of PFAS) is used to coat stainless steel surfaces to prevent cheese from sticking during processing. However, due to its toxicity and health concerns have led to EU planning to ban the production of PFAS. Therefore, this thesis was conducted to find an alternative. The goal of this thesis is to find an alternative to PTFE coating that would provide similar effect during cheese production.
The research was conducted in collaboration with Tetra Pak as a part of PFAS free project, involved testing 316 stainless steel samples treated using various combinations of surface engineering techniques. Pre-treatments of bead blasting and micro peening. Post-treatments of electropolishing and passivation. Alternative coatings, Nedox3k, CS1331, and 3129ES. Each treated samples had different pressures, media types and media sizes.
To understand the PTFE coating, surface characteristics of the machine surface in contact with cheese was studied by measuring surface roughness parameters, evaluating surface friction, and measuring surface adhesion (wettability). Friction tests were conducted in both dry conditions (against rubber) and wet conditions (against actual cheese with water as lubricant). Surface roughness was analyzed using 3D microscope, and contact angle were measured to assess hydrophobicity.
The results identified potential alternatives to PTFE In dry conditions, bead blasting combined with electropolishing producing coefficient of friction levels closer to PTFE-coated samples. In wet conditions using cheese, bead blasted surfaces only to provide the closets value to PTFE’s low-friction performance.
While PTFE surfaces were hydrophobic, all tested treatments were hydrophilic (contact angles less than 90°). Also, a correlation between a surface roughness parameter, reduced peak height (Spk) and the coefficient of friction, suggesting that the larger Spk the lower the coefficient of friction value.
For future work, studying friction not only from surface structure side, but also investigating surface chemistry and surface energy would be required. also testing these surfaces under actual cheese production temperatures (70–80°C).

• author: Khair, Duaa Musbah Abdalla Mohammed
• supervisor: Martin Adell
• organization: Production and Materials Engineering
• course: MMTM05 20251
• year: 2025
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: PFAS free, PTFE, surface engineering, product development, surface roughness, surface friction, surface adhesion, wettability, surface treatments, bead blasting, micro peening, electropolishing, passivation, stainless steel, hydrophobic surface, hydrophilic surface, coating, Spk, cheese friction, friction in dry condition, friction in wet condition
• report number: LUTMDN/(TMMV-5379)/1-50/2025
• language: English
• id: 9199915
• date added to LUP: 2025-06-16 15:49:50
• date last changed: 2025-06-16 15:49:50