Fouling by nanoscale roughness) allows for the

Fouling is a big problem in dairy pasteurization equipment. The heated milk and its derivatives generate mineral and proteinaceous deposits on stainless steel walls and increase the thermal resistance. These deposits are also a threat to the food safety due to micro-organisms and their cleaning process involves cost and time.The aim is to use biomimetic surfaces like lotus-like surface (dual-scale roughness) or Nepenthes pitcher plant inspired SLIPS (slippery liquid infused porous surfaces) on the stainless steel and test their fouling behaviours under the dairy processing conditions.Biomimetic surfaces inspired from the lotus leaf has self-cleaning abilities and their dual-scale roughness (i.e. a micro-roughness superposed by nanoscale roughness) allows for the particular suspended Cassie-Baxter wetting state due to air remaining trapped between the liquid and the solid surface. Those surfaces possess very high contact angles (higher than 150°) and very low contact angle hysteresis (less than 10°). However, their stability through time remains questionable as under certain environmental conditions, liquid is very likely to penetrate into the three dimensional structures, maximizing the solid/liquid contact area and degrading the surfaces’ self-cleaning properties. To overcome this limitation, impregnation of the lotus-like surfaces by a liquid of low surface tension (e.g. an inert oil, non-miscible to water) would be a possible solution. Indeed, the resulting interface would be similar to the one of SLIPS (Slippery Liquid Infused Porous Surfaces), which present a smooth and inert interface that would theoretically limit fouling.Native stainless steel (NAT) is used as a reference material. Texturing was carried out on this surface and Cauliflower-like structures was obtained after femtosecond laser ablation under certain laser fluence and scanning speed. The resulting samples is referred as TEX. To maximize oil retention on TEX surface, a fluorosilanization was performed by immersing TEX samples in a 10-3 M solution of trichloro-perfluorooctyl-silane (Sigma Aldrich) in n-hexane for 4 hours. Rinsing was done once in hexane, twice in dichloromethane and once in ethanol. This surfaces is called SilTEX. Slippery liquid infused surfaces (SLIPS) were obtained by pouring dropwise Krytox 103 oil (DuPont) on tilted SilTEX surfaces.Foul Test was carried out in a pilot-scale pasteurizer which is composed of two plate heat exchangers, one for preheating (from 20 to 65°C) and another for heating (from 65°C to 85°C) and they are connected to a storage tank. Sample milk with a flow rate of 300 l/h was circulated for one and a half hours and tested. This will help to investigate potential fouling properties of various surfaces.Next the wettability property is studied using the goniometer. Apart from that the dynamic analysis (contact angle hysteresis, roll-off and slide-off angles) can be evaluated. This method allows the calculation of total surface energy and of its different components due to dispersive interactions and acido-basic interactions. The surface roughness is studied using the Profilometer.Fouled samples are observed using Electron Probe Micro-analysis (EPMA)Goniometer provides the result of water contact angle, surface energy and roughness of native and modified stainless steel. Where ?Total Total surface energy; ?LW – due to dispersive interactions; ?AB – due to acido-basic interactions; ?+-the electron acceptor; ?- electron donor.Fouling density of the samples were determined by weighing them before and after the fouling test. They are then compared to the Native stainless steel. Below equation is used to calculate the fouling density.Where, F%: Fouling density compared to native stainless steel (-)MF: Fouling mass on the sample (mg)ref: Native stainless steel value S: Fouled surface (cm²)The below graph shows the fouling performance of the sample surfaces in comparison to the Native stainless steel.TEX sample with high surface energy and roughness promotes tremendously to the fouling growth, 391 wt.-% increase in the dairy deposit is observed. SilTEX samples show an increase of 86 wt.-% fouling weight when compared to native stainless steel. Whereas SLIPS-like structures have the most interesting results, they showed a reduction of 63% weight. This protein adhesion to the surface is avoided because of the oil impregnation. Fouling on NAT surfaces is dense and thick, whereas the deposits on SLIPS-like samples are large bubble-like structures. Another observation of SLIPS-like and native samples was after rinsing 20 minutes in water, there was no trace of fouling on liquid-infused SLIPS surfaces.The SLIPS surfaces with an inert, low surface tension oil, leads to an slippery surface which has proven to be a very efficient antifouling solution than the other materials. A simple water rinsing step was sufficient to remove all trace of dairy deposit.