Study of Whey Protein Adsorption under Turbulent Flow

Heat exchanger performance degrades rapidly during operation due to formation of deposits on heat transfer surfaces which ultimately reduces service life of the equipment. Due to scaling, product deteriorates which causes lack of proper heating. Chemistry of milk scaling is qualitatively understood and the mathematical models for fouling at low temperatures have been produced but the behavior of systems at ultra high temperature processing has to be studied further to understand in depth. In diversified field, the effect of whey protein fouling along with pressure drop in heat exchangers were conducted by many researchers. Adding additives, treatment of heat exchanger surfaces and changing of heat exchanger configurations are notable areas of investigation in milk fouling. The present review highlighted information about previous work on fouling, influencing parameters of fouling and its mitigation approach and ends up with recommendations for retardation of milk fouling and necessary measures to perform the task.

Biotechnology Progress, 1998

Adsorption kinetics of-lactoglobulin onto stainless steel at low concentrations were studied to determine adsorption rate constants for monolayer coverage. Experimental data obtained from a batch reactor were described quantitatively using a reversible adsorption model which becomes the Langmuir-type adsorption isotherm at equilibrium. The forward rate constant, k 1 , and backward rate constant, k 2 , were 10 5 mL g-1 min-1 and 5 × 10-3 min-1 , respectively. A high-performance liquid chromatographic system using a stainless steel column packed with stainless steel particles (column adsorption reactor) was also used to measure adsorption with a step change of-lactoglobulin solution. The difference in behavior of an adsorption and a desorption isotherm in this column adsorption reactor suggested surface denaturation of-lactoglobulin after adsorption which was consistent with other research work.-lactoglobulin adsorption in the column adsorption reactor was affected by volumetric flow rate and concentration up to 4 mL min-1 and 100 µg mL-1 , respectively.

Chemical Engineering Science, 2007

The influences of calcium concentrations (70.88 mg/l), Reynolds number and temperature (60.96 • C) upon the deposit structure and the rate of growth deposition have been investigated in a plate heat exchanger. This was done from in situ measurements of the deposit electrical conductivity via implementation of stainless steel electrodes in channels combined with assessments of deposit thickness. Calcium ions affect structures of deposits and increase the rate of deposit growth upon heated surfaces. This was attributed to the formation of weaker size aggregates at higher calcium concentrations and a higher number of calcium bindings, which reinforce adhesion forces between protein aggregates. Structures and appearances of deposits also were affected by flow rates whatever the calcium concentrations. Deposit growth rate was enhanced by increasing flow rate below a critical Reynolds number comprised between 3200 and 5000. On the contrary, above the critical Reynolds number, a limitation of the deposit and/or an escape of the deposit from the fouled layer into the core fluid occurred, caused by the predominance of particle breakage on the deposit formation. Fouling tended to be reduced at higher flow rate. It was noteworthy that rates of growth decrease during fouling experiments which may be explained by an increase in local shear stresses leading to particle breakage. ᭧

Journal of Food Research, 2012

In the cleaning operations of heat exchange surfaces in dairy processing plants, the effect of heating/run time (HT) and aging on the fouling/cleaning of heat exchangers is not well understood. Longer heating time of the same deposit is expected to result in the formation of stronger and perhaps more cleaning resistant deposit. In this study, the phenomenon of heating and aging on the formation and cleaning of dairy fouling is investigated using the heat induced whey protein gels (HIWPG) produced in laboratory. The processes were also investigated with the whey protein deposits formed in pilot-scale plant trails. The HIWPGs were produced in tubular capsules for various heating (or run) times (60, 120, 240, 1440 and 2880 min respectively) and then dissolved in aqueous sodium hydroxide (0.5 wt %). The heating process here would have been of 'pure' aging. The dissolution rate was calculated based on the previously established UV Spectrophotometer analysis. The structure and texture of the gels were analysed using Scanning Electron Microscope (SEM) and texture analyser. In the pilot-scale plant study, whey protein fouling layers were generated by recirculating whey protein solution (6 wt %) for various heating periods (30, 60, and 90 min respectively). The deposit layers were then removed by recirculating aqueous sodium hydroxide (0.5 wt %) and the cleaning efficiency was monitored in the form of the recovery of heat transfer coefficient while both fluid electric conductivity and turbidity were recorded as indications of cleaning completion. It was found that increasing the HIWPG heating time significantly increased the gel hardness and dissolution time, implicating the difficulty in cleaning. Similarly to these results on gels, increasing the pilot-scale plant heating/run time increased the extent of fouling. The fouling layer formed next to the metal surface experienced the longest period of aging and the slope of the heat transfer coefficient increase seen at the final cleaning stage is related to this aging effect. The rate of cleaning for deposits formed initially on the metal surface is lower indicating a 'pure' aging effect of the deposit near surface.

International Dairy Journal, 2008

The deposition behaviour of the main components of milk fouling (b-lactoglobulin and calcium phosphate) and its dependence on the surface energy properties of the fouling support were evaluated in this work. As deposition supports, several modified stainless-steel materials obtained by surface modification techniques were used. Four fouling systems were analysed: an aqueous solution that resembles the mineral composition of milk (simulated milk ultrafiltrate, SMUF), at 44 and 70 1C, and SMUF with addition of b-lactoglobulin at 50 and 85 1C. Both the final amount of deposits formed for each system on the different surfaces and the type of aggregates formed during the first stages of the process for each case were assessed. The number and size of the calcium phosphate aggregates initially formed can be used as a predictive approach to the final amount of deposit developed for each system since relationships between these parameters were established. r

Journal of dairy science, 2016

Fouling of plate heat exchangers (PHE) is a severe problem in the dairy industry, notably because the relationship between the build-up of protein fouling deposits and the chemical reactions taking place in the fouling solution has not yet been fully elucidated. Experiments were conducted at pilot scale in a corrugated PHE, and fouling deposits were generated using a model β-lactoglobulin (β-LG) fouling solution for which the β-LG thermal denaturation reaction constants had been previously determined experimentally. Then 18 different bulk temperature profiles within the PHE were imposed. Analysis of the fouling runs shows that the dry deposit mass per channel versus the ratio R=kunf/kagg (with kunf and kagg representing, respectively, the unfolding and aggregation rate constants computed from both the identification of the β-LG thermal denaturation process and knowledge of the imposed bulk temperature profile into the PHE channel) is able to gather reasonably well the experimental f...

Experimental Thermal and Fluid Science, 2007

In order to reduce milk fouling during heat treatment, several approaches have been evaluated and one of them, the modification of the surface properties of the stainless steel used in heat exchangers, is analysed in this work. Fouling behaviour of stainless steel surfaces (2R) and modified stainless steel-based surfaces obtained by TiN sputtering was analysed. The combined effect of b-lactoglobulin and the surface energy properties of the materials on the deposition behaviour of calcium phosphate was evaluated. The experiments were performed in turbulent flow regime in a heat flow cell where the fouling thermal resistance was continuously monitored. The presence of protein was responsible for changing the overall fouling curve independently of the surface nature, as well as for the appearance of two distinct growth periods. The second growth phase occurred after different delay times depending on the roughness, surface composition and surface energy values of the deposition material. The resistance to cleaning of the different deposits was also evaluated and it was proved to be dependent on the surface energy parameters, probably as a result of the formation of different deposit structures. The main conclusion is that when protein is present, the non-modified 2R surfaces present the lowest amount of deposit, but the higher energy surfaces are the ones to retain less amount of deposit after the cleaning process.

ACS Applied Materials & Interfaces, 2021

Molecular details concerning the induction phase of milk fouling on stainless steel at an elevated temperature range were established to better understand the effect of temperature on surface fouling during pasteurization. The liquid−solid interface that replicates an industrial heat exchanger (≤75°C), including four stages (preheating, heating, holding, and cooling), was investigated using both a quartz crystal microbalance (QCM-D) and a customized flow cell. We found that the milk fouling induction process is rate-limited by the synergistic effects of bulk reactions, mass transfer, and surface reactions, all of which are controlled by both liquid and surface temperatures. Surface milk foulant becomes more rigid and compact as it builds up. The presence of protein aggregates in the bulk fluid leads to a fast formation of surface deposit with a reduced Young's modulus. Foulant adhesion and cohesion strength was enhanced as both interfacial temperature and processing time increased, while removal force increased with an increasing deposit thickness. During cleaning, caustic swelling and removal showed semilinear correlations with surface temperature (T S), where higher T S reduced swelling and enhanced removal. Our findings evidence that adsorption kinetics, characteristics of the foulant, and the subsequent removal mechanism are greatly dependent on the temperature profile, of which the surface temperature is the most critical one.

Fouling of heat exchangers in dairy industries is still quite a severe problem both technically and economically. Altering the surface properties of the heating surfaces would be a way of solving this issue. Modified steel surfaces were tested in an Alfa Laval V2 plate heat exchanger throughout dairy product sterilization. The behavior was analyzed for 8 different surfacetreatments, such as coatings (Diamond Like Carbon [DLC], Silica, SiOX, Ni-P-PTFE, Excalibur®, Xylan®) and ion implantation (SiF+, MoS2). All fouling and cleaning experiments were carried out in standard and well-controlled operating conditions. After fouling, no significant difference could be seen between all the modified steels and the reference by statistical variance analysis. Cleaning efficiency of Ni-PPTFE appeared significantly the best. It could be suggested that the free surface energy plays a predominant role and the roughness a minor role in the level of fouling and cleaning efficiency.

Reviews in Chemical Engineering, 2000

Formation of deposits on heat exchanger surfaces during operation rapidly increases the thermal resistance and reduces the operating service life. Product quality is deteriorated by fouling, which causes reduction of proper heating. The chemistry of fouling from milk fluids is qualitatively understood, and mathematical models for fouling at low temperatures exist, but the behavior of systems at ultrahigh temperature processing is still not clearly understood. The effect of whey protein fouling on heat transfer performance and pressure drop in heat exchangers was investigated by many researchers in diversified fields. Among them, adding additives, electromagnetic means, treating of heat exchanger surfaces and changing of heat exchanger configurations are notable. The present review highlighted information about previous work on fouling, parameters influencing fouling and its mitigation approach.