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Study of heat-denatured whey protein removal from stainless steel surfaces in clean-in-place systems
Abstract
The build-up of protein deposits over the inner surfaces of process equipment, particularly heat exchangers, is a common phenomenon in dairy factories, which hinders the normal functioning of such equipment. In this work, we have studied the washing process of stainless steel surfaces stained with heat-denatured whey protein. To do that we have used the bath-substrate-flow (BSF) device, a bench-scale apparatus that simulates clean-in-place systems. Screening tests were performed at low temperature (30 °C) to investigate the effect of the presence of protease, NaOH, ozone and surfactants on cleaning efficiency. The best results were obtained with NaOH (0.5%, w/w), proteases (1 g L-1) and ozone (40 NL h-1, 80 g Nm-3). On the other hand, the use of surfactants (either anionic or nonionic) did not improve the washing efficiency significantly. Therefore, ozone and proteases can be used as environmentally friendly cleaning agents to remove protein deposits in the food industry.
... This process consumes time and energy and the wastewater generated can produce an important impact on the environment [11]. Various investigations have included ozone in cleaning protocols with the aim of minimizing the environmental impact, but they have made no significant improvement in the detergency obtained with highly alkaline solutions [12]. ...
... The highest value of detergency is obtained with NaOH solutions (pH 13) without surfactants, reaching 11.8 ± 1.3%. Following the operating conditions of Bird and Fryer [39], Jurado-Alameda et al. [12] cleaned heat-denatured whey proteins in the BSF device using NaOH solutions (0.05-1% w/w) at 30 °C with a flow rate of 30 L/h. They obtained an optimal detergency value with NaOH 0.5% (w/w), an alkaline concentration very similar to that used in this work. ...
... Aqueous solutions containing bubbles have been evaluated for cleaning efficacy in the removal of protein model contaminants (bovine serum albumin and lysozyme) from surfaces and in the prevention of the fouling of surfaces by these same proteins, proving that nanobubbles can prevent the fouling of surfaces and that they can also clean already fouled surfaces [36,40]. However, the heat-denatured whey protein cleaning efficiency obtained in the electrocleaning device does not significantly improve that obtained with cleaningin-place systems [12]. Protein soils are notably difficult to remove and their alkali-based cleaning process is very sensitive to temperature and hydraulic effects [41] requiring harsh conditions to obtain satisfactory results. ...
Electrocleaning was used in the cleaning of food soils (starch and heat-denatured whey protein) adhered to stainless steel. The influence of anionic (linear alkylbenzene sulfonate, two polyoxyethylene lauryl ether carboxylic acids) and nonionic (fatty ethoxylated alcohol, alkylpolyglucoside, two polyoxyethylene glycerin esters) surfactants on detersive efficacy has been assessed. High levels of detergency (88.9%) were obtained when starchy dirt was used, doubling in some cases the washing efficiency achieved by cleaning-in-place methods. All the surfactants studied improved the detergency results with respect to that obtained with pH 13 solutions. However, when a denatured and dried whey protein was used, the electrocleaning method did not substantially improve detergency results, obtaining the highest detergency with 1 g/L alkylpolyglucoside at 60 °C (19.3%).
Graphical Abstract
... Ozone has also been extensively utilised for the removal of food residues from various surfaces encountered in the food processing industry, particularly because ineffective cleaning processes, may lead to the formation of biofilms on food equipment surfaces [10]. The removal of heat-denatured whey protein concentrates on stainless steel coupons was demonstrated using ozonated water (40 NL/h, 80 g/Nm 3 , 30 min) in the work of Jurado-Almeda et al. [135] It is worth mentioning that the application of aqueous or gaseous ozone for food processing depends on the type of food and the purpose of storage; nonetheless, the increased stability of ozone in the gaseous phases makes it somewhat preferrable. The interested reader is referred to the following critical reviews [17,43,124,[136][137][138][139] for an expanded discussion on this subject. ...
Ozone – a powerful antimicrobial agent, has been extensively applied for decontamination purposes in several industries (including food, water treatment, pharmaceuticals, textiles, healthcare, and the medical sectors). The advent of the COVID-19 pandemic has led to recent developments in the deployment of different ozone-based technologies for the decontamination of surfaces, materials and indoor environments. The pandemic has also highlighted the therapeutic potential of ozone for the treatment of COVID-19 patients, with astonishing results observed. The key objective of this review is to summarize recent advances in the utilisation of ozone for decontamination applications in the above-listed industries while emphasising the impact of key parameters affecting microbial reduction efficiency and ozone stability for prolonged action. We realise that aqueous ozonation has received higher research attention, compared to the gaseous application of ozone. This can be attributed to the fact that water treatment represents one of its earliest applications. Furthermore, the application of gaseous ozone for personal protective equipment (PPE) and medical device disinfection has not received a significant number of contributions compared to other applications. This presents a challenge for which the correct application of ozonation can mitigate. In this review, a critical discussion of these challenges is presented, as well as key knowledge gaps and open research problems/opportunities.
... • Ozone can remove fats (Jurado-Alameda et al., 2012a), proteins (Jurado-Alameda et al., 2014), and starches in cleaning processes. ...
Chemical and food industries are focusing on reducing the economic and environmental impact of cleaning operations. This study aims to analyse the use of alkaline ozonated formulations to remove starch adhering to stainless steel surfaces, improving disinfection of mature biofilms with Listeria and Pseudomonas, and reducing the environmental impact of wastewater. Three key cleaning parameters have been analysed in a lab-simulated Clean-in-Place system (CIP): temperature (20-60 °C), time (20-120 min), and cleaning formulations containing ozone and surfactant (linear alkylbenzene sulfonate, alkylpolyglucoside, fatty ethoxylated alcohol, lauramine oxide) were assayed. Higher temperature, time, and ozone concentration improved starch removal and disinfection of the stainless-steel surfaces, as well as the environmental impact of cleaning wastewater. Therefore, ozone-based CIP protocols could provide new opportunities to achieve cleaner, greener, and safer industries by intensifying cleaning, disinfection, and wastewater treatment in one step, saving operational costs compared to conventional CIP techniques.
... To study the influence of NaOH on WPG, the freshly produced samples were treated with NaOH solution. For the removal of protein deposit, the optimum concentration of NaOH was found to be 0.5 wt% in recent studies (Mercadé-Prieto and Chen, 2006;Mercadé-Prieto et al., 2007b,a, 2008bJurado-Alameda et al., 2014). The softening effect of NaOH is dominated by a chemical reaction rate. ...
To investigate the influence of chemical degradation on the mechanical (failure) behaviour of whey protein gels (WPGs), tensile and tensile relaxation experiments were performed on untreated and chemically treated gels. From each treatment performed, the tensile stresses increase with the applied strain rates, varying from 0.5%/s to 2.0%/s, indicating the time-dependent mechanical property of WPGs. Using sodium hydroxide solution with a concentration of 0.5wt% showed a clear chemical degradation effect at higher immersion time, resulting in reduced tensile strength due to softer mechanical response and increased stress relaxation, making the WPG more flowable. Comparing the failure behaviour between untreated and 3.0 min treated WPG, the untreated gels show a brittle failure behaviour and exhibit a lower failure strain than the adequately treated ones. The measured failure strain can be used to predict the cohesive failure of WPG subject to the same chemical degradation. The stress-strain relationships, responding to different experimental conditions, provide useful input data for modelling the mechanical behaviour of WPG associated with the chemical damage of the protein network.
... As indicated by the aftereffects of Compound Oxygen Request (COD) estimations, ozonated water expelled 84% of milk buildups from plates, though the non-ozonated warm water treatment evacuated just 51% of dairy soil materials. Also, [56,57] considered the reasonableness of ozone for expulsion of warmth denatured whey proteins from hardened steel surfaces. Both fluid and vaporous ozonation encouraged whey protein desorption. ...
... The chemistry of a particular soil also determines the fluid that should be used for cleaning. Enzymes are excellent cleaners for starch and protein deposits and can be used instead of highly alkaline solutions where they provide environmental and economic benefits (Antony et al., 2014;Jurado Alameda et al., 2014, 2015. Amylases are part of laundry and automatic dishwasher detergents for cleaning up starch residues from foods such as custard, gravy or potato (Gurung et al., 2013). ...
The cleanability of food contact materials is, among others, determined by the physico‐chemical properties of the soiling material. In the current study, starch of different origin was gelatinised and partially hydrolysed with diastase. The degree of hydrolysis was determined as the reducing capacity in terms of dextrose equivalents, and by the changes in apparent viscosity and surface tension. After spreading the starch paste on electropolished stainless steel coupons and subsequent drying, the removal was studied with a laboratory flow cell. These cleaning tests revealed a higher cleaning effectivity for smaller dextrins, which can be attributed to corresponding changes in solubility. Furthermore, the addition of commercially available diastase to demineralised water increased the cleaning effectivity of starch and dextrin soils at 25 °C. The results indicate that smaller starch breakdown products require reduced energy for removal so that cleaning processes can be adequately adjusted.
... Protein soils are relatively easy to remove; nevertheless, when proteinaceous deposits are submitted to typical operations in the food industry such as drying, ageing, or heating, coagulation appears, hindering the penetration of the cleaning formulation (Herbots et al., 2008). In these cases, proteases have proved to be an effective cleaning agent, being able to replace NaOH as a regular ingredient in industrial cleaning (Grasshoff, 2002;Jurado-Alameda et al., 2014). On the other hand, ␣-amylases are the most used type of carbohydrases in detergent industry. ...
An α-amylase and a protease suitable to be used as detergent additives in Cleaning-In-Place processes in the food industry have been studied in terms of their stability during storage as well as under washing conditions. Enzymatic solutions have been prepared with addition of two non-ionic surfactants at the pH of operation, an amine oxide and an alkylpolyglucoside. Activity assays have been carried out in order to obtain deactivation kinetics. The study of stability at storage during 21 days at 40 °C and 60 °C reveals that the enzymatic solutions in the absence of surfactants preserve their activity for longer. The protease showed to be more sensitive to thermal deactivation, undergoing a complete loss of activity at 60 °C before 24 h in all solutions studied. On the other hand, activity assays have been carried out at concentrations, time and temperature values usually found during cleaning processes of hard surfaces. The presence of the alkylpolyglucoside showed to preserve enzymatic activity of α-amylase at all temperatures assayed. The amine oxide, nevertheless, seemed to contribute to α-amylase deactivation and did not have a significant effect on protease. The results of this work suggest the need of stabilize enzymes in detergent formulations even when they do not contain potential denaturants.
... According to the results of chemical oxygen demand (COD) measurements, ozonated water removed 84% of milk residues from plates, whereas the nonozonated warm water treatment removed only 51% of dairy soil materials, but the two values did not differ significantly (P > 0.05). Similarly, Fukuzaki (2006) and Jurado-Alameda et al. (2014) studied the suitability of ozone for removal of heat-denatured whey proteins from stainless steel surfaces. Both aqueous and gaseous ozonation facilitated whey protein desorption. ...
Ozone treatment is a cost-effective and eco-friendly food-processing technology. It has successfully been used for the removal of milk residues and biofilm-forming bacteria from stainless steel surfaces and in milk processing, including fluid milk, powdered milk products and cheese. Ozonation has been shown to prevent mould growth on cheese and inactivate airborne moulds in cheese ripening and storage facilities. Ozone treatment has also been found to be a promising method for reducing the concentrations of pollutants in dairy wastewaters.
Biofilms generated during production of dairy/whey powders can cause contamination, spoilage and equipment failures, posing a significant challenge in the agri‐food sector. Factors including temperature, protein composition, equipment structures and surface topography influence biofilm formation and resistance to cleaning and sanitation. Several species of bacteria are well adapted to these challenges, posing the most pressing concerns of dairy whey process. Despite efforts to improve cleaning‐in‐place strategies, bacteria persist in difficult‐to‐clean areas. This review provides insights into bacterial biofouling in dairy protein powders, highlighting the mechanism of biofilm formation, predominant bacterial genera, critical processing steps and strategies to manage biofilm formation during the manufacturing process.
Improving the storage life of food products is a major problem for manufacturers, and the food sector needs an "ecofriendly" alternative to present technology. As a disinfectant, ozone has been utilized in waste-water purification systems since the beginning of the century. Recently, ozone has been utilized to handle a wide variety of agricultural products because of its qualities, including fast disintegration and low residual consequences during food preservation. Ozone is an interesting substitute preservative that the food industry demands and a suitable decontaminator for guaranteeing the microbiological hygiene and safety of food products. Ozone treatment has been demonstrated to be a potential strategy for lowering pollutants in dairy effluents. This review comprehensively highlights ozonation as a preservative in dairy, fruits and vegetables, poultry, cereals, and fresh produce in depth for save and effective use of ozone, whereas other published articles only discuss one of these categories. Overall, ozone has proven to be a viable technique, despite its high food-preservation efficacy, and market certification requires extensive information on the applicability of ozone-based technologies and their potential benefits.
The growing use of ozone (O3) in the last years to clean and enhance the physicochemical properties of starches, widely used as additives in food, beverage, and pharmaceutical industries, calls for a better understanding of their oxidation process. High pH, however, decomposes O3 rapidly, forming highly-oxidant radicals, thus increasing the complexity of the reaction system. In this study, a kinetic model for the ozonation reaction of starch in an alkaline medium was developed and experimentally validated. Firstly, the concentration of hydroxyl radicals (●OH) over the reaction time is evaluated through the degradation of pCBA (a probe compound) to later evaluate and model the oxidation process of starch based on Chemical Oxygen Demand (COD) measurements. By using a semi-batch reactor containing alkaline solutions at pH = 13, different O3 concentrations (0–42.30 g/Nm³) and temperatures (20–60 °C), a pseudo first-order kinetic model was proposed to model the pCBA-ozone reaction. This model estimates the ●OH formation, being [●OH] constant and proportional to the O3 continuous dose. Therefore, under the conditions studied, ●OH is a non-limiting reactant independent of temperature. The activation energy was estimated at 14.2 ± 2.1 and 14.5 ± 0.6 KJ/mol for 21.15 and 42.30 gO3/Nm³, respectively. Then, COD data were used to propose a kinetic model for ozone-starch oxidation in alkaline media, where besides O3 concentration and temperature, starch concentration (600–1700 mg/L) was also varied. According to the results, higher temperatures and longer reaction times resulted in a greater COD reduction, being it more pronounced at lower initial starch concentration. The activation energy of the ozone radicals-starch reaction was estimated at 8.1 ± 0.4 KJ/mol, being significantly lower than those reported for the reaction between pCBA and ●OH.
In the dairy industry, effective cleaning-in-place (CIP) is essential to maintain production efficiency and ensure food quality, safety, and shelf life. CIP is generally undertaken using sodium hydroxide solution or formulated caustic detergent at 70°C–80°C and is associated with significant energy and water consumption. The use of enzymes for CIP could potentially reduce the environmental impact of CIP as enzymes can work at low temperatures, are biodegradable, and reduce chemical usage and the resulting wastewater is more suitable for wastewater treatment processes. This chapter outlines the potential use of enzymes for CIP in dairy processing and associated advantages. Studies reported to date on using enzymes for removal of both milk fouling deposits (Type A) formed during heat treatment of milk and biofilms are discussed and important factors for consideration in the development of enzyme-based CIP to achieve optimum cleaning performance are highlighted.
Ozonation of cornstarch at pH 13 was performed using a semi-batch reactor to analyse the influence of a continuous ozone-oxygen gas flow (40 NL/h) at different ozone concentrations (0-42.30 g/Nm3) and temperatures (20-60ºC). A pseudofirst-order kinetic model was proposed to elucidate the reaction mechanisms associated with ozone at high pH conditions. The radical concentration remains constant and proportional to the ozone continuous dose, being a non-limiting factor independent of temperature (activation energy 14.2-14.5 KJ/mol). The oxidation kinetic of starch was studied monitoring the Chemical Oxygen Demand, finding a reduction in ozone concentration when both temperature and time increased (activation energy 8.1 KJ/mol). Therefore, the model proposed for the starch ozonation at high alkaline solutions provides a better understanding of the oxidation processes of common product additives such as starch, also making it possible to determine the environmental impact of such solutions by Chemical Oxygen Demand measurement.
Postprint: https://hdl.handle.net/10481/87845
To study the mechanical behaviours of protein deposits and its surrogate materials, various heat treatment was carried out on raw milk and whey protein solution to produce the samples for different mechanical experiments. Therein, milk and whey protein deposits generated from fouling experiments were mechanically characterised using indentation experiments, considering their complicated geometry and the irregular distribution on the heating plates.
Ozone is a powerful oxidant and, therefore, a promising agent in food processing since it is an effective agent for many food products by its high reactivity, penetrating ability and leaving non-toxic O2 as process by-product. Ozone has given a generally recognized as safe status by the United States Department of Agriculture (USDA) in 1997 for use as sanitizer in foods. Common examples of ozone treatments in the food industry include surface hygiene, sanitation of plant equipment, reuse of waste water, disinfection of poultry carcasses, improving shelf-life of fruit and vegetables and providing hygienic conditions in storage atmosphere of cereals. Oxidation process with ozone can be very complex thus leading to the formation of primary high reactive species. Ozonation works without any need for thermal energy and thereby saving energy. Also, since ozone is generated on-site at the time of use, there would be no need for transport and storage of any chemicals or reagents, therefore, reducing the total cost of operation at the industrial scale. In this context, ozone can be regarded as a green and environmentally friendly process. In this chapter, the use of ozone in the food processing will be discussed with an emphasis on the meat, cereals, dairy, fruits and vegetables and packaging industries. It is believed that this chapter will be useful for the researchers and the people working in the food industry.
Cleaning operations are performed regularly throughout the food industry. This review focuses on the removal of strongly adherent fouling deposits which compromise the performance and hygienic status of equipment and processes. Identifying and understanding the key mechanisms involved in cleaning food deposits is essential for selecting and optimising cleaning protocols. The complexity of these materials has prompted the use of model soil-surface systems for experimental investigations of cleaning. The factors that need to be considered in selecting model soil systems, the techniques used to measure and characterise cleaning, and the formulations that have been used to model food fouling deposits are discussed. Particular focus is given to deposits formed from liquid foods high in protein, starch, sugar and lipids. Biofilms, fouling layers generated in membrane operations and corrosion fouling are not considered.
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 stain-less steel as a function of time, while the mineral structure was mostly remaining. The break-up of the organic network structure, which likely involves depolymerization 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.
For efficient decomposition of dibutyl phthalate (DBP) in goat whey solution, we are using ozone (O3), ozone with zinc oxide (O3/ZnO), and ozone with zinc oxide and activated carbons (O3/ZnO/ACs) systems through catalytic ozonation process. The performance and efficiency of system were evaluated. The results showed that ozonation of sample using O3/ZnO/ACs system was found to be the most efficient for the DBP degradation. A maximum DBP degradation value of 99.04% was achieved after ozonation of whey solution using O3/ZnO/ACs system at O3 dosage 15 mg/L, pH 4, and 80 min. The ozonation treatments did not result in significant changes in protein, lactose, and ash content of whey (P > 0.05), while the fat content of whey decreased after ozonation. The results indicated that catalytic ozonation using O3/ZnO/ACs system can be suggested as an efficient process for the removal of DBP from contaminated whey and dairy products to prevent potential adverse health effect.
The effects of churning with different concentrations of ozonated water (OW) on fat particle size, texture, oxidation, melting and microbiological characteristics of butter from raw cream were investigated. For this purpose, butter samples were produced by churning with ozonated waters at concentrations of 0 (control), 0.15 (OW-15), 0.20 (OW-20), 0.25 (OW-25) and 0.30 (OW-30) mg L⁻¹. Churning with OW increased the lightness and redness value of samples and decreased yellowness. Firmness value of samples ranged from 126.86 to 347.46 N, with an increase with ozone concentration. Mean fat particle size (D[4.3]) value of samples decreased with higher ozone concentration in churning water. OW reduced the oxidative stability of samples. Microbial reductions by churning with ozonated water ranged from 0.07 to 1.59 log. Microbiological analysis results showed that ozone treatment improved the microbial safety of butter samples produced from raw cream.
An electrocleaning device was used to study the cleaning of dried starch adhered to stainless steel. Different cleaning parameters such as voltage, temperature, cleaning time, pH of the washing solution, polarity and previous wetting time were studied in relation to cleaning efficiency. Optimal cleaning conditions, according to energy savings and cleaning efficiency criteria, were determined: 20 °C, NaOH aqueous solution (pH 13), soiled substrate connected to the cathode, direct current voltage of only 5 V and 20 min without a previous wetting time. Under these conditions, the detergency found for cleaning difficult-to-remove dry starch was 65.7 ± 3.4%. The detergency found by electrocleaning was 52% higher than without current. High detergency results were achieved in the electrocleaning device using lower temperature and less time than those normally used in the food industry.
A unique dispositive to determine casein which is the most abundant protein in dairy sewages has been proposed. In this sensing technology, the derivatization reagent 1,2-naphtoquininone 4-sulphonate (NQS) is embedded into a polydimethylsiloxane-tetraethylortosilicate-SiO2 nanoparticles composite (PDMS-TEOS-SiO2NPs). When the composite is immersed into the samples, casein is extracted from the solution and derivatized inside the PDMS matrix after 10min at 100°C. The sensing support changes its color from yellow to orange depending on the casein concentration. Quantitative analysis can be carried out by measuring the absorbance with a reflection probe or by image-processing tool (GIMP). This sensor provides good sensitivity and precision (RSD% <12%). The method validation has been done by applying the biocinchoninic acid method (BCA). Moreover, semiquatitative analysis of casein can be performed by visual observation. Taking into account the advantages of small size, rapidity, simplicity, good stability and high compatibility in aqueous solution, this sensor is expected to have potential practical applications for in-situ determination of casein. Finally the method has been applied to analyze effluents from dairy industries.
Copyright © 2015 Elsevier B.V. All rights reserved.
The cleaning of hard surfaces soiled with starch films using nonionic (alkylpolyglucosides and polyoxyethylene alkyl ethers) and zwitterionic (lauramine oxide) surfactant solutions has been investigated. Response Surface Methodology (RSM) was applied to determine the effect of the composition of the cleaning solution on detergency, as well as the relationship between the contact angle of surfactant solutions on starch films and the removal efficacy of such films. The surfactants with a higher capacity for the removal of starch films were lauramine oxide and alkylpolyglucosides, and their mixtures. The effect of polyoxyethylene alkyl ethers was also statistically significant; however their contribution to soil removal was very low. A correlation between contact angle and detergency for starchy soils was found, and the importance of the hydration process of the starch film on its removal was established.
Número de publicación: 2 251 269 Número de solicitud: 200202364 Método BSF (Baño - Sustrato - Flujo) y dispositivo para la evaluación de la eficacia detersiva y dispersante de tensioactivos, de coadyuvantes de la detergencia y de composiciones detergentes de superficies duras con objeto de evaluar la eficacia detersiva y dispersante de detergentes de las mismas, caracterizado porque el dispositivo consta de un recipiente que contiene el baño de lavado provisto de termómetro agitador y orificio para la extracción de muestras, una columna de relleno que contendrá el sustrato sucio, una bomba peristáltica un baño de agua termostatizado para asegurar una temperatura constante en todo el sistema y un agitador que homogeneiza el baño de lavado. Universidad de Granada
This chapter focuses on the physical chemistry of cleaning processes in aqueous systems in a systematic way and provides more information about the physical chemical basics. The cleaning process can be divided into four different key factors: chemistry, mechanical action, thermal effects, and time. Depending on the substrate that has to be cleaned and the soil, one of these factors can be dominant or all factors can have similar influence. The physical chemistry of cleaning processes is influenced by effects at the interfaces and in the bulk phases. Interfacial phenomena are the basis for all the cleaning and washing processes. The effects range from the wetting of hard surfaces or fabrics and the dissolution of stains from hard surfaces or fabrics to the removal of ions from the washing liquor or the interaction of softeners with the fabric in the rinse cycle of a washing process. In addition to these interfacial effects, the bulk properties of the liquid system play an important role. The cleaning liquid can be either a homogeneous one-phase system or a dispersion of two or more immiscible phases, for example, a foam or an emulsion of two immiscible liquids. Also, viscosity or structures within the liquid may have a great impact.
The cleaning of protein based deposits from food process plant is commonplace in the food industry, but is not well-understood. The factors which influence cleaning have been investigated experimentally using (i) a fouling apparatus which generates a uniform and reproducible protein deposit, and (ii) a cleaning apparatus in which thermo-hydraulic conditions are well defined. Cleaning has also been examined visually. Temperature, flow rate and concentration effects have been identified. If an excessive cleaning chemical concentration is used, the rate of removal is reduced. Cleaning occurs by the removal of lumps of material from the surface, rather than uniformly; any model should take this into account.
A method has been formulated and tested in a laboratory device to evaluate the detersive and dispersant performance, as well as the washing dynamics, of surfactants and builders and the formulation of the detergent. The method, called bath−substrate flow (BSF), is based on the separation of the washing bath from the substrate to be washed after contact of the two by a cyclic-flow process. The method serves to analyze mechanical washing systems, such as dishwashers, tunnel washes, floor-washing machines, and industrial-scale cleaning systems. The circumscribed central compound experimental design was applied, as was the response surface method, to correlate the detergency values found.
Surfactant cleaning of ultrafiltration membranes is essentially a sequence of three stages. The micelles, formed when the dose of nonionic surfactant exceeds the critical micelle concentration, transport to the membrane surface, partially disassemble, and bind to proteins. The binding first results in protein dislocation but then continues to surfactant occupation of the membrane surface including the sites released by the proteins. The membrane surface gradually becomes more hydrophilic and ripe for the adsorption of micelles that now build a cake layer. The developed cake is responsible for an increased protein retention and severe fouling.The surfactant cleaning time needs to be optimized to maximize the protein solubilization and to prevent the growth of a micelle cake. Circulation of a cleaning solution accelerates the surfactant transport to the membrane surface but facilitates micelle pore blocking. The induced internal fouling can counteract the benefits of reduced cleaning times due to circulation. Water flow can disassemble the external cake and wash away surfactant monomers, but will barely release clogged pores.
The need to generate consistent and reproducible fouling layers for the study of cleaning mechanisms has prompted the use of whey protein solutions as model systems. We have employed both forced flows over heated surfaces—which are thereby fouled—or natural convective flows subjected to thermally induced gelation in sealed vessels. Specifically, deposits were generated from the same whey protein powder (30% WPC) by (1) formation of ‘surface deposits’, from a solution flowing over a heated surface, (2) gelation, termed ‘G80’, where the bulk temperature in the sealed vessel remains <72°C, thus avoiding aggregation in the bulk, and (3) gelation, ‘G90’, with bulk temperature 72°>C. Evident differences in deposit structure and properties were recorded and related to differences in cleaning behaviour observed using fluid dynamic gauging (FDG) in three modes: (i) quasi-stagnant mode, (ii) quasi-stagnant mode with fluid sampling, and (iii) duct flow with thermal resistance measurements. The surface and G80 deposits showed similarities, while the G90 deposit differed markedly. Larger differences between the surface and G80 deposits were observed under cleaning-in-place conditions.
The use of cleaning agents containing enzymes to reduce the (non-biodegradable) chemical loading of cleaning effluents from milk pasteurizer heat exchangers was investigated on the laboratory and plant scale. In the laboratory trials, an acid treatment (15 min, 0.5% nitric acid, 60°C) was followed by a short rinse with fresh water and then enzymatic treatment (45 min). Temperature and pH ranges were adjusted to the optimum conditions specified by the enzyme manufacturer. Deposit-free metal surfaces were obtained with three enzymes (Savinase®, Properase 1600 L® and Esperase® ). The Savinase® agent was subsequently used in a field test featuring a milk pasteurizer (ZE 23 WP1, 25,000 l h–1, Alfa-Laval). Process conditions were matched to the laboratory conditions. After a short final rinse, the heater was opened and visual examination indicated that all surfaces in contact with the product were clean. After one week's fouling/cleaning cycles the surfaces, including the separator, were still clean. These studies indicate that enzyme-based cleaning of milk heaters can be effective. The considerable environmental benefits offered by enzyme cleaners can be realized if some of the remaining difficulties concerning enzyme dosage, process control and economics can be overcome.
Present production of wild fish resources is around 85 million tonnes per year, and the maximum long-term potential of marine capture fisheries of some areas and fisheries has been reached. However, not all that is obtained from the sea is adequately used and three clearly differentiated factors can be taken into account to explain this fact: discards, wastage on board and byproducts and wastage ashore. Although some efforts have been made to change this situation, a more efficient and intelligent use is needed of the natural resources extracted from sea and wasted.
In this article, the present utilization of discards and fishery wastage and also the future trends and the expected future of fishery industry are presented.
The aim of this work was to study the cleaning of inorganic membranes fouled by whey protein solutions using proteolytic enzymes. Tami® 150+4T membranes (Tami Industries, S.A., 26110 Nyons, France) of 400kg/mol molecular weight cut-off (MWCO) and a ZrO2 filtering layer were selected to carry out the tests and Maxatase® XL (Genencor International, 2333 CN Leiden, The Netherlands) and P3-Ultrasil® 62 (Henkel Ibérica, S.A., 08025 Barcelona, Spain) were investigated as cleaning agents. Cleaning efficiency was observed to be a function of the operating conditions. The operating conditions studied were the pH of the cleaning solution, the enzymatic agent concentration and cleaning time. Very high cleaning efficiencies (close to 100%) were achieved in short operating times (20min). The proteolytic enzymes were observed to adsorb onto the inorganic membrane used. However, enzyme-cleaned membranes gave better results than chemically-cleaned ones when used for whey protein fractionation: higher permeate flux was obtained, while selectivity remained practically the same. No peptides were detected in the retentate and permeate streams resulting from hydrolysis of proteins by the adsorbed enzyme. The possibility of reusing the enzyme solutions for consecutive cleaning steps was also studied. A 30% loss in activity was observed during each cleaning cycle, irrespective of the initial activity of the solution.
The effectiveness of the removal process of starch from different surfaces was studied using a laboratory device called Bath-Substrate-Flow. To do this, experiments were performed using the following solutions as washing bath: (a) the commercial nonionic surfactant Glucopon® 650; (b) the commercial anionic surfactant, linear alkylbenzene sulfonate LAS, and (c) the enzyme α-amylase (obtained from the microorganism Bacillus licheniformis). The washing efficiency was related to the temperature of the process, the washing bath composition and the substrate used. The highest detergency was detected with the glass spheres presented, followed by the polyurethane discs. The cleaning process with the polyurethane discs is strongly dependant on the viscosity of the starch film, because their porous structure determines milder shear conditions inside them. The effect of temperature on starch removal was related to the properties of the washing bath (interfacial tension, viscosity, etc.) as well as to the solubility and viscosity of the soiling agent. The use of surfactants or enzymes under the appropriate conditions of concentration and/or temperature proved to be an interesting option for clean-in-place processes of starchy soils in the food industry, guaranteeing cleaning with a reduced risk of contamination.
Facilitation of cleaning of stainless steel particles fouled with heat-treated bovine serum albumin (BSA) was studied using gaseous ozone generated from a pure oxygen-fed ozonizer at concentrations of 0.1 to 0.5% (v/v). Ozone pretreatment markedly accelerated the rate of BSA desorption during subsequent caustic alkali cleaning. The effect of ozone pretreatment depended on the concentration of ozone and it was attributed to partial decomposition of BSA molecules into some fragments. It was also found that the surface charge property of stainless steel particles was modified by ozone oxidation, resulting in the improvement of the cleanability of stainless steel surfaces.
The influence of detergent concentration, temperature and flow rate on the time to remove milk deposits from the heated surfaces of a plate heat exchanger was studied. The results indicate that the main reduction in cleaning time was produced by small increases in the passage mean velocity of flow in the range 0.2 to 0.5 m/s. Increasing the temperature to 75 °C also resulted in substantial reductions in cleaning time. Variations in concentration, for which there was an optimum, had the least effect on cleaning time of the parameters investigated.
Detersive processes are complex systems involving a great number of variables. To determine the effect of these variables
on the washing of hard surfaces and fatty soils is the object of this work. The statistical design of experiments has been
used to evaluate the influence of factors such as temperature, soil concentration and surfactant concentration on detergency.
The experimental trials have been made in a continuous-flow device where the soiling agent is confined in a column filled
with borosilicate glass spheres. Solutions of the commercial surfactant Berol© LFG61 (a mixture of alkylpolyglucosides and fatty-alcohol ethoxylates) have been employed as the wash bath. Both the design
of experiments and the continuous experimental system used proved to be an effective tool for detecting the key variables
in the cleaning process. Expressions were developed to simulate detergency levels as a function of the variables assayed,
always inside the experimental domain. In the trials with oleic acid as the soiling agent, it was found that the temperature
and soil concentration were the most important variables to take into account, while the surfactant concentration was not
a significant variable. When a semi-solid mixture of different fatty acids was employed, all the variables assayed proved
significant, with high detergency values being reached by combining temperature and surfactant concentrations. Results clearly
show that the effectiveness of the surfactant used is influenced by the type and concentration of the soil and thus the intended
application of the product being developed should be taken into account when designing detergent formulas.
The present work analyzes the effect of incorporating a lipolytic enzyme (Lipolase® 100L) into detergent formulas for washing fatty soils on hard surfaces. The experimental device, which is called a “bath-substrate-flow”
device, uses a continuous flow on a substrate (glass spheres) soiled with triolein. Washing tests were done using only the
enzyme and changing both its concentration and the temperature of the process. The results showed that, in the presence of
lipase, soil removal was achieved through three consecutive mechanisms: (i) fundamental devoval of the soil by the bath flow
through the experimental device; (ii) emulsion of the soil in the washing medium; and (iii) enzymatic hydrolysis of the dispersed
soil. Different commercial surfactants were used, and detergency was evaluated in the absence and presence of lipase. The
use of surfactant formulas with the lipolytic enzyme showed a positive effect of the enzyme on the detergency values registered
with the fatty alcohol ethoxylate surfactants Findet® 10/15 and Findet 1214N/23, and with the anionic surfactant linear alkylbenzene sulfonate. The commercial surfactants Glucopon® 600, Glucopon 650, Findet 10/18, and Findet Q/21.5NF alone each presented high detergency values for fatty soils, and the
effect of the incorporation of the lipase was not significant.
The potential suitability of 10 commercial protease and lipase products for cleaning-in-place (CIP) application in the dairy industry was investigated on a laboratory scale. Assessment was based primarily on the ability of the enzymes to remove an experimentally generated milk fouling deposit from stainless steel (SS) panels. Three protease products were identified as being most suitable for this application on the basis of their cleaning performance at 40 °C, which was comparable to that of the commonly used cleaning agent, 1% NaOH at 60 °C. This was judged by quantification of residual organic matter and protein on the SS surface after cleaning and analysis by laser scanning confocal microscopy (LSCM). Enzyme activity was removed/inactivated under conditions simulating those normally undertaken after cleaning (rinsing with water, acid circulation, sanitation). Preliminary process-scale studies strongly suggest that enzyme-based CIP achieves satisfactory cleaning at an industrial scale. Cost analysis indicates that replacing caustic-based cleaning procedures with biodegradable enzymes operating at lower temperatures would be economically viable. Additional potential benefits include decreased energy and water consumption, improved safety, reduced waste generation, greater compatibility with wastewater treatment processes and a reduction in the environmental impact of the cleaning process.
Surface Plasmon Resonance (SPR) and rubisco protein stain were used as tools to screen the effectiveness of detergent formulations in cleaning a protein stain from solid surfaces. Surfactant and biosurfactant-based formulations, with and without added protease, were screened for cleaning performance. Enzyme-free detergent formulations at 1500 ppm total surfactant were insufficient to cause complete surface cleaning, despite the high concentration of surfactant. The cleaning performance of a "home-made" formulation containing 2 ppm subtilisin A (SA) and 2 ppm sodium dodecyl benzyl sulphonate (SDOBS) was as efficient as the best amongst the three enzyme-free 1500 ppm formulations. The cleaning performance of 2 ppm SA in the absence of SDOBS was less effective than the combined formulation, even though 2 ppm SDOBS alone did not cause any protein removal. The observed synergistic performance was attributed to the cooperative mechanisms (chemical and physical attack) by which these two agents act on a rubisco stain. Replacing SDOBS in the enzyme-surfactant formulation with the same amount of surfactin biosurfactant (2 ppm) gave the best rubisco removal of all formulations examined in this study, irrespective of the surface chemistry underlying the protein film. It was found that 75% and 80% of immobilised rubisco stain could be removed from hydrophobic and hydrophilic surfaces, respectively, by the biosurfactant-SA formulation (compared with 60% and 65%, respectively, using the SDOBS-SA formulation). Our results suggest that it may be possible to generate fully renewable biochemical-based cleaning formulations that have superior cleaning performance to existing technologies. In developing optimised formulations, there is a pressing need for chip-based tools similar to that developed in this research.
Bicinchoninic acid, sodium salt, is a stable, water-soluble compound capable of forming an intense purple complex with cuprous ion (Cu1+) in an alkaline environment. This reagent forms the basis of an analytical method capable of monitoring cuprous ion produced in the reaction of protein with alkaline Cu2+ (biuret reaction). The color produced from this reaction is stable and increases in a proportional fashion over a broad range of increasing protein concentrations. When compared to the method of Lowry et al., the results reported here demonstrate a greater tolerance of the bicinchoninate reagent toward such commonly encountered interferences as nonionic detergents and simple buffer salts. The stability of the reagent and resulting chromophore also allows for a simplified, one-step analysis and an enhanced flexibility in protocol selection. This new method maintains the high sensitivity and low protein-to-protein variation associated with the Lowry technique.
Square (2.54 x 2.54 cm2) 304 stainless steel metal plates were cleaned, passivated, and soiled by autoclaving (121 degrees C at 15 psi for 15 min) with reconstituted nonfat dry milk (20% solids). Fifteen-minute treatments using either warm water (40 degrees C) or ozonated cold water (10 degrees C) were conducted to compare prerinse cleaning potential of soiled metal plates. The chemical oxygen demand determination was performed on extracted organic material from treated metal plates. Results indicated that the ozone treatment removed 84% of soil from metal plates versus 51% soil removal by the warm water treatment, but the effectiveness of the two treatments did not differ (P > 0.05). Cleaning effects were visualized using scanning electron microscopy at 200x and 2000x magnification. The amount of soil film present on stainless steel metal surfaces was visibly lower on ozonated treatments versus on warm water treatments.
Membrane separation processes have become part of the set of basic unit operations for dairy process design and product development. These processes are employed in a variety of separation and concentration duties, but in all cases, the membranes must be cleaned regularly to remove both organic and inorganic material deposited on the surface from the fluid stream being processed. Cleaning is a vital step in maintaining the permeability and selectivity of the membrane and is necessary to return the plant to its original capacity, to minimize risks of bacteriological contamination, and to produce acceptable products. Caustic-, acidic-, and enzyme-based cleaners may be used for membrane cleaning and are usually formulated with additives to best match the specific cleaning duty. Cleaning generates significant volumes of wastewater and reduces membrane life and plant productivity, so each regime must be optimized with respect to concentration, order and duration of cleaning steps, temperature, pressure, and flow rate. This article reviews the key mechanisms governing cleaning performance and suggests directions by which further optimization may be achieved.
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