Đồ án Vệ sinh trong chế biến sữa (Sanitation in dairy plant)

To control the electrical discharge and maintain a corona, a dielectric space or discharge gap is formed using a dielectric material such as ceramic or glass. A grounded electrode that is usually produced from stainless steel acts as a boundary to the discharge space. The most common shape for ozone generators is a cylinder, which is the most space- efficient, economic form .Care must be taken to ventilate the equipment properly as released ozone can be irritating to workers. Ozone is very unstable at a high as well as at a low pH. Ozone is most effective at a pH range of 6.0 to 8.5. As water temperature increases, the solubility of ozone decreases. It dissipates almost immediately at 40°C. Ozone is a broad-spectrum germicide which is effective against food pathogens, yeasts, and molds, and viruses and protozoa. It has been used to sanitize dairy equipment and to disinfect water, including pools, spas, and cooling towers and for algae control in water and wastewater treatment plants. It is not tolerant of organic soil. The probable mode of action of ozone is through the attack on the cell membrane, rupturing and killing the cell. Another application is to release gaseous ozone in cold storage rooms to control molds and eliminate ethylene, which can accelerate ripening in fruits and vegetables. Ozone is more stable in the gas phase and in an aqueous phase. The use of ozone presents safety issues. It is a powerful irritant to the respiratory tract and a cellular poison that interferes with the ability of lungs to fight infectious agents. Ozone, as chlorine dioxide, has been found to produce brominated organic compounds that are alleged potential carcinogens. Furthermore, there is a high capital cost associated with the use of ozone including the need for generators at point of use as well as the energy costs to operate them. Also, ozone is corrosive to soft metals and mild steel as well as rubber and some plastics. Sanitation in dairy plant Page 21 Table 1: Specific Areas or Conditions where Particular Sanitizers are Recommended 2.6. Enzymatic cleaning It is known that monocomponent enzymes can be used for biofilm removal. The heterogenicity of the biofilm matrix limits the potential of these enzymes for use in effective cleaning. The proteinase samples, e.g. chemotrypsin were shown to be effective Sanitation in dairy plant Page 22 in reducing and inactivating pure-culture biofilms, but when milk residues were present no effect of the proteinases could be observed. The different enzymatic cleaning procedures tested were also shown to be ineffective in inhibiting growth and metabolic activities of bacterial strains isolated from dairies. Based on the varying results obtained for removal and inactivation of microbes on surfaces by enzyme preparates, one possibility could therefore be to combine various types of enzymes to attain efficient cleaning. The use of enzymes is also limited due to the lack of techniques for quantitative evaluation of the enzymatic effects and the accessibility of the different enzymatic activities. The results showed that the resazurin-based fluorometric assay tested during that part of the project performed at the Faculty of Veterinary Medicine at the University of Helsinki can be used for estimating the enzymatic activities on process surfaces. This method can be recommended especially when a rapid, high-throughput capacity system is needed (Mikkola, 1999; Augustin, 2000). Table 2: Optimal Cleaning Guides for Dairy Processing Equipment 3. Equipment Cleaning is generally accomplished by manual labor with basic supplies and equipment or by the use of mechanized equipment that applies the cleaning medium (usually water),cleaning compound, and sanitizer. The cleaning crew should be provided with the tools and equipment needed to accomplish the cleanup with minimal effort and time. Storage space should be provided for chemicals, tools, and portable equipment. Sanitation in dairy plant Page 23 3.1. Mechanical Abrasives Although abrasives such as steel, wool, and copper chore balls, can effectively remove soil when manual labor is used, these cleaning aids should not be used on any surface that has direct contact with food. Small pieces of these scouring pads may become embedded in the construction material of the equipment and cause pit corrosion (especially on stainless steel) or may be picked up by the food, resulting in consumer complaints and even consumer damage suits. Wiping cloths should not be used as a substitute for abrasives or for general purposes because they spread molds and bacteria. If cloths are necessary, they should be boiled and sanitized before use. 3.2. Water Hoses Hoses should be long enough to reach all areas to be cleaned, but should be no longer than required. For rapid and effective cleanup, it is important to have hoses equipped with nozzles designed to produce a spray that will cover the areas being cleaned. Nozzles with rapid-type connectors should be provided for each hose. Fan-type nozzles give better coverage for large surfaces in a minimum amount of time. Debris lodged in deep cracks or crevices is dislodged most effectively through small, straight jets. Bent type nozzles are beneficial for cleaning, around and under equipment. For a combination of washing and brushing, a sprayhead brush is needed. Cleanup hoses, unless connected to steam lines, should have an automatic shut off valve on the operator’s end to conserve water, reduce splashing, and facilitate exchange of nozzles. Hoses should be removed from food production areas after cleanup, and it is necessary to clean, sanitize, and store them on hooks off of the floor. This precaution is especially important in the control of Listeria monocytogenes. 3.3. Brushes Brushes used for manual or mechanical cleaning should fit the contour of the surface being cleaned. Those equipped with spray heads between the bristles are satisfactory for cleaning screens and other surfaces in small operations where a combination of water spray and brushing is necessary. Bristles should be as harsh as possible without creating surface damage. Rotary hydraulic and power-driven brushes for cleaning pipes aid in cleaning lines that transport liquids and heat exchanger tubes. Brushes are manufactured from a variety of materials horse-hair, hog bristles, fiber, and nylon but are usually nylon. Bassine, a coarse-textured fiber, is suitable for heavy- duty scrubbing. Palmetto fiber brushes are less coarse and are effective for scrubbing with medium soil, such as metal equipment and walls. Tampico brushes are fine fibered and well adapted for cleaning light soil that requires only gentle brushing pressure. All Sanitation in dairy plant Page 24 nylon brushes have strong and flexible fibers that are uniform in diameter, durable, and do not absorb water. Most power-driven brushes are equipped with nylon bristles. Brushes made of absorbent materials should not be used. 3.4. Scrapers, Sponges, and Squeegees Sometimes scrapers are needed to remove tenacious deposits, especially in small operations. Sponges and squeegees are most effectively used for cleaning product storage tanks when the operation has insufficient volume to justify mechanized cleaning. 3.5. High-Pressure Water Pumps High-pressure water pumps may be portable or stationary, depending on the volume and needs of the individual plant. Portable units are usually smaller than centralized installations. The capacity of portable units is from 40 to 75 L/minute, with operating pressures of up to 41.5 kg/cm2. Portable units may include solution tanks for mixing of cleaning compounds and sanitizers. Stationary units have capacities ranging from 55 to 475 L/min. Piston-type pumps deliver up to 300 L/min, and multistage turbines have capacities of up to 475 L/min, with operating pressures of upto 61.5 kg/cm2.The capacity and pressure of these units vary from one manufacturer to another. In a centralized unit, the high-pressure water is piped throughout the plant, and outlets are placed for convenient access to areas to be cleaned. The pipes, fittings, and hoses must be capable of withstanding the water pressure, and all of the equipment should be made of corrosion-resistant materials. The choice of a stationary or portable unit depends on the desired volume of high-pressure water and the ease with which a portable unit can be moved close to areas being cleaned. Other uses of high-pressure water in the plant can also determine whether a stationary unit is warranted. High-pressure, high-volume water pumps have been used primarily when supplementary hot, high-pressure water is desired. Because this equipment uses a large volume of water and cleaning compounds, it is frequently considered inefficient. This concept has been applied to portable and centralized high-pressure, low-volume equipment that blends cleaning compounds for dispensing in areas to be cleaned. With a lower volume and water temperature, it is a more efficient approach that can effectively clean areas that are difficult to reach and penetrate. 3.6. Low-Pressure, High-Temperature Spray Units This equipment may be portable or stationary. The portable units generally consist of a lightweight hose, adjustable nozzles, steam-heated detergent tank, and pump. Operating pressures are generally less than 35 kg/cm2. Stationary units may operate at the main hot Sanitation in dairy plant Page 25 water supply pressure or may use a pump. These units are used because no free steam or environment fogging is present, splashing during the cleaning operation is minimal, soaking operations are impractical and hand brushing is difficult and time-consuming, and the detergent stream is easily directed onto the soiled surface. 3.7. High-Pressure Hot-Water Units This equipment utilizes steam at 3.5 to 8.5 kg/cm2 and unheated water at any pressure above 1 kg/cm2. These units convert the high-velocity energy of steam into pressure in the delivery line. The cleaning compound is simultaneously drawn from the tank and mixed in desired proportions with hot water. Pressure at the nozzle is a function of the steam pressure in the line; for example, at 40kg of steam pressure, the jet pressure is approximately 14 kg/cm2. This equipment is easy to operate and maintain but has the same inefficiency as the high-pressure, high-volume water pumps. 3.8. Steam Guns Various brands of steam guns are available that mix steam with water and/or cleaning compounds by aspiration. The most satisfactory units are those that use sufficient water and are properly adjusted to prevent a steam fog around the nozzle. Although this equipment has applications, it is a high-energy-consuming method of cleaning. It also reduces safety through fog formation and increases moisture condensation, sometimes resulting in mold growth on walls and ceilings, and increased potential for the growth of L.monocytogenes. High-pressure, low-volume equipment is generally as effective as steam guns if appropriate cleaning compounds are incorporated. 3.9. Portable High-Pressure, Low-Volume Cleaning Equipment A portable high-pressure, low-volume unit contains an air- or motor-driven high- pressure pump, a storage container for the cleaning compound, and a high-pressure delivery line and nozzle (Figure 6).The self-contained pump provides the required pressure to the delivery line, and the nozzle regulates pressure and volume. This portable unit simultaneously meters the predetermined amount of cleaning compound from the storage container and mixes it in the desired proportion of water as the pump delivers the desired pressure. The ideal high-pressure, low-volume unit delivers the cleaning solution at approximately 55ºC with 20 to 85 kg/cm2 pressure and 8 to 12 L/minute, depending on equipment specifications and nozzle design. However, low-pressure, medium-pressure (boosted pressure),and high-pressure equipment exists. Although high pressure is effective in removing heavy soils, it can create too much atomization. Therefore, the food industry has evolved primarily to medium (boosted) pressure. The high-pressure cleaning Sanitation in dairy plant Page 26 principle is based on automation of the cleaning compound through a high-pressure spray nozzle. The high-pressure spray provides the cleaning medium for application of the cleaning compound. The velocity, or force, of the cleaning solution against the surface is the major factor that contributes to cleaning effectiveness. High- pressure, low-volume equipment is necessary to reduce water and cleaning compound consumption. This equipment conserves water and cleaning compounds, and it is less hazardous than high-pressure, high-volume equipment because the low volume results in reduced force as distance from the nozzle increases. Portable high-pressure, low-volume equipment is relatively inexpensive and quickly connected to existing utilities. Some suppliers of cleaning compounds provide these units at little or no rent to customers who agree to purchase their products exclusively. These units do require more labor than does centralized equipment because transportation throughout the cleaning operation is necessary and because less automation can be provided without a centralized system. Portable equipment is not as durable and can require an excessive amount of maintenance. High-temperature sprays tend to bake the soil to the surface being cleaned, providing the optimum temperature for microbial growth. This hydraulic cleaning equipment is beneficial for small plants because the portable units can be moved through the facility. Portable equipment can be utilized for cleaning parts of equipment and building surfaces, and is especially effective for conveyors and processing equipment where soaking operations are impractical and hand brushing is difficult and time-consuming. It appears that this method of cleaning may receive more attention in the future because it may be more effective in the removal of L.monocyto- genes from areas that are difficult to clean with less labor-intensive equipment such as Figure 6 A portable high-pressure, low-volume cleaning unit that is used where a centralized system does not exist. Sanitation in dairy plant Page 27 foam-dispensing units. A trend exists toward centrally installed equipment because of the potential labor savings and reduced maintenance. 4. Sanitation methods 4.1. Regulation and process of cleaning and disinfecting The design of modern dairy equipment allows cleaning and disinfecting to take place without the equipment having to be taken apart, i.e, cleaning-in-place (CIP). This means that the processing equipment must be made of materials (eg, stainless steel) that are resistant to the corroding effects of the cleaning agents. The processing equipment must also be designed in such way that all surfaces in contact with the product can be cleaned. Careful cleaning in dairy plant is very important because milk components are excellent substrates for microorganisms. This does not alone apply to the parts in contact with the product, but also to the external parts and rooms etc… 4.1.1. The effectiveness of the cleaning is determined by the following four factors:  The chemical factor is determined by the cleaning agent and the concentration in which it is used. The cleaning agent is chosen according to the type of pollution to be removed, in this way: Table 3: The cleaning agent is chosen according to the type of pollution to be removed The functions of the cleaning agents are: - To loosen the pollution - To keep the impurities dissolved in the cleaning solutions to prevent them from precipitation on the cleaned surfaces Sanitation in dairy plant Page 28 - To prevent sedimentation of lactic salts. Guiding concentrations: Acid (HNO3) 0.8-1.2%, and lye (NaOH) 0.8-1.5%.  The mechanical factor is determined by the speed of the liquid over the surfaces. The faster the liquid moves, the more efficient the cleaning will be. It is important that the movement of the liquid is turbulent, i.e. that the liquid parts continuously change place mutually. Consequently, the pump speeds are considerably higher during CIP than during production. The cleaning turbines in the tanks make up an effective mechanical factory, but partial blockings of the turbines may appear. In consequence, the turbines should be inspected regularly.  The thermal factor (the temperature) is very important. Within chemistry it is said that the reaction speed is doubled if the temperature is increased by 10 0 C. However, a too high temperature also presents disadvantages, as residues of proteins and lactic salts are precipitated at too high temperatures, and the solubility of the salts in the water is reduced. Guiding temperatures: Lye solution 70 – 750C and acid solution 60 – 650C.  The time factor is important to the softening and solution part of the pollution. In the program survey, approximate periods for the single steps in the programs are indicated. The indicated periods should only be regarded as a broad guidance, as there may be considerable differences between the single routes, both as regards equipment to be cleaned and the fouling degree. 4.1.2. Disinfection The purpose of a disinfection is to kill the largest possible number of bacteria to avoid an infection of the products. Heat in the form of steam or especially hot water is the most used form of disinfection. The central CIP plant includes programs for sterilisation with hot water, and the return temperature is set to 85 – 900C. Cleaning of dairy equipment is carried out as follows: 4.1.2.1. Pre-rinse The processing equipment is rinsed with cold or warm water. The object is to remove any possible product residue before cleaning. The rinsing water containing the product residue should be led to suitable reception facilities in order to minimise pollution. 4.1.2.2. Cleaning with sodium hydroxide Sanitation in dairy plant Page 29 The process equipment is cleaned by means of circulation of a hot sodium hydroxide cleaning solution. Today, special cleaning agents are commonly used instead of sodium hydroxide. After cleaning, the cleaning solution is collected and re-used. Re-use should not take place before the concentration of the returning solution (%) has been checked and adjusted accordingly. 4.1.2.3. Intermediate rinse Any remaining cleaning solution is flushed out with either collected rinse water or fresh water. 4.1.2.4. Cleaning with nitric acid The process equipment is cleaned by means of circulation of a hot nitric acid cleaning solution. Today, special cleaning agents are commonly used instead of nitric acid. After cleaning, the cleaning solution is collected and reused. Re-use should not take place before the concentration of the returning solution (%) has been checked and adjusted accordingly. 4.1.2.5. Final rinse Any remaining cleaning solution is flushed out with either cold or hot water. Chemical free water is collected and used for pre-rinse. 4.1.2.6. Disinfection This is carried out immediately before the product plant is put into operation. Disinfection can be carried out thermally or chemically. The CIP plant is normally designed to allow for disinfection by circulation of either hot water at 90-95°C or a solution of e.g. hydrogen peroxide. Today special agents for disinfection is widely used in place of hydrogen peroxide. Disinfection must always be followed by a rinse with clean and drinkable water. 4.1.3. Cleaning Methods 4.1.3.1. Cleaning agents: The following cleaning agents can be used for CIP-cleaning.  Lye, NaOH, Sodium hydroxide: - 30% concentrated solution.  Acid, HNO3,Nitric acid: Sanitation in dairy plant Page 30 - 30% concentrated solution. - 62% concentrated solution. Hydrochloric acid, (HCl), and/or chlorine-containing cleaning agents, (Cl ), must never be used. 4.1.4. General maintenance of CIP plant:  Daily check: Control of lye and acid cleaning concentrations.  Weekly check: Control of stone deposits in lye tank/ tanks and water tank/tanks. Drawing off of bottom sludge from lye and acid tanks.  Monthly check: Control of various gaskets and replacement of these, if necessary.  Quarterly check: Change of cleaning solution in the lye and acid tanks. Table 4: Concentration Of Cleaning Solution Sanitation in dairy plant Page 31 4.2. Cleaning process in the dairy plant’s areas: Depend on each different area, we choose suitable chemical compounds and the hygiene methods. Table 4 lists the typical concentration of cleaning compounds and sanitizers for various cleaning applications. Although variations can exist, the suggested concentrations should be considered. Table 5: Typical concentrations for various cleaning Applications a. CIP Cleaning Programs for Pipes and Tanks Table 6: CIP Cleaning Programs for Pipes and Tanks Ways and Solution Cleaning time (minutes) Note Pipes Pre-rinse, cold water/ recyclable water 1-3 *) Time is dependent on the physical conditions in and around various pipes/pipelines to be cleaned. **) Time is dependent on the physical conditions in and around various pipes/pipelines to be cleaned as well as the software to control cleaning of Lye cleaning 1% solution at 70°C (The time stated is only started when return concentration and return temperature are identical with the above) 6- 10 Intermediate rinse, cold water/ recyclable water - Special software solution 1-3 Acid cleaning 0.8% solution at 60°C (The time stated is only started when return concentration and return temperature are identical with the above 4-6 Final rinse, cold water 1-3 Sanitation in dairy plant Page 32 (The time stated is only started when return concentration indicates clean water) pipes/pipelines. Above times are stated as efficient cleaning times and should be seen as recommendable values. These values may change dependent on the physical conditions in and around various pipes/ pipelines as well as the complexity of various products with regard to the physical/chemical conditions, as well as the complexity of various physical/ chemical as well as microbiological deposits. Picking up of residual product * minutes Hot water sterilisation at 85°C (The time stated is only started when return temperature is identical with the above). Cold water disinfection with hydrogen peroxide, H2O2, solution 200 ppm 3-5 Total cleaning time ** minutes Tank Picking up of residual products * minutes *) Time is dependent on the physical conditions in and around various tanks to be cleaned (tank dimension). **) Time is dependent on the physical conditions in and around various tanks to be cleaned (tank dimension), as well as the software to control cleaning of Pre-rinse, cold water/recyclable water 1-3 Lye cleaning 1% solution at 70°C (The time stated is only started when return concentration and return temperature are identical with the above) 10-15 Intermediate rinse, cold water/recyclable water - special software solution 1-3 Acid cleaning 0.8% solution at 50-60°C (The time stated is only started when return concentration and return temperature are identical with the 4-6 Sanitation in dairy plant Page 33 above) tank/tanks. Above times are stated as efficient cleaning times and should be seen as recommendable values. These values may change dependent on the physical conditions in and around various tanks (tank dimensions) as well as the complexity of various products with regard to the physical/chemical conditions, as well as the complexity of various physical/ chemical as well as microbiological deposits. Final rinse, cold water (The time stated is only started when return concentration indicates clean water) 0.5-1 Total cleaning time ** minutes Hot water sterilisation at 85°C (The time stated is only started when return temperature is identical with the above) Cold water disinfection with hydrogen peroxide, H2O2, solution 200 ppm 3-5 b. Cleaning procedures used for pasteurizers A CIP programme for a pasteurizer circuit normally consists of prerinsing, circulation of an alkaline detergent solution, intermediate water rinse, circulation of acid solution and postrinsing. Acid circulation is included to remove encrusted protein and salts from the surfaces of heat-treatment equipment (Chisti & Moo-Young, 1994). The flow rate must be more than 1.5 m/s to achieve the mechanical force necessary to prevent biofilm build-up (LeChevallier et al., 1990). Extensive bacterial biofilms may also develop on gaskets in dairy equipment when regular CIP procedures are performed (Austin & Bergeron, 1995; Storgårds et al., 1999). Sanitation in dairy plant Page 34 Table 7: CIP Cleaning Programs for pasteurizers Pasteurisers Cleaning Time (minutes) Note Pre-rinse, cold water/recyclable water 5-10 *) Time is dependent on the physical conditions in and around various pasteuriser/ pasteuriser plants to be cleaned. **) Time is dependent on the physical conditions in and around various pasteuriser/ pasteuriser plants to be cleaned as well as the software to control cleaning of pasteuriser/ pasteuriser plants. Above times are stated as efficient cleaning times and should be seen as recommendable values. These values may change dependent on the physical conditions in and around various pasteuriser/ pasteuriser plants as well as the complexity of various products with regard to the physical/chemical conditions, as well as the complexity of various physical/ chemical as well as microbiological deposits. Lye cleaning 1.5% solution at 70°C (The time stated is only started when return concentration and return temperature are identical with the above) 45-60 Intermediate rinse, cold water/recyclable water - special software solution 5-10 Acid cleaning 0.8% solution at 50-60°C (The time stated is only started when return) concentration and return temperature are identical with the above) 20-30 Final rinse, cold water (The time stated is only started when return concentration indicates clean water) 2-5 Total cleaning time ** minutes Hot water sterilisation at 85°C (The time stated is only started when return temperature is identical with the above) Cold water disinfection with hydrogen peroxide, H2O2, solution 200 ppm. 15-20 Picking up of residual products * minutes Long-standing processing will cause fouling on the surface of processing equipment, especially in heat exchanger plates which results in the growth of harmful thermophilic bacteria. It is important to specify the correct processing times and cleaning methods. The cleaning efficiency of different cleaning agents was tested using milk burned for 8 h on stainless-steel coupons (AISI 304, 2B) using the pilot equipment ( Figure 7) Sanitation in dairy plant Page 35 Figure 7: a. Pilot equipment in simulation of soiling surfaces with burned yoghurt-milk. b. Pilot equipment in soiling surfaces with heated yoghurt-milk. Sanitation in dairy plant Page 36 The difference between various cleaning programmes can be seen in Fig. 8: stainless-steel surfaces soiled with burned yoghurt milk containing harmful thermophilic bacteria before cleaning (Fig. 8a), after single-phase cleaning with 0.7% NaOH (Fig. 8b), after 2-phase cleaning with 0.7% NaOH and 1.0% HNO3 (Fig. 8c), after 2-phase cleaning with 0.7% NaOH containing the chelator solution and 1.0% HNO3 (Fig. 8d) and after single-phase cleaning with 0.7% NaOH containing the chelator solution (Fig. 8e). Figure 8: stainless-steel surfaces soiled with burned yoghurt milk containing harmful thermophilic bacteria before cleaning c. Cleaning of membranes filtration: Cleaning of membranes is nothing like cleaning of standard dairy equipment made of stainless steel. Membrane elements are often organic polymeric membranes made of materials, which only tolerate certain cleaning limits in terms of pH and temperature (and desinfectants/oxidisers). Therefore it is almost always necessary to use formulated cleaning products including enzymatic products from approved suppliers like Henkel, Sanitation in dairy plant Page 37 Ecolab, Diversey- Lever, Novadan and others. In the table below some limits are listed for different membrane materials. Table 8: Character of membrane filtration Water flux: After installation and cleaning of new membranes, the water flux should be registered to be used for future reference. Organic membranes always stabilise within the first few weeks. Cleaning of membranes should always be followed by a water flux reading, which must be recorded at the same pressure, temperature, time and cleaning step, so the cleaning efficiency can be monitored. d. CIP and hardness of water (Is determined from the content of calcium and magnesium): The hardness of the water is an important factor, as it governs the dosage concentration of the cleaning chemicals and the flushing time. Soft water is the most gentle for the membranes, with a low risk of mineral precipitation on the membrane surface. However, soft water has a much reduced buffering effect when dosing cleaning chemicals, which means that pH limits are reached at lower concentrations. As a rule of thumb, if 2% may be tolerated in 20°dH before the pH limit is reached, only 1% may be tolerated in 10°dH (when applying Divos 124). However, these figures are not true for all caustic products, but the principle is the same. Lower concentrations reduce the cleaning efficiency even at the same pH, as there are less cleaning agents (surfactants, carriers, complexing agents) to bind or “carry” the soil and to keep it in solution until flushing. Severe foaming may Sanitation in dairy plant Page 38 also be a result of using soft water. The flushing time is prolonged with higher water consumption as a result (ever washed hands using soft water?). Some enzymatic products need certain minerals (e.g. calcium) in order to work. When using soft water, these minerals will have to be added. When using hard water extra complexing agents such as EDTA or NTA must be added in order to prevent mineral precipitation. The solubility of calcium salts is much reduced at higher temperatures resulting in heavy fouling of the membrane Pre-treatment methods If some of the parameters do not meet the requirements, the following pre-treatments may be applied: Cartridge filter: Reduces and remove particles by raw water filtration (5-10 micron pore size). Sand filter: Removes Fe and Mn. Sand filter: Special filling material removes fouling particles Active carbon: Removes organic matter and neutralizes chlorine. Bisulfite: Neutralises chlorine. Ion exchange: Removes SiO2, Al, Fe, Mn, softens hard water. Chlorination: Kills bacteria (e.g. from surface water). One hour chlorination followed by dechlorination is recommended. e. General requirements about areas in the dairy plant (“National Dairy Regulations and Code (NDRC)” and “Interpretive Guidelines for the Processing Sector”): Floors Floor construction is a crucial component of a properly designed dairy plant and should be designed to eliminate future problems. The floors of all rooms in which dairy products are processed, pasteurized, manufactured or stored must be constructed of sealed concrete or other impervious material with a smooth surface and sloped 1/4 inch per foot to adequately trapped drains. The floor /wall joints are to be coved for ease of cleaning and maintenance. Walls and Ceilings Walls and ceiling of rooms in which dairy products are processed, pasteurized, manufactured, packaged or stored shall be smooth, light coloured and impervious to moisture. Sanitation in dairy plant Page 39 Drains Properly trapped and covered floor drains with removable covers are essential in all areas of the plant. The drains must be of an adequate size and be kept clean. Overhead Utility Lines All overhead utility lines should be installed in such a manner as to avoid contamination of products below. They should be insulated where necessary and be designed and finished to prevent the accumulation of dirt and minimize condensation, mould development and flaking. They must be easy to clean Lighting All plants shall provide adequate lighting, which is shielded with shatterproof coverings to ensure clean and efficient plant operation. Ventilation Adequate ventilation is required in all plants to prevent excessive heat, dust accumulation, odours or condensation and to provide a proper work environment for employees. The direction of airflow should be from the processing area outward to other areas of the plant. Dry Storage Area A separate dry storage area shall be provided in all dairy plants. Since the size requirements will depend on the needs of individual plants, this item will require site specific consideration. The intent and purpose of the room will be to provide protected storage for supplies and equipment not in immediate use. Water Supply Complete details on the water supply. The source and proposed treatment (when necessary) must be described. Professionally engineered water systems may be required depending on source and type of dairy products being processed. An adequate supply of hot and cold water under pressure shall be provided in all plants. The operator must assure that the water is bacteriologically and chemically safe. NOTE: Adequacy of the water supply will be determined on a site-specific basis and related to maximum production volumes. The responsibility for water quality analysis rests with the applicant. Consult the local health unit for types of tests required. Results of bacteriological and chemical analyses must be submitted for local health unit assessment prior to issuance of final approval to operate. Sanitation in dairy plant Page 40 Sewage Disposal Systems Sewage disposal facilities (either municipal or private systems) must be provided at all dairy plants. These systems are subject to provincial and municipal requirements. Consult the local health unit for required approvals. Refrigeration Refrigerated storage facilities must be provided for all dairy products. Temperature requirements for coolers and raw milk storage tanks shall be 4°C (40°F) or less but above 0°C (32°F); for freezers less than -18°C (0°F). Equipment Equipment used in the receiving, processing, pasteurizing, manufacturing, packaging, storing, dispensing, transporting or marketing of a dairy product shall be of an approved type or where applicable be based on 3A Standards. The equipment must not be defective, unsuitable or unsanitary. Staff Facilities Employee's facilities shall include a suitably designed dressing room and lunchroom. Conveniently located sanitary toilets for male and female employees shall be provided exclusively for the use of dairy plant personnel and shall not open directly into an area used for the processing or packaging of dairy products. Hand Washing Facilities Adequate and conveniently located facilities for hand washing and drying must be provided wherever the process demands. Where appropriate, facilities for hand disinfection should also be provided. 5. Biofilms, formation, developemt, and control 5.1. Introduction To a great extent, the science of public health has evolved from efforts to control various milkborne pathogens. Pasteurization and other procedures for disinfection of finished products have been very effective in controlling abroad spectrum of bacterial and rickettsial pathogens in milk and milk products. Despite the generally high quality of milk products in North America, recent reports show that bacterial contamination continues to present a significant threat to product quality and systems operations. Several factors have accounted for the current height-ened concern over food product safety ,including the recent and highly publicized contamination of hamburger meats in the Pacific North west by Escherichia coli, emergence(or reemergence)of Listeria spp. in milk and soft cheese processing operations and bacterial outbreaks in raw milk supplies. Sanitation in dairy plant Page 41 Although some of these outbreaks can beat tribute to poor quality assurance and sanitization procedures, other contamination problems occur despite the application of normal preventive maintenance and treatment regimens. An important reservoir of microbial contamination that has received relatively little attention is the microbial biofilm. In dairy processing operations, as well as in numerous other industrial systems, most bacteria are associated with surfaces. In addition to creating problems associated with public health and product spoilage, biofilms are responsible for mechanical blockages and the impedance of heat transfer processes. During plant operations, microbial biofilms are often difficult to detect and treat.By virtue of a number of unique survival strategies, bacteria and other organisms within biofilms are able to resist disinfectants and biocides, which are otherwise effective against their free-floating counterparts. This apparent resistance has been implicated in the survival of Listeria spp.in dairy product processing operations. The development of bacterial biofilms is a major cause of process fluid contamination leading to product deterioration. The inherent resistance of bacteria in biofilms leads to cycles of regrowth following system disinfection procedures. Are centre view of biofilms in the dairy processing industry has been prepared by Flintetal. Those scientists describe problems that are unique to pasteurization processes, in particular, Streptococcus thermophilus survival in biofilms on plate heat exchangers. 5.2. Bacterial biofilm development In natural aquatic systems, the majority of bacteria are attached to surfaces. Indeed, surface area is a major limiting factor for microbial growth in nearly every fresh water and marine environment. The ratio of planktonic (free-floating) bacteria to biofilm bacteria is a function of several interrelated factors, including surface energetic. materials of construction, to pography, hydraulic factors, and biofilm chemistry. Bacterial attachment and the formation of a biofilm appear to take place in a three- stage process. During the first stage, surfaces are rapidly coated with an organic conditioning film. This film might consist in blood of proteinaceous compounds such as albumin, in fresh water environments of humic substances, and in dairy operations of proteinaceous components of milk and milk products. This first stage occurs within the first 5 to 10 s after an otherwise clean surface is placed into a fluid environment. During the secondstage of adhesion, single bacterial cells are transported to surfaces, and reversible bonds are formed between the cell wall and the substratum. Bacterial extracellular polymeric substances (EPS) appear to mediate the attachment of primary Sanitation in dairy plant Page 42 colonizers to organic conditioning films that are associated with animate and inanimate substrata. The mature, third-stage biofilm consists of the organic conditioning film, a succession of colonizing bacterial consortia with their associated EPS and various detrital particles and ionic species. It is this structure that gives rise to the planktonic bacteria and their by- products (e.g., endotoxins). The question of whether differing substratum surface properties are communicated to the initial or succeeding organisms through the conditioning film is of great interest. Some workers have suggested that substratum properties can be transferred by an adsorbed protein film to adhering eucaryotic or prokaryotic cells. This supposition is based on their finding that the amount and surface structure of albumin adsorbed onto inanimate surfaces was a function of substratum wettability (surface free energy). Conversely, Flint et al. found that washed cells of S. thermophilus and Bacillus cereus attach to clean stainless steel surfaces within 60 s in the apparent absence of a conditioning film. Gasket materials, in cluding Buna-n and Teflon, have been found to accrete significant bacterial biofilms in a milk processing operation. Similar biofilms were found on surfaces exposed to both raw and pasteurized milk. Despite the recognition of the importance of conditioning films as precursors to biological fouling activities, treatments have not been developed for theircontrol or modification. 5.3. Detection To a great extent, the availability of effective detection techniques has limited the progress in understanding and resolving the problems related to biofilms. For 100 yr, microbiologists, for the most part, have virtually ignored the relationship of surface associated bacteria and other microorganisms to the overall population. Although planktonic samples can be obtained relatively easily from a water system or milk distribution line spigot, samples from pipeline and storage tank surfaces are more difficult to sample reproducibly. The acquisition of representative samples from surfaces in distribution and storage systems is particularly important for evaluations of disinfectant and biocide efficacy. The Robbins Device (Tyler Instruments, Calgary,AB, Canada) consists of a series of sample coupons that are flush-mounted in a rectangular flow channel. This biofilm sampler was designed to be sides-treamed to an existing distribution system to enable process control testing. Biofilms may be quantitatively removed from the Robbins Device by a combination of scraping and sonication and then enumerated. Laminar flow adhesion cells for sampling bacterial biofilms have been described. Reproducible Sanitation in dairy plant Page 43 colonization of aerobic and anaerobic bacterial isolates has been obtained with these devices, which also provide for real-time image analysis of colonizing organisms. Geesey and White and Pedersen have reviewed techniques for the sampling and isolation of bacteria associated with various surfaces. Fourier-transform infrared spectroscopy in the attenuated reflectance mode has been applied to the real-time analysis of developing biofilms. In addition to changes in biomass, metabolic status can be monitored (e.g.,the production of poly-β-hydroxyalkanoates). The application of quartz crystal microbalance gravimetric measurements to on-line monitoring of biomass has been described. This technique enables real-time analysis of cell numbers with a detection limit in the range of 10 5 cells·cm -2 . Measurements of open circuit potential detected the onset of biofilm formation on 316 stainless steel surfaces. Wong and Cerf have reviewed monitoring techniques that are specific for biofilms in dairy operations. Some of these techniques, including ATP- based bioluminescence, are subject to interferences from nonmicrobial biomass. There is a clear need for on-line tools to monitor bacterial biofilm development and cleaning efficacy in food processing industries. 5.4. Treatment options For the most part, the efficacy of disinfectant and biocide treatment has been evaluated on the basis of a bottle test. In this assay, bacteria are grown in laboratory culture (very often through multiple passages) and then challenged with an antimicrobial solution. System treatment concentrations, contact times, and environmental conditions (e.g., temperature) are based upon these types of laboratory studies. A number of workers have shown that the success of an antimicrobial agent is dependent upon its ability to inactivate and remove biofilm organisms. Indeed, low concentrations of sodium hypochlorite in the range of 0.5 to 5ppm are only inhibitory to biofilms associated with stainless steel surfaces; concentrations exceeding 50 ppm were required for inactivation under process control conditions. Particular attention should be paid to gasket surfaces that contact the product because biofilm bacteria can remain viable on those areas despite otherwise effective clean-in-place treatments. As was mentioned previously, EPS appear to afford bacteria protection from antagonistic agents. For example, endemic strains of Staphylococcus aureus that were isolated from poultry equipment were eight times as resistant to chlorine as were S. aureus strains that were isolated from normal skin. The major phenotypic difference between these strains was the extensive EPS associated with the poultry equipment isolates and their ability to form macro clumps. Others have shown that Pseudomonas Sanitation in dairy plant Page 44 aeruginosa survived within biofilms associated with polyvinyl chloride piping after 7 d of exposure to iodophors and phenolic antimicrobial solutions. These researchers suggested that these organisms survived within EPS masses on the interior walls of the piping. The structure of EPS acts as a diffusional barrier to antimicrobial penetration. Suci et al. found that the in vitro penetration rate of ciprofloxacin, an antibiotic, was significantly impeded by P.aeruginosa biofilms. The structure and composition of EPS apparently influence both diffusional resistance and oxidizing chemical demand. Sodium hypochlorite concentrations of 100 mg·L -1 heated to 65 0 C for 5 min or to 72 0 C for 1 min were required to inactivate L. monocytogenes biofilms associated with stainless steel surfaces. Treatment with 100 mg·L -1 of sodium hypochlorite for 30 s, followed by heat treatment at 65 C for 30 s, was not effective. With chlorine compounds, pH is an important treatment variable. The pka of hypochlorous acid, which has far stronger bactericidal activity than the hypochlorite ion, is approximately 7.5. Therefore, treatment pH should be maintained in the acidic range to provide maximal efficacy. Characklis suggests that chlorination programs might be improved by increasing chlorine concentration at the water-biofilm interface, increasing fluid shear stress at the water-biofilm interface, and controlling pH. High pH favors the hypochlorite ion promotion of detachment of mature biofilms, and low pH enhances hypochlorous acid disinfection of thin films. Other biocides used for biofilm control in the dairy industry include iodine, ozone, and chloramines. The isothiazolone microbicide, 2-methyl-5- chloro-2-methyl isothiazolone, has been employed at 10 mg·L -1 for the successful control of L. monocytogenes that is associated with conveyer systems in a dairy processing and packaging operation. As with some oxidizing biocides applied for suboptimal contact times, biofilm-mediated resistance to quaternary ammonium and iodophor compounds has been reported. Ozone has shown promise for disinfecting surfaces that come in contact with milk. Ozone is prepared onsite by passing dry oxygen or air through high voltage corona arc discharge electrodes. Like chlorine, ozone is a powerful oxidizing agent; bacterial membrane lipids, carbohydrates, and proteins are oxidized, resulting in cell death. Greene et al. compared ozonation with chlorination in disinfecting stainless steel plates colonized with P. aeruginosa or Al-caligenes faecalis. They found that the killing efficiencies of these two oxidizing agents were comparable. A relatively new disinfection technology that might have applications for the dairy and food products industries has been described. The technology involves passage of low level electrical fields (5 V cm -1 ;15 mA·cm -2 ) through biofilms in the presence of antimicrobials. Enhancement of biofilm bacterial inactivation occurred with both antibiotics and industrial biocides. Although Sanitation in dairy plant Page 45 viable numbers of bacteria did not decrease as a function of current application alone, killing activities of the biocides were enhanced by several orders of magnitude in the presence of these low level electric fields. Although mechanisms for this effect have not yet been established, they may involve alterations in EPS charge or cell membrane transport processes that facilitate transport of the antimicrobials to labile cellular components. Sanitation in dairy plant Page 46 REFERENCES [1] Norman G. Marriott, Principles of Food Sanitation fifth edition. 2006 [2] Marcw.Mittelman, Symposium: Biofilms: Development And Control [3] Biofilms, Internet Journal of Food Safety V.1, 6-7 [4] Homleid, Jens Petter & Mattila-Sandholm, Tiina. Evaluation of sanitation procedures for use in dairies. Espoo 2002. [5] Gerrit Smit, Dairy processing: Improving quality, 2003