Periodic cleaning and sanitation1, which includes disinfection of meat plant premises and equipment, is an integral part of Good Hygienic Practice (GHP, see page 341). Cleaning and sanitation can even be considered as one of the most important activities in the meat plant, as these measures provide the necessary environment for proper meat handling and processing.
Efficient meat plant cleaning and sanitation is often neglected as it requires extra work and the positive effects are not immediately visible. However, failures in meat plant hygiene can cause high financial losses in the long run. Unhygienic conditions in a meat plant result in
Proper cleaning and sanitation is becoming increasingly important in modern meat processing as more perishable and hygienically sensitive meat products come on the market, particularly convenience foods such as prepacked portioned chilled meat, vacuum-packed sliced sausage and ham products, meat products in controlled atmosphere packages etc. The microbial load of such products must be low to guarantee adequate shelf life and to avoid spoilage during distribution.
How to carry out meat plant cleaning and sanitation
Preconditions for efficient cleaning and sanitation are:
1) The term “sanitation” usually refers to disinfection and pest control.
Cleaning is the removal of dirt and organic substances, such as fat and protein particles from surfaces of walls, floors, tools and equipment. Through the cleaning procedures, high numbers of microorganisms (90% and more) present on the mentioned objects will be removed. However, many microorganisms stick very firmly to surfaces, in particular in tiny almost invisible layers of organic materials, so called biofilms, and will not entirely be removed even by profound cleaning but persist and continue multiplying.
Inactivation of those microorganisms requires antimicrobial treatments, carried out in food industries through hot water or steam or through the application of disinfectants. Disinfectants are chemical substances, which kill microorganisms but should not affect human health through hazardous residues and not cause corrosion of equipment. The application of disinfectants is called disinfection. The term sanitation refers to the inactivation of microorganisms through disinfectants, but also includes combating pests such as insects and rodents through chemical substances (insecticides and rodenticides).
When starting cleaning and disinfection/sanitation measures all food products must be removed from the area because:
Cleaning and disinfection procedures in the meat industries are complex processes depending on the surfaces to be treated and the kind of contamination to be removed. Selection of suitable chemicals for cleaning or for disinfection may require special knowledge. All these factors can make correct cleaning and disinfection a difficult task for the personnel involved. However, staff must be made aware that efficient cleaning and disinfection is of utmost importance for product quality and safety.
b) Cleaning techniques
The first step in floor and equipment cleaning is to physically remove scrap, i.e. coarse solid particles, with a dry brush or broom and shovel. This is usually referred to as “dry cleaning”. Using large amounts of water to remove this material would be extremely wasteful and eventually cause drains to clog and waste water treatment facilities to become overloaded.
More profound clean-up procedures require water in sufficient quantities. Manual cleaning using brushes or scrapers is widely applied in small-scale operations although labour and time-intensive (Fig. 488). A cleaning method commonly used in the meat industries is high pressure cleaning. The pressurized water is applied by high pressure units and special spraying lances. The pressure should be between 30-70 bar and the spraying nozzle £15cm from the surface to be cleaned. Otherwise the pressure being applied decreases rapidly. If hot water is used, the temperature should be 55°C at the nozzle in order to achieve sufficiently high temperatures at the surfaces, in particular for fat removal (Fig. 489).
|Fig. 488: Manual cleaning of working tables with brushes||Fig. 489: Cleaning of wall with pressurized water - care must be taken not to contaminate equipment|
High pressure water is efficient for surface cleaning after dry-cleaning of scrap. It serves for the removal of remaining small solid parts, blood and dirt from the entire floors and walls of processing sections as well as for the removal of meat and fat particles and layers of protein from tools and equipment. As hot water has a much better cleaning effect than cold water, hot water should be available for this purpose.
Cleaning with equipment producing a pressurized steam/water-mix is even more efficient as impact temperatures of approx. 100°C can be achieved. The disadvantage of this method is the intense fog and aerosol formation, which may not only cause unwanted microbial spreading by water droplets (aerosol) but also affect installations and equipment through high humidity and excessive condensation. For these reasons a steam/water-mix is not suitable for meat processing facilities and cold or hot pressurized water cleaning is preferred.
The removal of loose dirt and meat/fat residues by water does not mean that the cleaning was complete. Sticky or encrusted layers of fat or protein will still exist and must be removed. For this purpose chemical cleaning solutions can be very effective.
Application can be by hand using brushes or scrapers for dismantled equipment or in general for smaller surfaces to be cleaned. Mechanical cleaning with high pressure equipment together with cleaning solutions is used for larger floor and wall areas as well as working tables, containers and equipment.
Traditional cleaning substances for manual use are alkalines, such as sodium carbonates (Na2CO3, washing soda). These substances are efficient in dissolving proteins and fats, but may cause corrosion in tools and equipment, if their pH is 11 and above.
Commercially available cleaning agents in modern cleaning practices are complex compositions of either alkaline, acid or neutral chemical substances. In order to improve their dirt loosening properties, surface-active agents, also called surfactants or detergents are added. Detergents decrease the superficial tension of water. Water can then penetrate into the small spaces between dirt particles and surfaces (Fig. 490), where those particles are attached, thus facilitating their removal. For fat removal by pressurized hot water, cleaning detergents are important as they keep the fat dissolved and prevent fats settling down after the water temperature has decreased. Detergents may have additional cleaning components such as chlorine, silicate or phosphate. It is important that manufacturers indicate the type of the substance, either alkaline, acidic or neutral on the product label.
Fig. 490: Effect of detergents (surfactants): Decrease of surface tension of water droplets and impact angle (below), dirt particles are easier loosened and removed from surface.
Alkaline cleaning agents:
Generally suitable for removing organic dirt, protein residues and fat.
Acid cleaning agents:
Used particularly for removal of encrusted residues of dirt or protein or of inorganic deposits (“scaling”) such as waterstone, milkstone, lime etc.
Neutral cleaning agents:
Have much less effect than alkaline or acid cleaning agents, but have mild impact on skin and materials and are useful for manual cleaning of smooth surfaces without encrusted dirt.
In practice alkaline and acid cleaning substances should be used alternatively. The alkaline agent should be the substance used for routine cleaning, but every few days an acid substance should be employed instead in order to remove encrusted residues, scaling etc.
Cleaning substances together with the suspended dirt particles and fat must be rinsed off using potable water.
A relatively new cleaning method for the food industry, in particular the larger-scale plants, is foam cleaning (Fig. 491). Water foam containing detergents and other cleaning agents is sprayed on wetted walls, floors and surfaces of equipment. The foam does not immediately run off but clings to the surfaces. This allows a longer term contact on the surfaces to be cleaned. After a sufficient impact period (min. 15 minutes) the foam is washed down with water (water hose or low-pressure water spray). As no high pressure water spraying is needed for washing off the foam, the spreading of water droplets (aerosol) in the room to be cleaned is minimized.
Fig. 491: Foam cleaning
c) Disinfection techniques
Cleaning reduces a substantial amount of microorganisms (Fig. 492b) but it does not have the potential to completely eliminate all surface contamination. Persistent microorganisms will continue to grow in number by using remaining protein as nutrients and pose a further risk to the foods to be processed.
The elimination of microorganisms is achieved through disinfection1), either by using hot water (or better steam) or chemical disinfectants (Fig. 492c). Chemical disinfectants are preferred for most applications in the meat industries as they are easy to use and do not involve the risk of accidents or other negative side effects such as damage to equipment by generating high humidity or water condensation, which may occur when using steam.
|Uncleaned (rinsed only) (a) Many bacterial colonies (white spots)||After chemical cleaning (b) Reduced numbers of bacterial colonies|
After cleaning and disinfection (c) Very few bacterial colonies remaining
Fig. 492: Effect of cleaning and disinfection on the number of bacteria
Image of impression plate samples (see page 332) taken from a meat container (plastic)
1) Disinfection in the food sector does not aim at the complete absence of microorganisms (such as sterilization of surgical instruments in hospitals), but the number of microorganisms must be substantially reduced by the process.
Best disinfection results are achieved when chemical disinfection is preceded by intensive dry/wet cleaning (see page 370, b). Disinfection without precleaning is not fully efficient as many microorganisms remain embedded in encrusted dirt, protein and fat, which cannot be properly dissolved by disinfection chemicals. Therefore microorganisms remain protected against the disinfection chemicals. Moreover, remaining protein may inactivate chemical disinfectants.
Adequate rinsing with water after cleaning and prior to disinfection is also indispensable, as chemical disinfectants may be neutralized by remaining cleaning substances. All this has to be taken into account, otherwise the disinfection procedures may be inefficient and a waste of money.
A compromise on this issue is proposed by the chemical industry by offering so called combined disinfection/cleaning agents. They are made on the basis of quaternary ammonium compounds, which have surfactant and disinfectant properties. The combined method should be considered only in cases of very little dirt contamination.
It is very important that disinfection chemicals are strictly used according to the specifications given by the suppliers. Lower concentrations and shorter impact periods than prescribed will considerably reduce the efficacy of disinfection or make it totally inefficient. Surfaces should be dried after cleaning and rinsing before starting disinfection. This is important, as the concentration of the disinfection solution would be lowered with remaining water on the surfaces and possibly ineffective when becoming too highly diluted.
The application of chemical disinfectants is done with stationary or mobile spraying devices. In medium or small scale meat plants, mobile spraying devices are sufficient (Fig. 493). The disinfectant is applied by means of spraying lances and manual or electrical pumps. One important rule is, that the disinfectant solution must be applied from top to bottom, i.e., first upper parts of walls, then lower parts of walls and the floor last. The same applies to equipment.
Fig. 493: Disinfection of walls by using portable spray equipment. For operatorís protection gloves and facemask are recommended.
Hot disinfectant solutions (up to 50°C) are more effective than cold ones. After application, the disinfectant solution must remain for a certain period of time on the surfaces to be disinfected as indicated in the user instructions, normally for 30 minutes. Thereafter removal of the chemicals through rinsing with potable water is needed.
d) Disinfectants for the meat industry
Disinfectants should be effective and rapidly acting in killing microorganisms (Fig. 494). It should be noted that disinfectants do not sterilize the surfaces treated, absolute germ-free surfaces cannot be achieved, but disinfectants should kill all pathogens. The chemical composition of disinfectants vary depending on the specific target (slaughterhouse, meat processing, easily accessible open processing lines or closed food pipeline systems) and on chemical formulations by the individual disinfectant manufacturer. Modern disinfectants are mostly mixtures of different chemical substances. Combinations of disinfection chemicals achieve a synergistic effect and result in the elimination of a broader spectrum of microorganisms. The exact compositions are sometimes not fully revealed by the manufacturers. In principle the following groups of substances are used:
Chlorine containing compounds
Effective against a wide range of bacteria, penetrates cell walls, but has a corroding effect on equipment
Na - or Ca-hypochlorite (Na/Ca O Cl)
Gaseous chlorine (Cl2) (Hypochlorous acid is the effective substance used preferably for disinfection of water)
Aldehydes (used in animal production, e.g.
Destruction of microorganisms, may be corrosive
Quaternary ammonium compounds (QUATS)
Effect on cell walls, not corrosive, odourless, additional cleaning properties (surfactant)
Oxygen releasing substances
Penetrate into cells, good effect on all microorganisms incl. spores and virus, odourless, may be corrosive in concentrations >1%
Fig. 494: Effect of some chemical disinfectants on microorganisms
The following commercially available disinfectant is an example for an efficient combination of components:
The organic acids, apart from their sanitizing effect, decrease the pH as some disinfectants are more efficient at lower pH. The surfactants assist in penetrating organic material. The peroxide compounds have the direct antimicrobial effect by coagulation and denaturation of proteins (virus) and penetration through cell walls causing cell destruction (bacteria).
The available types of chemical disinfectants act differently on certain groups of bacteria and under certain pH-ranges. In order to achieve a maximum disinfection effect, it is recommended to alternate periodically the type of the chemical disinfectant applied. Utilization of suitable alternative substances will inactivate bacteria, which were possibly surviving the previous sanitation process. This procedure will also help to counteract the development of resistant bacteria in the meat plant (see “Cleaning and sanitation plan”, table 22).
e) Cleaning and disinfection (sanitation) schemes
Meat industry staff must be made fully aware of the need for proper cleaning. Cleaning should be treated as an integral part of the production process. It should be done carefully and not just superficially or in a rush at the end of the production process.
While daily cleaning or even cleaning several times a day is an absolute necessity, it has to be decided according to type and product lines or activity of each individual meat plant, where and at which time intervals disinfection measures should be applied.
Frequency of disinfection depends on need requirements:
Cleaning and disinfection plans
For all rooms and all equipment used for meat processing or meat storage, specific cleaning and disinfection plans should be established.
In table 22, an example is given for disinfection of meat processing equipment, in this case for a meat grinder. This type of equipment is an integral part of almost every meat processing line. Meat grinders require particular careful and frequent cleaning and sanitation, as the output product minced meat is hygienically very sensitive.
Table 22: Cleaning and disinfection plan (example)
Equipment: Meat grinder
|Pre-cleaning|| Potable water |
Pressure: 20-30 bars
Time: 20-30 min
pH: approx. 12
|1 x monthly |
Time: 20-30 min
pH: approx. 1.8
Pressure: 5-10 bars
|Disinfection||2 x weekly
Time: 30 min
pH: approx. 5.7
|3 x weekly |
Time: 30 min
pH: approx. 10.2
Pressure: 5-10 bars
Agent A: Alkaline cleaning substance
Agent B: Acid cleaning substance
Agent C: Disinfectant
Agent D: Disinfectant chemically different from C and supplementing impact of C