(1995)and Kumar and Anand, (1998). In general, however, biofilm formation is usually found only on environmental surfaces, and progression of attached cells through microcolonies to extensive biofilm is limited by regular cleaning and disinfection ibson et al.(1995)in studies of attached microorganisms in 17 different processing environments, recorded 79% of isolates as Gram negative rods, 8.6% Gram positive cocci, 6.5% Gram positive rods and 1.2% yeast strains. The most ommon organisms were Pseudomonas, Staphylococcus and Enterobacter spp Pseudomonads are environmental psychrotrophic organisms that readily attach to surfaces and are common spoilage organisms in chilled foods. Other commor Gram negatives that have been associated with surfaces are coliform organisms that are widely distributed in the environment and may also be indicators of inadequate processing or post process contamination. Staphylococci are associated with human skin and therefore their presence on surfaces may be as a result of transfer from food handlers. In addition, Mettler and Carpentier(1998) studied the microflora associated with the surfaces in milk, meat and pastry sites and concluded that the micro-flora was specific to the processing environment Bacteria adhering to the food product contact surfaces may be an important source of potential contamination leading to serious hygienic problems and economic losses due to food spoilage. For example, pseudomonads and many other Gram negative organisms detected on surfaces are the spoilage organisms of concern in chilled foods. The survival of organisms in biofilms may be a source of post process contamination, resulting in reduced shelf life of the oroduct. In addition, Listeria monocytogenes has been isolated from a range of food processing surfaces( Walker et al. 1991, Lawrence and Gilmore 1995 and Destro et al. 1996)and is usually looked for in high-risk processing areas via the company environmental sampling plan Following HACCP principles, if the food processor believes that biofilms are a risk to the safety of the food product, appropriate control steps must be taken. These would include providing an environment in which the formation of the biofilm would be limited, undertaking cleaning and disinfection programmes as required, monitoring and controlling these programmes to ensure their success during their operation and verifying their performance by a suitable(usually microbiological)assessment. Within the sanitation programme, the cleaning phase can be divided up into three stages, following the pioneering work of Jennings(1965) and interpreted by Koopal (1985), with the addition of a fourth stage to cover disinfection These are described below 1. The wetting and penetration by the cleaning solution of both the soil and the equipment surface. 2. The reaction of the cleaning solution with both the soil and the surface to facilitate: peptisation of organic materials, dissolution of soluble organics and minerals, emulsification of fats and the dispersion and removal from the surface of solid soil components(1995) and Kumar and Anand, (1998). In general, however, biofilm formation is usually found only on environmental surfaces, and progression of attached cells through microcolonies to extensive biofilm is limited by regular cleaning and disinfection. Gibson et al.(1995) in studies of attached microorganisms in 17 different processing environments, recorded 79% of isolates as Gram negative rods, 8.6% Gram positive cocci, 6.5% Gram positive rods and 1.2% yeast strains. The most common organisms were Pseudomonas, Staphylococcus and Enterobacter spp. Pseudomonads are environmental psychrotrophic organisms that readily attach to surfaces and are common spoilage organsisms in chilled foods. Other common Gram negatives that have been associated with surfaces are coliform organisms that are widely distributed in the environment and may also be indicators of inadequate processing or post process contamination. Staphylococci are associated with human skin and therefore their presence on surfaces may be as a result of transfer from food handlers. In addition, Mettler and Carpentier (1998) studied the microflora associated with the surfaces in milk, meat and pastry sites and concluded that the micro-flora was specific to the processing environment. Bacteria adhering to the food product contact surfaces may be an important source of potential contamination leading to serious hygienic problems and economic losses due to food spoilage. For example, pseudomonads and many other Gram negative organisms detected on surfaces are the spoilage organisms of concern in chilled foods. The survival of organisms in biofilms may be a source of post process contamination, resulting in reduced shelf life of the product. In addition, Listeria monocytogenes has been isolated from a range of food processing surfaces (Walker et al. 1991, Lawrence and Gilmore 1995 and Destro et al. 1996) and is usually looked for in high-risk processing areas via the company environmental sampling plan. Following HACCP principles, if the food processor believes that biofilms are a risk to the safety of the food product, appropriate control steps must be taken. These would include providing an environment in which the formation of the biofilm would be limited, undertaking cleaning and disinfection programmes as required, monitoring and controlling these programmes to ensure their success during their operation and verifying their performance by a suitable (usually microbiological) assessment. Within the sanitation programme, the cleaning phase can be divided up into three stages, following the pioneering work of Jennings (1965) and interpreted by Koopal (1985), with the addition of a fourth stage to cover disinfection. These are described below. 1. The wetting and penetration by the cleaning solution of both the soil and the equipment surface. 2. The reaction of the cleaning solution with both the soil and the surface to facilitate: peptisation of organic materials, dissolution of soluble organics and minerals, emulsification of fats and the dispersion and removal from the surface of solid soil components. Cleaning and disinfection 399