Cleaning and disinfection 405 programme, there are likely to be sufficient viable microorganisms remaining on the surface to warrant the application of a disinfectant. The aim of disinfection is therefore to further reduce the surface population of viable microorganisms, via removal or destruction, and/or to prevent surface microbial growth during the inter-production period. Elevated temperature is the best disinfectant as it penetrates into surfaces, is non-corrosive, is non-selective to microbial types, is easily measured and leaves no residue ( Jennings 1965). However, for open surfaces, the use of hot water or steam is uneconomic, hazardous or impossible and reliance is, therefore, placed on chemical biocides Whilst there are many chemicals with biocidal properties, many common disinfectants are not used in food applications because of safety or taint problems, e.g. phenolics or metal-ion-based products. In addition, other disinfectants are used to a limited extent only in chilled food manufacture and/or for specific purposes, e.g. peracetic acid, biguanides, formaldehyde glutaraldehyde, organic acids, ozone, chlorine dioxide, bromine and iodine ompounds. Of the acceptable chemicals, the most commonly used products are chlorine-releasing components quaternary ammonium compound amphoterics quaternary ammonium/amphoteric mixtures Chlorine is the cheapest disinfectant and is available as hypochlorite (or occasionally as chlorine gas) or in slow releasing forms(e.g. chloramines, dichlorodimethy hydantoin). Quaternary ammonium compounds ( Quats o DACs)are amphipolar, cationic detergents, derived from substituted ammonium salts with a chlorine or bromine anion and amphoterics are based on the amino acid glycine, often incorporating an imidazole group In a( CCFRA) survey undertaken of the UK food industry in 1987, of 145 applications of disinfectants 52% were chlorine based, 37% were quaternary ammonium compounds and 8% were amphoterics. Of these biocides there were respectively, 44, 30 and 8 branded products used. In a(CCFRA)European survey of 1993, the most common disinfectants used in the Uk and Scandinavian countries were QACs for open surfaces and peracetic acid and chlorine for closed, liquid handling surfaces. The survey also showed that open surfaces were usually cleaned with alkaline detergents which were foamed and then rinsed with medium pressure water(250psi)and closed systems were CIP cleaned with caustic followed by acidic detergents with a suitable rinse in- between. A survey of the approved disinfectant products in Germany (DVG listed) in 1994 indicated that 36% were QACs, 20% were mixtures of QACs with aldehydes or biguanides and 10% were amphoterics(Knauer-Kraetzl 1994). More recently the synergistic combinations of QACs and amphoterics have been explored in the UK and these compounds are now widely used in The characteristics of the most commonly used are 143. The properties of QAC/amphoteric mixes will be lar to their parent compounds with often enhanced microorganism contrprogramme, there are likely to be sufficient viable microorganisms remaining on the surface to warrant the application of a disinfectant. The aim of disinfection is therefore to further reduce the surface population of viable microorganisms, via removal or destruction, and/or to prevent surface microbial growth during the inter-production period. Elevated temperature is the best disinfectant as it penetrates into surfaces, is non-corrosive, is non-selective to microbial types, is easily measured and leaves no residue (Jennings 1965). However, for open surfaces, the use of hot water or steam is uneconomic, hazardous or impossible, and reliance is, therefore, placed on chemical biocides. Whilst there are many chemicals with biocidal properties, many common disinfectants are not used in food applications because of safety or taint problems, e.g. phenolics or metal-ion-based products. In addition, other disinfectants are used to a limited extent only in chilled food manufacture and/or for specific purposes, e.g. peracetic acid, biguanides, formaldehyde, glutaraldehyde, organic acids, ozone, chlorine dioxide, bromine and iodine compounds. Of the acceptable chemicals, the most commonly used products are: • chlorine-releasing components • quaternary ammonium compounds • amphoterics • quaternary ammonium/amphoteric mixtures. Chlorine is the cheapest disinfectant and is available as hypochlorite (or occasionally as chlorine gas) or in slow releasing forms (e.g. chloramines, dichlorodimethylhydantoin). Quaternary ammonium compounds (Quats or QACs) are amphipolar, cationic detergents, derived from substituted ammonium salts with a chlorine or bromine anion and amphoterics are based on the amino acid glycine, often incorporating an imidazole group. In a (CCFRA) survey undertaken of the UK food industry in 1987, of 145 applications of disinfectants 52% were chlorine based, 37% were quaternary ammonium compounds and 8% were amphoterics. Of these biocides there were, respectively, 44, 30 and 8 branded products used. In a (CCFRA) European survey of 1993, the most common disinfectants used in the UK and Scandinavian countries were QACs for open surfaces and peracetic acid and chlorine for closed, liquid handling surfaces. The survey also showed that open surfaces were usually cleaned with alkaline detergents which were foamed and then rinsed with medium pressure water (250psi) and closed systems were CIP cleaned with caustic followed by acidic detergents with a suitable rinse in￾between. A survey of the approved disinfectant products in Germany (DVG listed) in 1994 indicated that 36% were QACs, 20% were mixtures of QACs with aldehydes or biguanides and 10% were amphoterics (Knauer-Kraetzl 1994). More recently the synergistic combinations of QACs and amphoterics have been explored in the UK and these compounds are now widely used in chilled food plants. The characteristics of the most commonly used are compared in Table 14.3. The properties of QAC/amphoteric mixes will be similar to their parent compounds with often enhanced microorganism control. Cleaning and disinfection 405