402 Chilled foods processing applications and can range from hours(e.g. heat exchangers)to typically several days or weeks, and in practice is controlled by the application of a ' clean(Dunsmore et al. 1981). Periodic cleans are employed to return the surface-bound soil accumulation to an acceptable base level(plot B, ig. 14.1(b)and are achieved by increasing cleaning time and/or energy input, e.g. higher temperatures, alternative chemicals or manual scrubbing. A typical example of a periodic clean is the week-end clean down or ' bottoming 14.3 Sanitation chemicals In many instances, management view the costs of cleaning and disinfection as the price of the chemicals purchased, primarily because this is the only"invoice that they see. In reality, however, sanitation chemicals are likely to represent approximately only 5% of the true costs, with labour and water costs being the most significant. The purchase of a good quality formulated cleaning product, whilst being initially more expensive, will more than cover its costs by oth the standard of clean and cle Within the sanitation programme it has traditionally been recognised that cleaning is responsible for the removal of not only the soil but also the majority of the microorganisms present Mrozek(1982) showed a reduction in bacterial numbers on surfaces by up to 3 log orders whilst Schmidt and Cremling(1981) described reductions of 2-6 log orders The results of work at CCfrA on the assessment of well constructed and competently undertaken sanitation programmes on food processing equipment in eight chilled food factories is shown in Table 14.1. The results suggest that both cleaning and disinfection are equally responsible for reducing the levels of adhered microorganisms. It is important, therefore, not only to purchase quality cleaning chemicals for their soil removal capabilities but also for their potential for microbial removal Unfortunately no single cleaning agent is able to perform all the functions necessary to facilitate a successful cleaning programme; so a cleaning solution, or detergent, is blended from a range of typical characteristic components urfactants · inorganic alkalis Table 14.1 Arithmetic and log mean bacterial counts on food processing equipment before and after cleaning and after disinfection Before cleaning After cleaning After disinfection Arithmetic mean 867×104 2.5×103 g mean No of observations 3147
processing applications and can range from hours (e.g. heat exchangers) to typically several days or weeks, and in practice is controlled by the application of a ‘periodic’ clean (Dunsmore et al. 1981). Periodic cleans are employed to return the surface-bound soil accumulation to an acceptable base level (plot B, Fig. 14.1(b)) and are achieved by increasing cleaning time and/or energy input, e.g. higher temperatures, alternative chemicals or manual scrubbing. A typical example of a periodic clean is the ‘week-end clean down’ or ‘bottoming’. 14.3 Sanitation chemicals In many instances, management view the costs of cleaning and disinfection as the price of the chemicals purchased, primarily because this is the only ‘invoice’ that they see. In reality, however, sanitation chemicals are likely to represent approximately only 5% of the true costs, with labour and water costs being the most significant. The purchase of a good quality formulated cleaning product, whilst being initially more expensive, will more than cover its costs by increasing both the standard of clean and cleaning efficiency. Within the sanitation programme it has traditionally been recognised that cleaning is responsible for the removal of not only the soil but also the majority of the microorganisms present. Mrozek (1982) showed a reduction in bacterial numbers on surfaces by up to 3 log orders whilst Schmidt and Cremling (1981) described reductions of 2–6 log orders. The results of work at CCFRA on the assessment of well constructed and competently undertaken sanitation programmes on food processing equipment in eight chilled food factories is shown in Table 14.1. The results suggest that both cleaning and disinfection are equally responsible for reducing the levels of adhered microorganisms. It is important, therefore, not only to purchase quality cleaning chemicals for their soil removal capabilities but also for their potential for microbial removal. Unfortunately no single cleaning agent is able to perform all the functions necessary to facilitate a successful cleaning programme; so a cleaning solution, or detergent, is blended from a range of typical characteristic components: • water • surfactants • inorganic alkalis Table 14.1 Arithmetic and log mean bacterial counts on food processing equipment before and after cleaning and after disinfection Before cleaning After cleaning After disinfection Arithmetic mean 1.32106 8.67104 2.5103 log mean 3.26 2.35 1.14 No. of observations 498 1090 3147 402 Chilled foods
Cleaning and disinfection 40 inorganic and organic acids · sequestering agents For the majority of food processing operations it may be necessary, therefore employ a number of cleaning products, for specific operations. This requirement must be balanced by the desire to keep the range of cleaning chemicals on site to a minimum so as to reduce the risk of using the wrong product, to simplify the b of the safety officer and to allow chemical purchase to be based more on the economics of bulk quantities. The range of chemicals and their purposes is well documented(Anon. 1991, Elliot 1980, ICMSF 1980, 1988, Hayes 1985, Holah 1991, Koopal 1985, Russell et al. 1982)and only an overview of the principles is given here. Water is the base ingredient of allwet cleaning systems and must be of table quality. Water provides the cheapest readily available transport medium for rinsing and dispersing soils, has dissolving powers to remove ionic-soluble compounds such as salts and sugars, will help emulsify fats at temperatures above their melting point, and, in high-pressure cleaning, can be used as an abrasive agent. On its own, however, water is a poor wetting agent and cannot dissolve non-ionic compounds Organic surfactants(surface-active or wetting agents)are amphipolar and are omposed of a long non-polar(hydrophobic or lyophilic) chain or tail and a polar(hydrophilic or lyophobic) head. Surfactants are classified as anionic (including the traditional soaps), cationic, or non-ionic, depending on their ionic charge in solution, with anionics and non-ionics being the most common Amphipolar molecules aid cleaning by reducing the surface tension of water and by emulsification of fats. If a surfactant is added to a drop of water on a surface the polar heads disrupt the waters hydrogen bonding and so reduce the surface tension of the water and allow the drop to collapse andwet' the surface Increased wettability leads to enhanced penetration into soils and surface irregularities and hence aids cleaning action. Fats and oils are emulsified as the hydrophilic heads of the surfactant molecules dissolve in the water whilst the hydrophobic end dissolves in the fat. If the fat is surface-bound, the forces acting on the fat/water interface are such that the fat particle will form a sphere(to obtain the lowest surface area for its given volume) causing the fat deposit to roll-up' and detach itself from the surface. lkalis are useful cleaning agents as they are cheap, break down proteins through the action of hydroxyl ions, saponify fats and, at higher concentrations, may be bactericidal. Strong alkalis, usually sodium hydroxide(or caustic soda) exhibit a high degree of saponification and protein disruption, though they are corrosive and hazardous to operatives. Correspondingly, weak alkalis are less hazardous but also less effective. Alkaline detergents may be chlorinated to aid the removal of proteinaceous deposits, but chlorine at alkaline ph is not an effective biocide. The main disadvantages of alkalis are their potential to precipitate hard water ions, the formation of scums with soaps, and their poor disability
• inorganic and organic acids • sequestering agents. For the majority of food processing operations it may be necessary, therefore, to employ a number of cleaning products, for specific operations. This requirement must be balanced by the desire to keep the range of cleaning chemicals on site to a minimum so as to reduce the risk of using the wrong product, to simplify the job of the safety officer and to allow chemical purchase to be based more on the economics of bulk quantities. The range of chemicals and their purposes is well documented (Anon. 1991, Elliot 1980, ICMSF 1980, 1988, Hayes 1985, Holah 1991, Koopal 1985, Russell et al. 1982) and only an overview of the principles is given here. Water is the base ingredient of all ‘wet’ cleaning systems and must be of potable quality. Water provides the cheapest readily available transport medium for rinsing and dispersing soils, has dissolving powers to remove ionic-soluble compounds such as salts and sugars, will help emulsify fats at temperatures above their melting point, and, in high-pressure cleaning, can be used as an abrasive agent. On its own, however, water is a poor ‘wetting’ agent and cannot dissolve non-ionic compounds. Organic surfactants (surface-active or wetting agents) are amphipolar and are composed of a long non-polar (hydrophobic or lyophilic) chain or tail and a polar (hydrophilic or lyophobic) head. Surfactants are classified as anionic (including the traditional soaps), cationic, or non-ionic, depending on their ionic charge in solution, with anionics and non-ionics being the most common. Amphipolar molecules aid cleaning by reducing the surface tension of water and by emulsification of fats. If a surfactant is added to a drop of water on a surface, the polar heads disrupt the water’s hydrogen bonding and so reduce the surface tension of the water and allow the drop to collapse and ‘wet’ the surface. Increased wettability leads to enhanced penetration into soils and surface irregularities and hence aids cleaning action. Fats and oils are emulsified as the hydrophilic heads of the surfactant molecules dissolve in the water whilst the hydrophobic end dissolves in the fat. If the fat is surface-bound, the forces acting on the fat/water interface are such that the fat particle will form a sphere (to obtain the lowest surface area for its given volume) causing the fat deposit to ‘roll-up’ and detach itself from the surface. Alkalis are useful cleaning agents as they are cheap, break down proteins through the action of hydroxyl ions, saponify fats and, at higher concentrations, may be bactericidal. Strong alkalis, usually sodium hydroxide (or caustic soda), exhibit a high degree of saponification and protein disruption, though they are corrosive and hazardous to operatives. Correspondingly, weak alkalis are less hazardous but also less effective. Alkaline detergents may be chlorinated to aid the removal of proteinaceous deposits, but chlorine at alkaline pH is not an effective biocide. The main disadvantages of alkalis are their potential to precipitate hard water ions, the formation of scums with soaps, and their poor rinsability. Cleaning and disinfection 403
404 Chilled foods Acids have little detergency properties, although they are very useful in making soluble carbonate and mineral scales, including hard water salts and proteinaceous deposits. As with alkalis, the stronger the acid the more effective it is; though, in addition, the more corrosive to plant and operatives. Acids are not used as frequently as alkalis in chilled food operations and tend to be used Sequestering agents(sequestrants or chelating agents) are employed to prevent mineral ions precipitating by forming soluble complexes with them Their primary use is in the control of water hardness ions and they are added to surfactants to aid their dispersion capacity and rinsability. Sequestrants are most commonly based on ethylene diamine tetracetic acid (EDTA), which is expensive. Although cheaper alternatives are available, these are usually polyphosphates which are environmentally unfriendly A general-purpose food detergent may, therefore, contain a strong alkali to saponify fats, weaker alkali"builders'or" agents, surfactants to improve wetting, dispersion and rinsability and sequestrants to control hard water ions. In addition, the detergent should ideally be safe, non-tainting, non-corrosive, stable, environmentally friendly and cheap. The choice of cleaning agent will depend on the soil to be removed and on its solubility characteristics, and these are summar- ised for a range of chilled products in Table 14.2(modified from Elliot 1980 Because of the wide range of food soils likely to be encountered and fluence of the food manufacturing site(temperature, humidity, type of equipment, time before cleaning, etc. ) there are currently no recognised laboratory methods for assessing the efficacy of cleaning compounds. Food manufacturers have to be satisfied that cleaning chemicals are working appropriately, by conducting suitable field trials. Although the majority of the microbial contamination is removed by the cleaning phase of the sanitation Table 14.2 Solubility characteristics and cleaning procedures recommended for a rang of soil types Soil type Solubility characteristics Cleaning procedure Sugars, organic Mildly alkaline detergent High protein food Water-soluble Chlorinated alkaline detergent poultry, fish) Alkali-soluble Slightly acid-soluble Starchy foods, tomatoes, Partly water-soluble Mildly alkaline detergent fruits Alkali-soluble Fatty foods(fat, butter, Water-insoluble Alkaline-soluble Heat-precipitated water Water-insoluble Acid cleaner used on a hardness. milk stone Alkaline-insoluble protein scale Acid-soluble
Acids have little detergency properties, although they are very useful in making soluble carbonate and mineral scales, including hard water salts and proteinaceous deposits. As with alkalis, the stronger the acid the more effective it is; though, in addition, the more corrosive to plant and operatives. Acids are not used as frequently as alkalis in chilled food operations and tend to be used for periodic cleans. Sequestering agents (sequestrants or chelating agents) are employed to prevent mineral ions precipitating by forming soluble complexes with them. Their primary use is in the control of water hardness ions and they are added to surfactants to aid their dispersion capacity and rinsability. Sequestrants are most commonly based on ethylene diamine tetracetic acid (EDTA), which is expensive. Although cheaper alternatives are available, these are usually polyphosphates which are environmentally unfriendly. A general-purpose food detergent may, therefore, contain a strong alkali to saponify fats, weaker alkali ‘builders’ or ‘bulking’ agents, surfactants to improve wetting, dispersion and rinsability and sequestrants to control hard water ions. In addition, the detergent should ideally be safe, non-tainting, non-corrosive, stable, environmentally friendly and cheap. The choice of cleaning agent will depend on the soil to be removed and on its solubility characteristics, and these are summarised for a range of chilled products in Table 14.2 (modified from Elliot 1980). Because of the wide range of food soils likely to be encountered and the influence of the food manufacturing site (temperature, humidity, type of equipment, time before cleaning, etc.), there are currently no recognised laboratory methods for assessing the efficacy of cleaning compounds. Food manufacturers have to be satisfied that cleaning chemicals are working appropriately, by conducting suitable field trials. Although the majority of the microbial contamination is removed by the cleaning phase of the sanitation Table 14.2 Solubility characteristics and cleaning procedures recommended for a range of soil types Soil type Solubility characteristics Cleaning procedure recommended Sugars, organic acids, salt Water-soluble Mildly alkaline detergent High protein foods (meat, Water-soluble Chlorinated alkaline detergent poultry, fish) Alkali-soluble Slightly acid-soluble Starchy foods, tomatoes, Partly water-soluble Mildly alkaline detergent fruits Alkali-soluble Fatty foods (fat, butter, Water-insoluble Mildly alkaline detergent; if margarine, oils) Alkaline-soluble ineffective, use strong alkali Heat-precipitated water Water-insoluble Acid cleaner, used on a hardness, milk stone, Alkaline-insoluble periodic basis protein scale Acid-soluble 404 Chilled foods
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 contr
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 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 inbetween. 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
406 Chilled foods Table 14.3 Characteristics of some universal disinfectants Property Chlorine QAC Amphoteric Peracetic M Spores Developed microbial resistance Inactivation by organic matter er Detergency properties Surface activity Corrosion Potential environmental impact Cost no effect(or problem) ++large effect Within the chilled food industry, particularly for mid-shift cleaning and disinfection in high-risk areas, alcohol based products are commonly used. This is primarily to restrict the use of water for cleaning during production as a control measure to prevent the growth and spread of any food pathogens that penetrate the high-risk area barrier controls. Ethyl alcohol (ethanol) and isopropyl alcohol(isopropanol)have bactericidal and virucidal(but not poricidal) properties(Hugo and Russell 1999), though they are only active in he absence of organic matter i.e. the surfaces need to be wiped clean and then alcohol reapplied. Alcohols are most active in the 60-70% range, and can be formulated into wipe and spray based products. Alcohol products are used on a small, local scale because of their well recognised health and safety issues The efficacy of disinfectants is generally controlled by five factors nterfering substances(primarily organic matter), pH, temperature, concentra- tion and contact time. To some extent, and particularly for the oxidative biocides, the efficiency of all disinfectants is reduced in the presence of organic matter. Organic material may react chemically with the disinfectant such that it oses its biocidal potency, or spatially such that microorganisms are protected from its effect. Other interfering substances, e.g. cleaning chemicals, may react
Within the chilled food industry, particularly for mid-shift cleaning and disinfection in high-risk areas, alcohol based products are commonly used. This is primarily to restrict the use of water for cleaning during production as a control measure to prevent the growth and spread of any food pathogens that penetrate the high-risk area barrier controls. Ethyl alcohol (ethanol) and isopropyl alcohol (isopropanol) have bactericidal and virucidal (but not sporicidal) properties (Hugo and Russell 1999), though they are only active in the absence of organic matter i.e. the surfaces need to be wiped clean and then alcohol reapplied. Alcohols are most active in the 60–70% range, and can be formulated into wipe and spray based products. Alcohol products are used on a small, local scale because of their well recognised health and safety issues. The efficacy of disinfectants is generally controlled by five factors: interfering substances (primarily organic matter), pH, temperature, concentration and contact time. To some extent, and particularly for the oxidative biocides, the efficiency of all disinfectants is reduced in the presence of organic matter. Organic material may react chemically with the disinfectant such that it loses its biocidal potency, or spatially such that microorganisms are protected from its effect. Other interfering substances, e.g. cleaning chemicals, may react Table 14.3 Characteristics of some universal disinfectants Property Chlorine QAC Amphoteric Peracetic acid Microorganism control Gram-positive + + + + + + + + Gram-negative + + + + + + + Spores + + + Yeast + + + + + + + + Developed microbial resistance + + Inactivation by organic matter + + + + + water hardness + Detergency properties ++ + Surface activity ++ ++ Foaming potential ++ ++ Problems with taints +/ +/ Stability +/ +/ Corrosion + Safety + + + Other chemicals + Potential environmental impact + + /+ /+ Cost ++ ++ + no effect (or problem). + effect. + + large effect. 406 Chilled foods