The evolution of microbiological risk assessment 7 Because the underlying causes of foodborne illness were unknown, microbial food poisoning was recurrent. However, the situation changed after 1795, when the French government, driven by war, offered a substantial reward for anyone developing a new method of preserving food. It was Nicholas Appert, a Parisian confectioner, who accepted the challenge and developed a wide-mouth glass bottle that was filled with food corked and heated in boiling water for about six hours. In 1810, Durand in England patented the use of tin cans for thermal processing of foods, but neither Appert nor Durand understood why thermally processed foods did not spoil (Hartman, 1997), despite the fact that in 1677 van Leeuwenhoek had discovered his little heat-sensitive animalcules'(Dobell, 1960) Louis Pasteur provided the scientific basis for heat preservation in the period 1854-1864. During this time, he showed that certain bacteria were either ssociated with food spoilage or caused specific diseases. Based on Pasteur's indings, commercial heat treatment of wine was first introduced in 1867to destroy any undesirable microorganisms, and the process was described pasteurisation. Another important development occurred in Germany, when Robert Koch introduced a method of growing microorganisms in pure culture and with colleagues first isolated the vibrio cholerae bacterium in 1884, during a worldwide pandemic( Chung et al., 1995). Over the next 100 years or more, laboratory isolation and study of pure cultures of microbes remained among the predominant activities of food microbiologists(Hartman, 1997) 2.3 The evolution of food safety systems When it was accepted that people could contract disease from contaminated food, hygiene control laws were introduced and examples can be seen in old legal records. Table 2. 1 gives an overview of the more important milestones in developing food safety systems. In the absence of knowledge about the causes of serious foodborne diseases and their etiology, use was made of the prohibition principle. This means that it was prohibited to produce and/or to consume certain types of food after it was realised that the foods could be a cause of high mortality. The principle was used particularly to protect special groups of individuals within society, such as soldiers. After the recognition at the end of the nineteenth century that microbial agents were often responsible for foodborne illness, systems for controlling the safety of the food supply began to be introduced First, use was made of microbiological testing of foods and this became widely accepted as a means of assessing food safety during the early part of the twentieth century. Eventually, statutory microbiological requirements relating food safety were established in parts of the world. Further progress occurred when Esty and Meyer(1922)developed the concept of setting process performance criteria for heat treat of low-acid canned food products to reduce the risk of botulism. Later, many other foods processed in this way were controlled in a similar manner. An outstanding example is the work of Enright er
Because the underlying causes of foodborne illness were unknown, microbial food poisoning was recurrent. However, the situation changed after 1795, when the French government, driven by war, offered a substantial reward for anyone developing a new method of preserving food. It was Nicholas Appert, a Parisian confectioner, who accepted the challenge and developed a wide-mouth glass bottle that was filled with food, corked and heated in boiling water for about six hours. In 1810, Durand in England patented the use of tin cans for thermal processing of foods, but neither Appert nor Durand understood why thermally processed foods did not spoil (Hartman, 1997), despite the fact that in 1677 van Leeuwenhoek had discovered ‘his little heat-sensitive animalcules’ (Dobell, 1960). Louis Pasteur provided the scientific basis for heat preservation in the period 1854–1864. During this time, he showed that certain bacteria were either associated with food spoilage or caused specific diseases. Based on Pasteur’s findings, commercial heat treatment of wine was first introduced in 1867 to destroy any undesirable microorganisms, and the process was described as ‘pasteurisation’. Another important development occurred in Germany, when Robert Koch introduced a method of growing microorganisms in pure culture and, with colleagues, first isolated the vibrio cholerae bacterium in 1884, during a worldwide pandemic (Chung et al., 1995). Over the next 100 years or more, laboratory isolation and study of pure cultures of microbes remained among the predominant activities of food microbiologists (Hartman, 1997). 2.3 The evolution of food safety systems When it was accepted that people could contract disease from contaminated food, hygiene control laws were introduced and examples can be seen in old legal records. Table 2.1 gives an overview of the more important milestones in developing food safety systems. In the absence of knowledge about the causes of serious foodborne diseases and their etiology, use was made of the ‘prohibition’ principle. This means that it was prohibited to produce and/or to consume certain types of food after it was realised that the foods could be a cause of high mortality. The principle was used particularly to protect special groups of individuals within society, such as soldiers. After the recognition at the end of the nineteenth century that microbial agents were often responsible for foodborne illness, systems for controlling the safety of the food supply began to be introduced. First, use was made of microbiological testing of foods and this became widely accepted as a means of assessing food safety during the early part of the twentieth century. Eventually, statutory microbiological requirements relating to food safety were established in many parts of the world. Further progress occurred when Esty and Meyer (1922) developed the concept of setting process performance criteria for heat treatment of low-acid canned food products to reduce the risk of botulism. Later, many other foods processed in this way were controlled in a similar manner. An outstanding example is the work of Enright et The evolution of microbiological risk assessment 7
8 Microbiological risk assessment in food processing Table 2.1 Important milestones in the development of food safety syster Til Use of prohibition' principle to protect special groups within society against foodborne illnesses Microbiological examination of food Introduction of process performance criteria by Esty Meyer for canned, low-acid food products 1930-1960 Use of risk assessment(for differen etting process performance criteria for heat pasteurisation of milk Introduction of good manufacturing practices Introduction of formal hazard analysis critical control point system ca1978 Start of predictive modelling of bacterial growth in food 1995 Introduction of formal quantitative risk analysis al. (1956, 1957)who established performance criteria for the pasteurisation of milk that provided an appropriate level of protection against Coxiella burneti the causative agent of Q fever. Studies for tuberculosis had been carried out earlier. This work is an early example of the use of risk assessment principles in deriving process criteria with greater knowledge of the more important foodborne diseases and the establishment of risk factors from analyses of outbreaks came the development of more comprehensive means of controlling food safety in production. These included the elaboration of good manufacturing practice(GMP), which helps to minimise microbial contamination of food from personnel and the production environment, and, ultimately, the hazard analysis critical control point(HACCP) system(Department of Health, Education and Welfare, 1972), in which GMP plays an important part The ability of different bacteria to multiply in foods is influenced by sever key factors, including pH, water activity and storage temperature. The effects of these factors, both singularly and in combination, have been studied extensively in laboratory media and model food systems, and this has led to the development of mathematical models for predicting bacterial growth in commercial food products. Although not a food safety system on its own, predictive modelling is a valuable tool, which has helped to make possible the introduction of quantitive risk assessment(QRA). The latter has been used for many years in other disciplines and its use in food microbiology has been stimulated by the decision of the World Trade Organisation(WTO)to promote free trade in safe food (Anon, 1995). It has been emphasised, however, that control of food safety this context must be based on the application of sound scientific principles, and risk analysis is seen as the basis for ensuring that the requirement is met The next sub-section gives more detailed information on the above mentioned food safety initiatives, with special reference to risk assessment procedures
al. (1956, 1957) who established performance criteria for the pasteurisation of milk that provided an appropriate level of protection against Coxiella burnetii, the causative agent of Q fever. Studies for tuberculosis had been carried out earlier. This work is an early example of the use of risk assessment principles in deriving process criteria. With greater knowledge of the more important foodborne diseases and the establishment of risk factors from analyses of outbreaks came the development of more comprehensive means of controlling food safety in production. These included the elaboration of good manufacturing practice (GMP), which helps to minimise microbial contamination of food from personnel and the production environment, and, ultimately, the hazard analysis critical control point (HACCP) system (Department of Health, Education and Welfare, 1972), in which GMP plays an important part. The ability of different bacteria to multiply in foods is influenced by several key factors, including pH, water activity and storage temperature. The effects of these factors, both singularly and in combination, have been studied extensively in laboratory media and model food systems, and this has led to the development of mathematical models for predicting bacterial growth in commercial food products. Although not a food safety system on its own, predictive modelling is a valuable tool, which has helped to make possible the introduction of quantitive risk assessment (QRA). The latter has been used for many years in other disciplines and its use in food microbiology has been stimulated by the decision of the World Trade Organisation (WTO) to promote free trade in safe food (Anon., 1995). It has been emphasised, however, that control of food safety in this context must be based on the application of sound scientific principles, and risk analysis is seen as the basis for ensuring that the requirement is met. The next sub-section gives more detailed information on the abovementioned food safety initiatives, with special reference to risk assessment procedures. Table 2.1 Important milestones in the development of food safety systems Time Activity Distant past Use of ‘prohibition’ principle to protect special groups within society against foodborne illnesses 1900 to present Microbiological examination of food 1922 Introduction of process performance criteria by Esty & Meyer for canned, low-acid food products 1930–1960 Use of risk assessment (for different pathogenic organisms) in setting process performance criteria for heat pasteurisation of milk 1960 Introduction of good manufacturing practices 1971 Introduction of formal hazard analysis critical control point system ca 1978 Start of predictive modelling of bacterial growth in food 1995 Introduction of formal quantitative risk analysis 8 Microbiological risk assessment in food processing
The evolution of microbiological risk assessment 9 2.3.1 Theprohibition'principle As their trade in food increased, the romans paid greater attention to the question of preventing spoilage, and a new rule emerged: it was prohibited to sell spoiled food of any kind. The aedilis(churchwarden) inspected and controlled food markets, and was charged with confiscating any food that had become spoiled. Over the last 2000 years, the prohibition principle has continued to be applied in many societies to protect consumers from both spoiled food and that likely to contain deadly disease agents. Some examples are given below Consumption of blood products In an historical account of food safety measures, Baird-Parker(2000)describes the action taken by Emperor Leo VI of Byzantium(AD 886-911). The Emperor introduced an outright ban on the consumption of blood products as a means of reducing the high incidence of poisoning associated with sausages among his people. The law applied particularly to blood sausages and carried a high penalty if it was disregarded, which indicates the seriousness of the problem. It was stated: 'A person found to have blood prepared as food, whether he buys or sells it, shall have all his property confiscated and, after having been severely scourged and disgracefully shaved, shall be exiled for life. From the data available and current expert knowledge, it is clear that the blood diseasewas actually botulist Selling of contagious flesh In a document entitled 'A history of government regulation of adulteration and misbranding of food, Hutt and Hutt (1984) refer to the English Statute of Pillory and Thumbrell(1266/67). This required the following: If any butcher do sell contagious flesh or which has died from the murrain(rinderpest), he must be punished. The customary punishment was to be placed in the stocks with the offending meat buried underneath Unsold fish In 1319, the municipal authorities in Zurich, Switzerland, issued an ordinance prohibiting the sale of any fish that had been left over from the day before. A similar rule also operated in the city of Basel. However, such fish, could still be sold to strangers(Kampelmacher, 1971) ing of pufferfish In Japan, a dish known as fugu'is, historically, one of the most favoured and heraldic forms of fish eating Nevertheless, consumption of this food has resulted in many deaths, and the problem continues to this day. Consumption of the delicacy was banned in 1550 by the Emperor, after a group of soldiers had died. but the ban was abolished in 1888 when the Japanese Prime Minister tasted a small sample of fugu and survived. This disease is known as blowfish or pufferfish poisoning and is due to the neurotoxic effects of the tetrodotoxin
2.3.1 The ‘prohibition’ principle As their trade in food increased, the Romans paid greater attention to the question of preventing spoilage, and a new rule emerged: it was prohibited to sell spoiled food of any kind. The aedilis (churchwarden) inspected and controlled food markets, and was charged with confiscating any food that had become spoiled. Over the last 2000 years, the ‘prohibition’ principle has continued to be applied in many societies to protect consumers from both spoiled food and that likely to contain deadly disease agents. Some examples are given below. Consumption of blood products In an historical account of food safety measures, Baird-Parker (2000) describes the action taken by Emperor Leo VI of Byzantium (AD 886–911). The Emperor introduced an outright ban on the consumption of blood products as a means of reducing the high incidence of poisoning associated with sausages among his people. The law applied particularly to blood sausages and carried a high penalty if it was disregarded, which indicates the seriousness of the problem. It was stated: ‘A person found to have blood prepared as food, whether he buys or sells it, shall have all his property confiscated and, after having been severely scourged and disgracefully shaved, shall be exiled for life.’ From the data available and current expert knowledge, it is clear that the ‘blood disease’ was actually botulism. Selling of contagious flesh In a document entitled ‘A history of government regulation of adulteration and misbranding of food,’ Hutt and Hutt (1984) refer to the English Statute of Pillory and Thumbrell (1266/67). This required the following: ‘If any butcher do sell contagious flesh or which has died from the murrain (rinderpest), he must be punished.’ The customary punishment was to be placed in the stocks with the offending meat buried underneath. Unsold fish In 1319, the municipal authorities in Zurich, Switzerland, issued an ordinance prohibiting the sale of any fish that had been left over from the day before. A similar rule also operated in the city of Basel. However, such fish, could still be sold to strangers (Kampelmacher, 1971). Eating of pufferfish In Japan, a dish known as ‘fugu’ is, historically, one of the most favoured and heraldic forms of fish eating Nevertheless, consumption of this food has resulted in many deaths, and the problem continues to this day. Consumption of the delicacy was banned in 1550 by the Emperor, after a group of soldiers had died, but the ban was abolished in 1888 when the Japanese Prime Minister tasted a small sample of fugu and survived. This disease is known as blowfish or pufferfish poisoning and is due to the neurotoxic effects of the tetrodotoxin, The evolution of microbiological risk assessment 9
10 Microbiological risk assessment in food processing which occurs in various species of pufferfish. The dish is now prepared only by chefs who have been specially trained and certified by the Japanese government and can be relied upon to free the flesh of the toxic liver, gonads and skin Despite these precautions, many cases of tetrodotoxin poisoning are reported each year in people consuming fugu(Source: Medical Journal, 12 June, 2001 vol. 2, no 6) In the Regency of Banyumas and surrounding areas of Central Java, Indonesia, tempe bongkrek and other coconut-based products are prepared from partly defatted coconut. The raw material for tempe bongkrek is sometimes mixed with the residue obtained from the manufacture of tofu(soybean curd)and allowed to ferment with the mould Rhizopus oligosporus. Under certain conditions,a contaminating bacterium, Burkholderia cocovenans, is able to grow and produce two distinct toxins: colourless bongkrek acid and yellow-coloured toxoflavin Bongkrek food poisoning usually has a latency period of 4-6 hours. Typical symptoms include malaise, abdominal pain, dizziness and extensive sweating The victim becomes fatigued and drowsy and eventually passes into a coma. Death occurs 1-20 hours after the onset of the initial symptoms (Steinkraus, 1996). Because many Banyumas people have died as a result of eating tempe bongkrek, sale of the product is now prohibited 2.3.2 The 'precautionary'principle Once proper scientific data became available, the principle of prohibition began to be largely replaced by food safety regulations, which included process performance criteria, product specifications and specified storage conditions The risk of botulism from blood sausages was minimised by introducing both product specifications and requirements for storage. As mentioned previously, the safety of fugu was improved by giving more attention to the training of chefs and ensuring that toxic organs were properly removed from the fish Despite these advances, another principle, the ' precautionary'principle, is still relevant in some situations, although its application is mainly restricted to certain vulnerable groups of the population, where absolute safety cannot be guaranteed with respect to some foods. For example, senior citizens in the USA areadvisednottoeatthefollowingtypesoffood(seewww.foodsafetygov/-fsg/ sr2. html) Raw fin fish and shellfish, including oysters, clams, mussels and scallops Raw or unpasteurised milk or cheese Soft cheese, such as feta, brie, camembert, blue-veined and Mexican-style Raw or lightly cooked eggs or egg products, including salad dressings, cookie or cake batter, sauces and beverages, such as egg nog(Foods made from commercially pasteurised egg are safe
which occurs in various species of pufferfish. The dish is now prepared only by chefs who have been specially trained and certified by the Japanese government and can be relied upon to free the flesh of the toxic liver, gonads and skin. Despite these precautions, many cases of tetrodotoxin poisoning are reported each year in people consuming fugu (Source: Medical Journal, 12 June, 2001, vol. 2, no. 6). Sale of bongkrek In the Regency of Banyumas and surrounding areas of Central Java, Indonesia, tempe bongkrek and other coconut-based products are prepared from partly defatted coconut. The raw material for tempe bongkrek is sometimes mixed with the residue obtained from the manufacture of tofu (soybean curd) and allowed to ferment with the mould Rhizopus oligosporus. Under certain conditions, a contaminating bacterium, Burkholderia cocovenans, is able to grow and produce two distinct toxins: colourless bongkrek acid and yellow-coloured toxoflavin. Bongkrek food poisoning usually has a latency period of 4–6 hours. Typical symptoms include malaise, abdominal pain, dizziness and extensive sweating. The victim becomes fatigued and drowsy and eventually passes into a coma. Death occurs 1–20 hours after the onset of the initial symptoms (Steinkraus, 1996). Because many Banyumas people have died as a result of eating tempe bongkrek, sale of the product is now prohibited. 2.3.2 The ‘precautionary’ principle Once proper scientific data became available, the principle of prohibition began to be largely replaced by food safety regulations, which included process performance criteria, product specifications and specified storage conditions. The risk of botulism from blood sausages was minimised by introducing both product specifications and requirements for storage. As mentioned previously, the safety of fugu was improved by giving more attention to the training of chefs and ensuring that toxic organs were properly removed from the fish. Despite these advances, another principle, the ‘precautionary’ principle, is still relevant in some situations, although its application is mainly restricted to certain vulnerable groups of the population, where absolute safety cannot be guaranteed with respect to some foods. For example, senior citizens in the USA are advised not to eat the following types of food (see www.foodsafety.gov/~fsg/ sr2.html): • Raw fin fish and shellfish, including oysters, clams, mussels and scallops. • Raw or unpasteurised milk or cheese. • Soft cheese, such as feta, brie, camembert, blue-veined and Mexican-style cheese. • Raw or lightly cooked eggs or egg products, including salad dressings, cookie or cake batter, sauces and beverages, such as egg nog. (Foods made from commercially pasteurised egg are safe.) 10 Microbiological risk assessment in food processing
The evolution of microbiological risk assessment 11 · Raw meat or poultry Raw sprouts(alfalfa, clover and radish) Non-pasteurised or untreated fruit or vegetable juice.(These juices will carry a warning label. The reason for giving such advice to the elderly is that they are more likely to be affected by any harmful bacteria that are present in the above foods. Once illness occurs, older people face the risk of more serious health problems, even death. With increasing age, natural defences, such as the immune system and production of stomach acid, become weaker. Also, underlying conditions, cluding diabetes and kidney disease, as well as some cancer treatments, may increase the risk of an individual succumbing to foodborne illness and suffering rious consequences. Other groups within the population may also show greater susceptibility to foodborne illness. These include pregnant women, neonates and patients immunosuppressive drugs for treatment of diseases such as cancer Ind rheumatoid arthritis. Here, examples of appropriate precautionary advice clude a recommendation to avoid feeding honey to infants below one year of age, because of the risk of botulism(described in detail by Lund and Peck, 000). Also advice is given in several countries to pregnant women to stop eating certain pates and soft cheeses due to the risk of contracting listeriosis(see Fg.2.1) Unfortunately, the warning of vulnerable groups against these particular hazards varies considerably between countries and in some cases is non-existent At the other end of the 'precautionary'scale is the use of it in risk management when there is a lack of proper scientific evidence or possible legal difficulties. A ecent example from the UK was the ban on butchers selling beef-on-the-bone because of the perceived risk of transmitting to humans the agent of bovine spongiform encephalopathy from bone marrow. Although the risk was considered extremely small, sale of the product was nevertheless prohibited by 2.3.3 Establishing process criteria At the start of the twentieth century, it had already been recognised that protection of the public against foodborne hazards required proper control of heat treatments used commercially in food production. Two example are presented here:(i) the performance criteria for destroying spores of Clost botulinum in low-acid, canned foods(Esty and Meyer, 1922)and (ii)the process criteria for Cox. burnetii in milk pasteurisation, as determined by Enright et al. (1957) Setting of process performance criteria for heat treatment of low-acid canned foods he first mathematical evaluation of the heat sterilisation process for canned foods was made by Bigelow et al.(1920)and later developed by Ball(1923)to
• Raw meat or poultry. • Raw sprouts (alfalfa, clover and radish). • Non-pasteurised or untreated fruit or vegetable juice. (These juices will carry a warning label.) The reason for giving such advice to the elderly is that they are more likely to be affected by any harmful bacteria that are present in the above foods. Once illness occurs, older people face the risk of more serious health problems, even death. With increasing age, natural defences, such as the immune system and production of stomach acid, become weaker. Also, underlying conditions, including diabetes and kidney disease, as well as some cancer treatments, may increase the risk of an individual succumbing to foodborne illness and suffering serious consequences. Other groups within the population may also show greater susceptibility to foodborne illness. These include pregnant women, neonates and patients given immunosuppressive drugs for treatment of diseases such as cancer and rheumatoid arthritis. Here, examples of appropriate precautionary advice include a recommendation to avoid feeding honey to infants below one year of age, because of the risk of botulism (described in detail by Lund and Peck, 2000). Also advice is given in several countries to pregnant women to stop eating certain pates and soft cheeses due to the risk of contracting listeriosis (see Fig. 2.1). Unfortunately, the warning of vulnerable groups against these particular hazards varies considerably between countries and in some cases is non-existent. At the other end of the ‘precautionary’ scale is the use of it in risk management when there is a lack of proper scientific evidence or possible legal difficulties. A recent example from the UK was the ban on butchers selling beef-on-the-bone, because of the perceived risk of transmitting to humans the agent of bovine spongiform encephalopathy from bone marrow. Although the risk was considered extremely small, sale of the product was nevertheless prohibited by law. 2.3.3 Establishing process criteria At the start of the twentieth century, it had already been recognised that protection of the public against foodborne hazards required proper control of heat treatments used commercially in food production. Two example are presented here: (i) the performance criteria for destroying spores of Clost. botulinum in low-acid, canned foods (Esty and Meyer, 1922) and (ii) the process criteria for Cox. burnetii in milk pasteurisation, as determined by Enright et al. (1957). Setting of process performance criteria for heat treatment of low-acid canned foods The first mathematical evaluation of the heat sterilisation process for canned foods was made by Bigelow et al. (1920) and later developed by Ball (1923) to The evolution of microbiological risk assessment 11