MICROBIOLOGICAL QUALITY AND SAFETY IN DAIRY INDUSTRY

Module 3. Plant hygiene and sanitation

Lesson 13
CONCEPTS OF HYGIENE AND SANITATION

13.1 Introduction

In history medicine and hygiene have always been counterparts in healing and preventing diseases. However, both disciplines have mostly gone hand in hand in improving human health. After the recognition of germs as causing agent of diseases the significance of hygiene developed rapidly and is now considered as the corner stone of safe food production.

In the mid nineteenth century, two persons lay the foundation of modern hygiene. It was Hungarian physician Semmelweis and the British surgeon Lister. Both introduced hygienic methods which still appear to be essential in modern society. Ignác Fülöp Semmelweis (1818 - 1865) was a Hungarian physician who demonstrated that puerperal fever 1 (also known as "childbed fever") was contagious and that its incidence could be drastically reduced by enforcing appropriate hand-washing behavior by medical care-givers. Since the cadaverous matter could not been removed from hands merely by washing them with soap and water and therefore experiments with different chemicals were started where he recommended the additional use of chlorinated lime resulting in reduction of death rate caused by puerperal fever to zero level.

In 1865, Louis Pasteur suggested that decay in wounds was caused by living organisms in the air, which on entering matter caused it to ferment. He considered that microbes in the air were likely causing the putrefaction and need to be destroyed before they entered the wound. Joseph Lister (1827-1912) made a triumphal tour of the leading surgical centers in Germany in 1875 where he met Robert Koch who demonstrated in 1878 the usefulness of steam for sterilizing surgical instruments and dressings.

Public health concern with food borne diseases emerged around 1880’s. This was after micro-organisms were recovered as infectious agents. Koch and his assistants devised the techniques for culturing bacteria outside the body, and formulated the rules for showing whether or not a bacterium is the cause of a disease. Identification of agents involved in food borne diseases and the etiological research of food-borne diseases began at the end of the 19th century when the work of Van Ermengem served to clarify the etiology of botulism in man (Van Ermengem, 1897). Later milestones in this category included the recognition of Clostridium perfringens as a food-borne pathogen in 1943 (McClane, 1979) and Bacillus cereus in the 1950’s (Kramer and Gilbert, 1989). Human infections with Listeria monocytogenes were well known by the 1940’s and food borne transmission was suspected (Rocourt and Cossart, 1997), but it was not until the occurrence of an outbreak in Canada in 1981 that proper evidence was obtained. Since then, numerous food-borne outbreaks have been reported in different countries, and prevention of listeriosis has become a major challenge for the Food Industry. Around 1980 – 1985 S. enteritidis re-emerged via the internal contamination of chicken eggs. At the same time a new emerging pathogenic started to emerge: Escherichia coli O157: H7 (Willshaw et al., 2000). This organism causes hemorrhagic colitis. In some victims, particularly the very young, may develop the hemolytic uremic syndrome (HUS) which is characterized by renal failure and hemolytic anaemia.

13.2 Hygiene and Food Sanitation

Following the discovery, around 1880, that food can be an important source of disease-causing organisms, investigations started to concentrate on the reservoirs and routes of transmission of pathogens. At the same time, attention began to focus on the presence of pathogenic bacteria in the intestines of animals, as a source of food contamination, and foods of animal origin, as routes of transmission to humans. Savage (1909) observed that faecal contamination of food must be very common and milk, in particular, was suspected to be a vehicle of infection. Theodor Escherich, a German paediatrician, who devoted his efforts to improving childcare, particularly in relation to infant hygiene and nutrition, was the first to make a plea for heat-processing of milk to prevent infant diarrhoea (Escherich, 1890). After that time, the heating processes used for food began to improve. Real progress was made when Esty and Meyer (1922) developed the concept of process-performance criteria for heat treatment of low-acid, canned food-products to reduce the risk of botulism. An outstanding example is the work of Enright et al. (1956, 1957), who established performance criteria for the pasteurization of raw milk that provided an appropriate level of protection (ALOP) against Coxiella burnetii, the causative agent of Q fever. Studies on the agent responsible for tuberculosis had been carried out earlier. Based on the need to improve hygiene in slaughter plants, the USA was one of the first countries to introduce a Meat Inspection Act in 1906. This brought the following reforms to the processing of cattle, sheep, horses, swine and goats destined for human consumption:

• All animals were required to pass an inspection by the US Drug Administration prior to slaughter;
• All carcasses were subject to a post-mortem inspection;
• Standards of cleanliness were established for slaughterhouses and processing plants.

In the UK, it was recognized that legislation alone was not sufficient to protect consumers against food borne diseases, and the health authorities became aware of the need for public education to achieve cleaner food supplies. Food handling practices were very poor. A new Food and Drug Act was introduced in the UK in 1938, and it become necessary to use hygienic conditions and practices in handling, wrapping and delivering food, and adequate hand-washing facilities for food handlers. A clear breakthrough in public health was the processing and disposal of domestic and sewage wastes, in conjunction with the purification of water supplies to ensure that any pathogens present were not passed to consumers via drinking water. Also, sanitary microbiologists were appointed to inspect food-processing and eating establishments to ensure that proper food-handling procedures were followed. These made a significant contribution to the development of appropriate hygiene standards.

13.2.1 Definitions of hygiene

In ancient times, it was clear that diseases could be overcome, either by actively curing (Asclepius) or through the power of cleanliness (Hygeia). The first definitions of ‘hygiene’ are derived from the work of the Goddess Hygeia:

‘Healing through cleanliness’

‘The science dealing with the preservation and promotion of health’

By the beginning of the 20^th century, it had become clear that preventive measures were the only way to produce safe food, and the discipline of food hygiene was born. Current definitions of ‘food hygiene’ are presented in Table 12.1.

Table 13.1 Definitions of food hygiene in current use

13.2.2 Food sanitation

Sanitation is a term for the hygienic disposal or recycling of waste materials, particularly human excrement. In consequence, sanitation is an important public health measure that is essential for the prevention of disease. In the USA, there is a particular focus on the concept of food sanitation, which may be defined as ‘the hygienic practices designed to maintain a clean and wholesome environment for food production, preparation and storage’ (Marriot, 1999). This second definition links hygiene more specifically with maintaining a clean working environment for food processing. Even here, hygiene requirements extend beyond the practice of cleaning itself to incorporate those elements that make effective cleaning possible and allow control of insects and other pests. In the microbiological sense, sanitation is defined as ‘a cleaning and disinfection process that results in a 99 – 99.9 % reduction in the number of vegetative bacteria present’.

13.2.3 Personal hygiene

Personal hygiene is of great importance for the maintenance of health in general. Human beings are natural carriers of many micro-organisms and sources include the hair, skin, mucous membranes, digestive tract, wounds, infections and clothing. Good personal hygiene is primarily directed towards preventing both disease and discomfort. Hand washing, dental care, avoidance of spitting, daily showering, etc, as well as clean living play an important part. Disposal of waste is also important. All these measures are preventive in character and are readily carried out.

13.2.4 Hygienic design of facilities and equipments

Hygienic design of food-production facilities, processing equipment etc. is a most important factor in ensuring that food is safe and wholesome. Poorly designed farms, factories, and equipment can easily result in contamination of food products and lead to food-poisoning incidents. Furthermore, design deficiencies may result in losses of product due to spoilage increased cleaning costs and reduced production time. These aspects are also of possible environmental concern. Therefore, it is essential that both manufacturers and users of food-processing equipment are aware of hygienic design principles and requirements such as those described in EU Directives 98/ 37/ EC and 93/ 43/ EEC, and Hygienic Design DIN EN 1672/ 2 (1997). Hygienic production of food thus depends upon a combination of food-processing procedures and hygienic design of buildings and equipment, in full compliance with legislation.

13.2.5 Hygiene control measures in food processing

Hygiene in food processing started with the introduction of general measures, including cleaning and disinfection, prevention of re-contamination and treatment of food products to kill any microbial pathogens present. Research carried out in the earlier 19th century resulted in predictions relating to many processes, such as heating, acidification, drying and the use of curing agents and its effect on both pathogenic and spoilage organisms. Such knowledge ushered in a new era in safe food production. This era is characterized by the division of hygiene measures into specific practices that are controllable and other general measures.

13.3 GHP Concept

One of the first safety systems developed by the food industry was that involving the application of Good Manufacturing Practices (GMP), as a supplement to end-product testing. GMP covers all aspects of production, from starting materials, premises and equipment to the training of staff and the WHO has established detailed guidelines. GMP also provides a framework for hygienic food production, which is often referred to as Good Hygienic Practice (GHP). The GHP concept is largely subjective and its benefits tend to be qualitative rather than quantitative. It has no direct relationship to the safety status of the product, but its application is considered to be a necessary preventive measure in producing safe food. Those hygiene measures that have a predictable outcome and are subject to control can be incorporated in the Hazard Analysis Critical Control Point (HACCP) concept. This concept seeks, among other things, to avoid reliance on microbiological testing of the end-product as a means of controlling food safety. Such testing may fail to distinguish between safe and unsafe batches of food and is both time-consuming and relatively costly. However, effective application of the HACCP concept depends upon GHP being used. The establishment of GHP is the outcome of long practical experience and major components of the system are

13.3.1 Design of premises and equipment

This includes the location and layout of the premises to avoid hygiene hazards and facilitate safe food production. Food processing and handling equipment should always be designed with hygiene in mind, including ease of cleaning.

13.3.2 Control of the production process

Control measures are applied throughout the supply chain and cover factors such as raw materials, packaging and process water, as well as the product itself. Key aspects include management and supervision of the process as a whole, as well as appropriate recording systems.

13.3.3 Plant maintenance and cleaning

Both processing equipment and the fabric of the building should be maintained in good order. Suitable programmes need to be developed for plant cleaning and disinfection, and their effectiveness monitored routinely. Systems are also needed for pest control and management of waste.

13.3.4 Personal hygiene

Staffs are required to maintain high standards of personal hygiene in relation to wearing of protective clothing, hand washing and general behaviour. Visitors must also be strictly controlled in these respects. The health status of personnel should be monitored regularly and any illness or injuries recorded.

13.3.5 Transportation

Requirements should be established for the use and maintenance of transport vehicles, including their cleaning and disinfection. Vehicle usage should be managed and supervised.

13.3.6 Product information and consumer awareness

It is important that the final product is suitably labeled and that the consumer is provided with all relevant information on product handling and storage, including a ‘use-by’ date. Labelling should also indicate the batch and origin of the product, so that full traceability is possible.

13.3.7 Staff training

In relation to food hygiene and safety, all personnel should receive appropriate training and be made fully aware of their individual responsibilities. Such training should be repeated and updated as required.

13.4 Future Aspects

13.4.1 Further development of hygiene control

From long experience, it has become clear that certain hygiene controls are very effective in reducing food borne disease, and the effects of certain measures, like heating the product, have a predictable outcome. Thus, they have been incorporated eventually in the HACCP system. However, there are still a large number of important measures that contribute to food safety but their effects are neither quantifiable nor properly understood. Examples include the effects of cleaning and disinfection, steps to prevent cross-contamination in food processing and hand washing and other aspects of personal hygiene. On the other hand, micro-organisms may sometimes become established unexpectedly in processing equipment and food-production facilities, thus increasing contamination of the product. In this case, the usual process parameters are controlled, but other, unknown factors are having an effect. Clearly, more information is needed on the factors that affect product safety and those that have little or no effect.

13.4.2 Building hygiene into the system

A new research area that aims to improve general hygiene involves nano-technology. This technology is a promising means of developing processes that are inherently hygienic. For example, coatings based on nano-technology can make the environment more hygienic by preventing bacterial attachment to surfaces (ceilings, floors and walls of processing facilities, conveyor belts etc.) and/ or bacterial proliferation on these surfaces. Coatings have already been developed and successfully applied to prevent fouling of, for example, windows, water-closets and tiles. Thus, modern technology can do much to protect society from pathogenic agents, but this takes no account of one important factor: natural disease-resistance. Without such resistance, human beings will continue to be highly vulnerable and require even-more protection from pathogens.

13.4.3 Changing pattern of microbial hazards

Society is increasingly confronted with microbial problems that are not susceptible to control by traditional measures. This may involve new hazards, including viral contamination of food and the occurrence of bacteria resistant to antibiotics and disinfectants. Many of these problems arise from the introduction of new technologies, new methods of producing raw food-materials and socio-economic changes in society, including overcrowding, increased traveling and global food-production and trade. Food borne disease continues at a high level, despite increasing attention to food hygiene, and with no alternative strategy available. This situation is an important challenge to modern society and requires a degree of foresight that goes well beyond present concepts of hygiene control.