Hygiene in the Kitchen

How can a kitchen or food factory ensure they are reducing the opportunity for microbial growth?

Cleaning is the process of removing dirt, grease and grime from a surface. Cleaning must be performed on hands, fruits and vegetables, food contact surfaces and non-food contact surfaces.

One of the best ways to prevent food contamination is hand-washing. The WHO recommends hand-washing to prevent disease. To wash your hands properly rub with soap for 20 seconds, rinse, dry with a clean paper towel and then rub with sanitiser and allow the sanitiser to dry (see http://www.who.int /gpsc/5may/How_To_HandWash_Poster.pdf). Hand washing should be performed whenever changing tasks, such as after going to the toilet, after handling rubbish or dirty utensils, after coughing, sneezing, nose-blowing, smoking, eating or drinking, after handling money, when switching between raw and ready-to-eat food and before putting on gloves.

Fruit and vegetables should be cleaned before use with a vegetable wash, or disinfectant such as chlorinated or ozonated water.

A detergent is a chemical that removes residue and grease from a surface, but it does not usually disinfect (kill microbes). A disinfectant chemical is a chemical that can kill most micro-organisms on surfaces, including pathogens (although it may not be able to kill viruses or bacterial and fungal spores). A detergent-disinfectant has the ability to both clean and disinfect. For the food industry, cleaning chemicals must comply with the SANS 1828 requirements, and detergents or detergent- disinfectants with the SANS 1853 requirements.

Food contact surfaces (such as utensils, mixers, containers, chopping boards, work surfaces and production belts) and hand contact surfaces (such as handles of cupboards, freezers, refrigerators, utensils as well as taps and switches) need both cleaning and disinfection. Cleaning materials and equipment also need to be carefully cleaned and disinfected to avoid becoming a source of cross-contamination, use of disposable cloths and paper towels are recommended. It is always necessary to clean before disinfecting, as particles and grease provide areas where microbes can be protected from the disinfectant which is meant to kill them. In order to disinfect, chemicals, steam and hot water (above 82°C) can be used.

After preparing a food, and before preparing the next product, equipment such as cutting boards, utensils, dishes and countertops must be cleaned. To clean, first pre-clean by scraping off large amounts of food and grease particles. Then use detergent to take all the rest of the dirt and grease into the water. Rinse with clean water, disinfect with a chemical disinfectant, then rinse so no disinfectant remains. Or disinfect by submerging a rack of items into hot water (at least 82°C) for 30 seconds. Then air dry and cover the item so it is safe from being contaminated before the next use.

Segregation. The principle of segregation, or separating things from one another, is used to manage a number of risks, including that of physical, chemical and allergen contamination. Segregation is also used to reduce microbiological risks to a product. Separating foods to reduce microbial risk will also apply to storage: raw vegetables should be stored apart from raw meat. It is best to store raw and cooked foods separately in a refrigerator, storing cooked foods above raw foods, so that raw food cannot accidentally fall into and contaminate cooked food. In addition cooked food should not be returned to containers which housed raw food, unless the container was thoroughly cleaned. This is meant to prevent microbial contamination of, for example, cooked chicken by raw chicken. Similarly, a food production environment should be set up in such a way that there is minimal chance for raw materials, work in progress, final product and waste to cross paths, thereby again reducing the opportunity for transfer of microbes between items. One example of this is to use different, colour coded, cutting boards for different foods such as fish, poultry, raw meat, raw vegetables and cooked foods. Therefore separating food prevents transfer of microbes from one food to another, keeping cleaned and/or cooked foods from being exposed to microbes again. Thus, reducing risk of spoilage, and harm to consumers.

Time & Temperature control. Temperature can control microbes in two ways: chilling can slow their growth, and cooking can kill them outright. It is important to keep food cooler or warmer than the temperatures that pathogens (dangerous microbes) grow the fastest, which is from 4°C to 65°C. Therefore, ensure that as soon as foods are received that frozen foods are put in the freezer (below -12°C) and chilled foods are refrigerated (below 4°C). Food must only be defrosted in the refrigerator or under cold running water, and food defrosted with water must be cooked immediately. Similarly always marinate food in a refrigerator. It is important to remember that once a food that was frozen or chilled warms up again, the microbes will grow as fast as ever.

Microbes can be killed by cooking, when food is cooked to the correct internal temperature (the temperature in the very middle of the food, e.g. middle of a chicken breast), or higher. This is because lower temperatures will not be enough to kill microbes. An internal temperature of more than 80°C for more than 10 minutes is generally sufficient, as it will kill Salmonella species, Listeria monocytogenes, Staphylococcus aureus, Enterobacteriaceae, Escherichia coli and Clostridium perfringens (excluding C. perfringens spores). The guidelines above are, however, not appropriate for hermetically sealed foods (e.g. canned products) as they do not reduce the risk of spore-forming bacteria such as Clostridium. For microwave cooking it is important to ensure that cooking is done evenly with no cool areas where microbes could survive.

Cooked foods must be stored in such a way that new microbes will not contaminate it, and that those that were not killed do not have the chance to grow further. The South African regulation R962 of 2012 require hot foods to be held at 65°C or higher temperatures. If a cooked food is to be chilled, it must be cooled to 70°C, but not below 65°C, before storing in a holding fridge.

When kitchens and factories apply cleaning, segregation and temperature control appropriately, it will substantially reduce the risk of microbial problems in the final product.

Article by: Gillian de Villiers