Food Hygiene & Bacteria

By Sally-Ann Stevens

While most of us generally don't think about it too much - myself included - food hygiene is an important and oft forgotten part of our daily eating routine.

In Australia alone, more than 2 million people are affected by some form of food poisoning, and many of these cases are from foods prepared and eaten at home.

Prevention is the key, and herein we'll look at the three major reasons for food poisoning: temperature, cross contamination and incorrect reheating.

Take something as simple as food storage: You cook a delicious tortellini pasta dish and realise the 800g of pasta you used was a little too much for two people. Simply decant the pasta into some Tupperware and pop it in the fridge.

Well, you'd be surprised how often this doesn't happen, and there are specific danger zones, both temperature and substance-based, where bacteria thrive.

First let's look at cross contamination: Simply put, this could be when you use a chopping board to dice some steak, then use the same unwashed knife and board to cut something else, say half a dozen mushrooms.

While everything seems okay, bacteria will have moved from one food to the other. Essentially the spread of bacteria between food, cross contamination can happen as described above, or even when raw food touches other food, perhaps a bag of chicken thighs will drip oils into leftover tortellini, for instance.

The best way to avoid cross contaminating foods, equipment and surfaces in your kitchen is to a) wash your hands thoroughly after handling raw food, b) keep raw and non-raw foods separate and c) clean surfaces and equipment properly before you prepare food and also again if they've been used with raw food.

The type of foods that are most likely to 'go bad' in a short period of time are meat, fish, poultry and dairy. It's wise to be aware of the condition of these foods, because while they may contaminate other foods in storage, they are home to some nasty bacteria too.

These four food groups already contain deadly bacteria, but in such small amounts that your body can deal with them effectively. But these minute amounts of bacteria can quickly expand, given enough moisture and time to multiply.

Cross contamination of foods and equipment is one thing, but bacteria will flourish if given the right temperature.

Most organisations and health companies agree on the Temperature Danger Zone, including Food Standards Australia New Zealand, an independent statutory authority that ensures all food imported into Australia and New Zealand is properly labelled according to content.

This Temperature Danger Zone is the area where bacteria will thrive, and eating such food could result in food poisoning. Between 5° and 60° almost all foodstuff, and particularly meat, fish, poultry and dairy, will spoil given more than a few hours.

The time needed for something to spoil is also cumulative. For instance, you may leave the milk out for 20 minutes a day, yet the milk is still cool to touch and smells okay. After four or five days of this however, that equals to more than an hour out of the fridge and thus the milk is likely to go bad before its use-by date, a sure sign that the bacteria have multiplied.

Refrigerating food is a good way to keep it fresher, longer. But it should also be noted that even the most high-tech fridge temperatures vary, so it's wise to check with a thermometer which is the best area for specific foods.

Overloaded fridges will also not work as efficiently either, and if goods are packed tightly, the cool air won't circulate properly, reducing the temperature inside.

At the other end of the scale is the hot food, which is a little easier to stomach (excuse the pun). If you cook something and it drops to below 60°, it is very likely to spoil if left for prolonged periods.

Basically, if you've cooked something and want to keep it for leftovers, transfer it as soon as it stops steaming to a sealed container and then pop it in the fridge - keeping either side of the Temperature Danger Zone: 5° to 60°.

Reheating pre-cooked food is also a notoriously common way to get food poisoning, and the only advice here is simple - if you are going to reheat food, do it as quickly as you can and get it as hot as possible, which will kill most potentially dangerous bacteria.

At the end of the day, common sense is always a good guide, but knowing how, why and when bacteria spreads will help you avoid food poisoning.

The Culprits...

Salmonella
There are many different types of Salmonella, most of which have been isolated from a variety of sources, but it was first isolated by Salmon and Smith in 1885 from pigs affected with hog cholera.

Listeria monocytogenes
This next bacteria has been linked with foodborne disease since the early 80s, yet its existence has been documented as far back as the mid-1940s.

Escherichia coli
Also known as E. coli, there are many strains that are harmless and live naturally in the digestive system of humans and animals.

Clostridium botulinum
While very rare, Clostridium botulinum is a very deadly micro organism when ingested. It is sometimes found in canned foods.

Links:
Food Standards Australia New Zealand
Food Safety Information Council