If you drop your food, it’s less about time spent on the floor and more about the surfaces.
By
Cathy Moir

Source:
The Conversation
11 Nov 2019 - 5:42 PM  UPDATED 18 Nov 2019 - 10:47 AM

There are many rules in food safety lore, some that have a basis in fact, and some that are purely grounded in convenience. But it’s important to look at the evidence to see which category common rules fall under.

1. The 'sniff' test

Often when a food has spoiled, it will smell bad. This leads many to believe "no stench = OK to eat". But this isn't always the case. The microorganisms (bacteria, yeasts and moulds) that spoil food by making it smelly, slimy or mouldy might not give you food poisoning.

Eat well: Is it safe to cut mould off food?
Should you bin it or simply slice off the furry bits? We investigate the best rule of thumb for this common kitchen conundrum.

But pathogenic (disease-causing) bacteria, such as salmonella, campylobacter, E.coli and listeria, which do make people sick, don't always cause obvious changes in food when they grow. Sometimes simply being present at low numbers and then consumed is enough to result in illness.

"Pathogenic bacteria, such as salmonella, campylobacter, E.coli and listeria, which do make people sick, don't always cause obvious changes in food when they grow."

Having said that, this isn't an invitation to consume obviously spoiled food. Spoilage is a good indicator food has been left too long and "bad" microorganisms, including pathogens, may also have grown.

In order to steer clear of nasty bugs in food, observe "use by" dates, refrigerate foods that need to be kept cold (this slows down the microbes), cook foods properly (this kills the microbes) and prevent contact and cross-contamination between ready-to-eat foods such as salads, with raw food such as meat that still needs to be cooked.

The best time to throw your leftovers away
Refrigeration is one of the most important inventions in the history of food.

2. The 'five-second' rule

Whether it's one, three, five seconds or some other number, we've all heard some version of this call when someone has dropped food on the floor. But is it true harmful bacteria need a few seconds to hitch a ride on your dropped slice of pizza?

In one peer-reviewed study, four food types were tested (watermelon, bread, bread and butter, and gummy sweets) with four different surfaces (stainless steel, ceramic tile, wood and carpet) that were contaminated with bacteria. Contact time, food type and surface all significantly affected the amount of contamination that occurred. The study found:

  • time is not necessarily of the essence as microorganisms from one surface can instantaneously contaminate another. But it’s true the longer contact time the more contamination can occur
  • higher moisture foods (such as watermelon) allowed the transfer of more microorganisms compared to the other foods. The gummy sweets, which are likely to have the driest surface, showed the weakest transfer of bacteria from the contact surface

  • the weakest microbial transfer occurred when food was dropped on to carpet compared to stainless steel, and tile in particular. The authors hypothesised bacteria attaches better to carpet as it's more absorbent, meaning it's less likely to transfer to the food.

While it's true dropped food can become contaminated with microorganisms from the floor or environment, the majority of those microorganisms in a normal home are likely to be harmless to human health.

The lesser-known causes of food poisoning that may ruin your dessert
With the weather warming up, beware those cold desserts that have been sitting in the sun.

3. Rare meat

When cooking and reheating meat, there are some simple rules to follow. Whole pieces of meat muscle such as steak, pork and lamb can be cooked on the outside, say barbecued or pan-fried, so they’re still rare on the inside.

Historically, under-cooked pork has been feared due to a parasitic worm, but this has never been seen in Australian pigs.

A meat thermometer could stop your feast being a recipe for disaster
Cook up a storm, not a disaster: Here's how to use the right temperature to avoid food poisoning.

Poultry and all minced, rolled, stuffed, tenderised and similar types of meat (including burgers) need to be cooked right through. This difference relates to where microorganisms are found on the meat.

We know microorganisms live on the surface of raw meat because animals naturally harbour microorganisms. That’s why just cooking the surface of a whole piece of muscle meat is sufficient (excluding poultry), because that will kill any potentially harmful bacteria.

When that meat is minced, rolled, stuffed, mechanically tenderised or turned into patties or sausages, the surface of the meat and what it’s carrying is then mixed through the whole product. It’s also possible for chicken tissue to be colonised by bacteria (which just doesn’t happen with other animal meat types). That’s why these types of meat products need to be cooked through to the centre.

The best way to tell if the meat is cooked is to use a meat thermometer. These can be purchased from homeware and hardware stores. Poultry and minced, rolled, stuffed, tenderised meats need to be cooked right through and to a temperature of 75°C. Insert the thermometer into the thickest part of the meat. If you don’t have a thermometer, check the juices run clear and not pink.

This article is republished from The Conversation under a Creative Commons license. Read the original articleCathy Moir is a senior food microbiologist and food safety and stability group leader at CSIRO. She is also affiliated with the Food Safety Information Council, a consumer-focused health promotion charity.

Food with caution
Can tea towels cause food poisoning?
Should you be worried about drying up?
How to avoid food poisoning at summer picnics
There's some really easy things you can do to make sure those al fresco eats don't make you sick.
Is it safe to put canned food in the fridge?
We've all done it. Opened a can of food, and, rather than storing or disposing of whatever is left, just put the can straight into the fridge. But is this dangerous?
You can thaw and refreeze meat: food safety myths busted
This time of year, most fridges are stocked up with food and drinks to share with family and friends. Let’s not make ourselves and our guests sick by getting things wrong when preparing and serving food.
Is double-dipping a food safety problem or just a nasty habit?
Seinfeld, Typhoid Mary and bad manners: scientists tackle the question of double-dipping.