Hey! There’s an invisible bug in my soup, What’s it doing there? -The 6 needs of bacteria

Bacteria or microorganisms are what is termed ubiquitous, meaning that they are literally everywhere! From your cellphone to the kitchen sink and even on (and in) your body- I’d start referring to myself as “we” if I were you.

Food-related microorganisms can be loosely grouped into 3 categories: pathogenic, spoilage and beneficial. Depending on where the microorganisms are, their quantity and the conditions under which they are kept, they can be completely harmless or extremely deadly. Think of it like a venomous snake, in it’s natural habitat far away from civilization the snake is harmless to you and I, but if it gets into your bed- then chances are you’re in a lot of trouble, and, in the same light, the venom from a snake is the key ingredient for the anti-venom used to save the lives of snakebite victims. In the same way, pathogenic bacteria such as Listeria monocytogenes, Salmonella, E.coli or Staphylococcus aureus in the environment probably won’t harm you, but if it gets in our food, it could lead to serious illness or even death. Spoilage organisms like Pseudomonas or Lactobacillus are unlikely to make you sick, but they tend to make your food look, smell & taste bad, while beneficial bacteria can be used to produce products and foods that we consume- e.g penicillin, yoghurt & bread.

Now, with all due respect- bacteria are a lot like us human beings. In that although there are millions, if not billions of bacteria known to man, they all need the following 6 conditions to be met in order to survive and thrive:

1- Food

Just as we humans need nourishment and nutrition in order to gain energy and ultimately, survive so do bacteria. Bacteria use the energy gained from the food on which they live to facilitate metabolic processes which lead to release of enzymes such as α-amylase used in starches, gases such as carbon dioxide released by the yeast in dough to give it the rising effect or toxins such as Listeriolysin O released by the listeria monocytogenes bacterium that causes Listeriosis . Without an adequate food source, bacteria cannot metabolize and therefore cannot survive.

2- Acid

Just as humans require a good pH balance for comfort- bacteria have an optimum pH at which their activity is at its peak. Conditions that are above or below this optimum pH value lead to a reduction in the bacterial activity which ultimately leads to death or inactivity. Foodborne pathogens require a slightly acidic pH level of 4.6-7.5, but they thrive in conditions with a pH of 6.6-7.5 acid/acidified foods with a pH 4.5 or below are generally considered safe.

3- Temperature

Bacteria, just like humans, have an optimum temperature range at which they “live their best lives”- this temperature range is called the danger zone (cue creepy dramatic music), for food-borne pathogens, the danger zone lies between 5- 60°C. To minimize the risk; – always keep hot food hot and cold food cold. -store cold food in the fridge or freezer at 5 degrees or less -Always cook meat thoroughly and invest in a meat thermometer – Store & serve hot foods at 60 °C or higher – When reheating food, always reheat until you can feel the heat at the bottom of the plate and the food is steaming

image source: https://foodsafetymattersyear9.weebly.com/the-danger-zone.html

4- Time

As the saying goes “all good things take time” well, in the world of foodborne pathogens we aren’t the patient type! Organisms such as staphylococcus aureus have an incubation period of 1-6 hours. I mean you could have breakfast in bed at 08:00 and one of those bland hospital pies for lunch- that’s if you’re well enough to eat anything. To avoid the drama, food should be removed from “the danger zone” (cue creepy, dramatic music again) within half an hour to four hours, either by cooling or heating.

image source: https://foodsafetymattersyear9.weebly.com/the-danger-zone.html

5- Oxygen

Almost all food-borne pathogens are aerobic- no, not that kind of aerobics man! Bacteria are not into jumping jacks, cycling and dancing etc!- Aerobic, meaning that they require oxygen to grow or survive. Removal of oxygen by means of vacuum packing or transferring products to an airtight container are some of the ways that we can minimize the suitability of conditions under which these pathogens could grow. Now, remember we said almost all food-borne pathogens need oxygen to survive, but there are a handful of stubborn- die-hard- Bruce Willis type pathogens like Clostridium botulinum which causes botulism & Bacillus cereus that are anaerobic (can survive/ grow without the presence of oxygen), these bad boys are also what are called spore-formers and can survive for very long periods under sub-optimal conditions such as low pH and high temperatures. Generally found in canned foods the best way to avoid these types of pathogens is – never purchase or use cans that are blown, dented or damaged -Wash the top of your cans before opening -Do not use canned products that have passed their EXPIRY date (Just out of interest, do you know the difference between expiry dates & best before date? – comment down below)

6- Moisture

Water is life for you, me, Dupree and even for bacteria. The really cool thing is that in the weird & wonderful world of food microbiology water content/ moisture actually has very little to do with bacterial survival- HUH?! To start of one needs to understand the terminology moisture is the measure of how much water is in a food in total water activity (aw) is a measure of the water that is available for use (by bacteria essentially) and is measured on a scale of 0 to 1.0 So a food may have a high moisture/ water content, all that water may be bound and therefore unavailable for bacteria to use- so it is not necessarily the moisture content that bacteria are after, it’s the water activity! For example, strawberry jam will have a higher moisture content compared to lets say , biltong- however, because the jam has a high concentration of sugar which in essence binds to the water and makes the water “unavailable for bacterial use” the water activity on the jam would be close to that of the biltong because both food products have a limited amount of “free- water”.

Food-borne pathogens grow best in foods that have a water activity between 0.95- 1.0, generally, a water activity of 0.85 and below is considered safe

That’s all folks!

See you in the next post, until then please follow me on Instagram @thefoodtech_SA as well as on the blog thefoodtechcoza.wordpress.com for regular updates.