IJsbrand Velzeboer: Underwear jokes and the cold wash

In Amersfoort and the surrounding area there was — and in some places still is — panic. A fecal contamination of the drinking water led to the advice to boil tap water for three minutes to be on the safe side. Meanwhile, a far greater danger is lurking in all those energy-efficient households — one no one is warning us about: washing underwear in cold water. What follows is a slightly unpleasant story, but one with an important message.

The test setup: a washing machine with 10 kg of dry laundry holds around 160 pairs of men’s underpants, which are ‘cleaned’ cold with detergent in three rinse cycles of approximately 20 liters each. Are they clean after that? Forget it! A simple calculation shows that this drum contains around 160 grams of fecal matter, assuming a ‘skid mark’ of 1 g per pair of underpants. The literature tells us that this corresponds to 5.10¹⁰  vegetative bacteria per gram in the washing drum. During washing, this content is roughly diluted three times with 20 liters of clean water each time. In a dilution series, the bacterial count decreases linearly; there is no logarithmic kill rate as with thermal decontamination. In the end, our cold-washed laundry on the drying rack still contains 2.10⁵ bacteria per gram. Perhaps detergents have some bactericidal effect? Say 80%. That still leaves a bacterial count of 4.10⁴ per gram of laundry. Who doesn’t start itching at the thought that a cold-washed pair of underpants weighing 160 grams contains 6,400,000 bacteria?

We know that body fats only become liquid at temperatures above 40 degrees Celsius. So those fats happily stay put, preferably in the rubber seals of the machine, in the form of greasy residue. The detergent industry has come up with a solution for this filth: special cleaning tablets! That’s turning things upside down. I don’t put pedals on my car because the engine doesn’t work properly, do I?

Of course, cold washing workwear for the food industry is completely unacceptable. That should be done at a minimum of 90 degrees Celsius, using chlorine-based detergents, followed by ironing. Only then is this clothing adequately decontaminated and the bacterial count below 100 per 100 cm². If everything is in order, every QA manager will have validated and verified this process. Right? Hmm… Fortunately, I’m not a germaphobe.

IJsbrand Velzeboer
Curative food technologist