Why it’s not such a good idea as it may first seem…
Recently we have been made aware of some consultants to infant formula producers promoting the idea of switching from using the industry standard 70/30 ethanol/water solutions for sanitising, to using anhydrous (99.99%) ethanol instead.
As reported, the thinking behind this is that doing so would help to reduce the amount of water being introduced into the production environment, so therefore would help in creating as much of a moisture free environment as possible, in order to combat the threat of C.Sakazakii.
At first glance, this may seem like a good idea, combined with the fact that anhydrous ethanol will evaporate faster so leave surfaces dryer quicker, and normally will cost less (on an active-matter basis) than buying a 70/30 solution.
All good points, until we consider the matter of effective sanitation, which surely is more important than all the other points combined.
The facts are that anhydrous ethanol has never been as effective as a 60-80% blend of ethanol and water, for the following reasons –
- In simple terms, ethanol kills bacteria by denaturing their proteins – breaking up their protein structure by disrupting the intramolecular hydrogen bonds, then dehydrating them. If a bacterial cell is exposed to anhydrous ethanol, it will enter the outside cell wall from all directions and coagulate the proteins just immediately inside the cell wall. This has the effect of forming a ring of coagulated protein that no more ethanol can pass through so coagulation of the whole cell does not happen. The result of this is that the cell becomes inactive but is not destroyed, and given the right conditions, will become active again.
- If a 70/30 mix of ethanol and water is used on a bacterial cell, then this more diluted form will also work by coagulating the cells protein but it does so at a slower rate so that it can penetrate the entire way through the cell before coagulation can stop it. Thus, the whole cell is coagulated and destroyed.
- Part of the reason why it can penetrate the whole cell effectively is because a 70/30 ratio of ethanol to water has the highest osmotic pressure of any blend, and this helps in penetrating through the outer cell wall. Higher or lower ratios of ethanol and water will not have the same effect.
- The other part of the reason is because a 70/30 blend has the right balance of volatility in that it stays on the surface long enough to penetrate the bacteria, but not long enough leave surfaces still damp after a reasonable time. Anhydrous ethanol has a higher vapour pressure than a more dilute blend, so may evaporate from the surface before it has had a chance to do much, particularly in environments with high air-movement.
On a practical note, remember that the 30% of the 70/30 blend that is water is not introduced into the processing environment as a “separate component”, and left on the surface after the 70% ethanol has evaporated – it’s not as simple as that! The two components of a blend act as one once blended, so as the product evaporates off the surface, there will always be a proportion of ethanol in the residue to provide bacterial control.
If you are wanting to minimise as much as possible any liquids entering your critical zone, then our advice is to apply the ethanol sanitiser via a wet-wipe format instead of the spray method. This gives a controlled and consistent amount of moisture per application and will introduce less moisture per square metre of surface treated than a spray type application. It also has the bonus benefit of providing physical agitation of the surface and collection of any soil, that you won’t get if you just spray a surface and leave it to evaporate.
If you would like some help to explore the best option for you in your facility, simply fill in the form below and someone from our Solutions team will be straight in touch.
Post by Glen Senior