Don’t throw the towel in on finished work odours

Customer expectations of cabinet roller towels (CRTs) are usually based on the assumption that a freshly laundered towel is sterile from end to end and the fact that each new user gets a clean bit as it is unwound from the roll means that the freshly exposed towel is free from bacteria and viruses, as well as soiling and staining. This rosy perception is clouded a little if the towel displays visible staining and even more if the user gets a whiff of horrible odours or experiences a greasy sensation from unremoved oils and fats.

Fifteen years ago, users’ suspicions that CRTs were not as clean and bugfree as they supposed might have been entirely justified. Measurements by Laundry Technology Centre sometimes revealed high levels of residual soiling and staining, unacceptably high bug counts and the occasional revolting stench. All this has now changed, and market leaders are delivering cabinet towels with residual bug counts that would satisfy a hospital, virtually stain-free and smelling consistently as sweet as a rose! This has enabled the CRT market to stabilise and clear the way for expansion, despite the large share of washroom hand-drying still being taken by paper towels and hot air blowers; and the recent pandemic has placed the spotlight back on CRT hygiene.

This major quality improvement was not just down to careful laundering. Research work by leading chemical suppliers played a significant role, along with some engineering innovations from equipment manufacturers. Much of the research is still under wraps, but this month we examine the ways in which the leaders are addressing the market-.place.

What causes odours?

There four major areas of odour generation:

• excrement from bugs that breed on unremoved soiling,
• particulates that get up the nose,
• residual oils, fats, greases or
• wash chemicals.

Removing each of these, to a satisfactorily low-level, calls for some imaginative wash chemistry that relies on a multi-component mixture, each part of which targets a different type of soiling.

Particulates

Examples of particulates that can give rise to complaint if not removed include:

• carbon particles found in soot or dirty grease from firefighters’, engineers’ or industrial oven-cleaners’ hands,
• flour and other food ingredients from workers in food processing and food preparation and
• dust from powder manufacturers and floor dirt from cleaning operatives, for example.

Particulates are removed using mechanical action and a good suspending agent in the main-wash detergent. This ‘wraps around’ each particle of food or whatever, helping to lift it off the textile and (equally importantly) keeping it suspended in the wash liquor until it can be flushed to drain.

Protein particles need softening in a well-designed, cool pre-wash to avoid setting of the protein (which could lock this onto the fibres of the yarns and prevent removal).

Bacteria

Any residues of organic matter (from foods, drinks, human or animal body fluids and so on) are liable to give rise to bacterial growth. It is the excrement from breeding bacteria which generates the wide range of odours which these give off. These might be acidic, which smell sharp and pungent. Others could be alkaline and tend to smell dank, like an open sewer. Human vomit gives off the sharp and readily recognisable smell of butyric acid. Stale perspiration can give an equally sharp and characteristic acidic odour and contains protein which must be softened in the pre-wash before it becomes set and irremovable in the main wash.

Bacteria are an ever-present feature of the environment in which we live. The key to preventing bacterial odours on clean towels in storage is to remove every trace of organic material, and to dry the towel thoroughly, so that there is nothing for the bacteria to feed on. This should be quite adequate to yield clean towels which smell just as sweet days or weeks later (in the customer’s store cupboard) as they do when they leave the laundry.

Residual oils and fats and tarry residues

The critical component in the wash chemistry for removing oils is usually the emulsifying agent. This has amphoteric molecules which make it soluble in both water and oils. It is this which takes the oil, fat or grease into solution in the wash liquor and so to drain. However, each type of oil requires a slightly different type of emulsifier: essential oils found on spa products need an emulsifier with a relatively low HLB (hydrophilic-lipophilic balance) value, around 7 – 8. Food oils and fats tend to need a higher HLB value, into the range 9 – 13, whilst mineral oils and greases may need a value as high as 15 or 16. A launderer who wishes to remove the entire range of possible oils, fats and greases may require a broad range emulsifier, which probably involves a mixture of ingredients and carries a premium price. However, very little of the correct emulsifier is needed to do the job, so price is not that critical in this instance.

Fish and chips!

Peracetic acid is finding a wide range of uses in most types of washing equipment, for de-colouring vegetable dye stains, killing bacteria and neutralising residual alkalinity on the clean textiles. Occasionally, incorrect dosage or removal of peracetic acid can leave the textile with an odour of acetic acid, which is the naturally occurring chemical that gives vinegar its characteristic smell. This can lead to the user of the towel instantly jumping to the wrong conclusion: that the last user had been eating fish and chips and the launderer has failed to remove the last traces of this! In actual fact, the launderer has probably removed all the soiling, taken out every stain and dealt effectively with any bacteria if they have been using peracetic acid in a well-designed process! They have just used a bit too much at some stage!

The other major risk in a cabinet towel process is residual alkali from the detergent. If the launderer opts for a high alkali process to maximise protein removal, then this must be completely rinsed off before drying. Failure to do this properly results in alkali yellowing of the drying fabric (‘galling’), which requires re-washing to rectify. Some processes use peracetic acid in the final bath to be certain of neutralisation of the last traces of alkali.

Cabinet roller towel processes

Modern continuous cabinet roller towel machines generally have six main stages:

• a pre-wash with a little detergent added to assist wetting out. This must be as cool as possible (below 40C) and as long as possible (above 4 minutes) to ensure softening of any protein contamination from human body fluids or foodstuffs. Residence time can be maximised by encouraging the continuous textile to concertina into a ‘J-Box’ or similar arrangement. Some machines operate with a high temperature J-box and rely on high alkalinity to chemically ‘burn’ any protein off the yarns. The emulsifier can be added at the pre-wash stage – it starts to function straight away and is carried forward with the textile.
• a main wash, usually at high temperature, although leading chemists are seeking lower temperature alternatives.
• a rinse zone for removal or neutralisation of the wash chemistry.
• a de-watering stage, to prepare the textile for economic drying by maximum mechanical removal of water.
• a drying zone, to bring the residual moisture in the textile down to around 2%, to minimise risk of mildew and odour formation in storage.
• A wind-up mechanism to produce a neat roll with square sides to give a neat fit into its cabinet for daily use.

Most continuous CRT machines make a good job of winding up the washed and dried towel but the performance of the other five stages varies widely depending on the design, the chemistry used and the in-house maintenance. The comments made on each of the first five stages are intended to aid troubleshooting, by highlighting the key points to monitor and correct where necessary.

Monitoring and certification

Bug measurements can be carried out cheaply and simply using a variety of methods. If there are bacteria present, the launderer needs to review the process: the target is to achieve no viable bacteria able to breed in storage. There is no point in proceeding with any attempt at certification until this is reached.

In parallel with ensuring the process is working effectively, the launderer should be discussing with detergent suppliers the requirements for dealing with Covid-19. Leading suppliers now have processes which promise an effective bug-kill, including Covid. The alternative may be to have the towels treated with a permanent finish that manages bacterial and viral growth.

Some laundry customers may accept that the laundry is using a process which meets this requirement if the detergent supplier has independent certification to this effect. Others may demand independent certification that the launderer is using this process correctly (or is using treated towels) and is actually achieving the necessary degree of decontamination. This will require the launderer to seek external help with monitoring and certification, which is now generally available in all parts of the UK and in many other parts of the world.

Conclusions

The market for cabinet roller towels is changing and leading launderers are meeting the challenge. All the problems are soluble, and it is now part of the craft skill of the professional launderer to address these and deliver odour-free, bug-free work which both looks clean and smells fresh.

• If you have problem that you think LTC Worldwide can help with, or that you feel would make a good subject for Material Solutions, please call
  T: 00 44 (0) 816545
  www.ltcworldwide.com