MATERIAL SOLUTIONS
Decontamination process development
Effective removal of proteins is critical to allergen decontamination, because most allergens are protein-based, with a wide variety in the proteins concerned. Research has found that a one-wash test piece based on dairy protein, animal blood and carbon black can provide reliable indication of animal protein removal from this soiling. The Swiss EMPA organisation offers a calibrated test swatch based on these ingredients and the power of the wash process with respect to protein removal can be assessed numerically using a standard laundry reflectometer. The effectiveness of this is now backed up by several years research data on multiple sites throughout the UK, which demonstrate its reliability. Bleaching of vegetable dyes, usually by oxidation, complements protein removal, allowing visual checks by the food industry customer. A stain-free appearance is an essential part of assured decontamination. Some oxidising agents also offer a destructive effect on any stray residual molecules of protein.
Removal of vegetable oils is vital, with some unrefined nut oils, which contain the nut protein being particularly important. These, along with any fatty proteins, need suitable emulsifiers, to allow effective reduction using low temperature washing. Animal and human body oils usually need a different emulsifier to that used for dairy and for nut oils, so a wide-range emulsifier is called for. This could be a blend of two or more different emulsifiers to span a range of HLB (hydrophilic-lipophilic balance) values, from perhaps 15 right down to 6 for some nut oils and leading laundry chemical suppliers have achieved this in the last few years. Removal of mineral oils is essential as the HLB of mineral oil is closely matched to some fish as well as some nut oils. Most allergen decontamination processes also provide sufficient power to remove these if the HLB value is appropriate. Control of re-deposition of soiling removed by detergency is critical to allergen
TABLE 1: HLB VALUES FOR TYPICAL ALLERGENS
Allergen Typical HLB value Oily Fish Brazil Nut
Almond Nut Soya
28 LCNi | September 2024
11 8 6 7
ITCHY RASH; An itchy rash is among the mildest of allergenic reactions
decontamination. There is a natural tendency for micelles of emulsified oil and particulate soiling to be attracted back onto the clean fabric before the end of the wash process. This is because the soiling in suspension in the wash liquor tends to acquire an opposite electrical charge to that on the surface of the clean fabric. This creates a strong attraction which results in re-deposited soiling locking onto the cloth surface, where it is very firmly held, causing overall greying. This can be very difficult to reverse in any rewash. Greying assessment can be used to monitor the degree of re-deposition occurring. Re-deposition is countered by including powerful suspending agents in the wash chemistry, which wrap around the suspended soiling (in all of its forms), neutralising the electrical charge. This, together with the physical barrier to re-deposition created by the wraparound effect, reduces to a low safe level any risk of re-deposition of allergens on the clean textiles.
How the garment rental operator is providing justified assurance of adequate allergen removal
Allergens cannot be seen with the naked eye and can even be difficult to recognise under strong magnification. Leading laboratories have developed qualitative and quantitative tests for particular allergens, but these are time-consuming and require specialist equipment and skills. They are not suitable for daily, weekly
or even monthly quality control in the rental laundry, but they are suitable and cost-effective for evaluating different decontamination processes and for annual monitoring and certification of laundry performance.
LTC research has shown that the decontamination performance of a rental laundry can be assessed by measuring the allergen contamination on key surfaces and on a representative sample of decontaminated garments. There is no need to perform these tests for every one of the hundreds of different allergens in foodstuffs. It has been found that if the level of a limited number of key ‘marker’ allergens is below the current detectable limit, then the risk to the consumer has been reduced to an adequately low level and cleansed garments from the plant can be safely used. These detectable limits for some common allergens are shown in Table 2.
In between annual testing and certification, quarterly test have been developed and proven, to ensure that the power of the wash process continues to match or exceed that required. These quarterly monitoring tests are based on calibrated EMPA single-wash test swatches to indicate (numerically) the removal of animal and dairy protein, mineral oil, vegetable oil and vegetable dyes. They also include the use of a 25-wash test swatch for greying, to indicate the level of redeposition of soiling back onto the clean textiles.
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