It’s a conundrum many consumers face, and often complain about – odours that linger on stain-free, clean looking clothes. But now, Procter & Gamble has announced a presentation of new methods for exploring why this laundry mystery even exists.
The presentation explained sensory and analytical methods suggesting that, when a detergent ineffectively cleans body soils from clothing, it can cause something called odour ‘rebloom’. These findings, shared by P&G senior scientist Kelly Van Haren at the 2018 Society of Sensory Professionals Conference in Cleveland, Ohio, US, are said to be particularly important in the context of ongoing P&G research suggesting that wearing smelly clothing can negatively impact cognition, mood, performance and creativity.
“We’ve learned from global surveys that removal of odours is nearly as important to consumers as stain removal and maintaining fabrics’ brightness,” says Van Haren.
“So, it’s particularly frustrating for the nearly 50% of people who say their clothes look clean, but still smell bad. To delve deeper into this, we created a new method that relies on complex analytical equipment for highly sensitive findings, but also considers how most people detect odours on clothes – by sniffing them.”
Testing phase
To measure odour reduction on clothing, scientists at the laundry detergent company, Tide, used artificial body soils (ABS) dissolved in a solution which were then applied via pipette to swatches of fabric. Then, they used the swatches to identify two primary means of eliminating odour: firstly, cleaning the fabric to remove or break down the ABS odour compounds, and secondly, how perfume or other ingredients prevent or limit the ability to perceive odour.
Of the 15 detergents studied, a third of them did not clean fabric swatches of odour-causing soils any better than water alone
A total of 15 different laundry detergents were blind-tested, and then measured by analytical and sensory assessments one day later. Sensory assessment involved a panel of sensory olfaction experts that compared blind-coded fabric swatches washed with the detergents, to swatches washed in water only. Analytical assessment was conducted via gas chromatography / mass spectrometry equipment and was also blinded.
“Of the 15 detergents studied, a third of them did not clean fabric swatches of odour-causing soils any better than water alone, based on the analytical assessment. However, our sensory panels were unable to detect substantial differences in odours a day after washing with these detergents; meaning that perfumes in laundry detergents may be temporarily masking the smell of soils that were not cleaned from the fabric,” says Van Haren.
“70% of the soils on clothing are produced from our own bodies and are largely invisible to the human eye. When these invisible soils aren’t being removed by some laundry detergents, it may explain why clothing that appears and smells fresh out of the wash seems to pick up odours just from sitting in a drawer or shortly after putting on the garments.”
Odour and mentality
P&G is also involved in ongoing research to determine if the cleanliness and smell of clothing affects mood, behaviour and even the way we think.
“Our research has previously demonstrated an association between mood and the cleanliness of clothing,” says Mary Begovic Johnson, P&G Fabric Care principal scientist. “Preliminary results from new and ongoing research even suggests that wearing clean clothes may offer a variety of cognitive advantages—such as improving creativity.”
Final results of P&G’s ongoing research will be presented at future scientific meetings, and the impact of other clothing cleaning trends and challenges will be explored in future research. One such focus is on higher-capacity laundry machines, which have contributed to a 40% increase in the average load-size of laundry in the last five years and led to under-dosing of laundry detergents. Because these machines tend to use colder water, they can also be less efficient at removing body soils, especially greasy ones. P&G is also examining how this affects synthetic fabrics – which account for 64% of global fibre consumption – because these fabrics attract more greasy body soils and are therefore harder to clean.
