124 DEODORANTS
Odour absorption from activated zinc ricinoleate
n Dr Yana Bykov, Dr Swetlana Vogt, Martina Spiegel, Dr Maximilian Franke, Dr Martin Husmann - Schill+Seilacher, Germany
Smell is one of the five most important senses (sight, hearing, touch and taste), allowing us to perceive life in its entirety. The perception of smell is a very complex process including the excitation of specialised receptors located in the human nasal cavity, and signal transmission to the brain. Smells are caused by volatile chemical compounds, which can often be recognised even when present in low concentrations.
Odour plays an important role in our lives. It evokes emotions and memories, changes cognitive and physical abilities, and of course affects relationships between people. For this reason, the problem of odours has been preoccupying scientists and industrial developers for many years. We have to consider the subjective
perception when talking about pleasant and unpleasant odours. Acceptance of unpleasant odours can be determined by averaging the opinion of the population. The main source of malodours are sulfur and nitrogen containing molecules, such as allicin – garlic, felinine - cat urine, hydrogen
O ) 7 Figure 1: Chemical formula of zinc ricinoleate.
sulfide - rotten eggs, ammonia – urine, indole and skatole – fecal, cadaverine and putrescine – rotting flesh, nicotine – tobacco and so on. In addition, there are other odorous substances that are responsible, for example for smell of sweat - isovaleric acid, rancid oil - butanoic acid, tobacco smoke - acetaldehyde etc. In everyday life the number of unpleasant odours originated from non-sulfur and non- nitrogen containing molecules is very limited.
The most common solution to ‘change’ unpleasant odours is the use of fragrances. Such mixtures release a pleasant scent and are able to cover unpleasant odours. This masking is not always effective and after
dispersing the fragrance, unpleasant odour molecules will be predominant in the atmosphere again.
Odour absorbers
Another strategy to fight against bad odours is the development of odour absorbers. A lot of effort and scientific work has been done and this trend is still growing. Odour absorbers are substances that entrap odour-causing molecules and hold them for a long time. The most famous absorbers include activated carbon, zeolites (aluminosilicates), cyclodextrins and zinc ricinoleate. Macro or micro molecular structures of the first three substances resemble cavities, where absorption of odour molecules occurs. This process is in most of these cases not selective. Besides substances with unpleasant odour, also welcoming molecules like perfume components, can be absorbed. An additional difficulty when using activated carbon and zeolites in personal care or household products is their insolubility in water.
Figure 2: Three-dimensional model of zinc ricinoleate molecule. PERSONAL CARE EUROPE
Zinc ricinoleate Zinc ricinoleate has already been established in the area of industrial applications as well as in a wide range of personal care products and household chemicals. Its potential for absorption is based on the ability of divalent zinc atom to form stable complexes of a high degree of coordination with molecules containing electron-donating groups or atoms like nitrogen (N) and sulfur (S). The coordination number usually corresponds to four or six, which means, each zinc ricinoleate molecule can bind up to three suitable
April 2020 OH Zn(O-C-(CH2 -CH=CH-CH2-CH-(CH2 ) 5 -CH3 ) 2
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