Alpha Aromatics, Inc. is a supplier of vapor-phase (in the air) malodor neutralizers: Metazene, Meelium (topical surface active): ZRX, 4-O-Dor, Duo-2-0 and Olar. These extremely effective, complex organic compounds have been successfully incorporated into home care products (including laundry detergents, dry sheets, all-purpose and surface cleaners and carpet shampoos) and air freshening deodorizers, and have many other industrial applications such as wastewater treatment plants, landfills and composting, and food processing.
During this time, many other chemical deodorants have been developed. Some topicals (surface contact) have been formulated into commercial products and others, often less effective, have remained laboratory curiosities. Many occur naturally, are produced synthetically or are blended. Some have been patented, although this is no guarantee of commercial success.
All industrial and consumer malodors exist as gases or mists. They vary in intensity. One of the most intense is ethyl mercaptan. It has skunk-like odor, and as little as 0.000000000002 gram can be detected. Hydrogen sulfide has a sulfur-like, rotten egg-type odor is a poisonous gas more frequently encountered. As little as 0.025 ppm can be detected. Since normal air circulation quickly distributes these and other gases throughout enclosures, deodorizing aerosol mists will not reach the entire contaminated space. As a result, odor depletion is often just 60-80%. However, in time, sprayed particles are more widely distributed, and those that fall on surfaces contact and deactivate malodors. Sprays with smaller particles remain airborne for much longer periods, thus they are perceived more effective.
Other dispensing methods include gels, solids, wicks, wax melts, candles, thermal devices and atomization. There are even heated kitchen containers with deodorizing solutions or applying these solutions on surfaces, as well as mechanical fogging, sprayers, atomizers and outdoor dry vaporizing equipment. All have limitations that prevent or deter malodors and deodorizing molecules from contacting each other. Lastly, some deodorant molecules “lock onto” malodors less firmly than others. Those that form relatively loose bonds may allow some malodors to escape.
The simplest way to destroy volatile malodors is incineration. In a fire, H2S is transformed to sulfur dioxide and water. Ethyl amines are converted to nitrogen dioxide, carbon dioxide and water. This occurs in candle flames, furnaces, fireplaces, bread toasters and other heated cooking devices. Household furnaces provide the primary route for reducing malodors.
Direct ionic chemical reactions are also of interest. To significantly deodorize hydrocarbon solvents, one can add a “sodium plumbate” solution. All the malodorous sulfur-bearing contaminants almost immediately react, forming insoluble black powders, due to the great affinity of sulfur for lead. However, other contaminants, such as unsaturated and amine compounds, are unaffected. The addition of mercury salts has a similar effect of sulfur compounds.
Many consumer deodorizers contain zinc ions. As with lead and mercury, zinc reacts with sulfur compounds, forming white zinc sulfide. Tiny amounts of white sulfide on floors and furnishing are far less noticeable than black deposits, which explains why zinc is selected. Foul smelling unsaturated hydrocarbons, like propylene, must be removed from aerosol propellants. Two methods are utilized. In one, hydrogen is added, destroying the insidious double bond. In the other, natural zeolites are used to preferentially absorb unsaturated compounds.
The raw hydrocarbon liquid is trickled through beds of MolSeive 13X and MolSeive 4 (zeolites) Molecular Seives. For example, the MolSeive 13X polymeric molecule contains “holes” lined with positively-charged atoms. They attract the negatively charged portions of butane-based unsaturated compounds, such as isobutylene, removing them from the mixture. MolSeive 13X can absorb about 31% of its weight in unsaturated compounds. It can be recovered by heating to about 350°F, which causes the absorbed unsaturated compounds to disengage and float away. Some zeolite structures are created synthetically but natural products are preferred.
Natural and synthetic deodorants perform similar functions. Instead of “holes,” many attract sulfur and nitrogen malodorants by presenting positively charged carbon atoms. For example, mercaptans readily add to alpha beta unsaturated ketones at room temperatures. Itaconate salts are useful deodorants—especially if one of the ions is zinc.
A lesser-known mechanism exists where the deodorant molecule can be polymerized, presumably after contacting a malodor. The offending substance becomes enclosed and neutralized. For example, monomers can easily polymerize, producing transparent structures. Polyitaconates may form.
Natural vs. Synthetic
Many deodorants are described as “100% natural,” while others are made by chemically-modifying natural molecules. Metazene odor neutralizer additive can be considered as a union of two naturally-occurring components found in the Oil of Roman Chamomile, coconuts and other components.
Since odor neutralizers are active organic chemicals, they are generally biodegradable by natural forces. Natural components such as hydroxyl free radicals, oxygen free radicals, water and ultraviolet radiation can break down deodorant, ultimately producing carbon dioxide and water molecules. An exception is polymerization, which forms inert macromolecular substances.
Natural essential oils used in fragrance creations have malodor masking qualities and even effective deodorizing action, while delivering a pleasant scent. Acid-base reactions can be important in the reduction or eliminating of malodors. Lime easily produced from natural limestone deposits is chemically calcium hydroxide calcium sulfide. It can quickly react with hydrogen sulfide to produce odorless calcium sulfide. Historically, lime pits are used to minimize the fetid odor of human or animal remains.
Oxidizers and Bactericides
Ozone and ultraviolet, although found in nature, can be electronically produced for certain types of odor removal. Halogens such as fluorine, chlorine, bromine, iodine and astatine can eliminate malodors by contact; however, safety precautions are required. Quaternary ammonium compounds and synthesized phenolic(s) have been used to eliminate odor-causing bacteria.
Ironically, US Patent No. 7,147,822 describes air fresheners containing citric acid which reacts with ammonia and volatile amine odors, cancelling them by producing salts, such as ammonium dihydrogen citrate, which is odorless. Similarly, it purports to spray potassium carbonate solutions to react with hydrogen sulfide (H2S), forming potassium sulfide, which is almost odorless. Finally, an aerosol containing about 10% of a strong (5%) sodium hypoclorite solution is proposed for chemically oxidizing hydrogen sulfide malodors into odorless sodium sulfite. The patent is quite voluminous (16 pages) and is without merit, since the proposed formulations would corrode and explode aerosol containers.
Most US deodorant patents describe complex, synthetic organic compounds which vaguely claim to possess deodorizing properties. As a rule, they do not describe sensory or gas chromatographic experimental results. No data is given on the possible deleterious effect of the odor counteractant on fragrance ingredients.
Most of the deodorizers in use are synthesized and therefore not natural in the strict sense of that term. They typically originate from naturally-occurring organic molecules, like soybean oil or glyceryl trilaurate, which are modified and often chemically united with other organic structure. They often contain “an electron sink” due to a scarcity of electrons, thus developing an electro-positive aura. As such, the structure attracts the negatively charged (electron rich) sulfur and nitrogen elements in many malodors. This feature exists in such synthetic deodorizers as itaconic ester, methylmethacrylate esters and certain unsaturated ketones.
Natural enzymes and microbe biological digesters claim to physically eliminate odors by digestion. Here are some selected alpha odor control additives.
Alpha ZRX: The ricinoleate unit is found in castor oil, ergot and other substances. It is about 90% of the glyceryl triglyceride content of castor oil. Chemically, it is zinc 12-hydroxyoleate. The zinc provides astringency and inactivates malodors like hydrogen sulfide by precipitating zinc sulfide. Additionally, the ricinoleate chain binds electron-rich sulfur and nitrogen atoms, thus deactivating mercaptans, disulfides, amines and related malodors. In aerosols it is used at about 0.25%.
Alpha 4-O-Dor N-Soya-N-Ethyl Morpholinium Ethosulfate: Derived from soybeans, this solution has at least a 70-year history. It was patented and is still used in the formula of “Lysol-type” disinfectant/deodorant aerosols. In hydro-alcoholic formulation it is typically used at about 0.15%. These two products are most often used in surface-active odor control. If the highly unsaturated C18 soya moiety is replaced with oleic (also C18) the deodorizing ability is lost. So the natural component, possibly linoleic or linolenic chains, appear to contain the active site(s) needed for odor control.
Alpha Olar: This methyl undecylenate is a terminal double-bonded linear ester and is a 100% bio-based range of vegetable and (renewable origin) castor oil with anti-odor properties.
Plant-Based Essential Oils
A number of natural deodorants, many in the fragrance field, have shown an ability to mitigate malodors. Examples include:
Clove and Cinnamon Leaf Oils: These volatile oils can typically contain 82-87% eugenol, about 10% acetyl eugenol and minor ingredients. They could be regarded as a substituted phenol derivative. They claim to reduce mercaptans and sulfide malodors and may reduce amine malodors, judging from the molecular structure, but no amine claims are made. They are soluble in many organic solvents. For aerosol air fresheners no commercial examples are known. They can be skin irritants.
Citrus oils are said to control protein degradation odors. Such decompositions are a factor in producing sulfur-based body odors.
d’Limonene: It has low volatility (b. 176°C) and is obtained from citrus fruits. Unfortunately, it is a skin irritant and sensitizer. Its low cost and citrusy odor have made it attractive for some products, but it is not known as an aerosol-deodorizing ingredient.
Oil of Lemongrass: Another natural product, it is derived from lemons, which typically contains about 75% to 85% citral (neral), plus small amounts of geraniol, limonene methyl heptane and dipentene, which have a strong citrus or pine-like odor. Unfortunately, it can have a dark color or off-odor. Judging from its structure, OHC-C=C(CH3)-CH2-C=(CH3)2, it could have deodorizing quality.
Orange Oil: It is related to natural citrus products and typically contains about 92% d’limonene, with citral, decyl aldehyde, linalool, terpenes and other compounds. It may have mild deodorizing abilities, from the structure, but is not added to air fresheners except for fragrance (masking) reasons.
Lemon Oil: This natural volatile oil is claimed to control amine odor, such as those in diaper pails and decaying fish. It contains about 90% d’Limonene, 5% of various aldehydes, like citral, along with geraniol, dipentene and terpenes. As mentioned above, most ingredients contain the active -C= site, able to form electro-affinity bonds with negatively oriented nitrogen and sulfur atoms. If used at about 1.5% in an air freshener formulation, the lemon fragrance would dominate any added fragrance ingredients, making it impossible to create a line of air fresheners, each with a distinctive redolence. Virtually every aerosol air freshener today is marketed as part of a line of four to six products, of which two or three fragrances are replaced annually.
Lime Oil: This a natural product is often produced via vacuum distillation of certain Mexican lime peels. The oil contains linalool, geraniol, methyl heptanone and minor ingredients. The major constituent of linalool is, chemically, 3,7-dimethyk-1-octadien-3-al, and structurally (CH3)2C=CH-CH2-CH2-C(CH3)(OH)-CH=CH2. Lime oil is claimed to control some type of chemical odors.
Oil of Wintergreen: Originally from the leaves of the teaberry wintergreen (pine) tree, the oil is now produced synthetically as the principal ingredient, sometimes identified as methyl 2-hydroxy-benzoate. The molecular structure can be shown as: OH-C6H4-CO2CH3. The oil has a strong medicinal (minty) characteristic odor similar to BenGay. It has been claimed to reduce the odors of mold (mildew) and smoke.
Microbial and empyreumatic odors are complex and not popular targets for air deodorants. No obvious odor-cancelling mechanism is available. It is, therefore, possible that the strong odor of wintergreen covers up these other odors if only temporarily. The odor of wintergreen would predominate over those of any added fragrance ingredients, thus limiting any aerosol line to a single wintergreen scented formula, plus companion products where wintergreen is absent.
Cedar Oil: Oil of Cedar is a complex natural mixture of cedrene (a tricyclic sesquiterpene) with cedral (cedrene camphor and minor ingredients.) The cedrene molecule contains a CH3(CH2)C-C unit that can theoretically remove some sulfur and nitrogen-based malodors. In fact, a claim is made for the elimination of sulfur-type malodors. The mild odor has been related to that of Siberian Pine (terpene).
Vanilla types occur in nature, but rarely. Synthetics are produced from guaiacol, a distilled resin from the gaiacum tree and from lignin/wood pulp, which is rarely processed today. It can be isolated from certain potato parings. It is far more practical to synthesize it from eugenol. Chemically, it is 3-Methoxy-4 hydroxy-benzal-dehyde. It has a moderately strong, pleasant odor. It is claimed to control sulfur-based malodors, such as those from mercaptans, sulfides and disulfides. Other aldehydes are also claimed to remove malodors, but the mechanism is unclear.
Pine Oil: Claimed to reduce bacterial proliferation, the product distilled from pine needles contains dipentene, pinene, sylvestrene, cadene, bornyl acetate and minor ingredients. Pine oil is utilized in older household cleaners.
It is unlikely that pine oil-based aerosol air fresheners will ameliorate offensive odors. Pine oil may reduce the bacteria and other microbes that proliferate on various surfaces and create malodors. Pine oil is a natural agent which eliminates harmful organisms similar to eucalyptus oil and tea tree oil. With its high levels of phenols and acidic plant chemicals, it can reduce germs and odors.
Spearmint Oil: A natural product from the leaves and tops of Mentha spica and related plants, it contains at least 50-60% carvone: 2-methyl-5(1methylenyl) cyclohexene-1-one. A sidearm contains a CH3 (CH2)-C-C unit. As with certain other compounds described earlier, spearmint odor is quite strong. At about 2.0% it would dominate any companion odors contributed by other fragrances. Depending upon particle size percentage, cost and other factors, an aerosol air freshener of this type could produce a discomfortingly intense spearmint odor. A group of companion products, all based on spearmint as the deodorant, would probably not be successful in the marketplace.
The choice of deodorant concentration in any air spray applications depends upon at least four factors: efficacy, particle size, odor of the deodorant and cost. As a rule, from 0.5% to 3.0% (or more) deodorant will be appropriate. In aerosol applications, decreasing particle size by increasing the percentage of propellant will increase efficacy. Highly odorous deodorants may be unsuitable, or must be used with other, less odorous deodorants to obtain the desired efficacy. With their virtual lack of chemical odor, Metazene and Meelium vapor-phase neutralizing additives provide superior virtually fragrance-free effectiveness in the air via spray, aerosol, atomization, fogging and thermal diffusion.
Pressurized aerosol application considerations include the solubility of the deodorizer in the aerosol solution, and its compatibility with plain or lined aerosol cans. Some may corrode containers and other components, producing oxygen over-pressures, which can react with a trace of exposed iron to produce red colorations. Some may slowly change chemically in the aerosol medium, becoming inert.
Worldwide government regulations must also be considered. Perhaps the most cogent are those by US EPA and the California (CARB), which limit the volatile organic compound (VOC) content. For air fresheners, anhydrous type may contain up to 70% VOCs while those that are water-based may contain only 20% VOCs. Other regulations involve can strength, pressure limits, safety data sheet documents and label claims.
Arnold Zlotnik is the founder, president and CEO of Alpha Aromatics and has 40-plus years in the fragrance and air care industry. Prior to forming Alpha Aromatics, he was the founder and largest shareholder of Aromatech (now Agilex). Alpha supplies fragrances for myriad consumer products including scents for private labels, perfumes, personal and home care, candles and more.
More info: www.alphaaromatics.com