Tai Xiumei

China Research Institute of Daily Chemical Industry, China

Xu Bin, Wu Jiren, Tang Zhuhua, Cheng Yan, Si Zuoxue

Hainan Institute for Food Control, China

Hou Meifang

Shanghai Institute of Technology, China

As an important component of household life, the kitchen plays a vital role in daily life. The kitchen is not only the area with the most greasy dirt in the house, but also the place with the easiest bacterial growth and odor production. It has become very difficult to keep the kitchen clean and beautiful, and avoid bacterial growth and odor development. Researchers have conducted a lot of work on kitchen cleaners.[1～9]The formation of kitchen greasy dirt,cleaning and product usage were discussed in this paper.

Formation of kitchen greasy dirt

Oil stains are expected in the kitchen when there is continuous cooking, especially in China where oil is used quite often. The oil used in cooking will be vaporized,carbonized and condensed into grease in the heating process, which will become brown viscous residual substances with long-term heating and oxidation, then attached or bound to the wall and kitchen appliances.Unsaturated grease in the oil will be transformed into conjugated ethylenic bond under long-term high temperature, and then oxidized and polymerized, forming viscous dirt, such as oxidized oil and polymerized oil.[1]In addition, due to sedimentation and physical absorption effects, small dust particles floating in the air and other particles will attach to the utensils, further increasing the cleaning difficulty.[2]

Cleaning techniques for kitchen greasy dirt

Generally, there are three cleaning techniques for removing kitchen greasy dirt.

1) Cleaning with strong alkali. Alkalis have saponification reaction with animal oil or vegetable oils. Such kind of cleaners is low in raw material price, but strongly corrosive for objects and human skin, so it is rarely used at present.

2) Cleaning with solvents. Organic solvent is used to dissolve greasy dirt according to principle of “Like Dissolves Like”. It is highly efficient in grease removal,but with high toxicity, low flash point, strong pollution and high price, making its development restricted.

3) Cleaning with surfactants. When cleaning, hydrophobic groups of surfactants is bonded to greasy dirt,and one end of the hydrophilic group dives into water,thus reducing the surface tension between oil and water.Greasy dirt molecules are dispersed to small particles by moistening, penetration and emulsification, making the dirt fall off under a mechanical force effect, reaching the purpose of removing the grease. Such cleaners have advantages as high detergency, moderate action,low toxicity and low price, widely used as detergents.Research on kitchen cleaners with surfactants as the active ingredient will be highlighted below.

Kitchen cleaners

There are many advantages for surfactants which were used in the kitchen cleaner. Based on the characteristics of greasy dirt and the different usages, generally three types of cleaner product are popular to be seen in the market: liquid, paste and powder. Research results show that permeability, emulsification and dispersal of cleaners to dirt can be strengthened by reasonable mixing of surfactants and interaction with builders, improving the cleaning effect on kitchen greasy dirt. For liquid products,no inorganic builders can be added, so generally organic solvents will be added to improve the dirt removal effect.For powder products, dirt removal effect can be improved by mixing with inorganic builders.

Heavy kitchen grease dirt cleaner

Heavy kitchen grease dirt has complicated ingredients,mainly including aldehyde, aromatic compounds,heterocyclic compounds, esters, ketones, lactone,hydrocarbons and fatty acids. Such greasy dirt is formed by unsaturated fatty acid esters at high temperatures for a long time, and finally attach to the surface of kitchen appliances, walls and exhaust hoods. For such heavy cross-linked greasy dirt, usually, the most frequently used method is mixing alkalis, solvents and surfactants with solvent penetration and dilution, alkali saponification and neutralization, as well as surfactant emulsification to reach an ideal removal effect.

Heavy alkaline greasy dirt cleaner.Yan Yuan, et al.[6]conducted investigations on the cleaning effect of solvents,alkalis and surfactants on heavy kitchen greasy dirt. The results showed that the three substances had varying degrees of detergency on heavy kitchen greasy dirt, and lacking of any one of them would affect the product detergency to a great extent. In terms of formula design, the best heavy kitchen greasy dirt cleaning effect might be achieved by reasonable compounding.

Yan Jia, et al.[7]designed a heavy kitchen greasy dirt cleaner formula by mixing of surfactants LAS (2%～5%),AES (2%～4%), AEO (4%～6%), and washing builders like triethanolamine and sodium benzoate in a certain order.Through the detergency test, the dirt removal rate was up to 97% and the corrosion rate was nearly zero. It was also found in the experiment that the addition of a few additives could improve the cleaning activity and stability owning to synergistic effect with surfactants and reduce cost at the same time.

The research of Tan Xiaojun[8]indicated that surfactants, alkalis and solvents have different abilities to remove heavy kitchen greasy dirt, where solvents have the strongest detergency followed by alkalis and surfactants.Surfactants, alkalies and solvents were selected by the singlefactor detergency test, and finally mixed ingredients were determined. The mixing ratio was adjusted on the orthogonal test, and the kitchen heavy greasy dirt cleaner formula was obtained as follows: AEO9 (1%), triethanolamine (3%) and diethylene glycol monobutyl ether (4%～6%), where the chelating agent and corrosion inhibitor were also included.The detergency of formula can reach to 90%.

Zhao Leyi, et al.[4]made the product into powder,beneficial to increasing alkalinity and reducing cost. The formula contained 0%～8% non-ionic surfactant, 5%～15%anionic surfactant, 5%～40% phosphate, 0%～30% silicate,3%～10% solubilizer or organic solvent and 15%～30%other additives. The experiment results indicated that the product has good cleaning effect.

Liu Qinggang, et al.[10]developed a water-based kitchen cleaner by using the surfactant mixing technique and obtained the variation rule of between component contents with detergency of the cleaner. The results indicated that the kitchen cleaner had high detergency of up to 99.0%; the product was free of organic solvents, low in alkalinity, without corrosion to stainless steel, copper,aluminum and other common metals, without damage to the paint surface of kitchen appliances, and will enjoy extensive market prospects.

The dirt on the stove and exhaust hood was also a kind of kitchen heavy greasy dirt. Generally, stove cleaner is used to remove the grease attached to the surface of stoves and ovens and carbon dirt sediment formed by burning under oxidation at high temperature. Guo Likan, et al.[11]developed a special cleaner for stoves based on the characteristics of stove equipment, which could effectively removed the dirt on the surface of stove ware. The cleaner is mixed by alkaline ingredients (NaOH), surfactants (alkylolamides, alkylphenol ethoxylates or fatty alcohol-polyoxyethylene ether) and organic solvents (alcohol ether). When using, carbon dirt sediment were softened by surfactants and organic solvents,and then rapidly dissolved by strong alkalis, without any effect on human health.

At present, special cleaners for exhaust hoods are generally composed of penetrants, swellers, softeners and emulsifiers. Li Yujun, et al.[12]developed a low-cost,environmentally-friendly, safe and efficient water-based heavy greasy dirt cleaner, based on the characteristics of the exhaust hood. The formula was optimized by the orthogonal test: anionic surfactant (4%), alkyl glycoside(3.5%), sodium alcohol ether sulfate (1.0%), sodium dodecyl benzene sulfonate(0.5%), sodium citrate (l%)and triethanolamine (3%). Upon comparison of the detergency of the self-made cleaner, and a commercially available kitchen cleaner at 10°C and 30°C, it indicated that the self-made cleaner has a good cleaning effect.

Jiang Li, et al.[13]researched the formula of waterbased heavy grease dirt cleaner for exhaust hoods, and discussed the detergency mechanism by the orthogonal test, using the cleaning efficiency as the evaluation methods. The results indicated that the cleaning efficiency of cleaner, obtained from the experimental formula,significantly higher than the commercially available product, with the detergency of 99.8% on washing for 10 min. The cleaner has many advantages, such as low raw material cost, less corrosion to metal, safety and environmental protection.

Weak acidic heavy grease dirt cleaner.Weakly acidic heavy grease dirt cleaner can effectively solve high corrosion of strongly alkaline cleaners to kitchen appliances and damage to human skin, and can solve the problems of solvent-based cleaners as being flammable and explosive, steam toxic to the human body, high cost and unsafe use. Gu Mengmeng et al.[14]successfully developed an efficient, environmentally-friendly, weakly acidic water-based cleaner for kitchen purposes by the orthogonal test, and obtained the optimum formula as follows: sodium diethylhexyl sulfosuccinate (4.4%),sodium alcohol ether sulphate (4.4%), alkyl glycoside(6.4%) and cocoamidopropyl betaine (7.5%). The results indicated that the self-made cleaner (pH: 6.5) is nonirritating to skin, has good detergency and is very simple in formula composition and preparation process.

Neutral heavy grease dirt cleaner.According to incomplete statistics, more than 70% of kitchen appliances must be cleaned with neutral cleaners, so it is significance to develop new neutral heavy grease dirt cleaner, and it is necessary to have good detergency under neutral conditions.

Li Quanqing, et al.[15]obtained a neutral microemulsion formula by using a specific greasy dirt molecular penetration,moistening and emulsification effect of surfactants, greasy dirt solubilization, dispersity and emulsification with surfactants, and the chelation and anti-resedimentation of inorganic builders, according to the action principle of surfactants. Comparing with the commercially product, the obtained product had good detergency, which can be close to the commercially available strong alkaline formula product,without damage to kitchen appliances, non-irritating and safe to the human body. The microemulsion kitchen heavy grease dirt cleaner was characterized by rapid cleaning, safe usage,low cost and good detergency, without damage to human skin, enjoying good market prospects.

Kitchen light grease dirt cleaner

Dish washimg detergent.Along with the general improvement of environmental awareness, green and biodegradability of dish washing detergent has become the research direction. Zhang Xuechun, et al.[16]prepared tableware detergent using octenyl-succinate sugar ester with cane molasses as the raw material, and mixed octenylsuccinate sugar ester as the raw material. The results indicated that the dish washing detergents were characterized by non-irritation to human skin, low cost, suitable viscosity and good detergency. Wei Xingchuan[17]prepared an environmentally-friendly dish washing detergent by mixing alkyl glycoside (APG), LAS, betaine and AES,and the detergency, viscosity, irritation, foaming, and other indicators were tested. The results indicated that the formula could achieve strong detergency, and that the other main performances could meet the requirements for standard dish washing detergents.

Fu Jianwen, et al.[18]studied the application of the mixture of cationic surfactants alkyl hydroxyethyl dimethyl ammonium chloride (Prepagen HY), and anionic surfactants LAS and AES in tableware detergent and pH,viscosity, cloud point, stability, foaming, detergency of the mixed system were measured. The results indicated that Prepagen HY had excellent synergetic efficiency with AES and LAS, which can improve the viscosity, foaming and detergency of dish washing detergents.

Microemulsion systems have ultralow interfacial tension,strong emulsification and solubilization, and effective penetration, so it is significant to develop microemulsionbased dish washing cleaner. Cai Zhaosheng[9]developed a weakly alkaline, micro-emulsion-based kitchen dish washing cleaner, where surfactants, emulsifiers, alkaline builders and alcohol ethers were dispersed in water at a given proportion, in sequence, forming micro-emulsions,which integrated the advantages of strong alkaline, solventbased and surfactant-based cleaners. The performance evaluation test results indicated that it could effectively remove greasy dirt on hard surfaces for a good dirt removal effect when cleaning kitchen appliances and hard surfaces.Surfactants can promote moistening and penetration of greasy dirt surfaces, and disperse, solubilize and emulsify greasy dirt; emulsifiers can promote alcohol ether solvents to disperse in water, forming micro-emulsions; alkaline builders can promote partial saponification by contacting greasy dirt, and can swell the resinous substances formed by polymerization of unsaturated grease, to reduce the binding of greasy dirt with solid surfaces and the compacting of greasy dirt; alcohol ether solvents have good swelling and dissolving effects on deteriorated oils formed by greasy dirt(particularly unsaturated grease), and can effectively reduce the binding of greasy dirt with solid surfaces to promote the cleaning of greasy dirt.

Kitchen floor cleaners.When cooking in the kitchen,greasy substances will be spilled on the floor. To clean such dirt in a timely manner, researchers have developed a kitchen floor cleaner.[19]The product is made from surfactants and builders with strong emulsification and penetration. Based on environmental considerations,the products mainly refers to colorless and transparent water-based cleaners, at present. The products have strong emulsification, so long-term skin contact should be avoided, as much as possible. In addition, there are different treatment methods for different floors. For example, for cement floors, products should be diluted properly, and should be rinsed off in a short time, without residue.

Disincrustant & rust removers.Incrustant is the most common situation for kitchen in daily life. In addition, if the water inlet is galvanized, the protective layer of the pipelines inner wall will also be lost due to water friction, resulting in iron corrosion and rust production. Disincrustant & rust removers can rapidly remove floating rust, and long-term accumulated impurities and dirt on the metal, ceramic tile, plastic and other rigid surfaces. It is a very useful kitchen cleaning product. According to a market survey on cleaners in the USA in 2012, the disincrustant volume growth rate of such disincrustant & rust removers was very considerable.[20]

To avoid equipment corrosion caused by scaling off &rust removal, disincrustant & rust removers are comprised of efficient surfactants and organic acids, mainly including mixed acids, penetrants, corrosion inhibitors and waterbased chelating agents. This kind of product has good property of removing dirt, rust & scale high cleanliness,non-irritanting and safe to skin.

Conclusion

In recent years, along with more and more attention to environmental protection, “greening” concept has put forward in every industries. For the daily chemical industry, green chemical industry has become the development trend,[21,22]which requires low energy consumption and small pollution in the product preparation process, low content of hazardous substances in the product, non-toxicity to human body, small irritation and good biodegradability.[23]Among the various kitchen cleaners, surfactant-based cleaners have distinct advantages, which are also the development trend in the future. Along with the development of green surfactants, the market share has been increasing year by year. The industrial production[24]and application research of fatty alcohol polyoxyethylene ether sulfate (AES), alkyl polyglycoside(APG), fatty acid methyl ester sulfonate (MES) and fatty acid methyl ester ethoxylate (FMEE) have been making progress,and the research and production of various green kitchen cleaners will also step into a new development stage.

Foundation item

National Natural Science Foundation of China (NSFC)(No.41171250)

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