EFFECT OF SELECTED ENZYMES ON PERFORMANCE OF LIQUID LAUNDRY DETERGENTS Anita Bocho-Janiszewska University of Technology and Humanities in Radom, Faculty of Materials Science and Design, Department of Chemistry, Corresponding address: Chrobrego Str. 27, 26-600 Radom, Poland, [email protected] Abstract : The article examines the effect of type of selected enzymes on the performance of liquid laundry detergents. Enzymes are the catalysts of biological processes. Like any other catalyst, an enzyme brings the reaction catalyzed to its equilibrium position more quickly than it would occur otherwise. The most widely used detergent enzymes are hydrolases, which remove soils consisting of proteins, lipids, and poly-saccharides. Soil and stain components with good water solubility are easily removed during the cleaning process. Most other stains are partially removed by the surfactant system of a detergent, although the result is often unsatisfactory. In most cases a suitable detergent enzyme aids the removal of soils and stains. Whereas the detergent components have a purely physicochemical action, enzymes act by degrading the dirt into smaller and more soluble fragments. In the research samples of liquid laundry detergent containing selected hydrolases (lipase, amylase and protease) were prepared. Tests of the performance of liquid laundry detergents: viscosity, foaming properties and washing properties were conducted. Studies were carried out at three differe nt temperatures: 20, 30 and 40° C. For the sake of comparison, the same tests were also performed for a commercially available product. The addition of the enzyme does not affect the viscosity and foaming ability of the liquid laundry detergent. The ability to remove stains by the liquids containing enzymes was high even at a lower temperature. Nevertheless, the complete removal of the stain requires the joint action of the enzyme and the surfactant system. Keywords: liquid laundry detergents, enzymes, hydrolases, washing ability, foaming properties. 7 1. INTRODUCTION Liquid detergents are convenient products. Compared with powdered detergent they dissolve more rapidly, particularly in cold water, they generate less dust and they are easier to dose. A typical liquid laundry detergent consists all or some of the following components: surfactants, builders, optical brighteners, polymers and enzymes [Lai 1997, Smulders 2002, Aehle 2004]. Both anionic and nonionic surfactants are used in the formulations of liquid detergents. Surfactants are primarily responsible for wetting the surfaces of fabrics as well as a soil, helping to lift the stains off the fabric surface and suspend dirt particulates in solution [Broze 1999, Smulders 2002, Tadros 2005]. Builders are introduced into detergents mainly to sequester the hardness of the water. Common builders used are phosphorus compounds (in regions where they are still permitted in detergent products – these compounds have been identified as possible cause of eutro-phication of lakes and rivers and they are severely controlled and even banned in several countries), carbonates, zeolites, salts of polyacetic acid (EDTA) and citrates [Smulders 2002, Mahrholz, Klein and Klein 2004, Yangxin, Jin and Bayly 2008]. Polymers are used in liquid laundry detergents as soil antiredeposition agents, soil release agents and dye transfer inhibitors. Frequently used polymers are carboxymethyl cellulose (CMC) derivatives, polyethylene terephthalate and polyoxyethyleneterephthalate (PET-POET polymer) and polyvinylpyrrolidone (PVP) [Bertleffet et al. 1998, Smulders 2002, Lai 1997]. Enzymes improve cleaning performance by degrading large complex molecules such as proteins, starches and fats. The reaction products are more soluble in the washing liquor and can be removed by the surfactants more 8 efficiently. Enzymes also help to maintain whiteness and brightness and clarify colors by removing fuzz. They even can improve fabric softness [Maase and van Tilburg 1983, Olsen and Falholt 1998, Aehle 2004, Zhanget et al. 2014]. Enzymes are proteins. These large organic molecules are produced by all living cells. They catalyze most chemical reactions in biological systems, usually at low temperature and at the neutral pH, with an extreme efficacy. They usually exhibit a very high specificity, reacting on one particular chemical compound or even on one given bond within the molecule [Broze 1999, Aehle 2004]. Detergent enzymes are not so specific. The most widely used detergent enzymes are hydrolases which catalyze the hydrolysis of a chemical bond. There are four types of hydrolases currently being used in liquid laundry detergents: protease, lipase, amylase and cellulase [Broze 1999, Aehle 2004]. Proteases support the removal of many soils commonly encountered by the consumer such as food stains, blood and grass. These enzymes catalyze the hydrolysis of the peptide bond found in proteins resulting in the formation of smaller and more soluble polypeptides and amino acids [Wolff et al. 1996, Subba et al. 2009, Singh et al. 2012, Zhang et al. 2014]. Amylase enzymes work on food stains of the starchy variety, like rice, sauce or gravy. These enzymes catalyze the hydrolysis of 1-4 glucosidic bonds in starch [Kravetz and Guin 1985, Hoshino and Tanaka 2003, Hoshino, Tanaka and Kanda 2006]. Lipase enzymes target the oily, greasy stains that are some of the most difficult stains to remove. Lipases catalyze the hydrolysis of mostly the C1 and C3 bonds in the triglyceride molecule, yielding free fatty acids and diglyceride [Varanasi et al. 2001, Bora 2014]. Cellulases are capable of degrading the structure of damaged cellulose fibrils which exist mostly at the surface of cotton fiber s after multicycle washing and using. Cellulases cleave β -1,4- 9 glucosidic bonds incellulose and operate directly on the natural cotton fibers. Cellulases bring diverse benefits: fabric softening, color brightening, antipilling, soil-release properties and antiredeposition [Calvimontes, Stamm and Dutschk 2009, Calvimontes, Lant and Dutschk 2011]. The aim of this study was to determine the effect of various enzymes on the performance of liquid laundry detergents. In the paper samples of liquid laundry detergent containing selected hydrolases (lipase, amylase and protease) were prepared. Tests of the performance of liquid laundry detergents: viscosity, foaming properties and washing properties were conducted. The studies were carried out at three different temperatures: 20, 30 and 40° C. For the sake of comparison, the same tests were also performed for a commercially available product. 1. MATERIAL AND METHODS The study examined liquid laundry detergents containing three enzymes: protease, amylase and lipase. The formulation of the liquid laundry detergent tested is specified in Table 1. For the purpose of comparison, an enzyme-free laundry detergent (Base) and a commercial product (Com) were also tested. The composition of the commercial product, based on the m anufacturer’s data, includes 5-15% anionic surfactants, <5% nonionic surfactants, phosphonates, soap, enzymes, fragrance. Viscosity measurement Dynamic viscosity measurements were performed with Brookfield DV-III rotational viscometer. Viscosity is measured with a rotating measuring tip called the spindle, which is immersed in the test fluid. Testing was performed at a temperature of 20 °C, with the spindle rotating at 10 rpm. 10 Table 1. Formulation of liquid laundry detergent tested Composition [ wt. % ] INCI Name Base P A L MixS Mix0 Laureth -7 10 - Laureth -3 3 - Sodium Laureth Sulfate 7 - Propylene Glycol 2 Sodium Citrate 1 Protease - 0.5 - - 0.5 0.5 Amylase - - 0.5 - 0.5 0.5 Lipase - - - 0.5 0.5 0.5 Aqua to 100 Source: Authors own study Foaming properties measurement The foaming properties were determined using a method set out in the Polish standard [Polish Standard – foaming properties]. The method involved a measurement of the volume of foam produced by a free flow of the gel laundry detergent solution from a distributor onto the surface of the same solution inside a graduated cylinder. Measurements of volume were performed after 30 s, 1 min and 10 min. The concentration of the test solutions was 1 wt%. Based on measurements, two parameters were determined: - foaming ability, FA [cm 3] – volume of foam produced after 30 s. - foam stability, FS [%]: 11 V FS = 10 4100 []% V 1 where: V10 – volume of foam measured after 10 min [cm 3], V1 – volume of foam measured after 1 min [cm 3]. Washing properties measurement The washing properties were determined on the basis of methodology set out in the Polish standard [Polish Standard – washing properties]. The method involved washing of pieces of soiled test fabric in the test washing agent in strictly defined conditions. Pieces of cotton fabric were stained with, previously mixed, three types of soils: tannic, fat and protein. The fabric pieces were dried overnight in the open air. Fabrics prepared in this way were washed separately in the liquid laundry detergent tested. The concentration of the test liquid laundry detergent was 1 wt %. After washing, the pieces of fabric were rinsed and ironed, and their degree of whiteness was assessed. Based on tests, the following parameters were determined: - washing ability, WA [%]: X - B WA = 4100 []% A- B where: X – average degree of whiteness of soiled fabric after washing, B – average degree of whiteness of soiled fabric before washing, A – average degree of whiteness of unsoiled (control) fabric. 12 3. RESULTS AND DISCUSSION Viscosity