Study on the Stability and Compatibility of the Cosmetic Products with Lavandula angustifolia Oil Kept in PPH Polypropylene Homopolymer Plastic Containers

MIHAELA BOGDAN1, LAURA ENDRES1, BIANCA PASCA1, DELIA MIRELA TIT1*, DIANA UIVAROSAN1, DANA MARIA COPOLOVICI2,3*, LOTFI ALEYA4, SIMONA BUNGAU1 1 University of Oradea, Faculty of Medicine and Pharmacy, 29 N. Jiga Str., 410028, Oradea, Romania 2Aurel Vlaicu University, Faculty of Food Engineering, Tourism and Environmental Protection, 77 Revolutiei Blvd., 310130, Arad, Romania 3 Institute for Research, Development and Innovation in Technical and Natural Sciences, Romania, 2 Elena Dragoi Str.,Arad, 310330, Romania 4Laboratoire Chrono-environnement, Universite de Franche-Comte, Besancon, F-25030, France

The curative effect of essential oils on mind, body, and spirit has demonstrated its importance for centuries. These very powerful organic chemicals in plants, named aroma molecules, have the property of removing viruses, bacteria and fungi from surrounding areas [1,2]. The popularity of aromatherapy is growing, cosmetics brands including essential oils on a large scale in their products. Consumers that do not mind paying more for natural products determined new formulations and innovations in the cosmetics industry. Products used in aromatherapy quickly gained popularity in the cosmetics market that includes perfumes, emollients and body creams [2].
Lavandula angustifolia oil is the volatile oil obtained from the flowers of the Lavender, Lavandula angustifolia, Labiatae [3]. Although the mechanisms of action of lavender oil are not entirely known, it has antifungal and antibacterial properties on many different bacteria species, especially when antibiotics have no effect [4]. The use of lavender oil in aromatherapy for the treatment of stress, headaches, abrasions, skin problems, painful muscles, primary dysmenorrhea, burns and stimulation of the immune system is well documented [5][6][7][8].
Among the properties of lavender essential oil in cosmetics we can list: relieves dry skin, detoxifies pores and stimulates cell regeneration [2,9]. In order to preserve its properties in cosmetic products it has to be incorporated into well-studied formulations together with compatible components so that the final cosmetic product fulfills the quality standards when stored in proper conditions for functionality and aesthetics, to preserve their chemical, microbiological and physical properties. The stability of the final product is directly influenced by the primar y packaging, due to the many interactions that may occur between the product and the packaging on the one hand * email: mirela_tit@yahoo.com; danaban76@gmail.com All authors have equal contribution at this paper.
(corrosion, chemical reactions, migration adsorption of product components into the container) and between the product, the packaging and the external environment, on the other hand (the effectiveness of a container to protect the contents from the effects of water and/or atmospheric oxygen vapour and to ensure the retention of volatile product and water components is represented by the barrier properties of the container) [10]. In this study, the stability and compatibility of a new cosmetic product containing lavender essential oil was tested and stored in a 100 mL volume PPH plastic homopolymer (Moplen HP648T) plastic container. PPH is the result of the specific polymerization of propane using a Ziegler-Natta catalyst, by injection [11][12][13]. It appears in granular form, stabilized under normal conditions, having a natural color and very good chemical resistance to various chemical agents, basic or acidic. The material is used for the manufacture of parts of household appliances, technical products, medical devices, and packaging containers used in various industrial branches: food, textile, electrotechnics, etc. Our results were compared with those obtained for the same product, stored in a glass container and used as control.

Experimental part Material and method
Tested product was hand and body cream, formulated and prepared from 100% natural ingredients (table 1) in Viridis Cosmetics laboratories, by pharmacist Mihaela Bogdan.
The distilled water was obtained in the private laboratories with a GFL / 205458 type 2008 distiller. The raw materials were purchased from Mayam Elemental (Romania), all of them were accompanied by a quality certificate. The preservative used (Phenoxyethanol, Ethylhexylglycerin) was provided by Gracefruit LTD (England). All materials used in the formula have been applied in accordance with their purpose, in a permitted quantity and do not constitute a threat to human health. The raw materials used to formulate this product are all well-known ingredients with a long history of safe use. The product obtained is characterized by the parameters described in table 2. established time intervals (7, 14 and 28 days) for each strain -20 g of the test formulation 0.2 mL of calibrated inoculum: 1.0x10 5 -1.0x10 6 cfu/g for bacteria, and 1.0x10 4 -1.0x10 5 cfu/g (cfu -unit-forming colonies) for Candida albicans and Aspergillus brasiliensis. The determination materials and parameters are shown in table 3 [14].

Results and discussions
In order to assess the stability and compatibility of the product with the plastic container, the parameters of the cosmetic product were monitored both in the tested container and in glass containers, used as controls, in identical conditions. Stability and compatibility testing of product in plastic container is presented in table 4.
The monitoring of the tested product parameters in the plastic container showed that there were no significant changes of the product submitted to test conditions during the assessment. The stability and compatibility tests of the studied cosmetic product in plastic packaging shown stable results, comparable with the organoleptic and physicochemical test results of the control sample stored at room conditions. The appearance of the product tested in plastic container, depending on the temperature variations, is illustrated in figure 1.
There were no changes in appearance, color and fragrance not even in the cycle-test evaluation (table 5). Stability and compatibility testing of product in glass container is presented in table 6.
The appearance of the product tested in glass container, depending on temperature variations, is illustrated in figure  2.
The chemical composition of the plastic container, declared by the producer (Synthesia Grup, Romania) is: plastic jar 100 mL PPH Polypropylene homopolymer (Moplen HP648T) and cup PS Styrene homopolymer (Styrolution PS GPPS) with the chemical structure shown in figure 3.
The appearance, smell and color of the plastic container product were monitored under the same conditions; the results are presented in table 7. The Challenge Test  Depending on the product category (emulsion / homogenous cream), we have chosen the most appropriate testing methodology for this type of product. We considered the evaluation of critical aesthetic properties such as organoleptic properties (appearance, color, perfume), but also physicochemical parameters (density, pH, temperature cycle test (5-40 three series), temperature variations I 40°C, II 5°C and a control sample at room temperature RT (temperature 0 being 25°C).
The purpose of the test was to ensure stability, physical integrity, microbiological stability and compatibility of the contents with the original packaging of our cosmetic product under appropriate storage, transport and use conditions. Thus, after determining the stability and compatibility with the container, an assessment of the antimicrobial preservative of the cosmetic product was also carried out; the evaluation was done by using a challenge test according to SR EN ISO 1190: 2012 [14]. The assay implies the contamination of the formulation with a determined inoculum with known density and the monitorization of viability of test microorganisms at pre-    confirmed the efficacy of the preservative, the formulation fulfilling the A type criteria [14]. Table 8 presents the stability of the product from the microbiological point of view.
According to SR EN ISO 11930/2012 a deviation of 0.5 log from the established criteria is accepted. R x .lgN 0 -lgNx where: N 0 -number of the micro-organisms inoculated at time t 0 ; N x -number of surviving micro-organisms at each sampling time t x ; NI -no increase in the count from the previous contact time T7, T14, T28 days; NP -not performed.
Innovation and development in the cosmetics industry determine a direction that promotes health before beauty [15][16][17].
The products used in cosmetic formulations are constantly diversifying as a result of researches in the field, which combine the healing and prevention of many skin conditions with the use of natural products such as vegetable extracts and essential oils [9,18,19]. Research and innovation in this field, as well as in pharmaceutical and environmental fields [20,21] have become necessary, especially nowadays when physical, chemical, and environmental aggressions on the skin cause increasing incidence of skin cancers [22,23].
Testing product attributes that are likely to change while stored, influencing the quality of the cosmetic product, are included in the protocols for cosmetic stability studies. Tests performed in real time or under accelerated conditions must ensure the stability and physical integrity of cosmetic products under appropriate storage and transport conditions, chemical and microbiological stability as well as the compatibility of the contents with the container [24].
Studies on the cosmetics or on their components stability usually include and focus on different accelerated storage conditions under which the samples are kept, in elevated temperature (37, 40 or 45 °C), during different periods of time (1 to 3 months), depending on the product type [24][25][26][27][28][29]. In this study, the aspect, color, fragrance, pH and density were monitored in conditions of temperature variation from 5 to 40 °C, during a period of 2 months.
The tests were carried out in plastic containers (the body and hand cream) which were tested to determine the compatibility of the cream with the material, and in glass containers for control. The stability and compatibility tests of the studied cosmetic product in plastic packaging shown stable results, comparable with the organoleptic and physicochemical test results of the control sample stored at room conditions. The changes in pH of the cosmetic product in original packaging and glass container after test in temperature variations I (40 °C) did not affect the other physical and chemical parameters (aspect, color, smell, density).
The antimicrobial and protection properties of the cosmetic product have also been tested. To ensure the safety of the cosmetic product, microbiological testing is important. The ISO 29621 [30] standard requires that every cosmetic producer has to guarantee that the products they make do not contain microorganisms that may influence the quality of the cosmetic product, that the use of it does not influence negativelly the consumer's health. According to SR EN ISO 1190: 2012 [14], the Challenge Test is used for microbiological tests of newly formulated cosmetic products. In this study the results confirm the microbiological stability of the tested product. In order to keep regulations comming out from above mentioned ISO and EN standards it will be necessary to continue in this research and test the stability of cosmetics products from the point of their odourfor instance by employing electrochemical sensors [31,32].

Conclusions
The studied product remained stable, regarding the physical and chemical properties, and the microbiological aspect, being compatible with both plastic and glass containers during the test, at storage temperatures that is recommended to be under 40 °C; also, it does not interact with the material of which the container is made.