Does application of Petroselinum crispum and Levisticum officinale Koch. extracts improve the thermal stability of vegetable oils?

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1 Cristina POPOVICI, Tatiana CAPCANARI, Olga DESEATNICOVA and Rodica STURZA Does application... Does application of Petroselinum crispum and Levisticum officinale Koch. extracts improve the thermal stability of vegetable oils? Cristina POPOVICI, Tatiana CAPCANARI, Olga DESEATNICOVA and Rodica STURZA Technical University of Moldova, 168 Stefan cel Mare St., MD-24 Chisinau, Republic of Moldova Phone: , Fax: , cristina_popovici@mail.md Abstract Parsley and lovage are known not only for their taste, aroma and flavour, but also for their antioxidant effects and properties. Parsley and lovage contain phenolic substances such as phenolic acids, flavonoids, phenolic diterpenes and volatile oils. Phenolic compounds in these plant materials are closely associated with their antioxidant activity and also play an important role in stabilizing lipid peroxidation. Efficacy of parsley and lovage extracts in stabilizing sunflower and grape seeds oils in thermal oxidation conditions has been studied. Extracts of parsley and lovage were prepared in water/ethanol solutions, total polyphenol content (TPC) was in the range of mg/ml and antioxidant activity range in the extracts was %. Being highest in TPC and antioxidant potential, parsley and lovage extracts were added to vegetable oil mixtures. Obtained samples of oils with extracts were heated at 16 C. The oxidation of the oil samples was evaluated by means of free fatty acids content, peroxide and p-anisidine value. The results of UV/Vis spectroscopy confirm stabilization effect on thermal oxidation of the tested oils. This study demonstrates that natural plants extract such as parsley and lovage can effectively inhibit the lipid oxidation of sunflower and grape seeds oil mixture in thermal oxidation conditions. Keywords: antioxidants, natural plant extracts, parsley, lovage, sunflower oil, grape seed oil, free fatty acid content, peroxide value, p-anisidine value, thermal stability. Rezumat Pătrunjelul şi leuşteanul sunt cunoscute nu numai pentru gust şi aromă, ci şi pentru efectele antioxidante şi proprietăţile lor. Patrunjelul si leuşteanul conţin substanţe fenolice acizi fenolici, flavonoide, diterpene fenolice şi uleiuri volatile. În aceste plante aromatice compuşii fenolici sunt strâns asociaţi cu activitatea lor antioxidantă şi, de asemenea, joacă un rol important în stabilizarea peroxidării lipidice. In lucrarea dată a fost studiată eficacitatea extractelor de pătrunjel şi leuştean asupra stabilităţii uleiurilor de floarea soarelui şi din seminţe de struguri în condiţii de oxidare termică. Extractele din patrunjel şi leuştean au fost obţinute în soluţie de apă/etanol. Conţinutul total de polifenoli (CTP) fiind în limitele de 4,5 7,7 mg/ml, iar activitatea antioxidantă în extracte a variat între 48,8 84,6%. Cea mai mare activitate antioxidantă şi CTP s-a obţinut în extracte de pătrunjel şi leuştean. Datorită conţinutului sporit de polifenoli şi activităţii antioxidante înalte extractele au fost incorporate în amestecuri de uleiuri vegetale. Probele de uleiuri vegetale cu extracte au fost încălzite la 16 C. Oxidarea probelor de uleiuri a fost evaluată prin intermediul conţinutului acizilor graşi liberi, indicilor de peroxid şi p-anisidină. Rezultatele spectroscopiei UV/Vis confirmă efectul de stabilizare în condiţiile oxidării termice a probelor de uleiuri analizate. Rezultatele acestor cercetări demonstrează, că extractele naturale din plante aromatice, cum ar fi patrunjelul si leuşteanul pot inhiba eficient oxidarea lipidelor din amestecuri de uleiuri vegetale analizate în condiţii de oxidare termică. Cuvinte cheie: antioxidanţi, extracte din plante naturale, pătrunjel, leuştean, ulei de floarea soarelui, ulei din seminţe de struguri, conţinutul de acizi graşi liberi, indice de peroxid, indice de p-anisidină, stabilitate termică. 313

2 Papers of the Sibiu Alma Mater University Conference, Fifth Edition, March 211, Sibiu Volume 1 1. Introduction Vegetable oils and fats are recognized as important components of our diet. They provide essential fatty acids such as α-linolenic acid (ω 3 fatty acid) and Linoleic acid (ω 6 fatty acid), fat-soluble vitamines: vitamin A (Retinol), vitamin E (Tocopherols), vitamin K (2-methyl-1,4- naphthoquinone derivatives) and vitamin D (Secosteroids) and other biologically active compounds (Whitney Ellie et al., 28; Robert Goodhart et al., 198). During storage and frying of oils, fats and fatty foods, lipid oxidation is one of the principle causes of quality deterioration. In results in the losses of nutritional value of food as well as changes in colour, texture, sensory and other physiological properties (Valéria Ramalho et al., 28; Fritsch, 1981). In order to retard or prevent the oxidative deterioration and extend the self-life of vegetable oils, adding antioxidants is necessary (Maryam Azizkhani et al., 29; Karpinska et al., 21). In spite of high effectiveness of synthetic antioxidants such as tert-butylhydroquinon (TBHQ), their application is restricted in several countries because of their possible toxicity and carcinogenic effects (Prior, 24; Hou, 23; J. Pocorny et al., 21; Farag et al., 1989). Due to these safety concerns, there is an increasing trend among food scientists to replace these synthetic antioxidants with natural ones, which in general, are supposed to be safer. The effectiveness of different natural sources in stabilizing vegetable oils has been previously studied (Popovici, 28; Anwar et al., 23; Ito et al., 1986). Experiments involving spice oxidation inhibition characteristics began in the 195s. Researchers observed an increased oil stability in the presence of a variety of spices and condiments (Chipault et al., 1955). Within the spices, parsley (Petroselinum crispum) and lovage (Levisticum officinale koch.) are some of those that present good antioxidant ability. The compounds responsible for parsley and lovage antioxidant activity are mainly phenolic acids (caffeic, ferulic, p-coumaric acids) and flavonoids such as flavonol aglycones (quercetin, kaempferol, and their glycosides) (Yıldız et al., 28; Kahkonen et al., 1999; Larson, 1988). In our previous study, total polyphenol content and radical-scavenging activity of parsley and lovage extracts using a stable free radical DPPH were determined (Popovici et al., 21). The obtained results show that tested extracts of parsley and lovage had strong antioxidant characteristics. However, according to these data, the information about tested extracts effectiveness in delaying the deterioration of the oils during frying seems to be limited. The purpose of this current work was to describe the effect of added parsley and lovage extracts in the protection of sunflower and grape seed oils against the thermal oxidation process. 2. Materials and methods 2.1. Materials The refined and deodorized sunflower and unrefined grape seed oils free from antioxidant additions were purchased from a local producer in the Republic of Moldova. The leaves of parsley (Petroselinum crispum) and lovage (Levisticum officinale Koch.) were harvested in late April 21 in central part of Moldova. Fresh and healthy leaves were washed, dried and used in analyses within 24 h after harvesting Chemicals 1,1-Diphenyl-2-picrylhydrazyl (DPPH ) as free radical form (9% purity), Folin-Ciocalteu s phenolic reagent, sodium carbonate and gallic acid were supplied by Sigma-Aldrich. Methanol (99,8%), ethanol (99,9%), chloroform, potassium hydroxide and phenolphthalein were provided by Eco-Chimie (Chisinau, Republic of Moldova). All reagents were of analytical grade. Distilled water was used throughout Drying Super-high frequency and convection drying were used for herbs drying. The SHF drying was performed at 5% and 1% of magnetic intensive. The convection drying was made at 6 C and 8 C Extraction Dried leaves of parsley and lovage were ground before extraction. The dried powder of herbs was extracted with 7% EtOH for 2 h at 6 C and liquid-to-solid ratio 1 ml per gram. The extracts of tasted herbs were filtered with paper filter and after were used in the experiments. Obtained extracts were analyzed for the antioxidant activity DPPH (Brandwilliams et al., 1995) and total polyphenol content (Singleton et al., 1999) assays. 314

3 Cristina POPOVICI, Tatiana CAPCANARI, Olga DESEATNICOVA and Rodica STURZA Does application... Absorbance measurements were recorded on a UV/Vis spectrophotometer HACH-LANGE DR- 5 (Germany). For each extract sample analysis were carried out in triplicate Sample preparation Five oil samples were prepared: sunflower oil, grape seed oil, mixture of sunflower and grape seed oils, mixture of sunflower and grape seed oils with parsley extract and mixture of sunflower and grape seed oils with lovage extract. The content of herbs extract was 1 ml Extract/1 ml Oil in every oil sample. The parsley and lovage extracts were added directly to the oils, followed by slow stirring until complete dissolution. Obtained oil samples were exposed to the thermal oxidation Thermal oxidation test The test for thermal oxidation was performed on the oven SPT 2 Vacuum drier (Germany). The oil samples were transferred in beakers, containing 3 ml of sample. The temperature was set at 16 C. Heating was carried out continuously for 25 min. The amount of primary oxidation products was determined through measuring of peroxide value (PV) and acid value (AV). These were determined according to AOAC Official Method (AOAC, 1999). Formation of secondary oxidation products was measured as p-anisidine value (IUPAC, 1987). Oil samples exposed to the thermal oxidation test were analyzed using UV/Vis spectroscopy (Pretsch et al., 26) Statistical analysis Experimental results were means ± SD (standard deviation) of three parallel measurements and processed statistically by the method of those small squares with application of coefficient Student and determination of interval of investigation (Snedecor et al., 1989). 3. Results and discussion 3.1. Total polyphenol content and antioxidant activity DPPH of parsley and lovage extracts The antioxidant activity expressed as the DPPH values of tested parsley and lovage extracts as well as the amount of total polyphenol content of these extracts are investigated and obtained results are shown in Table 1. The total polyphenol content in parsley and lovage extracts was in the range of mg/ml. The highest content of total polyphenols was in accordance with results of antioxidant function determination found in extracts of parsley and lovage predried by SHF with magnetic intensive 1%. The lowest total polyphenol content was recorded in extracts of lovage dried by convection at 6 C and 8 C corresponding to their low antioxidant function. Using the DPPH assay we obtained a hierarchy of antioxidant activity ranging from 84.6 to 46.8 %. Interestingly, the highest antioxidant function was found in the extracts of herbs samples dried by convection at the temperature of 8 C and by super-high frequency (SHF) drying with magnetic intensive 1%. On the other hand, the antioxidant function of the extracts prepared from herbs exposed by SHF drying with magnetic intensive 1% was significantly higher. There was a direct relationship between the total polyphenol content and antioxidant function in the extracts of herbs predried by different methods and conditions. DPPH values were significantly linearly correlated to the total polyphenol content: R 2 =, Thermal stability of sunflower and grape seed oils with added extracts Oxidative and hydrolytic decomposition is observed in the heating process of vegetable oils. The presence and depth of the process of oil oxidation and hydrolysis is characterized by the content of free fatty acids in oils, i.e., the acid value (AV). The growth of the acid value or intensity in the formation of free fatty acids in the compared oils has a linear character (Table 2). When comparing the acid values of the oil group with added parsley and lovage extracts, one can note that free fatty acids accumulate to a lesser extent in a sample containing a parsley extract as an antioxidative component and that the acid values are,573 and,618 mg KOH/g oil respectively. Table 2 illustrates the intensity of the processes of the formation of the primary oxidation products (peroxides) in the tested oils depending on the heating temperature. Peroxide compounds are known to be unstable. They decompose in the heating process with the formation of the secondary products of vegetable oil oxidation, more stable carbonyl compounds. 315

4 Papers of the Sibiu Alma Mater University Conference, Fifth Edition, March 211, Sibiu Volume 1 Table 1. Comparison of DPPH and Folin-Ciocalteu assays at tested extracts. Drying Total Polyphenol Radical scavenging Herbs Conditions (temperature, C content (TPC), activity (DPPH), Method / magnetic power, %±sd*) mg/ml ± sd* % ± sd* Parsley 6 ± 2 C 5.9 ± ±.61 Convection 8 ± 2 C 6.6 ± ±.69 Super-high 5 ± 2 % 7.4 ± ±.72 frequency (SHF) 1 ± 2 % 7.7 ± ±.71 Lovage 6 ± 2 C 4.5 ± ±.53 Convection 8 ± 2 C 4.9 ± ±.57 Super-high 5 ± 2 % 5.3 ± ±.34 frequency (SHF) 1 ± 2 % 5.9 ± ±.67 *Average concentration of three measurements ± standard deviation. Table 2. Quality indices of sunflower and grape seed oils with/without added extracts Quality indices of the tested oils No Name of oil Acid value Peroxide value samples mg KOH/g oil meq/kg oil p-anisidine Value, c.u. 2 ± 2 C 16 ± 2 C 2 ± 2 C 16 ± 2 C 2 ± 2 C 16 ± 2 C 1. Sunflower oil refined and.183±.2.756± ± ± ± ±.7 deodorized 2. Grape seed oil unrefined.211±.1.873±.5 8.4± ± ± ±.3 3. Mixture of sunflower and grape seed oils.192±.1.774± ± ± ± ±.3 4. Mixture of sunflower and grape seed oils with added parsley extract.191±.3.573± ± ± ± ±.7 5. Mixture of sunflower and grape seed oils with added lovage extract.191±.2.618± ± ± ± ±.3 The change in the intensity of the accumulation of such aldehydes as 2,4-decadienal and 2-octenal in the compared vegetable oils, which is expressed by the amount of the p-anisidine value. The incorporation of the parsley and lovage extracts in the composition of the oils mixture exerts an effective influence on the processes of stabilization of the tested oils. Thus, the p-anisidine value of the oils mixture without extracts came to c.u. after heating process, and this value of the oils with the parsley and lovage extracts decreased and varied from to c.u. respectively. Figures 1 5 show UV/Vis spectra of tested sunflower and grape seed oils, their mixture with/without extracts. It was established, that spectra of tested oils with parsley and lovage extracts is characterized by peaks at 325 nm, which is specific for polyphenol compounds Wavelenght,nm Figure 1. UV/Vis spectra of sunflower oil. 316

5 Cristina POPOVICI, Tatiana CAPCANARI, Olga DESEATNICOVA and Rodica STURZA Does application ,6,5,4,3,2,1 -,2 Figure 2. UV/Vis spectra of grape seed oil. -,1 Figure 3. UV/Vis spectra of sunflower and grape seed oils mixture 4 3,5 3 2,5 2 1,5 1,5 -,5 Figure 4. UV/Vis spectra of sunflower and grape seed oils mixture with added parsley extract When comparing the quality indices and obtained UV/Vis spectra of tested oils with extracts (parsley and lovage) incorporated into the oil samples, one should note that the antioxidative components of the parsley extract exert the greatest influence on inhibiting the processes of oil thermal oxidation. 4 3,5 3 2,5 2 1,5 1,5 -,5 Figure 5. UV/Vis spectra of sunflower and grape seed oils mixture with added lovage extract 4. Conclusions The results of this study indicate that the antioxidant activity of herbs extracts depends on various factors: herbs species, method and conditions of drying. The parsley extract was the most abundant source of polyphenol compounds and showed the highest value of antioxidant activity in the group of the studied extracts. The incorporation of the natural plant extracts into the composition of the mixture of sunflower and grape seed oils exerts an effective influence on the processes of stabilization of the tested oils; i.e., it inhibits the intensity of the accumulation of the primary and secondary oxidation products during thermal oxidation process. References Anwar F., Bhanger M.I., Yasmeen S. 23. Antioxidant activity of some natural extracts in corn oil. In N. Muarata, M. Yamada, I. Nishida, et al. (Eds.), Advanced research of plant lipids. Proceeding of 15- ISPL, May 12-17, 22, Okazaki, Japan. Netherlands: Kluwer Publishers. p AOAC, Official methods of analysis, 16 th Ed. AOAC International, Gaithersburg. Azizkhani Maryam, Parvin Zandi, 29. Effect of some natural antioxidants mixtures on margarine stability. World academy of science, Enginiring and technology, 49, p Brandwilliams W., Cuvelier M.E., Berset C., Use of a free-radical method to evaluate antioxidant activity, LWT-Food. Sci. Technol. 28, p Chipault J.R., Mizuno G.R., Lundberg W.O Antioxidants properties of spices in oil-in-water emulsions. Food res. 2, p

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