Journal of Food and Nutrition Research (ISSN 1336-8672) Vol. 57, 2018, No. 1, pp. 87–97
Composition, antioxidant activity, thermal and oxidative stability of Lecythis tuyrana oil
Andrés Felipe Alzate Arbeláez – Álvaro Cogollo Pacheco – Benjamín Rojano
Summary Oil from Lecythis tuyrana oilseeds is extracted for its potential use in food industry. The aim of this study was to gain knowledge on composition, antioxidant activity and thermal oxidative stability of this type of oil. Compositional parameters were evaluated. Antioxidant activity was evaluated by oxygen radical absorbance capacity and 2,2-diphenyl- 1-picrylhydrazyl radical. Oxidative stability was evaluated by peroxide value, thiobarbituric acid reactive substances values and oxidative stability index (OSI). Thermal stability was determined by thermogravimetric assay and differen- tial scanning calorimetry. Almonds were found to have a high oil content of 732 g·kg-1. Total carotenoids, tocopherols and phenols were also quantified. OSI showed an induction time of 3.47 h and it was thermostable up to 200 °C. It was possible to improve the stability of oil by 27.5 % under accelerated conditions, using butylated hydroxytoluene as an antioxidant. L. tuyrana is a good source of unsaturated fatty acids (oleic acid 369.0 g·kg-1, linoleic acid 272.0 g·kg-1, palmitic acid 171.0 g·kg-1, stearic acid 149.0 g·kg-1, arachidonic acid 10.0 g·kg-1, palmitoleic acid 7.0 g·kg-1), which are oxidatively stabilized by the presence of carotenoids, phenols and tocopherols. In this way, the new oil with interesting nutraceutical properties is proposed to be used in the food, cosmetic and pharmaceutical industry.
Keywords edible oil; Lecythis tuyrana; oxidative stability; thermal stability; oilseeds
Demand for new sources of vegetable oils with this tree are desired by several rodent species [4]. a high content of unsaturated fatty acids, as oleic, However, reports on L. tuyrana from the point of linoleic and linolenic, has promoted the study of view of the generation of agronomic crops in Co- new species, Lecythidaceae family being one of the lombia, uses in traditional medicine, composition most promising. Genus Lecythis consists of about and stability of the oil extracted from the almonds 26 species distributed from Nicaragua to Brazil’s and their potential use in food products with a nu- Amazon with 73 % of species found there [1]. In tritional function, are very few. Colombia, this genus is found in altitudes of 200 m The quality of oils is determined by its chemi- above sea level, in particular on banks of the Pa- cal composition and the presence of antioxidant cific and Caribbean rivers. Lecythis tuyrana is bioactive substances, which act directly on the a species of large tree, which is threatened by de- oil’s stability, providing a greater added value. forestation for its use as timber [2]. In their natura Carotenoids, tocopherols and polyphenolic com- habitat, L. tuyrana trees can reach up to 60 m of pounds are among these bioactive substances [5]. height, they have large, woody fruits, which are Two studies report that the seeds of some species also dehiscent and subglobose (9.5–14.5 cm × of Lecythis genus, namely, L. ollaria and L. curra- 10–17.5 cm), the seeds being oblong of 4.5–7 cm × nii, can be pressed to obtain edible oils with a high 2–3 cm. The fruits are used as antidiarrheal medi- content of unsaturated fatty acids. For example, cine and are delivered by the Kuna Indians [3]. Brazil nuts contain ω-3 fatty acid (α-linolenic acid) For certain birds, these trees are very important in a portion of approximately 70 % of total lipids. as a shelter and food. Moreover, the seeds of Here, half of it is oleic acid, followed by 25 %
Andrés Felipe Alzate Arbeláez, Benjamín Rojano, Food Science Laboratory, School of Chemistry, Faculty of Science, National University of Colombia, Street 59A # 63-20, 050034 Medellín, Colombia. Álvaro Cogollo Pacheco, Botanical Garden “Joaquín Antonio Uribe”, Street 73 # 51d-14, 050010 Medellín, Colombia. Correspondence author: Benjamín Rojano, e-mail: [email protected]
© 2018 National Agricultural and Food Centre (Slovakia) 87 Alzate Arbeláez, A. F. – Cogollo Pacheco, Á. – Rojano, B. J. Food Nutr. Res., Vol. 57, 2018, pp. 87–97 polyunsaturated lipids (linoleic acid, ω-6), and ap- tivars grown in the area of Urabá, department of proximately 19 % saturated fat such as palmitic Antioquia, Colombia, cultivated from January to and stearic acids [6, 7]. May 2017. A voucher specimen was left at Botani- However, the processing and incorporation of cal Garden “Joaquín Antonio Uribe”, Medellín, oils in food matrices, specifically the highly unsatu- Colombia (voucher number 2330). The seeds were rated oils, generates oxidative deterioration and selected in the best condition of maturity, which affects the organoleptic characteristics and shelf was indicated by spontaneous opening of the fruit life. Therefore, it is necessary to conduct studies shell. These were washed and dried at room tem- on the thermal and oxidative stability of oils [8]. perature and then stored at 4 °C in sealed polypro- Differential scanning calorimetry (DSC) is pylene bags until analysis. a thermal analysis technique employed in the measurement of temperatures and heat flows Oil extraction associated with many physical and chemical pro The oil was obtained by cold pressing the perties of oils. Furthermore, DSC thermal pro- almonds with a manual mill (Piteba, Schiedam, file provides information on oxidative stability of Holland), controlling the pressing temperature at various fats and oils [9]. Thermogravimetric analy- 45 °C. The oil obtained was filtered through a me- sis (TGA) is an important parameter on the stabil- tallic sieve (opening 1.00 mm, 18 mesh) and centri- ity of edible oils, providing information about the fuged at room temperature at 4 000 ×g for 15 min overall compositional change of the sample [10]. (centrifuge Z206A; Hermle, Wehingen, Germany) To inhibit oxidative deterioration, the oils are and then stored in an amber glass at –18 °C. The supplemented with natural or synthetic antioxi- acid, saponification and iodine numbers were de- dants, which retard rancidity by trapping free termined according to the methods recommended radicals generated by reactive oxygen species. by the American Oil Chemists’ Society (AOCS): The synthetic antioxidant 2,6-di-tert-butyl-4-hy- AOCS Cd 3d, AOCS Cd 1-25 and AOCS Cd 3-25, droxytoluene (BHT) is the most used in food ma- respectively [12]. trices rich in polyunsaturated fatty acids, used at a recommended content of 100 mg·kg-1 to avoid Composition of oil harmful effects on human health [11]. Fatty acids The aim of this research was to study compo- To determine the fatty acid profile of oil, sition, antioxidant activity and thermal as well as a gas chromatograph 6890N GC coupled to oxidative stability of oil extracted from L. tuyrana a 5973N MS selective detector and equipped with seeds, for the first time, as a new source of oil with a split/splitless injector (Agilent Technologies, high nutritional value and potencially beneficial to Santa Clara, California, USA) was used. The in- human health. jector temperature was (300 ± 1) ˚C. Samples were processed by adding 1 ml 0.5 mol·l-1 potas- sium hydroxide in methanol to 50 mg of sample in Materials and methods 1 ml n-hexane and subsequent vigorous shaking for 60 s, then neutralized with 1 mol·l-1 HCl and Materials centrifuged. The upper n-hexane layer contain- The oil was obtained as described further. ing fatty acids methyl esters (FAME) was col- Fluorescein, 2,4,6-tripyridyl-s-triazine (TPTZ), lected, filtered and automatically injected (3.0 µl) 2,2-diphenyl-2-picrylhydrazyl free radical to the chromatograph in the splitless mode. (DPPH•), gallic acid, 6-hydroxy-2,5,7,8-tetrame An HP-5 MS (5.0 % phenylmethylsiloxane) 30 m, thylchroman-2-carboxylic acid (Trolox), β-caro 0.25 mm column, (Agilent Technologies), 0.25 μm tene, thiobarbituric acid, methyl-β-cyclodextrin film thickness, and a maximum temperature of and α-tocopherol were purchased from Sigma- 325 ˚C were used. The database NIST 98 (Na Aldrich (St. Louis, Missouri, USA). Methanol, tional Institute of Standards and Technology, ethanol, n-hexane, butanol, acetone, dichlo- Gaithersburg, Maryland, USA) was used to iden- romethane, Folin-Ciocalteu reagent, sodium car- tify fatty acids [13]. The quantity of fatty acids was bonate and trichloroacetic acid (analytical grade) expressed as grams of fatty acid per kilogram of were purchased from Merck (Darmstadt, Germa- oil. ny). Ethyl ether, chloroform and octane, were pur- chased from Carlo Erba (Cornaredo, Italy). Total carotenoids Quantification of total carotenes was carried Plant material out as described by Biswas et al. [14]. A sample Almonds were obtained from L. tuyrana cul- of 100 mg was taken into a test tube, to which
88 Stability of Lecythis tuyrana oil
4 ml of cold acetone were added and, after stir- pressed as milligrams of tocopherols per kilogram ring vigorously for 120 s, it was allowed to stand of crude oil. 15 min at 4 °C. Then, it was centrifuged at 4 000 ×g for 10 min and the supernatant was transferred Antioxidant activity of oil to another test tube. The above procedure was Oxygen radical-absorbance capacity repeated until the sample was exhausted. Final- The oxygen radical-absorbance capacity ly, both of the acetone extracts were combined (ORAC) assay was carried out using the follow- and filtered. The absorbance of the solution at ing methodology. A volume of 3 ml of the follow- 449 nm was determined, using acetone as blank, ing solution was prepared: 21 µl of a 10 µmol·l-1 in a spectrophotometer UV/Vis Multiskan Spec- solution of fluorescein, 2 899 µl of 75 mmol·l-1 trum (Thermo Scientific, Waltham, Massachusetts, phosphate buffer (pH 7.4), 50 µl of 600 mmol·l-1 USA). Results were expressed as milligrams of 2,2’-azobis(2-amidinopropane) dihydrochloride β-carotene per kilogram of crude oil, using a cali- (AAPH) and 30 µl of oil, which was dissolved in bration curve with β-carotene standard. a 70 g·l-1 solution of methyl-β-cyclodextrin. Fluo- rescence was recorded on a spectrofluorometer Total polyphenols with a thermostated multicell (model LS55; Per- The total polyphenols content was determined kin Elmer, Waltham, Massachusetts, USA). The by the adapted Folin-Ciocalteu assay. Briefly, ORAC value was calculated from a calibration 10 g of oil were extracted with 150 ml of metha- curve using Trolox as an antioxidant standard and nol in a separation funnel and, when the phases expressed as micromoles of Trolox equivalents separated, the methanolic layer was centrifuged (TE) per kilogram of oil [17]. at 4 000 ×g for 15 min. The remaining oil was removed and the solution was distilled under re- DPPH radical-scavenging activity duced pressure. The extract obtained was mixed DPPH radical-scavenging assay described by with Folin-Ciocalteu reagent and sodium carbon- Lee et al. [18] was used with some modifications. ate solution (71 g·kg-1). The mixture was stirred This procedure was performed using 10 μl of the and stored at room temperature for 0.5 h in extract and 990 μl of the DPPH radical, in octane the darkness. The absorbance was measured at solution (20 mg·l-1). After 0.5 h of reaction at 760 nm against a blank containing only Folin-Cio room temperature in the dark, the absorbance was calteu reagent, methanol and sodium carbonate. read at 517 nm. For each studied sample, the per- A standard calibration curve of gallic acid was used centage inhibition of the radical concentration was and results were expressed as milligrams of gallic calculated and the results were expressed as milli acid equivalent per kilogram of crude oil [15]. moles of BHT equivalents per kilogram of oil, by the construction of a calibration curve using BHT Determination of vitamin E as a standard. The content of vitamin E (α-tocopherol) was determined by high-performance liquid chro- Oxidative stability of oil matography (HPLC), according to the modified Using freshly extracted oil, the oxidative protocol of Gliszczyńska-Świgło et al. [16]. quality indices peroxide value (PV), thiobarbituric An aliquot of the oil was diluted in the mobile acid reactive substances value (TBARS), total po- phase, filtered through a membrane filter (pore lar compounds (TPC) and oxidative stability index size 0.20 µm) and then injected into the chro- (OSI) were determined. The effect of the antioxi- matograph. An LC-20AD liquid chromatograph dant BHT to increase the useful life of the oil (oxi- (Shimadzu, Tokyo, Japan) was used, equipped dative stability) was measured by the active oxygen with a SIL-20A auto injector/HT, a communica- method (AOM). tion module CBM-20A and diode array detector (PDA) at a wavelength of 295 nm. Quantification Peroxide value of vitamin E was conducted on a LiChrospher Peroxide value (PV) was determined by the RP-18 column (250 mm × 4.5 mm, particle International Dairy Federation (IDF) method size 5 mm; Merck). A mixture of methanol and [19]. This method is based on the ability of lipid dichloromethane (85 : 15, v/v) was used as a mo- peroxide to oxidize Fe2+ to Fe3+. A volume of bile phase. The flow rate of the mobile phase 3.5 ml of a mixture of chloroform and metha- was 0.8 ml·min-1, column temperature was kept nol (7 : 3) was stirred for 10 s and, subsequent- at 35 °C and isocratic flow conditions were used. ly, 50 µl of a solution of FeSO4 (0.144 mol·l-1), Concentration of α-tocopherol was calculated BaCl2 in HCl (0.4 mol·l-1) and 50 μl of a solution from the calibration curve and results were ex- of NH4SCN (0.44 mol·l-1) were added to 1 ml of
89 Alzate Arbeláez, A. F. – Cogollo Pacheco, Á. – Rojano, B. J. Food Nutr. Res., Vol. 57, 2018, pp. 87–97 the above solution. This mixture was incubated for with 20 ml hexane : ethyl ether (90 : 10, v/v), the a period of 20 min in darkness and, after this time, solvent was passed through while the sample was absorbance was determined at a wavelength of retained on the column. The second fraction (con- 510 nm. Results were expressed as milliequivalents taining TPC) was eluted with 20 ml diethyl ether. of oxygen per kilogram of oil. The efficiency of separation by silica cartridges was checked by thin layer chromatography (plates Anisidine value of Silica Gel 60; 5 cm × 10 cm, 0.25 mm thick- Anisidine value (AV), which quantifies alde- ness; Merck) using n-hexane : diethyl ether : acetic hydes as final degradation products, was deter- acid (80 : 20 : 1 v/v/v) for plate development. Dried mined according to IUPAC 2504 standard [20]. plates were exposed to iodine vapor to visualize The oil samples, dissolved in octane, were allowed the separation of two fractions. Solvents were re- to react with p-anisidine solution in acetic acid moved at reduced pressure in a rotary evaporator (2.50 g·l-1) for 10 min at room temperature. The and both fractions were weighed. The results were absorbance of the resulting coloured complex was expressed as grams of polar compounds per kilo- measured at 350 nm and results were expressed gram of oil. according to Eq. 1. (1.2 ) Oxidative stability index = 1.25 × (1) Oxidative stability index (OSI) was evalu- 𝐴𝐴1 − 𝐴𝐴2 ated by Rancimat model 679 (Metrohm, Herisau, 𝐴𝐴𝐴𝐴A A Switzerland) following AOCS Official Method where 1 is the sample𝑚𝑚 absorbance, 2 the absor- bance of the blank and m is weight of sample (ex- Cd 12b-92 [12]. Oil (2.5 g) was heated to a tem- pressed in grams). perature of 120 °C and oxidized by bubbling air through the sample (20 l·h-1). Volatile secondary Total oxidation value products from lipid oxidation were carried by the The total oxidation value (TV) was calculated air into a tube with distilled water, where con- through Eq. 2 [21]. ductivity was monitored. OSI is the time until the maximum rate of conductivity increase is achieved. = 2 + (2)
𝑇𝑇𝑇𝑇 𝑃𝑃𝑃𝑃 𝐴𝐴𝐴𝐴 Active oxygen method Thiobarbituric acid reactive substances The AOM method was performed according to The end product of lipid peroxidation, malon Anwar et al. [23]. A volume of 30 ml of oil was aldehyde (MDA), reacts with 2-thiobarbituric acid supplemented with BHT at 100 mg·l-1, which is (TBA) to produce a fluorescent complex that can a concentration accepted by Food and Agriculture be measured at 500 nm excitation and 520 nm Organization (FAO) [11]. In addition, a control emission wavelengths. The fluorescence was read sample was used. The test was conducted under by an LS-55 spectrofluorometer. Volumes of accelerated conditions (100 °C ± 1 °C with an air 80 µl of trichloroacetic acid (TCA, 10 g·l-1) and flow of 1 150 ml·min-1), until a time in which PV of 160 µl of TBA (60 g·l-1) were added to 500 µl of 100 meq·kg-1 oil was reached. oil. This mixture was incubated for a period of 20 min at 90 °C and then submerged to cold wa- Thermal stability of oil ter for 10 min. After this period, 600 µl of butanol Differential scanning calorimetry was added to it. The sample was stirred and the A sample of 5.0 mg of oil was submitted to respective measurements were taken. TBA reac- heating at a constant rate of 10 °C·min-1 from tive substances values (TBARS) were expressed room temperature to 500 °C with a flow of air of as millimoles of malondialdehyde per kilogram of 40 ml·min-1. Heat fluxes were measured on Q20 crude oil using a calibration curve with MDA as instrument (TA Instruments, New Castle, Dela- a standard [22]. ware, USA).
Total polar compounds Thermogravimetric analysis The content of total polar compounds (TPC) The thermal stability of the oil was evaluated was determined according to IUPAC 2507 by thermogravimetry on a thermogravimetric standard [20]. Polar and non-polar fractions were analyser Q50 (TA Instruments) by heating the separated from 100 mg of oil dissolved in 2 ml of crude oil sample in air, from 100 °C to 800 °C at n-hexane using silica cartridge for solid-phase ex- a rate of 20 °C·min-1. The Platinum Software traction (Sep-pak; Waters, Milford, Massachu- (TA Instruments) was used to export and analyse setts, USA). The non-polar fraction was eluted graphical and numerical data.
90 Stability of Lecythis tuyrana oil
A
B C
Fig. 1. Photographs of Lecythis tuyrana fruits. A – whole fruit, B – fruit interior, C – almonds.
Statistical analysis as total polyphenols, with antioxidant charac All experiments were carried out over tripli- teristics in the Lecythis oil seeds, were quantified cate samples and their mean values were reported. in the polar extract of oil and were found at a level Software Statgraphics Centurion XVI (Statpoint of 62.20 ± 3.50 mg·kg-1 oil, expressed as gallic acid Technologies, The Plains, Virginia, USA) was used equivalent. for statistical analysis. In the lipophilic phase of oilseeds, total carotenoids were found to be present at 3.00 ± 0.10 mg·kg-1 of oil (expressed as β-carotene Results equivalent). In general, very low amounts were found in Lecythis almond oils, lower values Fig. 1 shows three photographs of the fruits of have been reported in oilseeds and other L. tuyrana used in this research. The fruits reach nuts such as Pistacia vera. Carotenoids (of the a size of almost 18 cm of diameter, and a height type of β-carotene) and lutein were found at near 15 cm. The whole fruit inside has three com- 4.0–10.0 mg·kg-1 and 15.0–96.0 mg·kg-1 of oil, res partments where the seeds are found, can contain pectively [27]. α-Tocopherol in L. tuyrana oil was up to 18 almonds, which have brown testa. To ob- found in a content of 32.20 ± 0.40 mg·kg-1 oil, tain the oil, this layer was removed. which was similar to data reported by Bolling In almonds of L. tuyrana, a lipid content of et al. for pecan (Carya illinoinensis) and the Brazil 732.0 ± 27.1 g·kg-1 was found. The extracted nut (Bertholletia excelsa) [28]. oil had an acid value of 2.70 ± 0.30 g·kg-1 (ex- Fig. 2 shows the fatty acid profile of L. tuyra- pressed as oleic acid), saponification value na oil, with a high content of oleic acid (ω-9) 194.70 ± 14.54 g·kg-1 oil (expressed as KOH), io- 369.0 g·kg-1, linoleic acid (ω-6) 272.0 g·kg-1, pal- dine value 64.02 ± 4.73 g·kg-1 oil (expressed as mitic acid 171.0 g·kg-1, stearic acid 149.0 g·kg-1 I2 equivalent). These results are similar to those and, to a lesser extent, unsaturated acids like ar- reported for other seeds in the Lecythis genus achidonic acid (ω-6) 10.0 g·kg-1, palmitoleic acid [24–26]. Hydrophilic secondary metabolites, such (ω-7) 7.0 g·kg-1, and very low amounts of satu-
91 Alzate Arbeláez, A. F. – Cogollo Pacheco, Á. – Rojano, B. J. Food Nutr. Res., Vol. 57, 2018, pp. 87–97
11 6 9 3 5
] 7 6 0 1
× 7 [
c e n
a 5 d n u
b 3 A
1 2 8 1 4 9 5 10 15 20 25 30 35 40 45 50 Retention time [min] Fig. 2. Analysis of fatty acids methyl esters from Lecythis tuyrana oil. Chromatogram was obtained by gas chromatography – mass spectrometry. The y-axis represents total ion counts. Retention: 1 – myristic acid (19.538 min), 2 – palmitoleic acid (ω-7, 23.734 min), 3 – palmitic acid (24.376 min), 4 – behenic acid (27.053 min); 5 – linoleic acid (ω-6, 29.050 min), 6 – oleic acid (ω-9, 29.264 min), 7 – stearic acid (29.924 min), 8 – arachidonic acid (ω-6. 35.351 min), 9 – margaric acid (43.348 min).
rated fatty acids, such as myristic acid 3.0 g·kg-1, oil (expressed as BHT), which is similar to the behenic acid 2.0 g·kg-1 or margaric acid 1.0 g·kg-1. values for olive oil (15.425 mmol·kg-1), greater The antioxidant activity evaluated by free ra than canola oil (7.19 mmol·kg-1) and less than dical-scavenging assays is a mechanism of hydro- the soybean oil (18.365 mmol·kg-1) [18]. Low gen atom transfer (HAT) and, for L. tuyrana oil, values of PV (3.64 ± 0.45 meq·kg-1) and TBARS it was evaluated by the capacity of trapping (2.69 ± 0.21 μmol·kg-1) were determined for peroxyl radical (ROO•) by ORAC method with L. tuyrana oil. a result of 3641 ± 323 µmol·kg-1 (expressed as TE). This value falls within a range determined Oxidative and thermal stability by Ninfali et al. [29] with 33 olive oils from Oxidative stability of oils determined as OSI various regions of Italy and Spain, while phe- is completely dependent on the temperature and nol and tocopherol values were similar to those oxygen flow used. In this case, due to the oil com- for Lecythis oil. Another important test to trap position, a temperature of 120 °C with an air flux free radicals (DPPH•) implemented in recent of 20 l·h-1 was used, and an OSI value was 3.47 h years is a lipophilic DPPH assay to determine (Fig. 3). oxidative stability of oils and fats. In Lecythis oil, The AOM method facilitates characterization the obtained result was 14.70 ± 0.50 mmol·kg-1 of oil regarding degradation kinetics, under ac-
20 150 3.47 h without BHT ] 1 ] - with BHT 1 - 15 k g m c · e q · 100 m [ µ S [
y u e
i t 10 i v t v a l c
d e 50 n d u o x i o 5 C e r P
0 0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4. 0 1 4 7 10 13 16 19 22 25 Time [h] Time [h] Fig. 3. Time course of conductivity Fig. 4. Formation of peroxides in Lecythis tuyrana oil of Lecythis tuyrana oil at temperature of 120 °C supplemented with and without butylhydroxytoluene. -1 with air flux of 20 l·h . BHT – butylhydroxytoluene (100 mg·l-1).
92 Stability of Lecythis tuyrana oil celerated conditions. PV is used to indicate pri- 100 mary oxidative deterioration of fats and oils. The TG PV measurements were performed over time until 80 DTG reaching 100 meq·kg-1 (accepted as the total oxi- ] % dative rancidity of an oil). Eq. 3 and Eq. 4 show [ 60 the kinetic model for the control (oil without an- t i g h tioxidant) and for oil supplemented with BHT 100 e 40 W mg·l-1, respectively. 20 = e( . . ); = 94.0 % (3) = e(11. 2338 + 0.849749𝑡𝑡); 2 = 96.6 % (4) 𝑃𝑃𝑃𝑃 𝑅𝑅 0 6 78086 + 0 479106𝑡𝑡 2 0 100 200 300 400 500 600 700 800 where𝑃𝑃𝑃𝑃 t is time in hours. 𝑅𝑅 Temperature [°C] The model to reach 100 meq·kg-1 was an expo- Fig. 5. Thermogravimetric analysis nential type model, and its findings were PV values for crude Lecythis tuyrana oil. of 18.64 h for the control and 23.77 h for the sam- TG – curve of weight loss, DTG – first derivative of TG curve. ple with BHT. These results showed that BHT can inhibit the oxidative process of L. tuyrana oil by 27.5 % at a temperature of 100 °C (Fig. 4). 3000 Fig. 5 shows the results of TGA for Lecythis oil. Thermal degradation started when the oil tem ]
- 1 2500 g perature was of approximately 200 °C and the mass · W
loss became continuous up to 550 °C, being very m [ 2000 significant at 340 °C. Similar results were reported w f l o for vegetable oils and it was suggested that a con- t a tinuous breaking of the hydrocarbon chains in H e 1500 molecules, such as carbon dioxide and monoxide, volatilize carbon easily. This is favoured by the proportion of unsaturated fatty acids in Lecythis 0 0 100 200 300 400 500 oil, which is 64 % [30]. Further mass loss occurs at Temperature [°C] 420 °C and 530 °C due to degradation of saturated Differential scanning calorimetry fatty acids and polymers formed during the final Fig. 6. for Lecythis tuyrana oil. stages of peroxidation [31]. Results of DSC assay are shown in Fig. 6. An increase in the heat flux, characteristic of exother- mic reactions, can be seen above 200 °C. mono-unsaturated fatty acid (MUFA) most com- monly used in Western diet and is present in most Discussion oils of animal or plant origin. Also, oleic acid is an indicator of quality of oils for culinary use, such Lipids belong to main nutrients of the human as olive, sunflower and canola oil. It has multiple diet, and they are of great importance for con health benefits, including a decrease of the risk of sumers and food industry. Seed oils constitute heart disease by 20–40 %, primarily through the a significant part of the typical human diet because reduction of low density lipoproteins (LDL) cho- they are a source of essential nutrients such as lesterol. Beneficial effects on cerebrovascular risk fatty acids, tocopherols and phytosterols. Health factors, such as thrombogenesis, and on insulin conscious consumers require from the industry sensitivity were reported [32–34]. to provide oilseeds and oils which are rich in be The linoleic acid content is similar to that re- neficial compounds including ω-3, ω-6, ω-9 fatty ported for Lecythis pisonis [26], higher than olive acids, tocopherols, carotenoids and polyphenols. and soybean oil [35], and lower than those re- In L. tuyrana oil, mainly 9 fatty acids are found, ported for some types of sunflower and canola with carbon chains from 14 to 22 carbon atoms, oils [37, 37]. Linoleic acid is an essential fatty acid with a ratio of percentage of saturated and unsatu- with many health effects like the ability to inhibit rated (I/S) of 2.0 %. This index shows a high pro- proliferation of colorectal cancer and decrease portion of unsaturated fatty acids, and oleic and growth of atherosclerotic plaque [38]. Palmitoleic linoleic acids as key components. Oleic acid is the acid, which is a ω-7, a minor fatty acid, known for
93 Alzate Arbeláez, A. F. – Cogollo Pacheco, Á. – Rojano, B. J. Food Nutr. Res., Vol. 57, 2018, pp. 87–97 its beneficial action on the skin and mucous mem- containing 370 g·kg-1 oleic acid and 270 g·kg-1 li branes [39]. noleic acid, which suggests a poor thermal stabil- Content of vitamin E in L. tuyrana almonds ity in frying processes where temperatures reach and oil was similar to other massively commer 180–200 °C. Tests of TGA and DSC type, com- cialized nuts. An increase in the consumption of monly used in the industry of fats and oils, were this type of products is beneficial for health due done to confirm the thermostability. These assays to an important role in protection of polyunsatu- characterize the phenomena of decomposition, rated fatty acids (PUFA) and other components sublimation, reduction, oxidation and adsorption of cell membranes, as well as protection of LDL or desorption of gases or vapours, being a function from oxidation by free radicals. Vitamin E is the of temperature change, thermal reactivity, initial main lipid-soluble antioxidant in the cellular anti- temperature, final combustion (in the case of fuel oxidant defense system and is retrieved exclusively oil) and degradation rate [43, 44]. from the diet. Its consumption must be such as to DSC is a technique used to measure heat fluxes ensure a 2.25-times higher plasma concentration in respect to temperature changes associated with than that of cholesterol [40]. phase transitions or chemical reactions such as The oxidative stability of oil is determined by oxidation or hydrolysis. This technique was used the relationship between saturated fatty acids, un- to determine the thermal profile of the oil, the saturated fatty acids and secondary metabolites results of this process being reactions associated present, and it is reflected by its antioxidant ac- with formation of degradation products, such as tivity, specifically those measurable by lipophilic peroxides or polar compounds, commonly formed methodologies. ORAC and DPPH values deter- in lipidic matrices due to the effects of diffusion of mine the antioxidant potential of a food product, oxygen reached in the dynamic process of heating with protective properties on many systems such and aeration of the sample [45, 46]. as lipid membranes and cell wall. Lecythis oil has To retard the oxidative deterioration of oils values similar to many oils reported with benefi- caused by radical oxygen species, antioxidants cial health effects, such as olive and canola oils. are used, which reduce the oxidation process The oxidation quality of the freshly extracted and improve the organoleptic quality of the final oil is characterized by PV (3.64 meq·kg-1), which product. Antioxidants in food determine shelf registers the initial and intermediate products of life and reduce nutritional losses. However, they lipid peroxidation. TBARS value (2.69 μmol·kg-1) never improve or regenerate the quality of a highly and TPC (60.0 g·kg-1) are associated with the oxidized food product. Antioxidants to be used presence of final oxidation compounds. In addi- in food must meet certain requirements such as tion, TV of 3.54 shows that the oil did not suffer being odourless, tasteless, effective at low con- oxidative deterioration in the extractive pro- tents, easy to incorporate, supporting processing cess and its natural antioxidant ingredients were conditions and stable in the finished product [47]. protected. These values are a particularly cha The oxidation process of Lecythis oil under racteristic for each oil and they are indicators of accelerated conditions (100 ± 1 ° C with an air flow its potential shelf life. The values found for each of 1 150 ml·min-1) was reduced by 27.5 % using of the oxidative stages reflected a high stability of BHT as an antioxidant at 100 mg·l-1. Therefore, Lecythis oil. we were able to obtain a stabilized oil with high OSI of oils and fats determined by the Ranci- nutraceutical and functional potential that allows mat assay is based on the induction time of oxida- its use in food. In addition, research is under way tion of the sample by exposure to elevated tem on the use of natural antioxidants with a greater peratures and air flow in accelerated conditions. efficiency than BHT. The result for Lecythis oil (OSI of 3.47 h) is com- parable to those reported for maize oil and cotton- seed oil [41]. OSI is a fundamental tool in techno Conclusions logy assessment, quality and shelf life of oils and fats, which facilitates evaluation and optimization L. tuyrana oil obtained by pressing is a source of stabilization strategies for oils and fats by anti- of unsaturated fatty acids such as oleic acid oxidant compounds [42]. (369.0 g·kg-1) and linoleic acid (272.0 g·kg-1), The thermal stability of crude vegetable oils which are stabilized by carotenoids, lipophilic an- obtained by cold extraction processes is an indica- tioxidants (3.00 ± 0.10 mg·kg-1 β-carotene) and tor of quality for its use in different food matrices tocopherols (32.20 mg·kg-1). This proposal is or cosmetics. Lecythis oil is characterized by a high supported by oxidative stability values, namely, proportion of unsaturated fatty acids (I/S = 2.02) TBARS, PV and TV and, finally, by the low TPC
94 Stability of Lecythis tuyrana oil value. The oil was found very stable compared to 8. Rudnik, E. – Szczucinska, A. – Gwardiak, H. – many other newly extracted oils. TGA, DSC and Szulc, A. – Winiarska, A.: Comparative studies of OSI assays also demonstrated thermal stability oxidative stability of linseed oil. Thermochimica for the oil, which, although not stabilized by addi- Acta, 370, 2001, pp. 135–140. DOI: 10.1016/S0040- 6031(00)00781-4. tives, did not show thermal decomposition below 9. Saldaña, M. D. A. – Martínez-Monteagudo, S. I.: 200 °C. However, the high presence of unsaturated Oxidative stability of fats and oils measured by fatty acids (close to 64.0 %) can cause significant differential scanning calorimetry for food and oxidative damage. Lecythis oil is a novel oil with industrial applications. In: Elkordy, A. A. (Ed.): interesting nutraceutical properties, which is pro- Applications of calorimetry in a wide context – posed to be used as an ingredient in fresh prepa- Differential scanning calorimetry, isothermal titra- rations, conventional frying, vacuum frying and tion calorimetry and microcalorimetry. Sunderland : baking processes. InTech Open Access Publisher, 2013, pp. 445–474. ISBN: 9789535109471. DOI: 10.5772/54486. 10. Santos, J. C. O. – Santos, I. M. G. – Conceiçă o, M. M. – Acknowledgements Porto, S. L. – Trindade, M. F. S. – Souza, A. G. – Pra The authors appreciate the support and assistance sad, S. – Fernandes Jr., V. J. – Araújo, A. S.: Thermo given by the Research Office and Faculty of Science at analytical, kinetic and rheological parameters of National University of Colombia (Medellin, Colombia) commercial edible vegetable oils. Journal of Ther and Botanical Garden “Joaquín A. Uribe” (Medellín, mal Analysis and Calorimetry, 75, 2014, pp. 419–428. Colombia) throughout this study. DOI: 10.1023/B:JTAN.0000027128.62480.db. 11. Report of the seventeenth session of the Joint FAO/WHO Codex Alimentarius Commission, References Rome, 29 June – 10 July 1987. FAO/WHO Codex Alimentarius Commission. Sess. 17. Rome : FAO/ 1. Mori, S. – Prance, G.: Lecythidaceae, Part 2: The zygo- WHO Codex Alimentarius Commission, 1987. morphic–flowered New World genera (Couroupita, ISBN: 9251026149.
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