Aleksandra Szydłowska-Czerniak

Determination of antioxidant capacities of vegetable oils by ferric-ion spectrophotometric methods

Two ferric-ion-based total antioxidant capacity methods: 1,10-phenanthroline (Phen) and ferric reducing antioxidant power (FRAP) were used for determination of antioxidant capacities (AC) of the acetonic and methanolic extracts of vegetable oils. The obtained mean Phen and FRAP values for acetonic extracts of olive oils, rapeseed, rice and four sunflower oils (39.3-336.5 and 39.5-339.6 micromol Fe/100g) were higher than for methanolic extracts (22.8-307.3 and 23.5-300.1 micromol Fe/100g). However, antioxidant capacities of methanolic extracts of corn oil, blended oils and two sunflower oils with garden green flowers (56.5-312.9 and 53.9-306.5 micromol Fe/100g for Phen and FRAP methods, respectively) were higher than for acetonic extracts of these oils (54.2-249.2 and 52.9-244.7 micromol Fe/100g for Phen and FRAP methods, respectively). There is a linear and significant correlation between these two analytical methods (r=0.9989 and 0.9986 for acetonic and methanolic extracts). Also, total phenolic compounds (TPC) in the studied oils correlated with their antioxidant capacities determined by Phen and FRAP methods (r=0.9012, 0.7818 and 0.8947, 0.7830 for acetonic and methanolic extracts, respectively). The comparable precision (R.S.D.=0.8-4.6%, 0.9-4.9% and 0.7-4.0%, 0.6-4.0% for acetonic and methanolic extracts, respectively) and sensitivity (epsilon=1.27 x 10(4), 1.11 x 10(4) and 2.62 x 10(4)dm(3)mol(-1)cm(-1)) for the proposed Phen and the modified FRAP methods, demonstrate the benefit of the Phen method in the routine analysis of antioxidant capacities of vegetable oils.

Effect of refining processes on antioxidant capacity, total contents of phenolics and carotenoids in palm oils

Antioxidant capacity (AC), total phenolic content (TPC) and total carotenoid content (TCC) in palm oils at various stages of the refining process from two technological modes were determined. The obtained mean FRAP and DPPH values for the methanolic extracts of palm oils from mode 1 (19.5-102.8μmol TE/100g and 18.8-103.0μmol TE/100g) were lower than for oils from mode 2 (25.6-134.8μmol TE/100g and 25.4-135.4μmol TE/100g). The total phenolics (4.1-12.4mg GA/100g) and carotenoids (0.18-45.8mg/100g) in the studied oils were correlated with their antioxidant capacities determined by FRAP and DPPH methods (r=0.6623-0.9878). During the refining process, for both technological modes resulted in a loss of AC by 80%, TPC by 26-55% and TCC by 99%. The bleaching step caused the highest losses of AC as determined by FRAP 41% and 46%, DPPH by 43% and 48%, while TPC loss was 45% and 23% and loss of carotenoids was 49% and 56%, in mode 1 and mode 2, respectively.

Spectrophotometric determination of total phosphorus in rape seeds and oils at various stages of technological process: calculation of phospholipids and non-hydratable phospholipids contents in rapeseed oil

Abstract A new spectrophotometric method for determination of total phosphorus in rape seeds and rapeseed oils is described. The procedure is based on formation of the ionic—associate of molybdophosphate with Malachite Green (MG) in an acidic medium and compared with the standard vanadomolybdate and molybdenum blue methods. Satisfactory values of recovery ranged between 99.1–100.3% and RSD

Rapeseed and its Products—Sources of Bioactive Compounds: A Review of their Characteristics and Analysis

Extensive studies of rapeseed varieties, meals and rapeseed oils revealed that they are rich sources of natural components having antioxidant properties. In this review the characteristic of bioactive compounds in rapeseed cultivars, meals and oils will be presented. The analytical methods of antioxidants identification and determination are described. The effects of innovations in rapeseed modification and technology improvements on antioxidant capacity of rapeseed oil and products will be discussed.

Development of a novel gold nanoparticle-based method to determine antioxidant capacity of Brassica oilseeds, white flakes and meal

Antioxidant capacity (AC) of Brassica oilseeds, white flakes and meal was determined by a new spectrophotometric method. The proposed assay (AuNP) based on the formation of gold nanoparticles (AuNPs) in an acetic buffer medium (pH=4.6) was compared with the previously described silver nanoparticle-based (AgNP), ferric reducing antioxidant power (FRAP), 2,2-diphenyl-1-picrylhydrazyl (DPPH) and Folin-Ciocalteu (FC) procedures. The novel AuNP method was validated using standard antioxidants such as phenolic acids and quercetin. The AC of rapeseed, white flakes and meal varied from 10.0 to 86.7μmolsinapicacid(SA)/g, 26.5-160.3μmolSA/g, 6.8-103.0μmolSA/g, 23.0-259.3μmolSA/g and 6.9-92.1μmolSA/g for AuNP, AgNP, FRAP, DPPH and FC methods, respectively. The proposed AuNP method is simple, precise (intra-day RSD=0.27-2.11% and inter-day RSD=2.05-4.87%) and accurate (recovery=96.2-104.3%) and can be useful in the routine analysis of the AC.

Spectroscopic Determination of Metals in Palm Oils from Different Stages of the Technological Process

Magnesium, calcium, copper, iron, and lead in palm oils ( Elaeis guineensis ) at various stages of the refining process were determined by inductively coupled plasma mass spectrometry (ICP-MS) after microwave digestion. The mean concentrations of Mg, Ca, Cu, Fe, and Pb in the studied palm oils varied from 20.7 to 7090.1 μg kg(-1), from 193.9 to 8077.9 μg kg(-1), from 29.7 to 463.0 μg kg(-1), from 115.2 to 415.9 μg kg(-1), and from 1.7 to 16.0 μg kg(-1), respectively, which are below the Polish legal requirements. The comparable precisions for the proposed ICP-MS (RSD = 0.81-5.99%) and standard GFAAS (RSD = 1.18-5.26%) methods demonstrate the benefit of the ICP-MS method in the routine analysis of metal ions in palm oils. There are significant, positive correlations between Ca and Mg, between Ca and Cu, between Fe and Pb, between Cu and Fe, between Cu and Mg, and between Cu and Pb in palm oils determined by two analytical methods (r = 0.8798-0.9817, p < 0.05). Principal component analysis (PCA) and hierarchical cluster analysis (HCA) were used for discrimination of the quality of the analyzed palm oils based on main and trace metal contents determined by the proposed ICP-MS and the standard GFAAS methods. Two main groups were identified by HCA, whereas the classification and characterization of the studied palm oils within each of groups on the basis of metal ions amounts were obtained from PCA. The chemometric analyses demonstrated that crude palm oil had the highest level of the determined metals concentrations. Also, the analyzed metals in palm oils from different steps of the refining process were grouped using HCA to assess the effectiveness of technological processes for their removal.

A novel iron oxide nanoparticle-based method for the determination of the antioxidant capacity of rapeseed oils at various stages of the refining process

A novel iron oxide nanoparticle-based (IONP) method and two modified methods: ferric reducing antioxidant power (FRAP) and 2,2′-diphenyl-1-picrylhydrazyl (DPPH) were used for the determination of the antioxidant capacities of the acetonic, ethanolic and methanolic extracts of rapeseed oils from different stages of technological processes. The IONP method based on the reduction of ferric ions by oil antioxidants in acidic medium and the formation of yellow solutions of iron oxide nanoparticles (IONPs) has been elaborated. The novel IONP method was validated using sinapic acid (SA), caffeic acid (CA), gallic acid (GA), ferulic acid (FA), vanillic acid (VA) and Trolox (TE) as standard antioxidant solutions. The average antioxidant capacities of the studied rapeseed oils ranged between 2594 and 4946 μmol SA/100 g for the proposed IONP method, 58–315 μmol SA/100 g for the FRAP method, and 462–1511 μmol SA/100 g for the DPPH assay. Satisfactory values of precision (RSD = 0.5–3.4%) demonstrate the benefit of the proposed IONP method for analysis of the antioxidant capacity of rapeseed oil samples.

Synthesis of novel octyl sinapate to enhance antioxidant capacity of rapeseed–linseed oil mixture

BACKGROUND Lipophilisation allows the formation of new functionalised antioxidants having beneficial properties compared to natural hydrophilic phenolic acids. Therefore, this work focused on the synthesis of lipophilic antioxidants, such as a new octyl sinapate, octyl caffeate and octyl ferulate using the modified Fischer esterification of selected hydroxycinnamic acids with 1-octanol. RESULTS The lipophilic octyl sinapate was obtained for the first time with satisfactory yield (83%) after purification by column chromatography. The identity of the synthesised phenolipids was confirmed by chromatographic and spectroscopic analyses. Antioxidant capacity of phenolipids was determined by DPPH (IC50  = 35.87-52.24 μg mL-1 ) and ABTS (IC50  = 39.45-48.72 μg mL-1 ) methods and compared with IC50 values (7.37-35.30 μg mL-1 and 7.55-41.67 μg mL-1 , respectively) for well known antioxidants. The antioxidant capacity of rapeseed-linseed oil enriched with the purified esters was about two to 30 times higher in comparison with a non-supplemented oil. CONCLUSION The novel octyl sinapate as well as octyl caffeate and octyl ferulate have antioxidant properties and lipophilic character, therefore they may be added to vegetable oils as potential antioxidants for tackling oxidative processes.