RESUMO
Fatty acids are present in many foods, either free or esterified. Their presence helps to characterize and classify the food. The nature of these fatty acids is also associated with the treatments applied. To assess the fatty acid profile of these matrices, extractions are carried out using different solvents that influence the nature and lipid profile. The subsequent derivatization of fatty acids to more volatile fatty acyl methyl esters (FAMEs) prior to determination of the fatty acid profile takes into account the nature of the extraction solvent. Thus, the present work proposes to determine the fatty acid profile by Gas Chromatography Flame Ionisation Detector (GC-FID) of two lipid extracts derivatized by the MeOH/KOH and Hexane/MeOH/MeOH-BF3 procedures. Freshly harvested Tetracarpidium conophorum nuts from fields in the Fombap locality were brought to the laboratory where they were boiled (95 °C; 30 min), shelled, cut into small cubes and dried for 48 h at 45 °C. The dried seeds were ground and the resulting paste macerated in hexane for 48 h. The liquid fraction obtained was concentrated using a rotavapor, and the lipid extracts were stored at -15 °C. The egusi pudding was obtained by mixing 100 g of egusi seed paste with 0.50 g of white Piper nigrum powders, then packed in bulrush leaves and steamed for 120 min. After cooking, the product was stored for 4 days at room temperature and reheated twice a day. At the end of the last day, the lipid fraction oil was extracted following the methodology of Bligh and Dyer [1], then concentrated and preserved as before. The lipid extracts were then methylated using MeOH/KOH and Hexane/MeOH/MeOH-BF3 methods before injection into a GC-FID equipped with a Stabil Wax®-DA column. Supelco's standard mix of 37 FAMEs was used to identify and quantify the fatty acids present in the various samples. The results obtained enable us to identify the different fatty acids according to the retention time of their corresponding FAMEs and to quantify them. The fatty acids obtained were classified as saturated and unsaturated (mono and polyunsaturated). These analyses showed that the rapid derivatization method (MeOH/KOH) identified the same number of fatty acids as the Hexane/MeOH/MeOH-BF3 method in the lipid extract from the egusi pudding, whereas the Hexane/MeOH/MeOH-BF3 method identified four more fatty acids in the lipid extract coming from Tetracarpidium conophorum. Although the number of fatty acids was similar, the derivatization method influenced the nature of the fatty acids in the egusi pudding lipid extract. Overall, polyunsaturated fatty acids were the most abundant in the different oils. Omega-3 were the majority subclass in Tetracarpidium conophorum nuts, while omega-6 were in egusi pudding. The derivatization method did not influence the majority fatty acid (alpha linolenic) in Tetracarpidium conophorum nuts, whereas derivatization with BF3 gave trans linoleic and KOH cis linoleic in egusi pudding. These results show that the choice of derivatization method for fatty acid profiling and quantification is very important and depends on the technique and extraction solvents used.
RESUMO
This study determined for the first time the structure of the peptides (i.e., peptidomics) in soy protein hydrolysates and elucidated their effects on an oil's oxidative stability during frying cycles. The oil investigated was palm olein during 0, 4, 8, and 12 frying cycles of plantain banana chips. Proteins were extracted and hydrolyzed with two proteases. Trypsin hydrolysate (HTRY) exhibited higher anti-radical activity (DPPH, 70.2%) than the control (unhydrolyzed proteins, 33.49%) and pepsin hydrolysate (HPEP, 46.1%) at 200 µg/mL. HPEP however showed a 4.6-fold greater reduction of ferric ions (FRAP) while also possessing a higher peroxyl radical scavenging ability (716 ± 30 µM Trolox Eq/g) than HTRY (38.5 ± 35 µM Trolox Eq/g). During oil oxidative stability tests, HPEP improved the oxidative stability of the palm olein oil after 8 and 12 frying cycles, characterized by lower concentrations of hydroperoxides, and carbonyl and volatile compounds. HTRY however exerteda pro-oxidant activity. Structural data from SDS-PAGE and tandem mass spectrometry showed that the mechanism for the greater activity of the pepsin hydrolysate occurred due to unique structural features and a higher percentage of short-chain peptides. This was justified by a 25, 31, and 48% higher contents of tryptophan, histidine, and methionine, respectively (important amino acids with hydrogen atom transfer and electron-donating capacities) in the peptides identified in the pepsin hydrolysate.
RESUMO
Objective: The aim of this study was to determine the chemical characteristics and antibacterial activity of Fontitrygon margarita liver oil against the bacteria responsible for food poisoning. Methods: Oils were extracted from F. margarita liver using two methods (exudation and cooking-pressing) and analyses by Fourier transform infrared (FTIR) spectroscopy. Quality indexes were determined using standard methods and the fatty acid profile was carried out by gas chromatography with a flame ionization detector (GC-FID). Antibacterial activities of these oils, their emulsion, and their interactions with common antibiotics were evaluated by the broth microdilution method. Results: Extraction yield was higher with cooking-pressing (16.90%) compared to exudation (14.49%). The quality indexes of both oils were conformed to Codex Alimentarius Standard. Thiobarbituric acid index was higher with exudation compared to cooking-pressing (3.20 ± 0.14 and 2.36 ± 0.14 µmol MDA/kg, respectively) while acid, iodine, peroxide, and anisidine values did not significantly vary with the extraction methods (2.15-2.30 mgKOH/g, 102.42-106.65 gI2/100 g, 3.34-3.57 meqO2/kg, and 2.85-3.32 respectively). FTIR analyses clearly show that the two spectra are similar (no differences in the frequency and absorbance of their bands). The fatty acid profile revealed that, regardless of the extraction methods, F. margarita oil is richer in monounsaturated (55.97-55.41%) followed by polyunsaturated (28.17-28.52%) and saturated fatty acids (15.86-16.07%). Moreover, these oils showed antibacterial activity on all the bacteria strains tested with MICs between 16 and 256 mg/ml. Regardless of the extraction methods, emulsions showed higher activity (6.25 ≤ MIC ≤25 mg/ml) compared to crude oils. Additionally, F. margarita liver oil potentiated the antibacterial activity of ciprofloxacin, tetracycline, gentamicin, amoxicillin, and chloramphenicol. Conclusion: These results showed the effectiveness of Fontitrygon margarita liver oil against some bacteria responsible for food poisoning, thus demonstrating their antibacterial properties which could be due to their chemical composition.
