The effect of dihydrosphingosine (d18:0) on triacylglycerol (TAG) oxidation was examined with and without α-tocopherol. Three types of TAG from fish, linseed, and soybean oil were oxidized at 50°C to determine the effect of dihydrosphingosine (d18:0) with or without α-tocopherol on triacylglycerol (TAG) oxidation. The analysis of oxygen consumption and total volatile formation demonstrated a small effect of d18:0 on TAG oxidation in the absence of α-tocopherol. On the other hand, the combination of d18:0 with α-tocopherol showed strong antioxidant activity and completely inhibited volatile formation within 1400 h for soybean oil TAG, 650 h for linseed oil TAG, and 380 h for fish oil TAG.
The red alga Gracilaria vermiculophylla is a well-known producer of prostaglandins, such as PGE2 and PGF2α. In this study, the characteristics of glycerolipids as substrates of prostaglandin production were clarified, and the lipid classes, fatty acid composition, and glycerolipid molecular species were investigated in detail. The major lipid classes were monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), and sulfoquinovosyldiacylglycerol (SQDG), as well as phosphatidylcholine (PC), which accounted for 43.0% of the total lipid profile. Arachidonic acid (20:4n-6), a prostaglandin precursor, and palmitic acid (16:0) were the predominant fatty acids in the total lipid profile. The 20:4n-6 content was significantly high in MGDG and PC (more than 60%), and the 16:0 content was significantly high in DGDG and SQDG (more than 50%). Chiral-phase high-performance liquid chromatography determined that fatty acids were esterified at the sn-1 and sn-2 positions of those lipids. The main glycerolipid molecular species were 20:4n-6/20:4n-6 (sn-1/sn-2) for MGDG (56.5%) and PC (40.0%), and 20:4n-6/16:0 for DGDG (75.4%) and SQDG (58.4%). Thus, it was considered that the glycerolipid molecular species containing one or two 20:4n-6 were the major substrates for prostaglandin production in G. vermiculophylla.
In this study, the effect of three amplitudes of ultrasound-assisted solvent extraction (UASE) (0, 25 and 50 %; 100 W, 30 kHz; the 0% treatment serving as control) on yield and quality of extracted oil from P. khinjuk hull at various pretreatment times (15, 30 and 45 min) was evaluated. The highest oil yields at the three amplitude levels tested were 24.4, 29.8 and 37.8% for 0, 25 and 50 %, respectively. Although increase in pretreatment time increased oil yield, pretreatment time at 30 and 45 min did not significantly different for both 25 and 50% amplitude. Furthermore, UASE did not significantly affect fatty acid composition, peroxide value (PV), conjugated diene value (CDV) and anisidine value (AnV) of extracted oils. UASE also increased tocopherols and tocoterienols content of oils but pretreatment time at 30 and 45 min did not significantly different for them. Therefore, UASE increase yield and quality of extracted oil and reduce extraction time. All these advantages make UASE a good substitute for the extraction of oil.
The rules and patterns of thermal losses of tertiary butylhydroquinone (TBHQ) in palm oil (PO) and its effect on the qualities of PO were investigated by oven heating method. Volatilization and transformation products of TBHQ in PO were also studied in detail under heating treatment. Results showed that at low temperature (< 135°C), TBHQ had better antioxidative properties, while its antioxidative potency to PO was significantly weakened at high temperature (≥ 135°C). In addition, as heating temperatures increased and heating time prolonged, losses of TBHQ significantly increased in PO. Volatilization was the major pathway for losses of TBHQ in PO under heating treatment. Meanwhile, a small portion of TBHQ was transformed and the major transformation product was 2-tertbutyl-1,4- benzoquinone (TQ). Moreover, TQ and several decomposition products of PO were also observed in the volatilization products of TBHQ.
The present study is focused on the effect of the TTABr/MX/H2O-nanoparticles on the rate of piperidinolysis of ionized phenyl salicylate where TTABr represents tetradecyltrimethylammonium bromide and MX = NaCl, NaBr and CnH2n+1CO2Na with n = 4, 5, 6 and 7. Pseudo-first-order rate constant for the piperidinolysis of ionized phenyl salicylate at 35°C and constant concentration [PSa–]T = 0.2 mM, [Pip]T = 0.1 M, [NaOH] = 30 mM, [TTABr]T and different [MX] follow an empirical relationship which gives two empirical constant, Xkcat and KX/S. The value of relative counterion (X) binding constant, RXBr were calculated from the relationship; RXBr = Xkcat/Brkcat. The values of RXBr for X = C4H9CO2–, C5H11CO2–, C6H13CO2–, and C7H15CO2– are increasing with increase in the number of alkyl chain of counterion X.
A series of diester containing zwitterionic gemini surfactants, N,N-dimethyl-N-alkyl-2-[[hydroxy (alkoxy) phosphinyl]oxy]-alkylammonium designated as C8(-)-S-Cn(+), S = 2 and 3, n = 12, 14 and 16, were synthesized and characterized by instrumental techniques namely FT-IR, 1H NMR, 13C NMR, 31P NMR and Mass spectral studies. These new gemini surfactants further investigated for their various surfactant properties. The critical micelle concentration (cmc) and the effectiveness of surface tension reduction (Πcmc) were determined as a function of surfactant concentration by means of surface tension measurement. Micellization and viscosity properties were investigated by surface tension, electrical conductivity, dye micellization and rheology techniques. The findings of the aqueous surfactant system obtained were impacted by polarity, size and the nature of zwitterions as the surface. The thermodynamic and viscosity properties of these surfactants found to be based on the structures of gemini surfactants.
The present work involves a sensitive high-throughput microtiter plate based colorimetric assay for estimating lipase activity using cupric acetate pyridine reagent (CAPR). In the first approach, three factors two levels factorial design methodology was used to evaluate the interactive effect of different parameters on the sensitivity of the assay method. The optimization study revealed that the optimum CAPR concentration was 7.5% w/v, the optimum solvent was heptane and the optimum CAPR pH was 6. In the second approach, the optimized colorimetric microplate assay was used to measure lipase activity based on enzymatic hydrolysis of olive oil emulsion substrate at 37°C and 150 rpm. The emulsion substrates were formulated by using olive oil, triton X-100 (10% v/v in pH 8) and sodium phosphate buffer of pH 8 in ratio of 1:1:1 in the case of Candida sp. lipase. While in the case of immobilized lipozyme RMIM, The emulsion substrates were formulated by using olive oil, triton X-100 (1% v/v in pH 8) and sodium phosphate buffer of pH 8 in ratio of 2:1:1. Absorbance was measured at 655 nm. The stability of this assay (in terms of colored heptane phase absorbance readings) retained more than 92.5% after 24 h at 4°C compared to the absorbance readings measured at zero time. In comparison with other lipase assay methods, beside the developed sensitivity, the reproducibility and the lower limit of detection (LOD) of the proposed method, it permits analyzing of 96 samples at one time in a 96-well microplate. Furthermore, it consumes small quantities of chemicals and unit operations.
Castor oil methyl ester is a kind of biodiesel from castor oil. However, in those previous methods for biodiesel preparation using castor oil as feedstock, glycerol was the main by-product, which had a strong blocking effect on the immobilized enzyme activity and affected the mass transfer of reaction system. For avoiding the negative effect of glycerol on the enzymatic esterification, biodiesel was prepared using ricinoleic acid (RA) as acyl donor. Enzyme screening was also studied, and the effects of reaction temperature, molar ratio of ricinoleic acid and methanol, enzyme load, and reaction time, on the preparation of castor methyl ester were also evaluated. Response surface methodology (RSM) was used to optimize the interaction effect of reaction variables (reaction temperature (30-70°C), enzyme load (2-7%; relative to the weight of total substrates), molar ratio of methanol to ricinoleic acid (2:1-10:1), and reaction time (0.5-2.5 h)) on the acid value (AV) and the degree of esterification (DE). Validation of the RSM model was verified by the good agreement between the experimental and the predicted values of AV and DE. The optimum preparation conditions were as follows: reaction temperature, 48.2°C; enzyme load, 5.8%; molar ratio of methanol to ricinoleic acid, 5.56:1; reaction time, 2.36 h. Under these conditions, the AV and DE of the esterification reaction are 10.36±1.05 mgKOH/g and 94.03±0.60%, respectively. The relationship between initial reaction rate and temperature was also established, and the activation energy (Ea) of the enzymatic esterification is 33.87 KJ/mol.
Incorporations of nature fatty acids which were palmitic acid and stearic acid into the end positions of soybean oils were done using sn-1,3 specific immobilised lipase from Rhizomucor miehei at different ratios in order to produce symmetrical triglycerides without changing the fatty acids at sn-2 position. The optimum ratio for the process was 25:75 w/w. There were 19.2% increase of SFA for P25 and 16% increase for S25 at the sn-1,3 positions. The research findings indicated that the structured lipids produced from enzymatic interesterification possessed a higher oxidative stability than soybean oil. The newly formed structured lipids (SUS type) could be good sources for various applications in food industry.