含蜡原油结构抑制机理研究

基于含蜡模拟油加抑制剂GY1前后的特征温度、流变参数、析蜡量及微观结构的实验分析,研究含蜡原油结构抑制机理.结果表明:①抑制剂GY1不能阻止蜡结晶与晶核的形成,反而使析蜡量有所增加;②对于含粗晶蜡的模拟油,抑制剂GY1将阻碍其蜡晶生长,使蜡晶尺寸变小、非对称性增大,进而增强蜡晶颗粒相互作用与连接趋势,宏观表现为降凝与降粘效果差;③对于含微晶蜡的模拟油,抑制剂GY1有助于其蜡晶的聚集生长,使蜡晶尺寸变大、表面结合力降低,进而抑制蜡晶颗粒相互作用与连接趋势,宏观表现为降凝降粘效果显著;④含蜡原油结构抑制的机理就是使蜡晶颗粒聚集变大、提高其对称性、降低其分散度、抑制其相互作用与连接的机理.     

Release characteristics of paracetamol and oleuropein from Mech-Degla date fruit tablets enriched and non-enriched with freeze-dried olive leaf extract

Release characteristics of paracetamol from date (Phoenix dactylifera L., var. Mech-Degla) fruit tablets enriched and non-enriched with freeze-dried olive leaf extract (OLE) were studied. For this, two types of tablets (T) were obtained by direct compression: (1) T1 from P1-powder blend, containing 60% date powder (DP) and 40% paracetamol, and (2) T2 from P2-powder blend, containing 57% DP, 40% paracetamol, and 3% OLE. The release of paracetamol was studied in phosphate buffer (pH?6.8) and HCl solution (0.1N). Additionally, the oleuropein released was investigated in the case of T2-tablets. Based on obtained results, P1- and P2-powder blends showed acceptable flow properties in terms of Hausner’s ratio (1.30, in the case of P2) and angle of repose for both P1 (31 degrees) and P2 (33 degrees). Dissolution study showed that the released paracetamol achieved 80% after 70?min, whereas the oleuropein release was almost complete after 30?min. On the other hand, the Peppas model described correctly dissolution kinetics of both paracetamol (R²=?0.99) and oleuropein (R²=?0.89) whatever the applied dissolution medium. Furthermore, the presence of OLE in T2-tablets enhanced their microbiological shelf-life.     

Distributions of Polycyclic Aromatic Hydrocarbons and Phthalic Acid Esters in Gums and Soapstocks Obtained from Soybean Oil Refinery

Soybean oil gums and soapstocks are important by-products that may potentially be contaminated by persistent organic pollutants (POP) such as polycyclic aromatic hydrocarbons (PAH) and phthalic acid esters (PAE), thus lowering the value when using them as starting materials to produce animal feed additives, food industry ingredients, and pharmaceutical products. In the present work, PAH and PAE distributions in these two types of by-products were detected using solvent extraction–solid phase extraction purification coupled with gas chromatography–mass spectrometry. Total PAH and PAE amounts in the soapstocks were significantly higher than those in the gums, thus indicating that neutralization showed much higher removal efficiency than degumming in terms of PAH and PAE eliminations. Meanwhile, the results proved that the concentrations of these two kinds of contaminants in the soybean oil gums and soapstocks were much higher than those in the soybean oils, suggesting that further investigations were needed and that the contents of PAH and PAE in soybean oil refining by-products should be carefully monitored and regulated.     

Plant oil bioconversion into increase biological activity through lipases derived from wastes

The aim of this study was to show that abundant and inexpensive plant oils can be biotransformed to increase biological activity (antioxidant, antimicrobial and cytotoxicity) through hydrolysis reaction catalysed by lipases. We tested homemade and commercial lipases through the biotransformation of nine different plant oils in forty different combinations. First, the chemical composition of the samples was investigated. Thereafter, biological tests were conducted to assess the antioxidant and antimicrobial activity of the sampled biotransformation products, as well as analyzed their influence on the viability of healthy and cancer cells. Summarising, sunflower, corn and olive oils modified by orange waste-obtained lipases presented the most promising results, reaching up to 90% of antioxidant activity increase and significant growth inhibition of bacteria colonies belonging to genera Escherichia, Listeria, Staphylococcus, Pseudomonas and Salmonella. In addition, those compounds affected human oral squamous carcinoma cells. The bioconversion of plant oils through lipases improves their biological properties and might be an option for biotechnological application.     

Antioxidant Stability in Vegetable Oils Monitored by the ASTM D7545 Method

The PetroOXY method was used to evaluate the kinetics of oxidation of two edible vegetable oils, extracted from moringa and passion fruit. This method, which uses pure oxygen at 700 kPa is effective and fast and our experiments were carried out at temperatures 110–140 °C with BHA antioxidant additive concentration ranging from 0 to 500 ppm. Moringa and passion fruit oils followed first-order kinetics although, in the case of passion fruit oil, mathematical approximations in the first-order kinetic expression resulted in a final equation that could also be interpreted as deriving from zero-order kinetics. The higher stability of moringa oil was characterized by an activation enthalpy ca. 50 % higher than the one related to passion fruit oil.     

Influence of fatty acid composition on chemical changes in blends of sunflower oils during thermoxidation and frying

The influence of fatty acid composition on formation of new compounds at frying temperatures has been studied in seven samples of sunflower oils widely differing in their fatty acid composition. Thermal oxidation assays as well as frying experiments were carried out and samples were evaluated by measuring the new compounds formed, i.e. polymers, polar compounds and their distribution by molecular weight, and polar fatty acids and their distribution by molecular weight. The levels of all the new compounds analysed strongly depended on the degree of oil unsaturation; the two least unsaturated oils with low content of linoleic acid and high content of palmitic acid behaved exceptionally well. When considering polar compounds or polar fatty acids, the polymers/oxidised monomers ratio increased significantly as the level of degradation increased. The new compounds formed are practically identical when analysed in the used frying oils or in the lipids extracted from the counterpart fried potatoes, independently of the level of degradation.     

Maintenance of postharvest quality and bioactive compounds of fresh‐cut sweet leaf bush (Sauropus androgynus L. Merr.) through hot CaCl2 dips

The effects of hot CaCl₂ dips on postharvest quality and bioactive compounds of fresh‐cut sweet leaf bush were investigated. The vegetable was dipped in 0.5% or 1.0% (w/v) of CaCl₂ solutions at 40 °C for 30 s and the control was the untreated sample. Hot CaCl₂ dips significantly delayed the weight loss, maintained the overall quality and inhibited the wiltness (P < 0.05). Both hot CaCl₂ dips had no effect on the changes in lightness (L*) and delayed the decrease in greenness (‐a*) and total chlorophyll content and the increase in both yellowness (b*) and carotenoid content. Hot CaCl₂ dips enhanced total antioxidants, total phenolics content and both AsA‐POD and G‐POD activities from 38.6, 0.44, 15.2 and 22.4 at day 0 to 55.3, 0.55, 50.5 and 362.4 at day 8, respectively. Moreover, hot CaCl₂ dips also delayed the loss of DPPH free radical scavenging activity, total flavonoid, ascorbic acid and CAT activity when compared to other treatments during storage. This study showed that hot CaCl₂ dip maintains postharvest quality and enhanced bioactive compounds of fresh‐cut sweet leaf bush during storage.     

Effects of chitosan coating combined with essential oils on quality and antioxidant enzyme activities of grass carp (Ctenopharyngodon idellus) fillets stored at 4 °C

Effects of chitosan coating combined with essential oils from clove, cinnamon and lemon grass on quality and antioxidant enzyme activities of grass carp fillets stored at 4 ± 0.5 °C were evaluated. The quality parameters (including pH, total volatile basic nitrogen (TVB‐N), K value, thiobarbituric acid (TBA) value, shear force and total viable count (TVC)) and antioxidant enzyme activities were analysed periodically. The results indicated that composite chitosan coatings presented better preservation effects than chitosan coating alone. In addition, chitosan–clove essential oil coating had the best quality enhancement effects among treatments by inhibiting deterioration of physicochemical quality and microbial growth and maintaining antioxidant enzyme activities of fillets during refrigerated storage. The negative correlation was observed between the changes in TBA values and antioxidant enzyme activities in fillets. Based on these findings, chitosan–essential oil coatings effectively mitigated oxidative stress and extended shelf life of refrigerated grass carp fillets.