Formation of volatile pyrrole products from epoxyalkenal/protein reactions

The production of volatile compounds in the reaction of the lipid peroxidation product (E)-4,5-epoxy-(E)-2-heptenal with lysine or bovine serum albumin was studied in order to characterise alternative mechanisms for production of volatile pyrrole derivatives in foods. A mixture of the lipid and the ammo acid or the protein was stirred overnight at 31°C and the volatiles formed were collected using a Tenax TA trap. Several aldehydes, ketones, alkylfurans, alkyl- and acyl-pyrroles, and alkylpyridines were identified by GC/MS. Formation of pyrrole derivatives in these reactions suggested the existence of alternative mechanisms for production of these flavour-associated compounds, previously considered to be formed mainly via Maillard reactions. This new route does not need the presence of sugars, and might contribute significantly to volatile pyrrole production in foods under conditions unfavourable for classic Maillard reactions.     

Neutron diffraction studies of liquid and crystalline trilaurin

Neutron diffraction has been employed to investigate the structure of trilaurin in both liquid and crystalline states. The combination of long-wavelength (4.5 Å) neutrons and wide angular ranges of detection (～6<2θ[^o]<～100) per mitted a large range of momentum transfer to be acceessed (～0.15?1]<～2) in a single scan of the detector. The chemical technique of selective deuteration of chosen parts of the triglyceride molecules was used to enhance specific aspects of the diffraction pattern and elucidate structures formed. The well established layer structure in the solid phases was confirmed in the diffraction patterns. It was also established that long-range ordering in the solid resulting from chain-chain registry disappeared when the solid melts. However, we found no evidence for long-range ordering in the form of persistence of a layer-layer spacing correlation in the liquid state. We postulate from the diffraction patterns a molecular arrangement resembling the arrangement found in the nematic phase of liquid crystals, where the layer structure is relaxed from that smectic-like arrangement for the crystalline phase. The data also reveal that this lack of order is not dependent on temperature in the liquid phase and persists into the super-cooled region below the normal β melting point.     

Viscosities of fatty acids, triglycerides, and their binary mixtures

Viscosity data have been obtained as a function of temperature for seven fatty acids (pelargonic, capric, lauric, myristic, palmitic, stearic, and oleic) and four triglycerides (tricaprilin, tripalmitin, tristearin, and triolein) and their binary mixtures at temperatures from above their melting points to 90°C. The viscosity measurements were performed by using Cannon Fenske glass capillary kinematic viscometers. Modified versions of the Andrade equation were used to correlate the kinematic viscosities of pure fatty acids and pure triglycerides. The MacAllister method was used for their binary mixtures. The correlation constants are valuable for designing or evaluating chemical process equipment, such as heat exchangers, reactors, distillation columns, and process piping.     

Degradation of unsaturated triglycerides injected into a pressurized reactor

To evaluate the precombustion chemistry of vegetable oils under conditions that exist in a diesel engine, several pure unsaturated triglycerides (triolein, trilinolein, trilinolenin) were injected into a pressurized reactor where they were subjected to thermal and oxidative degradation under varying conditions of atmosphere (air or nitrogen), temperature and pressure. Vapor samples were collected and then analyzed by gas chromatography/mass spectrometry techniques. In general, the samples consisted of similar mixtures regardless of the reaction conditions or triglyceride used as starting material. The most prominent compounds identified in these samples were fatty acids of different chain lengths and a variety of aliphatic hydrocarbons. Smaller numbers of other classes of compounds, such as aldehydes, were also detected. Presented at the 81st AOCS Annual Meeting, Baltimore, MD, April 1990.     

Triglyceride Content of Supercritical Carbon Dioxide Extracted Fractions of Beef Fat

Beef fat was fractionated using supercritical carbon dioxide at 40°C and pressures from 10.3–27.6 MPa. Extractions followed by one or two stage separation were collected at atmospheric pressure and ambient temperature. Triglyceride analysis of extracts using HPLC and evaporative light scattering detection resolved 15 major peaks. Triglyceride content (mg/g extract) was influenced by extraction conditions. Extraction at 27.6 MPa and separation at 20.7 MPa resulted in highest triglyceride concentration, while 13.8 MPa resulted in the lowest. Saturated and monounsaturated triglycerides were selectively extracted based on solvent density and molecular weight. Little selectivity of polyunsaturated triglycerides was observed for fractionating beef fat.     

Identification of major triglycerides causing the clouding of palm olein

Clouding was obtained by storing palm olein at 12.5°C for up to 24h and was separated by centrifugation. the fat crystals were collected after washing with cold acetone. The crystals were identified according to their fatty acid and triglyceride composition, carbon number and degree of unsaturation. Palmitic-oleic-palmitic (POP) and palmitic-oleic-stearic (POS) levels were high in the cloud material, especially in that recovered between 15–18 h of storage. The increase in POP and POS concentrations was concomitant with a decrease in the content of palmiticoleic-oleic (POO). The least amount of POO was also obtained in clouds collected between 15–18 h of storage, compared to the original oil sample. The increase of palmitic acid explained that triglycerides conjugated with palmitic acid molecules in their acyl chains could have been crystallized, and crystallization could have taken place in the order of the number of palmitic molecule in the acyl chain. The concentrations of the other triglycerides did not change much throughout the storage period. Further storage caused the composition of the cloud to become similar to that of the original oil sample.     

Gel Matrix Influence on Hydrolysis of Triglycerides by Immobilized Lipases

The hydrolytic activities and specificities of gel-entrapped C. cylindracae lipase (CCL) and R. arrhizus lipase (RAL) toward olive oil and tributyrin were investigated. Lipases in hydrophobic gels with the longest chain lengths generally displayed highest activity. The optimal temperature was 30–35° for free and 37–40° for gel-entrapped lipases. The ratio of the activity on tributyrin to that of olive oil (expressed as T/O ratio), an indicator of substrate specificity, increased from 0.3 for free lipases to 12.3 ± 2.3 for CCL lipase in ENTP-2000-formed gel and 16.2 ± 0.3 for RAL lipase in ENTP-4000-formed gel.     

The production of fish oils enriched in polyunsaturated fatty acid-containing triglycerides

A simple concentration technique was developed and used for the production of fish oils highly enriched with respect to the polyunsaturated triglycerides. The method involves the rapid solidification of fish oil droplets in liquid nitrogen followed by extraction with acetone at −60°C. The combined percentage ofcis-5,8,11,14,17-eicosapentaenoic acid (20:5) andcis-4,7,10,13,16,19-docosahexaenoic acid (22:6) after enrichment of a crude South African Anchovy (Engraulis capensis) oil was 57.4. A maximum percentage of 66.0 was attained for n-3 fatty acids after enrichment of a crude Chilean fish oil. A maximum yield of 26.0% was achieved for a crude sardine (Sardina pilchardus) oil. Triglycerides containing only saturated fatty acids or a combination of saturated and monoenoic acids were totally removed by the process, as assessed by silver-ion high-performance liquid chromatography of the triglyceride oils. This process permits the production of significant quantities of highly unsaturated triglycerides, which may be used in physiological and oxidative studies or for structural analysis of these triglycerides, many of which are present at extremely low concentrations in the original oils.     

Fast quantitative analysis of soybean oil in olive oil by high-temperature capillary gas chromatography

Analysis of glycerides has always been of great interest, especially to the food industry. Several methods have been developed, and attempts to improve analytical conditions are prevalent. Among these methods, high-temperature capillary gas chromatography has received particular consideration because it rapidly provides a glyceride profile. In this paper, we discuss a method to identify and quantitate mixtures of olive and soybean oils with the intention of verifying the latter as an adulterant of olive oils. The contamination of olive oil with soybean oil was detected by the presence of the triglyceride trilinolein, which does not exist in pure olive oil, although it is abundant in soybean oil. A calibration curve was constructed with several levels of contamination, and the lowest amount of detectable soybean oil was determined to be 4%.