A novel method to quantify glycidol fatty acid esters (GEs), supposed to present as food processing contaminants in edible oils, has been developed in combination with double solid-phase extractions (SPEs) and LC-MS measurements. The analytes were five species of synthetic GEs: glycidol palmitic, stearic, oleic, linoleic and linolenic acid esters. The use of selected ion monitoring in a positive ion mode of atmospheric chemical ionization-MS with a reversed-phase gradient LC provided a limit of quantification of 0.0045-0.012 mg/mL for the standard GEs, which enables the detection of GEs in mg ranges per gram of edible oil. Using the double SPE procedure first in reversed-phase and then in normalphase second, allowed large amounts of co-existing acylglycerols in the oils to be removed, which improved the robustness and stability of the method in sequential runs of LC-MS measurements. When the method was used to quantify GEs in three commercial sources of edible oils, the recovery% ranged from 71.3 to 94.6% (average 79.4%) with a relative standard deviation of 2.9-12.1% for the two oils containing triacylglycerols as major components, and ranged from 90.8 to 105.1% (average 97.2%) with a relative standard deviation of 2.1-12.0% for the other, diacylglycerol-rich oil. Although the accuracy and precision of the method may not be yet sufficient, it is useful for determining trace levels of GEs and will be helpful for the quality control of edible oils.

We previously reported a method to quantify five species of glycidol fatty acid esters (GEs) in edible oils which used a combination of a double solid-phase extraction (SPE) and liquid chromatography-mass spectrometry (LC-MS) using fast HPLC. To expand its application, we established a new method using conventional HPLC, which is applicable not only to liquid oils but also to solid ones. The optimized LC-MS conditions using conventional HPLC were useful for standard GEs but not for oil samples because of the insufficient accuracy during sequential runs. Thin-layer chromatographic studies revealed that co-existing diacylglycerols were not sufficiently removed by the original SPE procedure due to excessive amounts of oil applied to the normal-phase SPE, which disturbed the quantitative and stable detection only when conventional HPLC was employed. The amount of oil applied was decreased tenfold (100 mg ? 10 mg), which resulted in stable LC-MS measurements. Furthermore, the use of chloroform/acetone, instead of acetonitrile, prior to the SPE treatment expanded its applicability to solid oils, with recovery values ranging from 102.7 to 109.5% for three oil samples (two liquid and one solid oils). This method can form the basis of a standardized method for the quality control of GEs in edible oils.

We examined the crystallization behavior of high-melting fractions in liquid oil containing high concentrations of diacylglycerols (DAG [80%) (hereafter referred to as DAG-rich oil). By differential scanning calorimetry and optical microscopy at moderate cooling rates, crystallization in the DAG-rich oil was detected at around 6°C. It was found that the crystallization extent increased with decreasing temperatures of crystallization below 0°C. A gas chromatographic analysis was performed on the crystallized fractions, which were separated by filtration at different periods of isothermal crystallization at 3°C. The results indicated that at earlier crystallization periods, the concentrations of 1,3-disaturated DAG such as palmitic and stearic acid moieties (15 min) and 1,3-saturated-unsaturated mixed-acid DAG including oleic acid, palmitic, and stearic acid moieties (15 min-3 h) were predominant. However, the concentrations of 1,3-diunsaturated DAG including oleic acid moiety increased after a crystallization period of 6 h. To clarify the sequential crystallization process of DAG, we examined the binary mixing behavior of principal DAG components occurring in the rapeseed-based DAG-rich oil. It was evident that 1,3-disaturated DAG, 1,3-saturated-unsaturated mixedacid DAG, and 1,3-diunsaturated DAG exhibited immiscible behavior. From these data, basic information on the precipitation processes in DAG-rich oils at chilled temperatures was obtained.

Theaflavins are polyphenols found in black tea, whose physiological activities are not well understood. This study on mice evaluated the influence of a single oral administration of theaflavins on energy metabolism by monitoring the initial metabolic changess in skeletal muscle and brown adipose tissue (BAT). Oxygen consumption (VO2) and energy expenditure (EE) were increased significantly in mice treated with theaflavin rich fraction (TF) compared with the group administered vehicle alone. There was no difference in locomotor activity. Fasting mice were euthanized under anesthesia before and 2 and 5, 20-hr after treatment with TF or vehicle. The mRNA levels of uncoupling protein-1 (UCP-1) and peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α) in BAT were increased significantly 2-hr after administration ofTF. The levels of UCP-3 and PGC-1α in the gastrocnemius muscle were increased significantly 2 and 5-hr after administration of TF. The concentration of phosphorylated AMP-activated protein kinase (AMPK) 1α was also increased significantly in the gastrocnemius 2 and 5-hr after treatment with TF. These results indicate that TF significantly enhances systemic energy expenditure, as evidenced by an increase in expression of metabolic genes.

Liquid oil containing high concentrations of diacylglycerols (DAG > 80 %, hereafter referred to as DAG‐rich oil) is generally more likely to cause precipitation at chilled temperatures (clouding phenomena) than triacylglycerol‐based oil. The clouding phenomena that occur during long‐term storage of DAG‐rich oil are unwanted in consumer products and therefore, must be prevented. In the present study, we attempted to retard precipitation by adding food emulsifiers, polyglycerol fatty acid esters (PGFE) containing different fatty acid moieties. DSC, polarized optical microscopy, and X‐ray diffraction studies revealed that the addition of 0.2 % PGFE containing palmitic and oleic acid moieties very effectively retarded precipitation in the DAG‐rich oil. To confirm these observations, we prepared a model DAG oil to mimic DAG‐rich oil and examined the retardation behavior of high‐melting DAG fractions using PGFE. The results are discussed in terms of the effects of PGFE additives on the pre‐nucleation processes of high‐melting fractions in DAG‐rich oil.