The Antioxidation Mechanism of Polydimethylsiloxane in Oil.

Strong and stable antioxidation effects of polydimethylsiloxane (PDMS) are widely accepted and utilized in commercial frying oil; however, the mechanism is not fully established. On the other hand, canola oil contains about 700 ppm (mg/kg-oil) of the natural antioxidant, tocopherol. Canola oil containing 0, 1 and 10 ppm added PDMS was heated at 180°C for 1 h under stirring, then left for 2-3 days at room temperature; this treatment was repeated 5 times. Compared to pure canola oil, PDMS-containing canola oil exhibited remarkably lower peroxide, p-anisidine and acid values, a lower decrease in tocopherol content but a higher oxygen content during the heating experiments, implicating low oxygen consumption for the oxidation. While PDMS has not been known to exhibit antioxidative effects at ambient temperatures, the present results show that PDMS prevents autoxidation as well as thermal oxidation. In addition, PDMS, not tocopherols, provided the major antioxidative effect during intermittent heating, and the decrease of tocopherols was significantly inhibited by PDMS. Phase contrast microscopy confirmed that PDMS contained in canola oil was suspended as particles. Also, the oxygen content in standing PDMS-containing canola oil decreased as the depth of oil increased, corresponding to the PDMS distribution, which also decreased as the depth of oil increased. Moreover, PDMS had a higher affinity for oxygen than canola oil in a mixture of canola oil/PDMS, 1:1 v/v. Thus, it is suggested that PDMS restricted the behavior of oxygen dissolved in canola oil by attracting oxygen in and around the PDMS particles, which is wholly different from the radical scavenging antioxidation of tocopherol.

Study on the effect of polydimethylsiloxane from the viewpoint of oxygen content in oil.

It has been reported that polydimethylsiloxane (PDMS) inhibits oxygen dissolution into oil by forming a monolayer on the surface of the oil, thereby reducing thermal oxidation. In the present study, the distribution of PDMS was determined by the inductively coupled plasma atomic emission spectroscopy in standing PDMS-containing canola oil. PDMS did not disperse in the oil uniformly, but there was a tendency that the PDMS concentration decreased as the depth of oil increased, and the concentration of the bottom part was the lowest. When canola oil was covered with PDMS by dropping it gently on the surface of the oil and kept at 60°C, the oxygen content and oxidation of the oil were lower than those of the control canola oil. PDMS-containing canola oil and canola oil were heated with stirring from room temperature to 180°C, and then allowed to stand while cooling. Oxygen contents of both oils increased up to 120°C then dropped abruptly. While cooling, oxygen contents sharply increased at 100°C and approached the saturation content, although the increase for PDMS-containing canola oil was a little slow. Likewise, the thermal treatment of PDMS-containing canola oil and canola oil at 180°C for 1 h under stirring was repeated 5 times with standing intervals for 2-3 days at room temperature. Oxidation of the former was less than that of the latter in spite of its high oxygen content. In conclusion, the oxygen content of oil with/without PDMS addition increased, but oxidation of PDMS-containing canola oil was inhibited both during heating and standing with intermittent heating. It was suggested that PDMS exerted its antioxidative effect regardless of whether it covered the oil or was dispersed in it.

Antithrombic and anti-atherogenic effects of partially defatted flaxseed meal using a laser-induced thrombosis test in apolipoprotein E and low-density lipoprotein receptor deficient mice.

Atherothrombosis can be regarded as a 'life-style related disease' of which diet is one of the important risk factors. The prophylactic effect of partially defatted flaxseed meal (PDFM) on atherothrombosis has not yet been studied. The aim of this study was to assess the effect of PDFM and a lignan from flaxseed, secoisolariciresinol diglucoside (SDG), on thrombosis and atherogenesis. An earlier developed test, the quantitative assessment of laser-induced thrombus formation in the carotid artery of apolipoprotein E and low-density lipoprotein receptor deficient mice was used in this study. Thrombotic and atherosclerotic status was assessed in mice kept on a high-fat diet for 8 weeks (40% in energy). The diet contained 0.05% cholesterol alone (control) or the same cholesterol with added PDFM (5% w/w; 8.3 g/kg body weight per day) or SDG (0.06% w/w; 100 mg/kg body weight per day). PDFM showed antithrombotic (P < 0.01) and anti-atherogenic effect (P < 0.01). SDG did not affect either atherogenesis or thrombosis. This study suggests that dietary intake of PDFM can be beneficial in reducing the risk of high-fat-induced atherothrombosis.