Physicochemical Changes in Hazelnut, Olive Pomace, Grapeseed and Sunflower Oils Heated at Frying Temperatures

Abstract

In order to compare the thermal performances to evaluate suitability for frying, hazelnut oil (HNO), olive pomace oil (OPO), grapeseed oil (GSO) and sunflower oil (SSO) were heated for 5 h / 5 consecutive days at 175 ± 5 ℃, and sampled at the end of each day. Free acidity, peroxide value, conjugated dienes, total polar materials, viscosity, and CIE color values were measured. Highest values of free acidity, conjugated dienes, total polar materials and viscosity were observed in grapeseed oil sample. GSO has reached to a very viscous state during the earlier hours of the operation; hence it is not suitable for frying. Better thermal performances have found with HNO and OPO when compared to the control oil, SSO. Therefore, both oils can alternatively be used as new frying oils effectively.

Chemical modifications of ricinolein in castor oil and methyl ricinoleate for viscosity reduction to facilitate their use as biodiesels

“…The kinematic viscosity of oxidized ricinolein (II) was greatly reduced (by 92% in contrast with castor oil) and it was verified to be almost as low as that of grape seed oil and soybean oil (see Table 1) [13]. Therefore, it is our anticipation that oxidized ricinolein could serve as an alternative promising biodiesel precursor, similar to soybean oil which has been widely used for long period of time.…”

“…Oxidation reaction was subsequently performed in the presence of Dess-Martin periodinane. The chemical structure was further analyzed by 1 H NMR and 13 C NMR, and the yield of oxidized product was confirmed to be the same as the product obtained from the previous procedures. In addition, kinematic viscosity and density were found to be similar as well and thus we could infer that the order in which the two reactions are carried out does not affect the production of biodiesel.…”

“…Here we demonstrated in our studies that oxidation of hydroxyl groups to carbonyl groups on ricinolein was feasible and the product was accordingly characterized by 1 Figure S4). And in 13 C NMR spectrum of oxidized ricinolein (II), the characteristic signals show at 209.02 ppm (-CH 2 COCH 2 -), 173.09 ppm (-OCO-), 133.36 ppm ( --CHCH2CO-), 121.03 ppm (-CH 2X CH 2 CH --), 68.85 ppm (-CHOCO-), 62.01 ppm (-CH 2 OCO-), 42.27 ppm ( --CHCH2CO-), 41.57 ppm ( --CHCH2COCH2-), 33.91 ppm (-OCOCH 2 -), 13.97 ppm (CH 3 -C). According to NMR data, we could infer that hydroxyl group of castor oil has been conversed to carbonyl group.…”

“…Once the top layer was extracted, the methanol was then removed via rotary evaporation, and then the product was dried by anhydrous sodium sulfate. The product methyl ricinoleate (III in Scheme 3) was confirmed by 1 H NMR and 13 C NMR using deuterated dimethyl sulfoxide (DMSO-d6) as the solvent.…”

“…Tetramethyl silane (TMS) was added as a position standard for the chemical shifts. The 1 H NMR spectra were recorded at 400 MHz and 13 C NMR spectra were recorded at 100 MHz on an Avance III 400 NMR spectrometer (Bruker). The numbers of scans done were 8 for 1 H NMR and 100 for 13 C NMR.…”