Rancimat test

Lacoste, F., and Lagardere, L. 2003. Quality Parameters Evolution During Biodiesel Oxidation Using Rancimat Test. Eur. J. Lipid Sci. Technol., 105,145-155. 

According to these results, the relative antioxidant effectiveness of BHT increased with decreasing temperature, and it decreased for GP. The Rancimat method underrated the stability of those samples containing BHT, perhaps because of volatilization of antioxidants during Rancimat testing. The relative activity of... 

Dittmar, T B. Ondruschka J. Haupt M. Lauterbach. Improvement of the oxidative stability of fatty acid methyl esters with antioxidants—limitations of the rancimat test. Chemie Ing. Techn. 

Lacoste, E L. Lagardere. quality parameters evolution during biodiesel oxidation using rancimat test. Eur. J. LipidSci. Technol. 2003,105, 149-155. 

Ferulic acid (36) Antioxidant activity by extending the induction time of lipid oxidation in the Rancimat test 108... 

Lipid oxidation is also estimated by instrumental analyses such as by Rancimat test method and used for accelerated stability study [6]. Electron spin resonance can measure radical formation in many types of food matrices [7]. Analysis of volatiles with dynamic headspace/GC-MS is highly sensitive and can provide lot of information with regard to volatile lipid oxidation products and other volatiles with sensory impact in food samples. This type of data can also give information on possible reaction pathways of food deterioration [8]. Front-face fluorescence spectroscopy... 

The monohydroperoxides of triacylglycerols predominate in commercial oils (more than 90% of total peroxides), but the structure (and reactivity) of lipid hydroperoxides formed is related to the type of oil. For this reason, in some of the CL methods developed, the analytical signal depends not only on the concentration of peroxides present in the sample but also on the nature of the sample. This state was highlighted by Bunting and Gray (2003). The lipid hydroperoxides produced in oxidized oil during the Rancimat test have been monitored by the luminol CL reaction (Matthaus 1996). The obtained results were satisfactory, as the induction periods of the oils assessed by Rancimat and CL methods showed a significant linear correlation. 

The oxidative stability of oils and fats is an important parameter for the analysis of their quality. It is performed using the Rancimat test equipment or the Omnlon Instrument to measure the changes in the electrical conductivity in water caused by the formation and release of volatile oxidation compounds [13]. 

In addition to sensory evaluation, some other parameters are suitable to describe the quality of cold-pressed oils. Such characteristic features are oxidative stability (Rancimat test), tocopherol content and composition, amount of trans-fatty acids or stigmastadiene, showing a heat treatment during production, as weU as content of chlorophyll, as a measure not only for the maturity of the raw material, but also as an indicator of improper pressing conditions. 

In the literature, canolol is described as an effective antioxidant (Koski et al., 2003 Kuwahara et al., 2004 Vuorela et al., 2005 Wakamatsu et al., 2005). Figure 17.8 shows increased oxidative stability of canola oil accompanied increasing amounts of canolol. Using the Rancimat test at 120°C canolol contents below 200 itg/g in canola oil from roasted seeds resulted in slight decrease of the oxidative stability. In contrast, amounts of canolol higher than 200 g/g improved oxidative stability of the oil dramatically. Wijesundera et al. (2008) also showed an improvement in... 

FIGURE 17.8 Formation of canolol during roasting of canola seeds and its effect on the oxidation stability of the resulting oil in the Rancimat test at 120°C. 

At higher contents of canolol in the oil, a good correlation with the oxidation stability using the Rancimat test was found. If the temperature load was <15 min at 180°C, a decrease in the oxidation stability was observed due to the low formation of canolol. With increasing temperature load, the oxidation stability increased from 4 to 7 h, before the oxidation stability decreased again as a result of a temperature load of more than 45 min at 180°C. At a low temperature load, less canolol is formed so that the temperature is sufficient to impair the oxidation stability of the oil. Only when the content of canolol in the oil from roasted seeds increases does oxidative stability improve. If the temperature load is too high, the impairment of the oil is faster, then the formation of canolol can improve the oxidation stability. 

Other parameters that are usually determined to assess the oil stability and quality are the acid index (Al) and the peroxide value (Ca 5a-40 and Cd 8-53 AOCS Methods). The oxidative stability is also an important parameter in the characterization of fats and oils that can be determined among other methods by using the Rancimat test. 

Figure 18 Rancimat tests of (k). Biodiesel(methyl soy ate) and ( ). treated biodiesel (ozone/methanol)...

Cold-pressed hempseed oil varies from off-yellow to dark green due to the presence of carotenoids and chlorophylls at different levels (Defeme and Pate, 1996 Oomah et al., 2002). While the presence of carotenoids and tocopherols increases the oxidative stability of oil, the presence of chlorophylls increases the risk of oxidation. With high unsaturation levels (see later and Table 11.1.1), virgin hempseed oil was reported to have oxidative stability based on the Rancimat test at 120°C (Matthaus and Briihl, 2008), 1.32h at 110°C (Uluata and Ozdemir, 2012), and 6.4-7.6h at 100°C (Dimic et al., 2009). A slightly better value of 1.35-1.72h at 120°C was also reported (Anwar et al., 2006). Therefore, great care must be taken to prevent oil oxidation. 

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