Rancimat instrument

The Oil Stability Index (OSI) is another method to measure oil stability that can be conducted using AOCS Method Cd 12b-92 (AOCS, 2005) with a Rancimat instrument or an Oxidative Stability Instrument. The OSI may be run at temperatures of 100, 100, 120, 130, and 140°C. Although oil processors and food manufacturers are interested in rapid measurements of oxidation, the high temperature at which the procedure is conducted may not be relevant to ambient temperatures used for most oil storage. Frankel (1993) suggested that the variation in results at 110°C with the rapid analysis and ambient temperature storage may be because of differences in the oxidation mechanisms at the two temperatures. 

NOTE This method relies on either of two commercially available instruments that consist of a means of controlling sample temperature (maintained at 0.1 °C), an air distribution system, conductivity tubes, stoppers and probes, and electronics or software for measuring conductivity and determining induction period. The following steps are generally applicable to both the Rancimat and the Oxidative Stability Instrument however, some variations exist due to differences in hardware and models available. Consult the manufacturer s instructions for additional detail. 

The Biodiesel Stability (BIOSTAB) project, supported by the European Commission, was initiated in 2001 to establish clear criteria and analytical methods for the monitoring biodiesel fuel stability (Various, 2003 Prankl, 2002). The resulting unified method, EN 14112 (Anon., 2003c) established a means for measuring oxidative stability utilizing the Rancimat or oxidation stability instruments. This test method was essentially developed from standards employed in the fats and oils industry to measure isothermally the induction period for oxidation of fatty derivatives. At present, both biodiesel fuel standards ASTM D 6751 (Anon., 2007a) and EN 14214 (Anon., 2003b) include an oxidative stability specification based on measurement by method EN 14112. 

OSI method (Rancimat Oxidative Stability Instrument) Volatile organic acids Monitoring changes in conductivity Rapid and automated Fats and oils... 

Active oxygen method (AOM) Bubbling air in a closed environment, 98°C, do not represent normal storage Rancimat is the automated version, also OSI instrument... 

Oa StabUity Index. Two conductivity instruments, Rancimat and The Oxidative Stability Instmment, have been developed as alternatives to AOM Stability analysis. These instruments measure the increase in deionized water conductivity resulting from trapped volatile oxidation products produced when the oU product is heated under a stream of air. The conductivity increase is related to the oxidative stabihty of the products. These instruments provide a more reproducible measurement of oxidation stability with less technician time and attention. 

The active oxygen method (AOM) is the most common analytical method used to measure oxidative stability of fats and oils products. AOM employs heat and aeration to accelerate oxidation of the oil by continuously bubbling air through a heated sample. Periodic peroxide values are measured to determine the time required for the oil to oxidize to a predetermined peroxide value under the AOM conditions. This method requires close attention to detail to produce reproducible results and even then the variation between laboratories is 25 for a 100 h AOM sample. Conductivity instruments such as the Rancimat and the Oxidative Stability Instrument have been developed as alternatives to AOM stability analysis. These instruments measure the increase in the conductivity of deionized water resulting from trapped volatile oxidation products produced when the oil product is heated under a stream of air. The conductivity increase is related to the oxidative stability of the products. These instruments provide a more reproducible measurement of oxidation stability with less technician time and attention. 

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 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]. 

---