ABSTRACT
The process of extraction for the quantitative separation of fat/oil is the basis for the majority of official methods. The extraction process, which separates the sample into two fractions, permits two approaches to quantitative measurement. The analysis can be performed by either weighing the fat/oil fraction directly, or indirectly by measuring the loss of weight due to extraction. Acceleration of the extraction process has been achieved by elevating the temperature of the solvent. This chapter discusses a recently developed primary method called the Filter Bag Technique (FBT). This technique utilizes temperatures of up to twice the boiling point of petroleum ether to accelerate extraction. High sample throughputs are accomplished by batch processing of samples encapsulated in filter media formed in the shape of a bag. The extraction is performed automatically in an ANKOM XT20 Fat Analyzer, an instrument that can process 20 samples in 20–60 min. The fat/oil percentage is calculated indirectly from the loss of weight from the sample in the filter bag. Various studies related to the extraction and gravimetric measurements of these fractions are discussed in this chapter for both the conventional method and the FBT. The accuracy of the FBT depends on effective predrying and proper weighing of the sample. Studies of the conventional method suggest that samples containing polyunsaturated fatty acids are sensitive to oxidation particularly during the solvent evaporation step when the oil is heated in the presence of oxygen. Various studies of the ruggedness of the FBT indicate that the method is not sensitive to small changes in analytical conditions. The ruggedness of the method was confirmed in an experiment utilizing Youden’s Ruggedness Test. When the accuracy of the FBT was compared to that of the conventional method with a wide variety of samples (n = 22) in a regression analysis, the two methods were highly correlated (R2 = 0.9996). There was essentially no bias (–0.046 intercept) and no distortion over the range of the samples (slope 1.001). Two collaborative studies with laboratories from five countries provided similar evidence of the accuracy of the FBT. The second collaborative study, designed to evaluate the FBT as an AOCS official method, was conducted with 28 samples presented as 56 blind 40duplicates. Twelve international collaborating laboratories used the FBT for the analysis, whereas three AOCS certified laboratories utilized the official methods. This study resulted in a similar highly significant R2 of 0.9990 compared with the official methods, with an intercept of 0.046 and a slope of 1.005. The average repeatability within laboratories was Sr = 0.31 and reproducibility among laboratories was SR = 0.46. These studies indicate that the FBT is an accurate and precise method capable of analyzing large quantities of samples in an efficient and automated fashion.
