Fatty acid Soxhlet extraction methods

Chromatographic methods were developed for the systematic determination of five classes of additives in PE for food packaging [170]. In Soxhlet extractions phenolic AOs and acid amides were determined by HPLC and CGC, respectively. Thiodipropionic acid esters were determined by HRGC as higher alcohols obtained after saponification of the extracts with KOH. Glycerol fatty acid esters and stearates were determined... 

TABLE 4. Comparison of Fatty Acid Composition of Wheat Germ Oil Extracted with SC-C02 and Soxhlet Methods. 

The fatty acid composition of the extracts was not affected by temperature, pressure, and the extraction method (Table 4). Supercritical carbon-dioxide-extracted oil samples had similar fatty acid composition to that of the Soxhlet-extracted oil (Table 4). All of the wheat germ extracts consisted of about 56% linoleic acid (18 2 n-6), which is an essential fatty acid (Table 4). The total unsaturated and polyunsaturated fatty acid (PUFA) content of the wheat germ oil was about 81 % and 64%, respectively. The SC-CO2 extraction of wheat germ resulted in extracts with similar tocopherol and tocotrienol compositions to those of the Soxhlet extracts (Table 8) (50). These results indicate that SC-CO2 technology can be used for extraction and fractionation of WGO components to obtain products with high quality. 

A supercritical fluid extraction (SFE) method for analysis of CO2 extractables in cranberry seeds was investigated. The SFE operating conditions were optimized to maximize the extraction yields. Extraction yields obtained by SFE were comparable to conventional Soxhlet extraction. The extracts were derivatized and then analyzed by GC-MS. The extracts obtained via hexane and CO2 mostly contained methylated fatty acids. Linoleic acid and palmitic acid were the major compounds extracted. 

The objective of this research was to determine the quantity and chemical composition of supercritical CO2 extractables from cranberry seeds. SFE parameters such as CO2 pressure, extraction temperature/time, and CO2 flow rate were optimized to obtain the best possible extraction conditions. The amount and type of SF extractables have been compared with Soxhlet extractables to evaluate the feasibility of SFE as an alternative extraction method. The SF and Soxhlet extracts were compared by gravimetric determination followed by derivatization of the fatty acids into their methyl esters with subsequent determination of their compositions by GC-MS. 

In a companion study, M. Palma et al. studied the extraction of grape seeds with pure SF CO2 and analyzed the derivatized extracts by GC-MS. These extracts were found to contain volatiles such as aliphatic aldehydes in addition to fatty acids and sterols. Even though we used similar conditions for our SF extraction and GC-MS analysis, we were unable to detect any similar volatile compounds. To further investigate the presence of volatiles in the cranberry seed extract, we adapted a solid phase microextraction (SPME) method from the work of Jelen et al. who had earlier developed it for the characterization of volatile compounds in different vegetable oils. SPME followed by gas chromatog[raphy was performed on the headspace of the cranberry seed extract to test for the presence of volatile compounds. The GC trace failed to show the elution of any components for either the SF or Soxhlet extract. 

One of the most interesting fields of application of MAE in food analysis is the extraction of lipids. This step, traditionally performed with conventional Soxhlet extraction, has been performed with the focused microwave-assisted Soxhlet extractor prototype of Figure 2B. Extraction of oil from olives, srm-flower seeds, and soyabeans extraction of the lipid fraction of dairy products (milk and cheese) and extraction of fatty acids from precooked and sausage foods have significant advantages over conventional methods, including dramatically reduced extraction times, lower degradation of thermolabile analytes, and acceleration of other analytical steps such as hydrolysis in milk samples, in addition to completeness of analyte extraction, which is not always achieved with conventional methods. 

In connection with the more recent interest in SFC, methods for the analytical application of extraction with supercritical fluids have been extensively developed. At the Arrhenius Laboratories SFE has been applied to the extraction of different types of rapeseeds and other oil seeds as a part of a breeding project. SFCs of two of these extracts are shown in Fig. 2.8. Traditionally, such seeds are examined for total fat content, either gravimet-rically after Soxhlet extraction or by means of elementary analysis. In addition, the fatty acid pattern is analysed by GC after hydrolysis and methylation. Soxhlet extraction can be replaced by SFE followed by a gravimetric analysis to quantify the extract. Alternatively, quantification can be performed on a detector (ELDS) that has been connected directly to... 

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