oil extraction and analysis phần 6 potx

Chapter 6

Oil Content Analysis: Myths and Reality

V.J. Barthet and J.K. Daun

Canadian Grain Commission, Grain Research Laboratory, Winnipeg, Manitoba R3C 3G8,

Canada

Abstract

The FOSFA (Federation of Oils, Seeds and Fats Associations Limited) extraction

method (harmonized as AOCS Am 2-93 or ISO 659) is considered to be the refer￾ence method to measure the oil content of oilseeds. The method is based on the

extraction of neutral lipids with hexane or petroleum ether, and the extracted com￾ponents are estimated gravimetrically and defined as crude fat or oil content. The

method requires a triplicate grind/extraction, making it lengthy and very detailed

for the analyst. Compared with other official methods (AOAC 996.06), the

FOSFA extraction method gave the highest oil recoveries in all oilseeds tested.

Accelerating the extraction through the use of new instrumentation, which com￾bines solvent extraction with a physical disruption such as pressure or microwave

heating, has not been able to give oil recovery equal to the FOSFA extraction.

Although the FOSFA method remains the reference method, both ISO and AOCS

have identified a need to develop new rapid methods for oil extraction that yield

oil equivalent to that from the FOSFA method and that can be used for determina￾tion of other factors such as methyl esters or free fatty acids. This study examined

the lipid components extracted by each stage of the FOSFA method: First

Extraction (FOSFA1), Second Extraction (FOSFA2), and Third Extraction

(FOSFA3). In a typical analysis, FOSFA1 accounted for ~86%, FOSFA2 for

~13.5%, and FOSFA3 for as much as 0.5% of the total oil extracted. Although

mainly triacylglycerols (TAG) were found, the extracts contained small amounts

of other lipid components including nonesterified fatty acids, partial glycerides,

fat-soluble vitamins, long-chain alcohols or aldehydes, and sterol or cholesterol

esters. More nonpolar material was extracted in the first early stage of the extrac￾tion, whereas the later stages contained more polar material. The oil in FOSFA1

and FOSFA2 contained close to 98% TAG based on methyl ester determination.

The analyses of the phosphorus content by graphite furnace atomic absorption

spectrophotometry showed that almost no phosphorus (below limit of detection)

was found in FOSFA1 and FOSFA2 oils but small amounts of phosphorus were

present in FOSFA3 oils. This indicates that only ~0.5% of phospholipids were pre￾sent in the FOSFA3 oils, suggesting that only very small amounts (<0.005%) of

phospholipids are extracted by the total method when the three extracts are com￾Copyright © 2004 AOCS Press