A modified method for determining free fatty acids from small soybean oil sample sizes

Abstract

A modification of the AOCS Official Method Ca 5a-40 for determination of free fatty acids (FFA) in 0.3 to 6.0-g samples of refined and crude soybean oil is described. The modified method uses only about 10% of the weight of oil sample, alcohol volume, and alkali strength recommended in the Official Method. Standard solutions of refined and crude soybean oil with FFA concentrations between 0.01 and 75% were prepared by adding known weights of oleic acid. The FFA concentrations, determined from small sample sizes with the modified method, were compared with FFA percentages determined from larger sample sizes with the Official Method. Relationships among determinations obtained by the modified and official methods, for both refined and crude oils, were described by linear functions. The relationship for refined soybean oil had an R 2 value of 0.997 and a slope of 0.99 ± 0.031. The values for crude soybean oil are defined by a line with R 2 = 0.9996 and a slope of 1.01 ± 0.013. JAOCS 75, 563-568 (1998). KEY WORDS:Crude soybean oil, free fatty acid, Official Method, refined soybean oil, titration.In the soybean industry, the presence and development of any amount of free fatty acid (FFA) in soybean oil is undesirable. The FFA content of oil in soybeans indicates how well the beans have been treated during the period between harvest and processing. The eventual consequence of high FFA content is monetary loss because processing soybeans with high FFA content results in more refining loss. Specifically, refining loss is the sum of oil weight lost during removal of FFA and other impurities plus the weight of entrained neutral oil in soapstock during the normal alkali-refining process. The percentage of oil lost during refining can be estimated as a multiple of the FFA percentage. Norris (1) estimates the potential loss at about three times the FFA content. Because of the economic impact of high FFA, it is important to determine the initial level of FFA in soybean oil and also to monitor its concentration during processing.The standard method for FFA determination in extracted crude and refined soybean oil samples is based on an acidbase titration technique in a nonaqueous system. The method commonly used is AOCS Official Method Ca 5a-40 (2). The procedure prescribes an oil sample of maximum 56.4 g and minimum 3.53 g for the titration, depending on the level of FFA in the oil sample. When oil quantities are limited, as in some storage studies or when experimental use of oilseed crops is evaluated, sample sizes of this magnitude are not possible. A simple and inexpensive method is needed that accurately quantifies FFA content from a smaller sample size.The use of smaller amounts of chemicals will have an impact, especially in developing countries, where chemicals are scarce and expensive. Also, it is prudent to limit the use of resources, particularly those hazardous to the environment. For example, hexane, a solvent used in the titration, is a hazardous, highly flammable compound, and its disposal can be harmful to the en...

Oral Thresholds and Suprathreshold Intensity Ratings for Free Fatty Acids on 3 Tongue Sites in Humans: Implications for Transduction Mechanisms

“…Receptor-mediated transduction may predominate at low stimulus concentrations, but when receptor binding is saturated and FFAs are available, diffusion may be the predominant route of passage across membranes (Ibrahimi and Abumrad 2002). Unbound FFA concentrations in the circulation may be in the nanomolar range (Azzazy et al 2006), but concentrations 6-8 orders of magnitude higher may occur in the oral cavity while eating (Rukunudin et al 1998;Wan et al 1998;Bertran et al 1999;Che Man et al 1999;Gopala Krishna et al 2006;Li et al 2008).…”

Impact of extraction method on yield of lipid oxidation products from oxidized and unoxidized walnuts

“…PV and conjugated dienes were determined by the American Oil Chemists' Society (AOCS) official methods Cd 8-53 and Ti 1a-64, respectively (10). FFA were measured according to a modification of method Ca 5a-40 (10) proposed by Rukunudin et al (11) using a 0.5-mL oil sample. Total oil content was determined gravimetrically after the extract was dried to a constant weight as outlined in method Ca 2c-25 (10).…”

Assessment of conventional and microwave heating induced degradation of carotenoids in olive oil by VIS Raman spectroscopy and classical methods

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