American Oil Chemists Society Methods Research Articles

Wijs, Potassium Iodate, and AOCS Official Method to Determine the Iodine Value (IV) of Fat and Oil

Fatty acid, present in edible oil, is a key constituent in our diet. The iodine number is a measure of the amount of unsaturated fatty acid in fat and oil. Iodine is a trace element that is required by humans for normal biological function. The iodine value (IV) of four edible oils was determined in this study: castor oil, peppermint oil, almond oil, and coconut oil. Iodine is a wonderful reagent for converting the unsaturation into the saturation of fat and oil. The purported technique offered a reliable and rapid determination of IV. The Wijs, or iodine monochloride, potassium iodate, and American Oil Chemists' Society's (AOCS) Fourier transform infrared spectroscopy (FT-IR) are all used to determine IV. Both Wijs and potassium iodate are iodometry-based titrations, whereas the AOCS method is applied through FT-IR. C=C stretching in the range of 1635.48cm-1-1652.77 cm-1, C=O band in the range of 1744.23 cm-1- 1747.49 cm-1, C-H stretching in the range of 2923.9 cm-1- 2925.85 cm-1, O-H stretching in the range of 3448 cm-1- 3472 cm-1 were observed in different dilution for identification of unsaturated fatty acid in numerous oils through FT-IR. All methods are satisfactory; meanwhile, the potassium iodate method is safer than the Wijs method experimentally and more economical than the AOCS method. IV for castor oil, peppermint oil, almond oil, and coconut oil were computed at 84.67 I2/100g,5.56 I2/100gm,99.09 I2/100gm,8.21 I2/100gm along with the deviation by three methods.

An International Collaborative Study on Trypsin Inhibitor Assay for Legumes, Cereals, and Related Products

AbstractFor determining trypsin inhibitor activity (TIA) in soy products, the American Oil Chemists' Society (AOCS) Method Ba 12‐75 has been used. It measures differences in absorbance at 410 nm of bovine trypsin activity toward a synthetic substrate (Nα‐benzoyl‐DL‐arginine‐p‐nitroanilide) in the absence and presence of an inhibitor. Recently, a significantly improved method was developed (JAOCS, 2019, 96:635–645), featuring 5 mL of total assay volume, enzyme‐last sequence, and single inhibitor level in duplicate. It is proposed as the AOCS Method Ba 12a‐2020. As a part of the AOCS method approval process, a collaborative study involving 12 international laboratories was conducted to evaluate the performance of the proposed method. The study involved measuring TIA in 10 selected test samples plus a blind duplicate. They included soybeans, pulses, cereals, and their processed products (flours, concentrates, and isolates). After rigorous statistical treatment of the data, only three outliers were removed from the data of two samples. Repeatability relative standard deviations (RSDr) for the 11 samples ranged from 0.99% to 5.52%. Reproducibility RSD (RSDR) ranged from 7.07% to 22.92%, with seven samples having RSDR around 10% or less. The remaining four samples had very low TIA, and their RSDR values ranged from 13.34% to 22.92%. The study has demonstrated reliable performance of the proposed AOCS method. Several collaborators carried out additional experiments addressing some aspects of the method, leading to further refinements. The proposed method is undergoing evaluation by the AOCS Uniform Methods Committee for adoption as an Official Method for measuring TIA in various legume and grain products.

The Influence of Oil Raw Materials on The Quality of Finished Soap Products in The Laboratory Division at PT. Solar Wings Corps

The business actors are required to generate the maximum profit possible, thus demanding workers to work productively. This cannot be denied because workers are the most essential element in running the company’s wheels. PT Wings Surya is a manufacturing company that produce soap. this research activity focuses on how to check soap products using the AOCS Method, in which the AOCS (The American Oil Chemists’ Society) method is a method applied to measure and analyze levels in oil so that it is known whether these levels already meet the standards to be processed into a quality product. The quality of the finished soap product can be determined and anticipated by looking at the quality of the Iodide Value, Peroxide Value, and Saponification Value of the raw oil used for the soap product. The finished product of soap at PT. Wings Surya in November based on the quality of the raw material used, it will produce a finished product of soap with good quality but not with the rancid smell caused by the raw material of the oil it self.

Validation of the SafTest Percent Fat for the Measurement of the Fat Content of Meat Meals, Fish Meal, and Potato Chips, Crackers, and Other and Grain-Based Snack Products: AOAC Performance Tested MethodSM #082004.

The Official American Oil Chemists Society (AOCS) Standard Procedure Aa 4-38, AOCS Standard Procedure Am 5-04, ISO 11085:2015, and similar methods are based on extraction of fats from food products using organic solvents. These methods require large volumes of organic solvents and up to 18-hour extractions. The SafTest Percent Fat measures fat content as "total triglycerides" in solubilized snack products and meals using micro-analytical and membrane separation principles. The study objective is to validate the SafTest Percent Fat in an internal study and an independent laboratory study. Comparability to AOCS Standard Procedure Aa 4-38 or AOCS Standard Procedure Am 5-04, LOQ, selectivity, robustness, stability, and consistency were determined. Mean recoveries from replicate analyses of SafTest control samples at three concentrations yielded 101 to 103%. The relative standard deviations of repeatability (RSDr) were below 5%. Studies of meat meals and snacks analyzed using the SafTest Percent Fat demonstrated RSDr of 2.3 to 5.6% compared to 2.6 to 4.9% for AOCS Aa 4-38. The method demonstrated average recoveries ranging from 88.8 to 116.2% compared to the AOCS methods results performed in two contract laboratory studies and an independent laboratory validation. The SafTest Percent Fat test can determine fat content in meals and snack matrices with accuracy and precision comparable to results from AOCS Aa 4-38 and AOCS Am 5-04. The SafTest Percent Fat test uses small reagent volumes, instrumental analysis, easy-to-use standardized procedures, and rapid analysis times for fat content determination.

A New Method for Determining Free Fatty Acid Content in Edible Oils by Using Electrical Conductivity

In the current study, a new method for determining free fatty acid (FFA) content in edible oils has been developed based on the electrical conductivity (EC) value change of a 0.04 M potassium hydroxide (KOH) solution during KOH–FFA mixed reaction. At ambient temperature, 4.000 ± 0.001 g of edible oils (oils with a high melting point were melted first) was dispersed in 40.0 ± 0.1 ml of KOH solution. The mixtures were stirred for 5 s and were held for 5 min. The EC value changes of the KOH solution layers were determined, and the FFA was predicted basing on the calibration. The analytical conditions studied include the concentration of KOH solution, holding time, the types of edible oils, setting temperature, and the ratio of oil to KOH solution (m/v). The calibration was validated by using the American Oil Chemists’ Society (AOCS) titrimetric FFA method. The analytical conditions were found to have no significant effects on the results. When the ratio of oil to KOH solution was 1:10 (m/v), the calibration was y = 12.04x−0.0769 (where x is the EC value change and y is the FFA content), R = 0.9992, SD = 0.0745, and a calibration with an SE of <0.0745 % FFA over a range of 0 % to 5 % was obtained. The method was validated using standard addition and the AOCS method. The results show that the analytical performance of the EC procedure is as good as or better than that of the AOCS titrimetric procedure.

Rapid Method for the Determination of Moisture Content in Biodiesel Using FTIR Spectroscopy

AbstractA new, rapid, and direct method was developed for the determination of moisture content in biodiesel produced from various types of oils using Fourier transform infrared (FTIR) spectroscopy with an attenuated total reflectance (ATR) element. Samples of biodiesels used in this study were produced using sludge palm oil (SPO). The calibration set was prepared by spiking double‐distilled water into dried biodiesel samples in ratios (w/w) between 0 and 10% moisture. Absorbance values from the wavelength regions 3,700–3,075 and 1,700–1,500 cm−1, and the partial least square (PLS) regression method were used to derive a FTIR spectroscopic calibration model for moisture content in biodiesel samples. The coefficient of determinations (R2) for the models was computed by comparing the results obtained from FTIR spectroscopy against the values of the moisture concentrations (%) determined using the American Oil Chemists’ Society (AOCS) oven method Ca 2d‐25. Same comparison was done using International Union of Pure and Applied Chemistry (IUPAC) distillation method 2.602. R2 was 0.9793 and 0.9700 using AOCS and IUPAC methods, respectively. The standard error (SE) of calibration was 1.84. The calibration model was cross validated within the same set of samples, and the standard deviation (SD) of the difference for repeatability (SDDr) and accuracy (SDDa) of the FTIR method was determined. With its speed and ease of data manipulation, FTIR spectroscopy is a useful alternative method to other methods for rapid and routine determination of moisture content in biodiesel for quality control.

Proposed Modifications to AOAC 996.06, Optimizing the Determination of Trans Fatty Acids: Presentation of Data

The increased focus on the accuracy of trans fatty acid data generated using current methodologies has resulted in research initiatives to optimize the quality of these assays. In this study, scientists combined the established methodology from AOAC 996.06 and the American Oil Chemists Society method Ce 1h-05, as well as other independent research. As a result, method modifications are proposed that could allow for a more accurate determination of trans fat than the current AOAC 996.06 method. Validation data from this study are presented. The authors encourage peer review and offer to facilitate a collaborative validation to update AOAC 996.06.

Development of Monoclonal Antibody-Based Enzyme-Linked Immunosorbent Assay for Gossypol Analysis in Cottonseed Meals

A monoclonal antibody-based indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) was developed for the analysis of gossypol in cottonseed meals. First, the checkerboard method was used to determine the optimum amount of coating antigen gossypol-BSA (bovine serum albumin) and primary anti-gossypol monoclonal antibody (Mab) needed in the ic-ELISA. Second, the effects of several physical (incubation time and temperature) and chemical (solvent types and concentrations) conditions on the performance of Mab on ic-ELISA were investigated to get a rapid robust assay with high sensitivity. Under the established optimized condition, the concentration of gossypol giving 50% reduction of the maximum ELISA signal (I50) in the competitive standard curve was 0.20 microg/mL, whereas the detection limit for gossypol was 0.024 microg/mL. This ic-ELISA method for the analysis of gossypol extracted by methanol from a variety of cottonseed meals was further compared with the official method of the American Oil Chemists' Society (AOCS). The amounts of gossypol determined by the ic-ELISA had a good correlation with those obtained by the AOCS method (R2 = 0.90).

Calculation of iodine value from measurements of fatty acid methyl esters of some oils: Comparison with the relevant American Oil Chemists Society method

AbstractA new calculation method for the determination of iodine value (IV) from measurements of fatty acid methyl esters is proposed. The method is based on the quantitative determination of fatty acid methyl esters of vegetable oils by capillary gas chromatography. IV is a measure of the number of double bonds in the unsaturated fatty acids in one gram of oil. The analytical methodology of its evaluation includes the use of rather health dangerous reagents, and for that reason is mostly avoided by laboratory analysts. A calculation procedure to determine the IV of oils from their fatty acid methyl ester composition is in use based on the American Oil Chemists’ Society (AOCS) method Cd 1c‐85. A new calculation procedure for IV, based also on the evaluation of the fatty acid methyl esters of oils, was developed. The application of the proposed calculation methodology was checked with olive oil, corn oil, soybean oil, cottonseed oil, and sunflower seed oil. The proposed calculation gave results in better agreement with the Wijs method than with the relevant AOCS method.

BIODIESEL PRODUCTION VIAACID CATALYSIS

Vegetable oils and animal fats can be transesterified to biodiesel for use as an alternative diesel fuel.Conversion of low cost feedstocks such as used frying oils is complicated if the oils contain large amounts of free fattyacids that will form soaps with alkaline catalysts. The soaps can prevent separation of the biodiesel from the glycerinfraction. Alternative processes are available that use an acid catalyst. The objective of this study was to investigate theeffect of process variables on acid-catalyzed transesterification. The molar ratio of alcohol, reaction temperature, catalystamount, reaction time, water content, and free fatty acids were investigated to determine the best strategy for producingbiodiesel. Food grade soybean oil was used to prepare esters using excess methanol and sulfuric acid as a catalyst. Tocompare the effect of different alcohol types on ester formation, methanol, ethanol, 2-propanol, and n-butanol werecompared. The American Oil Chemists Society Method Ca 14-56 was used to measure the biodiesels total glycerinamount as an indicator of the completeness of the reaction. It was found that acid catalysis can provide high conversionrates but much longer times are required than for alkaline catalysts. The acid catalyst also requires the concentration ofwater to be less than 0.5%, which is about the same as is required for alkaline catalysts. Water formed by theesterification of free fatty acids limited their presence in the oil to 5%.

Stoichiometric Determination of Hydroperoxides in Oils by Fourier Transform Near-Infrared Spectroscopy

Abstract A rapid Fourier transform near-infrared (FT-NIR) spectroscopic method was developed for quantitative determination of the peroxide values (PVs) of edible oils. The method is based on the stoichiometric reaction of triphenylphosphine (TPP) with hydroperoxides to produce triphenylphosphine oxide (TPPO). Calibration standards were prepared by adding randomized amounts of TPPO and TPP to peroxide-free high-erucic-acid rapeseed (HEAR) to produce a calibration matrix spanning the concentrations of TPPO and residual TPP in oils having PVs in the range 0-100 after complete reaction of the hydroperoxides with added TPP. A partial-least-squares (PLS) calibration model for predicting PV was developed by using the NIR spectral region from 4710 to 4540 cm-1, where TPP and TPPO both absorb. The resulting PLS calibration was linear, the cross-validation having a standard deviation (SD) of 1.36 PV over the analytical range. The method was validated by comparing the PLS-predicted PVs of oils spiked with tert-butyl hydroperoxide (TBHP) and those of naturally oxidized HEAR oils with the results obtained by using the American Oil Chemists’ Society (AOCS) iodometric procedure. The FT-NIR PV method correlated very well (SD = 1.20) with the reference AOCS method for TBHP-spiked oil samples. Similar results were obtained for naturally oxidized HEAR oil, with a standard deviation of the difference for reproducibility of ±1.11 PV for both methods. The analysis consists of adding about 0.04 mL TPP stock solution to 1 g oil, shaking, recording the spectrum, and using the PLS calibration to predict PV. Because of its simple and rapid stoichiometric reaction and its excellent correspondence to the iodometric method, the FT-NIR method provides a simple and alternative means of measuring PV. The FT-NIR method avoids the solvent and reagent disposal problems associated with the AOCS method and can be readily auto mated by appropriate programming of the FTIR spectrometer. Thus, it provides a simple and rapid analytical technique for determining PVs of fats and oils.

High‐performance liquid chromatographic separations of soy phospholipids

AbstractHigh‐performance liquid chromatography methods to quantitate soy phospholipids vary as to which phospholipids are analyzed, degree of method ruggedness, precision, time, and standards. Fluid and deoiled soy lecithins were analyzed by three different high‐performance liquid chromatography methods, including the American Oil Chemists’ Society (AOCS) Method Ja 7b‐91. The other methods include an isocratic mixed phase (normal‐phase column and reverse‐phase solvent) method with ultraviolet detection, and a binary gradient normal‐phase (proposed International Lecithin and Phospholipid Society) method with light‐scattering detection. A set of 20 analyses were repeated on three different days for fluid and deoiled product by the three methods. The statistical comparison involved the selected methods and the phosphatidylcholine and phosphatidylethanolamine measured data, which were the common analytes among the methods. The precision for the mixed phase method and the Proposed International Lecithin and Phospholipid Society method was better than that for the AOCS method. Selection of reference standards was an important issue in defining the results. Column conditioning varied by 2–3 h for the Proposed International Lecithin and Phospholipid Society method, 16 h for the mixed phase method, and 2–3 d for the AOCS method. The ruggedness for the methods showed the following descending order: proposed International Lecithin and Phospholipid Society, mixed phase, AOCS.

An improved phosphorus assay for oils without carcinogenic hydrazine sulfate

AbstractAn improved spectrophotometric method for phosphorus determination in oils is proposed. The proposed new method has made significant improvements in safety, sensitivity, and efficiency in comparison with the current American Oil Chemists’ Society (AOCS) Official Method (Ca 12–55, corrected 1992). The AOCS method employs hydrazine sulfate as the reducing agent to generate molybdenum blue. Hydrazine sulfate is a known carcinogen in laboratory animals and a suspected human carcinogen. The chemical also irritates skin and mucous membranes. In the improved method ascorbic acid is used as the reducing agent. Ascorbic acid is equally effective as hydrazine sulfate for the color reaction. The improved method is approximately 75 times more sensitive than the AOCS method. The sensitivity is improved by measuring absorbance at the absorption peak, 825 nm, and reducing the final volume of reaction mixture for color reaction. The AOCS method determines phosphorus by measuring absorbance at 650 nm, which is about 40% of that at the absorption peak. The efficiency of this improved method is also significantly increased by reducing sample size and the volumes of sample preparation. Therefore, the improved method is more cost‐effective than the AOCS method because less chemical reagents and smaller glassware are used, and the hazardous chemical waste disposal cost is eliminated. The improved method also avoids concentrated HCl and 50% KOH for sample preparation.

Comparison of Methylation Methods for the Quantitation of Conjugated Linoleic Acid Isomers

Abstract Four methylation methods were evaluated for use in the gas chromatographic (GC) quantitation of conjugated linoleic acid (CLA) isomers, which are potential anticarcinogen. The methods were (1) sodium methoxide in methanol (NaOMe-MeOH), (2) American Oil Chemists' Society (AOCS) procedure Ce 2-66, which involves methanolic sodium hydroxide followed by boron trifluoride in methanol, (3) tetramethylguanidine in methanol (TMG-MeOH), and (4) direct transesterification with methanolbenzene- acetyl chloride (DAC). Purified methyl esters of isomerized linoleic acid containing 86% CLA isomers were methylated and analyzed by GC. The AOCS and DAC methods resulted in 3 and 50% losses in cis-9,trans-11-octadecadienoic acid (9c, 111 CLA isomer) and trans-10,cis-12 octadecadienoic acid (10t, 12c CLA isomers), respectively. Compared with the control, the AOCS and DAC methods increased the yield of the trans,trans CLA isomers (trans-9,trans-11- and trans-10, trans-12-octadecadienoic acid) by 1.07-fold and a 10-fold, respectively. A non-CLA artifact that eluted close to CLA peaks was formed during methylation by the AOCS and DAC methods. Thus, the DAC and AOCS methods are not suitable for quantitation of CLA isomers. The NaOMe-MeOH and TMG-MeOH methods, however, are suitable for quantitation of CLA isomers in fats containing low concentrations of free fatty acids.