TLC-FID assessment of lipid oxidation as applied to fish lipids rich in triglycerides

Changes in the polar lipid content of fatty fish oils were studied by quantitative thin layer chromatography-flame ionization detection (TLC-FID) during an accelerated oxidation test. There was a direct linear correlation between increase in polar lipids and increase in weight of the oil samples. Comparison of increases in polar lipids with thiobarbituric acid values gave a hyperbolic correlation curve. However, a linear correlation was obtained in a semilogarithmic system. The simple and time-saving TLC-FID method for the analysis of the polar lipid content of oils as compared to a column chromatographic method suggests that this new method could be used in quality control of edible oils. Presented in part at the ISF/AOCS World Congress, New York City, April 1980.     

Fatty acid composition and oxidation of lipids in Korean catfish

This study determined the lipid content and FA composition of muscle and a mixture of muscle and viscera from Korean catfish as well as lipid oxidation and hydrolysis. Lipid content and FA compositions in Korean catfish, which were purchased every month or two during September 1999–July 2000, were analyzed. Lipid oxidation and hydrolysis were determined as PV, thiobarbituric acid value, and FFA in the muscle and the mixture during storage at 2°C for 12 d and −14°C for 9 wk. Lipid contents of the muscle and the mixture were 3.2 (w/w) and 5.4%, respectively. Oleic acid was the most abundant FA in the catfish lipids, constituting 28.0% (w/w) of total FA in the muscle and 25.6% in the mixture, followed by palmitic acid and linoleic acid, amounting to 20.2 and 12.2%, respectively, in the muscle and 20.2 and 12.5% in the mixture. EPA and DHA were 3.2 and 6.8%, respectively, in the muscle and 3.5 and 8.1% in the mixture. Seasonal variation in lipid contents and FA composition was minimal in catfish. Lipids in minced catfish oxidized and hydrolyzed readily at 2°C. Inclusion of viscera into the muscle increased lipid oxidation and hydrolysis. Frozen storage at −14°C and addition of ascorbic acid both reduced lipid oxidation. Frozen storage retarded lipid hydrolysis in catfish.     

Hydrolysis of acylglycerols and phospholipids of milled rice surface lipids during storage

The relative contribution of acylglycerols and phospholipids to the lipid hydrolysis in milled rice was investigated during storage at 37°C and 70% RH for 50 d. The MAG, DAG, and lysophospholipid contents of surface lipid were determined by reversed-phase HPLC. The MAG and DAG content of milled rice increased during storage from 0.06 to 0.18% (w/w milled rice), with the MAG content increasing more than that of the DAG. Lysophosphatidylcholine increased throughout the study from 0.013 to 0.034% (w/w), whereas lysophosphatidylinositol and lysophosphatidylethanolamine contents initially increased from 0.002 to 0.003% and from 0.005 to 0.009% (w/w), respectively, and then stabilized until day 50. The relative percentage of TAG and phospholipids hydrolyzed in milled rice increased rapidly during the first 3 d of storage from 12.3 to 37.6% and 25.0 to 62.5% (w/w), respectively, and steadily increased to 53.1 and 73.8% (w/w) on day 50. A higher percentage (62.5%) of phospholipids was hydrolyzed relative to TAG (37.6%) after 3 d and probably contributed significantly to milled rice lipid hydrolysis during early storage. However, TAG concentration (0.57%, w/w) was much higher relative to phospholipids (0.08%, w/w) in surface lipids, and therefore TAG hydrolysis was the major contributor to FFA development and the quality of stored milled rice.     

Effect of sprouting on the quality and composition of canola seed and oil

Sprouting has been considered as a damage factor in grading canola. This project deals with the evaluation of the effect of sprouting on the quality and composition of canola seed and oil. Sprouted seeds had lower oil content than nonsprouted seeds as determined by exhaustive petroleum ether extraction. The difference, although statistically significant, was small, less than 0.1% oil at the maximum level of sprouting allowed in topgrade canola. There were no differences in chlorophyll contents or moisture contents between sound and sprouted seeds. Sprouted seeds had significantly higher levels of FFA and crude protein than sound seeds. Oxidation parameters (diene and aldehyde) were higher in oils from sound seeds than oils from sprouted seeds, but there was no statistically significant difference in PV. Sprouted seeds had higher levels of tocopherols and sucrose, but lower levels of raffinose, stachyose, and total sugars than sound seeds. There was no difference in overall FA composition of the oil between sound and sprouted seeds. The second extraction of the Federation of Oils Seeds and Fat Associations (FOSFA) extraction method, which allowed the extraction of more polar lipids, contained significantly more saturated FA. However, this was not significant in the overall FA composition of the oils because this fraction counted for about 2% of the total lipid content. The presence of sprouted seed had an effect on results for oil and crude protein determined by NIR as compared with results by FOSFA extraction, or pulsed NMR for oil and Dumas combustion for crude protein. Addition of sprouted seed samples to the NIR, calibration set overcame this problem. These results suggested that sprouting did not have a highly damaging effect on the quality and composition of canola seed and oil when less than 10% of the seeds in a sample were sprouting.     

Rapid quantitative determination of free fatty acids in fats and oils by fourier transform infrared spectroscopy

Rapid direct and indirect Fourier transform infrared (FTIR) spectroscopic methods were developed for the determination of free fatty acids (FFA) in fats and oils based on both transmission and attenuated total reflectance approaches, covering an analytical range of 0.2–8% FFA. Calibration curves were prepared by adding oleic acid to the oil chosen for analysis and measuring the C=O band @ 1711 cm^–1 after ratioing the sample spectrum against that of the same oil free of fatty acids. For fats and oils that may have undergone significant thermal stress or extensive oxidation, an indirect method was developed in which 1% KOH/methanol is used to extract the FFAs and convert them to their potassium salts. The carboxylate anion absorbs @ 1570 cm^–1, well away from interfering absorptions of carbonyl-containing oxidation end products that are commonly present in oxidized oils. Both approaches gave results comparable in precision and accuracy to that of the American Oil Chemists’ Society reference titration method. Through macroprogramming, the FFA analysis procedure was completely automated, making it suitable for routine quality control applications. As such, the method requires no knowledge of FTIR spectroscopy on the part of the operator, and an analysis takes less than 2 min.     

Study on the composition of rice bran oil and its higher free fatty acids value

The compositions of rice bran oils (RBO) and three commercial vegetable oils were investigated. For refined groundnut oil, refined sunflower oil, and refined safflower oil, color values were 1.5–2.0 Lovibond units, unsaponifiable matter contents were 0.15–1.40%, tocopherol contents were 30–60 mg%, and FFA levels were 0.05–0.10%, whereas refined RBO samples showed higher values of 7.6–15.5 Lovibond units for color, 2.5–3.2% for unsaponifiable matter, 48–70 mg% for tocopherols content, and 0.14–0.55% for FFA levels. Of the four oils, only RBO contained oryzanol, ranging from 0.14 to 1.39%. Highoryzanol RBO also showed higher FFA values compared with the other vegetable oils studied. The analyses of FA and glyceride compositions showed higher palmitic, oleic, and linoleic acid contents than reported values in some cases and higher partial glycerides content in RBO than the commonly used vegetable oils. Consequently, the TG level was 79.9–92% in RBO whereas it was >95% in the other oils studied. Thus, refined RBO showed higher FFA values, variable oryzanol contents, and higher partial acylglycerol contents than commercial vegetable oils having lower FFA values and higher TG levels. The higher oryzanol levels in RBO may contribute to the higher FFA values in this oil.     

A highly sensitive method for the micro-determination of lipid hydroperoxides by potentiometry

A modified method for peroxide value (POV) determination of lipids was developed through the application of potentiometry to conventional POV tests such as the official method of the Japan Oil Chemists’ Society (JOCS). The new method permits a simple and reliable determination of low hydroperoxide levels in the initial stages of lipid autoxidation when only very small amounts of sample are available, even when those levels are measured on less than 10 mg of lipid. Using the present method, hydroperoxide levels as low as 20 nanoequivalents (neq) were determined with reasonable precision. This method is applicable to all lipids tested including oils and fats, free fatty acids, phospholipids, glycolipids and cholesterol esters.     

Effect of minimal neutralization at optimal conditions on minor components and oxidation stability of sunflower oil

In this study, oxidatively stable minimal neutralized sunflower seed oils were produced using three chemicals (Ca(OH)₂, MgO, and Na₂SiO₃) under previously determined optimal process conditions. Lipid oxidation rates at these optimum conditions were compared to the oils neutralized with NaOH (0.20%, 40°C, 15 min). It was concluded that the oils neutralized by NaOH had the shortest hydroperoxide and hexanal lag phases, thus were the least stable oils. Oils neutralized by Ca(OH)₂, MgO, and Na₂SiO₃ had lower FFA and higher oxidative stability than oil neutralized by NaOH. The study focused on which weak alkaline has higher oxidation stability and minimum FFA content and maximum acceptable tocopherol content. The oil neutralized by Ca(OH)₂ had the lowest FFA value and highest total phenolics and α-tocopherol contents and it had better oxidative stability than oil neutralized by NaOH. It suggests that Ca(OH)₂ could be more effective in producing a high quality oil.     

Quality assessment of industrial prefried french fries

An industrial production of prefried french fries using palm oil as a frying medium was studied over a period of 12 days. Samples of oils and french fries were withdrawn once a day. The quality of both the oil and the french fries was assessed using two types of tests. Some tests, such as the determination of free fatty acid (FFA) and the determination of thiobarbituric acid value (TBA), oxifritest and Food Oil Sensor correspond to what was used by a quality control laboratory. More elaborate techniques such as the determination of polar components, polymers and cyclic fatty acid monomers (CFAM) were also used. Only small increases of FFA, TBA, polar components and polymers were observed. However, in the case of palm oil, which contains a high percentage of diglycerides, it is more reliable to determine the quality of the oil using the amount of polymers instead of polar components which may include some diglycerides. Thus a high “polar components” value (up to 20–25%) would not necessarily reflect an altered sample. The maximum amount of CFAM detected was 0.1% and they did not seem to be preferentially adsorbed on the french fries. These results, along with the sensory evaluations, showed that the french fries obtained in these production conditions were of good quality as far as the fat was concerned.     

Rapid methods for determination of free fatty acids contents in fatty oils

Rapid qualitative and quantitative methods for determining the free fatty acid (FFA) contents in common oils and fats are reported. Qualitative method is based on the type of color developed in the presence of BDH indicators (Universal and “678”) when a known excess of alkali is added to an alcoholic solution of oil or fat. By this method, low (0.0–0.25), medium (0.26–0.99) and high (1.0 and above) FFA levels in fatty oils may be distinguished. Quantitative method is a simplified modification of the usual procedure of determining the FFA contents of oils and fats by titration against standard alkali solution in the presence of BDH Universal or “678” indicator. The results of the rapid methods agree well with those of the standard AOCS method.     

Influence of triacylglycerol characterics on the determination of free fatty acids in vegetable oils by fourier transform infrared spectroscopy

A rapid and direct Fourier transform infrared (FTIR) spectroscopic method using a 25-μm NaCl transmission cell was developed for the determination of free fatty acids (FFA) in six important vegetable oils (corn, soybean, sunflower, palm, palm kernel, and coconut oils) that differ in fatty acid profile. The calibrations were established by adding either standard FFA (oleic, lauric acids) or a representative mixture of FFA obtained after saponification of the refined oils. For all oils, up to a FFA level of 6.5% for coconut oil, the best correlation coefficient was obtained by linear regression of the free carboxyl absorption at 1711 cm⁻¹. All correlation coefficients were greater than 0.993, and no significant difference between the calibration methods could be detected. Upon validation of the calibration, no significant difference (α=0.05) between the “actual” and the “FTIR predicted” FFA values could be observed. The calibration models developed for the six oils differed significantly and indicate the need to develop a calibration that is specific for each oil. In terms of repeatability and accuracy, the FTIR method developed was excellent. Because of its simplicity, quick analysis time of less than 2 min, and minimal use of solvents and labor, the introduction of FTIR spectroscopy into laboratory routine for FFA determination should be considered.     

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

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.     

Lipid profile of process streams of palm oil mill

During palm oil extraction, oil loss occurs mainly at three stages of processing, namely sterilization, pressing and clarification. Samples from a semi-commercial palm oil mill were analyzed for their lipid composition (triacylglycerol, diacylglycerol, monoacylglycerol, free fatty acid, phospholipid and glycolipid contents and fatty acid compositions of these lipid classes) and compared with the end product,viz., raw palm oil. The results indicate significant variations between the samples with respect to oil quality and lipid profile. Data relating to the lipid classes showed that sterilizer condensate had the highest levels of free fatty acids (24%), followed by press fiber (12.5%) and sludge effluent (10.9%), as compared to raw oil (1.5%). Diacylglycerol and monoacylglycerol contents were also markedly higher for these streams. Press fiber was characterized by extremely high proportions of phospholipids and glycolipids. Distribution of fatty acids (16:0, 18:1, 18:2 and 18:3) also varied among lipid classes of the process streams, particularly between polar lipids. This paper discusses the compositional aspects of lipids relating to quality of oils of the palm oil mill streams.     

Rapid Determination of Degradation in Frying Oils with Near-Infrared Spectroscopy

Measures of free fatty acids (FFA), total polar materials (TPM), and conjugated dienoic acids (CDA), typical indices of oil degradation, were analyzed in daily oil aliquots taken from soybean oils with different linolenic acid concentrations used to fry French fries. The oils also were scanned with a reflectance near-infrared spectrometer using a wavelength range of 350–2,500 nm. By using partial least squares and one-out cross validation, calibrations were developed to quantitatively determine FFA, TPM, and CDA by near-infrared spectroscopy (NIRS). The coefficients of determination (R ²) when compared to the standard methods were 0.973 for FFA, 0.984 for TPM, and 0.902 for CDA. NIRS was an accurate and fast method to determine FFA, TPM, and CDA in oxidized oils. The ability to obtain different parameters simultaneously makes NIRS a potentially valuable tool for food quality assurance.     

Dietary Polyunsaturated Fatty Acids and Inflammation: The Role of Phospholipid Biosynthesis

The composition of fatty acids in the diets of both human and domestic animal species can regulate inflammation through the biosynthesis of potent lipid mediators. The substrates for lipid mediator biosynthesis are derived primarily from membrane phospholipids and reflect dietary fatty acid intake. Inflammation can be exacerbated with intake of certain dietary fatty acids, such as some ω-6 polyunsaturated fatty acids (PUFA), and subsequent incorporation into membrane phospholipids. Inflammation, however, can be resolved with ingestion of other fatty acids, such as ω-3 PUFA. The influence of dietary PUFA on phospholipid composition is influenced by factors that control phospholipid biosynthesis within cellular membranes, such as preferential incorporation of some fatty acids, competition between newly ingested PUFA and fatty acids released from stores such as adipose, and the impacts of carbohydrate metabolism and physiological state. The objective of this review is to explain these factors as potential obstacles to manipulating PUFA composition of tissue phospholipids by specific dietary fatty acids. A better understanding of the factors that influence how dietary fatty acids can be incorporated into phospholipids may lead to nutritional intervention strategies that optimize health.     

水和游离脂肪酸对DBU催化制备生物柴油的影响

以低品质油脂作为生产生物柴油的原料可以有效降低产品的成本。催化剂对原料油中主要杂质游离脂肪酸和水分的耐受程度决定了该工艺对原料油的适应性。本文采用有机碱1,8-二氮杂双环[5,4,0]十一碳-7-烯（DBU）催化酯交换反应制备生物柴油,研究了不同水和游离脂肪酸含量下酯交换反应的转化率、反应后产物两相的组成以及各组分在两相的分配。结果表明,DBU作为催化剂时,对水和游离脂肪酸具有较强的耐受性：水含量小于2%（质量分数,下同）,游离脂肪酸含量小于5%;1.5%左右的水对反应具有促进作用,水含量为1.5%时,酯交换转化率最高可达93.7%。此外,水和游离脂肪酸会降低甲醇、DBU在甲酯相中的分布,这使得甲酯相中甲酯的纯度有所上升。     

Relative FFA formation and lipid oxidation of commercially milled unseparated,head, and broken rice

This study was conducted to determine the relative rate of FFA formation and lipid oxidation of unseparated (head and broken), head, and broken rice and the effect of water washing on the lipid quality of broken rice. A regression model was developed with surface FFA or conjugated diene (CD) content vs. incubation time to determine the rates of FFA formation and lipid oxidation. The surface lipid contents of unseparated, head, and broken rice were 0.40, 0.38, and 0.50% of rice, respectively. FFA formation during storage showed three phases: an initial rapid formation, followed by a period of very little or no formation, and finally a phase of gradual formation. In contrast, CD formation initially showed a slow increase but later increased gradually with storage time. The relative rates of FFA and CD formation of unseparated, head, and broken rice were 0.0028, 0.0027, and 0.0036 and 0.192, 0.188, and 0.377, respectively. Water washing reduced the rates of FFA formation and lipid oxidation of broken rice to 0.0015 and 0.2192 from initial values of 0.0031 and 0.369, respectively. Water washing appears to be a simple and practical means of lowering the rates of FFA formation and lipid oxidation in broken rice.     

Influence of Enzymatic Remediation on Compositional and Thermal Properties of Palm Oil and Palm Oleins from Dry Fractionation

Characteristics of crude palm oil are high FFA and DAG contents. High DAG content may affect throughput and yield during fractionation: high‐grade specialty fats such as hard palm mid fraction require premium crude palm oil to secure adequate crystallization properties. Moreover, DAGs are generally considered the main precursors for the formation of glycidyl esters during high‐temperature deodorization. The purpose of this study was to investigate the effect of enzymatic remediation on the reduction of FFA and DAG in crude palm oil. In practice, series of process parameters (vacuum and reaction time) were investigated, and the quality of enzymatically remediated crude palm oils was examined in terms of FFA and DAG reduction, TAG composition, and SFC and DSC melting profiles. Fully refined enzymatically remediated palm oils were then dry fractionated. The quality of the oleins derived from the enzymatically remediated palm oil was compared to that of regular RBD palm oleins.     

Extraction of pollen lipids by SFE‐CO2 and determination of free fatty acids by HPLC

Rape bee pollen lipids obtained by petrol ether extraction (PEE) or supercritical fluid (carbon dioxide) extraction (SFE) were compared with regard to their free fatty acid (FFA) components. Optimal SFE conditions were selected by carrying out the Taguchi method with an OA9 (3³) matrix design, and are as follows: extraction pressure at 35 MPa, temperature at 45 °C, and dynamic extraction time at 90 min. The lipid yield based on PEE was 7.42 wt‐% and the extracts of the desired analytes based on SFE varied in the range of 3.23–5.58 wt‐% under different conditions. With the optimized procedure, the lipid yield was 6.09 wt‐%. The FFA in the lipids were separated with a pre‐column derivation method and 1‐[2‐(p‐toluenesulfonate) ethyl]‐2‐phenylimidazole [4,5‐f]9,10‐phenanthrene as labeling regent, followed by high‐pressure liquid chromatography (HPLC) with fluorescence detection. HPLC analysis shows that the lipids contain abundant unsaturated fatty acids (UFA) in high to low concentrations as follows: linolenic acid (18:3), oleic acid (18:1), linoleic acid (18:2), nervonic acid (24:1), and lignoceric acid (20:4). The UFA contents in the SFE extracts were higher than those after PEE. The results indicated that SFE under suitable conditions is more selective than conventional PEE with regard to lipid extraction and preservation of their quality.     

Effect of fatty acid composition of phospholipids on their antioxidant properties and activity index

Various phospholipids may act as antioxidants or prooxidants. This study investigated the effects of three phospholipid classes and their fatty acid composition on antioxidant activity. Antioxidant properties of sphingomyelin, phosphatidylcholine, and phosphatidylethanolamine from salmon and menhaden oil were measured by oxidation induction time. An antioxidant activity index was determined in these systems with the Rancimat 617. Fatty acid profiles of the individual phospholipids and total oils were determined by gas-liquid chromatography before and after oxidation. The index was significantly (P<0.05) influenced by the headgroup and fatty acid composition of the phospholipid. Lipids with a choline headgroup had oxidation induction times greater than 60 h in the salmon oil system. The choline-containing phospholipid also offered better (P<0.05) protection from oxidation to the n-3 and total polyunsaturated fatty acids in salmon oil. Phospholipids containing more saturated fatty acids had longer oxidation induction times (>84 h) and higher antioxidant index (>9). Chainlength of the fatty acids may have contributed to the observed index, as phospholipids with longer chains (i.e., C₁₈ and above) had longer oxidation induction times. Phospholipids tested in this study had little or no antioxidant activity in menhaden oil, nor did they offer protection to n-3 or total polyunsaturated fatty acids in this oil. These findings suggest that fatty acid profiles of individual oils may influence the antioxidant index of each phospholipid.