Chemical and organoleptic properties of oxidized fats

Various commercial fats were oxidized at elevated temperatures, and the extent of off-flavor development was evaluated organoleptically. Objective test methods also were applied to these oxidized fats, and correlations were established between the data and flavor panel results. Good to excellent correlations were obtained with pentane values, oxygen absorption values, peroxide values, and the average flavor scores. Results with the benzidine and thiobarbituric acid spectrophotometric methods were unsatisfactory. The octanoic acid method was found to be too insensitive to be of value. An exception to the above observations was lard, in which case all of the objective test methods gave good correlations with the flavor panel data. Presented at the AOCS Meeting, New Orleans, April 1973.     

An instrumental method for measuring the degree of reversion and rancidity of edible oils

Summary The amount of volatile carbonyl compounds diffused from 100 g. of an oil into a stream of nitrogen bubbled through the oil under specified conditions was determined by converting the carbonyl compounds into their 2,4-dinitrophenylhydrazones and then measuring the absorption of the wine-red color of the quinoidal ions at 480 mμ. From the absorbance thus obtained, a carbonyl index was calculated and assigned to the oil. The carbonyl indices of a number of edible oils, such as soybean, cottonseed, and hydrogenated vegetable, were found to correlate with the degree of reversion and rancidity of the oils as determined by organoleptic means. The reproducibility of the carbonyl index determination was 3%. This accuracy corresponded to approximately ±0.1 point in an organoleptic testing panel in which 1 point represented a very unacceptable oil and 10 points a very good oil. The carbonyl index method may also be used as a means of evaluating the flavor stability of edible oils. The carbonyl index gave a good indication of the flavor stability after aging at 60°C. for the less stable and 100°C. for the more stable oils and fats. Funds for this study were furnished by a grant-in-aid from Swift and Company, Chicago, Ill. Presented at the American Oil Chemists’ Society meeting, Minneapolis, Minn., Oct. 11–14, 1954.     

Photooxidation of Benzo[ de ]naphtho[2,1,8,7- stuv ]anthra[2,1,9,8- hijkl ]pentacene

This article describes the photooxidation of benzo[ de ]naphtho-[2,1,8,7- stuv ]anthra[2,1,9,8- hijkl ]pentacene (BNAP) synthesized by the condensation of naphthanthrone with zinc dust. When an o -dichlorobenzene solution of BNAP was irradiated with light of its maximum absorption wavelength (535 nm), the original absorption band was reduced and a new band appeared at longer wavelengths showing a peak at 606 nm. Excitation of the photobleached sample with 600 nm gave rise to fluorescence on the red side of that of BNAP by about 90 nm. The new fluorescence spectrum showed a vibrational progression of about 1,600 cm m 1 , which corresponds to the stretching of a carbonyl group. No spectral changes occurred in degassed solution. These findings suggest that BNAP reacts with singlet oxygen to form a ketone. Molecular orbital calculations revealed that the carbonyl group of the product is located at the C-18 position and that a hydroxy group is also present at the C-2 position; therefore the product is predicted as 2,18-dihydrobenzo[ de ]-naphtho[2,1,8,7- stuv ]anthra[2,1,9,8- hijkl ]pentacen-18-one.     

Amino-hexose-reductones as antioxidants. I. Vegetable oils

Summary Amino-hexose-reductones were evaluated as antioxidants in soybean, cottonseed, and corn oils and were shown to be highly effective by all oxidative and chemical tests. The activity of the eight different reductones was approximately the same in any one substrate. Slightly higher activities were given by reductones of lower molecular weight. Activity was demonstrated at concentrations as low as 0.001% and was shown to be a linear function of the concentration up to 0.02%, the approximate limit of solubility. Out-standing features of the reductone-treated oils were long induction periods, slow absorption of oxygen, and low rates of peroxide development. Reductones are believed not to react directly with peroxides but to prevent peroxide formation by reacting with some precursor. The combination of reductones with other antioxidants showed synergistic effects in only one sample of corn oil. The activity of combinations in soybean and cottonseed oils was for the most part strictly additive. In soybean oil, citric acid-reductone combinations with each at the 0.01% level gave a slight improvement over the expected activity. Oils stabilized with multiple-component, antioxidant mixtures in which an amino reductone replaced propyl gallate showed less peroxide development and were equally acceptable according to organoleptic scores. Aged oils did not show the organoleptic improvement that would be expected from the marked improvement observed in the oxidative stability. Significant improvements in flavor stability could be observed with reductones only when they were used in combination with an-other antioxidant. Reductone-treated soybean and cottonseed oils did not show an appreciable improvement in flavor stability. Only the di-n-butylamino-and diallylamino-reductones contributed foreign flavors to the oil. Atypical flavors are believed associated with the amine moiety of the reductone. At high temperatures and at higher concentrations of reductones a brown melanoid color develops in the oil. The anhydro derivatives developed more color than the normal reductone. The reductones do not withstand oil deodorization conditions. Presented at the meeting of the American Oil Chemists' Society, Chicago, Ill. September 23–26, 1956.     

Effect of autoxidation prior to deodorization on oxidative and flavor stability of soybean oil

Summary Oxidation prior to deodorization was shown to be detrimental to the flavor and oxidative stability of soybean oil. The increase in the nonvolatile carbonyl content of freshly deodorized oils was proportional to the peroxide value of the oils before deodorization. Rate of loss of flavor and oxidative stability of the oil were related to the extent of carbonyl development. All oils, whether or not they had been submitted to any known oxidation, contained some nonvolatile carbonyls. The loss in stability was not due to a loss of the antioxidant tocopherol. Oxidized soybean oil methyl esters were shown to develop nonvolatile carbonyl compounds upon heating at deodorization temperatures. The addition of isolated methyl ester peroxide decomposition products to deodorized soybean oil reduced its flavor and oxidative stability in proportion to the amount added. The results obtained were parallel and similar to those obtained by oxidizing soybean oil prior to deodorization. Flavor deterioration and undesirable flavors were typical of aging soybean oil whether or not the oils were oxidized before deodorization or whether an equivalent amount of nonvolatile thermal decomposition products was added to the oil. These oxidatively derived, nonvolatile carbonyl materials are believed to enter into the sequence of reactions that contribute to flavor instability and quality deterioration of soybean oil. The structure of these materials is not know. This work indicates the importance of minimizing autoxidation in soybean oil particularly before deodorization to insure good oxidative and flavor stability. Presented at fall meeting, American Oil Chemists’ Society, October 20–22, 1958, Chicago, Ill. This is a laboratory of the Northern Utilization Research and Development Division, Agricultural Research Service, U. S. Department of Agriculture.     

Oxidation and quality of soybean oil: A preliminary study of the anisidine test

The anisidine test, a measure of secondary oxidation products in glyceride oils, was applied to a number of soybean salad oils processed from sound and damaged soybeans. A highly significant correlation (−0.68) was found between the anisidine values of salad oils from sound soybeans and their flavor scores. Multiple correlations between flavor scores, anisidine, and peroxide values yielded a correlation of 0.81 and provided a method for predicting the initial flavor scores of sound soybean salad oils. Similar data for oils from damaged beans gave a highly significant, but lower, correlation (−0.65). Comparative studies indicated that sound crude oils usually contain lower levels of oxidation products than damaged crude. Oxidation in both sound and damaged crudes increased roughly in proportion to iron content. Reproducibility of the test and the effects of hydrogenation, accelerated storage, and fluorescent light on anisidine values were studied. Analysis of damaged oils before and after deodorization showed that little, if any, reduction of anisidine value occurred. Deodorization of sound oils, however, lowered anisidine values. In comparison with damaged oils, the anisidine values of sound oils were lower at comparable stages of processing. The poor quality of damaged soybean oil was substantiated by organoleptic evaluations. Flavor scores of oils given special processing treatments increased as anisidine values decreased.     

Effect of water activity on secondary products formation in autoxidizing methyl linoleate

The role of water activity on the formation of peroxides and carbonyl compounds during lipid oxidation is important to know because there could be either beneficial or detrimental effects of water activity on lipid oxidation in stored foods. Therefore, methyl linoleate was chosen as a model lipid and was autoxidized to 1% at water activity ranging from 0.02 to 0.79 at 37°C. Oxygen uptake was monitored manometrically. The peroxide and carbonyl contents were determined upon termination of the autoxidation studies. Methyl linoleate autoxidation was characterized by three phases: i) an initial induction period of no oxygen absorption; ii) a slow rate of oxygen absorption, up to 0.15% oxidation; and iii) a relatively faster rate of oxygen absorption beyond 0.15% up to 1% oxidation. Water activity had considerable influence during the first phase. There was no induction period at or below water activity 0.22. The induction period begins at water activity 0.32 and could be extended to a limit with increase in water activity. Once the induction period was passed water activity had no influence on the rate of oxidation. However, during the second and third phases water activity becomes important in the stabilization of peroxides/hydroperoxides and decides the course of secondary reactions that follow peroxide decomposition. Higher water activity values, particularly water activity 0.67, tended to stabilize peroxides. Water activity had considerable influence on the formation of secondary products of autoxidation as evidenced by the variation in the type and quantity of carbonyl compounds at different water activity values.     

Thermal oxidation of fractionated polypropylene in solution

Thermal oxidation of fractionated polypropylene was carried out in trichlorobenzene under atmospheric oxygen at 125°C with conventional oxygen uptake. The oxidizability of the polymers is discussed on the basis of the oxygen uptake curves and the properties of the polymers. Fractions of atactic polypropylene oxidized easily at the initial stage of the oxidation and showed neither autoxidation phenomena nor the induction period observed in the isotactic polymer. Hydrogenation of the ether-soluble fraction by a Wilkinson catalyst gave a polymer which was, according to infrared spectrometry, free from impurity groups such as hydroperoxide, carbonyl, and unsaturation groups. The hydrogenated fraction was more stable to thermal oxidation than the unhydrogenated fraction and showed an induction period. The results indicate that the initiation process of the oxidation of polypropylene is apparently dependent on the impurities such as hydroperoxide, carbonyl, and unsaturation and that stereoregularity of the polymer affects the kinetic dependence of the oxidation.     

Studies on the flavor of autoxidized soybean oil

The flavor components of soybean oil in the early stages of autoxidation were isolated by distillation in a molecular still. The distillate consisted of an aqueous layer and an oily film. The oily film did not reproduce the autoxidized flavor when added to freshly deodorized oil. Gas chromatographic and organoleptic analysis indicated that the oily film contained hexanal, vinylamyl ketone, andtrans,cis-2,6-nonadienal. The aqueous layer reproduced the autoxidized flavor when added to freshly deodorized oil, and the flavor had a retention time on butandiol succinate columns between those of pentanal and hexanal. Mixtures of vinylethyl ketone and pentanal gave a flavor to freshly deodorized oil similar to the flavor of oil in the early stages of autoxidation. Vinylethyl ketone was identified in the distillate from autoxidized soybean oil as the 2,4-dinitrophenylhydrazone. Presented at the AOCS Meeting, Minneapolis, 1963.     

Degradation of low‐density polyethylene during extrusion. VI. Effects of oxygen content in air gap

In our previous papers polyethylene degradation during extrusion coating has been studied and the type of degradation products that are formed and from which step they originate have been discussed. A trained sensory panel has rated the off‐flavor intensities in water samples that have been in contact with various extruded films. Encouraged by the results from these investigations and the documented synergism between aldehydes and ketones and aldehydes and carboxylic acids in off‐flavor intensity, the present study was aimed at confirming the belief that the off‐flavor depends on the presence of oxidative degradation products that have migrated from the film into the water. By decreasing the oxygen concentration in the atmosphere surrounding the extruded melt presence of the highly oxidized species (i.e., carbonyl compounds and carboxylic acids) would decrease and thus the off‐flavor in the water should decline. From this study it could be concluded that the extrusion temperature and the oxygen content in the atmosphere nearest the molten film before quenching are the most important parameters for oxidative degradation and residence time in the air gap influence the amount of oxidative degradation products formed. Furthermore we concluded that the off‐flavor intensity is strongly correlated to the surface oxidation index of the film. Carboxylic acids are present in the water extracts of extruded films and are related to the off‐flavor intensities. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1767–1775, 2005     

Solubility and esterification kinetics of terephthalic acid in ethylene glycol III. The effects of functional groups

Clear time (t_cl), the time required for the turbid mixture of terephthalic acid (TPA) and ethylene glycol (EG) to be clear, was measured to examine the effect of poly(ethylene terephthalate) (PET) prepolymer (DP of 1–5) on the kinetics of dissolution and/or ester-ification of TPA with EG. The t_cl of the mixture of TPA/EG (1 : 1.5 in molar ratio) was reduced to 1 : 2.2 or 1 : 3.5 by addition of 30 wt % of PET prepolymer or bis-(2-hydroxyl ethyl) terephthalate (BHET), respectively. Diethyl terephthalate (DET) as an addititive was used as a model compound to examine the effects of the —OH group on the esterification reaction of TPA/EG. The t_cl value increased with addition of DET. The effect of the carbonyl group was also examined by determining esterification rates of benzoic acid (BA) with either ethylene glycol monobezoate (EGMB) as a compound with carbonyl group, or 2-penoxyethanol (2-PhE) as a compound without the carbonyl group. The reaction rate of BA with EGMB was much higher than that of BA with 2-PhE, which indicates that the carbonyl group gave an increasing effect of the esterification rate. Fourier transform infrared spectra showed that the —OH group in both BHET and EGMB formed intramolecular hydrogen bonding with the ester carbonyl group. On the basis of these observations, we concluded that the electron density of oxygen in the hydroxyl group increased through the formation of the intramolecular hydrogen bond. The increased electron density gave the —OH group easier access to the carbonyl carbon in BA, leading to an increase in the esterification rate. © 1996 John Wiley & Sons, Inc.     

Oxidative degradation of polyolefins. I. Thermal oxidative degradation of atactic polypropylene in solution

Atactic polypropylene was oxidized in solution with radical initiator in the absence and presence of metal catalyst to considerably high conversion over the temperature range of 70° to 125°C, and oxidation products and the change in molecular weight distribution were measured. The unoxidized polypropylene had no ultraviolet absorption at 253.7 nm, whereas the oxidized polypropylene showed distinct absorption over a wide range of molecular weights. It was found that oxygen was incorporated into the polymer chain as hydroperoxide, acid, carbonyl, and hydroxy groups. Much of the absorbed oxygen was found to be involved in smaller fraction of low molecular weight products. Although the average molecular weight of the oxidized polypropylene decreased significantly, the formation of low-boiling products was quite small.     

Amaranth: a technological alternative in child nutrition

The relative high protein and oil content of amaranth grain and its relative high-protein quality are desirable characteristics to use it as a weaning food. Such a product was prepared with A. caudatus grain. Batches were processed without previous treatment of the grain, washed with water or with a bicarbonate solution. Processing consisted of cooking at atmospheric pressure for 10 min before passing the partially cooked grain through a double drum-drier heated with steam at 70 psi, and at a velocity of 3 rpm. Batches were also processed with the addition of strawberry flavor. All samples were analyzed for damaged starch and fluid characteristics using a 10% concentration, viscosity (by the Brabender amylograph), water absorption and retention, particle size, stability of the suspension, and soluble sugars. The different samples were organoleptically evaluated for acceptability, consistency, astringency, sweetness flavor and aroma, with a 20-member panel. A product with water or with milk and sugar was also evaluated. The results indicated that washing the grain prior to cooking increased the consistency of the product and eliminated the astringency of the grain. Washing also increased water absorption and retention, soluble sugars and the coefficient of consistency. all samples exhibited 100% damaged starch and had a pseudoplastic behavior. The raw grain flour gave a viscosity of 500 UB, while for the processed samples this value increased to 1,420 UB. In general, its acceptability on the part of the panelists was high. It was good for the product with strawberry flavor, but it was even better for the sample without flavor which had been previously washed. These results, as well as others reported on nutritive value, confirm the hypothesis regarding the use of processed whole grain amaranth as a weaning food.     

Studies on photodegradation of poly(vinyl chloride) (part 1)

Films prepared from emulsion polymerized poly(vinyl chloride) were subjected at 0°C to accelerated photodegradation in air using a weatherometer. Photooxidation and scission of the main chain took place but dehydrochlorination or formation of polyenes was not observed. The absorption of the carbonyl group indicating oxidation was found at 1725cm^?1 in the infrared absorption spectrum. Only when tetrahydrofuran, which had been used for the preparation of films, was left in the films, an absorption was also found at 1770cm^?1. Oxidation occurred at the position of the methylene carbon and the cut end of the main chain. As a result of the X-ray photoelectronic spectrum (ESCA) analysis, it was found that the carbonyl concentration was higher in the surface layer of the sample than in the interior thereof.     

Fe(Ⅲ)-EDTA吸收羰基硫动力学研究

<正>在合成氨原料气中,羰基硫(COS)占有机硫的80%左右,天然气中COS亦高达500ppm,为了经济有效地脱除COS,作者经过筛选实验发现乙二胺四乙酸络合铁(Fe(Ⅲ)-EDTA)可以脱除COS,故对Fe(Ⅲ)-EDTA吸收COS的动力学进行了研究,揭示了该过程的控制步骤,建立了其数学模型,并提出了对该方法进行改进的可行性方案.     

复合发酵剂对咸鱼风味品质的影响

金丝鱼经腌制后接种戊糖片球菌和木糖葡萄球菌,研究发酵对咸鱼风味的影响。实验表明:发酵可促进鱼肉中蛋白质的水解,提高咸鱼中小分子呈味物质的含量,降低pH,发酵终产品风味独特。采用GC-MS对产品挥发性风味成分分析表明挥发性羰基化合物及小分子酸类含量显著增加。     

Flavor evaluation of crude oil to predict the quality of soybean oil

Reliable methods for evaluation of crude oils are needed to assist processing and to improve flavor quality of finished products. The quality of crude oils from soybeans of different sources and treatments was determined by sensory evaluation and by capillary gas chromatographic (GC) analyses of volatiles. Taste panelists were specially trained in using a new technique to evaluate crude oils by dilution and comparison with freshly deodorized oils. The flavor quality of crude oils from untempered soybeans was significantly poorer than that of oils from soybeans steam-tempered at 104 C for four min. Capillary GC analyses of total volatiles and hexanal correlated well with differences in flavor quality and stability. Crude oils extracted from soybeans damaged by storage at 45 C and 13% moisture received decreasing flavor scores with prolonged storage time. Similarlly, hexanal and total volatile contents increased with storage times. Commercial crude oils from several geographic locations showed a wide range in flavor scores. However, flavor scores of crude oils showed good agreement with flavor stabilities (decrease in flavor scores after storage at 60 C) of the corresponding oils after refining, bleaching, and deodorization. Therefore, the combined use, of sensory evaluations and GC-volatile analyses of crude oils can provide convenient, rapid, sensitive and reliable screening methods to assist in improving the quality of finished soybean oils by controlling soybean storage and processing.     

A study of the flavor stability and autoxidation of beef fats

Summary The odoriferous compounds isolated from a fresh edible tallow were found to be very complex in nature and could not be diminished by treatment with carbonyl reagents. When these compounds were removed by deodorization, the bland tallow which was obtained developed on autoxidation another type of odoriferous compounds. The latter contained various carbonyl compounds of the type which have been associated with flavor reversion in edible oils. The characteristic odor of oleo oil and edible tallow could be removed by slight hydrogenation of high selectivity under atmospheric pressure. This hydrogenation process raised the melting point by less than 2°C. but substantially decreased the linolenic and arachiidonic acid content. The hydrogenated products, after deodorization, were not only bland in odor and flavor but also had flavor stabilities better than those of some of the best commercial shortenings. Funds for this study were furnished by a grant-in-aid from Swift and Company, Chicago, Ill. Presented at the American Oil Chemists’ Society meeting, Minneapolis, Minn., October 11–14, 1954.     

Studies on the morphology of blends of poly(vinyl chloride) and segmented polyurethanes

Solution-cast specimens of poly(vinyl chloride)/polyurethane (PVC/PU) blends were studied by means of infra-red, differential scanning calorimetry and dynamic mechanical measurements. Polyurethanes with polycaprolactone, poly(tetramethylene adipate), poly(tetramethylene oxide) and poly(propylene oxide) of the same molecular weight (1000) were used. The results indicate that it is possible to change the morphology of the blends significantly by proper selection of the structure of the soft segments. The polyester soft segments are more compatible with PVC than are the polyether ones. Hydrogen bonding of NH groups with the urethane carbonyl of the hard segments and with the ester carbonyl and ether oxygen of the soft segments was studied by applying a curve resolution technique to the NH and carbonyl stretching vibration absorption peaks of the blends. Information about the distribution of hydrogen bonding between the different acceptors was used to discuss the segregation and mixing of the hard and soft segments at different PVC contents of the blends. Morphological models were proposed for blends of different compatibility between PVC and the soft segments.