Relationships between the flavor evaluation procedure and objective chemical tests for measuring oxidative deterioration in stored food fats were investigated. These chemical tests involved the measurements of peroxide value, TBA test, and carbonyl value, parts of which were modified for simplicating the procedure. Fried rice cakes, which are typical fat-bearing foods in Japan, were chosen as the testing media. They were fried with soybean oil, safflower oil, olive oil, and lard at 240 °C respectively, as well as with these oils which had been heated at 240 °C for 2 h. Then these fried rice-cakes were aged under various conditions, namely, in dark at 24 °C, 38 °C and 60 °C, in light at 25 °C, and in sunlight at room temperature. The development of rancidity in these fried rice cakes was measured by means of chemical tests and sensory evaluation by an experienced testing panel. The results obtained by these chemical tests were correlated somewhat with the flavor scores. Especially carbonyl value based on 2, 4-dinitrophenylhvdrazone method showed a good correlation with the flavor score. Several weak points of these chemical tests employed in this report were discussed.
Neutral lipids and phospholipids were conveniently separated based on their degree of unsaturation by employing the chromatography on silica gel sintered rod impregnated with 12.5% silver nitrate. Individual lipid species separated on the rod were then quantified in situ with a flame ionization detector (thinchrography). Triglycerides were separated into the individual molecular species using benzene-diethylether (98 : 2, vol/vol) or benzene-chloroform-acetic acid (90 : 10 : 1, vol/vol) as the developing solvent system. The detector responses of tripalmitin, triolein and trilinolein on thinchrography were found to be proportional to the theoretical values based on weight percent. The method has been successfully employed to the analysis of eleven kinds of oils and fats. Each sample was shown to yield a characteristic chromatogram, indicating that this method might be useful for identifying the source of the oils or fats. Phosphatidylcholine and phosphatidylethanolamine were also separated into the individual molecular species by the same technique with chloroform-methanol-water (65 : 25 : 3, vol/vol) as the developing solvent system.
Mechanism for the formation of a solid solution and its modification phenomenon were examined in the binary systems of C18-C16, C18-C14, C18-C12, and C16-C14, using differential scanning colorimetry (DSC) and infrared (IR) spectroscopy. 1) Binary systems of C18-C16, C18-C14, and C16-C14 form continuous solid solution in either metastable state or stable state. At transition, they transit from sub-α and α-type solids to β-type solids, and this behavior was similar to that shown by 1-monoglyceride alone. C18-C12 system does not form a solid solution, and C18 and C12 were found to undergo transition independently. 2) Phase diagrams of C18-C16, C18-C14, and C16-C14 systems showed a similar pattern. Transition curve from sub-α to α-type was characteristic, the lowest temperature appeared at a specific composition ratio of the two components, and this temperature differed according to the composition ratio of the two camponents. Since C18 and C12 did not dissolve with each other, transition curves of C18 and C12 were different curves. 3) Transition rate was affected by the molecular chain length comprising the binary system, and became slower in the order of C18-C16, C18-C14, and C16-C14. The transition rate was the fastest in the case of short-chain monoglyceride containing 510% of longchain monoglyceride, but the rate becomes slower as the transition temperature from α to β-type becomes higher, so that, in general, the rate becomes faster with larger amount of short-chain monoglyceride contained in the long-chain monoglyceride, and became slower in the case of contrary.
Synthesis of zinc O, O-diisobutyldithio [35S] phosphate (ZDDP [35S]) was successfully carried out, using an exchange reaction between ammonium salt of O, O-diisobutyl-dithiophosphoric acid and elementary sulfur [35S]. The experimental tehnique and apparatus in this method are much simpler, therefore much safer, than the ordinary synthetic method where P235S5 is used. The ZDDP [35S] obtained was both chemically and radiochemically pure. The specific activity of the sulfur in ZDDP [35S] was 20.6% of that of the elementary sulfur [35S] used. According to this synthetic method, a satisfactorily high specific activity of ZDDP [35S], can be easily obtained.
GC analysis of the fatty acid composition of the oils containing short chain fatty acids has not been performed satisfactorily because of the loss of short chain methyl esters during the ester preparation procedure. The loss was supposed to be due to volatility and water solubility of these esters. The authors have worked on the simple and quantitative procedure for the preparation of esters from the oils containing short chain acids. It was confirmed that the loss of short chain esters could be avoided by preparing propyl esters with BF3-1-propanol reagent and washing the ester solution with 10.5% aqueous sodium chloride. Then the propyl esters prepared from the standard mixture containing from butyric to octadecanoic acids were analyzed by GC. The propyl esters were prepared by following procedure. Five tenths grams of the oil containing short chain fatty acids and 6 ml of 0.5 N sodium hydroxide in 1-propanol were introduced into an 100 ml flask. Then the mixture was refluxed about 10 min. Seven ml of 14% BF3 1-propanol reagent was added through the condenser and refluxed for 10 min. Then 5 ml of heptane was added and boiled for 1 min. After cooling to room temperature 100 ml of 10.5% aqueous sodium chloride was added to the flask, and the flask was shaken for 1 min. The heptane layer was transfered into a test tube and the aqueous solution was reextracted by 5 ml of heptane. The heptane solutions were combined and used as the sample for GC. It was found that the response of propyl ester in FID increased as the carbon number of fatty acid increased, although the rate of increase was not so large as that of methyl ester. So GC analytical value (area percent) must be corrected using the correction factor obtained through the analysis of standard mixture. Moreover, the corrected analytical value should be converted to the fatty acid composition, since the ratio of propyl moiety in the propyl ester does not respresent the fatty acid composition. The propyl and methyl esters of fatty acids were prepared from milk fat and fatty acid compositions were analyzed by GC.
Synthesis of methyl 4-isopropyl-7-methyl-5, 7-octadienoate (4) from readily available starting materials are described. Method A : Methyl 4-formyl-5-methylhexanoate (2) was prepared from the reaction of the piperidine enamine of isovaleraldehyde and methyl acrylate. A Wittig reaction between (2) and methallyli denetriphenylphosphorane in anhydrous tetrahydrofuran gave predominantly compound (4). Method B : A Wittig reaction of between 4-cyano-2-isopropyl butyraldehyde (3) and methallylidene-triphenylphosphorane gave 4-isopropyl-7-methyl-5, 7 - octadienenitrile (5). Hydrolysis of (5) under basic conditions gave a mixture of (4) and isomers of (4).