A simple and rapid method was developed for measuring the degree of rancidity in food fat. At first, the oil-bearing food was immersed in benzene, and the oil in the food was extracted. During this extraction, volatile carbonyl compounds moved to the solvent. A part of the benzene extract was transfered to a distillation apparatus. Then, the solvent was distilled off. Most of volatile carbonyl compounds from the food fat were also evaporated with benzene and collected in the distillate. The amount of carbonyl compounds condensed in the distillate was determined by converting the carbonyls into their 2, 4-dinitrophenylhydrazones and then measuring the absorbance of the wine-red color of quinoidal ions. In this report, this procedure was applied to aged fried rice crackers as follows. The rice crackers were fried with soybean oil, corn oil, and lard at 240°C as well as with these oils that had been heated at 240°C for 2 h. Then, these fried rice crackers were aged under various conditions, such as in dark at 35°C and 62°C, and in light at 25°C. The development of rancidity in these fried rice crackers was measured by sensory evaluation by an experienced panel and chemical tests such as the measurement of peroxide value, carbonyl value, and this carbonyl value of volatile carbonyl compounds. The results showed the best correlation between the volatile carbonyl values and flavor score. The merit of volatile carbonyl value of volatile carbonyl compounds for measuring the degree of rancidity was discussed.
Several problems about the volatile carbonyl compounds separated with “benzene distillation method” were investigated. Volatile carbonyl compounds separated with “benzene distillation method” from rancid rice crackers fried with soybean oil or lard were converted to their 2, 4-DNPH and identified with mainly TLC. The presence of the C2, C3, and C6 aldehyde was found in the distillates from benzene extract of the rice crackers fried with soybean oil or lard. The presence of C5 and C4 aldehydes was observed in the distillate from lard. The most abundant compound in the two groups was C6 aldehyde. The recoveries of volatile carbonyl compounds with “benzene distillation method” were determined. Head space vapors on rancid oils were gas-chromatographed. The results were compared with that on volatile carbonyl compounds separated with “benzene distillation method”. To improve the recoveries of carbonyl compounds especially C6 aldehyde, the solvents having higher boiling points than benzene were examined. Heptane seemed to be suitable for this purpose.
The reaction of 1, 2-epithiodecane with acetic anhydride in the presence of pyridine, triethylamine, and tributylamine gave S-(2-acetoxydecyl) thioacetate (1), 2-(acetylthio)decyl acetate (2), and S-[2-(acetylthio)decyl] thioacetate (3). Formation of bis(acetylthio)-compounds such as (3) had not been reported in the reaction of epithio-compounds with acetic anhydride. The ratio of the yields of (1), (2), and (3) was changed with reaction temperature, reaction time, amount of pyridine, and molar ratio of 1, 2-epithiodecane and acetic anhydride, but was independent of kinds of amines. The reaction of 1, 2-epithiooctane, 1, 2-epithiododecane, and 1, 2-epithiotetradecane with acetic anhydride in the presence of pyridine gave similar results described above. Higher selectivity to form the compound corresponding to (2) was observed in the reaction of 1, 2-epithiodecane with butyric and isobutyric anhydrides than with acetic anhydride. The reaction is presumed to be attack of carbonium ions of epithio-compounds activated by pyridine to acid anhydrides.
The authors studied on the antifoaming properties of vicinal glycols which were different in chain length and the position of neighbouring hydroxyl groups. 1, 2-Hexane-, 2, 3-hexane-, 3, 4-hexane-, 1, 2-octane-, 2, 3-octane-, 3, 4-octane-, 4, 5-octane-, 1, 2-decane-, 2, 3-decane-, 3, 4-decane-, 4, 5-decane-, 5, 6-decane-, 1, 2-dodecane-, 2, 3-dodecane-, 3, 4-dodecane-, 4, 5-dodecane-, 5, 6-dodecane-, and 6, 7-dodecanediols were derived from the corresponding olefins, which were prepared by the Wittig reactions, by the hydroxylation with hydrogen peroxide or potassium permanganate, or by the Meerwein-Ponndorf reduction of acyloins. The antifoaming power of these glycols was evaluated by the Ross and Miles method for the aqueous solutions of sodium dodecylbenzenesulforate, benzylhexadecyldimethylammonium chloride or p-nonylphenyl poly(oxyethylene) ether (n=15) as foaming agents. The results were expressed as immediate reading of foam height and reading of foam height after 5 min as a function of concentration of diols. From the results summarized in Fig.-1Fig.-16, it is evident that 5, 6-dodecanediols are superior to octanol, a commercial antifoaming agent, and comparable to silicone antifoamers. The antifoaming power of the glycols is larger when the two hydroxyl groups are located near center of the alkyl chain, but the symmetrical glycols where two hydroxyl groups centered on the alkyl chain are not so good.
The following two types of semipolar organoboron surfactants were prepared by esterification of fatty acids with di glycerol borate-ethylene oxide adducts which were made under Lewis acid catalyzed condition. The bound state between acyl group, polyoxyethylene group and di glycerol borate residue in above surfactants was confirmed by IR, NMR and potentiometric titration analysis. Average additional moles and distribution of polyoxyethylene groups were suggested by GPC, TLC and potentiometric titration data of di glycerol borate-ethylene oxide adducts. Addition reaction mechanism of ethylene oxide to di glycerol borate was especially discussed int hese synthetic process. On the other hand, it was found that type 1 was completely soluble in water and had better surface tension lowering ability than Tween and PEG fatty monoesters.