By gas chromatographic determination, the amount of free fatty acids, composition of fatty acids derived from glyceride and decomposition rate of fats in mackerel homogenates, individually inoculated with yeasts or bacteria and incubated at 25°C for 7 days, were investigated. The decomposition rate of fats was compared with total volatile basic nitrogen (TVB-N) production in the inoculated homogenates. The following results were obtained. (1) Candida lipolytica and Pseudomonas fluorescens had the highest decomposition rates of fats among the 5 yeast and 4 bacterial strains tested, respectively. The decomposition rates of fats by them were about 90% after incubation at 25°C for 7 days. (2) Free fatty acids released from glyceride by the yeast strains or the bacterial strains were of the same kind as the fatty acids present in glycerides, and so it was considered that the decomposition of fats mainly depended on cleavage of glycerol ester. (3) Fifteen to twenty-five percent of the released free fatty acids, especially unsaturated free fatty acids, were further decomposed. (4) The decomposition rate of fats by the test strains did not always correspond to the amount of TVB-N produced in the homogenates; for example, Bacillus subtilis formed a large amount of TVB-N but showed a small decomposition rate of fats.
The mutagenic activities and the amounts of heterocyclic amines in oil of charred egg yolk were investigated in order to estimate the carcinogenic risk to humans. Fresh egg yolk was roasted at 300-350° for 30min to get a black and oily material. The mutagenic activity of this material to Salmonella typhimurium TA98 with S9mix was 24 revertants/mg. The mutagenic material was further purified by 2N hydrochloric acid-ethyl ether partition, followed by blue cotton treatment. The mutagenic activities after these purification steps were 5, 108 and 16, 435 revertants/mg, respectively. Mutagenic and carcinogenic heterocyclic amines in the partially purified material were analyzed by a combination of high performance liquid chromatography using octadecylsilane and cation exchange columns, and four carcinogenic heterocyclic amines, Trp-P-1, Trp-P-2, AαC and MeAαC were detected. The contents of these heterocyclic amines were as follows: 4.3ng of Trp-P-1, 1.0ng of Trp-P-2, 6.1ng of AαC and 1.2ng of McAαC per one gram of oil of charred egg yolk. These compounds were estimated to account for only one percent of the mutagenicity of oil of charred egg yolk.
Identification of γ-irradiated grapefruit was investigated by observation of rooting and shooting of the grapefruit seeds. In order to reduce the incubation time for germination, indole-3-acetic acid (10ppm) and gibberellic acid (100ppm) were used to promote the rooting and the shooting, respectively. When incubated with the above plant hormones, a non-irradiated group started rooting in about a week after the incubation, and the root elongated with time, while an irradiated group (50krad) was slow in rooting and showed no emergence of roots with a length of 10mm or more. In 12 days, the emergence rates of roots with a length of 10mm or more in non-irradiated and irradiated groups were 30% and 0%, respectively. In 16 days, the emergence rates of the plumule in non-irradiated and irradiated groups were 20% and 0%, respectively. Thus, two features were critical for identification of γ-irradiated grapefruit: no emergence of a root with a length of 10mm or more, and no emergence of a plumule. This was also useful at low irradiation level, since the same phenomena were found in a grapefruit irradiated with 30krad. On the other hand, TTC activity in grapefruit seeds, used as a test of germination ability in cereal seeds, was not affected by γ-irradiation.
A high performance liquid chromatographic method (HPLC) is described for determining lasalocid sodium residues in chicken tissues. Lasalocid was extracted from tissues by homogenizing them with acetonitrile. The supernatant was washed with n-hexane saturated with acetonitrile, then applied to a Sep-pak silica cartridge. After evaporation, the residue was dissolved in methanol and determined by HPLC. Lasalocid was separated on a UNISIL PACK 5C18 column (4.6mm×25cm) by using a methanol-20mM phosphate buffer, pH 3.0 (9:1) as a mobile phase. Lasalocid was detected with a spectrofluorometer (excitation and emission wavelengths set at 310nm and 420nm, respectively). Recoveries of lasalocid sodium added to chicken muscles and chicken livers were in the ranges of 89.4-92.3% and 85.3-89.0%, respectively. The detection limit is 0.005ppm, which is adequate for residual analysis.
A rapid convenient method for the simultaneous determination of acesulfame K (AK), saccharin (SA) and aspartame (APM) in soft drinks by high performance liquid chromatography (HPLC) using an ion-pair partition system was developed. McIlvaine buffer, pH 4.5, and 0.1M tetrabutylammonium bromide were added to a sample and the solution was passed through Bond Elut C18. The column was washed with water, and the sweeteners were eluted with a mixture of methanol-McIlvaine buffer, pH 3.0 (3:7). The eluate was determined by HPLC with a Finepak SIL C18S column and a mobile phase of methanol-water (2:8) containing tetraethylammonium hydroxide, pH 4.0. The effluent was monitored with a UV detector at a wavelength of 210nm. By these procedures, the 3 sweeteners can be well separated and quantitatively determined. The recoveries of AK, SA and APM from soft drinks piked at 50 and 200μg/g were 95-102%, 93-104%, 90-102%, respectively. The detection limits of AK, SA and APM were 10mg/kg of sample.
A chemical method to evaluate decomposition in chum salmon (Oncorhynchus keta) and rainbow trout (Salmo gairdneri) was developed. Ethyloxycarbonyl derivatives of polyamines were formed from extracts of these fishes and separated by gas chromatograph with a flame ionization detector. The changes in contents of putrescine (Put), cadaverine (Cad), tyramine (Tym), tryptamine (Tpm), spermidine (Spd) and spermine (Spn) were examined in the meats of these salmonoid fishes during storage at 5°C and 10°C. The levels of Cad, Tym and Put increased as decomposition progressed, regardless of storage temperature. Of these three amines, Cad was the major product, and seemed to be most useful as an index for decomposition of salmonoid fishes; Cad was not detected or was present in only a trace amount (less than 1ppm) at the acceptable stage, 1 to 10ppm at the stage of initial decomposition and over 10ppm at the stage of advanced decomposition. Spn, Spd and Put were distributed in the muscle of live salmonoid fishes.
A simple and rapid method for the quantitative determination of nicotinic acid (NA) and nicotinamide (NAA) in meat was developed. Five grams of meat was placed in a beaker, 10ml of distilled water was added and mixed, and the beaker was placed in a boiling water bath for 5min. The mixture was filtered, after cooling with water. The filtrate was put in a 10ml tube and niacin test paper (NTP) was added. When NA or NAA had been added to the meat, the color of NTP changed to orange, and quantitation was done by comparison with standard colors. According to the results of market research, NA and NAA are added at levels of more than 100mg/kg to meat. Therefore, it is possible to judge by means of the NTP method whether NA or NAA has been added to meat or not.