We report results of quantitative analysis using a precolumn derivatization method for melatonin extracted from raw milk. The extraction method is described as follows.
The raw milk, obtained from 43-month-old Holstein cows, was incubated with papain at 45°C for 30 minutes. The enzyme reaction was stopped by the addition of trichloro acetic acid and then the reaction mixture centrifuged. The melatonin in the supernatant was extracted with chloroform, after which, the chloroform layer was washed with water and evaporated to dryness. For the derivatization of melatonin, 150μL of aqueous 2mol/L Na₂CO₃, 100μL 100mmol/L H₂O₂, 50μL 1mmol/L CuSO₄, and 700μL water were added to the residue, and the mixture was then heated in water (94-96°C) for 6 minutes. The melatonin derivative was extracted with ethyl acetate, evaporated to dryness, dissolved in aqueous 15% (v/v) CH₃CN, and then subjected to HPLC analysis. When standard melatonin was added to raw milk, the recovery rate was 85.3±7.3% (mean S.D. n=5). The 43-month-old Holstein cows were milked at noon and night, on January, February, and March 2006. In January, melatonin content in raw milk was determined to be 5.7pg/mL in diurnal milk and 42.3pg/mL in nocturnal milk. In February and March, melatonin content in nocturnal milk decreased to 22.3 and 14.8pg/mL, respectively. These results suggest that the present method is suitable for determination of melatonin contained in raw milk.

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This study aims to contribute to the product development of Kaburazushi, a traditional food produced in the Toyama prefecture of Japan consisting essentially of sliced turnips and salted yellowtail sandwiched together and pickled in malted rice and salt. Commercially available samples of Kaburazushi, obtained from 10 major producers, were subjected to physicochemical analyses, including those for microbial number, components of taste, and physical properties, in addition to sensory evaluation. How these factors relate to one another was examined by means of a multivariate analysis. The extent of fermentation, organic acid composition, and carbohydrate composition, estimated from the microbial numbers, were found to be significantly different among samples obtained from the various producers. A principal component analysis showed two axes ; one showing the degree of lactic fermentation at the opposite pole to the addition of acidulants and sweeteners, and the other showing the degree of the saccharification of rice starch. The product samples were divided into three types : those produced by means of traditional procedures ; a type somewhat inadequately fermented ; and a type whose taste had been modified to some degree. The physicochemical and sensory properties were combined to perform a principal component analysis. The results suggested the existence of two prominent paradigms of value held by consumers when rating the samples : one which related to the taste acquired through the addition of sweeteners ; and the other which saw them scoring highly the seasoned taste resulting from production involving traditional procedures.

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Within the standard method for determination of nitrite in processed foods, sample solutions containing nitrite extracted from the foods are treated with sodium hydroxide and zinc acetate, as deproteinizing agents, before colorimetry is conducted by diazotization-coupling. However, in the case of pollack roe, analysis is very difficult or often impossible to carry out due to the turbidity, decrease in filtration rate, and foaming of the sample solution. It is suspected that these conditions are caused by the high concentration of soluble proteins originating from pollack roe. With this in mind, improvement of the procedure for preparing sample solution from pollack roe and its products was investigated. Results showed that decreases in filtration rate were resolved by the use of half the volume of deproteinizing agents in addition to twice the concentration as that of the standard method. The addition of silicone-type antifoaming agent SI suppressed the sample solution foaming and increased the filtration rate. Adding sodium chloride was not effective in avoiding turbidity or decreasing filtration rate and foaming. Using our modified method for preparing sample solutions, concentration of nitrite in pollack roe was determined to be 0.08±0.02 ppm and the recovery ratio of 5 ppm of nitrite added to pollack roe was 89.8±2.5%, respectively.

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An extract of Hatakeshimeji (Lyophyllum decastes Sing.) was orally administrated once to male and female mice and to male mice for 20 weeks. We macroscopically observed general symptoms, the presence or absence of death during a dose period, and the presence or absence of abnormality upon completion. Results suggest that the general observation of symptoms and increase of weight were unchanged and no death or abnormal findings were present at autopsy.
In addition, the extract of Hatakeshimeji (2.88g) was administrated orally to 11 adults for two weeks during which we assessed its safety by conducting blood tests, urine tests, and blood pressure and body measurement checks. Consequently, there were no clinical problems observed with regard to blood test results, hepatic and renal functions, glucose and lipid metabolisms, and blood pressure. Likewise, analysis of agaritine from hot-water extracts of Hatakeshimeji showed no such problems. These results suggest that the extract of Hatakeshimeji is a safe food and may perform some health functions.

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Heat-induced gels were prepared from two different types of frozen fish-meat (Surimi) to which rice starches had been added. All the stress-strain characteristics except yield strain of gel, prepared from second-grade Surimi, were enhanced to coincide with increases of the amount of starches added. At 20% addition, the breaking stress and strain reached the same levels as those of gel obtained from SA-grade Surimi. The addition of pregelatinized starches to SA-grade Surimi enhanced stiffness of the gel, but decreased yield and breaking characteristics. Some characteristic values of gel added with 3% pre-gelatinized starches were proximal to those of gel added with 10% Chinese yam.

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[in Japanese]

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