Akihiro Ibe

Degradation of Aflatoxins by Food Additives

Degradation of four aflatoxins (AFB1, AFB2, AFG1 and AFG2) by food additives was investigated. Pure aflatoxins were degraded by treatment with solutions of acidic food additives (hydrochloric acid:HCl and sulfuric acid:H2SO4), alkaline food additives (sodium bicarbonate:NaHCO3, sodium carbonate:Na2CO3, sodium hydroxide:NaOH, sodium sulfite:Na2SO3, and sodium hypochlorite:NaOCl) and neutral food additives (potassium metabisulfite:K2S2O5, sodium bisulfite:NaHSO3, sodium hydrosulfite:Na2S2O4, hydrogen peroxide:H2O2, sodium chlorite:NaClO2, and ammonium peroxodisulfate:(ÑH4)2S2O8). The aflatoxins were treated with these neutral food additives under several conditions, and the effects of treatment temperature, time, and concentration of food additives on aflatoxin degradation were studied. Potassium bromate (KBrO3), potassium nitrate (KNO3), and sodium nitrite (NaNO2) had no effect on aflatoxins. Of the aflatoxin added to corn, 20% AFB, remained after treatment with the solution of NaHSO3 (0.5%, 48 h), but all of the AFB1 was completely degraded by NaClO2 (0.25%, pH 4, 48 h) and (NH4)2S2O8 (0.25%, 48 h) at 60°C. Of the aflatoxins added to butter beans, less than 20 and 5% of AFB1 remained after boiling treatment with a 2 and 0.5% solution of Na2S2O4, respectively. These findings suggested that aflatoxins can be degraded or removed by treatment with food additives during food processing.

Comparative evaluation of three different extraction methods for rice (Oryza sativa L.) genomic DNA.

Recently, more immediate and precise cultivar-identifying methods targeting the specific and/or introduced gene(s) have been put into practical use for various rice cultivars. However trustworthy and innovative the biotechnological analyses may be, DNA purity and quality do have unpredictable influences upon the identification. Extraction methods of rice DNA have hardly ever been compared in a comprehensive manner. In this study, we investigated extraction characteristics of three methods by using 10 rice cultivars and then examined template availability of rice DNAs thereby extracted. An UV spectrophotometric study with a view toward methods revealed three different facts: The Isoplant II kit method with inhibitor absorption yielded the most DNAs, the Takara kit method with magnetic trapping produced the best DNAs free from contaminative proteins, and the enzymatic digestion method exclusively with enzymatic digestions prepared the best DNAs free from contaminative polysaccharides. Moreover, with a view toward cultivars, an insignificant difference in yield was not entirely bore out, and some difference in cultivar might cause significant difference in yield; however, no significant difference in purity was found among the cultivars used. On the other hand, electrophoretic images of the DNAs from the same cultivars showed considerable differences in quality among the methods. Furthermore, the DNA extracts from certain brands of rice proved really available for cultivar identification by using polymerase chain reaction (PCR) related to sequence-tagged sites. Therefore, this study suggested that these extraction methods may be used as the situation demands and that the DNAs thereby extracted might work successfully even in cultivar-identifying PCRs.

微生物学的スクリーニング，HPLCおよびLC/MS/MSによる食肉中の残留テトラサイクリン系抗生物質4薬剤の迅速分析

A rapid and precise determination residues of 4 tetracyclines (TCs) (oxytetracycline (OTC), tetracycline (TC), chlortetracycline (CTC) and doxycycline (DOXY)) in meat was developed by employing three analyses; a microbiological screening, HPLC and LC/MS/MS. TCs were extracted with pH 4.0 McIlvaine buffer containing 0.01 mol/L EDTA from a meat sample, and then purified using a mixed mode, reversed-phase and cation-exchange cartridge. The mean recoveries (n=5) of 0.2 microg/g OTC, TC and CTC, 0.05 microg/g DOXY spiked in meat samples were 76.6-99.0% (C.V. 1.6-5.4%). In 13 meat samples in which the microbiological screening indicated the presence of TCs, CTC (9 samples) and DOXY (4 samples) were identified with HPLC and LC/MS/MS.

米中の農薬残留実態(1995年4月∼2005年3月)

Pesictide residues in 343 samples of domestic rice and 32 samples of imported rice purchased on the Tokyo market from April 1995 to March 2005 were investigated. Residues of eleven kinds of pesticides (including organophosphorus, organochlorine, carbamate, pyrethroid and organonitrogen pesticides and bromide) were detected at levels between trace and 1 ppm in 47 domestic rice samples. DDVP and bromide residues were detected at levels between 0.01 ppm and 5 ppm in 18 imported rice samples. For rice samples that were found to containing pesticides, the amounts of pesticide intake were calculated according to the daily intake of rice, and they were compared with the ADI values. Since residual pesticide levels were 17/10,000-2/5 of ADI, all the rice samples were considered to be safe for human consumption.

Content and Origin of Nonvolatile Amines in Various Commercial Pickles

The content of nonvolatile amines (putrescine, cadaverine, histamine, tyramine, and spermidine) in commercial pickles and their raw materials was determined in order to investigate the origin of these amines and to evaluate possible health risks. The nonvolatile amine content varied depending on the type of pickle; histamine and tyramine contents were relatively high, namely, 6.0-264 and 2.0-369 μg/g, respectively, especially in soybean paste pickles and moromi pickles. Amines derived from raw materials were detected in soy sauce pickles, soybean paste pickles, and moromi pickles. However, the raw materials/vegetables of rice bran pickles, sake lees pickles, and malt pickles did not contain these amines, and so the amines in these pickles might have been produced by microorganisms during the fermentation process. Judging from the measured amine content of pickles, the potential health risk is estimated to be low.

Determination of Nonvolatile Amines in Foods by Improved Dansyl Derivatization Reaction

An analytical method for the determination of nonvolatile amines (putrescine, cadaverine, histamine, tyramine, and spermidine) in foods was developed, using an improved dansyl derivatization technique. The five amines were extracted from food with 1% trichloroacetic acid. Three milliliter of extract was applied to a polymer-based strong cation exchange resin mini-column, which was washed with 5 mL of water, and eluted with 5 mL of 1 mol/L potassium carbonate solution. The eluate was dansylated, then 5 mL of toluene was added with shaking. The toluene layer was evaporated. The residue was taken up in 1 mL of acetonitrile and shaken with 1 mL of 5% proline in 1 mol/L potassium carbonate solution. The upper acetonitrile layer was collected, filtered, and subjected to HPLC. The limits of quantitation for putrescine and cadaverine in the samples were both 0.2 μg/g; those of spermidine, tyramine, and histamine were 0.8, 2.0, and 5.0 μg/g, respectively. The average recoveries of the five amines from nine foods exceeded 80%.