Hisaya Terada

Studies on the analysis of food additives by high-performance liquid chromatography. V. Simultaneous determination of preservatives and saccharin in foods by ion-pair chromatography.

A high-performance liquid chromatographic method for the simultaneous determination of sorbic acid, benzoic acid, p-hydroxybenzoic acid and its methyl, ethyl, isopropyl, n-propyl, isobutyl, n-butyl esters and saccharin in foodstuffs is described. For good separations of these compounds, acetonitrile-water-0.2 M phosphate buffer pH 3.6 (7:12:1) containing 2 mM cetyltrimethylammonium bromide as an ion-pair reagent and a Nucleosil 5C18 column are required. A steam distillation method and a Sep-Pak C18 cartridge method for the sample preparation are compared. The recoveries from a coffee drink were generally better than 93.8% and the relative standard deviations were 0.85-2.15% for the Sep-Pak C18 cartridge method.

Determination of Ochratoxin a in coffee beans and coffee products by monoclonal antibody affinity chromatography

A clean‐up method using a monoclonal antibody affinity column was developed for the analysis of ochratoxin A (OTA) in coffee products. Monoclonal antibody specific for OTA was covalently bound to Sepharose‐4B and the resultant affinity column was used for the clean‐up of sample extracts. OTA was quantitatively recovered from the affinity column. The subsequent high performance liquid chromatography (HPLC) of the eluted sample revealed no marked interference peaks when compared with those extracts obtained by conventional approaches. The HPLC peak coinciding with OTA was confirmed by derivatization into ethyl and n‐propyl esters. Furthermore, the present affinity column could be regenerated at least 30 times without significant loss of the binding activity. The detection limit of OTA in the present affinity column‐HPLC procedure was 0.5 μg/kg for coffee beans and instant coffee powder, and 0.025 μg/kg for a canned coffee drink. The recoveries of OTA from coffee products were more than 98%, with coefficient...

Caffeine degradation and increased ochratoxin A production by toxigenic strains of Aspergillus ochraceus isolated from green coffee beans.

The growth and ochratoxin A production of Aspergillus ochraceus strains S-235-100 and IFM 0458, which were isolated from green coffee beans and glutinous rice, respectively, were examined in yeast extract-sucrose (YES) medium containing 0.1 to 1.0% caffeine. The mycelial growth and ochratoxin A formation of strain IFM 0458 was inhibited by caffeine at concentrations over 0.1%, and ochratoxin A was not produced at caffeine levels of 0.5% and 1.0%. Contrary to this, A. ochraceus strain S-235-100 produced a larger amount of ochratoxin A in the presence of 0.5% and 1.0% caffeine when grown on YES medium, reaching a maximum after 15 to 20 days of incubation.The formation of ochratoxin A by nine additional strains of A. ochraceus, three strains of A. elegans and one strain of A. sclerotiorum isolated from green coffee beans was determined on rice and ground green coffee media. A significant degree of degradation of caffeine in the green coffee medium was demonstrated with cultures of nine A. ochraceus isolates from green coffee beans. Most of these isolates showed the potential to grow on moist green coffee beans and to produce a significant amount of ochratoxins.

光化学反応を利用したHPLCによる食品中の酢酸dl-α-トコフェロールおよびdl-α-トコフェロールの定量

A reliable analytical method for the simultaneous determination of dl-alpha-tocopherol acetate and dl-alpha-tocopherol in foods was established by HPLC using post-column photochemical reaction with UV and fluorescence detection. For low-fat food such as fruit juice and vegetable sauce, the tocopherols were extracted with methanol containing 0.1% ascorbic acid and the extract solution was injected into the HPLC. For fatty foods such as butter and margarine, the tocopherols were extracted with a mixed solvent of acetonitrile-2-propanol (9:1) containing ascorbic acid. The extract was cleaned up using a Sep Pak plus C18 cartridge and the eluent from the cartridge was injected into the HPLC. The peaks corresponding to tocopherols on the chromatogram were confirmed by comparing their UV spectra with those of the standard mixture at lamp-on and lamp-off of the photochemical reactor. The recoveries of tocopherols from low-fat foods (orange juice and barbecue sauce) fortified at levels of 10 and 100 microg/kg each were 88.3 to 105.8% (RSD 0.5 to 6.0%) and those from the fatty foods (peanut butter and margarine) fortified at 100 microg/kg each were 57.1 to 88.3% (RSD 3.0 to 6.4%). The determination limits corresponded to 10 microg/kg of the tocopherols in the low-fat foods and 20 microg/kg in the fatty foods.

HPLCおよびLC-MS/MSによる加工食品中の超高甘味度甘味料アドバンテーム定量法

A simple method using HPLC and LC-MS/MS was developed for the determination of ultra-high-intensity sweetener, advantame, in processed foods. Advantame was extracted by dialysis, and cleaned up on a Sep-Pak Plus C18 cartridge, then determined by HPLC and LC-MS/MS. The recoveries from 5 kinds of processed foods fortified at the levels of 0.001 g/kg and 0.01 g/kg were 64.1-89.9% (RSD 0.9-6.9%) by HPLC and 68.8-99.9% (RSD 0.8-4.9%) by LC-MS/MS. The quantitation limit was 0.0004 g/kg by HPLC and 0.00004 g/kg by LC-MS/MS.

Species Identification of Pufferfish Products Using RAPD Analysis

A simple and rapid method was developed to identify the source species of pufferfish products. Randomly amplified polymorphic DNA (RAPD) analysis was applied to identify 8 species of pufferfish. Commercial kits were used for DNA extraction and amplification. Simultaneous identification was possible by polyacrylamide gel electrophoresis of PCR products. Two primers were chosen based on the result of pre-examination with 40 primers, and the PCR conditions were optimized. Characteristic RAPD patterns were obtained for each pufferfish species. The developed method was applied to identify the source species of 26 pufferfish products. The results suggest that the developed method would be useful for verification of the labeled species of pufferfish products.

Observed distribution of radiocaesium contamination in shiitake lots and variability of test results

Shiitake mushrooms (Lentinula edodes) cultivated on bed-log are known to accumulate radiocaesium. Since the Fukushima–Diichi nuclear power plant accident (2011), the violation rate has been higher for log-cultivated shiitake than that for agricultural products or other foodstuffs. When testing shiitake mushrooms for radionuclide contamination, the validation of the sampling plan can be severely compromised by the heterogeneous contamination within shiitake lots. Currently, few data are available on the statistical properties of the radiocaesium contamination of log-cultivated shiitake. In this paper, shiitake lots contaminated by radiocaesium were identified and the distribution of the radiocaesium concentration within the lots investigated. The risk of misclassifying shiitake lots was predicted from the operating characteristic curve generated from Monte Carlo simulations and the performance of various sampling plans was evaluated. This study provides useful information for deciding on an acceptable level of misclassification risk.