We designed an off-line combination of HPLC/photodiode array detector (PDA) and 1H-quantitative NMR (1H-qNMR) to estimate the relative molar sensitivity (RMS) of an analyte to a reference standard. The RMS is calculated as follows: a mixture of the analyte and the reference is analyzed using 1H-qNMR and HPLC/PDA. The response ratio of the analyte and the reference obtained by HPLC/PDA is then corrected using the molar ratio obtained by 1H-qNMR. We selected methylparaben (MPB), which is a certified reference material, as the reference standard and hesperidin (Hes) and monoglucosylhesperidin (MGHes) as analytes, and the RMSs of Hes283 nm/MPB255 nm and MGHes283 nm/MPB255 nm were determined as 1.25 and 1.32, respectively. We determined the contents of Hes and MGHes in processed foods by the conventional absolute calibration method and by the internal standard method employing the RMS values with respect to MPB. The differences between the values obtained with the two methods were less than 2.0% for Hes and 3.5% for MGHes.
Analysis of L-ascorbic acid (AsA) and erythorbic acid (ErA) in foods is generally performed by HPLC measurement after extraction with metaphosphoric acid solution. But this method can not always measure the concentrations of AsA and ErA precisely due to the presence of interfering compounds, and the reproducibility of retention time is poor. We considered that quantitative analysis by HPLC and confirmation by LC-MS/MS using an identical extraction solvent might be an effective approach for AsA and ErA analysis. Chelate fiber was added to the sample, followed by extraction with acetic acid solution containing ethylenediaminetetraacetic acid disodium salt, purification with Oasis MCX, and 2-fold dilution with methanol. The resulting solution was used for quantification by HPLC using a ZIC-HILIC column and identification by LC-MS/MS. In recovery tests with 8 kinds of foods, the recovery of AsA was over 91%, and that of ErA was over 88%. The RSD was 5.1% or less for both analytes. Analysis of 8 kinds of foods by both methods showed that this method gave better RSD values than the conventional method. AsA and ErA in all samples were confirmed by product ion scanning and selected reaction monitoring of LC-MS/MS.
A simple and useful method for the determination of nitrite in meat and fish products was developed. The sample (2.5 g) was extracted and cleaned up by dialysis in tris hydroxymethyl aminomethane solution with shaking at 80℃ for 2.5 hr. Nitrite in the dialysate was quantified by colorimetric analysis. Furthermore, the dialysate was cleaned up with SPE under cooling, and nitrite in the resulting solution was determined using LC-UV with an anion exchange column for confirmation. The recoveries of nitrite from frankfurter and fish sausage, fortified at the levels of 0.002 g/kg and the maximum usage dose (0.070 g/kg for meat products, 0.050 g/kg for fish sausage) ranged from 82.6 to 104.8% in colorimetric analysis and from 88.3 to 97.6% in LC-UV confirmation analysis. The values determined in various meat and fish products by the developed method and by the Japanese official method were approximately equivalent.
It has been suggested that a myxosporean parasite, Unicapsula seriolae, is responsible for food-borne disease associated with the ingestion of raw greater amberjack. In this study, we quantified U. seriolae in greater amberjack meats involved in food-poisoning episodes. U. seriolae DNA was detected in 26 samples out of 29 samples by means of quantitative real-time PCR(qRT-PCR). The major symptoms were diarrhea and vomiting within 12 hours after consumption. No seasonal trend in the outbreaks was apparent. The number of spores in samples with qRT-PCR-detected U. seriolae DNA ranged from 1.9×105 to 1.7×107 spores/g. However, no spores were detected in greater amberjack purchased from markets. These results indicate that U. seriolae was responsible for the outbreaks. The copy number of DNA in the positive samples was more than 107 copies/g. The ingestion amount was known in 11 of the incidents, and the minimum quantity of spores that caused symptoms was estimated to be 3.8×106 spores/g.
A quantitative analysis by HPLC of α-glucosyltransferase-treated stevia in foods was considered. This analysis is the way which hydrolyzed α-glucosyltransferase-treated stevia in the stevioside (SS) and the rebaudioside A (RS) using a glucoamylase. Recovery (%) of α-glucosyltransferase-treated stevia, spiked at 200 mg/kg in various foods, were more than 80% and the relative standard deviations were less than 5.0% as SS and RS for the rate of collection. A qualitative analysis by LC-MS/MS was performed 36 products of commercial foods containing stevia. We quantified of 11 products in which α-glucosyltransferase-treated stevia was detected. Quantitative value was at most 180 mg/kg as SS, at most 70 mg/kg as RS.
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.
Aspergillus parasiticus contamination of peanuts results in the production of highly toxic metabolites, such as aflatoxin B1, B2, G1 and G2, and its incidence in imported peanuts is reported to be increasing. Here, we examined whether the antifungal compound allyl isothiocyanate (AIT), which is present in mustard seed, could inhibit the growth of seed-borne fungi and aflatoxin-producing fungi. Peanuts produced in China and Japan were inoculated with A. parasiticus and exposed to AIT vapor released by a commercial mustard seed extract in closed containers under controlled conditions of temperature and humidity. AIT in the inoculated peanut samples reached its highest concentration of 44.8 ng/mL at 3 hr and decreased to 5.6 ng/mL after 9 weeks. Although AIT decreased the growth of the seed-borne fungi during the test period, the inoculated fungi survived. All tested peanuts samples were analyzed for aflatoxin using the HPLC method. There was a correlation between the number of aflatoxin-producing fungi and the total amount of aflatoxin production in the inoculated peanut samples. Our results indicate that AIT was effective in inhibiting the growth of seed-borne fungi and aflatoxin-producing fungi.
S-421 is a synergist of pyrethroid and organophosphorus pesticides, which are used as termiticides or household insecticides. S-421 is stable and ubiquitous in the environment. Here we describe the concentrations of S-421 in domestic and imported commercial fish collected from 2009 to 2016. Samples were extracted with acetone/hexane and S-421 was purified on a silica gel column. Quantitative analysis was performed by GC-ECD. S-421 was detected in 78 of 116 samples of domestic fish and shellfish at levels of <0.2 to 2.6 ng/g (mean: 0.4 ng/g), and in 69 of 102 imported samples at a level of <0.2 to 1.5 ng/g (mean: 0.4 ng/g). The concentrations of S-421 in fish were lower than those of p,p′-DDE and similar to those of β-HCH.
An interlaboratory study was performed to evaluate the equivalence between an official method and a modified method of evaporation residue test using three food-simulating solvents (water, 4% acetic acid and 20% ethanol), based on the Japanese Food Sanitation Law for food contact products. Twenty-three laboratories participated, and tested the evaporation residues of nine test solutions as blind duplicates. For evaporation, a water bath was used in the official method, and a hot plate in the modified method. In most laboratories, the test solutions were heated until just prior to evaporation to dryness, and then allowed to dry under residual heat. Statistical analysis revealed that there was no significant difference between the two methods, regardless of the heating equipment used. Accordingly, the modified method provides performance equal to the official method, and is available as an alternative method.
An interlaboratory study was performed to evaluate the equivalence between an official method and a modified method of evaporation residue test using heptane as a food-simulating solvent for oily or fatty foods, based on the Japanese Food Sanitation Law for food contact products. Twenty-three laboratories participated, and tested the evaporation residues of nine test solutions as blind duplicates. In the official method, heating for evaporation was done with a water bath. In the modified method, a hot plate was used for evaporation, and/or a vacuum concentration procedure was skipped. In most laboratories, the test solutions were heated until just prior to dryness, and then allowed to dry under residual heat. Statistical analysis revealed that there was no significant difference between the two methods. Accordingly, the modified method provides performance equal to the official method, and is available as an alternative method. Furthermore, an interlaboratory study was performed to evaluate and compare two leaching solutions (95% ethanol and isooctane) used as food-simulating solvents for oily or fatty foods in the EU. The results demonstrated that there was no significant difference between heptane and these two leaching solutions.