Azodicarbonamide (ADA) is used in some countries as a flour bleaching agent and a dough conditioner. However, ADA is prohibited for use as a food additive in Japan. Therefore, it is necessary to establish an efficient and sensitive method to determine ADA in wheat flour. A simple and practical procedure to analyze ADA in wheat flour and prepared flour mixes was developed. ADA was extracted from samples by ultrasonication with acetone. ADA in the solution was derivatized with triphenylphosphine (TPP). The ADA-TPP derivative was concentrated and cleaned up using a reversed-phase solid-phase extraction cartridge, and the ADA-TPP derivative was analyzed using HPLC for determination and LC-MS/MS for identification. Good linearity was achieved over the concentration range of 0.25–100 ppm ADA in wheat flour and prepared flour mixes. The mean recoveries from wheat flour and prepared flour mixes fortified at the levels of 1 and 10 ppm ranged from 86.9 to 101.0%, and the coefficients of variation ranged from 1.9 to 3.4%.
A method using high-performance liquid chromatograph (HPLC) was developed for the identification of colorants migrated from colored modeling clays, which are popular toys for children. Twelve permitted dyes and 25 non-permitted dyes were analyzed in 20 clays (10 wheat clays, 2 rice clays, 2 corn clays, 3 paper clays and 3 resin clays). As a result, 13 products which were labeled for children's use (under 6 years old) met the specifications of the Japanese Food Sanitation Law, while non-permitted colorants were eluted from 2 products. In additon, unknown colorants were eluted from 3 products for people over 6 years old, although these are not covered by the Japanese regulation. It was suggested that some type of clays contained pigments, which are generally used in printing ink and plastics.
Rapid multi-residue analysis of pesticides in pulses was developed using LC-MS/MS. Pesticide residues in 5 g of homogenized pulses were extracted with 30 mL of acetonitrile and salted out with 4 g of anhydrous magnesium sulfate and 2 g of sodium chloride in the presence of citrate buffer in a disposable tube. The resulting residues were extracted with 30 mL of acetonitrile, and co-extractives were removed on a handmade four-layer column, consisting of a layer of Z-Sep/C18 (20 mg/50 mg) dry particles on top of a three-layer, custom-made (pre-packed) column (lower bed: 60 mg of PSA, middle bed: 30 mg of GC, and top bed: 60 mg of C18) packed in a 10 mm internal diameter polypropylene column (3 mL). The developed method showed good recoveries of pesticides in soybean, lentil, white kidney bean and garbanzo. According to the method validation guideline of the Ministry of Health, Labour and Welfare of Japan, recovery tests were conducted in soybeans fortified with 107 kinds of pesticides at the levels of 0.01 and 0.1 μg/g, respectively. At each concentration 2 samples were extracted on 5 separate days. Pesticides in the test solution were determined by LC-MS/MS using scheduled MRM. As regards the trueness of this method for 107 pesticides in soybeans, 97 pesticides were in the range of 70–120% with satisfactory repeatability and within-run reproducibility. This new method is expected to be applicable for routine examination of pesticide residues in soybeans.
A rapid dialysis method for the analysis of stevioside (SS) and rebaudioside A (RS) in foods was developed. Minced samples (10 g) were packed into 30 cm net length dialysis tubing with 30% methanol to increase the dialysis efficiency. The dialysis tubing was put in a 100 mL centrifuge tube, and the total fluid volume was made up to 100 mL with 30% methanol. Dialysis was done with shaking while heating at 50℃. The dialysis times were reduced from 48–72 hr in the conventional method to 2 hr under these conditions. The dialysate was loaded on a C18 solid- phase extraction cartridge, and the cartridge was washed with 40% methanol. SS and RS were eluted from the cartridge with 80% methanol, and separated by reversed-phase HPLC. Recovery yields (%)of SS and RS, spiked at 0.02 g/kg in various foods, were 83.0–105.1% and the relative standard deviations were mostly less than 5%.
Discriminating vegetable oils and animal and milk fats by infrared absorption spectroscopy is difficult due to similarities in their spectral patterns. Therefore, a rapid and simple method for analyzing vegetable oils, animal fats, and milk fats using TOF/MS with an APCI direct probe ion source was developed. This method enabled discrimination of these oils and fats based on mass spectra and detailed analyses of the ions derived from sterols, even in samples consisting of only a few milligrams. Analyses of the mass spectra of processed foods containing oils and milk fats, such as butter, cheese, and chocolate, enabled confirmation of the raw material origin based on specific ions derived from the oils and fats used to produce the final product.
Cefsulodin–irgasan–novobiocin agar (CIN) has been used as a selective agar to detect Yersinia in food or human patients; however, its components can inhibit the growth of some strains of Yersinia enterocolitica serovar O3 and Y. pseudotuberculosis. Recently, a new Yersinia selective agar, CHROMagar Yersinia enterocolitica (CAYe), was developed and evaluated as a novel selective agar for pathogenic Y. enterocolitica. In this research, a total of 251Yersinia strains (176 pathogenic Y. enterocolitica, 59 Y. pseudotuberculosis, and 16 non-pathogenic Yersinia) were cultured on both CIN and CAYe for comparison. Except for 10 of 104 pathogenic Y. enterocolitica O3 strains and 59 Y. pseudotuberculosis strains, 198 Yersinia isolates grew on both media after 48 hr of incubation at 32℃. Of the 10 pathogenic Y. enterocolitica O3 which could not grow on CIN or CAYe, 9 strains could not grow on CIN with supplements and 1 strain could not grow CAYe with supplements. Of 9 strains which did not grow on CIN with supplements, 3 strains could not grow on CIN without supplements. However, 1 strain which did not grow on CAYe with supplements could grow on CAYe without supplements. All of the Y. pseudotuberculosis strains could grow on CIN with/without supplements and on CAYe without supplements. The results indicate that the inhibition of the growth of Y. enterocolitica O3 on CIN is related to the components of CIN; however, the inhibition on CAYe appears to be related to the supplements in CAYe. Therefore, CAYe may be a more useful selective medium than CIN for pathogenic Y. enterocolitica .
Using polystyrene, acrylonitrile-styrene resin and acrylonitrile–butadiene–styrene resin pellets as samples, an interlaboratory study was performed to evaluate the volatiles test method, based on the specifications described in the Japanese Food Sanitation Law for food-contacting polystyrene products. The study was conducted with the participation of twenty-one laboratories. Each laboratory quantified the contents of styrene, toluene, ethylbenzene, isopropylbenzene and propylbenzene in three test pellets using GC-FID, GC-MS or headspace-GC-FID. Statistical analysis revealed that the repeatability (RSDr) and reproducibility (RSDr) were 1.0–2.6 and 2.5–5.5% for the GC-FID method. The values of the performance parameters fulfilled the requirements (RSDr: 10%, RSDr: 25%), and the performance is sufficient for specifications testing. The RSDr and RSDr of results obtained using the GC-MS and HS-GC methods were 1.4–7.8 and 4.9–13%(GC-MS), and 2.0–2.6 and 3.3–6.9%(HS-GC-FID), respectively. The quantified levels were similar to those obtained with GC-FID. The study suggests that the GC-MS and HS-GC methods can be employed as alternative methods to the GC-FID method.