The detection sensitivity of the protein wiping method based on BCA assay was evaluated for specified allergenic food ingredients. The detection sensitivity was measured when BSA samples and eight specified allergenic food ingredients (shrimp powder, crab powder, walnut paste, wheat flour, buckwheat flour, liquid egg, milk, and peanut powder) were applied to 25 cm² stainless steel surfaces, dried, and subsequently wiped off with a swab. The visually detectable limit was determined to be 2–2.25 μg using a BSA solution as the standard, with an absorbance of approximately 0.3 at 562 nm. Test areas with low (2.5 μg/25 cm²), medium (5.0 μg/25 cm²), and high (7.5 μg/25 cm²) contamination levels were prepared, and recovery tests were performed using the protein wiping method. The measurement error was within ±0.03. Moreover, the recovery rate from swabs was observed as 78.2–94.4%. Recovery tests for eight specified allergenic food ingredients showed the ability to detect the ingredients when >10 μg of material was applied to the test surface. This study suggested that the protein wiping method is useful for cleanliness control to prevent cross-contact of allergens in the food manufacturing environment.

We isolated Phytolaccasaponins B, E and G, which are toxic components of Phytolacca americana. Highly purified products were extracted from Phytolacca americana root extract using silica gel, ODS, diol column chromatography. Using these components as analytical standards, we optimized the LC-MS/MS conditions and established 3 components simultaneous analysis method. In recovery tests, the average recovery ranged from 74 to 119%, with a repeatability of 1.0 to 7.1% RSD. Analyses of a 2018 food poisoning specimen indicated 3 toxic components in the leaves and 2 toxic components in the roots. Those findings suggest that the simultaneous analysis method was useful for a food poisoning specimen. These results show that this method is required for identifying food poisoning caused by Phytolacca americana, even when leftovers are unrecognizable or when the poisoning is caused by plant parts other than the roots.

This study investigated the effective detection methods and contamination status of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on the surface of commercially available vegetables and fruits. SARS-CoV-2 RNA was detected by quantitative real-time RT-PCR. A comparison of swabbing methods using three types of materials and five wiping techniques revealed the highest recovery rate when using a polyester swab, wiping in four directions and suspending the swab in PBS after each swabbing direction. The recovery rate of the method was 8–26% on the surfaces of five different types of commercially available vegetables and fruits. Examination of effective washing for removing SARS-CoV-2 from the surface of eggplants showed that >90% of the virus could be removed by water wiping or scrubbing. A total of 90 commercially available vegetables (45 cucumbers and 45 tomatoes) purchased between June and October 2023 were tested to determine the status of SARS-CoV-2 contamination. Although the virus RNA was detected from only one cucumber purchased in August, the number of infectious viruses could not be determined. Results demonstrated that commercially available vegetables have low risks as a source of COVID-19 infection. Preventive measures such as practicing appropriate respiratory etiquette may contribute to the prevention of SARS-CoV-2 contamination in food products. Furthermore, washing the produce with water and basic infection control measures, including hand hygiene and mask wearing, are essential to reduce the risk of infection through food.

Standard curves are used to estimate the concentration of a target substance in food samples and the curves are generally made with the least square method. The least square method is allowed to apply only under the condition that the measurements follow the normal distribution with a constant variance. Actually, however, it is thought that as the measurements of samples are higher, the scattering of the measurements would be also larger. In this study, thus, the effect of the scattering of measured values of samples on the concentration estimation was studied with two normal distribution models with a constant variance and a variance changing to measured values. Measurement data analyzed here were random samples from the normal distributions with various variance. As a result, in the case that the concentrations of the target substance and the measurements were linear, the latter model with the changing variance was statistically more appropriate for the data whose scattering increased with it. However, no remarkable differences were observed between the two models in the standard curves and the estimates from those curves for the measurement sets studied. In the case that the concentrations and the measurements were nonlinear being concave downward and upward, the same results were also observed. These results showed that the model with the changing variance would be more appropriate than the one with the constant variance for various measurement data, while both models could also successfully estimate the concentration of unknown samples.

The Codex Standard for Honey adopts diastase activity as an indicator of honey freshness and as a measure to detect overheating during the manufacturing process. However, in some cases a foreign amylase is added to honey to increase its diastase activity. In our previous study, we developed a simple and sensitive method for screening foreign amylases using native polyacrylamide gel electrophoresis followed by activity staining. In this study, to confirm the effectiveness of this method, a collaborative study involving 12 laboratories was conducted in accordance with the AOAC guidelines for qualitative analysis, targeting amylases derived from the Aspergillus and Geobacillus, which were frequently detected in Japan. From the probability of detection (POD) curve confirmed in the preliminary test, three concentrations (low, medium, and high) calculated as diastase numbers were set, and eight samples of each concentration (total of 24 samples) were distributed in a blind manner and evaluated. The results showed that while the POD at the middle level was higher than expected, the method demonstrated sufficient performance to determine the presence or absence of foreign amylase.