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Shiitake powder is an important part of international agricultural trade. It is generally in dry powder state due to the requirement of preservation, so economically motivated adulteration in the shoddy way (using stipe instead of pileus) or the counterfeit way (using cheap mushroom) should be concerned, while methods for the authenticity identification of shiitake powder were barely reported. Herein, a fingerprint method was developed for the authenticity identification of shiitake powder through high-performance liquid chromatography (HPLC) coupled with chemometrics. The results showed that shiitake pileus powder and stipe powder can be discriminated using PCA and OPLS-DA. Besides, shiitake pileus powder, Pleurotus eryngii (P. eryngii) powder, shiitake cultivation bag powder and Pleurotus ostreatus (P. ostreatus) powder can be discriminated using OPLS-DA. This work provided usable technical solutions for two ways of economically motivated adulteration in shiitake powder. [ABSTRACT FROM AUTHOR]

Nitrofurans are a group of widely used veterinary antibiotics which have been forbidden in many countries. Surface-enhanced Raman spectroscopy (SERS) coupled with gold nanoparticles was used in this study for the rapid detection and characterization of nitrofuran antibiotics (including furadantin, furaltadone, and their mixture). Density functional theory calculations were conducted with Gaussian 03 at the B3LYP level using the 6-31G(d) basis set to analyze the assignment of vibrations. The SERS measurement of nitrofuran antibiotics has been investigated by active SERS substrate of gold nanoparticles with average size around 50 nm. The SERS qualitative analysis has been studied for furadantin and furaltadone by their characteristic SERS peaks. The peaks at 1,420 and 1,456 cm could be used to discriminate between the two compounds in a mixture. The SERS peaks at 1,008 and 1,162 cm were used as the index of quantitative analysis for furadantin and furaltadone, respectively. Under optimal conditions, the limit of detection could reach the level of 5 ppm. The results showed that the SERS method with gold nanoparticles is capable of identifying and characterizing furaltadone and furadantin, which is valuable to be further applied on the detection of antibiotic residues in food samples. [ABSTRACT FROM AUTHOR]

Methamidophos (MAP) is a highly efficient and broad-spectrum organophosphate pesticide. In this study, a rapid method for detecting MAP in vegetables using surface enhanced Raman scattering (SERS) spectroscopy has been established. Density functional theory calculations were performed with Gaussian 03 at RB3LYP level and with the 6-311G (d) basis set. SERS, normal and theoretical Raman spectroscopy were compared to investigate the mechanism of Raman scattering enhancement. The SERS signal of MAP was improved in alkaline conditions with optimum scattering efficiency at pH of 13.46. Furthermore, MAP detection in vegetables by SERS method had a good linear relationship between 0.01 and 1,000 μg/mL. The concentration of MAP in vegetables was detected and chosen for recovery test with three levels: 4, 8, and 15 μg/mL. The results of three level tests were 86.7-96.6 % and their relative standard deviations were between 1.2 and 2.5 %, which shows the good repeatability of this method. [ABSTRACT FROM AUTHOR]

Butylated hydroxyanisole (BHA) is a common antioxidant used in foods and food packaging materials, and it can migrate into the food during its supply chain. BHA has been shown to be carcinogenic, which has gained substantial attention in recent years. In this study, the feasibility of using surface-enhanced Raman scattering (SERS) coupled with SERS-active gold substrates for rapid detection of trace amounts of BHA was investigated. Raman signals of tested samples were enhanced significantly by SERS. The detection limit of the BHA solution can reach 10 μg/mL by SERS enhanced with 50 nm gold nanoparticles and in a 1.0 pH solution system. The Raman peak at 480 cm was used as the index of quantitative analysis, the line correlation was R = 0.9803. The results showed that the SERS method is useful for sensitive and selective detection of BHA. By comparing the enhanced peak features, the adsorption behavior of BHA on the surface of gold nanoparticles was analyzed in detail and it was determined that the molecule was adsorbed on the gold surface by 'Ph-O(H) (Ph = phenyl)'. The benzene ring vibration increased significantly, inferring that the benzene ring is perpendicular to the surface of the gold nanoparticles. [ABSTRACT FROM AUTHOR]