Determination of the soybean allergen Gly m 6 and its stability in food processing using liquid chromatography-tandem mass spectrometry coupled with stable-isotope dimethyl labelling.

A cost-effective method using liquid chromatography-tandem mass spectrometry (LC-MS/MS) coupled with stable-isotope dimethyl labelling was used for the determination of Gly m 6. The validation results revealed that the recoveries and precisions obtained from five spiked levels were in the ranges of 88.8-113.0% and 8.3-22.0%, respectively. The content and stability of the major soybean allergen Gly m 6 in various food processing procedures were evaluated by the quantification results of its surrogate signature peptide. The Gly m 6 content in soybean decreased by 42% after natto fermentation, and by 31% and 35% in pasteurised soymilk and sterilised soymilk, respectively, relative to the raw soymilk. Only 19% of Gly m 6 in raw soymilk was retained in the soymilk film. This study extended the feasibility of dimethyl labelling to soy-based food samples and examined the proteolysis of Gly m 6 in natto fermentation and its thermal instability.

Rapid screening and determination of pesticides on lemon surfaces using the paper-spray mass spectrometry integrated via thermal desorption probe.

This paper presents a novel thermal desorption probe integrated with the corona-discharged assisted paper-spray mass spectrometry (PS-MS) for rapid detecting the residual pesticides on fruit surfaces. Pesticide detection can be simply achieved by scratching the fruit surface and then placed in front of the inlet of the MS for target pesticides screening. A novel ionization method comprising the electrospray ionization and the corona discharged is generated on the paper tip to simultaneously ionize the pesticide of high and low polarities for MS detection. Six pesticides composed of polar acetamiprid, azoxystobin, pyridaben and low polar chlorfenapyr, pyriproxyden, λ-cyhalothrin are successfully detected in seconds. The results are also validated with the LC-MS/MS and GC-MS/MS spectra performed via the standard protocols by a certificated laboratory of Eurofins Taiwan. The developed method provides a rapid, simple yet efficient way for screening residual pesticides on fruits.

Microfluidic colorimetric analysis system for sodium benzoate detection in foods.

Sodium benzoate (SBA) is a widely-used additive for preventing food spoilage and deterioration and extending the shelf life. However, the concentration of SBA must be controlled under safe regulations to avoid damaging human health. Accordingly, this study proposes a microfluidic colorimetric analysis (MCA) system composing of a wax-printed paper-microchip and a self-made smart analysis equipment for the concentration detection of SBA in common foods and beverages. In the presented method, the distilled SBA sample is mixed with NaOH to obtain a nitro compound and the compound is then dripped onto the reaction area of the paper-microchip, which is embedded with two layers of reagents (namely acetophenone and acetone). The paper-microchip is heated at 120 °C for 20 min to cause a colorimetric reaction and the reaction image is then obtained through a CMOS (complementary metal oxide semiconductor) device and transmitted to a cell-phone over a WiFi connection. Finally, use the self-developed RGB analysis software installed on the cell-phone to obtain the SBA concentration. A calibration curve is constructed using SBA samples with known concentrations ranging from 50 ppm (0.35 mM) to 5000 ppm (35 mM). It is shown that the R + G + B value (Y) of the reaction image and SBA concentration (X) are related via Y = -0.034 X +737.40, with a determination coefficient of R2 = 0.9970. By measuring the SBA concentration of 15 commercially available food and beverage products, the actual feasibility of the current MCA system can be demonstrated. The results show that the difference from the measurement results obtained using the macroscale HPLC method does not exceed 6.0%. Overall, the current system provides a reliable and low-cost technique for quantifying the SBA concentration in food and drink products.