Simultaneous Determination of TBH<Subscript>2</Subscript>Q and BHA Antioxidants in Food Samples Using Eosin Y Film Modified Electrode

A glassy carbon electrode (GCE) was modified with eosin Y that was electrodeposited on GCE via continuous cycling between ??1.6 and 1.5 V (vs Ag/AgCl). This electrode was characterized by scanning electron microscopy and electrochemical impedance spectra. The resulting electrode exhibited excellent electrocatalytic activity toward the oxidation of butylated hydroxyanisole (BHA) and tert-butyl hydroquinone (TBH₂Q); in addition, the oxidation products of BHA and TBH₂Q were found to be the same, which was studied by CV and in situ FT-IR spectroelectrochemistry. Under the optimized condition, the oxidation peak currents were linear to BHA/TBH₂Q in the range from 0.10 to 7.00 μg mL^?1 with the detection limits of 0.01 μg mL^?1 (S/N?=?3) for BHA and 0.015 μg mL^?1 (S/N?=?3) for TBH₂Q, respectively. Moreover, the reproducibility and repeatability of the electrode were determined. The proposed method was successfully applied in the simultaneous determination of BHA and TBH₂Q in several edible oil samples, and satisfactory results when compared with those obtained using high-performance liquid chromatography.     

Reproducible Molecularly Imprinted QCM Sensor for Accurate,Stable, and Sensitive Detection of Enrofloxacin Residue in Animal-Derived Foods

This study describes the development of a novel reproducible molecularly imprinted quartz crystal microbalance (QCM) sensor for the accurate and sensitive analysis of the residue of enrofloxacin (ENRO) in animal-derived foods. This proposed sensor was easily fabricated by directly immobilizing molecularly imprinted polymer (MIP) of ENRO on the surface of a QCM Au chip, which combined the advantages of selective recognition from the MIP with the high sensitivity and portability of a QCM sensor. The parameters in the fabrication and measurement process were optimized and discussed in detail. It was verified that the MIP-modified QCM Au chip performed favorably for the detection of ENRO residue in common animal-derived food products and demonstrated acceptable accuracy (recovery: pure milk 77.2–84.2%, egg 77.3–85.6%, chicken muscle 73.5–89.1%, pork 74.7–85.8%), precision (relative standard deviation (RSD, n = 3), pure milk 2.9–8.0%, egg 2.9–6.4%, chicken muscle 3.4–6.8%, pork 2.2–4.7%), and sensitivity (limit of detection, pure milk 0.31 μg L^?1, egg 0.44 μg kg^?1, chicken muscle 0.54 μg kg^?1, pork 0.57 μg kg^?1). The MIP-modified QCM Au chip for sensing ENRO was portable, could be stored for an extended period of time, and reused for more than 30 analysis cycles with a response attenuation of 7.8%. These results have demonstrated that the proposed MIP QCM sensor presents an accurate, sensitive, rapid, and low-cost methodology for ENRO residue detection in animal foods. This research is very promising for the development of novel effective devices applied to the detection of various contaminants in the field of food safety.     

Volatile Constituents of Jambolan (<Emphasis Type="Italic">Syzygium cumini</Emphasis> L.) Fruits at Three Maturation Stages and Optimization of HS-SPME GC-MS Method Using a Central Composite Design

The volatile compounds of jambolan (Syzygium cumini L.) fruit were determined at three different maturity stages (unripe, half-ripe, and ripe) by headspace solid-phase microextraction (HS-SPME)–gas chromatography-mass spectrometry (GC-MS) technique using five different fibers (Fused silica PDMS/DVB, DVB/CAR/PDMS, PEG, Stable flex PDMS/DVB, and PDMS). The optimal extraction conditions were evaluated using different variables such as adsorption temperature (minimum 25 °C, maximum 55 °C), salt quantity (minimum 0, maximum 30.0%), and extraction time (min 10, max 30 min). The major classes of compounds identified were ester, terpene, alcohol, aldehyde, and carboxylic acid. Ninety volatile compounds with characteristics aroma attributes were identified, and the primary compounds linked with development of characteristics aroma of ripe jambolan fruit pulp were trans-β-ocimene, β-ocimene, caryophyllene, humulene, D-α-pinene, L-β-pinene, β-pinene, D-limonene, α-terpineol, neo-allo-ocimene, 2-hexenal (E), δ-cadinene, 3-hexen-1-ol, (Z) β-linalool, terpinolene, eremophilene, valencene, 1-hexanol, longipinene, γ-terpinene, γ-muurolene, endo-borneol, o-cymene, nonanal, terpinen-4-ol, β-terpineol, α-muurolene, fenchol, α-fenchene, β-thujene, benzaldehyde, (E)-2-hexenal, β-cadinene, and decanal.     

A Novel Fluorescent Probe for Detecting Hydrogen Sulfide in Wine

Hydrogen sulfide (H₂S) has recently been recognized as the third endogenous gaseous signaling molecule besides NO and CO. At the same time, H₂S is responsible for an important proportion of faulty wines with potentially large economic losses. Thus, the H₂S in wine not only contributes negatively to wine aroma but also faces a problem of food safety. So an efficient and practical sensor to detect H₂S in wine was needed. A new fluorescent probe 4-methyl-2-oxo-2H-chromen-7-yl-thiophene-2-carboxylate (probe 1) was designed and synthesized for detection of H₂S. Addition of H₂S caused the fluorescence intensity of probe 1 increased and fluorescence saturation was reached in 15 min. The fluorescence of probe 1 was found turn-on under UV light at 365 nm. This noticeable change of probe 1 indicates that probe 1 could be employed as a visible detection agent for H₂S. H₂S can be detected quantitatively in the concentration range 0–20 μM, and the detection limit on fluorescence response of the probe was 18 nM. Moreover, probe 1 can be conveniently used as a signal tool to determine the H₂S levels in wine.     

Chemometric Analysis of <Superscript>1</Superscript>H NMR Fingerprints of <Emphasis Type="Italic">Coffea arabica</Emphasis> Green Bean Extracts Cultivated under Different Planting Densities

High planting density has been used to increase coffee production but there are few studies related to the variations it provokes in metabolite compositions. The use of ¹H NMR data associated with chemometric techniques allows the determination of metabolic fingerprints and verification of metabolic changes when coffee is subjected to high planting densities. The aim of this work is to investigate ¹H NMR spectral data of green bean extracts of Coffea arabica cv. IAPAR 59 grown in a square pattern at two planting densities, 6000 and 10,000 plants ha^?1. Thirty extracts were obtained using a simplex centroid design with four solvents (ethanol, acetone, dichloromethane, and hexane). The lyophilized extracts were dissolved in DMSO-d₆ to obtain the ¹H NMR spectra. The spectral data were analyzed with principal component (PCA) and cluster analyses (CA). Significant differences between ethanolic and non-ethanolic extracts were found by PCA. Only the ethanolic mean spectrum showed characteristic chemical shifts of sugars and trigonelline. Acetone extracts were separated by cluster analysis.     

Multivariate Optimization for the Development of a Fast and Simple Ultrasound-Assisted Extraction Procedure for Multielemental Determination in Tea Leaves by Inductively Coupled Plasma Optical Emission Spectrometry (ICP OES)

The current study describes a fast and efficient procedure of ultrasound-assisted extraction for determination of Ca, Mg, K, Na, Cu, Zn, Mn, and Al in tea leaves by inductively coupled plasma optical emission spectrometry (ICP OES). The variables of procedure were optimized using the Box–Behnken design and the conditions selected were nitric acid concentration (1.0 mol L^?1), sonication time (7 min), and sonication temperature (75 °C). The extraction efficiency was calculated using the analyte concentration obtained by a total digestion procedure as reference. Accuracy was confirmed by analysis of certified reference material of apple leaves (NIST 1515) and spinach leaves (NIST 1570a) using the procedure proposed. A statistical evaluation using Student’s t test showed that there is no significant difference between the value obtained with the proposed procedure and the certified value, at 95% confidence level. The proposed procedure was successfully applied and is a good alternative to conventional acid digestion procedure and can be applied to routine analysis for determination of Ca, Mg, K, Na, Zn, Mn, Cu, and Al in tea leaves used for the preparation of infusions.     

Development of Real-time PCR Assays for the Detection of the <Emphasis Type="Italic">pin</Emphasis> II Terminator (t<Emphasis Type="Italic">pin</Emphasis>II) Used in GM Constructs and Its Donor Organism,Potato (<Emphasis Type="Italic">Solanum tuberosum</Emphasis>)

Two singleplex TaqMan methods were developed for the detection of potato targets: one for the detection of the tpinII terminator, which is an emerging terminator used in GM constructs, and one for the detection of the endogenous StLS gene of potato. Performance criteria such as specificity and sensitivity were successfully tested for the two methods, taking into account the recommendations of international guidelines. The presence of the StLS target was checked in 16 potato cultivars. The StLS target is present at low copy number and can be used for quantitation purposes, as demonstrated on transgenic potatoes in this paper. The StLS target is an excellent candidate to replace the presently recommended endogenous target based on the UGP gene, which shows several disadvantages due to its high copy number and lack of specificity. The research also indicates that DNA can easily be extracted from different parts of potato tubers with a classical cetyltrimethylammonium bromide method.     

Simple Solvent Extraction Coupled with Liquid Chromatography-High-Resolution Mass Spectrometry for the Analysis of Pesticide Residues in Rice Bran Protein Powder

A simple analytical method combining solvent extraction and liquid chromatography-high-resolution mass spectrometry (LC-HRMS) was developed for the analysis of pesticide residues in rice bran protein powder. Owning to the high accuracy of HRMS in determination of mass to charge ratio (m/z), a suspect screen of pesticide residues was performed by LC-HRMS prior to quantification analysis. Based on the theoretical m/z, four pesticides including isoprothiolane (IPT), tebuconazole (TBZ), propiconazole (PCZ), and tricyclazole (TCZ) were detected and further verified with their reference standards. The solvent extraction conditions were optimized according to the signal intensity of extracted ion chromatogram (XIC) in LC-HRMS. After optimization, 50% acetonitrile solution was adopted, in which the targeted pesticides could be extracted effectively (recoveries/accuracy of >?85%) with the good reproducibility (relative standard deviation (RSD)?<?10.3%). Two isotope internal standards isoprothiolane-D₄ (IPT-D₄) and propiconazole-D₅ (PCZ-D₅) were applied in quantification, and the quantification results were highly consistent with those from the standard addition method. Limit of detections (LODs) and limit of quantifications (LOQs) of the method were about 0.05–0.2 and 0.2 to 1 μg kg^?1, respectively, without additional purification/enrichment for these analytical targets. The developed method was applied for the analysis of five different batches of rice bran protein samples. It was found that these four pesticide residues were all below 0.02 mg kg^?1, well less than the maximum residue levels (MRLs) in the latest regulations in EU and China (0.1–5 mg kg^?1). Besides the rice bran protein powder, this suspect screen followed with targeted quantification approach by LC-HRMS could also be applied for other rice derivative products analysis.