Matrix Effects in Detection of Phthalate Esters from Wheat by a Modified QuEChERS Method with GC/MS

Simultaneous determination of sixteen phthalic acid esters (PAEs) in soil and evaluation of matrix effect using a QuEChERS/GC/MS-internal standard method

Phthalic acid esters (PAEs) are emerging pollutants that need to be analyzed precisely. Chromatography-based determination of PAE content in soils are frequently affected by matrix effect, which may limit the quantification of different kinds of PAEs from different types of soil. Here we optimized a QuEChERS protocol combined with gas chromatography-mass spectrometry (GC-MS) for simultaneous determination of 16 PAEs in different soils. PAEs in different type of soils (fluvo-aquic soil, red soil, and black soil) were extracted with acetonitrile followed by GC-MS detection based on quantitative ion internal standard method. All 16 PAEs showed excellent linear relationships with mass peak areas (R2 > 0.99). The limits of detection (LOD) and limits of quantitation (LOQ) of all the samples were in the range of 0.91-66.97 µg/kg and 2.7-200.9 µg/kg, respectively. The accurate test at 0.5, 0.1, and 1.0 mg/kg spiking level recorded recovery rate between 80.11% and 100.99% with relative standard deviations (RSDs) ranging from 0.37 to 8.50% in tested matrices. No significant matrix effect was observed for most tested PAEs. This is a simple method with high sensitivity and strong stability, which is suitable and reproducible for quantifying large number of PAEs in different types of soil.

Nanotechnology-based optical sensors for Baijiu quality and safety control

Baijiu quality and safety have received considerable attention owing to the gradual increase in its consumption. However, owing to the unique and complex process of Baijiu production, issues leading to quality and safety concerns may occur during the manufacturing process. Therefore, establishing appropriate analytical methods is necessary for Baijiu quality assurance and process control. Nanomaterial (NM)-based optical sensing techniques have garnered widespread interest because of their unique advantages. However, comprehensive studies on nano-optical sensing technology for quality and safety control of Baijiu are lacking. In this review, we systematically summarize NM-based optical sensor applications for the accurate detection and quantification of analytes closely related to Baijiu quality and safety. Furthermore, we evaluate the sensing mechanisms for each application. Finally, we discuss the challenges nanotechnology poses for Baijiu analysis and future trends. Overall, nanotechnological approaches provide a potentially useful alternative for simplifying Baijiu analysis and improving final product quality and safety.

Phthalate ester (PAEs) accumulation in wheat tissues and dynamic changes of rhizosphere microorganisms in the field with plastic-film residue

Phthalates acid esters (PAEs) have accumulated in soil and crops like wheat as a result of the widespread usage of plastic films. It is yet unclear, nevertheless, how these dynamic variations in PAE accumulation in wheat tissues relate to rhizosphere bacteria in the field. In this work, a field root-bag experiment was conducted to examine the changes of PAEs accumulation in the rhizosphere soil and wheat tissues under film residue conditions at four different growth stages of wheat, and to clarify the roles played by the microbial community in the alterations. Results showed that the plastic film residues significantly increased the concentrations of PAEs in soils, wheat roots, straw and grains. The maximum ΣPAEs concentration in soils and different wheat tissues appeared at the maturity, with the ΣPAEs concentration of 1.57 mg kg-1, 4.77 mg kg-1, 5.21 mg kg-1, 1.81 mg kg-1 for rhizosphere soils, wheat roots, straw and grains, respectively. The plastic film residues significantly changed the functions and components of the bacterial community, increased the stochastic processes of the bacterial community assembly, and reduced the complexity and stability of the bacterial network. In addition, the present study identified some bacteria associated with plastic film residues and PAEs degradation in key-stone taxa, and their relative abundances were positive related to the ΣPAEs concentration in soils. The PAEs content and key-stone taxa in rhizosphere soil play a crucial role in the formation of rhizosphere soil bacterial communities. This field study provides valuable information for better understanding the role of microorganisms in the complex system consisting of film residue, soil and crops.

Fusion-based strategy of CSA and mobile NIR for the quantification of free fatty acid in wheat varieties coupled with chemometrics

The use of sensor fusion, a novel method of combining artificial senses, has become increasingly popular in the assessment of food quality. This study employed a combination of the colorimetric sensor array (CSA) and mobile near-infrared (NIR) spectroscopy to predict free fatty acids in wheat flour. In conjunction with a partial least squares model, Low- and mid-level fusion strategies were used for quantification. Accordingly, performance of the built model was evaluated based on higher correlation coefficients between calibration and prediction (R_C and R_P), lower root mean square error of prediction (RMSEP), and a higher residual predictive deviation (RPD). The mid-level fusion coupled PLS model produced superior data fusion findings, with R_C = 0.8793, RMSECV = 7.91 mg/100 g, R_P = 0.8747, RMSEP = 6.99 mg/100 g, and RPD = 2.27. The findings of the study suggest that the NIR-CSA fusion approach could be effectively applied to the prediction of free fatty acids in wheat flour.

The content of PAEs in field soils caused by the residual film has a periodical peak

The wide use of plastic film mulch has led to the release of phthalate esters (PAEs), which seriously threatens the soil environment and the safety of crop production. However, it is unknown whether there is a maximum threshold of soil PAEs accumulation induced by plastic film residue, and the dynamic changes of soil PAEs under field conditions are still unclear. To address these issues, a field experiment was conducted to investigate the temporal fluctuations of soil PAEs content and the response of microbial community structure in the field with plastic film residue. Results showed that the content of soil PAEs fluctuated during an observation period of one year, had a periodical peak in winter and summer, and was exacerbated by the increase in the aging degree and residual amount of plastic films. The PAEs content in soil with black films was higher than the US soil allowable criteria. High-throughput sequencing analysis showed that the addition of residual film significantly increased the alpha diversity of bacterial communities, changed the structure of bacterial community, and generated significant disturbances in bacterial function. Besides, the residual film recruited more microbiota related to plastic film and PAEs degradation. Results of the present study provide insight into the dynamic variation of soil PAEs caused by plastic film residue in one year, which is important to help evaluate the pollution risk of PAEs on soils and crops caused by residual plastic film.

Effects of film mulching on the distribution of phthalate esters in wheat grains from dryland

The application of plastic film in field crop production elevated the phthalate esters (PAEs) accumulation in wheat grains, which poses potential risks to human health. However, the variation of grain PAEs contents in different dryland areas is not clear, and the distribution of PAEs in different tissues of grains has not been studied yet. In the present study, field experiments in five sites (three provinces) with two treatments (soil with and without film mulching) were carried out to study the concentration and distribution of PAEs in grains and the effects of environmental factors on them. Results showed that the total PAE concentration (∑PAEs) in wheat grains ranged from 445 to 764 μg/kg, mainly in the forms of di-(2-ethylhexyl)-phthalate (DEHP), dibutyl phthalate (DBP), and diisobutyl phthalate (DIBP). Compared with control, total PAE concentrations in soils and wheat grains were significantly higher in treatments with film mulching. The effects of film on the proportion of PAEs in the flour and bran varied with experiment sites. Grain PAEs in the control groups presented significantly negative correlation with annual temperature, while there was a positive correlation between soil PAEs and bran PAEs in the film treatment. Results in this study are of great significance to comprehensively evaluate the effect of film mulching on grain safety in dryland wheat production.

Simple method for determining phthalate diesters and their metabolites in seafood species using QuEChERS extraction and liquid chromatography-high resolution mass spectrometry

In this article we describe a new and simple analytical method based on the Quick, Easy, Cheap, Effective, Rugged and Safe technique followed by dispersive solid-phase extraction clean-up with C₁₈ and Lipifiltr® and LC-HRMS for simultaneously extracting six phthalate diesters and six of their metabolites (phthalate monoesters) from highly consumed seafood species. The method was validated for seafood with high and low lipid contents. Apparent recoveries were up to 79% for all compounds. Matrix effect values ranged from -8 to -48% for all compounds in both types of matrices. Method limits of detection were 1-25 ng g^-1 dry weight (d.w.) for most compounds. Five seafood species were analysed using this method, and several phthalate diesters and monoesters were successfully quantified. Phthalate diesters were found at concentrations of up to 982 ng g^-1 (d.w.) and phthalate monoesters were found at concentrations of up to 178 ng g^-1 (d.w.).

Interactions between p-Cresol and Ala-Lys-Arg-Ala (AKRA) from Sesame-Flavor-Type Baijiu

The objective of this study was to investigate the influence of Ala-Lys-Arg-Ala (AKRA), a tetrapeptide newly identified from Chinese Sesame flavor-type Baijiu in our previous work, on its binding ability with aroma compounds. A method using headspace solid-phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME-GC/MS) was employed to determine the corresponding binding ability between different concentrations of AKRA (10 - 1000 μg/L) and aromas in Baijiu. In comparison, the aroma molecules in Baijiu before and after adding AKRA were almost the same; only their volatility was altered, with mostly the esters, alcohols, and phenolic compounds being decreased. Additionally, AKRA slightly changed the whole aroma profile of Baijiu, especially with respect to p-cresol (an off-odor in sesame-flavor-type Baijiu), which was verified by systematic sensory experiments including gas chromatography-olfactometry (GC-O) and odor activity values (OAVs) analysis. The nonvolatile tetrapeptide favored the hydrogen bond interactions with p-cresol, forming the AKRA- p-cresol complex, thus reducing the headspace concentration of phenolic off-flavors as evidenced by HS-SPME-GC/MS, ultraviolet (UV) absorption spectroscopy, and nuclear magnetic resonance spectrum (¹H NMR) analysis. Meanwhile, the hydrogen bond interaction was further confirmed with the intermolecular cross-peaks between the carboxyl hydrogen of AKRA and the phenolic hydroxyl of p-cresol by nuclear Overhauser effect spectroscopy (¹H-¹H NOESY).

Structural characterization of a tetrapeptide from Sesame flavor-type Baijiu and its interactions with aroma compounds

The small molecules in Chinese Baijiu have been widely reported, but there is little information on peptides since their low concentrations. A tetrapeptide, Asp-Arg-Ala-Arg (DRAR), was newly identified from Jingzhi Sesame flavor-type Baijiu (SFTB) by high-performance liquid chromatography and quadrupole-time-of-flight-mass spectrometry (HPLC-Q-TOF-MS) with a concentration of 13.159 ± 0.202 μg/L (P > 0.05). Interactions between DRAR and volatile compounds were characterized using headspace solid-phase micro-extraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS), and the results indicated that DRAR could suppress the volatility of aroma compounds by 0.09-39.02 %, especially with respect to esters and alcohols. The involved binding modes of DRAR with esters or alcohols in 46% ethanol/water solutions (v/v) were respectively determined by ultraviolet (UV) absorption spectroscopy. According to the Van't Hoff equation, the thermodynamic parameters (for DRAR - esters complex, ΔH = -34.7 KJ mol^-1, ΔS = -66.4 J mol^-1 K^-1 and for DRAR - alcohols complex, ΔH = -40.8 KJ mol^-1, ΔS = -91.8 J mol^-1 K^-1) indicated that hydrogen bonds and van der Waals forces played major roles in stabilizing the DRAR-esters and DRAR-alcohols complexes. This study will help us to further understand the interaction mechanisms between aroma compounds and peptides, and the important role of peptides on the quality of Chinese Baijiu.