Food Analytical Methods

A simple and reliable analytical method based on ultra-high performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) was developed and validated for the simultaneous determination of total isoflavone aglycones and its metabolite equol in egg yolk. The seven target analytes were separated on an Acquity ultra performance liquid chromatography (UPLC) system BEH C18 column with gradient elution and detected by electrospray ionization source (ESI) operating in negative subsection acquisition mode under multiple reaction monitoring (MRM) conditions. The results showed that the recoveries of spiked isoflavones and equol from the matrices were satisfactory, ranging between 73.74 and 89.35%, and all with relative standard deviation (RSD) values below 10%. The linearity of their corresponding concentration ranges from 2 to 500 ng/mL with correlation coefficients (r2) all higher than 0.99. The analytes were stable under the experimental conditions and the proposed method exhibited good recovery and reproducibility within only 8 min. The measurement results showed that the tested eggs contained soy isoflavones and equol, which may be beneficial for people who lack estrogens and those with hormone-related disorders. This method can also be useful for the determination of isoflavones and equol in other animal products.

Lipidomic strategies have been applied to many methodologies, such as species differentiation and lipid-associated disease identification. In this study, we first applied a lipidomic strategy coupled with UPLC-Q-Exactive Orbitrap mass spectrometry to investigate the differences between reconstituted milk and ultra-high temperature sterilization (UHT) milk. Fifteen lipids were selected as biomarkers to identify UHT and reconstituted milk by OPLS-DA method. Furthermore, a discriminant model to identify reconstituted milk from UHT milk was established based on these biomarkers. This robust discriminative model provided a strong technical proof to promote the development of the market norms concerning the identification of UHT and reconstituted milk.

A type of quartz wool-supported surface dummy molecularly imprinted silica (QW@MIP) was prepared using bisphenol AF as the template molecule for solid-phase extraction of bisphenol A (BPA). The QW@MIP was characterized by FT-IR spectroscopy, scanning electron microscopy, and thermo-gravimetric analysis. The adsorption tests showed that the QW@MIP had high-adsorption ability and a fast binding kinetics for BPA. When used as a solid-phase extraction (SPE) sorbent for BPA, the QW@MIP showed ease of packing SPE cartridge, low flow resistance, high extraction efficiency, high enrichment factor, and good reusability. Moreover, the dummy-imprinting technique used herein can effectively avoid the interference of residual template molecules in sorbent to determination of BPA. A new SPE method was developed using the QW@MIP sorbent, and then coupled with a high-performance liquid chromatography method, it was successfully applied to the detection of BPA spiked in water samples and orange juice and that in a certified sample with recoveries of 96.7–103.1% (RSD = 1.0–2.8%), 96.9–99.9% (RSD = 1.0–2.9%), and 99.2% (RSD = 0.5%), respectively. The limit of detection (S/N = 3) and limit of quantification (S/N = 10) for all samples were 0.05 and 0.17 ng mL−1, respectively. The QW@MIP can be potentially used as a good SPE sorbent for BPA in environmental water samples and beverages.

An air-agitated cloud-point extraction procedure (AACPE), which is a new generation of cloud-point extraction procedure, has been investigated for extraction and preconcentration of four heterocyclic amines (i.e., 2-Amino-3,4-dimethyl-3H-imidazo[4,5-f]quinoline (MeIQ), 2-Amino-3,4,8-trimethyl-3H-imidazo[4,5-f]quinoxaline (4,8-DiMeIQx), 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), and 1-methyl-9H-pyrido[3,4-B]indole (harmane)) prior to high-performance liquid chromatography (HPLC). In order to enhance the extraction efficiency, the mixture of the aqueous sample solution and extraction solvent (Triton X-114) was repeatedly aspirated and dispensed using a syringe. Various parameters affecting the extraction efficiency of the AACPE procedure, including type and amount of salt, concentration of Triton X-114, extraction time (or number of air agitations), and centrifugation time, were investigated. No temperature controller was necessary. Under the optimum extraction condition, the linearity was achieved between 0.005 and 1.00 mg kg−1 with the correlation coefficient (R 2) > 0.999. The low limit of detections (LODs) ranged from 0.001 to 0.003 mg kg−1 with high enrichment factor (EF) more than 80. Matrix-matched calibration has been used for analysis of the target analytes in real samples. The applicability of the developed procedure was successfully evaluated by the determination of the heterocyclic amines in smoked sausage samples.

Black soybeans have been reported to contain high antioxidant content, including anthocyanins. Ultrasound-assisted water extraction of antioxidants from Korean black soybeans (Glycine max [L.] Merr. Cheongja4ho) was investigated for the first time. A three-level, three-factor Box-Behnken design using a response surface methodology (RSM) was employed to optimize the conditions for the maximum yields of three dependent variables, including total anthocyanin content, total phenol content, and 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging activity, based on 17 different experiments. The solid-liquid ratio (X1, 1/30–1/50 g mL−1), extraction time (X2, 1–9 min), and amplitude (X3, 20–100%) significantly affected three dependent variables. The optimized conditions were solid-liquid ratio of 49.1 g mL−1, extraction time of 8.59 min, and amplitude of 81.4%. At the optimum point, the total anthocyanin content, total phenol content, and ABTS•+ scavenging activity were 66.44, 940.96, and 242.45 mg 100 g−1. The difference (%) between the predicted and experimental values was less than 6.40%, indicating that the model fits well. The conditions optimized for ultrasound-assisted water extraction of antioxidants from black soybeans can be applied as an efficient technique for extracting anthocyanins in plants on a larger scale.

This work presents a study to evaluate the migration of lead to cooked foods prepared in clay pots produced in a small community in Brazil. Clay pots produced in Maragogipinho, Bahia, Brazil, go through an artisanal vitrification process by the addition of lead oxide to improve the visual appearance of the pot. To evaluate the migration of the lead to the food, samples of a fish-based delicacy (fish stew), with and without palm oil and coconut milk, were taken at different moments of contact with the clay container after cooking. Determination of lead concentrations was performed by inductively coupled plasma optical emission spectrometry (ICP-OES), and the concentrations found were higher than 2.0 mg kg−1, which is the value regulated by the Brazilian Health Regulatory Agency. In addition, the highest concentrations of lead were detected in samples with a longer contact time with the pan. The longer the contact time was, the higher the lead content that migrated to the food. These results suggest that cooking and storing foods in the glazed clay pots pose a potential risk of lead contamination.