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The total tetramethylpyrazine (TMP) content in vinegar samples could be detected by multiple HS-SPME coupled with GC-FID (MHS-SPME-GC-FID) as a routine method. Unlike the traditional HS-SPME method, only one working curve built with different levels of standard aqueous solutions in the MHS-SPME-GC-FID method was able to calibrate the total TMP level from different matrixes (calibration standards ranging from 0.05 to 5.00 μg mL−1, R2 = 0.9986). In addition, the developed method was sensitive to the determination of TMP in vinegars (the limit of detection of 1 μg L−1, the limit of quantification of 5 μg L−1). In addition, the excellent recovery at 0.10 μg mL−1, 1.00 μg mL−1 and 5.00 μg mL−1 of TMP (ranging from 81.01% to 113.5%) and good reproducibility of the method (inter-day RSD 7.79%, intra-day RSD 3.94%) confirmed that the developed method was accurate and stable for the analysis of vinegar samples. Moreover, the detection results in real samples were consistent with the results from the traditional HS-SPME-GC-FID corrected by external standard method. In conclusion, the uniqueness of the working curve and the absence of matrix effect in MHS-SPME-GC-FID method were useful for rapidly obtaining comparable data from liquid samples with different matrix.

Abalone is one of the most valuable seafood products and the quality of ready-to-eat abalone products could be improved through tenderization treatments prior to a fully cooking process. In this study, a tenderization process (80 °C for 2 h) was applied to improve the quality properties of baked abalone muscle for the developing of ready-to-eat products. The quality properties of baked abalone (150–210 °C, 10–30 min) with and without pre-tenderization treatment prior to baking were evaluated through sensory evaluation, textural analysis and Hunter Lab colorimeter. In addition, amounts of sugars and α-dicarbonyl compounds in these products were determined via HPLC analyses. The baking condition at 180 °C for 20 min combined with pre-tenderization resulted in an optimal product. The baked abalone with pre-tenderization had better textural properties (hardness, 1031.12 ± 101.67; springiness, 0.96 ± 0.02; chewiness, 817.13 ± 113.43; shear, 2843.92 ± 35.67), sensory scores (30.1 ± 2.9) and color (25.28 ± 1.21) as compared to the baked abalone without pre-tenderization (hardness, 1990.91 ± 252.35; springiness, 0.87 ± 0.01; chewiness, 1164.43 ± 195.64; shear, 3910.79 ± 302.12; sensory score, 17.4 ± 1.0; color, 15.91 ± 0.74). The reducing sugar analysis indicated the presence of ribose and glucose in the baked abalone. In addition, the formation of α-dicarbonyl compounds (degraded from reducing sugars) including glucosone, 3-deoxyglucosone, glyoxal, methylglyoxal, and diacetyl were significantly promoted by the tenderization process in the baked abalone muscle. And the tenderization treatment led to an average of 218% increase in α-dicarbonyl compounds in the baked abalone muscle. The promotion of the formation of α-dicarbonyl compounds by the tenderization treatment contributed to the accumulation of pigments in the final baked products and led to desirable color.

Vortex-assisted liquid-liquid micro-extraction (VALLME) was applied for eliminating the matrix effect and improving the sensitivity of eugenol determination by headspace solid phase micro-extraction (HS-SPME) coupled with gas chromatography-mass spectrometer (GC-MS) in fish samples. Under the optimum condition of VALLME and HS-SPME, the good linearity of eugenol in fish samples was obtained in the range from 15.0 to 750.0 μg/kg. The limit of detection (LOD) and the limit of quantification (LOQ) for eugenol were 0.5 and 1.5 μg/kg, respectively. The recovery of eugenol was ranging from 95.4 to 119.9% and the relative standard deviation (RSD %) for eugenol was lower than 20%. The results turned out that VALLME followed HS-SPME-GC-MS was a simple, rapid, and accurate method for the determination of eugenol in fish samples. The levels of eugenol in different parts of real samples were tested by the developed method, and the results concluded that the developed method was compatible with GC-MS analysis with long-term application and had excellent repeatability, linearity, and sensitivity.

A new, rapid, and inexpensive method using two-step ultrasonic assisted liquid–liquid micro-extraction (UALLME) coupled with capillary electrophoresis-ultraviolet (CE-UV) was developed for 5-hydroxymethylfurfural (HMF) analysis in high ion strength samples (like vinegar and soy sauce). The factors affecting the extraction efficiency were optimized such as the extraction volume, the ultrasonic time, and the power density of ultrasonic. Under the optimum conditions, the limit of detection (LOD) and the limit of quantification (LOQ) for HMF were 0.03 and 0.10 mg/L, respectively. The relative standard deviations (RSD %) for HMF were ranging from 0.53 to 3.17%, and the recoveries of HMF were ranging from 91.24 to 109.39%. The results turned out that two-step UALLME-CE-UV was applicable to analyze HMF in vinegar and soy sauce. Eleven brands of vinegar and soy sauce were tested by two-step UALLME-CE-UV, and the results showed that the method had a potential application in analysis of foodstuffs. The two step UALLME method was effective to improve the selectivity and sensitivity of CE-UV method for HMF analysis in vinegar and soy sauce.

Vortex-assisted liquid–liquid microextraction (VALLME) is a fast and simple pretreatment method, which has been applied for the clean-up of beverages containing caramel color. Herein, a reversed-phase C18 column (50 mm × 2.5 mm, 2 μm) was used, and the MS/MS instrument was operated in the multiple reaction monitoring mode for the sensitive and selective detection of 5-hydroxymethyl-2-furaldehyde (HMF). The matrix effect and detection stability were corrected using the isotope dilution method. This method demonstrated low limit of quantification (0.3 μg L−1) and excellent linearity (R2 = 0.999). The recovery rates of HMF ranged from 87.5% to 101.0% in carbonated drinks and from 85.1% to 98.7% in soft drinks. The content of HMF was quantified in thirteen beverage samples, ranging from 0.2 to 14.8 mg L−1. In conclusion, the VALLME coupled with the HPLC-ESI-MS/MS method is a valid and rapid technique for isotope dilution quantification of HMF in beverages.

The concentration of tetramethylpyrazine (TMP) in vinegar is an active indicator of vinegar quality. Dispersive liquid–liquid microextraction (DLLME) was first applied to vinegar as a clean-up pre-treatment for the rapid (5 min) determination of TMP by high-pressure liquid chromatography with ultraviolet detection (HPLC-UV), and may serve as an alternative to solid-phase extraction (SPE) or solid-phase microextraction (SPME). High sensitivity of HPLC for TMP determination was obtained using the DLLME pretreatment, with a limit of detection (LOD) of 0.001 mg L−1 and limit of quantification (LOQ) of 0.005 mg L−1. The developed method exhibited excellent linearity in the concentration range of 0.050–80.000 mg L−1, with a correlation coefficient R2 > 0.999. Furthermore, the percentage recovery of TMP in vinegar using the developed method was within the range 97.97–105.24%. Therefore, DLLME coupled with HPLC-UV is a sensitive and promising method for vinegar clean-up and TMP assay.

In this study, a rapid and reliable pretreatment method called dispersive liquid-liquid microextraction (DLLME) was developed for the determination of 4(5)-methylimidazole (4-MeI) in beverages. The clean-up samples were analyzed by a high performance liquid chromatography coupled with triple quadrupole mass spectrometer (HPLC–MS/MS) using a reversed-phase C18 column (250 mm × 4.6 mm, 5 μm). The matrix effects and the fault of DLLME operation were corrected by the isotope dilution technique. The developed method exhibited the limit of quantification (0.3 μg L−1) and excellent linearity (R2 = 0.999). In addition, the recovery values of 4-MeI in carbonated beverage were ranging from 102.60% to 113.22%, in soft drinks were ranging from 103.24% to 108.85%. The content 4-MeI was detected in thirteen beverage samples treated with DLLME and solid phase extraction method (SPE) (ranging from 6.4 to 165.5 μg L−1). The consistent result of 4-MeI content detected by DLLME and SPE method concluded that the established method on the basis of DLLME was rapid, robust and accurate for the trace 4-MeI determination in beverages.