Comparison of amino acid, 5'-nucleotide and lipid metabolism of oysters (Crassostrea gigas Thunberg) captured in different seasons.

As an important aquaculture shellfish, the superior taste and high nutritional value of oyster (Crassostrea gigas Thunberg) have drawn extensive attention. In this study, twenty-one free amino acids (FAAs) and six 5'-nucleotides were evaluated through stable isotope labeling-liquid chromatography coupled with tandem mass spectrometry (SIL-LC-MS/MS), and the lipid profile was explored using ultrahigh performance liquid chromatography-Q Exactive HF mass spectrometry (UHPLC-QE/MS). The adductor muscle of the oyster possessed a high level of sweetness-related amino acids (Arg, Gly and Hyp) and 5'-nucleotides. A total of 149 lipid species were detected in different tissues of oysters, including 17 triacylglycerols (TAGs), 6 diacylglycerols (DAGs), 61 phosphatidylcholines (PCs), 29 phosphatidylethanolamines (PEs), 11 lysophosphatidylcholines (LPCs), 8 lysophosphatidylethanolamines (LPEs), and 1 lysophosphatidylinositol (LPI). FAAs, 5'-nucleotides and lipid profile in the digestive gland of oysters can be divided into three stages, from November to April, May to July, and August to October. The highest proportion of umami-taste amino acids and 5'-nucleotides appeared from March to May. The highest percentage of high unsaturation degree glyceride and phospholipids appeared in August and April, respectively. Thus, the results reported in this study are important for product development and sustainable exploitation in the future.

Simultaneous Determination of Acrylamide, 5-Hydroxymethylfurfural, and Heterocyclic Aromatic Amines in Thermally Processed Foods by Ultrahigh-Performance Liquid Chromatography Coupled with a Q Exactive HF-X Mass Spectrometer.

In this study, a rapid and reliable method based on ultrahigh-performance liquid chromatography coupled with Q Exactive HF-X mass spectrometry (UHPLC-QE/MS) was established for the simultaneous quantification and validation of acrylamide, 5-hydroxymethylfurfural, and 14 heterocyclic aromatic amines in thermally processed foods. With the optimization of the pretreatment method, all 16 hazardous compounds with different polarities were simultaneously extracted and purified by one-step purification. By studying various acquisition modes in detail, full MS + PRM detection using an electrospray ionization source in the positive mode gives an excellent-shaped chromatographic peak and thereby achieves a better quantitative ability for analytes in the matrix. This method demonstrated good quantification recovery in the range of 68.85-146.42%. The limits of quantification were within the range from 0.1 to 50 ng/mL. With the method proposed, the simultaneous determination of 16 hazardous compounds in different thermally processed foods was successfully applied. The all-fragment-ion approaches at high resolution have the ability to reduce false-positive peak detections arising from peak alignment software in the detection of samples significantly. The proposed isotope dilution UHPLC-QE/MS method was validated and demonstrated to be sensitive, accurate, and precise for the simultaneous quantification of multiple contaminants in one injection.

Changes in Aroma Profile of Shiitake Mushroom (Lentinus edodes) during Different Stages of Hot Air Drying.

To clarify the changes in the aroma characteristics of shiitake mushrooms (Lentinus edodes) during hot-air drying, volatile compounds of L. edodes were analyzed using sensory evaluation, electronic nose, and purge and trap combined with gas chromatography-mass spectrometry (PT-GC-MS) at different timepoints of the drying process. Results showed that the sensory and volatile profile changed significantly during the drying process at 60 °C for up to 12 h and the drying process could be divided into three stages: early stage (<2 h), middle stage (2-3.5 h) and late stage (>3.5 h). Volatile compounds in fresh L. edodes consisted mainly of ketones and alcohols. The early stage of drying decreased the concentration of ketone and alcohol compounds and promoted the generation of cyclic organosulfur compounds through a series of enzymatic and non-enzymatic reactions, which mainly contribute to the characteristic odor of shiitake mushroom. Partial least squares-discriminant analysis (PLS-DA) showed that the volatile compounds released after different drying times could be divided into four groups, which have been confirmed by sensory evaluation results. The results suggested that the unique flavor of dried mushrooms is mainly due to the activation of enzymes during the drying process, which act on lentinic acid to produce sulfur-containing heterocyclic compounds. We believe that our study makes a potential contribution to the mushroom cultivation and processing industry to achieve an improvement in sensory quality.