Simultaneous quantitation of volatile compounds in citrus beverage through stir bar sorptive extraction coupled with thermal desorption-programmed temperature vaporization

Development and comprehensive SBSE-GC/Q-TOF-MS analysis optimization, comparison, and evaluation of different mulberry varieties volatile flavor

Optimization of seven parameters of stir bar sorptive extraction (SBSE) on mulberry volatile components for the first time. A total of 347 volatile components were identified and quantified in 14 mulberry varieties, predominantly encompassing esters, aldehydes, terpenoids, hydrocarbons, ketones, alcohols, heterocyclics, acids, and phenols. Hexanal and (E)-2-hexenal were the dominant volatiles. Furthermore, 79 volatile compounds characterized by odor activity values (OAVs) > 1 were identified, making a significant contribution to the distinctive mulberry flavor. "Green" notes were the most intense, followed by "fatty" and "fruity". Utilizing odor ring charts, the volatile flavor characteristics of the 14 mulberry varieties could be intuitively distinguished. This study not only established a viable methodology for differentiating mulberry varieties but also laid a theoretical foundation for the quality evaluation and variety breeding of mulberry flavor.

Insights into crucial odourants dominating the characteristic flavour of citrus-white teas prepared from citrus reticulata Blanco 'Chachiensis' and Camellia sinensis 'Fudingdabai'

Citrus-white teas (CWs), which possess a balanced flavour of tea and citrus, are becoming more popular worldwide; however, their characteristic flavour and odourants received limited research. Volatile components of two types of CWs prepared from Citrus reticulata Blanco 'Chachiensis' and Camellia sinensis 'Fudingdabai' were comprehensively investigated using a combination of stir bar sorptive extraction and gas chromatography-mass spectrometry (GC-MS). Ninety-nine crucial odourants in the CWs were quantified by applying GC-olfactometry/MS, significant differences were compared, and their odour activity values (OAVs) were calculated. Twenty-two odourants (in total 2628.09 and 1131.18 mg/kg respectively) were further confirmed as traditional CW (CW-A) and innovated CW (CW-B) characteristic flavour crucial contributors which all possessed > 1 OAVs, particularly limonene (72919 in CW-A) and trans-β-ionone (138953 in CW-B). The unravelling of CWs aroma composition will greatly expanding our understanding of tea aroma chemistry and the potential aroma interactions will offer insights into tea blending technologies.

Optimizing Mass Spectrometry Analyses: A Tailored Review on the Utility of Design of Experiments

Mass spectrometry (MS) has emerged as a tool that can analyze nearly all classes of molecules, with its scope rapidly expanding in the areas of post-translational modifications, MS instrumentation, and many others. Yet integration of novel analyte preparatory and purification methods with existing or novel mass spectrometers can introduce new challenges for MS sensitivity. The mechanisms that govern detection by MS are particularly complex and interdependent, including ionization efficiency, ion suppression, and transmission. Performance of both off-line and MS methods can be optimized separately or, when appropriate, simultaneously through statistical designs, broadly referred to as "design of experiments" (DOE). The following review provides a tutorial-like guide into the selection of DOE for MS experiments, the practices for modeling and optimization of response variables, and the available software tools that support DOE implementation in any laboratory. This review comes 3 years after the latest DOE review (Hibbert DB, 2012), which provided a comprehensive overview on the types of designs available and their statistical construction. Since that time, new classes of DOE, such as the definitive screening design, have emerged and new calls have been made for mass spectrometrists to adopt the practice. Rather than exhaustively cover all possible designs, we have highlighted the three most practical DOE classes available to mass spectrometrists. This review further differentiates itself by providing expert recommendations for experimental setup and defining DOE entirely in the context of three case-studies that highlight the utility of different designs to achieve different goals. A step-by-step tutorial is also provided.

Production of medium-chain volatile flavour esters in Pichia pastoris whole-cell biocatalysts with extracellular expression of Saccharomyces cerevisiae acyl-CoA:ethanol O-acyltransferase Eht1 or Eeb1

Medium-chain volatile flavour esters are important molecules since they have extensive applications in food, fragrance, cosmetic, paint and coating industries, which determine different characteristics of aroma or taste in commercial products. Biosynthesis of these compounds by alcoholysis is catalyzed by acyl-CoA:ethanol O-acyltransferases Eht1 or Eeb1 in Saccharomyces cerevisiae. In this study, these two yeast enzymes were selected to explore their preparations as the form of whole cell biocatalysts for the production of volatile flavour esters. Here, the novel whole cell biocatalysts Pichia pastoris yeasts with functional extracellular expression of Eht1 or Eeb1 were constructed. Flavour production was established through an integrated process with coupled enzyme formation and ester biosynthesis in the recombinant yeasts in one pot, leading to the formation of volatile C6–C14 methyl and ethyl esters from wort medium. Interestingly, there is no significant difference between P. pastoris-EHT1 and P. pastoris-EEB1 in substrate preference during flavour biosynthesis, indicating a similar role of Eht1 and Eeb1 in P. pastoris cells, in contradiction with previous findings in S. cerevisiae to some extent. Consequently the study not only provides a greater understanding of these two enzymes in a heterogeneous host, but also demonstrated the positive effect of the recombinant Eht1 and Eeb1 in ester formation by P. pastoris live cells, potentially paving the way towards achieving efficient production of volatile flavour by an integrated biocatalytic system composed of recombinant enzyme production and flavour biosynthesis.