Extraction of aroma compounds of fruit juices by air stripping using a bubble column operating with antifoam and its effect on juice properties

Online Scavenging of Trace Analytes in Complex Matrices for Fast Analysis by Carbon Dioxide Bubbling Extraction Coupled with Gas Chromatography-Mass Spectrometry

Carbon dioxide (CO₂) microbubbles can selectively enrich organic solutes from sea spray aerosols. Common bubbling extractions are normally followed by off-line separation/detection through methods such as mass spectrometry, chromatography, and spectroscopy. However, it is necessary to establish extractions with online separation and identification systems to improve efficiency and minimize sample loss. In this study, CO₂ is used to form microbubbles in the sample solution, and trace analytes in the solution are transported to the gas phase by bubble bursting. Analytes at the liquid-gas interface are directly released into the trapping device, followed by thermal desorption for gas chromatography-mass spectrometry. For polycyclic aromatic hydrocarbons, the dependence of the extraction efficiency on various parameters has been analyzed. The method reported here provides high efficiency and minimizes the loss of trace volatiles with a better signal strength and signal-to-noise ratio than other gases. These features make the proposed method a rapid method to detect and quantify volatile/semivolatile analytes in complex liquid matrices. In addition to the preconcentration of organics, metal ions, and inorganic anions, a noticeable decrease of metal-organic compounds in the aqueous solution was shown for the first time. We finally propose a simple model of chemical partitioning in CO₂ bubbling extraction of liquid samples for guiding online monitoring of trace analytes in real-world samples.

Extraction of Green Tea Phenolics Using Water Bubbled with Gases

Water was bubbled with gases including nitrogen (N₂ ), oxygen (O₂ ), hydrogen (H₂ ), carbon dioxide (CO₂ ), and air for 10 min and phenolics from green tea leaves were extracted using the prepared gas-bubbled water. To retain the gases in water, the extraction conditions were maintained in an air-tight container at room temperature under magnetic stirring. Radical scavenging ability, total phenolic content, and phenolic profiles of the extracts were analyzed, and gas-bubbled water was examined to explain the differences in phenolic contents. Overall, green tea infusion prepared from H₂ -bubbled water contained significantly high levels of total phenolic compounds and antioxidant activity compared to other gas-bubbled waters including N₂ , O₂ , CO₂ , and air (P < 0.05).Control samples and those bubbled with CO₂ showed the lowest antioxidant activities in green tea infusion. However, green tea extracts with O₂ bubbling showed the lowest catechin content. Green tea leaves treated with hydrogen gas-bubbled water had much greater damage to their surface morphological properties compared to the other groups, which may explain the higher yield of phenolic compounds. Overall, hydrogen gas-bubbled water showed better extraction yield of phenolics from green tea leaves than other gas-bubbled water. PRACTICAL APPLICATION: Green tea or green tea infusion has diverse health beneficial functionality due to the presence of phenolic compounds. In this study, different gases including nitrogen, oxygen, hydrogen, and carbon dioxide were treated in water and these gas-bubbled water were used to extract phenolics from green tea leaves. Among them, hydrogen-bubbled water extracted the highest phenolic contents from tea leaves and showed the highest in vitro antioxidant ability in green tea infusion compared to other gas-bubbled water. This new knowledge could help to produce green teas with higher antioxidant activity in beverage industry.

On-line coupling of fizzy extraction with gas chromatography

Fizzy extraction (FE) is carried out by first dissolving a carrier gas (typically, carbon dioxide) in a liquid sample at a moderate pressure (typically, 150 kPa) and then rapidly depressurizing the sample. The depressurization leads to instant release of numerous microbubbles in the liquid matrix. The abruptly released gas extracts the volatile solutes and elutes them toward a detector in a short period of time. Here, we describe on-line coupling of FE with gas chromatography (GC). The two platforms are highly compatible and could be combined following several modifications of the interface and adjustments of the extraction sequence. The analytes are released within a short period of time (1.5 s). Thus, the chromatographic peaks are satisfactorily narrow. There is no need to trap the extracted analytes in a loop or on a sorbent, as it is done in standard headspace and microextraction methods. The approach requires only minor sample pretreatment. The main parameters of the FE-GC-mass spectrometry (MS) method were optimized. The results of FE were compared with those of headspace flushing (scavenging headspace vapors), and the enhancement factors were in the order of ~ 2 to 13 (for various analytes). The limits of detection for some of the tested analytes were lower in the proposed FE-GC-MS method than in FE combined with atmospheric pressure chemical ionization MS. The method was further tested in analyses of selected real samples (apple flavor milk, mixed fruit and vegetable juice drink, mango flavored drink, pineapple green tea, toothpaste, and yogurt). Graphical abstract.