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The volatile organic compounds (VOCs) produced during cider fermentation, maturation, and dry hopping greatly impact enjoyment of the final product. To investigate the effect of apple variety on VOC development in cider, five apple varieties were picked from two orchards in southwest Colorado. Each apple variety was juiced, fermented with Lalvin QA23 Saccharomyces cerevisiae, dry-hopped with Citra hops, and analyzed separately alongside non-dry hopped controls. The aroma attributes of these historical southwest Colorado apples have never been explored, and few studies have chemically profiled the aromas of dry-hopped cider. A total of 73 VOCs were identified using headspace-solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) from fruit juice to cider. Ethyl esters, acetate esters, higher alcohols, and terpenes were the major aroma contributors observed in dry-hopped cider. The identity and concentrations of VOCs varied greatly between apple varieties, with only 24 common VOCs detected in all samples studied. This indicates the importance of apple variety choice in tuning the aroma profile of the finished cider. This method can be used to more effectively evaluate orchard or cider production treatments on cider quality. This case study also provides practical information for cider makers seeking to improve the quality of their products through consideration of fruit variety and dry hopping. Supplemental data for this article is available online at https://doi.org/10.1080/03610470.2021.2013645. [ABSTRACT FROM AUTHOR]

Cider quality and consumer acceptance are greatly influenced by its aroma. With the continued expansion of the craft cider industry, cider producers are employing techniques such as dry hopping to develop unique flavor profiles. Few studies, however, have explored the VOCs of dry-hopped cider. Herein, we monitor the development of VOCs from pressed apple juice, through fermentation and dry hopping by HS–SPME–GC–MS, to elucidate when and how aroma compounds arise in cider production. In all, 89 VOCs were detected, spanning eight classes of organic compounds. Racking events decreased ester concentrations by 10 ± 1%, but resting on the lees allowed these pleasant, fruity aromas to be reestablished. Dry hopping was conducted with three types of hops (Citra, Galaxy, and Mosaic). The varied development of terpenes and esters between hop varieties supports the use of this technique to diversify the aroma profiles of ciders. Herein, we report that both the variety of hops and the timing of key processing steps including racking and hop addition significantly alter the identity and concentration of aroma-important VOCs in dry-hopped cider. [ABSTRACT FROM AUTHOR]

Azines are important in many extraterrestrial environments, from the atmosphere of Titan to the interstellar medium. They have been implicated as possible carriers of the diffuse interstellar bands in astronomy, indicating their persistence in interstellar space. Most importantly, they constitute the basic building blocks of DNA and RNA, so their chemical reactivity in these environments has significant astrobiological implications. In addition, N and O atoms are widely observed in the ISM and in the ionospheres of planets and moons. However, the chemical reactions of molecular anions with abundant interstellar and atmospheric atomic species are largely unexplored. In this paper, gas-phase reactions of deprotonated anions of benzene, pyridine, pyridazine, pyrimidine, pyrazine, and s-triazine with N and O atoms are studied both experimentally and computationally. In all cases, the major reaction channel is associative electron detachment; these reactions are particularly important since they control the balance between negative ions and free electron densities. The reactions of the azine anions with N atoms exhibit larger rate constants than reactions of corresponding chain anions. The reactions of azine anions with O atoms are even more rapid, with complex product patterns for different reactants. The mechanisms are studied theoretically by employing density functional theory; spin conversion is found to be important in determining some product distributions. The rich gas-phase chemistry observed in this work provides a better understanding of ion-atom reactions and their contributions to ionospheric chemistry as well as the chemical processing that occurs in the boundary layers between diffuse and dense interstellar clouds. [ABSTRACT FROM AUTHOR]

A central focus of astrobiology isthe determination of abioticformation routes to important biomolecules. The dissociation mechanismsof these molecules lend valuable insights into their synthesis pathways.Because of the detection of organic anions in the interstellar medium(ISM), it is imperative to study their role in these syntheses. Thiswork aims to experimentally and computationally examine deprotonatedadenine and guanine dissociation in an effort to illuminate potentialanionic precursors to purine formation. Collision-induced dissociation(CID) products and their branching fractions are experimentally measuredusing an ion trap mass spectrometer. Deprotonated guanine dissociatesprimarily by deammoniation (97%) with minor losses of carbodiimide(HNCNH) and/or cyanamide (NH2CN), and isocyanic acid (HNCO).Deprotonated adenine fragments by loss of hydrogen cyanide and/orisocyanide (HCN/HNC; 90%) and carbodiimide (HNCNH) and/or cyanamide(NH2CN; 10%). Tandem mass spectrometry (MSn) experiments reveal that deprotonated guanine fragmentslose additional HCN and CO, while deprotonated adenine fragments successivelylose HNC and HCN. Every neutral fragment observed in this study hasbeen detected in the ISM, highlighting the potential for nucleobasessuch as these to form in such environments. Lastly, the acidity ofabundant fragment ions is experimentally bracketed. Theoretical calculationsat the B3LYP/6-311++G(d,p) level of theory are performed to delineatethe mechanisms of dissociation and analyze the energies of reactants,intermediates, transition states, and products of these CID processes. [ABSTRACT FROM AUTHOR]

Studies of interstellar chemistry have grown in number and complexity by both observations and laboratory measurements, and nitrogen-containing aromatics have been implicated as important interstellar molecules. In this paper, the gas-phase collision induced dissociation (CID) processes of protonated pyridazine (1,2-diazine), pyrimidine (1,3-diazine), and pyrazine (1,4-diazine) cations (C4H5N2 + ) are investigated in detail both experimentally and theoretically. The major neutral loss for all three CID processes is HCN, leading to the formation of C3H4N+ isomers; our density functional theory (DFT) calculations support and elucidate our experimental results. The formation of C3H4N+ isomers from the reaction of abundant interstellar acrylonitrile (CH2CHCN) and H+ is also studied employing DFT calculations. Our results lead to a novel mechanism for interstellar protonated diazine formation from the consecutive reactions of CH2CHCN + H+ + HCN. Moreover, our results motivate the continuing search for interstellar C3H4N+ isomers as well as polycyclic aromatic N-containing hydrocarbons (PANHs). [ABSTRACT FROM AUTHOR]

Propene (CH3CHCH2), detected in the cold core TMC-1, is a surprisingly saturated (H-rich) species for observation in such regions. In a recently proposed gas-phase formation mechanism, interstellar propene is produced from its protonated precursor C3H+7 (CH3CHCH+3 ) via a dissociative recombination process. The precursor ion C3H+7 is itself produced via two consecutive radiative association reactions involving H2 starting from the isomer of C3H+3 with a linear carbon backbone (CH2CCH+). Initial calculations showed that the radiative association reactions are efficient enough to allow the production of an abundance of propene equal to that observed. However, a combination of experiments and more refined quantum chemical ab initio calculations reported here does not corroborate the initial result. Indeed, from both of these approaches, we have learned that the radiative association reactions leading to protonated propene do not occur efficiently at interstellar temperatures due to activation energy barriers. The result is that propene cannot be produced efficiently by the suggested gas-phase synthetic route. It is still difficult to say, however, that no suitable gas-phase syntheses for propene can occur in cold cores such as TMC-1. [ABSTRACT FROM AUTHOR]