Volatile Profile Survey of Five Apple Varieties Grown in Southwest Colorado from Juice to Finished, Dry-Hopped Cider

Abstract

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 .

Keywords:

• Cider
• dry hopping
• gas chromatography
• solid phase microextraction
• HS-SPME-GC-MS; volatiles

Acknowledgments

We thank Jared Scott, Elizabeth Philbrick, and Avery Scott of EsoTerra Cider, for their collaborative insights, cider samples, and assistance picking and pressing the apples used in this study. We also thank them greatly for the use of their facilities for sample preparation. Special thanks go to the orchard owners in Hermosa, CO for their Gravenstein apples, and to Beth Lashell and the Old Fort Orchard in Hesperus, CO for their many varieties of crab apples. We are grateful for Benjamin Cole’s design of the graphical abstract included with this manuscript. We acknowledge and thank Marty Emmes, Sam Bingman, Zach Myers, Kelly Bleck, Dr. Gigi Richard, Dr. Michael Grubb, and Dr. Jeff McFarlane for their discussions, edits, advice, and assistance throughout the project. Lastly, our laboratory would not function without the support of several good dogs, cats, and rabbits: thank you especially to O’Malley, Liessel, Ivy, Stuart, and Tilli for your support and cuteness.

Author contributions

Dr. C. Cole, undergraduate students J. Hinkley and M. Bingman, and collaborators Dr. C. Bradley II and Dr. J. Lee implemented the study and interpreted the results together. Undergraduate students J. Hinkley and M. Bingman collected and analyzed all reported experimental data under the mentorship of Dr. C. Cole, Dr. J. Lee, and Dr. C. Bradley II. J. Hinkley prepared the manuscript draft, and manuscript editing was performed by Dr. C. Cole and Dr. C. Bradley II. Dr. C. Cole acquired all funding that supported this work and led project administration and supervision.

Conflicts of interest

The authors declare no conflict of interest.

Additional information

Funding

This work was made possible thanks to the 2019–2020 Undergraduate Analytical Research Program (UARP) grant of the Society for the Analytical Chemists of Pittsburgh (SACP) and the 2019–2020 American Society for Mass Spectrometry Research at PUIs Award funded by Agilent Technologies. We thank these organizations for their financial support of undergraduate research.