Gas Chromatography-Mass Spectrometry (GC-MS) Analysis for Apple Wine Fermentation
In this study, GC-MS was utilized to monitor the development of volatile compounds during the fermentation of apple wine. Two methods were employed: Dynamic Headspace Extraction (DHE) and Solid Phase Microextraction (SPME), both coupled with GC-MS.
The GC-MS system was equipped with a DB-WAX capillary column (30m x 0.25mm x 0.50µm) using hydrogen as a carrier gas, set to a flow rate of 1 ml/min. Volatile compounds were separated in the gas chromatograph with a temperature program ranging from 30°C to 240°C. The mass spectrometer scanned ions with m/z ratios between 15 and 300, allowing for comprehensive detection of a wide range of compounds.
Yeast Species Used:
Three yeast species were used for fermentation:
– *Lachancea thermotolerans* (L. thermotolerans)
– *Torulaspora delbrueckii* (T. delbrueckii)
– *Saccharomyces cerevisiae* (S. cerevisiae)
These species were selected for their ability to influence the volatile profile of fermenting apple juice. They were monitored throughout the fermentation to observe how each contributed to the development of aromatic compounds.
Methods Overview:
– Dynamic Headspace Extraction (DHE): Volatiles were continuously purged from samples with nitrogen gas and trapped on Tenax-TA. Thermal desorption was used to release the volatiles for GC-MS analysis. This method yielded detailed results, identifying 48 volatile compounds.
– Solid Phase Microextraction (SPME): A fiber was exposed to the sample headspace, capturing volatile compounds which were later desorbed in the GC injector port. This method identified 21 volatile compounds and required minimal sample handling, making it highly automated.
File Naming Convention:
Samples were labeled with single or duplicate letters based on the yeast species:
– “C” and “CC” for *L. thermotolerans*
– “P” and “PP” for *T. delbrueckii*
– “S” and “SS” for *S. cerevisiae*
For example, “C” refers to a single sample of *L. thermotolerans*, while “CC” refers to its duplicate. The data collection followed a sequence (C → P → S → CC → PP → SS), and samples were taken at regular intervals during the fermentation process.
Results:
The GC-MS analysis successfully identified key volatile compounds, including esters, alcohols, ketones, and aldehydes, formed during fermentation. Principal component analysis was used to differentiate the fermentation stages and yeast species based on the volatiles’ development profiles.
This method provides a detailed, time-resolved insight into the production of aroma compounds during apple wine fermentation and can be applied to various fermentation processes.
Data:
The GC-MS data is provided as CDF files. The data was generated as part of a bachelor project by Mads Cort Nielsen. The project was supervised by Mikael Agerlin Petersen
