Using GC-MS to Investigate the Aroma Composition of Cheese

A recent study by the Department of Bioscience and Technology for Food, Agriculture and Environment at the University of Teramo (Italy) investigated the contribution of Kluyveromyces marxianus to the gross composition and aroma profile of cow cheeses. The volatile organic compounds were extracted by head-space solid phase micro-extraction and analyzed by gas chromatography-mass spectrometry (GC-MS) coupled with odor activity values. The authors published their research in Frontiers in Microbiology (1).

The characteristics of cheese are influenced by several factors, including the type of milk used, the diet of the animals, the ripening conditions, the length of ripening, and the microbiota (2). Kluyveromyces marxianus is one of the most interesting dairy yeasts because it is thermotolerant, known to grow at temperatures as high as 42 °C. However, it is also able to develop at refrigerated temperatures (3,4). K. marxianus strains affect the ripening of cheese by their proteolytic and lipolytic activities, as well as the formation of volatile aroma compounds (5,6). This yeast species metabolizes lactose as carbon source due to the expression of the LAC12 and LAC4 genes, which code for a lactose permease and a β-galactosidase, respectively (7).

K. marxianus FM09 was used to make experimental cheese, with cheese made using a LAB commercial starter being used as the control group, and the gross composition and the volatile profile of the cheeses were determined. Aroma components were identified through the GC-MS process by comparing the retention times of pure reference standards tested under the same conditions. The volatile compounds were quantified using the calibration curve of standards, and odor activity values (OAV; the ratio of a single compound’s concentration to that compound’s odor threshold) were used to describe the intensity of odor compounds in the sample. When a compound has OAV > 1, it is considered to contribute to the overall aroma of the sample. The analyses were performed in triplicate (1).

A total of 55 volatile compounds were detected in the cheeses, including 10 organic acids, 13 higher alcohols, 17 esters, 7 aldehydes, and 8 ketones. The content of higher alcohols was higher in cheeses obtained with FM09 + CC (1,079 μg/kg) than in the others (660.19 μg/kg). The most abundant were isoamyl alcohol (fusel, alcoholic, whiskey, fruity, banana), 1-octanol (waxy, green, orange, aldehydic, rose, mushroom), 2-butanol (sweet, apricot), and 2-phenylethanol (floral, sweet, rose) (1).

To summarize, the study determined that the inoculation of K. marxianus FM09 induced an increase of esters, higher alcohols, organic acids, and ketones, as well as the production of key volatile compounds was observed. These results demonstrated the potential of K. marxianus FM09 as co-adjunct culture, even if further studies are necessary to better investigate the interactions of the strains used and the cheese microbiota. The metabolic pathways of K. marxianus involved in the definition of cheese characteristics should be highlighted using multi -omics approaches (1).

Different kinds of cheese on table. © Africa Studio- stock.adobe.com

References

1. Perpetuini, G.; Rossetti, A. P.; Rapagnetta, A.; Tofalo, R. Unlocking the Potential of Kluyveromyces marxianus in the Definition of Aroma Composition of Cheeses. Front Microbiol. 2024, 15, 1464953. DOI: 10.3389/fmicb.2024.1464953

2. Mayo, B.; Rodríguez, J.; Vázquez, L.; Flórez, A. B. Microbial Interactions Within the Cheese Ecosystem and their Application to Improve Quality and Safety. Food Secur. 2021, 10, 602. DOI: 10.3390/foods10030602

3. Fonseca, G. G.; Heinzle, E.; Wittmann, C.; Gombert, A. K. The Yeast Kluyveromyces marxianus and its Biotechnological Potential. Appl. Microbiol. Biotechnol. 2008, 79, 339–354. DOI: 10.1007/s00253-008-1458-6

4. Tofalo, R.; Fasoli, G.; Schirone, M.; Perpetuini, G.; Pepe, A., Corsetti, A. et al. The Predominance, Biodiversity and Biotechnological Properties of Kluyveromyces marxianus in the Production of Pecorino di Farindola Cheese. Int. J. Food Microbiol. 2014, 187, 41–49. DOI: 10.1016/j.ijfoodmicro.2014.06.029

5. Binetti, A.; Carrasco, M.; Reinheimer, J.; Suárez, V. Yeasts from Autochthonal Cheese Starters: Technological and Functional Properties. J. Appl. Microbiol. 2013, 115, 434–444. DOI: 10.1111/jam.12228

6. Padilla, B.; Belloch, C.; López-Díez, J. J.; Flores, M.; Manzanares, P. Potential Impact of Dairy Yeasts on the Typical Flavour of Traditional Ewes' and Goats' Cheeses. Int. Dairy J. 2014, 35, 122–129. DOI: 10.1016/j.idairyj.2013.11.002

7. Varela, J. A.; Montini, N.; Scully, D.; Van der Ploeg, R.; Oreb, M.; Boles, E., et al. Polymorphisms in the LAC12 Gene Explain Lactose Utilisation Variability in Kluyveromyces marxianus Strains. FEMS Yeast Res. 2017, 17, fox021. DOI: 10.1093/femsyr/fox021