Measuring Volatile Organic Compounds with GC in Chinese Bacon

Scientists from the Shaanxi University of Technology in Hanzhong, China used various analytical techniques to identify various volatile organic compounds (VOCs) in different types of Chinese bacon. Their findings were published in the Journal of Chromatography A (1).

Chinese traditional cuisine bacon on wooden table | Image Credit: © Govan - stock.adobe.com

Chinese bacon is known for having a distinctive flavor compared with other pork products. Mainly created from pork belly, it is either air-cured with soy sauce, brown sugar, and spices (like star anise and cinnamon) until it's very hard, or it's cured for a shorter period before being smoked (2). It can be classified into smoked and non-smoked bacons, with each type having a unique flavor profile influenced by regional manufacturing techniques. The primary distinction between non-smoked and smoked bacon lies in their production techniques, which result in different profiles of volatile compounds specific to bacon from various regions. Aroma stems from the integration of various volatile organic compounds (VOCs), with Chinese bacon containing abundant volatile compounds, such as acids, aldehydes, ketones, alcohols, esters, and hydrocarbons. The smoking process is a critical factor in determining bacon’s aroma, with the flavor profile of these products being increasingly noted by consumers.

A previous study, “Aroma and flavor characteristics of commercial Chinese traditional bacon from different geographical regions,” established a sensory dictionary to evaluate traditional Chinese bacons, providing descriptive adjectives based on their specific aromatic characteristics (3). Gas chromatography-mass spectrometry (GC–MS) and electronic nose (E-nose) have been used to investigate these volatile metabolites, with GC–MS coupled with gas chromatography-ion mobility spectrometry (GC–IMS) being one of the most popular methods. However, there has been minimal investigation into the composition of volatile compounds in smoked and non-smoked bacons. For this study, two types of Chinese bacon were examined from four regions (Hunan, Sichuan, Zhenba, and Guangxi). Each of these regions have well-known types of bacon in China, each with a unique flavor profile. GC–MS and GC–IMS were used together to achieve better isomer separation while preserving the original flavor of the bacon samples.

The characteristic bacon flavor substances were identified using fingerprint analysis and quantitatively analyzed by ion migration spectrum. This technique proved useful for rapidly identifying VOCs present in the bacon samples. Guangxi bacon lacks a smoky aroma, which sets it apart from the other types. However, it contains many esters that play a crucial role in its flavor profile. In contrast, phenols, including guaiacol, which is typical in smoked bacon, were present in the bacon from Sichuan, Hunan, and Shaanxi but were absent in Guangxi bacon. Furthermore, Hunan bacon exhibited a higher aldehyde content than Sichuan bacon. 2-methyl-propanol and 3-methyl-butanol were identified as characteristic flavor compounds of Zhenba bacon. The Hunan bacon was shown to have more aldehydes than the Sichuan bacon, likely due to converting alcohols into aldehydes during longer smoking and processing times. Further, guaiacol emerged as a characteristic flavor substance in Chinese bacon, which is capable of distinguishing between smoked and non-smoked bacon. Overall, this study provides a theoretical foundation for understanding and identifying the flavor profiles of Chinese bacon. Using various analytical techniques to investigate the flavor compounds is essential for effectively distinguishing bacon from different regions.

References

(1) Qu, D.; Xi, L.; Li, Y.; Yang, H.; et al. Characterizing the Composition of Volatile Compounds in Different Types of Chinese Bacon Using GC–MS, E-Nose, and GC–IMS. J. Chromatogr. A 2024, 1730, 465056. DOI: 10.1016/j.chroma.2024.465056

(2) Wang, C. Lacquered Chinese Bacon Recipe. Dotdash Meredith 2022. https://www.seriouseats.com/lacquered-chinese-bacon-recipe (accessed 2024-7-11)

(3) Wang, H.; Zhang, X.; Suo, H.; Zhao, X.; Kan, J. Aroma and Flavor Characteristics of Commercial Chinese Traditional Bacon from Different Geographical Regions. J. Sens. Stud. 2018, 34 (1), e12475. DOI: 10.1111/joss.12475