Evaluating Pasteurization Methods for Improved Milk Flavor Using GC-MS and GC-SCD

Although heat treatment of milk is an indispensable process for ensuring microbiological safety and extending the shelf life of milk, ultrahigh temperature (UHT)-processed milk results in undesirable cooked flavors. An increasing trend exists toward approaches using multivariate analysis based on the concept that flavor is a composite of volatile compounds. Japanese researchers evaluating whether alternating-current high electric field (AC-HEF) pasteurization improves the flavor quality of milk compared with conventional UHT treatment profiled volatile compounds were profiled using solid-phase microextraction gas chromatography (GC)-mass spectrometry with a targeted aroma database (~500 compounds) and GC-sulfur chemiluminescence detection (GC-SCD) for sulfur-containing volatiles. A paper based on their efforts was published in the Journal of Dairy Science.¹

The causes for unintended, unpleasant tastes or odors in heat-treated milk, as well as their remedy, have long been central themes in dairy science over the past century.² In Japan, UHT-processed milk (defined as being heated at 120–150°C for 1–3 s, as specified by the country’s 1951 Ministerial ordinance on milk and milk products concerning compositional standards) accounts for over 90% of the milk sold. However, UHT processing (which inactivates spores and enzymes and extends shelf life) results in the development of the undesirable “cooked” flavors for the milk, including sulfurous odors and browning-associated flavors.^3-5Flavor differences such as these can possibly create an obstacle to consumers’ acceptance of milk processed with UHT.^6-8

Raw milk from a single batch was processed using AC-HEF (115°C, 20 s) or UHT (135°C, 2-3 s) treatment. Sensory evaluation involved a 120-member consumer panel and a trained panel; in addition, differential addition tests were performed for key aroma compounds identified using multivariate analysis. Consumers rated AC-HEF milk higher for its pleasant aroma and aftertaste. Multivariate analysis indicated that hexanal and butyl acetate were characteristic of AC-HEF milk, whereas 1-octen-3-one was more abundant in UHT milk. Spike-in tests showed that the addition of hexanal to UHT milk improved the perception, whereas 1-octen-3-one addition to AC-HEF milk produced undesirable results. GC-SCD confirmed significantly higher levels of carbon disulfide in UHT milk.¹

“These results,” write the authors of the paper,¹ “suggest that AC-HEF processing enhances favorable flavor attributes by suppressing off-flavor formation while maintaining the levels of aromatic volatiles. Thus, AC-HEF represents a promising alternative to UHT for producing shelf-stable milk with an improved flavor profile.”

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References

1. Matsumoto, M.; Yamada, T.; Takemori Y. Comparison Between the Flavor Profiles of Milk Pasteurized Using Alternating-Current High Electric Field and Ultra-High Temperature. J Dairy Sci. 2026, S0022-0302 (26), 00237-7. DOI: 10.3168/jds.2025-27838
2. Barbano, D. M. A 100-Year Review: The Production of Fluid (market) Milk.J. Dairy Sci. 2017, 100, 9894-9902. DOI: 10.3168/jds.2017-13561
3. Deeth, H. Improving UHT processing and UHT milk products; in Improving the Safety and Quality of Milk. Volume 1: Milk Production and Processing; Woodhead Publishing Limited, 2010; 302-329
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5. Lan, L.; Wang, W.; Su, Y. et al. Exploration of Milk Flavor: From the Perspective of Raw Milk, Pasteurized Milk, and UHT Milk.Food Chem. X. 2025, 25, 102083. DOI: 10.1016/j.fochx.2024.102083
6. Chapman, K. W.; Boor, K. J. Acceptance of 2% Ultra-Pasteurized Milk by Consumers, 6 to 11 Years Old.J. Dairy Sci. 2001, 84, 951-954. DOI: 10.3168/jds.S0022-0302(01)74553-5
7. Perkins, M. L.; Deeth, H. C. A Survey of Australian Consumers' Attitudes Towards UHT Milk.Aust. J. Dairy Technol. 2001, 56, 28-34
8. Lee, A. P.; Barbano, D. M.; Drake, M. A. The Influence of Ultra-Pasteurization by Indirect Heating Versus Direct Steam Injection on Skim and 2% Fat Milks. J. Dairy Sci. 2017, 100, 1688-1701. DOI: 10.3168/jds.2016-11899