Brand Protection of Food Products by Thermal Desorption-GC/MS
Posted on May 30th, 2017
The flavour of a food or beverage engages far more sensory input than taste alone. From a biological perspective, flavour may be defined as the sum of taste, aroma (smell sensation), texture (touch sensation), and other physical features (e.g. temperature) that create mouthfeel. The contributions of taste and aroma to flavour are made through chemoreception: the physiological response of sensory nerves to the volatile organic chemicals (VOC) released by foods and beverages. Although these VOCs are present at very low concentrations, they activate a highly specialised set of sensory connections in the brain, activating psychological responses that range from instinctual perception of food safety, to recognition of a previously eaten food, to even higher-order associations of a food with a memory or emotion.
Brands realise how important flavour and aroma are to consumer recognition, acceptance, and quality perception of food and beverage products. Often, flavour and/or aroma are the distinctive features that consumers’ desire and, importantly, associate with the product’s brand. However, foods and beverages undergo many chemical changes during processing, storage, and cooking, which can alter their flavour or aroma in both desirable and undesirable ways. For product consistency, it is essential to identify which chemicals are responsible for flavour and aroma that leads to brand recognition, and which change over time or with product handling.
What is Brand Protection?
Though chemical sources of unpleasant odour or taste in food and beverages may be perfectly harmless, consumers associate bad smells and strange tastes with spoiled goods. This negative perception can limit consumer acceptance because people who have had a bad experience with a product are not likely to consume it again, may avoid the entire brand, and often share their bad experience with others. Further products that fail the consumers’ “sniff test” may also call into question a product’s freshness or safety, which in turn, could cause costly product recalls and damage the entire brand.
With both increasing safety regulations and the continued pressure from consumers’ demands for quality taste and shelf like, food and beverage industries have a heightened focus on brand protection. Through their brand, companies communication to their consumers that their products are of the best possible quality. However, building this message requires more than good advertising campaigns – companies need to deliver on their promises with quality products, and consistent product quality does not happen on its own. Companies must analyse their products regularly, identifying and mitigating potential problems before the products hit the market.
VOCs are often essential to a product’s distinctive aroma and flavour. However, VOCs can be altered with product handling, and they can also be the culprits of a bad smell or odd taste. To ensure product consistency from batch to batch, brands consistently monitor VOCs in their products. Food and beverage industries want their consumers to believe that their products are always good and that bad batches never happen. Thus, many major brands conduct these analyses quietly to protect the brand’s reputation. The analysis and monitoring of the VOCs that make a brand distinctive, as well as the management of chemicals that affect flavour and aroma in food and beverages over time or upon processing, is often kept private, proprietary, or confidential. However, some researchers have published the results of their work with GERSTEL products to profile flavour and aroma in consumer goods.
Using the TD-GC/MS for Brand Protection
Thermal processing of foods (e.g. meat, fish, dairy, canned foods) is one of the most essential processes in the food industry because it ensures product safety and increases shelf life. But this transformative process can also lead to chemical changes that yield off-flavour and off-odour compounds. Professor Devin Peterson has reported the application of GERSTEL TD technologies to evaluate the effectiveness of phenolic ingredients in controlling the formation of off-flavour VOCs in ultrahigh temperature-processed milk.1,2 After solid phase extraction (SPE) of milk samples, the investigators employed GC equipped with a selective detector, GERSTEL MultiPurpose Sampler (MPS), GERSTEL Thermal Desorption Unit (TDU), and GERSTEL Cool Injection System (CIS) for the analysis of off-flavour markers 2-acetyle-2-thiazoline, 2-acetyl-1-pyrroline, and methional. This approach allowed for accurate analysis of milk samples in a fully automated manner, minimizing man power and maximizing speed and efficiency to achieve results.
TD is also used extensively by meat, fish, and poultry industries to evaluate the flavour quality of their products. Stir Bar Sorptive Extraction (SBSE) with GERSTEL Twister Polydimethylsiloxane (PDMS)-coated bars has higher capacity and recovery for meat tissue analysis than conventional methods. For example, Twister stir bars were used for SBSE with TD-GC-MS to analyse trace level off-flavour compounds in salmon fillets with high sensitivity (ng/L) and high recovery (>22%).3 The detection of 2-methylisoborneol and geosmin, which give salmon an unpalatable musty and earthy taste, enabled the monitoring of depurated salmon over several days.
PDMS Twisters with TD-GC-MS were also applied to analyse low-abundance off-flavour chemicals in grilled beef using the GERSTEL Thermal Desorption System (TDS) equipped with GERSTEL MPS and CIS.4 With low detection limits, the method resulted in the analysis of 57 volatile (31 flavour) compounds, including aldehydes, hydrocarbons, alcohols, ketones, pyrazines, and nitrogen – and sulphur – containing compounds in ground grilled beef and grilled beef dripping samples.
Understanding the flavour and aroma changes of food products over time provides a foundation for improving food processing and ingredient strategies. Professor Michael Qian at Oregon State University evaluated the aroma profile of early – and late – harvest pinot noir grapes to aid winemakers in assessing the right time to harvest grapes.5 Analysis of volatile phenols, vanillin, and methyl anthranilate, which could be useful indicators of pinot noir flavour and aroma, was conducted on a GC-MS coupled to GERSTEL MPS-TDU-CIS after extraction with the Twister SBSE method. Notably, analysis of the benzene-derived VOCs failed with a solid phase microextraction (SPME)-GC-MS system due to low concentrations and low affinity to SPME fibres. Thus, the study validated the use of Twister SBSE for the extraction of ultra-trace flavour and aroma chemicals in complex matrices.
Prof. Qian also analysed fresh and aged lemon-flavoured hard iced tea samples via Twister SBSE-TD-GC-MS using GERSTEL MPS-TDU-CIS. The investigators analysed several types of volatile odorants, including alcohols, esters, aldehydes, furanones, phenols, C13-norisoprenoids, and terpenoids.6 This analysis led the investigators to determine the class of compounds responsible for significantly reducing the lemon aroma intensity and the minty fresh flavours in the iced tea product after 1 year of storage.
The GERSTEL MPS can also be configured as a headspace autosampler for GC-MS analysis of VOCs. Due to the low concentration of VOCs in food samples, scientists at GERSTEL developed the Hot Injection and Trapping (HIT) method to collect multiple headspace injections for the introduction of a more concentrated sample into the gas chromatograph, consequently improving limits of detection. The HIT method involves a headspace-configured GERSTEL MPS and a GERSTEL TDU to desorb the analytes that are subsequently trapped in a GERSTEL CIS before entering the GC column. GERSTEL scientists showed HIT’s applicability in detecting VOCs in canned coffee (e.g. furfuryl methyl disulphide) and water (e.g. geosmin, 2,4,6 Trichloroanisole, and 2-methylisoborneol).
Taken together, these studies highlight GERSTEL’s TD capabilities for the detection of low-abundance flavour and aroma chemicals by GC methods from original food and beverage samples. For the analysis of VOCs in food products, GERSTEL technologies contribute to ensuring reliable and consistent results, which are fundamental for the brand protection of food and beverage industries.
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1. A. D. Troise, A. Fiore, A. Colantuono, S. Kokkinidou, G. G. Peterson, V. Fogliano. Effect of olive mill wastewater phenol compounds on reactive carbonyl species and maillard reaction end-products in ultrahigh-temperature-treated milk. J. Agric. Food Chem. 62:10092-10100 (2014).
2. S. Kokkinidou and D. G. Peterson. Control of maillard-type off-flavour development in ultrahigh-temperature-processed bovine milk by phenolic chemistry. J. Agric. Food Chem. 62:8023-8033 (2014).
3. E. D. Ruan, J. L. Aalhus, S. T. Summerfelt, J. Davidson, B. Swift, M. Juarez. Determination of off-flavour compounds, 2-methylisoborneol and geosmin, in salmon fillets using stir bar sorptive extraction-thermal desorption coupled with gas chromatography-mass spectrometry. J. Chromatogr. A 1321:133-136 (2013).
4. E. D. Ruan, J. L. Aalhus, M. Juarez, H. Sabik. Analysis of volatile and flavour compounds in grilled lean beef by stir bar sorptive extraction and thermal desorption-gas chromatography mass spectrometry. Food Anal. Methods 8:363-370 (2015).
5. F Yuan, M. C. Qian. Aroma potential in early – and late – maturity pinot noir grapes evaluated by aroma extract dilution analysis. J. Agric, Food Chem. 64:443-450 (2016).
6. F. Yuan, F. He, Y. Qian, J. Zheng, M. C. Quian. Aroma stability of lemon-flavoured hard ice tea assessed by chirality and aroma extract dilution analysis. J. Agric. Food Chem. 64:5717-5723 (2016).
This article is published, edited for the UK market, with the kind permission of GERSTEL US.