Electronic nose gauges levels of volatile compounds, taints.

As you know, it is important to consumers that the products they eat do not take up the odor or taste of the material in which they are packaged. If the odor or flavor of a foodstuff is foreign to the product, then the question is a matter of taint.

Many volatile compounds are responsible for taints. The migration of these compounds from packaging material to the product may occur either through the air space or as a result of direct contact with the product. Additional difficulties may occur if you use impermeable wrapping films on the outside of a packaged product because they prevent the evaporation of volatiles from, for example, printing inks.

Foods vary in their susceptibility to agents that cause taints. Fat-soluble compounds migrate easily to fats, oils and fatty foods, whereas water-soluble compounds migrate to aqueous foods. Particularly sensitive are products with a high area-to-volume ratio, such as powders.

Traditional methods for analyzing taints in foods include instrumental headspace gas chromatography, headspace gas chromatography-mass spectrometry, gas chromatography-sniffing systems and human sensory evalution. The electronic nose is becoming more widely used for determining the quality of foods and their packaging. Electronic noses are faster and more precise in making determinations, compared with the traditional approaches. But there sometimes are challenges in calibrating the devices.

Scientists at Finland's VTT Biotechnology combined the data gathered from an electronic nose with traditional analytical techniques to measure levels of volatile compounds in products. The researchers used an electronic nose to analyze the impact of different coloring agents on the sensory properties of packaging materials.

The investigators learned that the odor of the packaging itself was often not a reliable indicator of a taint that had been perceived. The electronic nose was successful in analyzing taints caused by the pigments found in printed solid packaging boards. The nose grouped the boards according to the coloring agents and type of lacquer used. This was achieved despite an overlapping of some samples. The results appeared to reflect to some extent the off-flavors perceived during human sensory evaluation.

Care must be taken when correlating results between different sensory and instrumental methods. For instance, the odor perceived during sensory evaluation is not exactly comparable with the amount and quality of volatile compounds measured from a similar sample headspace using an electronic nose or gas chromatography-mass spectrometry system.

VTT scientists are continuing their research, as these results are only preliminary. They will use statistical multicomparison methods in their future work.

Further information. Raija-Liisa Heinio, VTT Biotechnology, P.O. Box 1500, FIN-02044 VTT, Tietotie 2, Espoo, Finland; phone: [phone]; fax: [phone]; URL: www.vtt.fi/bel.