Due to their typical sensory profile, beverages like fruit juice and soft drinks have a very positive consumer image. Customers especially appreciate their fruit profile. Whether a flavor is considered to be an off-flavor depends on the food matrix. A good example is vinyl guaiacol. Vinyl guajacol is a positive flavor note in wheat beer but an off-flavor in orange juice. Diacetyl is a positive flavor in milk but an undesired flavor in fruit beverages.
During shelf storage and processing, native flavoring components, like aldehydes, are lost, and components that negatively change the sensory profile of the beverage accumulate. Temperature and light accelerate these changes. Some off-flavors can also be of microbiological origin.
Typical examples of off-flavors identified in orange juice are vinyl guaiacol and hydroxy-dimethyl-furanone. Both molecules derive from native orange juice components. Vinyl guajacol is generated from esters of ferulic acid natively present in oranges. Furanone is built up during the maillard reaction from sugars, amino acids and ascorbic acid. Modern analytical techniques like GC/MS and HPLC/MS have been helpful to identify and quantify the components.
Sensory off-flavor markers
For manufacturers of beverages, it is very important to describe off-flavors via their taste and smell. The sensory impact of an off-flavor on the final food product has to be determined by sensory tests.
Therefore it is important to find valid sensory markers for characteristic off-flavors. These molecules should be recognizable by panelists at low levels in a fruit juice matrix.
As a first approach, guaiacol, furaneol and methional, known to be present in stored orange juice, are applied to orange juice at ppm levels. Via sensory threshold values and difference tests, these three components could be proven to be valid off-flavor markers in orange juice. Guaiacol has a phenolic character, furaneol smells bread-like, and methional is linked to cooked flavor notes.
These sensory attributes are not positive for the sensory profile of orange juice.
Sensory panelists are usually very experienced at recognizing positive markers like freshness and fruity attributes linked to fruit esters and aldehydes. To identify off-flavors, panelists can now be easily trained using the above markers for off-flavors.
Outlook – The Search Goes On
In the future, additional beverages should be put through stress tests at accelerated temperature and light. Additional off-flavors have to be identified, their sensory attributes have to be described and their impact on final beverages have to be evaluated.
In parallel to stress tests, storage conditions on the shelf have to be simulated to verify the importance of these components. These conditions are different from region to region depending on the respective climatic conditions.
The target is to deliver beverages to customers that are as close as possible to fresh products. The routes for off-flavor development have to be identified to keep off-flavor development at a minimum.
Educating panelists to detect these negative sensory markers in beverages is of great importance to receive a high customer acceptance for beverages.
- Schiebele, P., Hofmann, T., Dechent, H.M.. Untersuchungen zur Aromacharakterisierung bei der Herstellung und Lagerung von Orangensaft aus Konzentrat im Vergleich zu Direktsaft. Forschungskreis der Ernährungsindustrie e.V. (FEI), Bonn, 1998-2001. http://www.fei-bonn.de/gefoerderte-projekte/projektdatenbank/aif-11569-n.projekt
- Haug, M., Hellfeier, F., Hambitzer, R.. Dem off-flavour auf der Spur. Lebensmitteltechnik, 1-2/2015, 31 (Bericht, Editorial)
- Haug, M., Hellfeier, F., Hambitzer, R.. Fehlaromen, Entstehung und deren Beurteilung in Getränken GDL-Symposium Aromen und Aromatisieren von Lebensmitteln, 01./02. Dezember 2014, Stuttgart
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