Garlic in the kitchen and the medicine cabinet

Garlic is used worldwide as a cooking ingredient and is also consumed for its medicinal properties. UN data indicates that in 2007 at least 15.7 million tonnes of garlic was produced worldwide. Like many other natural products, the flavour of different batches of garlic vary significantly in strength, which therefore needs to be assessed before use by the food industry.

What gives garlic its characteristic taste and smell?

It has been found that the majority of the volatile compounds are thiosulfinates, although the rich variety of compounds that contribute to the flavour and fragrance of garlic stem from the odourless precursor alliin. Rupturing of garlic’s cellular tissue (by processing) causes allicin to be converted enzymatically to allicin, which makes up the majority of the thiosulfinates present in freshly chopped garlic.

Allicin is unstable and decomposes to form a variety of compounds, with the literature pointing to diallyldisulfide as the most overwhelmingly abundant extractant from processed, raw and cooked garlic and the best indicator of the strength of garlic.

Simple, inexpensive analysis

The Oxford technology provides a simple, effective and inexpensive means for the electrochemical detection and quantification of diallydisulfides.

The measurement is carried out after shaking a pureed material in solvent, diluting it and carrying out the analysis using a cheap, disposable screen printed electrode.

This is a one shot analysis that requires little training and can be made even easier by the use of Oxford’s simple electronics module (Oxford University Innovation chilli pepper sensor – project 3675).

This has potential applications in monitoring the batch-to-batch variation and the stability of garlic during storage and also the garlic content of medicinal supplements.

Alternative approaches

Like other flavours in the food industry, garlic batches are often quantified by organoleptic testing, typically based upon the dilution of garlic in sour cream followed by taste testing. Extraction and chromatography are also used. Not only do these require complex equipment and expertise, but they tend to isolate mainly volatile thiosulfinates, whereas most of the flavour and fragrance of garlic comes from the odourless precursor alliin that is enzymatically converted to allicin.

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