Garlic: Allicin, Forms & How to Use It

Allicin is the central active compound that gives garlic its typical smell and its pungency – and the crucial point about it: the whole, intact clove contains no allicin at all. It only forms the moment you cut, crush or chew the clove. Then the odourless precursor alliin meets the enzyme alliinase, and within seconds allicin forms. This is precisely why an undamaged head of garlic barely smells – and a freshly chopped one all the more intensely.

Picture a Mediterranean kitchen: as soon as the blade passes through the clove, that unmistakable aroma hangs in the air. What happens chemically here is a small masterpiece of plant biology – and it also explains why raw and cooked garlic taste so different and why, with garlic preparations, so much depends on the processing.

Key facts at a glance

• Garlic (Allium sativum) belongs to the allium family – related to onion, leek and chives.
• Allicin only forms when the clove is cut, from the precursor alliin.
• Allicin is unstable and rapidly converts into further sulphur compounds (ajoene, sulphides).
• Available as a fresh clove, powder, oil macerate, black garlic and low-odour extract.
• No health claims are currently authorised for garlic in the EU – we describe it as a cultivated and culinary plant.

Where garlic comes from

Garlic originally comes from Central Asia and belongs to the genus Allium. Underground, the plant forms a head made of several cloves, each enclosed in a papery skin. Today it is grown worldwide – China, India and the Mediterranean region are among the most important areas. Depending on the variety, a distinction is made between white and violet garlic as well as varieties with and without a flower stalk.

Even in the ancient civilisations of Egypt, Greece and Rome, garlic was firmly established – as a culinary and cultural plant that has accompanied people in the kitchen and everyday life for thousands of years. This is a cultural-historical account of the traditional culinary use, not a health-related promise.

What happens in the clove: the allicin principle

The garlic plant's trick is separate storage. In the intact clove, two building blocks lie spatially separated from each other: the odourless amino-acid compound alliin and the enzyme alliinase. As long as the cell walls are intact, nothing happens – the clove barely smells. Only when you cut, crush or chew it do the cell walls break open, the two meet, and the alliinase converts alliin into allicin in a flash. This is the compound responsible for the characteristic smell.

Allicin, however, is a fleeting companion: it is chemically unstable and converts further within minutes – into compounds such as ajoene and various di- and trisulphides. In practical terms this means: whether and how much allicin forms depends greatly on what you do with the clove. A tried-and-tested kitchen trick: chop the clove and then let it rest for a few minutes before it goes into the pan. That gives the enzyme reaction time.

Heat and acid intervene in this interplay. If you throw garlic into hot fat immediately after peeling, the reaction runs differently than with raw, crushed garlic – one of the reasons why raw and cooked garlic are so far apart in taste. With food supplements you therefore often find the term "allicin potential": the amount of allicin a preparation can release under defined conditions.

The forms compared

The most fascinating special case is black garlic. It forms when fresh cloves mature over weeks under controlled warmth and humidity. In the process they turn deep dark, become soft like a prune and develop a mild, sweetish-balsamic taste – the typical garlic pungency recedes completely into the background. This fermentation shifts the profile of the sulphur compounds markedly; black garlic therefore contains different compounds than fresh garlic. In modern cuisine it has won a firm place – on its own, with cheese or in fine sauces.

Which form is the right one depends on the goal: for cooking you reach for the fresh clove or the powder; anyone who wants to avoid the smell chooses black garlic or low-odour capsules.

Garlic in the kitchen and everyday life

Hardly any ingredient is so versatile: raw in pesto, sautéed in the pan, braised in the oven, as a paste in a dip. A few practical tips that make the difference:

• Fine rather than coarse: the finer you chop or press, the more cell walls break open – the more intense the taste.
• Let it rest: after chopping, wait 5–10 minutes before heat comes into play.
• Don't burn it: garlic quickly turns bitter at too high a heat – better to add it late to the pan.
• Smell on the breath: fresh parsley, milk or apple can somewhat soften the typical sulphur compounds.

Anyone combining garlic with other plant extracts will find basic rules in combining food supplements correctly, and the choice of dosage form is clarified in capsule, tablet, powder or drops.

Storing fresh garlic correctly

Fresh garlic keeps best cool, dry and airy – in an open basket or clay pot, not in the fridge, where the moist environment encourages sprouting and mould. Whole heads stay fresh considerably longer than separated single cloves. If a green sprout appears inside, that is a sign of ageing; the sprout often tastes sharper and is removed by many before cooking. Peeled or chopped garlic should be used up promptly. Dried and fermented forms, by contrast, are shelf-stable and handy for the pantry.

Why so many people reach for garlic

Hardly any plant has become so firmly established in the kitchen across so many cultures and centuries as garlic. In Mediterranean cuisine it is, alongside olive oil and tomatoes, a load-bearing pillar; in Asian cuisine it seasons countless wok dishes; in the home cooking of many countries it simply belongs. This enormous spread is explained above all by taste: garlic brings depth and umami to a dish like hardly any other ingredient, and even a single clove noticeably changes the character of a sauce.

Added to that is the practical aspect: garlic is cheap, available everywhere, keeps for a long time and can be used in countless forms. Anyone who today reaches for low-odour capsules or black garlic often does so to avoid the intense taste and breath smell and still bring garlic into everyday life regularly. This describes what people do – not what garlic does.

Recognising quality

With fresh garlic, firm, plump cloves without sprouts or soft spots are a good sign. With preparations it is worth looking at the standardisation: reputable manufacturers state which value – for instance allicin potential – the extract is standardised to, and have it tested in the laboratory for purity. Why processing and form can be relevant for absorption is explained in bioavailability simply explained. Anyone interested in further sulphur-containing compounds will find a related topic in the guide NAC – N-acetylcysteine, and plant extracts in general are examined in the antioxidants overview as well as quercetin.

Honestly put in context: what the research examines

Garlic is among the most intensively studied foods of all – research has long been interested in its sulphur compounds and their behaviour in the body. What is established here: the biochemistry of allicin formation, the instability of allicin and the different compound profiles of the various forms. That is well-documented textbook knowledge. Less clear-cut and the subject of ongoing discussion are many of the health-related questions – and precisely for this reason no health claims (health claims under Regulation 432/2012) are currently authorised for garlic in the EU.

We deliberately abide by this: for us, garlic is first and foremost a culinary and seasoning herb with fascinating chemistry. We expressly make no statements about an effect on the heart, circulation, blood pressure, blood lipids or other bodily values. Anyone who wants to use garlic as a supplement should see a balanced diet as the basis. In the case of concurrent use of medication – in particular blood thinners – as well as with persistent complaints, please seek medical advice.

Matching products from Scheunengut

In our category black garlic you will find fermented, low-odour products, in the area bitter compounds further plant extracts, and under liver & kidneys related botanical classics. Look for a clear indication of the form – fresh, fermented or standardised extract – as well as for lab-tested quality.

Frequently asked questions (FAQ)

Why does a whole garlic clove barely smell, but a chopped one strongly?

Because the odour-forming allicin does not yet exist at all in the intact clove. There, the odourless precursor alliin and the enzyme alliinase lie spatially separated. Only when you cut or crush the clove do the cell walls break open, the two meet and allicin forms – in seconds. That is why the smell is most intense after cutting.

Does black garlic still have allicin?

Black garlic forms through weeks of fermentation under warmth and humidity. In the process the profile of the sulphur compounds shifts markedly: it contains different compounds than fresh garlic and tastes mild, soft and sweetish rather than sharp. The typical, allicin-dominated aroma recedes almost completely into the background.

Should I let garlic rest after chopping?

In the kitchen this is a tried-and-tested trick. If you let chopped or pressed garlic rest for a few minutes before you heat it, the enzyme reaction is given time to form allicin and its follow-on compounds. If, on the other hand, you throw it straight into hot fat, the reaction runs differently and the taste turns out milder.

Is garlic as a capsule better than fresh?

That cannot be answered across the board and depends on the goal. Fresh cloves deliver the full taste, while low-odour capsules and black garlic score when you want to avoid the garlic smell. With capsules it is worth looking at the standardisation, such as the stated allicin potential. We may not and do not wish to claim a health superiority of any one form.