Garlic Uncovered: Biology, Chemistry, and Culinary Uses
Introduction to Garlic
Garlic is a plant that is widely used withing every household and professional kitchen. It’s actually the second most grown and used vegetable after the onion. It belongs to the Amaryllidaceae family of plants, and it’s closely related to onions, shallots, chives, and leeks. Although it is native to Central and South Asia and northeastern Iran, it’s now cultivated in temperate and subtropical regions of the world, mainly in China, Korea, India, Bangladesh, the USA, Spain, and Egypt (1).
“Sativum” is the botanical name of garlic, and the direct translation will be “cultivated.” In other languages, it will sound like ‘skérodon’ in ancient Greek, ‘shuim’ in Hebrew, ‘ail’ in French, ‘ajo’ in Spanish, ‘aglio’ in Italian, ’Knoblauch’ in German, and ’suan’ in Chinese (2).
Anatomy of the garlic plant
Garlic is a perennial (any plant that persists for several years) plant which grows from a bulb and has a tall, flat stem that can reach up to a meter long (1 m = 3 ft). The plant can flower in the summer period (July to September) in the Northern Hemisphere (1,2).
The main parts of the plant are the bulb, containing cloves, and the aerial parts, which are above the ground. These include the stem, leaves, scape, and flower.
The most common part used in cooking is the bulb, but the stem, leaves, scape, and flowers are also edible. The green stems, leaves, and scapes grow in the late spring and early summer are perfect when used in salads. These scapes have a typical pig’s tail shape (1,2). They have a mild, less garlicky flavor and can be sautéed, grilled, added to some soups and stews, or simply used in salads or pesto.
The bulb consists of 6–35 smaller bulblets called cloves and is surrounded by a thin white or pinkish papery sheath (1).
The bulb contains up to 35 small bulblets called cloves. They are surrounded by a thin white or pinkish sheath separating them from the rest of the cloves.
Categories of garlic plants
We can categorize garlic into two broad categories—hardneck and softneck. The main differences between them come down to their structure, flavour, but also how they are grown and stored after harvesting. The “neck” in the names refers to the stalk that grows upward from the garlic bulb. Here are the main differences between hardneck and softneck garlic (1,2)
Hardneck Garlic (Allium sativum ssp. Ophioscorodon)
It is the type that produces fewer and larger-sized cloves and has a bold and spicy taste. A nice bonus is that in this variety of garlic the scapes (flower stalks) are edible. This type has a relatively shorter shelf life due to the thinner membranes/skins between the cloves. It only lasts anywhere between three and five months. A very interesting type of hardneck is solo garlic, also called single-clove garlic. It’s a specially harvested and rare type that produces only one large clove instead of multiple ones. Its flavour is much sweeter and milder than regular hardneck garlic. It resembles onion pearls.
Other varieties include the following:
- Chesnok Red – a purple stripe variety known for its sweet, rich flavor when roasted.
- German Extra Hardy – Porcelain type with robust flavor and big cloves.
- Purple Stripe Garlics – vibrant skins, complex flavor, excellent for roasting.
- Purple Glazer – mild, smooth taste, easy to peel.
- Rocambole (hot and spicy flavor)
- Porcelain (satin white with musky flavor and 4 cloves per bulb).
- Creole
- Middle Eastern
- Turban
Softneck Garlic (Allium sativum ssp. sativum)
Contains more, but smaller, cloves, which are tightly packed. Its smell and taste are much milder. Because of the presence of more skin/membrane tissue between the cloves, it has a relatively longer shelf life. It grows in hotter regions. It does not produce scapes. You are most probably buying this type of garlic in grocery stores.
Varieties of these will include:
- California Early White – mild, early harvest, great for braiding.
- California Late White – heat-tolerant with excellent shelf life.
- Organic Purple Italian – full flavor, perfect for roasting.
- Inchelium Red – an award-winning softneck with mild, nutty flavor.
- Blanco Piacenza
- California Early and Late Whites
- Corsican Red
- Inchelium Red
- Silver Rose
- Silver White
- French Red
Other types of “Garlic”?
Garlic-Like Plants and Their Key Features
These include:
- Elephant garlic (Allium ampeloprasum var. ampeloprasum), which is a type of leek plant. It has very large bulbs with onion-like flavour.
- Allium ursinum (Wild Garlic, Ramsons): a wild species with strong garlic scent.
- Allium vineale (Crow Garlic, Wild Onion): a wild plant that resembles an onion. It has garlic–onion flavor.
- Allium tuberosum (Chinese Garlic Chives): a herb used in Asian cuisine with mild garlicky aroma.
- Allium scorodoprasum (Serpent Garlic, Field Garlic): an Allium species with a garlic-like taste.
- Tulbaghia violacea (Society Garlic): a plant from a different family (Amaryllidaceae). It is edible, with pleasant garlicky flavour.
🧄 The Versatility of Garlic
Forms, Processing, and Trade-offs
Garlic is used in many different forms in food, pharmaceuticals, and supplements, each with its own flavour, intensity, shelf-life, and cost (1,2).
- Raw Garlic: The Benchmark
This will be the ultimate garlicky taste and flavour that you can get. Handling and storage costs are high due to its bulk (high water content). - Processed Forms (Food Industry & Supplements)
As a home cook you may also rely on these forms, but they are more related to the food industry because of their stability and ease of use.- Dehydrated garlic: With drying, there is a significant flavour intensity loss.
- Garlic Oil: Highly potent and concentrated brownish liquid that is produced by steam distillation. It is not used directly, but rather a small amount of it is diluted and added to the final product, including baked goods, beverages, and condiments.
- Garlic Juice
- Garlic Paste: Formulated using suitable flavors within a viscous, edible base.
- Garlic Capsules and Tablets: Prepared for the supplement market, capitalizing on garlic’s high medicinal values.
- Specialty and Compound Products
- Garlic Salt
- Black garlic — a specialized form of aged garlic
- Fermented or pickled garlic
Culinary Usage of Garlic
Garlic is probably one of the most used plants for cooking, maybe in second place after onions. It is used in all global cuisines because of it’s pungency, spiciness, and sweet flavour. Garlic is used in many different forms such as raw, sautéed, roasted, powdered, or as oil. It adds a specific flavour to virtually all culinary traditions, some of which include Mediterranean, Middle Eastern, East Asian, Indian subcontinent, American, and Latin American cuisines.
Garlic is very well combined with various herbs such as parsley, rosemary, thyme, or basil, and is a key ingredient in sauces, dressings, soups, stews, and marinades.
Garlic can also be found in pickles and ferments. These are popular in Northern China, the Middle East, Japan, the Mediterranean region, and Europe. Some of these dishes include Laba Suan (China), Torshi Seer (Iran), Aomori pickled garlic (Japan, Aomori prefecture), or lacto-fermented garlic.
Dehydrated powdered or granulated forms are generally used as condiments or in the food industries. These forms of garlic are as used as fresh garlic.
Green garlic, also known as baby garlic or spring garlic, is the immature garlic that can be harvested very early in the spring season. It can be used in salads, stir-fries, or soups.
Finally, the immature flower stalks (scapes) of the hardneck garlic are sometimes used stir-fried, grilled, or sautéed.
Key uses include:
- Raw: In dressings, salsas, dips, and salad dressings.
- Sautéed: Adds aromatic flavor to meats, vegetables, grains, tomato dishes, and sauces.
- Roasted: Produces a milder, sweet, caramelized flavor.
- Pickled or fermented: Found in some Asian cuisines, adds tangy depth.
- Confit: Garlic cloves bathed in oil and slow-cooked for prolonged periods of time.
Example Dishes Featuring Garlic:
- Garlic butter / compound butter — garlic mixed with butter, herbs, and lemon, used for meats, seafood, or bread.
- Aglio e olio (Italy) — pasta with garlic, olive oil, chili flakes, and parsley.
- Toum (Lebanon / Middle East) — garlic sauce emulsified with oil and lemon juice.
- Garlic bread or naan (Europe or India) — bread or flatbread brushed with garlic butter.
- Sofrito / recaito (Latin America) — aromatic sauce made with garlic, onions, peppers, tomatoes, and herbs.
- Pesto — in combination with basil, pine nuts, cheese, and olive oil.
- Sauces such as allioli (garlic and olive oil), aïoli (garlic and olive oil, egg yolks, lemon juice), skordalia, persillade, and gremolata.
Buying Garlic 🧄
- Look for bulbs that are intact, firm, and dry. They should have unbroken skins.
- Don’t buy garlic with soft spots or mold.
- Hardneck has larger cloves and stronger flavor.
- Softneck shelf-life is longer.
Storing Garlic 🫙
- Keep in a cool, dry, dark, and ventilated place. Ideal location will be your pantry.
- Intact whole bulbs can last for several months.
- Avoid refrigeration.
- Garlic can be frozen, dried, or powdered, but fresh cloves retain the most potent flavor and bioactivity
Science of Garlic
Garlic and other species from the Allium family are notorious for the presence of sulfur compounds in their cells which give them their unique smell and taste. One of those is a water-soluble substances is called Alliin, which is colorless and odorless. It is located in the cytoplasm. Another substance, an enzyme located in the vacuoles of the garlic cell, is called Alliinase. Hence, the Alliin and the enzyme do not interact with each other in a normal living cell. When fresh tissue is damaged, those two substances meet each other, creating very short-lived compounds: Allylsulfenic acid, Ammonia, and Pyruvate. Allylsulfenic acid is later transformed into the final form, Allicin. If we want to blame one molecule for the flavour, it will be the enzyme.
The reactions are very rapid and are 97% complete within 30s at 23 °C. Furthermore, the amount of Allicin that a single clove (10 g) can produce is around 5 mg. Allicin half-life (time for 50% decomposition) at room temperature is about 2.5 days (1-7).
Alliinases are enzymes with a defence mechanism against herbivores (animals eating plants). It is normally stored in a distinct compartment within the cell, and upon damage (animal feeding on it) it will be released and will catalyse the production of those pungent molecules. This will generally have a deterrent effect on animals; for example, many species such as European starlings, ticks, mosquitoes, and nematodes are repelled by garlic (1-7).
What about cooking?
Here I have only outlined the reaction that one can observe in a laboratory setting. But we use garlic for cooking! When we consider and talk about allicin’s biological properties, we imply that it is raw and not cooked. Unfortunately, when you heat garlic, the allicin is quickly destroyed. Heating it will cause spontaneous decomposition to allylsulfenic acid (2-propenesulfenic acid) and 2-propenethial (thioacrolein), which will produce alkyl disulfides, polysulfanes, vinyl dithiins, and ajoene (1-7).
Garlic breath
When you ingest raw garlic, it will find itself in the stomach where the pH is low (acidic conditions), which will convert the allicin into 2-propenethiol (PT), which is metabolized to allyl methyl sulfide (AMS). Both those substances account for the stinky breath (halitosis) that you have after eating garlic. Furthermore, the reason for the persistent effects of garlic smell can be explained by the fact that PT and AMS cannot be broken down as quickly in the liver and intestine, and these are further eliminated through breathing (lungs), skin, and urine. That’s why even brushing and mouth washing will not fix the “problem.” (1-7)
Nutritional Values, Biological Properties, and Toxicity
- Nutritional Values:
Garlic is a rich source of proteins, carbohydrates, phosphorus, and vit. C.
The nutritional values for fresh peeled garlic are as follows:
Approximate composition (100 g) of garlic salt:
| Component | Amount | Component | Amount |
| Energy | 63 kcal | K (Potassium) | 212 mg |
| Water | 1.4 g | Na (Sodium) | 31.4 g |
| Protein | 3.2 g | Ca (Calcium) | 220 mg |
| Fat | 0.1 g | Fe (Iron) | 1 mg |
| Carbohydrate | 13.8 g | Mg (Magnesium) | 11 mg |
| Fibre | 0.4 g | P (Phosphorus) | 79 mg |
| Ash | 81.5 g | Zn (Zinc) | 1 mg |
| Vitamins | — |
2. Biological activities
- Many studies suggest that garlic has the following biological activities with significant medical importance:
- Cholesterol reduction
- Garlic significantly lowers blood pressure
- Reduces the risk of colorectal and stomach cancers
- Antioxidant, helpful in the prevention of cancer and cardiovascular disease
3. ⚠️Safety Note
Toxicity to humans and other animals.
Low, acute, or fatal garlic poisoning in humans is very, very rare. It is probably not due to eating it raw or cooked, but rather taking it as supplementation. Note that some of the compounds found in garlic can cause dermatitis and occupational allergy. Even though your pet will never eat garlic, it should be known that garlic is toxic to animals, including cats and dogs (dose that will cause clinical signs of poisoning symptoms: 5 g/kg of raw and 15–30 g/kg of raw garlic in dogs) (1,2).
References
1. Peter, K. V. (ed.) (2001) Handbook of herbs and spices. Woodhead Publishing Limited / CRC Press.
ISBN: 1-85573-562-8; 0-8493-1217-5.
2. Block, E. (2015). Garlic and other alliums: The lore and the science. Royal Society of Chemistry (RSC Publishing).
ISBN 978-0-85404-190-9.
3. Borlinghaus, J., et al. “Allicin: Chemistry and Biological Properties.” Molecules, vol. 19, no. 8, 2014, pp. 12591–12618. DOI:10.3390/molecules190812591.
4. Lawson, L. D., and Z. Wang. “Allicin Bioavailability and Bioequivalence from Garlic Products.” Molecular Nutrition & Food Research, vol. 62, no. 15, 2018.
5. Fujisawa, H., “Thermostability of Allicin Determined by Chemical and Biological Assays.” Bioscience, Biotechnology, and Biochemistry, 2008.
6. Seki, T., et al. “Functionality of garlic sulfur compounds (Review).” Biomedical Reports, 2025.
7. Chen, Z., et al. “Thermolysis kinetics and thermal degradation compounds of allicin.” Food Chemistry, 2017.