The Science Behind Black Garlic’s Sweetness

This is an excellent question. The unique sweetness of black garlic is its most fascinating characteristic, and behind it lies a fascinating biochemical process driven by enzymes and heat.

In simple terms, the sweetness of black garlic primarily comes from the breakdown and transformation of the garlic’s own starches and sugars into new, sweeter sugars during the fermentation process, while the pungent compounds are simultaneously broken down.

Core Processes: Maillard Reaction and Enzymatic Reactions

The production of black garlic is not traditional “fermentation” involving microorganisms (like yogurt or kimchi), but rather a “ripening” or “aging” process dominated by enzymatic browning and the Maillard Reaction. This process typically takes place in a high-temperature, high-humidity environment (e.g., 60-80°C, 70-90% humidity) for several weeks.

Which Substances are at Work?

1. The “Release” and Transformation of Sugars (The Direct Source of Sweetness)

This is the most critical step in sweetness production.

• Main Actor: The garlic’s own carbohydrates.
  • Raw garlic is rich in polysaccharides, primarily fructans. Fructans are long chains of fructose molecules and are not very sweet themselves.
• The Worker: Enzymes.
  • In the heated and humid environment, the garlic’s endogenous enzymes (especially fructanase) are activated.
  • These enzymes act like “scissors,” cutting the long, non-sweet fructan chains into short-chain, highly sweet simple or double sugars, mainly:
    • Fructose: About 1.7 times sweeter than sucrose, it is the main contributor to black garlic’s sweetness.
    • Glucose: Has a sweetness level similar to sucrose.
• Result:
  • After several weeks of continuous action, the content of reducing sugars (like fructose and glucose) in garlic increases significantly (studies show it can increase several-fold or even tenfold), while the content of long-chain polysaccharides decreases correspondingly. It’s like breaking down a bundle of non-sweet “wood” (fructans) into very sweet “candy pieces” (fructose).

2. The Maillard Reaction (The Source of Flavor and Color)

This reaction occurs simultaneously with sugar conversion. While it doesn’t directly produce sweetness, it is crucial for the final flavor profile.

• Process: The reaction occurs between amino acids (the building blocks of proteins) and reducing sugars (the fructose and glucose produced in the previous step).
• Effects:
  • Creates Color: Gives black garlic its characteristic dark brown or black color.
  • Creates Flavor: Generates a variety of complex flavor compounds, including caramel, toffee, molasses, and slight sour notes. These complex flavors interact with the direct sweetness, making the sweetness of black garlic mellow, soft, and layered, rather than singular and sharp like white sugar.

3. Breakdown of Pungent Compounds (Removing the “Spiciness,” Highlighting the “Sweetness”)

The pungency and spiciness of raw garlic come mainly from alliin and the enzyme alliinase, which react to form allicin.

• Process: During the high-temperature aging process, alliinase is deactivated and can no longer catalyze the formation of pungent allicin.
• Result:
  • The existing pungent sulfur compounds (like allicin) gradually break down and convert into new, milder sulfur compounds, such as S-allyl-cysteine, which is not only non-pungent but is also considered to have various health benefits.
  • When the pungency and spiciness are greatly reduced or eliminated, the inherent sweetness and umami that were once masked can fully emerge.

Summary

The process that makes black garlic sweet is a multi-step synergistic effect:

1. Action of Enzymes: Fructanase and others break down non-sweet long-chain fructans into highly sweet simple sugars—fructose and glucose. This is the material basis for the sweetness.
2. Maillard Reaction: The newly formed reducing sugars react with amino acids, producing rich caramel and molasses flavors and a black appearance, making the sweetness rich and complex.
3. Breakdown of Pungency: High temperature deactivates alliinase and breaks down the pungent allicin, clearing the obstacle to perceiving sweetness.

Therefore, when you taste black garlic, you experience a pure and rich sweetness brought by fructose and glucose, modified by the Maillard Reaction, and uninterrupted by any pungent spiciness.