Rock sugar, or Koori Zato (氷砂糖), refers to semi-translucent gemstone-like chunks of sugar. We use them to make Plum Wine and Ume Plum Syrup.

Rock Sugar (Koori Zato) | Easy Japanese Recipes at JustOneCookbook.com

Rock sugar, or Koori Zato (氷砂糖), or sugar candy or rock candy, is made from a solution of sugar and water through crystallization. You can use it in sweet and savory dishes and beverages.

What Is Rock Sugar

Rock sugar is made by cooling sugar syrup from sugarcane or beets into large crystals. It comes in various types, such as white granulated sugar, brown sugar, and sugar cane, and is sold in jagged rocks or rectangular cubes.

It is commonly used in Asian cuisines to sweeten teas, drinks, dessert soups, and liquors or in cooking, such as marinades or braised pork belly. It’s less sweet than table sugar, but no scientific evidence suggests it’s a healthier alternative.

What Does It Taste Like

It has a clear and nuanced sweet flavor with hints of caramel.

Rock Sugar (Koori Zato) | Easy Japanese Recipes at JustOneCookbook.com

How To Use

The Japanese use it to make Plum Wine (Umeshu) and Ume Plum Syrup. As the rock sugar crystals take time to dissolve, this helps extract the flavors and fragrances from the plums slowly.

Depending on the recipe, you can also use it like white sugar or honey, such as sweetening hot tea and lemonade, and in cooking.

Where To Buy

Find it at Japanese or Asian grocery stores or specialized spice and tea stores. Alternatively, you can find it on Amazon and other online retail sites.

If you’re using a Chinese brand, choose the opaque or white-colored types, not the gold-colored rock sugar made from sugar cane, which will color the liquid.

How To Store

Keep bags in a cool and dry place.

Japanese plum wine (umeshu) in a glass jar.
Plum Wine (Umeshu)
Tall glasses containing ume syrup cider and ume compote.
Ume Plum Syrup

Substitutions

You could use regular or pure cane sugar, but the crystals will melt faster. The undissolved sugar may sink to the bottom of the jar instead of melding with the fruits. Shake the container a few times or turn it upside down to mix.


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