How to make Ume Koji Syrup 梅麹シロップ

Have you ever wondered if there’s a drink that can refresh your body on a hot summer day, boost your health, and still taste deliciously sweet? Many people turn to lemonade or iced tea, but Japan has a hidden treasure: Ume Koji Syrup (梅麹シロップ). This special syrup blends the tangy flavor of green plums with the natural sweetness of koji and sugar. It’s more than just a drink—it’s a seasonal ritual that connects food, health, and tradition.

In this guide, we’ll explore what makes Ume Koji Syrup unique, how to make it at home step by step, and tips for storing and enjoying it in different ways. By the end, you’ll see why this recipe is considered a beauty drink and a health booster during the summer months.

Table of Contents

Why This Recipe is Special

Ume Koji Syrup (梅麹シロップ) is a Japanese seasonal syrup made from just three ingredients: fresh green plums (ume), rice koji, and sugar. While the ingredient list is short, the fermentation process unlocks deep flavors and beneficial enzymes.

• Time Requirement: This recipe takes patience. It usually needs about 1 to 2 weeks for the sugar to dissolve fully and the syrup to develop.
• Difficulty Level: Beginner-friendly. The steps are simple and require no advanced cooking skills—just care and consistency.
• Special Qualities: Unlike other plum syrups, the addition of rice koji brings probiotics and enzymes that aid digestion and support gut health.

Ume Koji Syrup (梅麹シロップ) @JapanDishes

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Essential Ingredients

To make Ume Koji Syrup, you need only a few components, but each one plays a key role:

1. Green Plums (Ume) – 500g
   • Provide tartness, vitamin C, and minerals.
   • Only available in early summer in Japan, making this recipe a seasonal tradition.
   • Substitution: If fresh ume is not available, frozen ume can be used. Do not use ripe yellow plums as they are too soft.
2. Sugar – 500g (beet sugar recommended)
   • Preserves the syrup and draws out the plum juice.
   • Beet sugar is traditional, but white sugar, rock sugar, or brown sugar can also be used.
   • Variation: Rock sugar makes the syrup clearer and lighter, while brown sugar adds a deeper, caramel-like taste.
3. Dried Rice Koji – 50g
   • A fermented rice product that introduces natural enzymes.
   • It helps break down the plum’s nutrients and enhances the syrup’s health benefits.
   • Alternative: Raw rice koji can also be used if available.

Step-by-Step Instructions

Making Ume Koji Syrup is simple but requires care at every step. Here’s how to do it:

Step 1: Wash the Plums

Rinse the green plums gently under cool running water. This removes dirt and surface impurities.

Tip: Be gentle, as plums bruise easily. A bruised plum can affect the final flavor of your syrup.

Step 2: Soak (Optional but Recommended)

If you are concerned about bitterness or scum, soak the plums in water for about 3 hours. This step softens harsh flavors and improves clarity.

Step 3: Dry and Remove Stems

Wipe off the water completely with a clean towel. Then, using a bamboo skewer, carefully remove the small stems from each plum.

Why this matters: Removing stems prevents bitterness and avoids unwanted fermentation flavors.

Step 4: Layer the Ingredients

In a clean glass jar, begin layering:

• First, add a layer of sugar.
• Next, add a layer of plums.
• Then, add another layer of sugar.
• Repeat until all plums and sugar are used.

Step 5: Add the Koji

Finally, sprinkle the dried rice koji on top of the last sugar layer. Cover with more sugar to ensure the koji is fully buried.

Step 6: Cover and Secure

Cover the jar with a breathable cloth (such as a dish towel or paper towel) and secure it with a rubber band. This prevents dust and insects from entering while allowing natural gases to escape.

Step 7: Stir Daily

Once a day, stir from the bottom with a clean spoon to help the sugar dissolve evenly. Within a few days, you’ll notice syrup forming as the sugar pulls liquid out of the plums.

Secrets to Success and Expert Tips

• Use Sterilized Jars: Make sure your jar is thoroughly cleaned and dried before starting. This prevents mold growth.
• Don’t Skip Stirring: Daily stirring is essential to avoid sugar settling at the bottom and to keep fermentation even.
• Check the Smell: A fresh, fruity aroma means it’s fermenting properly. If you notice a sour or moldy smell, discard it.
• Patience is Key: Resist the urge to taste too early. Let the syrup fully extract and ferment for at least 7 days.

Assembly: How to Enjoy Ume Koji Syrup

Once the syrup is ready, strain the liquid and transfer it to a clean bottle. Now you have a versatile syrup that can be used in many ways:

• Mix 1–2 tablespoons of syrup with cold water or soda water for a refreshing summer drink.
• Drizzle over shaved ice for a cooling dessert.
• Use as a glaze for meat or fish dishes to add a sweet-tart flavor.
• Stir into yogurt for a probiotic boost.

Ume Koji Syrup (梅麹シロップ) @JapanDishes

Storage and Make-Ahead Tips

• Refrigeration: Store the finished syrup in the refrigerator in a sealed glass bottle. It will keep for about 3–4 weeks.
• Freezing: Freeze small portions in ice cube trays for long-term storage.
• Make-Ahead: You can prepare the syrup in early summer and enjoy it throughout the hot season.

Recipe Variations

Here are a few creative twists you might like:

• Honey Ume Koji Syrup: Replace part of the sugar with honey to add floral richness.
• Brown Sugar Version: Use brown or unrefined sugar to deepen the flavor.
• Ginger Infusion: Add thin slices of fresh ginger during fermentation for a spicy kick.
• Sparkling Cocktail: Mix syrup with soda water and a splash of sake or sparkling wine.
• Herbal Blend: Add mint leaves or basil to the mixed drink for extra aroma.

If you enjoy Japanese summer drinks, you may also like to try Aka Shiso Juice (Red Perilla), another refreshing seasonal beverage made with vibrant red perilla leaves. It pairs beautifully with Ume Koji Syrup as part of your summer drink menu.

Conclusion

Ume Koji Syrup (梅麹シロップ) is more than just a seasonal Japanese recipe—it’s a refreshing tradition that brings together health, taste, and culture. By combining simple ingredients with a little patience, you create a syrup that can be enjoyed in drinks, desserts, or even savory dishes.

Whether you’re new to Japanese fermentation or simply want a healthy summer treat, this recipe is an easy entry point. So, gather your plums, sugar, and koji, and start your own batch of Ume Koji Syrup today.

Also, if you love Japan, its food, and want travel tips or things to see, check out this article on Best Things to Do and See in Tokyo in October. It gives ideas for festivals, food adventures, and cultural highlights for people who like to read and discover what’s new in Japan.

Enjoy your homemade syrup and perhaps one day, sip it while watching cherry blossoms or autumn leaves in Japan!

FAQs About Ume Koji Syrup (梅麹シロップ)

Q1: How long does it take for Ume Koji Syrup to be ready?
It usually takes about 7–14 days for the sugar to dissolve fully and for the flavors to balance.

Q2: Can I use yellow ripe plums instead of green plums?
No. Only unripe green plums should be used for this syrup. Ripe plums are too soft and may spoil during fermentation.

Q3: What are the health benefits of Ume Koji Syrup?
It provides vitamin C, minerals, probiotics, and enzymes that support digestion, improve energy, and promote healthy skin.

Q4: Can I reduce the sugar?
Sugar is essential for preservation, but you can replace part of it with honey or rock sugar. Avoid cutting it too much, or the syrup may spoil.

Q5: How should I store the leftover plums after straining?
They can be refrigerated and used in jams, desserts, or as a sweet-tart topping for yogurt and ice cream.

Q6: Is this recipe suitable for beginners?
Yes! The steps are easy, and with daily stirring and clean tools, anyone can make it.