Natto Spores Starter Instructions

Gather first

What you need

Clean equipment, careful sanitation, and a steady 100°F fermentation temperature give the Natto Spores Starter the best beginning.

Natto Spores Starter pouch with dried soybeans, stainless-steel pot and spoon, casserole dish, and aluminum foil

Ingredients

2 cups dried soybeans
1 packet Natto Spores Starter

Equipment

Non-reactive pot, such as stainless steel or enamel
Colander
Large stainless-steel spoon
Casserole dish
Aluminum foil and a clean pin
Oven, dehydrator, or warmer able to hold 100°F

SANITATION IS ESSENTIALRinse or dunk the colander, cooking spoon, and casserole dish with boiling water before they touch the cooked beans.

EXPECT A STRONG AROMANatto is quite odorous while fermenting. You may want to isolate it during the 22-24 hour fermentation period.

Part 1

Prepare the soybeans

Begin the day before you plan to ferment. The beans should finish tender enough to culture while still holding their shape.

STARTING WITH PRE-COOKED BEANS?Dry beans are preferred. If you are not using dry beans and your beans are already fully cooked, skip the soaking and boiling directions. Complete the sterilization and warmer setup, then continue to Part 2: Add the Natto Spores.

Soak and cook

Done

STEP 19-12 hours

Wash and soak

Dried soybeans being covered with filtered water in a stainless-steel pot before soaking for 9 to 12 hours

Wash 2 cups of dried soybeans. Cover with 6 cups of filtered water and soak for 9-12 hours. A longer soak is recommended during colder months.

Plan ahead: start in the evening so the beans are ready to cook the next day.

Suggested reminder: 9 or 12 hours.

Choose when you want to continue, then select calendar, email, or text.

Done

STEP 22-3 hours

Boil until tender

Soaked soybeans gently boiling in fresh water with a 30-minute check timer

Drain off the soaking water. Place the beans in a large pot, cover with fresh water, and boil for 2-3 hours. Check every 30 minutes. The beans should be tender, but not mushy.

Target texture: moist and tender enough to ferment, while still firm enough to hold their shape.

Suggested reminders: 30 minutes, 2 hours, or 3 hours.

Choose a checkpoint, then select calendar, email, or text.

Done

STEP 3

Sterilize the equipment

Boiling water sterilizing a stainless-steel colander, cooking spoon, and white casserole dish

Rinse or dunk the colander, cooking spoon, and casserole dish with boiling water to sterilize them. Set the sterilized pieces on a clean surface.

Protect the culture: clean tools help ensure the right organisms thrive in the beans.

Done

STEP 4Preheat to 100°F

Drain and prepare the warmer

Cooked soybeans draining into a sterilized casserole dish beside a preheated 100 degree Fahrenheit oven

Drain the cooked beans in the sterilized colander and place them in the sterilized casserole dish. Turn on the oven light so the incubation space preheats to 100°F.

Temperature matters: the fermentation environment must remain at a steady 100°F.

Part 2

Add the Natto Spores

Work with the beans while they are still hot and use only the sterilized tools.

Inoculate and cover

Done

STEP 5

Add the starter

One silver Natto Spores Starter packet being poured directly over hot soybeans in a sterilized casserole dish

While the beans are still hot, pour 1 packet of Natto Spores Starter over the beans. Stir the beans carefully using the sterilized stainless-steel spoon.

Mix gently and thoroughly: distribute the starter throughout the beans without crushing them.

Done

STEP 61-inch layer

Spread the beans

Inoculated soybeans spread evenly in a one-inch layer in a sterilized casserole dish

Spread the beans in a layer about 1 inch thick in the casserole dish. If any beans spill onto the counter or another unsterilized surface, discard them. Do not add spilled beans back to the batch.

Avoid contamination: only beans that stayed in the sterilized work area belong in the dish.

Done

STEP 7Holes 1 inch apart

Cover and vent

Casserole dish tightly covered with aluminum foil while small ventilation holes are made one inch apart

Cover the casserole dish tightly with aluminum foil. Use a clean pin to poke small holes in the foil, spacing the holes 1 inch apart.

Why the holes? The culture needs limited oxygen while the foil keeps the beans protected and dark.

Part 3

Culture and finish

Keep the covered dish at a steady 100°F, then cool and refrigerate the finished natto to develop its best flavor and stringiness.

Done

STEP 822-24 hours at 100°F

Ferment the natto

Foil-covered casserole dish fermenting in a warm oven at 100 degrees Fahrenheit for 22 to 24 hours

Place the covered casserole dish in the oven, dehydrator, or other warmer. Ferment for 22-24 hours, keeping the temperature at a steady 100°F.

Look and smell: the natto is finished when a whitish film appears and the beans have a strong ammonia-like aroma. Remove the dish from the warmer when these signs appear.

Suggested reminder: check at 22 hours or 24 hours.

Choose a checkpoint, then select calendar, email, or text.

Done

STEP 9Cool 2 hours, then chill overnight

Cool, cover, and refrigerate

Finished stringy natto cooling for two hours before transfer to covered glass containers and overnight refrigeration

Let the finished natto cool at room temperature for 2 hours. Remove the aluminum foil, transfer the natto to covered containers, and refrigerate for at least overnight for the best flavor and stringiness.

Suggested reminder: cool for 2 hours.

Suggested reminder: refrigerate for at least 12 hours.

Store the finished natto

Keep finished natto in covered containers. Freeze smaller portions if you want to thaw them later.

About 1 weekin the refrigerator

Freeze portionsand thaw as needed

Troubleshooting

Is this normal?

Use these appearance, aroma, and handling cues while your natto cultures.

The natto smells strong while fermenting

A strong odor is expected. Natto can be quite odorous during fermentation, so you may prefer to isolate the warmer during this stage.

I see a whitish film on the beans

This is one of the key signs of finished natto. When the whitish film appears together with a strong ammonia-like aroma after the fermentation period, remove the dish from the warmer.

Some beans spilled onto the counter

Discard every spilled bean. Do not return beans from an unsterilized surface to the casserole dish because they can contaminate the batch.

The beans are mushy after boiling

The target is tender but not mushy. Check future batches every 30 minutes during boiling so the beans retain a firm final texture.

How do I know the natto is ready to eat?

After fermentation, cool for 2 hours and refrigerate in covered containers at least overnight. This resting period develops the best flavor and characteristic stringiness.

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