How to Grow Mung Bean Sprouts in Australia

Mung bean (Vigna radiata) is a legume in the pea family, Fabaceae. Its dried beans are sprouted in a jar and picked short and crisp. The sprouts are sweet and crunchy, and they are ready 3 to 5 days after the soak starts. Many jars fail because water is left sitting in them between rinses.

Three mistakes that matter

1. Leaving water in the jar. Beans sitting in a puddle between rinses ferment, smell sour and spoil. After every rinse, drain hard and prop the jar mouth down at about 45 degrees so the last drops keep running out.
2. Growing them in the light. Light greens the tips and can make the sprouts chewy and bitter rather than sweet. Keep the jar in a dark corner of the kitchen, or a cupboard with room for air around the jar.
3. Letting them grow too long. Past the crisp stage, large sprouts turn soft, lose quality quickly and can go mouldy at room temperature. Pick them at the stage described in Harvesting and Storing.

When to sprout

A jar on the kitchen bench works in any month. Mung beans sprout best near 20 to 22°C and germinate across about 18 to 29°C. A colder room slows them, and above 30°C a jar can sour or turn mouldy before the sprouts are ready.

Food safety

The warm, wet conditions that grow a sprout also let bacteria multiply, and bacteria carried inside a contaminated bean cannot be washed off.

• Buy beans sold for sprouting. Garden seed can be treated with fungicide or insecticide, and which seeds to sprout explains the difference.
• Wash your hands before handling beans or sprouts. Wash the jar, lid, mesh and bowl in hot water and detergent, then rinse them. Before the first batch and between batches, sanitise them in a dishwasher that can sanitise, usually on its longest, hottest setting. Without one, soak them in very hot water (77°C for 30 seconds). Or use plain unscented household bleach at 25 mL to 10 L of cold water for 30 seconds, made up fresh each day. Let them air-dry.
• Soak and rinse only in water fit to drink, and keep the jar away from raw meat and pets.
• Keep the fridge at 5°C or colder, and eat the sprouts within 3 to 4 days of harvest. Sprouts cooked for anyone at higher risk are eaten straight away. Leftovers are cooled, kept in the fridge, used within a day of cooking and reheated until steaming hot.
• Sprouts can carry harmful bacteria while looking, smelling and tasting normal, so none of those is a test of safety.
• Throw out any jar that smells sour or musty, feels slimy or turns dark. More signs are in sprout problems and safety.

What you need

Use a wide-mouth glass jar with a mesh lid, or muslin held on with a rubber band. A bowl or rack holds the jar upside down to drain. Mung beans are large, so a coarser mesh lets loose hulls wash out as the sprouts grow. Add mung beans for sprouting, plus a sprouting jar or mesh lids for mason jars if you need them.

For thicker, shop-style sprouts, spread the soaked beans over the base of a draining container on a rack and cover it to keep out light. Rest a plate on the beans, add a light weight once they are growing, and lift both off for every rinse. Thick, pale, shop-style mung bean sprouts covers that method in full.

Soaking and Rinsing

Start the soak in the evening, and the first rinse falls at breakfast.

1. Measure the beans, rinse them under running water until it runs clear, and pick out any broken or discoloured beans.
2. If you choose, soak the dry beans in undiluted white vinegar for 15 minutes, then rinse them for 1 minute under the tap. This lowers the risk but does not remove it.
3. Cover the beans with two to four times their volume of cool drinking water, about 20°C. Skim off any beans, hulls or grit that float.
4. Soak for 8 to 12 hours, overnight, out of direct sun, until most beans look pale and swollen.
5. Drain, rinse once with fresh water, and drain hard.
6. Shake the beans along the side of the jar and prop it mouth down at an angle in the bowl, somewhere dark.

From then on, rinse two to three times a day with cool drinking water, and three times in hot weather. Never let the beans soak again. Fill the jar, swirl and pour the water out through the mesh. Prop it at an angle again, so water drains out and air comes in.

Day by day

Growing beans give off their own heat, and each cool rinse carries some of it away.

Harvesting and Storing

Mung bean sprouts are ready when most tails are 1 to 5 cm long, still white and firm enough to snap. The green hulls are edible and many cling on, but floating off the loose ones gives a cleaner bowl.

• Tip the sprouts into a large bowl of cold drinking water.
• Swirl them and loosen the clumps gently so loose hulls rise.
• Skim the hulls off the surface or pour them away.
• Lift out the sprouts and pick out any beans that stayed hard.
• Repeat once if many hulls remain.

Dry the sprouts on a clean cloth or in a salad spinner until the surface feels dry. Pack them loosely into a clean, sealed container, refrigerate them straight away and use them within the limit in Food safety. Rinse each serve under cool running water just before eating. Cooked until steaming hot, they suit soups and stir-fries. Eating them raw in salads and sandwiches is a risk each reader weighs, and never for anyone named in Food safety.

Common problems

White fuzz on the tails. Fine root hairs can show as an even white fuzz along the tails only, and they collapse and vanish when rinsed. Mould can be white too. It grows in cobwebby patches on beans and empty hulls, stays after a rinse and smells musty, and that jar goes in the bin.

Sour smell or slime. Any of the signs in Food safety means the jar has spoiled, and rinsing will not save it. Throw it out, wash everything and start again with the drainage in Three mistakes that matter.

Beans that stay hard. Old beans, beans stored warm or damp, an overfilled jar, or a jar kept too wet or too dry are the usual causes. Pick the hard ones out at harvest, and use fresh beans stored cool and dry next time.

A jar that runs warm. A packed jar in a hot kitchen heats up and spoils faster. Move it to the coolest dark spot in the house, and rinse as Soaking and Rinsing describes for hot weather.

Tips

1. Start a small jar every few days for a steady supply, rather than one large batch.
2. Store dry beans sealed in a cool, dark, dry cupboard, where they can keep for several years.
3. To keep a surplus, steam-blanch the sprouts for 3 minutes, cool them in iced water, drain and freeze them in sealed containers.