A Week of Kitchen Mishaps: What Fermentation Taught Us

Quick answer: Tempeh fermentation depends on temperature, moisture, airflow and time, and small changes can slow a batch or stop the beans binding. At Calon, a batch that looks, smells or behaves differently is investigated, and if there’s any doubt about safety, it’s thrown away.

There are some days in a small food business when everything seems to work.

The beans soak beautifully.

They cook just as they should.

The temperature behaves itself.

You check the tempeh a few hours later and there it is: a lovely white layer of mycelium slowly bringing the beans together.

For a moment, you think, I think we've got this.

And then there are the other days.

The days when you open a container and stare at it for a little longer than usual.

Is that normal?

Why is this one taking so long?

Did we do something differently this time?

We've had plenty of those moments at Calon.

One batch took longer than expected. Another seemed drier than we wanted. Some beans stubbornly refused to become the beautiful, firm block we were hoping for.

Nothing dramatic. No kitchen disaster worthy of a television programme.

Just small things that made us stop, look again, check our notes and ask questions.

And honestly, those batches taught us some of the most important lessons we've learned so far.

Because this is the part of making tempeh that you don't always see.

The washing up.

The checking.

The waiting.

The second guessing.

The batch that doesn't quite behave.

And the decision that sometimes has to be made after you've put time, ingredients and care into something:

This one isn't good enough.

That isn't always an easy decision when you're a small business.

But it is part of learning to make something properly.

*A note: this is what we do in our own kitchen. If you ferment at home, follow guidance from a reliable food safety source rather than copying us.

So, what is actually happening inside that little block?

If you've read our earlier story about tempeh, you'll know that it isn't simply cooked soyabeans pressed into a block.

Tempeh is fermented.

We begin with cooked soyabeans and introduce a tempeh starter containing a species of mould from the Rhizopus family. Under the right conditions, the mould grows through the beans as fine white threads called mycelium.

Those threads gradually bind the beans together.

And that is how you end up with tempeh.

It sounds wonderfully simple.

But there is a catch.

Fermentation is alive.

You can prepare everything carefully, but the process still depends on what is happening around those tiny organisms.

Temperature matters.

Moisture matters.

Airflow matters.

The condition of the beans matters.

Time matters.

Even small changes can affect how a batch develops.

That is one of the things we find fascinating about making tempeh.

It isn't quite like following a cake recipe where you put everything in the oven, set a timer and wait for the bell.

With fermentation, you have to pay attention.

You have to look.

You have to learn.

And sometimes, you have to wait.

The batch that wouldn't hurry up

One of our batches simply took longer than expected.

We had soaked the beans.

Cooked them.

Prepared them.

Added the starter.

Everything seemed fine.

But the white mycelium wasn't spreading as quickly as we had expected.

So we waited.

Then we checked again.

And waited a little more.

This is where you learn something very quickly about fermentation.

The clock doesn't make the tempeh ready. The conditions do.

Tempeh is commonly fermented for somewhere around 24 to 48 hours, depending on the method and conditions. Temperature is particularly important because Rhizopus grows within a particular range, and even a small change can affect the speed of fermentation.

So instead of immediately assuming something had gone wrong, we went back to the basics.

What was the temperature?

What was the condition of the beans?

Was there enough moisture?

Was there enough airflow?

Had anything changed from our previous batches?

It is tempting, especially when you're new to something, to think that every batch should behave exactly like the one before it.

The lesson: the clock doesn’t make the tempeh ready. The conditions do. When you’re new to something it’s tempting to expect every batch to behave like the last one. Fermentation doesn’t work that way, and sometimes the right move is not to interfere but to watch.

The dry batch

Then there was the dry batch

Another batch taught us a different lesson.

The mould was growing, but the beans weren't coming together in the way we wanted.

Instead of a firm cake, some of the beans remained loose and separate.

We went back through the process again.

One thing became very clear.

Moisture matters. A lot.

Tempeh needs moisture for the mould to grow, but too much moisture can create its own problems. The beans need to be moist enough to support fermentation without becoming excessively wet.

This is one reason traditional tempeh making and modern tempeh production pay so much attention to airflow and moisture.

The mould needs to breathe.

Traditional tempeh is often wrapped in banana leaves, while modern production may use perforated packaging. The idea is similar: create an environment where the developing tempeh has the moisture and airflow it needs.

It sounds like a small detail.

It isn't.

Sometimes something as simple as how dry the beans are before fermentation can make a surprising difference to the finished tempeh.

That batch reminded us that there is no such thing as a tiny detail when you're working with fermentation.

And then there was the smell

This one made us pause.

If you've spent enough time around tempeh, you begin to recognise its smell.

Good tempeh can have a clean, earthy, slightly mushroom like aroma. Once cooked, it develops that lovely nutty, savoury character we enjoy so much.

But one batch smelled different.

Not dramatically wrong.

Just different enough to make us stop.

And this is where the romantic idea of fermentation has to meet something much more important:

food safety.

When you're making a fermented food, you can't simply rely on your eyes and nose and hope everything is fine.

Appearance and smell are useful observations, but they aren't a substitute for proper food safety controls.

Temperature needs to be controlled.

Hygiene needs to be taken seriously.

Time needs to be recorded.

The process needs to be understood and monitored.

And when something doesn't meet the standard, you don't try to convince yourself that it's probably alright.

You stop.

You investigate.

And if necessary, you discard it.

That's not wastefulness.

That's responsibility.

Especially when you're making food that someone else is going to take home and share with their family.

What does good tempeh actually look like?

This is something we've learned to appreciate through repetition.

A good tempeh cake should feel firm and hold together when you slice it.

You should be able to see the white mycelium binding the beans together.

The aroma should be clean and earthy, often with a gentle mushroom like note.

And once cooked, the beans develop a lovely savoury, nutty flavour.

 

 

As tempeh matures, you may also see darker or grey areas caused by the mould producing spores. That can be a normal part of tempeh's development.

But not every unusual colour or smell should simply be accepted as part of fermentation.

Strong ammonia like smells, unpleasant sour or decaying aromas, or unusual coloured growth are reasons to stop and investigate rather than carry on regardless.

This is one of the less glamorous things we've learned.

Knowing when something is good is important.

Knowing when something isn't good enough is even more important.

The questions we ask after a difficult batch

Every batch that didn't quite go to plan left us with questions.

Was the temperature stable?

Were the beans prepared consistently?

Did they have the right amount of moisture?

Was there enough airflow?

Did we allow enough time?

Had anything changed from the previous batch?

And perhaps the most useful question of all:

 

Did we write everything down?

Because memory is surprisingly unreliable when you're making batch after batch.

You think you'll remember.

That batch was slightly warmer.

We soaked those beans a little longer.

The kitchen was colder that day.

But a few weeks later, the details begin to blur.

So we record.

We check.

We learn.

Then we make another batch.

And another.

That is how a small food business slowly becomes better at what it does.

Not through one perfect attempt.

Through many attempts, careful observation and a willingness to learn from every one.

There is something humbling about fermentation

Perhaps this is the part we didn't expect when we first started making tempeh.

You can't bully fermentation into happening faster.

You can't simply tell the mould what you want it to do.

You can create the right environment.

You can prepare carefully.

You can monitor what is happening.

But then you have to give it time.

There is something quite grounding about that.

Especially when you're trying to build a business.

There are websites to launch.

Labels to check.

Packaging to organise.

Markets to prepare for.

Emails to answer.

Plans to make.

And then, somewhere in the middle of all of that, there is a little container of soyabeans quietly fermenting on its own schedule.

It doesn't care about your to do list.

It doesn't care that you have an order waiting.

It simply carries on doing what fermentation does.

Perhaps that is part of why we have come to enjoy the process so much.

It makes you slow down.

Look properly.

And pay attention.

What those imperfect batches taught us about Calon

When you see a finished packet of food, you don't see all of this.

You don't see the batch that took too long.

You don't see the beans that didn't bind properly.

You don't see the extra cleaning.

You don't see the notes we made.

You don't see the conversations about whether something was good enough.

And you probably shouldn't.

A food product should arrive in your hands feeling simple.

But behind that simplicity is a lot of care.

For us, every batch has gradually helped answer one question:

Would we be happy giving this to someone trying Calon for the very first time?

Because that first experience matters.

Imagine you've never eaten tempeh before.

You pick up a little block made here in Wales.

You take it home.

You slice it.

You put it in a hot pan.

You take your first bite.

We want that experience to make sense.

Not because we've convinced you that you should like tempeh.

Not because we've told you that it is the next big thing.

Simply because you've discovered something you genuinely enjoy.

 

Learning food safety with the right people around us

One of the most reassuring parts of this journey has been knowing that we haven't had to figure everything out alone.

We are incredibly grateful for the continued support and guidance we've received from Hadi Brooks and Tim Ellis, Business Wales, whose advice and encouragement have helped us navigate the many new things that come with building a food business from scratch.

We are also very grateful to the ZERO2FIVE Food Industry Centre at Cardiff Metropolitan University. Their team has shared so much knowledge with us through their guidance, practical support and food safety seminars. Those sessions have helped us understand not just what we need to do, but why it matters.

When you're learning to make a fermented food, food safety isn't something you can treat as an afterthought. It has to become part of the way you think.

And we would also like to thank Cywain for their support and guidance as we've continued developing Calon and finding our way through the many challenges that come with turning a small food idea into a real Welsh food business.

Food safety can’t be an afterthought when you make a fermented food. It has to become part of how you think. Each of these conversations, workshops, seminars and pieces of advice has given us something valuable to take back into our kitchen.

We're still learning, but we're learning with the right people around us, asking questions, listening carefully and continually trying to do things better.

For a small business like Calon, that support means a great deal.

And perhaps that's another lesson this journey has taught us:

You don't have to know everything when you start. You just need to be willing to learn, ask for help and take the responsibility seriously.

We're still learning

That's probably the most honest thing we can say about Calon.

We're still learning.

We're still asking questions.

We're still making adjustments.

We're still discovering what happens when a traditional food meets a small kitchen in Wales.

And that's okay.

In fact, we think that's part of the beauty of starting something from scratch.

You don't begin with all the answers.

You begin with curiosity.

Then you make something.

You see what happens.

You learn.

You try again.

And somewhere along the way, you realise that the thing that looked like a small experiment in your kitchen has slowly become something much bigger.

A brand.

A product.

A community.

And perhaps, eventually, a little piece of someone's own kitchen story.

So if you've never tried tempeh before, you don't need to know everything about it.

You don't need to be an expert.

You don't even need to know whether you're going to like it.

Just come and discover it with us.

We'll keep learning on this side of the kitchen.

You can bring the curiosity.

And maybe, one day, you'll take a bite and think:

Oh.

That's actually really good.

From our kitchen in Wales, we're only just beginning.

Calon.

Protein with a place.