Maltose Syrup from Scratch

A quintessential syrup for old school Chinese sweets (and some very off-topic chat on sugars)

Hi friends! This week’s post is slightly different — no cooking recipes here, instead, I will show you how to ferment your very own maltose syrup at home.

The process is not very complicated in terms of steps, but the science behind it is super cool, and I am also sharing some interesting notes on sugars that I have learnt during the process.

Why did I suddenly decide to make a syrup? Well, a couple weeks back I wanted to make some traditional sweets for CNY. While reading up various recipes, ‘Maltose Syrup’ (Mai Ya Tang 麦芽糖) kept appearing.

It brought feelings of nostalgia; my grandparents always had a jar in the kitchen. The syrup is incredibly viscous, but softens as it gets warm. I remember swirling bulbs of it out with a chopstick in summer afternoons, golden threads unravelling out of the jar as I lift my hand higher. Then I’d wrap it around the tip of the chopstick, and enjoy my very own ‘freshly-made’ lollipop.

Literally my fav childhood sweet (because it’s not v sweet)

Since moving to the UK, I have not seen it anywhere in Asian supermarkets. Nor have I seen it mentioned in any Western dessert recipes I have read.

Can I just make some from scratch? I thought.

Of course, given the power of Amazon, I could easily have ordered some online. But where would be the fun in that? And how else am I going to spend my time given it’s still lockdown? So I ordered wheat grains and sticky rice instead.

---

BUT FIRST, I had some other questions. What exactly is Maltose Syrup? What makes it different?

TL;DR — it provides extra viscosity/stickiness whilst lower sweetness compared to most other types of sugars/syrups. You can use it for glaze in sweet and savoury dishes alike (think char-siu pork or roast duck), but you probably want to do more research when using in baking in addition to reading my notes below.

Today, we will talk about some random info on sugar, the science and process of making the syrup at home, and then finally some thoughts on how to use in cooking.

---

OK, let’s lay the foundation with sugar compounds.

When we say sugars, they fall in 2 categories, monossacharides (aka simple sugars), and disaccharides (aka compound sugars, made up of 2 joined monossacharides). Longer saccharides are not usually considered as sugars.

We have all heard of the following compounds: fructose, glucose, sucrose, and lactose. Along with galactose and maltose, they are related as follows:

We won’t really dive into galactose and lactose here, they are included for completion to give the greater picture.

Most of these sugars are consumed by us in our daily diet, either through natural foods such as honey and fruits, or through sweeteners/syrups. I have summarised a table below of what sugars are present in some common ones.

---

Next, making the syrup and the science behind it.

The idea is simple: we start with more complex carbohydrates, and break them down into smaller sugar compounds by using enzymes.

This is actually the same process as making several other types of syrups. For specific types of syrups, we need to just find the correct carbohydrate and enzyme combo that will yield the desired end-product.

For making maltose, what we want is alpha-amalyse, which is abundant in grains post-germination. Thus, in my case: carbohydrate = glutinous rice; enzymes = sprouted grains.

Translating this into practical steps, we have the following:

1. Sprout some wheat or barley [see picture captions for how-to], and chop it up

2. Cook some glutinous rice, let it cool to around 60C (or slightly lower)

3. Stir chopped sprouts into cooked rice

4. Create environment for enzyme reaction and let it do its work (~40-60C)

5. Filter solids from resulting liquid

6. Reduce liquid to form syrup

Yes, simple.

Except sprouting grains in winter took absolutely A-G-E-S. Not to mention that you have to babysit your sprouts everyday to make sure they grow healthy.

But hey, lockdown, and therefore, time.

Scroll down for pics and breakdown of the process :)

---

Sprouting Wheat/Barley (both would work)

SPROUTING: First you need to soak your grains overnight. Then lay them out roughly flat on a tray, and cover with a damp cloth. It’s important to keep your grains covered from sunlight, and you also need to keep them well hydrated. After a couple of days, they will start sprouting! The number of days this takes is temperature dependent. As I did this in early-Feb, it took me 5 days from leftmost pic to rightmost pic.

GROWING: Day 6, 7, 9, 11. Once they start sprouting, you will need to costantly keep it covered and damp. You will also need to remove any grains that did not sprout or have grown mould in the process, but you don’t have to clean it everyday. They grow really fast over this period, and by the time you have the rightmost pic here you are basically good to go!

Creating that Enzyme + Starch Reaction

PREPARING YOUR SPROUTS: I harvested mine on day 15 as I was busy cooking other things. Before adding them to cooked rice, you will need to gently separate individual sprouts, wash them, and remove any that have gone a little mouldy or have not grown at all. The you can roughly chop or blitz them in a processor/blender until they look like the rightmost pic. But don’t make it into a smoothie because you will need to filter these out later!

To make cooking sticky rice easier, I would recomment soaking the rice for 2-4 hours before cooking. Then steam the rice for ~30minutes until soft and mushy. Add your chopped up sprouts and put it mixture in a warm environment. I covered my pot and stuck it into a preheated-then-turned-off oven for around 4-5 hours. I would turn the oven on for 5mins to heat up (pot out of the oven during that time!) every 1.5 hours to maintain around 40-50C.

After a long wait, there should be seperable liquid seeping out from your mixture, at which point you would want to strain out the liquid and discard the rice/sprout (you can use it in compost!). If you have a muslin cloth, try and squeeze as much liquid out as possible.

Reducing Your Syrup - just boil it for a bit, it took me around 1hr20m

At first you can boil it on high heat.

When it starts to be covered with bubbles like these, reduce to low heat to avoid over-boiling.

This consistency means it’s done. Pour into container while it’s hot, as it will become very viscous after it cools.

My very own maltose syrup post-cooling.

---

Back to the science behind it. This process is similar to how corn syrup, barley malt, brown rice syrup, and the Japanese mizuame are made. Except you just replace the starch and sprouts with desired variants to achieve slightly different flavour profiles and compound mixtures.

Theoretically, you can also convert between the sugar compounds by using different enzymes because they are so closely connected (remember the first diagram?)! In fact, the various corn syrups (high-fructose, high-maltose) are made this way from your average corn syrup.

---

So how can you use maltose syrup?

In my opinion, you can use maltose syrup for any Chinese savoury dishes that requires a glossy glazing, especially meat, like char-siu pork. More commonly, it is used in making sweets, such as peanut brittles 花生酥, crunchy rice candy 米花糖, and sticky candy 牛皮糖. However, most recipes for both categories will not mention maltose syrup because other sweeteners (e.g. honey) are more readily available and recipes have adapted to the generic consumer, but there is no reason why you can’t substitute backwards by reintroducing it.

I used the remaining syrup in my pan to make salted caramel nuts.

If you want to try it out by substituting into Western recipes, here are some reference data on relative sweetness, caramelisation temperatures, and water solubility.

Sweetness data from here, others from Wikipedia. Even though their structures are relatively similar, their sweetness diverges greatly. Interestingly, recent research suggests that this may be correlated to the tightness of the hydrogen bonds.

Another thing to note is that maltose syrup made in this way differs from pure chemical versions because it retains some of the more complex compounds produced in the process — think date syrup/honey/maple syrup. As such, it has its own special flavour too: malty and delicate, a bit like barley malt crossed with brown rice syrup but less sweet.

Finally, as mentioned earlier, it is extra sticky and viscous, but could be warmed up for easier handling.

---