The team at SWAY knows a thing or two about good prep. They also know that fresh ingredients change flavour depending on how it's prepared.
There's a big difference between a cooked berry syrup with jammy flavours and a cold juiced raspberry simple syrup. Similarly, there's a dramatic change in final flavour if we choose to blanch herbs as the first step to make our prep look nicer for longer.
When it comes to the flavour of fresh basil, the old method of blanching just wasn't good enough for the team at SWAY so the founders, Eric Söderlund and Christoffer Bergqvist, set out to experiment with different techniques.
It all began with a simple question. "How can we get the fresh flavour of basil without it going brown?".
If you are a professional bartender, you might at some point have asked yourself "how do I make a good basil cordial?" or wondered "how can I make a mint syrup?". You might even have gone ahead and blended a simple syrup with your herb of choice before straining it and calling it a success. After all, you did end up with a flavourful, bright green ingredient for your drinks.
That is of course until it's just a few hours old, at which point it begins to go brown and lose it's kick.
The problem, in more fancy terms, is something called enzymatic browning. It's the same process that happens when you cut an avocado and it goes brown almost immediately before you can finish scooping it into your guacamole bowl. The sinner behind this process is called polyphenol oxidase, or PPO for short.
Without getting too distracted on the chemistry behind it, PPO is the reason your avocados, apples and fresh basil syrup quickly goes brown when left in the presence of air. PPO is released from your ingredient's cells when a fruit or herb is cut, bruised or otherwise broken. This means that every turn of the blades in your blender releases PPO from the herb which moves your syrup's life span onto a very fast train to brown town.
The Original Fix
As mentioned already, this process is called enzymatic browning. If we take a second to look at the name of the sinner, "polyphenol oxidase", we notice it ends with -ase which in chemistry terms indicate it's an enzyme.
If you've read about whiskey production you might have heard of amylase, if you're into clarification you might know pectinase, and if you're nerding out on koji fermentation you might also know protease and lipase.
Every one of these ends with -ase and the thing before it indicates what the enzyme works with. Amylase reacts on starch, pectinase on pectin, protease on proteins, lipase on fats and polyphenol oxidase on polyphenols and oxygen.
Another thing all these enzymes have in common, apart from the same surname, is that they are deactivated at high enough temperatures. Some heat will make them work faster, but too much heat will deactivate them entirely and this is why blanching is a common approach for preventing browning.
By blanching herbs in boiling water for just 20-30 seconds, the PPO can be effectively deactivated, although at a cost to fresh flavour.
At a core temperature of 100°C, around 90% of PPO is destroyed in just 2 seconds, whereas it takes around 2 minutes to achieve the same effect at the lower temperature of 90°C.
When blanching herbs, it's important to move them straight from the boil to an ice bath in order to cool quickly and reduce the cooking effects. This is done mainly as a step to minimise flavour change when making infusions or to prevent further softening when cooking.
Alternative Efforts
Knowing that blanching works, but also changes the flavour, the creative limitation was easily set by the team at SWAY by ruling out blanching for the prep.
This now brings the focus to two simple questions.
- How do we extract the most flavour from the herb?
- While at the same time keeping PPO under control and avoid browning?
The team understood that enzymatic reactions are slowed by cold, so they started off by testing a simple cold water infusion in the fridge for up to 36 hours. The problem here is that flavour infusions are also affected by lower temperatures, so this was too slow and infusing whole basil didn't bring enough flavour.
The next natural option was to speed things up by increasing the surface area, so pre-chilled water was put in a blender with fresh basil which gave that super green colour, and a lot more flavour but it was too fine to strain easily and the browning followed quickly.
The insight came as a middle ground. If the story of Newton and a falling apple works to explain the insight of gravity, then the solution to perfect herb infused sodas can be imagined as an apple lasting longer by squeezing lime over it.
The Acid Solution
When you squeeze a wedge of fresh lime over a sliced apple, a cut avocado, or straight into your guacamole, it visibly slows down the browning.
Acids in the lime, a combination of citric, malic and ascorbic acids, slow down the enzymatic browning caused by PPO. This happens because ascorbic acid gets in the way of the enzymes, effectively working as a temporary sacrificial shield, while citric and malic acids lower pH which slows the reactions overall.
The team at SWAY wanted to create a basil infusion with the very specific purpose of using it in a carbonated soda for drinks. Since a flavoured soda is often balanced with both sugar and acids, the team found an opportunity to use acids creatively as a way to slow browning enough that a longer cold infusion would become possible.
By creating an acid solution with just over 0.5% citric acid, 0.5% malic acid and a small 0.25% ascorbic acid in the mix, the combination of this with the fridge temperatures allowed for a stable green mixture!
But the flavour was still not strong enough...
Introducing Frost Bloom
The final step to the innovative process was combining the cold acid bath with modern techniques for flavour extraction. Before adding the basil to the cold acid solution, the team left the basil in the freezer over night to go completely solid.
The technique of first freezing fresh ingredients, and then letting them thaw to improve infusions, is based on how water expands as it turns to ice. As the water in the basil leaves freeze solid, they form large crystals that slowly break apart the cells to release all the aromatic compounds which ultimately leads to more flavour.
After freezing, the team roughly chops the basil, combines it with the pre-chilled acid solution and leaves it to infuse for 24 hours before it's a simple case of filtering off the leaves, adding sugar and carbonating at high pressure for that perfect serve soda.
The Recipe
SWAY Basil Soda
Prep ingredients
- 75 g Basil (Leaves and Stems)
- 2 g Earl Grey Tea
- 1000 g Water
- 2.5 g Ascorbic Acid
- 5.65 g Citric Acid
- 5.65 g Malic Acid
- 90 g Sugar
Yield
1000 ml
Instructions
Freeze the basil (leaves and stems) and earl grey tea. Prepare acid-adjusted water by dissolving ascorbic acid, citric acid, and malic acid in 1 litre of water chilled to 4°C. Crush the frozen basil and add to the acid-adjusted water. Store in the fridge for 24 hours. Strain away the…
Eric, Christoffer and the team at SWAY continue to expand their knowledge on this new piece of prep and are openly sharing it via their website.
You can read more about SWAY and their Frost Bloom technique on their website which includes an insight into their new work using mint instead of basil.
If you want to check out more of their shared menu prep published on Peche, you can check it all out here
