Why does juice darken?

[BradJ]

I've been back on stinkies for a while (I kinda suck like that) but I have/had some really good home-made juice (for me it's always been about quitting cigs), which is tobacco flavor, with a hint of apple, around 15mg/ml.

It was clear and yellow, tasted great, but now it's much darker.

Why does that happen, and how and/or has it degraded?

Been prolly six months.

 

[Kenna]

Most juices will darken with age. Tobacco, vanilla, nic, & other ingredients darken naturally. Plus even exposure to a bit of air in a bottle allows oxidation. Probably fine to vape tho. It would take a long time to weaken the juice I believe.

Sent from my SAMSUNG-SGH-I317 using Tapatalk

 

[IDJoel]

What @Kenna shared is pretty much my understanding too. Time, heat, exposure to air (open tops and excess air/room in the bottle), and ultraviolet, will all contribute to e-liquids changing color (usually darker though some nicotines will develop a pink or orange hue). I am not aware of anything harmful that is created over time (of course we still don't know a lot about vaping... we each have to set our own level of "acceptable" risk). Nicotine will loose its potency as it oxidizes, and flavor may become unpleasant or weak, but if it tastes good... vape away.

If you would like a more scientific explanation you might want to ask your question again in the "Ask The Chemist" thread.

 

[Stosh]

Nicotine will darken with age, exposure to light and oxygen, but has very little effect on strength.

Madvapes did an experiment a couple years or so age...took bottles of exactly the same nic concentrate and stored one in the freezer in the dark, another at room temperature, up to and including one bottle on the windowsill in the sun. Testing the strength weekly and monthly, the windowsill bottle only dropped a tenth or two in potency in months of exposure although it darkened considerably.

 

[IDJoel]

I guess it is a matter of perception. To me; 8.57% degradation in 4 months is not insignificant (35mg/mL to 32mg/mL) for the window sill example your reference. I understand too that the "Office" sample only degraded 2.86% (35mg/mL to 34mg/mL) over the same time period. I have no idea how @BradJ has stored his e-liquid to this point and I did not intend to suggest any specific results regarding his juice; only possible cause/effect.

For those that would like to look at the test, it can be found here: Madvapes Blog - Nicotine Concentration Over Time | Madvapes

To me there are a few significant pieces of information missing:
--Type of containers: Glass or plastic(HDPE, LDPE, PET)? Clear, frosted/translucent, tinted?
--How much headspace?
--At what temperatures were the liquids at?
--Was the window south-facing, north facing, or ?
--What was the duration of exposure to direct (?) sunlight each day?
--Type of window: single pane, double pane, was the glass treated for UV blockage?
--What happened on months 5 & 6?

For kitchen sink science I have no problem with this, and anecdotally I find it interesting, but I'm not going to pull my nic stash out of the freezer based on this.

 

[DaveP]

Stosh Wrote:
Nicotine will darken with age, exposure to light and oxygen, but has very little effect on strength.
Madvapes did an experiment a couple years or so age...took bottles of exactly the same nic concentrate and stored one in the freezer in the dark, another at room temperature, up to and including one bottle on the windowsill in the sun. Testing the strength weekly and monthly, the window sill bottle only dropped a tenth or two in potency in months of exposure although it darkened considerably.

I've procrastinated now for several months getting my nic into 8oz boston rounds with polycone tops. I have the new bottles. It's still clear and smells the same after 4 or 5 months sitting on a shelf, in a box, with only room light. One bottle is still sealed and the other is capped and missing about 2 to 3 inches down from the top.

I've got to get it into the freezer. Its projected life at 3mg juice strength/ 10ml a day is 18 years for the two bottles, so I need to get it into the freezer soon. If I were vaping rapidly enough to use it up in a couple or three years I wouldn't ever worry about freezing.

 

[SupplyDaddy]

Since you are talking about eliquid with flavors added, it is "steeped" or as other places or industries would say "aged".

A light changing of color is normal and usually expected. It shows that all the bits and parts are now combined about as good as they should be and are probably at the best they will be. A longer steep time may or may not improve the flavor, and may darken the mix.
Best way to find out is to try it.

 

[dannyv45]

I believe the OP is not talking about nicotine storage or why raw nicotine discolors. I believe he's talking about the juice they already made.

We all know proper storage of nicotine will greatly improve shelf life of nicotine solution.

But already made juice can darken dramatically over time not only because of nicotine oxidation but also because of flavor molecule interaction with Nicotine. Take for instance chocolate. The flavoring in it's original manufactures bottle can start out crystal clear and when added to a nicotine base can turn dark brown within a few months. The OP I think is asking "Is this a sign of spoilage and is it safe to still vape"?

The answer to this question is it has NOT spoiled and it is safe to vape and the discoloration is a normal occurrence.

I have mixed e-juice well over 2 years old that is safe to vape and actually taste far better then when originally made. The base acts as a preservative and is for the most part antimicrobial meaning bacteria can not exist or grow in this environment. So the base actually prevents spoilage.

 

[Fozzy71]

From a forum I am not allowed to link to:

2. The development of complex flavour molecules.

Over time some e-Liquids especially custard / caramel or desert flavours darken over time
From observation this cannot be oxidation as it occurs uniformly through the liquid and does not require agitation of the liquid to occur.
It also cannot be caramelization as this does not occur below 110°C.

Maillard Reaction - Colour and flavour

What seems to be happening is a Maillard reaction commonly experienced by most people every day. The browning of bread, toast and potato chips these are high temperature examples. Medium temperature examples creating Dulce de leche and condensed milk.
Mallard reactions also occur at lower temperatures and contribute to the aging of wine and Balsamic Vinegar.

Maillard reactions get exponentially slower as they progress
This fits in with our observations of steeping e-Liquid, a golden colour may be observed in a couple of days however the full desired flavour and colour may take 4-6 weeks to develop.

The Maillard reactions will continue to progress over time, hence those almost black bottles of e-Liquid that are found at the back of a draw.

The degree of colour change is dependent on the type of flavours present and the presence of Nicotine
Some flavours wont change at all these are often referred to as shake and vape liquids.
This mirrors the culinary world, you never see matured lemonade being sold.

 

[f4milytime]

Flavored juice WITH nic, will usually darken more. Than flavored juice WITHOUT nic.

 

[smacuser]

The Maillard reactions will continue to progress over time, hence those almost black bottles of e-Liquid that are found at the back of a draw.

I'd vape that. not.

 

[ChelsB]

From a forum I am not allowed to link to:

2. The development of complex flavour molecules.

Over time some e-Liquids especially custard / caramel or desert flavours darken over time
From observation this cannot be oxidation as it occurs uniformly through the liquid and does not require agitation of the liquid to occur.
It also cannot be caramelization as this does not occur below 110°C.

Maillard Reaction - Colour and flavour

What seems to be happening is a Maillard reaction commonly experienced by most people every day. The browning of bread, toast and potato chips these are high temperature examples. Medium temperature examples creating Dulce de leche and condensed milk.
Mallard reactions also occur at lower temperatures and contribute to the aging of wine and Balsamic Vinegar.

Maillard reactions get exponentially slower as they progress
This fits in with our observations of steeping e-Liquid, a golden colour may be observed in a couple of days however the full desired flavour and colour may take 4-6 weeks to develop.

The Maillard reactions will continue to progress over time, hence those almost black bottles of e-Liquid that are found at the back of a draw.

The degree of colour change is dependent on the type of flavours present and the presence of Nicotine
Some flavours wont change at all these are often referred to as shake and vape liquids.
This mirrors the culinary world, you never see matured lemonade being sold.

Excellent explanation [emoji106]

 

[DaveP]

But already made juice can darken dramatically over time not only because of nicotine oxidation but also because of flavor molecule interaction with Nicotine. Take for instance chocolate. The flavoring in it's original manufactures bottle can start out crystal clear and when added to a nicotine base can turn dark brown within a few months. The OP I think is asking "Is this a sign of spoilage and is it safe to still vape"?

The answer to this question is it has NOT spoiled and it is safe to vape and the discoloration is a normal occurrence.

I agree. If it tastes good, vape it.

 

[BradJ]

Thanks all. It's a plastic 30ML bottle, kind of frosted. Not sure exactly what kind of plastic. 90% full so less than a centimeter of headspace. I keep them both capped tightly in a room temperature tackle box, so not much air or light, usually around 70-73 degrees.

Weird thing is that the store-bought juice I tried to copy is still a light yellow, while mine is significantly darker.

Still vapes well, though, so I'm going with it.

Appreciate all of your replies.

 

[IDJoel]

Weird thing is that the store-bought juice I tried to copy is still a light yellow, while mine is significantly darker.

Color difference might simply be due to the difference in ingredients (and amounts) used in each. If it tastes good; vape it!