I tried carbonating tomatoes first, and while they were a unique taste sensation, they weren't actually an improvement. I think something with a higher sugar content would be much better tasting.
I'm using "tangelos" which are a hybrid of tangerines. They are relatively small, very sweet, and easy to peel. For those reasons, I thought they would be good to try. Also I had a bag of them....
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Step 1: Add to the Water Bottle
In this trial, I filled the bottle with water and fruit. I thought that this might aid carbonation, since the CO2 could pass into the water, which could also pass through the cell walls of the fruit. I thought it might help diffuse the CO2 throughout all of the fruit.
Theoretically, filling the bottle with water is safer than just carbonating the fruit alone. With the fruit alone, gas is forced into the bottle, and it is under a lot of pressure as the gas fills the available space. When the bottle is filled with water, the gas is forced into the liquid and can't pressurize enough to potentially rupture the plastic and explode. I'm pretty sure that the soda stream has a pressure relief valve built in so there isn't any real worry, but theoretically this is a safer method.
I filled the bottle to the recommended line on the soda stream, and then added fruit, pouring off water to keep it at the fill line as the oranges displaced it. I didn't keep track of how many I added, but it was quite a few. Let's say seven or eight whole tangelos went in, which loosely filled the water bottle about halfway.
Step 2: Carbonate!
Instead of shooting the CO2 in one long blast as is my normal method with water, I used short bursts. The fruit was knocked around by the high pressure jet as the gas shot into the bottle, and I didn't want to disintegrate the orange wedges as they swirled around.
There was a lot more bubbles and fizzing in the bottle than normal. Typically the water fizzes up as the CO2 is charging it, but then dissipates instantly once the button is released. It took several second for it to dissipate with the orange slices in. This should have been a warning sign to me for the next step...
Step 3: Messy Removal
I casually twisted the bottle from the sodastream, expecting to cap it like any other time. However, releasing the seal caused the bottle to foam up torrentially, spraying water everywhere. I tried to retighten onto the sodastream, hoping that would stem the flood, but it did not, instead shooting water up into the inside of the machine along the carbonation tube.
Probably, I should have placed the entire assembly in the refrigerator again, to give the CO2 time to permeate the oranges. I suspect I lost most of the carbonation this way, as it escaped the bottle.
I capped it and put it in the refrigerator to see what would happen anyways.
Step 4: Decanting for a Soda and Fruit Snack
After waiting several hours, I poured the water out into glasses to make a Honey Orange Syrup soda that I had been preparing simultaneously. I thought that mildly orange flavored water would be a good base for it.
After the water was drained from the bottle, I dumped the oranges out into a bowl, shaking to get them out. It is a lot easier to get them in than out- if you do this, make sure you get your oranges down to their smallest possible segments.
The oranges were fizzy and sparkling on the tongue, but not nearly as much as the tomatoes had been. I think the gas explosion really robbed them of all the carbonation. I think that keeping them in the water didn't make much difference, or maybe even was detrimental since some of the orange flavoring and sweetness was leeched into the water.
Despite the above, these were still pretty good to eat, and I ate the equivalent of 3 tangelos this way in a single sitting. Doing so, I was able to discern the mild alarm I had when I was tasting them. The only time fruit gets fizzy like this naturally is when it has gone bad and is fermenting. This has the sensations of that, without the off flavors that result. However, the associations can be hard to break. People who have never had bad fruit may not feel this way.
This is a fast project, and easy. I recommend it for children as long as they are careful unscrewing the bottle.