Tried a fizzy fruit recipe at home that turned out with inferior results? This guide will help you to resolve your problem.
There are several key variables to consider when creating delicious fizzy fruit with dry ice. in order of precedence: 1) Temperature; 2) Concentration of CO2 3) Time, 4) The fruit's flesh density, 5) the fruit's water content, and 6) the fruit's sugar content. I will not delve too deeply into the chemistry for this purpose.
1. Temperature. As you may be aware, CO2 readily absorbs into water (e.g. soda). The colder the water, the greater the amount of CO2 that can be absorbed. However, water ice inhibits CO2 absorption and also causes it to lose its ability to hold CO2, which is why frozen cans of pop can explode, as the ice crystals actually force CO2 out of the can.
You want to chill your fruit as much as possible without freezing it, then maintain that temperature. 2C is the ideal temperature, which corresponds to the temperature of a very cold refrigerator. Personally, I abandoned the dry ice method (there are several ways to make fizzy fruits) because dry ice is -78C in its frozen state. As it sublimates, the gas's temperature is also approximately this low, resulting in extremely easy freezing of fruit.
If your fruit becomes frozen, it will not absorb CO2 and will lose its sparkle. However, if the fruit is still quite warm after being exposed to dry ice, you're either not using enough or the chunks are too large (causing moisture to stick to the dry ice and slow sublimation).
It's extremely difficult to obtain the correct amount of dry ice because it must be used to cool the fruit to near-freezing temperatures without freezing it and while it is constantly sublimating.
2. Concentration of CO2. This is the other issue with the dry ice method: not only must the fruit be kept at or near 2 degrees Celsius by the dry ice, but the CO2 concentration in the cooler must also be extremely high to displace enough oxygen. Extremely difficult to control because as the temperature in the cooler decreases, sublimation also decreases.
3. Time. You must expose the fruit for an extended period of time at low temperatures in order for the water trapped in the fibres to absorb CO2. However, once the first two variables are under control, achieving effervescence is relatively simple.
4. Density of fruit. Certain fruits are more effective than others. Generally, the more watery the outside of the fruit is, the more easily it fizzes, as there is no fibre to prevent CO2 absorption. For example, a grape cut in half fizzes much more quickly than an entire grape. Oranges that have been cut vs. oranges that have been whole. Pineapple chunks vs. a pineapple cut in half. It is possible to achieve a light sparkling effect simply by doing this, even if the first three variables are jumbled, but the result will be somewhat random.
5. The amount of water contained. The more water there is, the greater the potential for CO2 absorption. Due to variables 4 and 5, watermelon is essentially the ideal fruit.
6. Sweetness. This, I believe, has no effect on effervescence. However, due to the fact that carbonic acid is...acidic, sweet fruit helps to balance it out. This will probably matter more once you've mastered the fizzing.
Additionally, there is pressure. Increase the pressure inside a container by a factor of two, and the amount of CO2 that can be absorbed into any water contained within that container doubles. You can't really control this much with a cooler because it's not completely airtight, and you don't want to with dry ice. Dry ice has such a high expansion ratio that it easily blows things up. Unless you are certain, DO NOT seal dry ice in an airtight container.