Firstly - It's a neutral base - so it's essentially flavourless and adds texture/mouthfeel to the drink and also holds the drink together longer, so doesn't seperate quickly.
As for using it in a Slushie machine – it will depend on what products they are using because of the sugar levels etc. to ensure the beverage doesn’t freeze but for our products we use 1 ltr of our smoothie mix, 500ml of frappe choice & 4 litres of water.
This is some info from our Slushie supplier; The liquid mix would actually be better than powder so they're on the right track.
You would also need to run the temperature a bit warmer than you would for a slushie mix. They would need to play around with this a bit to get the right temperature but basically the frappe base freezes quicker than the slushie mix.
Here is a link to the DaVinci Gourmet Liquid Frappe Choice
Here is a link to our Fruit Smoothie Suppliers, you have a great choice.