I finally found the culprit to the mysterious ristretto_xxxxxxxtmp files, thanks to a post I found from an Australian forum.
The file is being generated by the app Vlingo when it is setup to speak out emails from Hotmail accounts. It doesn't generate this file with gmail or yahoo mail. Simply remove or disable the hotmail account in Vlingo and the ristretto files will disappear.
Here's the original post that I found...
Hi there. --------- Ristretto tmp files issue.
Well I had to share my findings, couldn't be selfish and not to share.
Thats why I signed to this board, just to post my findings.
)
I have my galaxy and experienced ristretto files popin at an alarming rate chocking the memory. After talking to useless technical support on both (ATT and Samsung) sides I decided to resolve it myself and found a solution (at least it worked for me).
1. You can delete these files but they will come back, so dont waist your time. Delete them after you do the next step.
2. The app that generate these ristretto_XXXtmp files is "Vlingo" this app reads out the emails, texts, etc. in audio format and allows to control the device by voice which is very cool by itself. The option in the app that causes these files to appear is when you let the app to read (read it alloud) emails from your hotmail account only (yahoo and gmail work fine).
So if you dont mind that your emails from hotmail account will not be read than disable this feature and these ristretto files will stop to multiply.
Spread the word, and let me know if it works.