you should be able to use it with food. do your self a favor and buy some ph buffer tho;hanna HI 70300 is an example of this fluid.
you HAVE to store the probe wet, otherwise it will ruin quickly,also never store it in ro/DI water it will also ruin it.
also after you use it you should flush the tip with clean water and store it with the buffer like i said.
a little advice if i may be so bold, buy a hanna or another meter that has a warrenty on the PROBE. imo you have like a 50% shot of getting a good probe with the ultra cheep meters. if it dosent calibrate, contact the manufacturer and request a replacement. ive done this with hanna and they had great service.