What are some ways to salvage food that has started to spoil?

Yesterday, I bought a reduced eye of the round beef roast for the crock pot that still had 3 days left on the expiry date. Well fudge... I left it on the counter over night. And with beef being so expensive too (here in Canada). My mother in law advised me to wash it thoroughly in vinigar before deciding it was bad as this would kill any bacteria that had started to develop. She also said that if that doesn't work to cut it in half and see how the inside smelled as I could just shave off the outside half inch or so. Thankfully after rinsing the vinigar off, the meat seemed ok. My apartment was only about 75 degrees last night. Aparently this tecnique was common practice before refridgeration. Wouldn't want to try that with chicken.