Many harmful microorganisms do not produce any odors. Smell
alone is not a perfect indicator of spoilage.
You probably can't tell, but if no one else is around to sniff the
meat for you, then "when in doubt, throw it out." But according to
the Department of Agriculture, spoiled meat generally doesn't make
people sick -- it's the pathogens that cause all the problems, like
e.coli bacteria. I personally have cooked and consumed meat that I
thought was a day or two past its prime, but have never suffered
allowing your other senses to help. looking at the meat you would
notice a change in color , sometimes the whole will be affected and
sometimes only in spots. look carefully. the other way is texture
and how it "feels". it can change in "density" (how firm or mushy
it might feel). another change would be that a superficial film
developes that you can feel.(a thin "slime" or slickness). the rule
of "when in doubt throw it out" is a good one, follow it,
especially if it concerns chicken, "ground" anything and seafoods.
the importance of temperature cannot be stressed enough. a refrig
should always be kept below 40 degrees and foods should always be
heated to 145 degrees, (leftovers to 165 degrees). it is imperative
to keep foods out of the 40 to 145 degree range!!! these temps
allow rampant reproduction of bacteria.
Please also be aware that meat and especially chicken that's been
unrefrigerated too long can contain bacteria or viruses that will
give you food poisoning. These are absolutely odorless and
colorless, so even with a keen sense of smell, you'll never know
they're present. Foodborne illness is much more common than
actually eating rotten food.