Define Petri Plates - Food Microbiology?

Petri plates were discovered by Richard Petri in Ninteenth century (1887). It consists of two dishes. Look at the Figure which illustrates the two dishes and petri plate can.

Figure: Petri plate and petri plate can

Bottom dishes (base) are smaller and carry 20-25 ml of the culture medium. Upper plate (cover) is bigger and provides a loose cover to bottom dish to avoid contamination. Petri plates are available in different sizes but for routine purpose, generally, plate of 9-10 cm diameter is used. Liquefied molten solid culture medium is poured into the bottom plate and is allowed to solidify. As petri plates provide larger surface area, these are useful for isolation and cultivation of microorganisms.: Storage and incubation of petri plates should be done in an inverted position to prevent dropping down of water droplets formed by condensation during solidification of media on to the surface of the hardened agar surface. This can spread the microorganisms on the agar surface, resulting in confluent growth instead of discrete colonies.