Q: Is there a quick easy test for gram positive or negative bacteria that does not use the gram staining procedure?
A: Most common beer spoilers are gram positive bacteria. If you see a bacterial colony growing on a petri dish you can use a quick test to screen it for a gram positive reaction. Place a loop of the colony onto a slide (using sterile technique) and place a drop of potassium hydroxide on the colony. Using the loop check to see if the colony appears “gooey” or not. A gooey consistency indicates a gram negative colony while a non-gooey consistency indicates a gram positive. Perform a proper gram stain to confirm this is a gram positive organism.