Because some kinds are psychrophiles, they can create a spoilage problem in meat coolers and other refrigerated storage areas. Unlike bacteria, which multiply by binary fission, yeasts reproduce by a method called budding. A small knob or bud forms on the parent cell, grows and finally separates to become a new yeast dell. Although this is the most common method of reproduction, yeasts also multiply by the formation of spores. Because they can grow under conditions of high salt or sugar content, they can cause the spoilage of certain foods in which bacteria would not grow.
Examples are honey, jellies, maple syrup and sweetened condensed milk.
Foods produced by the bacterial fermentation process, such as pickles and sauerkraut, can also be spoiled by yeasts which interfere with the normal fermentative process. Certain yeasts are pathogenic. However, yeast infections are much less common than are bacterial infections. Probably the best known microorganisms, molds are widely distributed in nature and grow under a variety of conditions in which air and moisture are present. They are also plants and a part of the fungi family.