CHAPTER VII 
YEASTS AND MOLDS 
Tur molds may be responsible for many changes in foods. Their 
action, however, should be considered from two standpoints since they 
bring about desirable and undesirable changes. A type of the former 
in the manufacture of Camembert and Roquefort cheese while the 
spoilage of strawberries and citrus fruits may be offered as an example 
of the latter. Tas Yu, the Chinese drink, is also said to be fermented 
in part by molds. 
Fungi. These are plants which possess no chlorophyl and conse- 
quently are unable to utilize the energy in sunlight. All of it must come 
from analytic processes. They do not construct their own starch but 
use that which has been built up by other organisms. For convenience, 
fungi have been divided into the following main groups. To the food 
microbiologist, these may not be so important but may be helpful in 
the identification of unknown fung1. 
Ascomycetes. This class produces ascospores or spores in an ascus. 
The yeasts since they possess this characteristic are put into this group. 
The aspergillacese are ascomycetes. Some of these form perithecia 
which contain ascl. 
Basidiomycetes. The spore-bearing bodies are termed basidia and 
possess a typical morphology. The conidia are produced from this on 
the sterigmata which may be either branched or unbranched. 
Phycomycetes. In this group are placed the alge. None of the 
fungi belonging to this group are commonly met with in food micro- 
biology. 
Fungi Imperfecti. Into this group are placed many fungi which 
do not come under any of the above groups. The fungi: imperfect 
are characterized by no definite fruiting bodies. Ozrdiuwm lactis is the 
best example and in this fungus each mycelial thread breaks up to 
form oidia which may develop into a new plant. 
Structure of Molds. The body of the mold is made up of a cotton- 
like structure called the mycelium. Each individual thread is called a 
mycelial thread or hypha. The hyphe are of two kinds—fertile and 
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