There are various types of microorganisms that can be found in milk and related products depending on the hygiene standards followed.
The microorganisms found in milk and milk related products are classified as unfavorable- ones that are responsible for causing spoilage, and favorable- ones that responsible for bringing about desired changes in the products. There are various established methods available to enumerate the type of the microorganisms present along with their quantification. To ensure that the consumer gets a safe product for consumption various bodies like the FDA and Codex have established the product regulatory standards that all the milk producers and processors are supposed to meet across the product marketing chain.
1. Bacteria - These are single celled microorganisms, normally measured in microns and one of the methods of their classification is based on the fundamental shapes that they exhibit: a. Spherical, b. rod and c. spiral. They reproduce asexually by fission and their growth phase is characterized by distinct phases:
2. Yeasts - These belong to the group of microorganisms called fungi. These are classified on the basis of morphology, cultural, sexual and physiological characters. Based on their method of reproduction, there are two forms that are of importance in the food industry.
a. Budding and spore forming yeasts: These are also called as true yeasts and reproduce by producing sexual ascospores.
b. Budding or Asexual yeasts: These are also called false yeasts.
3. Molds - These also belong to the class of fungi and are multi-celled and filamentous, the filaments being referred to as hypha. These too can reproduce either sexually or asexually. The sexual reproduction normally happens in the unfavorable conditions by forming spores through the process of nuclear fission, whereas the asexual reproduction happens through either fragmentation or spore production in conidia.
4. Viruses - These are intracellular parasites. They need to contact and invade an acceptable host cell to survive and replicate.
Factors affecting growth
As enumerated by Banwart (102-144), in any food environment, some microbial species will survive and become dominant. Organisms that lack the ability to withstand stresses induced by unfavorable environment will succumb. The conditions that affect the metabolism and multiplication of microorganisms include the following:
1. Nutrients - These are required as source of energy and for synthesis of cellular