FOOD 2010 Chapter Notes - Chapter 10: Food Microbiology, Reduction Potential, Protozoa

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Chapter 10: Food Microbiology and Fermentation
10.1 What are Microorganisms
-microorganisms are living entities that are too small to be seen with the naked eye
-compromise bacteria, viruses, protozoa, and fungi (yeasts and molds)
-either procaryotes or eucaryotes
-procaryotes = no nucleus in cell - bacteria
-eucaryotes = have nucleus - fungi, protozoa, plants and animals
-viruses are neither cause they are noncellular
-bacteria are unicellular, and are divided into
-gram-positive (thick cell wall and no outer membrane)
-gram-negative (thin cell wall and an outer membrane)
-they are also either
-bacillus (rod)
-spirilium (twisty)
-coccus (small balls)
-some bacteria are able to develop into spores under unfavorable conditions thus
being more able to increase survival in heating, drying and irradiation
-they can then germinate into vegetative cells when conditions improve
-molds are multi or unicellular found in decaying organic matter
-yeasts are unicellular and can grow over a wide range of conditions
-protozoa are single-celled eucaryotes, classified by morphology, locomotion and
life cycle
10.2 Factors Affecting Microbial Growth
-Nutrient Availability
-chemotrophic organisms require chemicals for metabolism
sudivided into
-lithotrophic = require inorganic compounds
-organotrophic = require organic compounds
-phototrophic organisms require energy in the form of light
-nutrient needs depends on organisms and temperature
-may become more exacting in requirement during refrigeration
-water activity
-bacteria need quite a bit of water, minimum aw of 0.90
-yeasts need minimum aw of 0.80
-molds need a minimum aw of 0.70
-this is just a general there are some exceptions
-acidity/alkalinity
-bacteria cannot survive under pH 4.5, optimum 6.5-7.5
-yeasts can live anywhere from pH 3.0-8.5, optimum 4.0-6.5
-molds between pH 2.0-11.0, optimum 4.5-6.8
-the ions will prevent the microorganisms ability to transport molecules in or
out of the cell through the cell membrane
-oxygen
-molds require oxygen (aerobes)
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Document Summary

Procaryotes = no nucleus in cell - bacteria. Eucaryotes = have nucleus - fungi, protozoa, plants and animals. Microorganisms are living entities that are too small to be seen with the naked eye. Compromise bacteria, viruses, protozoa, and fungi (yeasts and molds) Some bacteria are able to develop into spores under unfavorable conditions thus being more able to increase survival in heating, drying and irradiation. Molds are multi or unicellular found in decaying organic matter. Yeasts are unicellular and can grow over a wide range of conditions. Protozoa are single-celled eucaryotes, classified by morphology, locomotion and life cycle. Gram-positive (thick cell wall and no outer membrane) Gram-negative (thin cell wall and an outer membrane) They can then germinate into vegetative cells when conditions improve. Phototrophic organisms require energy in the form of light. May become more exacting in requirement during refrigeration. Bacteria need quite a bit of water, minimum aw of 0. 90.

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