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What conditions are the most favourable for microbial food production? -…
What conditions are the most favourable for microbial food production?
Types of microbes
Yeast
Saccharomyces cerevisiae
Scheffersomyces stipitis
Yarrowia lipolytica
Dekkera bruxellensis
Kluyveromyces lactis
Bacteria
Lactic Acid
Enterococcus
Carnobacterium
Lactobacillus
Lactococcus
Leuconostoc
Oenococcus
Pediococcus
Streptococcus
Tetragenococcus
Vagococcus
Weissella
Fungi/Molds
Mucorales
Aspergillus
Penicillium
Monascus
Actinomycetes
Mucor
Rhizopus
Amylomyces
Neurospora
Chosen Experiment Variables
Independent: The temperature of the yeast solution
Dependent: The growth of yeast over a period of time
Controlled:
Amount of yeast
pH level
Concentration of sugar solution yeast is placed in
Moisture
water is a requirement for growth and metabolism and supports many chemical reactions that occur in food products. Therefore, the minimisation of moisture content will reduce the growth of bacteria and will ensure the longer preservation of food.
Bacteria
Most bacteria need a minimum moisture level of 60% in order to grow effectively
Fungi/Mold
Mold grows best when subjected to a moisture level of around 55%
The growth of fungi is most efficient when subjected to a moisture level of 35% to 50% however they are able to grow at around minimum 20% - 30%
Yeast
Yeast requires a relatively high moisture level of above 85%
pH Level
Moderate changes in pH modify the ionization of amino-acid functional groups and disrupt hydrogen bonding, which, in turn, promotes changes in the folding of the molecule, promoting denaturation and destroying activity.
Bacteria
Most bacteria require a pH level of between 6.5 and 7, however some are able to survive in pH levels as low as 1
Yeast
Yeast needs a pH level of between 4 and 6 in order to grow effectively
Fungi/Mold
Fungi requires a pH level of approximately 4.5 to grow effieciently
Mold can grow in pH levels ranging from 3.5 to 8
Temperature
As the temperature increases, molecules move faster, enzymes speed up metabolism and cells rapidly increase in size.
Yeast
Water at 26°C are considered the optimum temperature for achieving yeast multiplication. Water at 27°C to 37°C is the optimum temperature range for the fermentation process. Water at 35°C is the fermentation temperature that yields the best result. Water at 60°C or higher is the kill zone for yeast
Bacteria
Bacteria can grow at temperatures anywhere from 5 to 60 degrees celsius
Fungi/Mold
Fungi's and mold's optimal temperature for growth is around
25-30°C
Nutrients
Microorganisms require certain basic nutrients for the growth and maintenance of metabolic functions.
Two categories of essential nutrients are macro- and micro-nutrients.
micronutrient
: an element or nutrient required in small quantities.
macronutrients
: any element or nutrient required in large amounts.
Yeast
Nitrogen (YAN), vitamins (thiamine) and mineral salts (Mg, Zn) are essential for yeast activity. The use of sugar acts as a source of nutrients and energy
Yeast also needs plenty of oxygen
Bacteria
Bacteria need water, a source of carbon, a source of nitrogen and some inorganic salts in order to grow
Fungi/Mold
Potential Experiments
Yeast
Yeast suspension testing how different sugar levels effect yeast growth
Yeast suspension in water baths, testing how temperature affects the growth of yeast
Make dough balls of the same weight and let rise in different temperature environments. Measure how much they rise and how much their size increases
Ferment yeast with other ingredients to create alcohol. Test what amounts of yeast are most favourable for alcohol.
Make alcohol and test what temperature is most efficient in the fermentation process of yeast
Place yeast into solutions of different pH levels. Test how different levels affect the growth of the yeast.
Bacteria
Test in agar plates how different temperatures effect the growth of different bacteria
Make yoghurt with different aounts of bacteria and test how it effects the final product
Make yoghurt and test what the ultimate temperature is for bacterial growth in yoghurt. What temperature makes the best yoghurt?
Place bacteria into agar plates or solutions of different pH levels, measure how the different levels effect the growth of bacteria
Fungi/Mold
Place fungi into different temperature conditions, testing how temperature affects the growth of the fungi/mold
Place fungi/mold in environments containing different pH levels. Test how the different levels effect the growth