MICR-4070 Lecture Notes - Lecture 4: Relative Growth Rate, Magnetic Ink Character Recognition, Organism
Document Summary
Micr 4070: factors affecting microbes in foods (lecture 4) For good microorganisms, you want to decrease the lag phase as much as possible. Log phase: there are optimal conditions and plenty of nutrients for growth. Stationary phase: not enough nutrients or not enough room for growth. Death phase: microorganisms are dying more than new cells are growing. Representative specific growth rates & doubling times of microorganisms. Internal ph of almost all cells is near neutrality. Organic acids enter the cell only in the protonated (undissociated) form. Intracellular ph should be above some critical ph at which intracellular proteins become denatured. Mechanisms for bacterial cells to respond to acidity (ph: homeostatic mechanism: ph0>6. 0. Monday, january 22, 2018: acid tolerance response (atr): ph0 of 5. 5-6. 0, synthesis of acid shock proteins: ph0 of 3. 0-5. 0 ph homeostasis ph of foods. Fruits, soft drinks, vinegar, and wines: acidic food. Meat, poultry, fish & shellfish: ph > 5. 6.
