STM3183 Low pH and Organic Acids

What is the optimal pH range for most bacteria to grow?

• 6.0 to 8.0

• 6.8 to 7.5

• 4.0 to 6.0

• 4.0 to 8.0

Which of the following acids is considered a weak acid?

• Hydrochloric acid

• Citric acid

• Sulfuric acid

• Nitric acid

Which microorganism can grow at a pH lower than 2.0?

• All of the above

• Bacteria

• Yeast

• Moulds

What happens to microbial cells when subjected to extreme pH?

• They multiply

• They die

• They are inhibited

• They thrive

What is the minimum pH for Salmonella growth when using hydrochloric acid?

• 4.30

• 4.05

• 4.40

• 4.10

What is the effect of weak acids on microbial cells?

• They have no effect

• They can lower cytoplasmic pH

• They fully dissociate in the cytoplasm

• They cannot penetrate the cell membrane

Which of the following is a characteristic of strong acids?

• Lipophilic

• Weak

• Fully dissociated

• Partially dissociated

What is the primary mechanism by which strong acids affect microbial cells?

• They promote growth

• They enhance enzyme activity

• They damage cell membranes

• They increase nutrient uptake

What is the role of lactic acid in food preservation?

• Effective against all microorganisms

• Inhibits spore-forming bacteria

• Promotes yeast growth

• Has no effect

Which of the following acids is most effective against moulds in bakery products?

• Acetic acid

• Propionic acid

• Lactic acid

• Benzoic acid