Food spoilage is most commonly caused by bacteria, yeasts, and moulds because:[Fill in the blank]

Question

BlackTom AI · Accepted Answer

Microorganisms spoil food because they actively metabolise food components and are able to grow under normal storage conditions.

1. Relevant knowledge points and concepts
- Food spoilage = undesirable changes (odour, taste, texture, colour, gas, slime) produced by biochemical reactions.
- Bacteria, yeasts and moulds metabolise carbohydrates, proteins and lipids, producing acids, alcohols, gases, proteolytic and lipolytic breakdown products and pigments.
- Many spoilage organisms tolerate common storage stresses: psychrotrophs grow in refrigeration, xerophilic yeasts/moulds tolerate low water activity, acid‑tolerant species survive low pH, and facultative/anaerobic bacteria grow with low oxygen.

2. Step‑by‑step reasoning
- If microbes are present and conditions (temperature, pH, water activity, oxygen) permit, they use food components as substrates.
- Their metabolism produces volatile compounds (off‑odours), acids (souring), proteases (putrefaction; slime, bad taste), and gas (packaging swelling).
- Because microbes reproduce, spoilage progresses exponentially until organoleptic rejection, even at storage temperatures.

3. Intermediate steps / examples
- Refrigeration slows but does not stop psychrotrophic Pseudomonas or Listeria growth; spoilage still occurs.
- Low water activity in jams prevents most bacteria but certain yeasts and moulds grow and cause breakdown.
- Canning failures or anaerobic niches can still support anaerobic spoilage bacteria (gas, off‑odour).

4. Why the correct answer is correct
- Option D states they can metabolise food components and grow under storage conditions, directly explaining the mechanism (biochemical conversion + growth) by which spoilage occurs. This captures both activity and environmental adaptability.

5. Why the other options are incorrect
- A: Not all foods carry microbes and spoilage ≠ inevitable disease on consumption. Many spoiled foods are not pathogenic.
- B: Spoilage is not only after packaging oxygen ingress; many organisms grow in low or no oxygen and some spoil in sealed packages.
- C: Endogenous enzymes also cause deterioration, and microorganisms are not universally more resistant to preservation processes than enzymes; this statement is misleading.

6. Conclusion
Therefore the correct answer is D. This matches the provided answer: D. They can metabolise food components and grow under storage conditions.

Food spoilage is most commonly caused by bacteria, yeasts, and moulds because:[Fill in the blank]单项选择题

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