Food safety experts talk about a temperature "danger zone" where pathogenic bacteria grow best in food. Over which temperature range do most disease-causing bacteria multiply most rapidly?

Introduction / Context:
Foodborne illnesses occur when pathogenic bacteria grow to harmful levels in food before it is eaten. Temperature is a major factor controlling bacterial growth. Food safety guidelines often warn about a temperature "danger zone" in which bacteria multiply very quickly. Understanding this danger zone helps in storing, cooking, and cooling food correctly to reduce the risk of food poisoning. This question asks which temperature range best represents the conditions under which many pathogenic bacteria grow fastest in food.

Given Data / Assumptions:

• We are considering pathogenic bacteria that grow in common foods.
• Options list several temperature ranges in degrees Celsius.
• We assume typical mesophilic bacteria that infect humans, many of which have an optimum near body temperature (about 37 degrees Celsius).
• We also assume normal kitchen and storage conditions rather than extreme industrial environments.

Concept / Approach:
Most human pathogens are mesophiles, meaning they prefer moderate temperatures. Their optimum growth is often between 30 and 40 degrees Celsius, with many peaking close to 37 degrees Celsius. Food safety authorities describe a broader danger zone where bacteria can grow quickly, generally from about 5 or 7 degrees Celsius up to 60 degrees Celsius, but the middle of this range is where growth is fastest. The option 20 to 45 degrees Celsius covers the typical rapid growth zone, including the optimum around 37 degrees Celsius. Lower ranges like 5 to 15 degrees Celsius slow bacterial growth significantly, while very high ranges above 60 degrees Celsius tend to kill most pathogens rather than support growth.

Step-by-Step Solution:
Step 1: Recognise that most foodborne pathogens are adapted to grow at or near human body temperature, around 37 degrees Celsius. Step 2: Identify which option range includes this temperature and provides room on either side for rapid growth. Step 3: Note that 20 to 45 degrees Celsius includes 37 degrees Celsius and represents a moderate, warm environment suitable for fast bacterial multiplication. Step 4: Observe that 5 to 15 degrees Celsius is relatively cool and typically used for refrigeration, which slows growth. Step 5: Understand that −5 to 5 degrees Celsius (option E) includes freezing and near-freezing temperatures where growth is minimal. Step 6: Conclude that 20 to 45 degrees Celsius is the best answer for rapid growth of many pathogenic bacteria in food.

Verification / Alternative check:
Food safety guidelines often recommend keeping hot foods above about 60 degrees Celsius and cold foods below about 5 degrees Celsius, in order to stay out of the danger zone where bacteria grow rapidly. Guidance documents frequently state that the most rapid growth occurs roughly between 20 and 45 degrees Celsius, with many bacteria doubling in number every 20 minutes under ideal conditions. Restaurant and catering regulations typically focus on minimising the time food spends in this range. These practical rules confirm that 20 to 45 degrees Celsius is the key high-risk growth range.

Why Other Options Are Wrong:
Option A: 5 to 15 degrees Celsius is near refrigeration temperatures, which significantly slow bacterial growth and are used for safe storage. Option B: 15 to 25 degrees Celsius includes mild room temperatures where some growth occurs, but it does not fully cover the main optimum near 37 degrees Celsius. Option D: 40 to 65 degrees Celsius partly overlaps with the high end of bacterial growth, but above about 60 degrees Celsius many pathogens start to die rather than multiply. Option E: −5 to 5 degrees Celsius is near or below freezing, where growth is minimal and food can be preserved for longer periods.

Common Pitfalls:
Learners may assume that very hot temperatures always favour growth, forgetting that excessive heat actually kills microbes. Others might think that any temperature above refrigeration is equally risky. It is important to remember that bacteria have an optimum range, and for many human pathogens this sits around body temperature. The broad danger zone is often quoted as 5 to 60 degrees Celsius, but the fastest growth tends to occur in the central portion of this range, which is captured well by 20 to 45 degrees Celsius.

Final Answer:
Most pathogenic bacteria grow best and multiply most rapidly in food over the approximate range of 20 to 45 degrees Celsius.