Lesson 5 Flashcards
What are the different categories of bacteria based on their effects on humans?
Bacteria are classified into four categories based on their effects on humans: pathogenic bacteria (disease-causing), undesirable bacteria (cause decomposition of food), beneficial bacteria (used in food production), and benign bacteria (neither helpful nor harmful).
What are pathogenic bacteria and how do they affect food safety?
Pathogenic bacteria are harmful, disease-causing bacteria that cannot be seen, smelled, or tasted in food. They cause food-borne illnesses without altering the food’s appearance, taste, or smell, making it difficult to detect contaminated food.
What are undesirable bacteria and how can they be identified in food?
Undesirable bacteria cause the decomposition of food, leading to spoilage. They can be identified by changes in the color, taste, odor, and texture of the food. Spoiled food is not typically a cause of food-borne illness and is usually easy to identify and avoid.
What are beneficial bacteria and how are they used in food production?
Beneficial bacteria are used in the production of various foods such as cultured milk, yogurt, cheese, and sauerkraut. They play a positive role in food fermentation and preservation processes.
What are benign bacteria?
Benign bacteria are neither helpful nor harmful to humans. Most bacteria fall into this category.
What are spores and how do they relate to bacteria?
Spores are a protective form some bacteria take under adverse conditions. During this dormant stage, bacteria do not reproduce but can survive harsh conditions. Once conditions become favorable, spores return to their vegetative state and resume growth. Spore-forming bacteria are difficult to destroy and include pathogens like tetanus, anthrax, and botulism.
How do bacteria reproduce and what is binary fission?
Bacteria reproduce by a process called binary fission, where one bacterium splits into two. This process results in exponential growth, with numbers doubling approximately every 20 to 30 minutes under ideal conditions.
What is the log phase in bacterial growth?
The log phase is the period of rapid bacterial growth under ideal conditions. Bacteria initially adjust to their environment in a resting (lag) phase, then enter the log phase of rapid growth, followed by stationary and death phases as nutrients deplete and waste products accumulate.
What conditions are necessary for bacterial growth?
Bacterial growth requires six conditions, summarized by the acronym FATTOM: Food (nutrients), Acidity (pH level), Temperature, Time, Oxygen, and Moisture. Controlling these conditions can help manage bacterial growth.
How does acidity affect bacterial growth?
Bacteria generally prefer neutral or low-acid foods. Foods with high acidity deter bacterial growth. Foods with a pH value of 4.6 or less are too acidic for bacteria to grow, making them safer. Vinegar, for example, is used as a preservative due to its high acidity.
What temperatures favor bacterial growth, and what is the Temperature Danger Zone?
Bacteria that cause diseases in humans grow most rapidly between 41°F and 140°F, known as the Temperature Danger Zone. Psychrophilic bacteria grow below 50°F, mesophilic bacteria thrive between 50°F and 110°F, and thermophilic bacteria grow best between 110°F and 150°F. To control bacterial growth, potentially hazardous foods should be kept cold at 41°F or less or hot at 140°F or more.
Why is time important in bacterial growth and how can it be managed?
Bacteria need time to grow and multiply. When conditions are favorable, their numbers can double every 20 to 30 minutes. Minimizing the time food spends in the Temperature Danger Zone is crucial. Batch preparation is a useful technique to reduce exposure time by only removing small quantities of food from refrigeration at a time.
What role does oxygen play in bacterial growth?
Some bacteria, called aerobes, require oxygen to grow, while anaerobes thrive without oxygen. Facultative bacteria can grow with or without oxygen. Managing oxygen exposure can help control bacterial growth.
Why is moisture important for bacterial survival and how can it be controlled?
Bacteria need moisture to absorb food through their cell walls. Removing moisture from food through dehydration, smoking, freezing, or preserving with salt or sugar can control bacterial growth. Foods with low water activity, such as dried rice and powdered milk, have a longer shelf life and are safer.
What is water activity and how does it affect bacterial growth?
Water activity measures the amount of water available in food for biological activity. Foods with a water activity value of 0.85 or less do not have enough moisture to support bacterial growth, making them safer and more shelf-stable. Low water activity increases food safety and shelf life.
