Lesson Notes By Weeks and Term v3 - Senior Secondary 3
Food Hygene, Preservation and Storage
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Food Hygene, Preservation and Storage
Download the Lessonotes Mobile Nigeria 2025 app for faster lesson access on Android and iPhone.
Subject: Health Education
Class: Senior Secondary 3
Term: 1st Term
Week: 5
Theme: Food And Nutrition
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explain food hygene list agent that can cause food poisoning list ways of preserving and storing food
through contaminated food or water, often by infected food handlers.
3. Parasites: These are organisms that live on or in a host and get their food from or at the expense of their host.
Examples: Giardia lamblia: Found in contaminated water and uncooked food. Causes diarrhea, abdominal cramps.
Ascaris lumbricoides (Roundworm): Eggs can be in soil and contaminate vegetables. Causes malnutrition and intestinal blockage.
Taenia solium (Pork tapeworm): From undercooked pork.
4. Toxins: These are poisonous substances produced by microorganisms, plants, or animals, or chemical contaminants.
Examples: Bacterial Toxins: Produced by bacteria like Staphylococcus aureus or Clostridium botulinum (causes botulism, rare but severe).
Natural Toxins: Found naturally in certain foods (e.g., aflatoxins in poorly stored groundnuts/maize, cassava with high cyanide content if not properly processed, certain wild mushrooms, pufferfish).
Chemical Contaminants: Pesticides, cleaning agents, heavy metals (e.g., lead from inappropriate cooking utensils or containers) accidentally contaminating food.
Nigerian Context for Food Poisoning: Unhygienic Street Food: Many cases linked to improperly handled akara, moi-moi, suya, or mama put meals.
Contaminated Water: Use of unsafe water for washing food or cooking can introduce pathogens.
Improper Storage: Cooked food left at room temperature for too long in Nigeria's hot climate allows rapid bacterial growth.
Aflatoxins: A significant concern in poorly stored staples like maize, groundnuts, and millet, especially during humid conditions. 2.
3. Food Preservation and Storage Food preservation involves processes that prevent or slow down food spoilage and maintain the nutritional value, texture, and flavour of food. Food storage refers to keeping food in appropriate conditions to maintain its quality and safety.
Reasons for Food Preservation: To extend the shelf life of food items. To maintain the nutritional content and quality of food. To ensure food availability during off-seasons (food security). To reduce food waste and economic losses. To prepare food for transportation or export.
Methods of Food Preservation:
A. Traditional/Common Methods in Nigeria:
1. Drying (Dehydration): Removes moisture from food, inhibiting microbial growth and enzyme activity.
Examples: Sun-drying fish (panla, eja kika), meat, vegetables (e.g., ugu, okro), yam flour (elubo isu), cassava flour (garri, fufu), pepper, corn, beans.
Principle: Microorganisms need water to grow. Removing water makes the environment unsuitable for them.
2. Salting: Adds salt to food, which draws out moisture (osmosis) and inhibits microbial growth.
Examples: Salting fish, meat (e.g., dried beef/kilishi).
Principle: High salt concentration dehydrates microbial cells and alters their environment.
3. Smoking: Uses smoke from burning wood to impart flavour, dry the food, and introduce antimicrobial compounds from the smoke.
Examples: Smoking fish (eja yiyan), meat (bushmeat), chicken.
Principle: Combination of drying, heat, and chemical compounds in smoke that inhibit microbial growth.
4. Fermentation: Uses beneficial microorganisms (bacteria, yeast, mould) to convert sugars into acids, alcohol, or gases, which preserve the food and often enhance flavour and nutrition.
Examples: Fermenting cassava for garri, fufu, or akpu; soybeans for ogiri; melon seeds for ogiri okpei; milk for nunu (yoghurt-like drink).
Principle: The acidic environment created by fermentation inhibits the growth of spoilage and pathogenic microorganisms.
5. Use of Spices/Herbs: Some spices (e.g., garlic, ginger, pepper) have natural antimicrobial properties that can help extend food shelf life.
6. Underground Storage/Cool Cellars: For root crops like yams and potatoes, storing them in cool, dark, well-ventilated earthen barns or pits helps to reduce spoilage by slowing down respiration and sprouting.
7. Oil Coating: Coating certain items like eggs with a thin layer of oil can help seal pores and reduce moisture loss and entry of microbes.
B. Modern/Accessible Methods:
1. Refrigeration: Storing food at low temperatures (0-5°C) slows down microbial growth and enzyme activity.
Examples: Storing cooked stews, soups, leftovers, fresh meat, vegetables, fruits, dairy products.
Principle: Low temperatures inhibit the rapid multiplication of most spoilage microorganisms.
2. Freezing: Storing food at very low temperatures (-18°C or below) stops microbial growth and greatly slows down enzyme activity.
Examples: Freezing meat, fish, poultry, vegetables, fruits, pre-cooked meals. * Principle: The low temperature freezes the water in food, making it unavailable for microbial growth and enzyme activity.
B. Modern/Accessible Methods:
1. Refrigeration: Storing food at low temperatures (0-5°C) slows down microbial growth and enzyme activity.
Examples: Storing cooked stews, soups, leftovers, fresh meat, vegetables, fruits, dairy products.
Principle: Low temperatures inhibit the rapid multiplication of most spoilage microorganisms.
2. Freezing: Storing food at very low temperatures (-18°C or below) stops microbial growth and greatly slows down enzyme activity.
Examples: Freezing meat, fish, poultry, vegetables, fruits, pre-cooked meals.
Principle: The low temperature freezes the water in food, making it unavailable for microbial growth and enzyme activity.
3. Canning: Sealing food in airtight containers and heating them to kill microorganisms and create a vacuum. (More industrial, less common at household level in Nigeria).
4. Pasteurization: Heating liquid foods (e.g., milk, juice) to a specific temperature for a set time to kill pathogens, then rapidly cooling.
5. Vacuum Sealing: Removing air from packaging to reduce oxidation and inhibit the growth of aerobic microorganisms.
Food Storage Practices: Airtight Containers: Protect food from moisture, pests, and cross-contamination (e.g., for grains, beans, flours). Cool, Dry, Dark Place: Ideal for non-perishable items like root crops (yam, potatoes), grains, and spices.
Proper Labelling: Date and label stored foods to ensure "First In, First Out" (FIFO) rotation, especially in refrigerators.
Separation: Raw and cooked foods should always be stored separately. Specific Storage for Yam and Beans (as per Evaluation Guide): Yam: Whole Yam: Store in a cool, dry, dark, and well-ventilated place. Traditional methods involve stacking on wooden platforms or shelves in barns (e.g., chi in Igbo culture), ensuring air circulation to prevent rot and sprouting. Avoid direct sunlight.
Yam Flour (Elubo Isu): Store in airtight containers in a cool, dry place to prevent moisture absorption and pest infestation.
Beans: Dried Beans: Store in airtight containers (e.g., plastic bins, jars) in a cool, dry place away from direct sunlight. This prevents moisture absorption, insect infestation (weevils), and mould growth. Adding dry pepper or dried neem leaves can deter pests.
Bean Flour: Store in airtight containers in a cool, dry place. This section provides detailed explanations of the core concepts related to food hygiene, food poisoning agents, and food preservation/storage. 2.
1. Food Hygiene Food hygiene refers to all conditions and measures necessary to ensure the safety and suitability of food at all stages of the food chain, from production to consumption. Its primary goal is to prevent food contamination and foodborne illnesses.
Key Principles of Food Hygiene: Cleanliness: Personal Hygiene: Regular hand washing with soap and water before, during, and after handling food. Covering cuts and wounds on hands. Wearing clean clothing. Avoiding coughing or sneezing over food.
Kitchen and Utensil Hygiene: Regular cleaning and sanitizing of work surfaces, chopping boards, knives, and cooking utensils. Using separate chopping boards for raw and cooked foods.
Food Cleanliness: Washing fruits and vegetables thoroughly under running water, especially those eaten raw or bought from open markets (e.g., garden eggs, tomatoes, ugu leaves).
Separation of Raw and Cooked Food: Raw foods (e.g., raw meat, poultry, seafood, unwashed vegetables) can contain harmful microorganisms that can transfer to cooked foods. Store raw foods below cooked or ready-to-eat foods in the refrigerator to prevent drips. Use separate utensils and chopping boards for raw and cooked foods, or wash them thoroughly in between uses.
Cooking Thoroughly: Proper cooking kills most harmful bacteria and viruses. Ensure food reaches a safe internal temperature (e.g., meats, poultry, eggs). For example, ensuring stews, soups, and rice dishes are fully heated through, not just warmed. Reheat leftovers to boiling point (or at least 74°C/165°F).
Keeping Food at Safe Temperatures: Hot Holding: Keep hot food hot (above 60°C/140°F) until served. This inhibits bacterial growth.
Example: Keeping jollof rice or stew warm on a low heat or in a warm server.
Cold Holding/Refrigeration: Keep cold food cold (at or below 5°C/40°F). Refrigeration slows down microbial growth.
Rapid Cooling: Cool cooked food rapidly before refrigerating (within 2 hours). Divide large portions into smaller, shallow containers to speed up cooling. 2.
2. Agents that Cause Food Poisoning Food poisoning is an illness caused by consuming food contaminated with harmful bacteria, viruses, parasites, or toxins.
Common Agents:
1. Bacteria: These are microscopic living organisms that can multiply rapidly in food, especially at room temperature.
Examples: Salmonella: Commonly found in raw poultry, eggs, unpasteurized milk, and contaminated water. Can cause fever, diarrhea, abdominal cramps. Escherichia coli (E. coli): Certain strains (e.g., E. coli O157:H7) are found in undercooked ground beef, unpasteurized milk, contaminated water, and fresh produce. Can cause severe abdominal cramps, bloody diarrhea, and kidney failure.
Staphylococcus aureus: Carried on the skin, nose, and throat of healthy individuals. Can contaminate food through improper handling (e.g., by a cook with a cut). Produces toxins that are not destroyed by cooking and cause rapid onset of nausea, vomiting, and cramps. Common in pastries, salads, cooked meats.
Clostridium perfringens: Often found in meat and poultry, especially large portions of food left to cool slowly. Causes abdominal pain and diarrhea.
Listeria monocytogenes: Can grow in refrigerated temperatures. Found in soft cheeses, deli meats, unpasteurized milk. Dangerous for pregnant women, newborns, and immunocompromised individuals.
Vibrio cholerae: Causes cholera, often associated with contaminated water and seafood, or food prepared with contaminated water.
2. Viruses: These are infectious agents that require a host to multiply. They are often spread through the fecal-oral route, typically from an infected food handler.
Examples: Norovirus: Highly contagious, causes gastroenteritis (vomiting, diarrhea). Commonly spread by infected food handlers or contaminated surfaces.
Hepatitis A: Can cause liver inflammation. Spread through contaminated food or water, often by infected food handlers.
3. Parasites: These are organisms that live on or in a host and get their food from or at the expense of their host.
Examples: Giardia lamblia: Found in contaminated water and uncooked food. Causes diarrhea, abdominal cramps.
Ascaris lumbricoides (Roundworm): Eggs can be in soil and contaminate vegetables. Causes malnutrition and intestinal blockage.
Taenia solium (Pork tapeworm): From undercooked pork.
4. Toxins: These are poisonous substances produced by microorganisms, plants, or animals, or chemical contaminants. *
Examples: Teacher Activities: Introduction (10 minutes): Initiate a discussion by asking students about their personal experiences with food spoilage at home or illness after eating certain foods. Project images of spoiled food, food poisoning symptoms, and well-preserved foods (e.g., smoked fish, dried yam slices). Briefly introduce the topic, linking these experiences to the importance of food hygiene, preservation, and storage. State the performance objectives for the lesson.
Explanation of Food Hygiene (15 minutes): Define food hygiene using clear, simple language. Explain the four key principles of food hygiene (cleanliness, separation, thorough cooking, safe temperatures) with vivid Nigerian examples (e.g., handwashing before preparing eba, using different cutting boards for raw chicken and vegetables for egusi soup, ensuring jollof rice is cooked through). Facilitate a short Q&A session. Explanation of Agents Causing Food Poisoning (15 minutes): Define food poisoning. Categorize and explain the main agents (bacteria, viruses, parasites, toxins) with examples relevant to common Nigerian foods and practices (e.g., Salmonella from undercooked eggs, E. coli from contaminated water, aflatoxins in groundnuts). Discuss typical symptoms associated with food poisoning. Show visuals of contaminated foods or environments (e.g., flies on uncovered food, dirty market stalls). Explanation of Food Preservation and Storage (20 minutes): Define food preservation and storage, explaining their importance. Present various methods of food preservation, categorizing them into traditional/common in Nigeria and modern/accessible methods. For each method, explain the underlying principle (e.g., drying removes moisture, refrigeration slows growth). Provide concrete Nigerian examples for each method (e.g., sun-drying panla, smoking catfish, fermenting cassava for garri, storing yams in a barn, refrigerating stew). Specifically discuss the preservation and storage of yam (whole and flour) and beans (dried). Use charts or diagrams illustrating different preservation techniques. Practical Discussion/Demonstration (15 minutes): Bring in small samples of traditionally preserved foods (e.g., a piece of dried fish, dried yam flour, a small packet of well-stored beans). If actual samples are unavailable, use high-quality images.* Lead a discussion on how these foods are preserved and stored, relating to the explanations provided. Conduct a brief mock demonstration of proper handwashing technique or the proper way to cover cooked food.
Conclusion & Assignment (5 minutes): Summarize key takeaways. Assign independent practice questions.
Student Activities: Brainstorming/Discussion: Students share experiences regarding food safety and spoilage.
Note-taking: Actively take notes during teacher explanations.
Q&A: Ask questions for clarification.
Group Discussion (if time permits): In small groups, students discuss: "How do families in their community ensure food safety during local festivals?" "What are common unhygienic practices observed in local food markets/restaurants and how can they be improved?" Observation: Examine samples of preserved foods (if provided) and discuss the methods used.
Mock Demonstration: Participate in or observe mock demonstrations of food hygiene practices.
Community Health and Disease Prevention: Understanding food hygiene is crucial in preventing common foodborne diseases like cholera and typhoid, which are prevalent in many Nigerian communities. For instance, proper washing of fruits and vegetables before consumption, especially those bought from open markets, significantly reduces the risk of consuming contaminated food. Knowledge of safe street food practices helps individuals make healthier choices, impacting community-wide health outcomes.
Household Economy and Food Security: By applying food preservation and storage techniques, Nigerian households can significantly reduce food waste, especially during peak harvest seasons or when electricity supply is erratic. For example, drying excess tomatoes, okra, or pepper prevents spoilage and ensures availability during lean seasons, contributing to household food security and saving money that would otherwise be spent on repurchasing fresh produce. This also supports the "zero hunger" goal. Entrepreneurship and Small-Scale Food Processing: Knowledge of food preservation techniques is fundamental for small-scale entrepreneurs in Nigeria involved in food processing. For example, local businesses producing yam flour (elubo), dried fish (eja kika), smoked meat (kilishi), or packaged garri rely on these methods to extend the shelf life of their products, ensure quality, and access wider markets, thereby stimulating local economies and creating employment opportunities.