Food Hygiene and Veterinary Public Health I

Food Hygiene and Veterinary Public Health I (VPHI)

• Course code: Vetm4141
• Year 4 DVM Students

Objectives of this Class

• Define veterinary public health
• Describe roles and responsibilities of public health veterinarians
• Define and differentiate different types of food contamination
• Define food from two perspectives

Introduction

• Veterinary public health (VPH) stems from veterinary medicine, encompassing comprehensive health for a wide range of species.
• Its ultimate aim is promoting human well-being, particularly in developing countries where close animal-human interaction is significant.
• VPH links agriculture and public health through veterinary medicine's contribution.
• VPH describes the concept and responsibility of veterinary medicine for public health.
• VPH is a component of public health, encompassing veterinary professional skills, knowledge, and resources for the protection and improvement of human health and nutrition. This involves controlling and preventing zoonotic diseases while lowering malnutrition and improving hygiene and sanitation.

Duties and Responsibilities of VPH Veterinarians

• In Animal Production and Health: Diagnosing and treating diseases in animals, preventing and controlling diseases, preventing job-related risks and diseases linked to live animals and their products, and managing quarantine stations to prevent livestock disease outbreaks.

• In Food Hygiene and Zoonoses: Ensuring food safety at all stages from farm/production to consumption via preventive and control measures for animal-originated diseases. This involves advising construction of food animal premises; inspections of facilities and products, including processing, storage, and distribution. This also includes investigating chemical and drug residues in food animals and cooperating with epidemiological services to control communicable diseases.

• In Environmental Health: Monitoring the disposal of dead animals and products to control zoonotic diseases of environmental origin. It also involves controlling disease vectors like insects and snails.

• In Biomedical Research: Developing better diagnostic tools, vaccines, and biological products. It entails ecological and epidemiological research on infectious diseases. Veterinary science is linked with comparative medicine and biological research in humans to evaluate medical treatments and vaccines.

Contamination of Food with Microorganisms

• Food, in a generalized sense, encompasses anything ingested (including drinks) by humans. In a veterinary context, it implies meat, meat products, milk, milk products, fish and fish products, eggs, and game (wild animals).
• Food can be processed, semi-processed, or raw. All contain protein, fat, and carbohydrates.
• Food safety ensures the food will cause no harm to the consumer.
• Wholesome food is sound, clean, free from adulteration (unacceptable substances), and suitable for human consumption.

Criteria of Food Safety and Hygiene

• Food should be healthy and palatable, attractive, free from decomposition and adulteration, free from other substances, nutritious, hygienic, and psychologically acceptable to the consumer.

Contamination of Food

• Food contamination arises from objectionable levels of organisms, chemicals, foreign bodies, taints, or unwanted, unhealthy, or decomposed material.
• Contamination can originate from a primary source (the animal) or a secondary source (contamination after slaughter).
• Primary contamination can involve microbial agents or chemical residues. Secondary contamination can arise from infected humans, other animals, or fomites (e.g., contaminated air, water, soil, or plants).

Microorganisms in Food

• Microorganisms in food can be categorized into wanted and unwanted. Unwanted ones can be further divided into spoiling and pathogenic varieties.

Objectives

• Differentiate between foodborne infection and intoxication.
• List foodborne infection and intoxication causing pathogens.
• List influencing factors in bacterial growth in food and explain their effect.
• Define food spoilage.
• Discuss the causes and signs of food spoilage.
• Describe methods for detecting food spoilage.

Foodborne Intoxication

• Food infection occurs from consuming food and viable microorganisms, whereas food intoxication involves ingesting preformed toxins produced by pathogenic microorganisms.
• Food poisoning due to ingesting preformed toxins is more detrimental than infection because even after cooking, the toxins remain resistant to heat inactivation.

Foodborne Infections

• Foodborne infection results from consuming food containing live pathogenic microorganisms.

Types of Microorganisms causing Foodborne Infections

• Bacteria (Salmonella, Streptococcus, Mycobacterium, Listeria, Brucella, Campylobacter, Anthrax, and others).
• Viruses (Infectious hepatitis, poliovirus, and others).
• Fungi (Ergot fungus, Aspergillus, poisonous mushrooms, and others).
• Parasites (Taenia, trichinosis, diphyllobothrium, and others).

Types of Contamination

• By Agent: Microbial (live agents like bacteria, fungi, viruses, and parasites) and non-microbial (chemical residues).
• By Time: Primary (arising directly from the food animal, e.g., infected animals) and secondary (originating from the environment, other animals, humans, or contaminated materials).

Types of Bacteria in Animal-Origin Food

• Psychrophiles (grow at low temps).
• Mesophiles (grow at room temperature).
• Thermophiles (grow at high temperatures).

Classification of Bacteria by Fermentation

• Homofermentative: Produce one product (e.g., lactic acid).
• Heterofermentative: Produce multiple products (e.g., CO2 and alcohol).

Effect of Microorganisms on Food

• Food spoilage modifies the nutritional value, texture, and flavor, making it unsuitable for consumption and often dangerous.
• Food degradation is a metabolic process primarily resulting in sensory changes.
• Food spoilage can emanate from microbial, enzymatic, physical, or chemical alterations.

Spoilage of Food by Microorganisms

• Proteolytic Spoilage: Proteolytic microorganisms degrade proteins into amino acids, generating foul odors (e.g., H2S and ammonia).
• Lipolytic Spoilage: Lipolytic microorganisms break down fats into fatty acids and glycerol, causing rancidity.
• Glycolytic Spoilage: Glycolytic microorganisms degrade carbohydrates, producing various byproducts (e.g., lactic acid, acetic acid, propionic acid, alcohol, CO2, and H2O).

Factors Influencing Bacterial Growth in Food

1. Intrinsic Parameters: Characteristics inherent to the food itself.

• pH: Most microorganisms thrive at neutral pH (around 7). Lower pH inhibits growth.
• Oxidation-Reduction Potential (ORP): Oxygen tension in the food affects microbial growth; aerobic and anaerobic microorganisms differ in their needs.
• Moisture Content/Water Activity: Microbes require water available for growth, and water activity measures this availability. Higher moisture content usually results in higher water activity.
• Nutrient Content: Water, energy sources (carbohydrates), nitrogen sources (amino acids), vitamins, and minerals.
• Antimicrobial Constituents: Naturally occurring substances (e.g., antibacterial agents) in the food that hinder microbial growth.
• Biological Structures: Natural barriers (e.g., hides, shells).

2. Extrinsic Parameters: Factors in the food's external environment.

• Temperature: Microbes have optimal growth temperatures (psychrophiles, mesophiles, and thermophiles).
• Relative Humidity: Moisture levels in the environment influence microbial growth in food.
• Gases: Presence and concentration of gases like oxygen (O2) and carbon dioxide (CO2) influence microbial growth.
• Presence/Activity of other Microorganisms: Microbes may antagonistically affect each other's growth.
• Additional parameters affecting microbial growth in food

Meat Quality and Production

• Meat Inspection/Hygiene: Detecting abnormalities/diseases in meat for wholesome and safe consumption. This involves quality, safety, and consumer acceptance.
• Carcass and Offal: Meat from the animal carcass, excluding non-meat parts (blood, feet, head, skin, viscera). Offal/by-products are often classified as edible and inedible parts and the inclusion as edible varies.
• Dressing Percentage (Carcass Yield): Ratio of the carcass weight compared to the animal's live weight (e.g., in cattle, a 53% yield).
• Meat Composition: The main constituents of lean beef meat are water (75%), protein (19%), non-protein nitrogen (1.65%), lipids (fatty acids) (2.5%), carbohydrates (glycogen) (1.2%), minerals (0.65%), and vitamins.
• Meat Proteins (Muscle Proteins): Myofibrils (contractile proteins), sarcoplasmic proteins (water-soluble proteins in the cytoplasm of muscle cells), and connective tissue proteins (Collagen, elastin, and reticulin–supporting muscle).
• Meat Lipids: Triglycerides, fats, oils, phospholipids, saturated, monounsaturated, polyunsaturated fatty acids, and cholesterol.
• Meat Carbohydrates: Primarily glycogen, profoundly influencing the post-mortem changes in muscle.
• Non-protein Nitrogen: Creatine, nucleotides, and inosine.
• Meat Minerals: Varied inorganic constituents crucial for animal function.
• Meat Vitamins: B vitamins, vitamin B1, B2, B3 or Niacin, B6 or pyridoxine, B12 , Pantothenic acid or vitamin B5, Folic acid, Biotin
• Meat species specification importance: Importance to quality control, safeguarding laws in different countries, and for meat quality detection/diagnosis in adulterated/substituted meat.
• Meat and Muscle Differences: Muscle is in the living animal, whereas meat results from post-mortem changes within the muscle.

Methods to Identify Meat Species

1. Physical Techniques: Examining color, texture, odor to ascertain meat species.
2. Anatomical Techniques: Analyzing dental formula and vertebrae/rib counts for animal identification.
3. Histological Techniques: Measuring and analyzing muscle fiber properties to ascertain species.
4. Chemical Techniques: Using chemical tests to determine differences in component levels, such as fat content, carotene proportion, linoleic acid levels, and glycogen levels of meats.
5. Biological Techniques: Using immunoassays or DNA-based methods (e.g., PCR) to identify specific species.

Contamination of Meat

• Endogenous: Infections from live animals (e.g., during infection) are ingested.
• Exogenous: Contamination occurs from factors in the environment/post-mortem stages in the slaughterhouse (e.g., during slaughter).

Sources of Contamination for Meat

• Outer Integuments: Hides, skins, hair, and feet.
• Gastrointestinal (GI) Contents: Stomach and intestines.
• Sticking Point Contamination: Contaminated blood vessels, resulting in meat contamination.
• Physical Contact: Personnel, premises, and equipment.
• Vermin (Pest): Rodents and insects.
• Chemical Contaminants: Chemical-based contamination (e.g., disinfectants or cleaning materials).

Signs of Meat Spoilage

• Changes in color (e.g., grey, yellow, or green).
• Shifts in consistency (stiffening).
• Unpleasant or repulsive odors (e.g., ammonia).
• Chemical changes (alkaline reaction due to ammonia formation).

Qualitative Changes in Meat

• Rigor Mortis: Post-mortem muscle stiffening resulting from the depletion of ATP (adenosine triphosphate) needed for muscle relaxation.
• Factors affecting Rigor Mortis: Temperature, animal stress levels, rate of cooling, etc.
• Pale, Soft, Exudative (PSE) Meat: Rapid onset of rigor mortis resulting in pale-colored, easily damaged meat.
• Dark, Firm, Dry (DFD) Meat: Slower onset of rigor mortis causing meat to display dark color, tough texture, and low moisture.

Slaughter Operations

• Methods of Slaughtering: Ritualistic and humane slaughter methods to ensure animal welfare.
• Stunning: Methods to render animals unconscious before slaughter (e.g., mechanical-captive bolt, electrical, chemical-carbon dioxide).
• Bleeding: Procedures to remove all blood from the carcass.
• Factors affecting bleeding efficiency: stunning methods, hauling time, time lag between stunning and bleeding, and animal health conditions.

Plant Sanitation

• Maintaining a hygienic environment in the slaughterhouse.
• Cleaning and disinfection of livestock vehicles, processing equipment, premises, and personnel.
• Important for preventing the transfer or spread of contagious diseases. A heavily contaminated hide or fleece will transmit much contamination to the carcass. Proper handling is necessary.

Ante-Mortem (AM) Examination

• Goal: Evaluating animals before slaughter to assess health and suitability. It's a precondition for good post-mortem examination results.
• Reasons for AME: Screening for health issues, separating diseased animals, reducing contamination, ensuring safety.
• Guidelines and Principles: Using well-lit areas, a precise record of the examination's results are of vital importance.
• Procedures of AME: Examination of the respiratory, digestive, behavior, structure and conformation, discharges, color, and odor.
• Judgement Categories of AME: Approved for slaughter (without restriction), condemned for slaughter, slaughter approved under special precautions, approval for delayed slaughter, and postponing or ordering emergency slaughter.