Control of Foodborne Disease

Today

• Review of classes of food-borne disease, types of contamination, sources and factors affecting growth

• HACCP

• Types of controls– Physical Methods– Chemical Methods– Biological Methods

Classes of Food-borne Disease

• Infection– Foodhandler– Food Concentration – Direct Contamination– Water-washed

• Toxico-infection• Intoxication (food poisoning)

– Bacterial and Fungal Toxins– Shellfish Toxins– Metals, Chemicals, etc.

• Allergy

Types of Contamination

• Viral

• Bacterial– Cells– Products

• Fungi– Products

• Protozoa and Helminths

• Other (Cyanobacteria??)

Microbial Growth in Food

• Bacteria and Fungi

• Complex Ecology– Interaction with multiple environmental factors

controls whether an organism can grow in a given environment

• Food Preservation– Ecology of zero growth

Microbial Growth in Food

• Intrinsic Factors:– pH– Water Activity– Salt Concentration– Nutrients– Etc.

• Extrinsic Factors– Temperature– Gaseous Conditions– Presence of Other

Microbes

Heterogeneity

- Question of scale

- Food items may have several distinct microenvironments

HACCP

• Hazard Analysis and Critical Control Point– Framework to identify risks and control hazards

• Preliminary steps– Gain management support– Assemble HACCP team– Describe the food and method of distribution– Identify the intended use and consumers– Develop a flow diagram– Verify the flow diagram

• Establish plan-specific objectives and performance criteria

7 Principles of HACCP

1) Conduct a Hazard Analysisa. Hazard identificationb. Hazard evaluationc. Identification of control measuresd. Determine influence of prerequisite

programs

2) Determine the Critical Control Pointsa. Consideration for product typeb. Use of decision trees

7 Principles of HACCP

3) Establish Critical Limitsa. Defined as “ a maximum or minimum value

to which a biological, chemical, or physical parameter must be controlled at the CCP to prevent, eliminate, or reduce to an acceptable level the occurrence of a significant food safety hazard

b. Typically process based rather than microbiological

7 Principles of HACCP

4) Establish Monitoring Proceduresa. What is being monitoredb. How oftenc. Procedures to collect datad. Responsibility

5) Establish Corrective Actionsa. Fix or correct problemb. Determine disposition of productc. Re-evaluate HACCP plan

7 Principles of HACCP

6) Establish Verification Processa. Methods, procedures, and/or tests used to

verify compliance to HACCP plan in addition to monitoring

b. Essentially QA/QC

7) Establish Record-Keeping and Documentation Procedures

a. HACCP Plan and supporting documentationb. Records obtained during operation of plan

Control of Food-borne Microbes

• Poor- No control over food production, distribution, or consumption

• Good- Prevent degradation of product by control of shelf-life and environmental factors

• Better- Chemical, Physical or Biological Treatment

• BEST- PREVENT CONTAMINATION

Physical Controls

• Water Activity– Dehydration

• Drying- air• Freeze-Drying (vacuum sublimation of ice content)

– Minimal aw needed for growth• Bacteria 0.91-0.88• Yeasts 0.88• Molds 0.80• Halophilic bacteria 0.75• Xerotolerant molds 0.71• Xerotphilic molds and osmophilic yeasts 0.62-0.60

Physical Controls

• Temperature Controls– Cool Storage (4-12ºC)

• Controlled-Atmosphere Storage• MAP/VP

– Freezing and Frozen Storage (-15 to -40ºC)– Heat Treatments

• Autoclaving• Dry Heat Sterilization• Pasteurization/Flash Pasteurization• Tyndalization• Microwave heating• Ohmic Heating

Physical controls

• Ultrasound– Synergy with heat

• Irradiation– UV Radiation– High-Intensity Pulsed Light

• Xenon lamps– Ionizing Radiation

• Gamma• E-Beam

• Hydrostatic Pressure• Electric Field Effects• Magnetic Field Effects

Chemical Controls

• Organic Acids and Esters– E.g. acetic, lactic, propionic, sorbic, benzoic– Related to pH (used in foods with pH<5.5)

• Dimethyl Dicarbonate– Highly reactive with wide range of compounds – Primarily targeted at yeasts, but also bacteriocidal– Inactivates enzymes

• Lysozyme– Targets peptidoglygan causing hydrolysis– Egg albumin– Increased effectiveness with pretreatment chelators

Chemical Controls

• Nitrites– Particularly good against C. botulinum– Inactivates enzymes; better under anaerobic

conditions, and low pH

• Parabens– Antimicrobial activity related to length of chain– Better against molds and yeast than bacteria; but more

effective against Gram + than Gram –– Inhibit nutrient uptake (e.g. amino acids line serine)

Chemical Controls

• Phenolic Antioxidants– E.g. BHA, BHT, propyl gallate, and TBHQ– Function: Delays auto-oxidation of

unsaturated lipids• Interupts free-radical chain mechanism of

hydroperoxide formation

– Similar antimicrobial mechanism to Parabens and other phenolics; higher levels required

Chemical Controls

• Phosphates– E.g. sodium acid pyrophosphate (SAPP),

TSPP, STPP, SHMP, TSP– Gram + more susceptible than Gram –– Mechanism: metal chelation

• Inhibits cell division– Interference with Mg2+-dependent enzyme.

• Salt (NaCl)– Water activity

Chemical Controls

• Sulfites and Sulfur salts– Targets spoilage and fermentative yeasts,

molds, acetic acid bacteria, and malolactic bacteria

– Act as antioxidants; inhibit enzymatic activities

Natural Chemical Compounds

• Lactoperoxidase System– Enzyme in milk– Better against Gram –

• Lactoferrin and Other Iron Binding Proteins

• Avidin (glycoprotein in egg albumin)– Binds biotin (a co-factor for enzymes)

• Spices and Oils• Phenolics

Biological Controls

• Controlled Acidification– E.g. lactobacilli and lactococcal bacteria

• Bacteriocins– E.g. Nisin (temp-dependent)