Food Safety and Foodborne Disease ENVR 191 Food Safety and Foodborne Disease Lecture 2 - December 6, 1999 Mark D. Sobsey

Hazard Analysis/Critical Control Points (HACCP) A program of process control to (1) identify microbial hazards, (2) identify the most vulnerable (critical) sites or steps in the process and (3) implement an in‑house monitoring system for quality assurance and hygiene. Incorporates elements of: (i) education and training, (ii) ingredient or commodity control, (iii) process control, (iv) inspection, and (iv) microbiological and related surveys Design and implement on a commodity-specific and production facility-specific basis

Methods to Control Fecal Contamination of Foods Prevention: keep enteric microbes out Remove enteric microbes: identify and remove contaminated food items and ingredients wash to remove contaminants filtration or other physical separation methods depurate or relay live shellfish. Use of heat sterilize disinfect (e.g., pasteurize and cook to destroy pathogens Use of cold and freezing cold storage and freezing to prevent proliferation Drying, dehydration and intermediate-moisture processing Chemical treatments: disinfect and sanitize Irradiation: UV and gamma (ionizing) radiation

Heat and Thermal Treatment Effects of heat vary with: food composition: water, fat, proteins, carbohydrates, salts and pH organism factors: form, composition, growth stage, age, etc. Sterilize (or nearly sterilize) foods (destroys all viable microbes) Heat >100oC; usually uses high pressure and steam; Typical target temperature is 115‑116oC for about 60 minutes. Example: Retorting of Canned Foods. Pasteurization: Intended to kill pathogens; Does not sterilize the food; Often used prior to subsequent cold storage so pathogens or spoilage organisms do not proliferate. High Temperature‑Short Time Method: 72oC; 15 sec. (milk) Low Temperature‑Long Time Method: 62.8oC for 30 min.(milk) Pasteurization times and temperatures for other foods depend on the effects of heat on the food, food composition and the target organisms of interest.

Thermal Destruction of Microbes: Thermal Death Time and D Value Thermal Death Time (TDT): time needed to kill a specified number of organisms at a specified temperature. D value: time needed to destroy 90% or 1 log10 of organisms at a specified temperature Assumes first-order (exponential; log-linear) destruction kinetics 100----- Survivors (%) 10------------------- 1-- D value Time (min.)

Drying, Dehydration and Desiccation Low moisture foods: usually <15% moisture Intermediate moisture foods (IMF): 15-50% moisture fruits, cakes, syrups, candies, jams, milks, some meats and cheeses Sun (natural) drying: often used for fruits Heat drying (dehydration; desiccation) Freeze drying (lyophilization; cryophilization) Condensing or evaporating: reducing moisture in a liquid food; e.g., evaporated or sweetened condensed milk. Drying destroys some enteric microbes but is not very effective for others. Inhibitors are often used for dried and IMF foods: ex.: potassium sorbate and calcium propionate as fungistats

Chemical Treatments Preservatives: Disinfectants and sanitizers: Most are ineffective against viruses and protozoan cysts most are designed to control certain bacteria and molds. propionates, sorbates, benzoates and p‑hydroxybenzoates: molds Nitrates and nitrites (ex., for Clostridia.) Sulfur dioxide and sulfites Acetic, lactic and other organic acids NaCl and sugars Ethylene and propylene oxides Disinfectants and sanitizers: Used to treat (by washing or dipping) certain meats and produce Chlorine, peroxyacetic acid, ozone, hydrogen peroxide 10s to 100s of mg/l; contact times of seconds to minutes Organic acids (acetic, lactic and citric) at 2-7%; less effective

Food Irradiation Ionizing Radiation (X‑rays and gamma rays) Becoming more widely used. Gamma radiation from Co-60 and Cs-137 sources) Effectiveness depends on: organism, composition of the food, temperature, and presence of oxygen Undesirable changes in foods from excessive radiation: radiolysis of water and other chemical reactions on amino acids, etc.. Doses(approximate) to inactivate 1 log10 of organisms: vegetative bacteria: 100‑200 Krad viruses: 500 Krad Cysts and Spores: 500 Krad UV Radiation: Low (monochromatic 254 nm) mad medium (polychromatic) Used primarily for beverages: water, juices, ciders, etc.

Shellfish Depuration and Relaying Place live bivalve mollusks shellfish in clean flowing seawater Normal pumping, feeding and related activity rids accumulated microbes Relaying: transfer shellfish from contaminated (restricted) waters to uncontaminated natural estuarine waters. Typical holding times in the clean water are two weeks or longer. Depuration: Place restricted shellfish in shore‑based tanks of clean, flowing seawater under controlled conditions for periods of several days Factors influencing deputation efficiency: tank geometry and loading (quantity of shellfish per volume of tank), water quality temperature

Factors Influencing Uptake and Persistence of Enteric Microbes in Shellfish Type of microbe: viruses are more persistent than bacteria Type of shellfish: differences among shellfish species and genera Temperature: uptake and persistence greater at higher temperature (to a limit); at very low and very high temperature, the animals become inactive and do not pump water Salinity: uptake and persistence greater at higher salinity. If salinity is low they become inactive and not pump water. Turbidity: excess causes gill clogging and interferes with activity. Higher turbidity increases microbial uptake but does not greatly influence elimination (except for some enteric bacteria). Dissolved oxygen: animals become inactive (suffocate at low DO). pH: in he physiological has little influence on uptake or elimination) Other water quality factors: toxic chemicals can interfere with activity Food supply: little direct effect if it does not change pumping activity Spawning reduces microbial elimination from shellfish.