Milk.One of Mother Nature s Most Perfect Foods Why Bacteria in Milk Matters SP Oliver Dept. Animal Science The University of Tennessee http://www.tqml.utk.edu soliver@utk.edu got milk? Milk Quality Topic of continued debate in dairy industry Issues. public health (residues, pathogens, toxins) processors & consumers demanding high quality Several groups support enhancing milk quality (lower SCC & bacteria counts) via regulatory intervention. Milk buyers/processors may only purchase high quality milk even though milk meets minimum regulatory standards Quality Milk Low SCC Low bacterial count Free of human pathogens Free of antibiotic residues Bacteria in Milk Regulatory limit defined. < 5,/ml in in Ontario. 1,/ml in in US. Safety concerns. Some pathogens in in milk can cause disease in in humans Quality concerns. Impacts taste, shelf-life, life, alter milk composition, yield High milk bacteria count associated with mastitis- causing bacteria, poor hygiene & sanitation, improper milk cooling, environmental contamination.
Bacteria Found in Milk Mastitis pathogens Psychrotrophic cold tolerant bacteria Thermoduric spoilage bacteria Foodborne pathogens Bacteria & Milk Quality Milk Is Pasteurized. So What s s the Concern? Reduced quality of raw & processed milk & milk products associated with psychrotrophic bacteria & thermoduric spoilage bacteria Most destroyed by pasteurization.some produce proteolytic & lipolytic enzymes that survive pasteurization These enzymes degrade protein & fat in raw & processed products.reduce shelf-life life & alter taste Quality & Shelf Life of Pasteurized Fluid Milk Most Most significant cause milk shelf-life. life. Gram- neg psychrotrophic bacteria.these bacteria generally do not survive pasteurization Post-pasteurization contamination with Gram-neg psychrotrophic bacteria which can grow at at refrigeration temperatures significant cause of milk shelf-life life Certain Certain bacteria (spore-forming strains of Bacillus & Paenibacillus) that survive pasteurization can grow at at refrigeration temperatures & cause spoilage of milk beyond 14 days post-processing processing Escherichia coli, Citrobacter fruendii, Klebsiella spp, Enterobacter spp. Acinetobacter, Hafnia alvei, Moraxella, P. aeruginosa, P. fluorescens, Non Non coliforms Pseudomonas spp., Bacillus Streptococci spp., Serratia spp. S. salivarius, S. bovis, S. equinus, Enterococci S. uberis, E. faecalis, E. faecium. E. avium, E. durans, E. malodoratus, S. thermophilus Manure Escherichia coli, Citrobacter fruendii, Klebsiella spp, Pseudomonas Moraxella, P. P. fluorescens, Streptococci spp., Bacillus Serratia Enterococci spp. Bacillus Soil Soil Enterobacter spp. Acinetobacter, Hafnia alvei, Moraxella aeruginosa, P. fluorescens Pseudomonas spp., spp., Serratia spp.,, S. bovis, S. uberis, E. faecalis, E. faecium. E. avium Coagulase neg. Staphylococci, S. bovis, S. uberis, E. faecalis, E. faecium, E. avium, Escherichia coli, Citrobacter fruendii, Klebsiella spp, Enterobacter spp. Pseudomonas spp. Bacillus spp. Non Non coliforms Streptococci Enterococci CNS CNS Bedding S. S. aureus aureus S. How Do Bacteria S. uberis S. uberis S. agalactiae agalactiae Mycoplasma Mycoplasma Lactococci, Lactococci, Bacillus, Bacillus, S. Get Into BTM? S. dysgalactiae Many dysgalactiae Many others others Infected udder udder Udder, teat teat & teat teat end end Pseudomonas, Pseudomonas, Enterococci, Enterococci, Milking equipment, water, cleaning Bulk tank Assessing Milk Quality Standard Plate Count (SPC) Laboratory Pasteurization Count (LPC) Coliform Count (CC) Preliminary Incubation Count (PI) Standard Plate Count (SPC) Most Most commonly used throughout industry. Indication of total aerobic bacteria present in milk Milk Milk samples plated & incubated 48 hr at 32 o C (9 o F).bacterial colonies counted
Standard Plate Count Good Acceptable Concern (low) (medium) (high) < 1, < 2, > 2, 45 4 35 3 25 2 15 1 5 < 1, < 2, > 2, Reasons for high SPC Improper cleaning of of milking system Strep agalactiae mastitis Dirty udders & teats, dirty equipment Inability to to cool cool milk milk rapidly to to 4 F Failure of of water heater Failure in in sanitation Residual water in in lines Wet Wet & humid weather Wet Wet milking conditions PI Counts Performed by by holding milk at at 12.8 C C (55 F) for 18 18 hr. bacteria enumerated using SPC Theory.normal microbial flora of of cow (skin & teat bacteria) will NOT grow substantially during incubation at at 55 F.however, bacteria associated with inadequate hygiene practices will be able to to grow.pi counts should ALWAYS be be compared to to fresh SPC Goal.detect farm hygiene inadequacies that may not be be apparent with SPC alone Factors influencing PI PI counts. Precision of of incubation/temp Age Age & storage of of milk milk sample Types, number, stage of of growth & growth temp of of bacteria in in sample Murphy, 27 8, 7, 6, 5, 4, 3, 2, 1, < 1, < 5, > 5, PI Counts Good Acceptable Concern (low) (medium) (high) <1, <5, >5, <3-4X SPC >3-4X SPC 9, Generally > SPC...a 3-4 fold higher PI PI count than SPC suggests. 1. 1. Cleaning & sanitation of of the milking system 2. 2. Poor udder preparation before milking 3. 3. Failure to to cool milk rapidly 4. 4. Prolonged storage times 5. 5. Milking cows with wet teats 6. 6. Extremely wet & humid conditions.pi PI counts & SPC SPC spike spike day day after after rain rain when when cows cows milked that that are are wet wet & dirtier dirtier Lab Pasteurization Count (LPC) Measures heat-loving (thermoduric) bacteria Resistant environmental bacteria Survive pasteurization Sample heated to 62.8 C C (143 F) & held for 3 min, then bacterial colonies counted Destroys most mastitis pathogens.selects for those bacteria that can survive pasteurization temperatures Not a regulatory test.some milk plants perform this test to ensure quality of final product Good Acceptable Concern (low) (medium) (high) <1 <1 --2 >2 45 4 35 3 25 2 15 1 LPC Classifications 5 < 1 < 1-2 > 2 Why Are LPC s s High? Unclean milking equipment? Most often seen with persistent cleaning problems Faulty milking machine or or worn out parts? Leaky pumps, deteriorated pipe line gaskets, inflations and other rubber parts, and milkstone deposits Extremely dirty cows? Significant levels of of contamination from soiled cows can also contribute to to high LPC Coliform Count Not Not a regulatory test Measures coliform bacteria Associated with fecal & environmental contamination No No legal limits for raw milk unless coliforms cause SPC to exceed 1,/ml Achievable goal: < 5 cfu/ml
Coliform Count Good Acceptable Concern (low) (medium) (high) <5 <5-1 >1 4 35 3 25 2 15 1 5 < 5 < 1 > 1 High counts suggest: 1. 1. Poor milking practices 2. 2. Dirty equipment 3. 3. Contaminated water 4. 4. Dirty milking facilities 5. 5. Cows with mastitis Quality Milk Low SCC Low bacterial count Free of human pathogens Free of antibiotic residues Should Dairy Industry Be Concerned About Food Safety? You Bet & Here s s Why!!!! Raw milk contains foodborne pathogens & toxins that can cause human disease & illness Human disease outbreaks associated with consumption of unpasteurized milk Raw milk consumed by dairy producers & their families, farm employees, neighbors, raw milk advocates Contaminated raw milk could contaminate processing & slaughter facilities Raw Milk Consumption Estimates difficult to find.assumed that < 1% of US population consume raw unpasteurized milk & products made from raw milk.(yilmaz et et al., al., 29) 29) Many dairy farm families, farm employees & neighbors drink raw raw milk milk from bulk bulk tank tank Consumption increasing. 3.2% of of those surveyed in in CA CA had had consumed raw raw milk milk (Headrick et et al., al., 1997) 3.5% who who participated in in a 22 survey consumed unpasteurized milk milk within a 7 day day period before survey was was taken (CDC, 24) Promoted by by raw raw milk milk advocates Demand for for natural, unprocessed foods Consumers who who support produce, sell sell & buy buy local Raw Milk Consumption Reasons for consuming raw milk. Health Health benefits. Enhanced nutritional qualities. Better Better taste. Green movement. Freedom of choice. Science-based data to substantiate these claims limited & in most cases lacking Raw Milk Consumption Reasons NOT to consume raw milk. FOOD FOOD SAFETY.FOOD SAFETY.FOOD SAFETY much science-based data to to substantiate food safety hazards of of consuming raw milk Cost.commercial raw milk demands a premium price.even more than organic milk Costs Costs associated with disease outbreaks, illness & product recalls
Is Raw Milk Safe? ABSOLUTELY NOT!!!! May contain several pathogens: Enterotoxigenic Staph. aureus Campylobacter jejuni Salmonella species E. E. coli (EHEC & ETEC) Listeria monocytogenes Mycobacterium tuberculosis Mycobacterium paratuberculosis Brucella spp (abortus cattle) (melitensis- goats) Coxiella burnetii Yersinia enterocolitica..many more Bulk tank milk plated on on blood agar Staphylococcus aureus Found frequently in in BTM.significant cause of mastitis throughout world Produce enterotoxins (A-H) & toxic shock syndrome toxin (TSST-1).enterotoxigenic Staph aureus can cause disease & food poisoning 73 of 78 (93.6%) Staph. aureus isolated from milk of cows with mastitis positive for one or more enterotoxin genes; 69 of 73 (88.5%) harbored > 1 enterotoxin gene (Srinivasan & Oliver, 26) Large outbreak in in Japan caused by consumption of low-fat milk produced from skim milk powder contaminated with Staph aureus enterotoxin A Milkborne Disease Outbreaks Raw milk long been recognized in in transmission of of a variety of of microbial pathogens 29 outbreaks/yr in in US from 188 & 197 (Chin, (Chin, 1982) 1982) Caused ~ 25% of of all reported disease outbreaks from contaminated food & water in in 1938; since then milkborne disease outbreaks decreased significantly (Grade A PMO, PMO, 27) 27) From 1973-1992, 1992, 46 outbreaks (~2.4/yr) reported (Headrick et et al., al., 1998) 1998) From 1993-26, 68 outbreaks (~5.2/yr) associated with unpasteurized milk or or milk products made from unpasteurized milk reported (CDC, (CDC, 28) 28) Foodborne Pathogens in Bulk Tank Milk Pathogen C jejuni STEC E. coli L monocytogenes Salmonella spp. Summary of 2 studies conducted between 1982 and 24 Prevalence Mean (range) 3.7 (.4 12.3) 1.8 (.8 3.8) 4.4 (1. 12.6) 3.6 (.2 8.9) Detection of Foodborne Pathogens In the Dairy Farm Environment TN River UT Dairy Study Summary Most (44%) foodborne pathogens were isolated from fecal samples Bovine feces, lagoon water, bedding, bird droppings, & rats were areas of concern on dairies studies Good manure management is important for dairy farm hygiene
Recycling of Foodborne Pathogens on the Farm GOT Milk? Make Sure It s Pasteurized RAW MILK Quality Milk Safety & quality of dairy products start at at the farm level & continues throughout processing cannot transform a low(er) quality raw product into a high quality finished product Consumers/processors demanding a higher quality raw product low SCC & bacteria counts Many tests used to determine quality regulatory.scc & bacteria counts non-regulatory but used by by industry.pic, LPC, CC To meet quality standards, producers p must adopt production practices that reduce mastitis & bacterial contamination of BTM McCord Hall Fire Dec. 29 A few pictures of Lab 56 Lab 57 Taken the day after the fire, before any cleanup had started
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