Commodity Microbiology – Milk and Dairy Products PDF

Commodity Microbiology – Milk and Dairy Products ENH 333 – Introduction to Food Hygiene Lecture 7  DineSafe Pass System Crucial Infraction - These infractions must be corrected immediately. An order to close the premises may be issued and/or immediate action m...

Commodity Microbiology – Milk and Dairy Products ENH 333 – Introduction to Food Hygiene Lecture 7  DineSafe Pass System Crucial Infraction - These infractions must be corrected immediately. An order to close the premises may be issued and/or immediate action must be taken to remove or eliminate the health hazard. A Closed Notice will be issued and must be posted, and other enforcement action will be taken. Crucial infractions are conditions that endanger food directly, such as contamination, time-temperature abuse or lack of safe-to-drink water or any other condition that constitutes a health hazard.  Significant Infraction - These infractions must be corrected immediately and a re-inspection to check for compliance will be conducted within 24 to 48 hours. Legal action may be taken should these infractions remain outstanding. Under exceptional circumstances a re-inspection to check for compliance may be extended beyond 48 hours. Significant infractions concern food handling, preparation, storage and/or service. Minor Infraction - These infractions must be corrected immediately. A follow-up compliance check will be conducted at the next scheduled inspection.  Milk Fresh liquid milk is capable of supporting the growth of almost every organism – Contains 87% water, 3.5% protein, 3.9% fat, 4.9% carbohydrates (mainly lactose) and numerous B vitamins and minerals Milk in the udder is almost sterile – when animals are healthy However, freshly drawn milk is generally contaminated from various sources: – Udder infections, dirty udders and teats, handlers, equipment Milk tends to be spoiled by bacteria as they can grow faster than fungi – Low temperature storage influences the organisms that can grow  Milk Microbiota Pseudomonas Lactococcus Alcaligenes Streptococcus Aeromonas Lactobacillus Acinetobacter Bacillus Moraxella Micrococcus Falvobacterium Corynebacterium Salmonella Listeria monocytogenes Campylobacter Mycobacterium tuberculosis E. coli Yersinia enterocolitica Brucella Staphylococcus aureus  Milk Spoilage Milk spoils through the action of lactic acid bacteria that feed on lactose and lower the pH by producing lactic acid, causing curdling If mould growth occurs on the surface, the pH may then increase leading to the growth of proteolytic bacteria that will liquefy the milk curd In raw milk, Alcaligenes viscolactis will cause ropiness – slime production Spoilage of pasteurized milk is primarily due to psychrophilic bacteria that produce heat-stable enzymes (lipases, proteases) which are not destroyed by pasteurization – Enzymes lead to milk spoilage by causing rancid and bitter flavours  The Lactoperoxidase System Lactoperoxidase is a heat stable enzyme present in cow’s milk It has no antibacterial effect on its own, but catalyzes a reaction that produces hypothiocyanite (OSCN-), which has an antibacterial effect in fresh raw milk The two essential components for the reaction, thiocyanate and hydrogen peroxide, are naturally present in milk in varying concentrations – But levels are low, and supplementation of the two essential components is needed for effective treatment This treatment system is used in developing countries to extend the shelf life of raw milk when there is a lack of refrigeration during on-farm storage and transportation  Milk Heat Treatment It is illegal to sell or distribute raw milk in Canada – also illegal to sell products made from raw milk (with one exception) All liquid milk should be heat treated to destroy pathogens and increase keeping quality – Endospores of pathogens such as Clostridium botulinum and thermoduric spoilage organisms such as Clostridium tyrobutyricum, C. sporogenes, or Bacillus cereus are not destroyed Two heat treatment methods: – Pasteurization – Sterilization (UHT)  Milk Pasteurization Low Temperature-Long Time (LTLT) The batch method Needs agitation, and “open” cleaning may allow contamination More suitable for small-scale dairies Time/temperature requirements (O. Reg. 493): If 6°C  Milk Testing Legislation requires various tests to be carried out on raw milk Tests can be carried out by the Central Milk Testing Lab or the processor – processor won’t do the full range of tests Producers face monetary penalties for failing tests Composition tests: – For fat, protein, lactose content and other solids Abnormal freezing point: – Milk must have a freezing point that is less than -0.506°C – Used to determine if water has been added – Closer the freezing point to 0°C, the greater the water content  Milk Testing Inhibitor test: – Tests for antibiotic residues – can enter milk from cows being treated – Most tests are negative; if positive, milk can’t be used for human consumption – important for food safety Microbiological tests: – Grade 1 milk must have aerobic bacteria counts