- Does raw milk have any substantial health benefits over free range pasteurised and “normal” milk.
So number 2.
Ok so to understand this we must know why we use the pasteurisation process and what happens during the pasteurisation process.
Ok so homogenisation and heat treatment:
-
Homogenisation is performed to avoid creaming of milk.
-
milk heated to ~60 degrees c forced through very small apertures at high pressure and velocities.
-
Fat globules break up into very small droplets which increase the surface area 5-6 fold
-
Extra proteins absorbed on globule surface, which prevent coalescence; thus lipids remain suspended in milk.
The milk is now homogenised
The aims of heat treatment:
To destroy all harmful micro organisms (MO) (i.e. those that cause tuberculosis and brucellosis) and reduce population of other MO.
It successfully destroys all pathogenic bacteria.
Two processes of pasteurisation:
High-temperature, short-time (HTST)
Holder or batch
HTST
-Cold unpasteurised milk pumped through Heat Exchanger.
-In HE raw milk pre-heated by pasteurised milk (which is partially cooled)
-Pre-heated milk passes through cloth filter and then into holding tube
In holding tube, milk is heated to 71.7c for 15s
Milk properly heated is returned to HE where it is cooled by incoming raw milk
-Milk passes through final cooling section.
Batch method
There are two batch methods:
In bottle
Ultra high temperature
Homogenised milk filled into bottles and heated to 120c for 15-60mins (usually 20mis)
- UHT 135-150c for at least 1s and then rapidly cooled
Hopefully know you can see that nothing funky has happened to the milk except for heating for anyone that thought otherwise.
This process of heating has relatively small effect on the nutrients. Due to the short lengths of time it is exposed to heat. This will depend on length of time and temperature under heating. Although as you can see the times under high temperature are relatively short.
I found this piece of literature from the Ohio state university, and it explains it much better then I could. So you get both my poor explanation and there good one.
Milk from healthy cows contains relatively few 23 bacteria (10 ?10 /ml), and the health risk from drinking raw milk would be minimal. However, milk is a natural food that has no protection from external contamination and can be contaminated easily when it is separated from the cow (Rosenthal, 1991). Raw milk normally has a varied microflora arising from several sources, such as the exterior surfaces of the animal and the surfaces of milk handling equipment such as milking machines, pipeline, and containers (Burton, 1986). Therefore, milk is susceptible to contamination by many pathogenic microorganisms, which result in infection and threat to consumer?s health. Addition- ally, there is the potential that disease of cows such as tuberculosis, brucellosis, typhoid, and listeriosis can be transmitted (Spreer, 1998). The average standard plate counts (SPC) for can and bulk milk are ~700,000 bacteria/mL and ~100,000 bacteria/mL respectively, depending on temperature and handling conditions. The microbial standards for grade ?A? raw milk are 100,000 bacteria/mL, for individual producer milk, 300,000 bacteria/mL, as commingled milk, 75,000 cells/mL as somatic cell count (SCC) (PMO, 2001). These standards are the maximum allowed and most dairy producers provide milk with concentrations considerably below the maximum allowable limits. Another indicator of milk quality is the preliminary incubation count (PI) with a maximum allowable count of 100,000 bacteria/mL on load, storage tank, or indi- vidual producer samples, although results of 25,000 bacteria/mL or less are desirable (DPC, 1997). Milk can be classified as a potentially hazardous food if it is not properly processed, handled, or stored.
Raw milk has been, and continues to be, a staple in the epidemiological literature; it has been linked to campylobacteriosis, salmonellosis, tuberculosis, brucellosis, hemorrhagic colitis, Brainerd diarrhea, Q fever, listeriosis, yersiniosis, and toxoplasmosis to name a few (Plotter, 2002). Outbreaks associated with the consumption of raw milk routinely occur every year. In 1995, the Center for Food Safety and Applied Nutrition and the U.S. Food and Drug Ad- ministration published guidelines that established a list of pathogen organisms transmitted through raw milk and milk products, such as Salmonella spp., Staphyloccocus aureus, Campylobacter jejuni, Yersina enterocolitica, Listeria monocytogenes, Escherichia coli (both enterotoxic and enteropathic), E. coli 0157: H7, Shigella spp., Streptococcus spp., and Hepatitis A virus. Among the fifty states and Puerto Rico, twenty- four states, including Ohio, do not permit the sale of raw milk directly to the consumer. Twenty-seven states permit the sale of raw milk for human consumption either at the farm where produced, in retail outlets, or through cow-share agreements. Twenty-nine states have recorded foodborne outbreaks traceable to raw milk consumption (NASDA, 2004).
Pasteurization is a thermal process widely used in the food and dairy industry with the objective of minimizing health hazards from pathogenic microor- ganisms and to prolong product shelf life. There are several temperature-time combinations to pasteurize milk that range from 63°C (145°F)/30 minutes or 72°C (161°F)/15 seconds to 100°C (212°F)/0.01 seconds. The bacteria standards for Grade ?A? pasteurized milk are 20,000 bacteria/mL and <10 coliform/mL (PMO, 2001). Heat may denature milk proteins. This effect is not considered a disadvantage from the nutritional point of view because it only involves changes in the specific arrangement of the casein protein. There is no breakdown of peptide linkages; therefore, casein can be considered a thermal-resistant compound. Although α-lactoalbumin is relatively heat stable, other whey proteins can be denatured as a result of heating. These denatured proteins are more digestible than their natu- rally occurring form because the protein?s structure is loosened and enzymes can act easier (Renner, 1986). Pasteurization does not impair the nutritional qual- ity of milk fat, calcium, and phosphorus (Beddows and Blake, 1982). Pasteurization temperature does not affect fat-soluble vitamins (A, D, and E), as well as the B-complex vitamins riboflavin, pantothenic acid, biotin, and niacin. The losses of vitamins, such as thiamin (<3%), pyridoxine (0?8%), cobalamin (<10%), and folic acid (<10%) are considered lower than those that take place during the normal handling and preparation of foodstuffs at home (Lund, 1982). Most of the vitamin C is lost during handling, pas- teurization, packaging, and oxidation of milk; about 70% of the remaining vitamin C and 90% of riboflavin can be destroyed by sunlight exposure during storage (Renner, 1986). Scientific research has shown that the detrimental effects of pasteurization on the nutritional and physi- ological values of milk are negligible considering the safety benefits in regards to consumers? health.
References
Beddows, C. G., and C. Blake. (1982). The status of fluoride in bovine milk. II. The effect of various heat treatment processes. J. Food Technol. pp. 63?70.
Burton, H. (1986). Microbiological aspects of pasteurized milk. Bulletin of the International Dairy Federation, No. 200, Chapter III. pp. 9?14.
DPC. (1997). Guidelines for troubleshooting on-farm bacteria counts in raw milk. The Dairy Practices Council. Keyport, NY.
Lund, D. B. J. (1982). Growth of thermoresistant strep- tococci and deposition of milk constituents on plates of heat exchangers during long operating times. J. Food Protection. 45(9): 806?812, 815.
NASDA. (2004). Raw milk survey. Dairy Division of the National Association of State Departments of Agriculture. September Annual Meeting. St. Paul, MN.
Plotter, H. M. (2002). Raw milk and milk products for human consumption. Dairy Division, Indiana State Board of Animal Health, Indianapolis, IN.
PMO. (2001 Revision). U.S. Department of Health and Human Services, Public Health Services. Food and Drug Administration (FDA). Washington, DC.
Renner, E. (1986). Nutritional aspects?Part I?Bio- chemical composition of pasteurized milk. Bulletin of the International Dairy Federation, No. 200, Chapter VII. pp. 27?29.
Rosenthal, I. (1991). Milk and Dairy Products Properties and Processing. Ed. Balaban Publishers VCH, New York, NY. pp. 70?71.
Spreer, E. (1998). Milk and Dairy Product Technology. Ed. Marcel Dekker, Inc. New York, NY. pp. 39?41.