Shelf Life and High-Temperature, Short-Duration Pasteurization

Good day

Maybe I am immunized to the natural bacteria in milk and therefor want (or need) them.

Here in sunny SA we also homogenize milk (the result a good tasting white fluid)

http://www.wisegeek.com/what-is-homogenized-milk.htm

I have customers in the dairy industry and are aware of the reasons for pasteurising etc. Personally I don't like the end product. I used to make myself sour milk but this stuff just go rotten.

I've copied an article from wikipedia (sp) for you. See below! Any more info needed you can look on line under the title or contact us

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Pasteurization is a process which slows microbial growth in food. The process was named after its creator, French chemist and microbiologist Louis Pasteur. The first pasteurization test was completed by Louis Pasteur and Claude Bernard on April 20, 1862. The process was originally conceived as a way of preventing wine and beer from souring.^[1]

Unlike sterilization, inventor Nicolas Appert, pasteurization is not intended to kill all pathogenic micro-organisms in the food or liquid. Instead, pasteurization aims to reduce the number of viable pathogens so they are unlikely to cause disease (assuming the pasteurization product is refrigerated and consumed before its expiration date). Commercial-scale sterilization of food is not common because it adversely affects the taste and quality of the product. Certain food products are processed to achieve the state of commercial sterility.^[2]

Pasteurization typically uses temperatures below boiling since at temperatures above the boiling point for milk, casein micelles will irreversibly aggregate (or "curdle"). There are two main types of pasteurization used today: High Temperature/Short Time (HTST) and Extended Shelf Life (ESL) treatment. Ultra-high temperature (UHT or ultra-heat treated) is also used for milk treatment. In the HTST process, milk is forced between metal plates or through pipes heated on the outside by hot water, and is heated to 71.7 °C (161 °F) for 15–20 seconds. UHT processing holds the milk at a temperature of 138 °C (280 °F) for a fraction of a second. ESL milk has a microbial filtration step and lower temperatures than HTST.^[3] Milk simply labeled "pasteurization " is usually treated with the HTST method, whereas milk labeled "ultra-pasteurization " or simply "UHT" has been treated with the UHT method.

Pasteurization methods are usually standardized and controlled by national food safety agencies (such as the USDA in the United States and the Food Standards Agency in the United Kingdom). These agencies require milk to be HTST pasteurized in order to qualify for the "pasteurization" label. There are different standards for different dairy products, depending on the fat content and the intended usage. For example, the pasteurization standards for cream differ from the standards for fluid milk, and the standards for pasteurizing cheese are designed to preserve the phosphatase enzyme, which aids in cutting.

The HTST pasteurization standard was designed to achieve a 5-log reduction, killing 99.999% of the number of viable micro-organisms in milk. This is considered adequate for destroying almost all yeasts, mold, and common spoilage bacteria and also to ensure adequate destruction of common pathogenic heat-resistant organisms (including Mycobacterium tuberculosis, which causes tuberculosis and Coxiella burnetii, which causes Q fever). HTST pasteurization processes must be designed so that the milk is heated evenly, and no part of the milk is subject to a shorter time or a lower temperature.

[edit] Recent developments

A newer method called flash pasteurization involves shorter exposure to higher temperatures, and is claimed to be better for preserving color and taste in some products.

The term cold pasteurization is used sometimes for the use of ionizing radiation (see Food irradiation) or other means (e.g. chemical) to kill bacteria in food. Food irradiation is also sometimes called pasteurization.

Another means of pasteurization is using pressure called high pressure pasteurization (HPP) ^[4] also known as High pressure food preservation where extremely high pressure is used to kill the bacteria.

[edit] Products that can be pasteurized

• Almonds
• Apple cider
• Beer
• Canned food
• Crabs
• Eggs
• Fruit juice
• Honey (not necessary unless it is diluted)
• Juice
• Maple Syrup
• Milk
• Palm wine
• Ready Meal
• Soy sauce
• Sports drinks
• Vinegar
• Water
• Wine
• cream
• cheese

[edit] Pasteurization of milk

Pasteurization is typically associated with milk, first suggested by Franz von Soxhlet in 1886. HTST pasteurized milk typically has a refrigerated shelf life of two to three weeks, whereas ultra pasteurized milk can last much longer when refrigerated, sometimes two to three months. When UHT treatment is combined with sterile handling and container technology (such as aseptic packaging), it can even be stored unrefrigerated for 3–4 months.^{[citation needed]}

A growing body of research supports the belief that pasteurization was not so much a response to any hazards or contamination issues with milk itself, but rather may have been a response to the hazards and contamination issues that resulted from the newly emerging "industrialized" dairy industry. It's likely that, with the burgeoning growth of large-scale, longer-distance distribution networks, the rise of chain-store supermarkets, and the resulting impetus for larger-herd dairy operations and mechanized milking, there came a corresponding inability to preserve the quality and inherent bacterial-resistance qualities of fresh milk being marketed in a localized area.^[5]

[edit] Alternative milk pasteurization standards Cooling tank

In addition to the standard HTST and UHT standards, there are other lesser-known pasteurization techniques. The first technique, called "batch pasteurization", involves heating large batches of milk to a lower temperature, typically 63 °C (145 °F) for 30 minutes, followed by quick cooling to about 4 °C (39 °F). The other technique is called higher-heat/shorter time (HHST), and it lies somewhere between HTST and UHT in terms of time and temperature. Pasteurization causes some irreversible and some temporary denaturation of the proteins in milk.

In 2001, the Animal and Plant Health Inspection Service of the USDA considered new rules requiring double pasteurization, which would have entailed holding milk at 72 °C (161 °F) for two separate 15-second periods, instead of one 30-second period as was the current standard.

In regions including Africa and South Asian countries, it is common to boil milk to sterilize it after it is harvested. This intense heating greatly changes the flavor of milk, to which the respective people are accustomed.^{[citation needed]}

[edit] Effectiveness of pasteurization

Milk pasteurization has been subject to increasing scrutiny in recent years, due to the discovery of pathogens that are both widespread and heat resistant (able to survive pasteurization in significant numbers).^[6] Researchers have developed more sensitive diagnostics, such as real-time PCR and improved culture methods that have enabled them to identify pathogens in pasteurized milk.

Some of the diseases that pasteurization can prevent are tuberculosis, diphtheria, salmonellosis, strep throat, scarlet fever, listeriosis and typhoid fever.

[edit] See also

• Canning
• Cold pasteurization
• Dairy product
• Flash pasteurization
• High pressure food preservation
• Homogenization
• Pasteurized shell eggs
• Raw milk
• Solar water disinfection

[edit] References

1. ^ Carlisle, Rodney (2004). Scientific American Inventions and Discoveries, p.357. John Wiley & Songs, Inc., new Jersey. ISBN 0471244104.
2. ^ Montville, T. J., and K. R. Matthews: "food microbiology an introduction", page 30. American Society for Microbiology Press, 2005.
3. ^ Paving the Way for ESL - extended shelf-life milk products | Dairy Foods | Find Articles at BNET.com
4. ^ , http://www.defendingfoodsafety.com/tags/high-pressure-pasteurization
5. ^ [1] The Untold Story of Milk by Ron Schmid, ND; New Trends Publishing, Nov. 2003
6. ^ Irene R. Grant et al., "Effect of Commercial-Scale High-Temperature, Short-Time Pasteurization on the Viability of Mycobacterium paratuberculosis in Naturally Infected Cows' Milk", Applied and Environmental Microbiology, February 2002, p. 602-607, Vol. 68, No. 2

[edit] External links

• Online forum on modern day pasteurization equipment
• Thermal treatment in food industry
• Pasteurization of animal by-products / (Animal By-Products Regulations)

Retrieved from "http://en.wikipedia.org/wiki/Pasteurization" Categories: Food science | Unit operations | Food preservation | Louis Pasteur Hidden categories: All articles with unsourced statements | Articles with unsourced statements from May 2007 | Articles with unsourced statements from February 2007 Views

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dear sir

thanx for updating but i was thinking it why not to review this with changing environment

with warm regards

sps sawhney

spssawhney@yahoo.com

0919915742601

Hello Mr. Spssawhney,

The key to enhancing or extending the shelf life of fresh milk is by keeping everything clean in the system, from the milking stage,to the transfer to milk cans, collecting into tanks and holding to accumulate enough volume before starting to pasteurize or heat the milk. The microbial load of the milk must be kept to a minimum by quickly cooling the raw milk if the travel time is several hours before it arrives at the dairy plant for processing. The shelf life of the milk will also depend on the storage conditions that you put the product into. Normally, pasteurized milk products in any kind of container will need to be kept refrigerated.

The adjustment in time and temperature in the pasteurizer has to be determined carefully. These are established by doing several trials with bacteria count determination before and after heating or pasteurizing. In the milk industry, this have been quite established.

If you increase the holding time from 15-16 seconds to 1 minute, I could imagine the length of the holding tube that you have to add. Or you can also change the holding time by reducing your flow rate. But not advisable as other parameters will also be affected, will reduce your production capacity.

dear rupertal

greetings and good day

thanx for your valuable comments

ours is a tropical country and the bacterial count of raw milk rises very fast

thus the microflora of milk at dairy dock is very high that is why i thought of increasing holding time by 1 minute

kindly comment

sps sawhney

spssawhney@yahoo.com

0919915742601

Hi, Mr. Sps Sawhney,

How high is your average count when the milk arrives at your factory? Is the milk cooled down or refrigerated when this is transported from the farm? There is a big possibility that spoilage or fermentation has already started before you process the milk. The increase in micro flora or microbial population is very rapid if the milk is warm, even just at room temperature(tropical environment 25-30 deg C) . The normal pasteurization temperature with a standard holding time cannot kill or reduce this bacteria count to meet the requirement of 50T count/gram maximum. Even increasing the holding time to a longer period may not attain the desired bacteria count. There are other quality aspects of the milk product that you have to consider, like changes in taste (souring) or burnt taste if you increase temp. and longer holding period. Or coagulation can occur if there is too much bacteria present.

The most important step in producing a good quality milk is to start from the farm.
Cool down the milk quickly and transport in insulated, clean containers. As much as possible, limit acceptance of any raw milk that arrives in the dock above 10 deg C.

If you are redoing your pasteurization system, I would think UHT is better and safer in the tropics.

I believe the milk pressure is raised and then subjected to 140C for 1/2 sec. This is supposed to kill all bacteria and such milk can keep for a long time, without refrigeration.

Because of the rate at which all bacteria multiply in the tropics and the almost impossible task of keeping all contamination out of all milk supplied to your factory, UHT would be the safest course.

If using normal pasteurization, (30 minutes at 60C?) I would be inclined to up the temp to about 75C. This should allow existing equipment to still be used (without severe reduction of capacity as would happen with an increase in treatment time) while still keeping the flavor change of the milk within acceptable bounds. It still won't make a big dent in the thermophillic bacteria, and the possible presence of harmful thermophiles I would expect to be a worry in the tropics, as the environment is full of them.

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