Is "expiry date" strictly a matter of science?

Can an expiry date be calculated? For example the expiry date of fresh dairy products in the Philippines is 4 days. Note that it doesn't not mean fresh milk gets bad in 4 days in the refrigerator, it can stand 10 days or more, but because with an expiry date of 10 days the local market would be infested with low cost fresh milk coming by ships from China, Vietnam, Korea, Australia, or Europe. This would destroy the flourishing local dairy companies that sell milk over price.

My questions -
It is true that adding a pinch of salt once you open a carton of milk helps to keep the milk fresher? If so, why not put it in a label?
Is it true that you can keep cheese longer by putting it in a ziploc bag with a paper towel that has been soaked in white vinegar? If so, why not put it in a label?
Do you think there's an aspect of marketing, politics etc in expiry date, not just a matter of science?
Can we accurately calculate/predict the expiry date independent on government mandate?

You can keep a lot of food items longer by putting them in the freezer, maybe using some magic will help, but the food producer should determine expiry dates based on shelf life trials at known temperatures. This goes on the label usually with a bit of leeway added for safety. I'm no expert, but I would say it is based on science or at least it should be. What's it got to do with the government?

Regards,
Simon

You can keep a lot of food items longer by putting them in the freezer, maybe using some magic will help, but the food producer should determine expiry dates based on shelf life trials at known temperatures. This goes on the label usually with a bit of leeway added for safety. I'm no expert, but I would say it is based on science or at least it should be. What's it got to do with the government?

Regards,
Simon

Expiry date is almost never a calculated value, IMHO. What typically happens is they take a sample of the product (preferably from several batches) and to stability testing. They'll store the product in a variety of conditions and test the quality at set intervals. They'll take the average and put in a safety factor (15% is bandied about a lot) and then whap it on the packaging. For example, milk - they'll take maybe 100 bottles, store twenty each in different conditions and then take one bottle from each location every day and test it for 20 days. Now, What's it got to do with the government? Sometimes it's government mandated regardless of reality and sometimes companies will just guess. I wouldn't really call expiry dates calculated, more vague rule of thumb guideline that applies in certain circumstances. I can take any product and make it expire long before the expiry date says it should and I can keep it fresh long after the expiry date says it should have turned to mush. If you can come up with a way to accurately predict expiry dates then a lot of companies will be willing to pay you lots and lots of money. But this is only my opinion.

Dear MoM,

Probably food safety expire date can be calculated with pathogen modelling programs.
But, expire date is mostly not about food safety, but about qulity, sensoric parameters and decay. It therefore depends on the organisation stating the shelf life, what the shelf life should be.

You asked two different things: 1) if expire date is a matter of science? 2) can expire date be calculated?
1) the testings you mention above are IMO science and therefore answer on question 1 = yes.
2) pathogen growth and decay can be calculated if there is collected enough data with tests from question 1, so calculating is possible.

I certainly do not agree with you that expire dates are only vague and guessings. I do agree that there are commercial shelf lifes, but what is wrong with that? It keeps money rolling.

Dear MoM,

Probably food safety expire date can be calculated with pathogen modelling programs.
But, expire date is mostly not about food safety, but about qulity, sensoric parameters and decay. It therefore depends on the organisation stating the shelf life, what the shelf life should be.

I agree with you that most expiry dates are entirely up to the organization/manufacturer as strengthened by the following quote:

With just a couple of exceptions, no laws regulate package dates -- variously referred to as sell-by dates, pull dates, expiration dates or quality dates. That most dates appear at all is entirely up to the manufacturer or the grocer. The federal government only requires expiration dates on infant formula and some baby food.
Read more: http://www.sfgate.co...L#ixzz1gaj7EQJo

But I am not sure I agree with you a hundred percent on expiry date calculation. There are too many variables for certainty...

You asked two different things: 1) if expire date is a matter of science? 2) can expire date be calculated?
1) the testings you mention above are IMO science and therefore answer on question 1 = yes.

Can we conclude that it is an exact science for dating?

2) pathogen growth and decay can be calculated if there is collected enough data with tests from question 1, so calculating is possible.

But only if the product has been handled correctly at all stages.

I agree that expiry date is a science. There may varying shelf life for same product but manufactured by different company. I have worked with companies who will go a long way even to increase the shelf life of their product by one day and this would definitely involve science. This really tells how much a company takes care of their products from the point of view of Food Safety and a longer shelf life can be considered as reference for quality and Food Safety Standards. Of course the product should be natural ( no artificial preservatives).

well, yeah, the "shelf-life" of a product can be calculated using certain formulas and this is an applied kinetics matter. However, it is a "theoretical" method and the results may vary in practice. Therefore, it's always best to test the shelf life under different conditions (different temps, air humidity, packaging etc.) to make sure your customers can safely consume your products.