Questioning Recommended Freezing Times.

[Parson Snows]

Following the previous posting of the table (summary shown below) I have been asked the following questions.

Q1) Why it is that the time recommended for Fresh Pork Roasts (Frozen) is 4 to 8 months when Ground Pork is only 3 to 4 months?



Q2) Why is it that the time recommended for Pork Sausages is less than that for ground pork, when the sausages are made of ground pork?

Q3) Why is it that the time for bacon; a cured item; is only ONE month when the recommended times for Fresh Pork Roasts (Frozen) is 4 to 8 months?

KEEPING IT SIMPLE

A1) IMPORTANT FACT: ALL MEAT etc. has bacteria present. The 4 to 8 months stated/recommended is for a WHOLE pork roast. For simplicity let us assume that the roast measures 3 inches high • 6 inches wide • 12 inches long. The surface area of this “theoretical” piece of pork would then be

A = 2 (W • L + L • H + H • W)
A = 2 (6 • 12 + 12 • 3 + 3 • 6)
A = 252 sq. in.

This is the surface that the bacteria present has available to spread upon, unless the roast has been injected with brine etc. then the area would be greater. For the purpose of this exercise we will assume that it has not be injected or treated in any way whatsoever.

For the ground pork times let us assume that we take the same “theoretical” piece of pork and grind it through a sterilised mincer/grinder fitted with a “final plate” size of 1/8 inch (3 mm). The surface area now available for the spread of the bacteria present, being very basic, would then be

As = Pi • d 2 (OR 4 • Pi • r • r)
As = 3.141 592 65 • 0.125 • 0.125
As = 0.049 087 385 sq. in (per sphere)



The above illustration shows 1” by 1” (minced/ground using a "final plate" size of 1/8 inch (3mm), totaling 64 spheres (8 by 8))

Therefore the TOTAL number of spheres in this "theoretical" piece equals
No. of Spheres = (3 • 8) • (6 • 8) • (12 • 8)
No. of Spheres = 110 592

At = As • No. of Spheres
At = 0.049 087 385 • 110 592
At = 5 428.672 082 sq. in

As you can see there is now a surface area of approximately 21.5 times that of the initial Pork Roast available for the bacteria present to multiply/spread. Freezing the ground/minced meat does not kill the bacteria, though rather just slows its action down.

A2) It is actually the addition and the amount of the salt in the sausage – the ingredient that is always assumed/considered to be a preservative – that causes the acceleration of the fat included/added in the sausage mixture (25 % etc.) to become rancid.

A3) It is a combination of addition of the salt in the cured bacon and the fact that the quality of frozen cured meat products deteriorate rather quicker than other meat products that sets this recommended time.

Note: Smoking the meat or using a vacuum packing m/c can extend these times though the principles remain unchanged and the eventual outcome will be the same, just delayed.

I hope that you find this information of some use to you

Kind regards

Parson Snows

[Parson Snows]

As several people have expressed interest in this I offer a "Simple explanation of Oxidative Rancidity"

The following text has been taken verbatim from “Processed Meats”, 2nd edition, 1984 by A.M. Pearson, AVI Publishing Company Inc.

Rancidity

Rancidity is caused by hydrolysis or oxidation. Bacteria can be the source of the enzymes: lipases cause hydrolysis and oxidases cause oxidation. Both give rise to the odors and flavors that are associated with rancidity.
Most rancidity problems encountered in meat products, however, are not of microbial origin but result from the reaction of oxygen with unsaturated fats. Oxidation of fats is influenced by quantity of oxygen present, temperature, light, and pro-oxidant catalysts. Salt is the best example of such catalysts. In addition, various chemicals, such as ozone, hydrogen peroxide, and other strong oxidizing agents markedly influence the development of rancidity. One of the main reasons microorganisms are not a significant factor in the development of rancidity in meats is that the free fatty acids liberated by hydrolysis of fats inhibit the growth of many types of microorganisms. In addition, the peroxides formed during oxidation of unsaturated fatty acids are quite toxic to many microorganisms.

The following text has been taken verbatim from “Principles of Meat Science”, 1975 by John C. Forrest, W.H. Freeman and Company.

Chemical Reactions Affecting Deteriorative Changes

OXIDATIVE RANCIDITY. Meat fats are susceptible to oxidation when they are exposed to the molecular oxygen present in air. This results in the production of a strong disagreeable odor and flavor in the cooked product. When these chemical changes occur, they constitute a defect referred to as oxidative rancidity. The term autoxidation is used to describe the chemical reactions that cause oxidative rancidity. The characteristic flavor and odor of oxidized fat is caused by the presence of low molecular weight aldehydes, acids, and ketones that form during the oxidation and decomposition of the fatty acid molecules. Polyunsaturated fats are much more susceptible to autoxidation than are monounsaturated fats. Saturated fatty acids are the most resistant to oxidation and the development of rancidity. In the relatively short period of time that it usually takes for rancidity to develop, probably only the polyunsaturated fatty acids undergo any appreciable autoxidation. Thus, the polyunsaturated fatty acids are the focal point for understanding the autoxidation of fats.
The rate of autoxidation is enhanced by the presence of prooxidants, such as heat and exposure to light, especially ultraviolet light. Prooxidants favor oxidation by catalyzing the oxidation reactions, and antioxidants inhibit oxidation. Prooxidants include nitrite, sodium chloride, a number of metals (such as copper, iron, manganese, and cobalt), and numerous other substances and agents. Since heat and light increase the autoxidation rate, meat stored at refrigerator or freezer temperatures, should also be kept in the dark in order to retard rancidity development. Obviously, minimizing the amount of air in containers, or eliminating it completely during storage, especially during extended freezer storage, also will retard the development of rancidity.
The storage life of ground products is shortened because of the incorporation of oxygen during the grinding process. The addition of salt to processed meat products also shortens their storage life. However, some ingredients added during processing (such as ascorbate, sage, and the phenolic compounds present in wood smoke) possess antioxidant properties and tend to retard the development of rancidity.
In the case of edible fats such as lard, rancidity is inhibited by the addition of antioxidants during processing. Two widely used antioxidants are butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA). The antioxidants used commercially generally contain various combinations of several antioxidants so as to take advantage of the desirable properties of each. Combinations of BHT, BHA, n-propyl gallate, and citric acid are commonly used in edible fats, and in foods with a moderate to high fat content.

I hope that this information is of some use to some of you

For the forum I think that this is enough "Science 101" on this subject however, if anyone wants to go deeper in the "science" part then PM me and I'll be glad to send you some further information by PM.

kind regards

Parson Snows