Types of meat Spoilage

1.    Meat sliming:

·  It is an indication of spoilage, often observed before expiry date.

·  It is caused by psychotropic m.os (Pseudomonas, Acinetobacter, Moraxella, Alcaligenes, streptococcus, Leuconostoc, Bacillus, and Micrococcus) when the meat is kept in refrigerator at R.H more than 90%

·  At first, it appears as drop colonies which coalesce with each other to from yellowish brown slime all over the surface of meat.

Accordingly, the meat should be kept at 0-2̊c and 88% - 90% RH to avoid this type of spoilage.

2. Meat putrefaction:

It means hydrolytic cleavage of meat protein by m.os to form free amino acids (e.g. tyrosin +tryptophan) which result in typical putrefaction (odor + flavor).

Types of meat putrefaction:

a. Aerobic putrefaction:

* Cause: →aerobic spore former.

* Source: →skin, surface of carcass, Air.

Aerobic spore former (B.anthracis, B. subtilis, B.mycoides) they liquefy gelatin, peptonize meat and blood hemolysis.

* Sit of Beginning: at surface appearance

Meat characters: → Soft in consistency, alkaline pH, change color, smell 

b. Anaerobic putrefaction:

·  Cause: anaerobic Spore formers e.g. Cl. sporogenes, Cl. putreficum , Cl. perfingenes.

·  Sources: Soil, manure, small intestine.

·  Site of Beginning: deep seated parts later after aerobic spoilage after consuming of O₂.

· Meat characters: →greenish yellow color, more bad odor.

                                        →Some produce toxin (Cl. Perfringens)

C. Chromogenic Gram – ve rods:

· Causes: Pigment producing m.o_s. e.g. pseudomonas + flavobacterium

· Sources: water, soil

· Site of beginning: surface of meat.

· Meat characters: unpleasant odor

➡️ Ps. flourescens →green

➡️ Ps. prodigiosum →bloody = red

➡️ Ps. cyanogenus →bluish green

➡️ Serratia → red spot

Control of meat spoilage

1. surface drying of carcasses

2. Reducing of surface pH (to 4 – 4.5) which inhibit the growth of both spoilage and pathogenic m.o.

3. Using chlorinated & hot wash water

4. Cooling or refrigeration (chilling and freezing)

5. Salting and curing 

6. Enzyme inhibitors:

7. Irradiation

8. Packaging

9. Reduce the stress as possible before slaughtering

10. Using of antioxidants

11. Balanced relation in cold store between R.H, temp., air velocity