SPOILAGE IN MEAT AND MEAT PRODUCTS Doç. Dr. Arzu Çağrı Mehmetoğlu

FRESH MEATS AND POULTRY

At the time of slaughter the internal tissues of healthy slaughter

animals - free of bacteria

At the retail level varying numbers and types of

microorganisms found.

The primary sources and routes of microorganisms to fresh meats : The stick knife

Animal hide

Gastrointestinal tract

Hands of handlers

Containers

Handling and storage environment

Lymph nodes

1. THE STICK KNIFE

If the knife is not sterile, organisms are swept into the bloodstream, where they may be deposited throughout the carcass.

2. ANIMAL HIDE

Some organisms from the hide enter the carcass by the stick knife

Others from the hide may be deposited onto the dehaired carcass or onto freshly cut surfaces

Injury

becomes airborne can contaminate dressed out carcasses

3.GASTROINTESTINAL TRACT

Intestinal contents with microorganisms contaminate the surface of carcasses

Rumen of ruminant animals, which typically contains ∼1010 bacteria per gram

4. HANDS OF HANDLERS

a source of human pathogens to freshly slaughtered meats

Even when gloves are worn,

organisms from one carcass can be passed on to other carcasses

5. CONTAINERS

Meat cuts that are placed in nonsterile containers -contaminated with the organisms in the container.

This tends to be a primary source of microorganisms to ground or minced meats.

6. HANDLING AND STORAGE ENVIRONMENT

Circulating air significant source of organisms to the surfaces of all

slaughtered animals

Temperature Rapid cooling

Oxygen

The method of dlaughter and bleeding

Physiological condition of the animal Fatique

Low glycogen The pH will not drop to 5.6

7. LYMPH NODES

In the case of red meats, lymph nodes contain large numbers of organisms, especially bacteria.

If they are cut through or added to portions that are ground, one may expect this biota to become prominent.

BIOCHEMICAL EVENTS THAT LEAD TO RIGOR MORTIS

When the slaughter of a well-rested beef animal,

a series of events takes place that leads to the production of meat:

1. Circulation stops: The ability to resynthesize ATP (adenosine

triphosphate) is lost;

lack of ATP causes actin and myosin to combine to form actomyosin, which leads to a hardening of muscles.

(MYOSIN FLAMENT)

2. The oxygen supply drops, resulting in a reduction of the O/R (oxidation–reduction) potential.

3. The supply of vitamins and antioxidants stops, resulting in a slow development of rancidity

4. Nervous and hormonal regulations stops, thus causing the temperature of the animal to fall and fat to solidify

5. Respiration stops, which stops ATP synthesis.

6. GLYCOLYSIS BEGINS

resulting in the conversion of most glycogen to lactic acid, which lowers pH from about 7.4 to about 5.6.

pH depression also starts protein denaturation,

releases and activates cathepsins,

and completes rigor mortis.

7. The reticuloendothelial system stops to protect, thus allowing microorganisms to grow unchecked.

8. Various metabolites accumulate that also help protein denaturation.

Reticuloendothelial system: relating to a bodily system that consists of all the cells able to ingest bacteria, colloidal particles

RIGOR MORTIS

require holding freshly slaughtered beef between 24 and 36 hours at 2–5◦C

prolonged storage at refrigerator temperatures, microbial spoilage begins.

the center temperatures are not reduced to the refrigerator range, the spoilage can start by bacteria of internal

sources.

Clostridium perfringens and Enterobacteriaceae family

FACTORS EFFECTING CONTAMINATION

Table 4–1 Genera of Bacteria Most Frequently Found on Meats and Poultry

Genus Gram Reaction Fresh Meats Fresh Livers Poultry

Acinetobacter − XX X XX

Aeromonas − XX X

Alcaligenes − X X X

Arcobacter − X

Bacillus + X X

Brochothrix + X X X

Campylobacter − XX

Carnobacterium + X

Caseobacter + X

Citrobacter − X X

Clostridium + X X

Corynebacterium + X X XX

Enterobacter − X X

Enterococcus + XX X X

Erysipelothrix + X X

Escherichia − X X

Flavobacterium − X X X

Hafnia − X

Kocuria + X X X

Kurthia + X

Lactobacillus + X

Lactococcus + X

Leuconostoc + X X

Listeria + X XX

Microbacterium + X X

Micrococcus + X XX XX

Moraxella − XX X X

Paenibacillus + X X

Pantoea − X X

Pediococcus + X

Proteus − X X

Pseudomonas − XX XX

Psychrobacter − XX X

Salmonella − X X

Serratia − X X

Shewanella − X

Staphylococcus + X X X

Vagococcus + XX

Weissella + X X

Yersinia − X

Note: X = known to occur; XX = most frequently reported.

Why only a few types predominate in spoiled meats?

to return to the intrinsic and extrinsic parameters that affect the growth of spoilage microorganisms.

pH: have pH values within the growth range of most of the organisms

Nutrient and moisture contents are adequate to support the growth of all organisms

Although the O/R potential of whole meats is low, O/R conditions at the surfaces higher

Of the extrinsic parameters,

**temperature of storage - important in controlling the types of microorganisms that develop on meats, as these products are normally held at refrigerator temperatures

FUNGAL SPOILAGE OF FRESH MEATS

Various spoilage conditions of whole beef:

Thamnidium, Mucor, and Rhizopus, all of which produce “whiskers” on beef;

Cladosporium, a common cause of “black spot”;

Penicillium, which produces green patches;

Sporotrichum and Chrysosporium, which produce “white spot.”

Molds generally do not grow on meats if the storage temperature is below 5◦C

GROUND BEEF OR HAMBURGER MEAT

spoiled mostly by bacteria,

the most important: Pseudomonas, Alcaligenes, Acinetobacter, Moraxella,

and Aeromonas.

the primary cause of spoilage- Pseudomonas and Acinetobacter-Moraxella spp.

BEEF ROUNDS AND QUARTERS

Undergo deep spoilage, usually near the bone, especially the “aitch” bone.

This type of spoilage is often referred to as “bone taint” or “sours.”

Only bacteria have been implicated, with the genera Clostridium and Enterococcus being the primary causative agents.

BEEF CUTS, SUCH AS STEAKS OR ROASTS

Undergo surface spoilage; whether the spoilage organisms are bacteria or molds depends on available moisture.

Freshly cut meats stored in a refrigerator with high humidity regularly undergo bacterial spoilage rather than mold spoilage.

The essential feature of this spoilage is surface sliminess

The relatively high O/R, availability of moisture, and low temperature favor the pseudomonads

The slime layer results from the combination of surface colonies and is largely responsible for the sticky consistency of spoiled meats.

The development of off-odor and slime on dressed chicken

(squares) and packaged beef (circles) during storage at 5◦C.

Significance of total viable microbial numbers in food products

relative to their use as indicators of spoilage. (a) Microbial spoilage

generally not recognized with the possible exception of raw milk,

which may sour in the 105–106 range. (b) Some food products show

incipiency in this range. Vacuum-packaged meats

often display objectionable odors and may be spoiled. (c) Off-odors

generally associated with aerobically stored meats and some

vegetables. (d) Almost all food products display obvious signs of

spoilage. Slime is common on

aerobically stored meats. (e) Definite structural changes in product

occur at this stage.

MECHANISM

Meat spoilage is characterized Rise in pH, increase in bacterial numbers, incraese

hydration capacity of meat proteins

At refrigeretion temp: Psychrotrophic bacteria

Pseudomonas-shorth generation time

Brochothrix thermosphacta also utilizes glucose and glutamate-short generation time

Use glucose first and then amino acids

When simple sugar finished (108/cm2) Aeromonas, Acinotobacter, Alcaligenes, Morexalla, Serratia

and Enterobacter , Pseudomonas utilise amino asids

• Produce methyl sulfide, esters and acids

The spoilage of meats at low temperature Off odor known as putrefaction -108

Pseudomonas, aeromonas, proteus, Clostridium produce proteolytic enzymes

Anaerobicaly decomposition of proteins

Mercaptan, indole, ammonia, H2S and amines

İndole from tryptophane

H2S from sulfur containing amino asids

decarboxylase

Lysine −−−−−−−−−→ H2N(CH2)5NH2

Cadaverine

decarboxylase

Ornithine or arginine −−−−−−−−−→ N(CH2) 5NH2

Putrescine

Putrescine is the major diamine produced by pseudomonads

cadaverine is produced more by Enterobacteriaceae

The sliminess Masses of bacterial growth

Softening and loosining of meat structural proteins

Alcaligenes, Aeromonas, Acinotobacter, Morexalla, Serratia, Pseudomonas, Lactobacillus, Streptococcus

Souring Formic, acetic, butyric, propionic and lactic acid by

anaerobes

Red spot by Serratia mercescens

Blue color by P. syncyanea

Yellow color by Flovobacterium

Greenish –blue or brownish-black spots by Chromobacterium lividium

The response of several physicochemical meat spoilage tests as fresh

ground beef was held at 7◦C until definite spoilage had occurred. The

arrow indicates the first day off-odors were detected.

ERV = extract release volume; free H2O = measurement of water-holding

capacity (inversely related); Sw = meat swelling;

η =viscosity; and log nos.=total aerobic bacteria/g.

THE EXTRACT-RELEASE VOLUME (ERV) TECHNIQUE

based on the volume of aqueous extract released by a homogenate of beef when allowed to pass through filter paper for a given period of time.

beef of good organoleptic and microbial quality releases large volumes of extract,

beef of poor microbial quality releases smaller volumes or none

DARK, FIRM, AND DRY (DFD) MEATS

pH>6.0

high simple carbohydrates,

spoilage is more rapid

off-odors are detectable with cell numbers around 106/cm2.

INCIDENCE/PREVALENCE OF MICROORGANISMS IN FRESH POULTRY

Whole poultry tends to have a lower microbial count than cut-up poultry.

Most of the organisms on such products are at the surface

Chicken breast muscle spoils

faster than leg muscles

because the leg muscles have a

higher pH

Whole poultry

Cut-up poultry

The reasons that poultry spoilage is mainly on the

surfaces:

1. The inner portions of poultry tissue are

1. generally sterile, or

2. contain relatively few organisms,

1. do not grow at low temperatures.

2. The spoilage biot

1. is restricted to the surfaces

2. Contaminated from water, processing, and handling.

MICROBIAL SPOILAGE OF POULTRY

the primary spoilage organisms : Pseudomonas

Shewenella putrefaciens grows well at 5◦C and produces off-odors in 7 days on chicken muscle.

With chicken leg muscle stored at 2◦C for 16

days,

79% of the biota consisted of Pseudomonads,

17% of Acinetobacter-Moraxella, and

4% of S. putrefaciens

YEAST

Fungi are of considerably less importance in poultry spoilage except when antibiotics are employed to suppress bacterial growth.

When antibiotics are employed, however, molds become the primary agents of spoilage.

The genera Candida, Rhodotorula, Debaryomyces, and Yarrowia are the most important yeasts found on poultry

The essential feature of poultry spoilage is sliminess at the outer surfaces of the carcass or cuts.

The visceral cavity often displays sour odors or what is commonly called visceral taint.

As poultry undergoes spoilage, off-odors are generally noted before

sliminess, off- odors being first detected - 7.2 to 8.0 log10

numbers/cm2.

Sliminess generally occurs shortly after off-odors, with 8.6 log10 counts/cm2

Total aerobic plate counts/cm2 of slimy surface rarely go higher than log10 9.5.

the initial growth first limited to poultry

surfaces,

the tissue below the skin remains free of bacteria

for some time.

Gradually, bacteria begin to enter the deep

tissues,

increased hydration of muscle proteins

CARCASS SANITIZING/WASHING

In an effort to reduce the number and types of pathogens on dressed carcasses and finished products, a number of methods have emerged:

1. Trimming—the excising of skin or outer tissue 2. Washing—the use of plain water at varying

temperatures and hose pressures 3. Organic acids—the addition to wash water of acetic,

citric, or lactic acid at concentrations of 2% to 5% 4. Other chemicals—the addition to wash water of

hydrogen peroxide, chlorine dioxide, or chlorhexidine 5. Steam vacuum treatments—the application of steam

for 5 to 10 seconds at 80◦C or higher as the final carcass preparation step

6. Combinations—the use of two or more of the above