SPOILAGE IN MEAT AND MEAT PRODUCTS

Transcription

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

2 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.

3 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

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

5 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

6 3.GASTROINTESTINAL TRACT Intestinal contents with microorganisms contaminate the surface of carcasses Rumen of ruminant animals, which typically contains bacteria per gram

7 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

8 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.

9 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

10 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.

11 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.

12 (MYOSIN FLAMENT)

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14 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.

15 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.

16 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

17 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

18 FACTORS EFFECTING CONTAMINATION

19 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

20 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

21 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

22 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.

23 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.

24 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.

25 The development of off-odor and slime on dressed chicken (squares) and packaged beef (circles) during storage at 5 C.

26 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 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.

27 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 (10 8 /cm2) Aeromonas, Acinotobacter, Alcaligenes, Morexalla, Serratia and Enterobacter, Pseudomonas utilise amino asids Produce methyl sulfide, esters and acids

28 The spoilage of meats at low temperature Off odor known as putrefaction Pseudomonas, aeromonas, proteus, Clostridium produce proteolytic enzymes Anaerobicaly decomposition of proteins Mercaptan, indole, ammonia, H 2 S and amines İndole from tryptophane H 2 S from sulfur containing amino asids

29 decarboxylase Lysine H 2 N(CH 2 ) 5 NH 2 Cadaverine decarboxylase Ornithine or arginine N(CH 2 ) 5NH 2 Putrescine

30 Putrescine is the major diamine produced by pseudomonads cadaverine is produced more by Enterobacteriaceae

31 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

32 Red spot by Serratia mercescens Blue color by P. syncyanea Yellow color by Flovobacterium Greenish blue or brownish-black spots by Chromobacterium lividium

33 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.

34 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

35 DARK, FIRM, AND DRY (DFD) MEATS ph>6.0 high simple carbohydrates, spoilage is more rapid off-odors are detectable with cell numbers around 10 6 /cm2.

36 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

37 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.

38 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

39 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

40 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.

41 As poultry undergoes spoilage, off-odors are generally noted before sliminess, off- odors being first detected to 8.0 log10 numbers/cm2. Sliminess generally occurs shortly after offodors, with 8.6 log10 counts/cm2 Total aerobic plate counts/cm2 of slimy surface rarely go higher than log

42 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

43 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