Iycee Charles de Gaulle Summary Microbial Growth In Fermented Sausages Biology Essay

Microbial Growth In Fermented Sausages Biology Essay

Definition of Fermented Sausages: Fermented sausages can be defined as a mixture of chiefly meat, fatty tissue, bring arounding agents, salt, nitrite, sugar and spices, filled into shells and left for a agitation or maturing procedure to take topographic point, before dried. ( FAO 1985 )

Fermented Sausages Ecosystem:

Fermented sausage merchandises are made with different sorts of meat every bit good as by different production engineerings. The best meat that may be used to fix sausages is that from grownup animate beings, particularly beef or porc. Both of these contain high degrees of myoglobin, a protein found in the musculus cells, which has the ability to offer singular coloring material to the production of dry and semi-dry fermented sausages. Other standards have to be considered when choosing meat for doing sausages, such as pH value ( the grade of sourness or alkalinity ) and the composing and binding belongingss. Furthermore the fat has to be fresh, white and with low polyunsaturated fatty acid.

While Na chloride ( NaCl ) is ever added to the production of fermented sausages at degrees between 2.5 % and 4 % , other additives such as nitrate and nitrite are used at degrees runing from 150 to 250 ppm ( parts per million to H2O ) , depending on the ordinances of the state ( Honikel, 2008 ) . Sugars normally used for the production of fermented sausages are sucrose, dextrose, lactose and glucose. Out of these, the most of import sugar, which is ever used in the dry fermented sausages, is lactose. In add-on, some spices are used in the industry of fermented sausages such as garlic, pepper and paprika.

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In drumhead, the production of dry fermented sausages is based on three stages:

The combination of shredded meat blended in with other ingredients such as salt, nitrite or nitrate, sugar and spices.

The mixture is put into shells, followed by the agitation procedure.

Finally the maturation and drying is completed.

However, two microbic reactions ( interdependently and at the same time ) will besides go on through the period of agitation.

The decrease in the pH degrees throughout glycolysis by lactic acid bacterium every bit good as the creative activity of azotic oxide causes a decrease of pathogens like ( CNC ) coagulase-negative coccus, including Micrococcus and/or Staphylococcus aureus.

Some additives such as sugar, Na chloride, nitrite/ nitrate and the presence of intrinsic factors such as H2O activity ( 0.85 – 0.92 ) and extrinsic factors such as the degree of temperature ( 24-300C to 12-18 0C ) throughout maturing, will intensively choose the microbiota which have the ability to better in this ecological niche.

There are several species of lactic acid bacteriums used in traditional fermented sausages, such as Lactobacillus plantarum, L.curvatus, L.sakei and Pediococcus spp. The latter are the most of import species, normally isolated among lactic acid bacteriums because they have the ability to accommodate in terrible conditions. ( Mozzi et al. 2010 )

Categorization of Fermented Sausages:

The categorization of fermented sausages depends on a scope of standards like H2O activity value ( aw ) , wet content, ( M: P ) wet protein ratio, comminution grade of fat and meat and weight loss. The H2O activity value is the footing of separating dry and semi-dry fermented sausages ( Incze 2004 ) . The concluding H2O activity value can be determined by the combination of the initial wet protein and wet in the salt content, every bit good as by the period of drying. On the other manus, the wet protein ratio has the ability to give information in relation to the extent of waterlessness of the meat. On this footing, the concluding content of the wet protein ratio should be 2.0 to 1 and the concluding H2O activity values between 0.90 and 0.91 or less ; these rates should be used as the boundary line for the industry of semi-dry and dry fermented sausages. The considerations of these parametric quantities are of import for set uping the shelf-life and safety of the merchandise for ingestion. ( Toldr & A ; aacute ; 2010 )

Types of Fermented Sausages:

Dry Sausages ( Slow Fermentation )

Dry fermented sausages can be defined as land meat or a category of shredded meat merchandises that, as a consequence of microbic accretion ( LAB ) , reach a pH of 5.2 to 5.8 or less. This type of sausage is considered to be safer than others as consequence of a long drying procedure ( 3 to 4 months ) at a low temperature ( 12 to 16 0C ) with optional cold fume. It has a concluding H2O activity aw scope of 0.88 and about a 30 % weight loss. Just a little measure of sugar is used in this type of processing, approximately ( 0.1 to 0.3 ) . The pH will diminish somewhat and easy. ( Marianski. S, Marianski. A 2009 ) , as consequence of the content of lactic acid, runing from 0.5 to 1.0, which is lower than in semi-dry sausages. The wet content is less than 30 % with a wet protein scope of between 2.3 and 1. ( Toldr & A ; aacute ; 2010 ) .

The hardening procedure is ever applied in the dry fermented sausage particularly before the lactic acid civilizations are added ; if the starting motor civilizations have been added, the bring arounding procedure will non happen. After the hardening procedure, the ingredients of the sausage are stuffed into shells and so placed in a agitation chamber. The sourness of the meat will increase bit by bit as a consequence of the metamorphosis of sugar by the lactic acid bacteriums. The uninterrupted drying procedure in coaction with the sourness of the meat generates an environment hostile to harmful bacteriums and preventive of its growing. ( Marianski. S and Marianski. A 2009 )

Meat and fat choice at ( 40C )

Blending at ( 8-120C ) in the absence of air


Agitation at 16-200C, 3-8days

Smoking ( optional )

Heating ( optional )

Drying ( 12- 160C for 6-8weeks

Boxing for retail distribution

figure1. Flow diagram of the procedure of dry fermented sausage adapted from ( pp. 53 ) ( Marianski S and Maria & A ; ntilde ; ski A 2009 )

Semi-dry Sausages ( Medium or Fast Fermentation )

Semi-dry fermented sausages are a land meat merchandise or shredded meat that, as consequence of lactic acid bacteriums action and the content of lactic acid runing between 0.5 % and 1.3 % , reaches a pH of ( 4.8- 5.3 ) . The chief method used for this type of agitation is acidification to drop the pH degree nevertheless, it is of import to add dextrose ( glucose ) to the ingredients of sausages, to back up a fast pH bead. The smoke every bit good as cooking procedure for semi-dry fermented sausages takes topographic point in the meat house with the heat at 60 0C. After the smoke procedure, the sausages might necessitate drying for a short clip.

The H2O activity values of the concluding merchandises are ranged between ( ?0.90 and 0.91 ) , which is much higher than dry fermented sausages and the weight loss of these merchandises is about 15 to 20 % . ( Toldr & A ; aacute ; 2010 )

The agitation procedure in the production of semi-dry sausages can be made in two ways ; by adding the starter civilization direct or by utilizing the traditional manner.

On the one manus, fast fermented sausages require about one to two yearss of agitation clip to drop the degree of pH to ( 4.8 ) . On the other manus, medium fermented sausages require two to three yearss of agitation clip to drop the pH to ( 4.8 to 5 ) . In fact, these times of agitation processing are based on the starting motor civilizations that are used. There are several of import factors that should be considered during the industry of semi-dry fermented sausages, such as the measure and type of sugar used, fermentation temperature and extra additives like citric acid every bit good as GdL. ( Marianski. S, Marianski. A 2009 )

Meat and fat choice at ( 40C )

Blending at ( 8-120C ) in the absence of air

Stuffing ( under vacuity )

Agitation at 25-30 0C, 1-2days. RH 70-95 %

Drying 5- 160C for 2-40 yearss

Smoking at 22- 60 0C

Boxing curried out under modified ambiances or vacuity


Figure2. Flow diagram of the processing of semidry fermented sausage adapted from ( pp.385 ) ( Toldr & A ; aacute ; 2010 )

Water Activity in the Dry and Semi-Dry Fermented Sausages:

All micro-organisms including bacteriums, viruses, molds and barms require H2O to turn and multiply and the handiness of this H2O for them is defined as H2O activity. ( Marianski S and Maria & A ; ntilde ; ski A 2010 ) .

Harmonizing to the Food Agriculture Organization of the United Nations, the term of H2O activity has been defined in the industry of dry fermented sausages as the quotient of the vapour force per unit area nowadays in the meat and the impregnation vapor of the pure H2O at the same temperature.

( PS / Po )

The H2O activity ( aw ) value in traditional industry of dry and semi-dry fermented sausages is decreased by smoking, drying and/or the bring arounding procedure by adding some preservatives such as salt, sugar and spices. The salt, H2O and fat contents of the sausage besides have a direct consequence on the province of ( aw ) . By adding one per cent of salt, or Na chloride ( NaCl ) the H2O activity value can be reduced by 0.0060 and one per cent of fat reduces about 0.00045 of the H2O activity value. In the same mode, the add-on of 1 per cent of sugar can cut down the ( aw ) value by about 0.0025, whereas the add-on of soy protein reduces the H2O activity degree by between 0.0012 and 0.0013. Ingredients used for doing sausages include meat with 30 per cent of fat, assorted with 2 per cent sugar, 3 per cent of Na chloride and 2 per cent of soy protein. The initial degree of H2O activity in the primary merchandise of thin meat, of 0.99 is so reduced to 0.9521 by these additives, while the H2O losingss by vaporization and the warming grade control the concluding H2O activity. In add-on the generation of barm every bit good as bacteriums can be inhibited at H2O activity value below 0.88 to 0.90, ( Food and Agriculture Organization, 1985 ) .

Figure3. Minimum H2O activity values for the growing of micro-organisms

Hazards of Pathogenic Bacteria that have to be Controlled in the Dry and Semidry Fermented Sausages Production:

Escherichia Coli:

The strains of verotoxigenic E. coli including different serotypes like O157: H7, O103: H25 and O26: H11. These serotypes have the ability to happen in the dry fermented sausages even with low ( aw ) values every bit good as low pH degree, and the caused eruptions of these serotypes in the dry fermented sausages were occurred in many states.

( Heir et al 2010 )

However, the most common serotype of ( VTEC ) occurs in the dry fermented sausages is E. coli O157: H7 and the first caused outbreak relating to E. coli O157: H7 in dry and semidry sausages was reported in 1994 ; 17 persons consumed these merchandises.

It is of import bear in head that the procedure of dry fermented sausages is able to cut down in viability of E. coli O157: H7 at degree ? 5log CFU/g. On the other manus, some additives such as sinapis alba mustard and Brassica juncea mustard have ability to extinguish E. coli O157: H7 in the dry fermented sausages because they contain high degrees of glucosinotates. ( Luciano et al 2010 ) .

Staphylococcus Aureus:

Staph. aureus has ability to do nutrient toxic condition by bring forthing toxins in meat ( enterotoxin ) . It besides has ability to turn in broad scope of temperatures, between 7 to 460C and can turn at pH degrees 4.5 to 9.3 ( the optimum pH degree is 7 ) . Furthermore, it has ability to turn at low aw values and 0.86 of aw has been considered the minimal degree for growing. The optimal value of aw is considered to be ? 0.90 and the production of enterotoxin can be produce at aw value 0.87. ( Lowley et al 2008 ) .


The Enterobacteriaceae of salmonella has a broad distribution on meat. There are several factors that can promote the growing Salmonella in the dry fermented sausages such as, high degree of pH, high ( aw ) value, high temperatures through the maturation procedure and low degrees of lactic acid. In many types of sausages, salmonellosis can ensue in eruptions. For illustration, in Germany, the spreadable sausage was contaminated with salmonella due to high degree of aw, a little sum of GdL and a small sum of sugar was added to the production and The intent of this procedure to retain the meaty gustatory sensation, every bit good as fresh consistence of the merchandise. ( Lund et al 2000 ) .