Meat Fermentation

MEAT FERMENTATION (CURING)

• Traditional, empirical methods of improving the shelf life of meat have relied on salting or drying (with or without chopping), or smoking.

• Some methods involve microorganisms, which in addition to increasing the shelf life affect the texture and flavour of the final meat product, called fermented meat products, are represented mainly by fermented sausages.  

• The shelf-life, safety, the specific flavour, texture and colour = acidulation, the lowering of water activity (aw) by the addition of salt (curing) and by drying.

• The role of microorganisms in fresh sausages, cooked sausages and dry-cured ham is limited

• Different varieties of sausage are defined according to their formulation, their area of production and their physical and chemical characteristics.

      Sausages grouped under four major category

•  Fermented sausages or sausages dried in air ( can be consumed without cooking, normal   sausages) Ham ( from pork )—- equivalently pastırma ……prepared from uncooked materials

• Boiled sausages …..prepared from uncooked materials but during processing either boiled in water or treated with steam …frankfurter, salami ( in Turkish sosis, salam..)

• cooked sausages

• fried sausages

                Fermented Sausages

• classified as semidry or dry sausages.

• mincing and mixing lean and fat meat with additives (e.g. nitrate, nitrite, NaCl, ascorbate) and seasonings (e.g. sugar, garlic, pepper).

• The meat mixture is always stuffed into casings, which can be natural (i.e. gut) or artificial (e.g. collagen) and which are available in a range of diameters.

• the products are fermented and air-dried.

• the desired characteristics are obtained by:  temperature, humidity and air velocity, to the intrinsic parameters, such as fat content, sodium content, degree of comminution and the nature and diameter of the casings.

Semidry sausages (in USA) : by rapid fermentation at an elevated temperature, either without drying or with a short period of drying followed by cooking (at 60–68°C) at the end of fermentation. Traditional Mediterranean products have a slow ripening process, which allows the development of moulds and yeasts on the surface. In northern and central Europe, fermentation is generally combined with smoking, preventing the
development of yeasts and moulds, and the drying period is shorter.

Microbiology of Fermentation

•  naturally contaminated with Lactobacillus, Carnobacterium, Micrococcus, Staphylococcus, Pseudomonas, Acinetobacter, Enterococcus, Arthrobacter, Corynebacterium, Brochothrix and Listeria, and also Enterobacteriaceae, yeasts and moulds.

Spoilage Bacteria

• Gram-negative aerobic microorganisms (e.g. Pseudomonas, Acinetobacter) may be involved in the spoilage of the products, due to their proteolytic activity and/or the catabolism of sulphur-containing amino acids, which cause defects in texture and flavour.

• these disappear through the fermentation period.,

Pathogenic Bacteria

• many pathogenic bacteria, including Clostridium, Staphylococcus aureus, Listeria and Enterobacteriaceae (including Salmonella) is easily controlled if good practice is applied during the processing of the sausages .

Desirable Flora

• lactic acid bacteria are generally the dominant bacterial flora .

• NATURAL ONES:  Lactobacillus curvatus, L. sakei, L. plantarum, L. viridescens, Carnobacterium divergens, C. piscicola and Leuconostoc

• Pediococcus is only found when inoculated as a starter culture.

•  Carnobacterium is present during the fermentation period, but disappears afterwards.

      In dry sausages with a pH above 5, Staphylococcus  warneri, S. saprophyticus, S. sciuri, S. cohnii, S. epidermis, S. xylosus and S. carnosus.

• During drying, yeasts (Debaryomyces hansenii, Candida, Kluyveromyces, Hansenula) and moulds (Penicillium, Aspergillus, Mucor, Cladosporium) are commonly found growing on the casings of sausages, mainly those made in southern Europe, which are ripened over a long time.

• Some  Mediterranean type sausages have moulds on the surface, usually strains of Penicillium nalgiovense, P. chrysogenum and P. camenberti, used as starters mainly to prevent growth of other mycotoxin-producing moulds and give a typical white colour on the surface.

• They may also contribute to flavour development through proteolytic, lipolytic and deaminase activity, and, more likely, through β-oxidation of free fatty acids and may delay rancidity by consuming oxygen.

Starter Cultures for Fermented Sausages

• The LAB used in starter cultures belong to the species Lactobacillus sakei, L.curvatus, (18-25C) L. plantarum, Pediococcus acidilactici and P. pentosaceus. ( 35-40 C)

• Yeasts (Debaryomyces hansenii, Candida famata) and moulds (Penicillium nalviogense, P.chrysogenum or P. camemberti) are added to the surface of the casing.

• microbial activity is also used for the ripening and improving dry-cured hams and bacons.

                 The Processing of Fermented Sausages

• The industrial production ( ‘ripening’) : fermentation followed by drying.

• differ mainly in the length of the total ripening period in relation to that of the fermentation period.

• High initial rates of LA production due to  use of LAB starter  and/or high temperatures during fermentation are associated with short drying periods.

• summer sausage’,  fermented at 38 °C and no drying.

Northern type sausages (NS) : ripened for short periods (up to 3 weeks) and are usually subjected to smoking.

Mediterranean sausages (MS): ripened for longer periods (several weeks or even months) and smoke is not so typically applied. Shelf-life is mostly due to drying and reduced water activity.

                                                      Raw Materials and Additives

• Chilled meats (frozen meat tempered to  −4 °C) and frozen (≤18 °C) porcine fats are most often mixed in a ratio of 2:1.

• ( pH should be 5.8 or lower because higher pH values favor the growth of undesired or hazardous acid-sensitive bacteria)

• salt (2–4%) containing sodium nitrite (NaNO2) (added as curing salt containing 0.4–0.6% NaNO2),

• Sodium chloride is the salt most commonly used in brine solution, and its usage level varies with the type of product being 1–2% in sausages, 2–3% in hams, 1.2–1.8% in bacon and 2–4% in jerkies.

• About 0.4–0.7% of potassium chloride on a finished-weight basis is used in low-sodium meat products, but it may impart a bitter and metallic flavour if used at >0.75%.

• As the use of salt from the sea, desert and rocks in preservation of meat spread, it was found that only certain types of salt helped in developing a desirable pink colour and a special flavour in cured meat.

• Investigations in the nineteenth century revealed that sodium nitrate, present as an impurity in these salts, was the precursor responsible for developing the characteristic colour and flavour in cured meat.

• Further, it was reported that nitrite, which was produced by microbial reduction of nitrate, was responsible for the curing effect.

• the reaction of haemoproteins with nitric oxide derived from nitrite was the chemical basis for the colour of cured meats.

• glucose (0.5–1%) table sugar (sucrose), brown sugar, dextrose, glucose solids, corn syrup solids and lactose can be added at different levels mainly to impart flavour and moderate the harshness of salt in certain products.

• Addition of reducing sugars (e.g. glucose solids, dextrose) to the brine also helps in browning reactions during thermal processing to produce a desirable colour and a caramel flavour in some products such as bacon.

• 1–2%, are added to the brine during various commercial operations in order to lower the water activity of meat during curing

Ascorbates/Erythorbates(isoascorbic acid)

• sodium ascorbate or ascorbic acid (0.5–1%) ( to prevent oxidation, improve color stability)

• The primary function of ascorbic acid may be in reducing metmyoglobin to myoglobin, thus accelerating the overall curing reaction.

• ascorbic acid also helps in the production of nitric oxide (NO) from nitrite .

• Besides their role in colour development, ascorbates and erythorbates have been shown to block the formation of carcinogenic N-nitrosamines in cooked cured meats (particularly in bacon).

• The USDA FSIS regulations permit the addition of 550 ppm /100 lbs of chopped meat , ascorbic or erythorbic acid

Seasonings (spices)

• Different types and levels of seasonings are used.

• The most common flavourings used in brine preparation are extracts from pepper, cloves (karanfil), allspice (yenibahar)and cinnamon.

• Garlic and onion flavourings may also be added.

• An aqueous smoke solution is sometimes introduced into the curing pickle to provide a smoked flavour.

• certain spices and herbs used as seasonings act as antioxidants by reducing the rate of oxidative rancidity development in cured meats.

Sodium Nitrite/ Sodium Nitrate

• sodium nitrite (or nitrate) is the most important cure additive responsible for the typical colour and flavour associated with cooked, cured meats.

• provides oxidative stability to meat by preventing lipid oxidation and helps in controlling the development of warmed-over flavour in cooked, stored meats.

• Nitrite also serves as a vital bacteriostatic agent for control of the outgrowth of Clostridium botulinum, particularly under conditions of product mishandling.

• addition of sodium nitrite to meat and meat products is highly regulated owing to the possible risk of formation of N-nitrosamines.

• In Canada,the maximum allowable limit for the use of sodium nitrite, potassium nitrite or their combinations in preserved meat and meat products: 200 ppm (20 g per 100 kg;

• In the United States, in all products except bacon: 200 ppm;

• Residual nitrite levels in the finished pumped bacon may not exceed 40 ppm.

• For Mediterranean type sausage part or all of the nitrite is substituted for by potassium nitrate (KNO3which needs to be reduced by Micrococcaceae to form the nitrosylating
NO
bacteria inhibited by pH values below 5.2. This hampers their use in Northern processing technology.

• Ground pepper (0.2–0.3%) ( Mediterranean :1–3%, and paprika and garlic …. effective antioxidants). 

Additional additives for Northern type sausages

                Phosphates (0.5%)

• Phosphates and polyphosphates are used primarily to increase the water-holding capacity of cured meat products.

• Alkaline phosphates increase the pH of the meat and also help in solubilizing muscle proteins in order to impart the water-retention action.

• In addition to increased water binding (i.e., increase in product yield), phosphates improve the cured meat flavour by retention of natural juices and by reduction of oxidative rancidity.

•  They also help improve retention of the cured meat colour.

• Phosphates: sodium pyrophosphate, monosodium phosphate, sodium hexametaphosphate, disodium phosphate, sodium tripolyphosphate and sodium pyrophosphate, as well as mono- and dipotassium phosphate, potassium tripolyphosphate and potassium pyrophosphate.

• Tripolyphosphates and their combinations with hexametaphosphates are the most widely used phosphates for cured meat cuts, as they provide the proper pH, good solubility, calcium compatibility and a high degree of the protein modifying effect.

• glucono-δ-lactone (GdL, 0.5%) to ascertain fast chemical acidulation with negative effects on flavour development;  (GdL) is only used for products with a short shelf-life ( because many strains of lactic acid bacteria ferment this compound to lactic and acetic acid acetic acid interferes with reactions leading to and stabilizing desired sensory properties.)

• manganese sulfate (˜50 ppm) as cofactor for lactic acid bacteria;

• vegetable proteins (mainly soya isolate), which may also accelerate fermentation.

             Comminution or Chopping

• Raw materials and additives, including microbial starters, are added for mixing and chopping, often under vacuum, in a mincer or ‘cutter’.

• The cutter consists of a set of knives that rotate rapidly (1–3 × 103 r.p.m.), producing a batter in a bowl that rotates slowly (10–20 r.p.m.)

• The relative speeds of the knives and bowl and the sequence of addition of raw materials and additives determine the fat particle size and are optimized to produce a batter within less than 5 minutes at temperatures ≤2 °C, ensuring minimal damage to the fat tissue.

Stuffing

• the batter is immediately stuffed under vacuum into natural, semisynthetic (collagen) or synthetic casings that are permeable to water and air, and both ends are clipped.

• The sausage diameter (e.g. 2–15 cm) is related positively to the relative importance of fermentation (pH) versus drying (aw) for stability.

                   SAUSAGE CASINGS      

Animal Casings

• the oldest of our packaging materials for sausage: the animal casing.

• As in the case of all collagen materials, the collagen is hardened and rendered less soluble by the application of salt.

• Initially, as the collagen is exposed to heat and drying, it becomes less permeable to moisture.

• the initial step in the processing of a sausage in animal casings requires drying to develop the appropriate smoke permeability.

• The sheep casings are the smallest in diameter and are also the tenderest.

• These are the most adaptable to fresh sausages, where there is no further processing to tenderize the casing, as well as to small-diameter cooked and smoked sausages.

                               Manufactured Collagen Casings

• Manufactured casing made from the same material chemically as the animal casing that is collagen.

• The manufactured collagen casing: any source of collagen could be used

• The collagen is solubilized and later extruded and hardened

Alginate Casing

Cellulose Casings

• Cellulose casings are made from regenerated cellulose derived from high-grade wood pulp.

Plastic casings

• In some cases, a moisture-impermeable material such as PVDC, Mylar, polyethylene or a polyamide (Nylon) is used as a casing.

• cost-effective but they may have drawbacks such as dimensional instability.

Ripening

• The sausages are hung in racks and placed in natural or, mostly, air-conditioned fermentation chambers at high relative humidity (RH).

• ripening in two consecutive stages:

A) Fermentation for bacterial growth

– Northern (20–26 °C/50–90%/62 h)

Mediterranean (5–24 °C/10–90%/100 h)

B) Transfer to another chamber, drying for development of sensory characteristics.

• air RH values not more than 0.10 points below the associated aw values of the sausage, to prevent case hardening, and recommended air speeds are approximately 0.1 m s-1.

Smoking

• After fermentation ,

• Northern type: subjected to smoke( controlled combustion of oak wood (300–600 °C) to minimize the production of polycyclic hydrocarbons.

• Smoke: antimicrobial,antioxidant effects, generates specific flavour and colour components

Sausage Metabolism and Safety (by the introduction of  ‘hurdles’ for undesirable mo.)

• The lowering of the redox potential ( omission of oxygen by chopping under vacuum,  addition of ascorbic acid or ascorbate). This inhibits aerobic bacteria and improves the bactericidal effectiveness of nitrite, a major hurdle.

• production of lactic acid ( pH drop), acetic acid, hydrogen peroxide, bacteriocins.

• Drying, addition of salt ( reduction in the water activity, aw <0.92 or <0.94 at pH <5.0).

• smoke in Northern type production, ensures stability and safety.

• The use of starters that are amino acid decarboxylase-deficient and contain antioxidant enzymes ( to ensure the absence of amine formation and undesirable lipid oxidation, respectively. )

•  undesirable moulds on the sausage exterior is prevented by pretreatment of the casing with potassium sorbate or pimaricine solutions.

Typical Defects and Their Causes

• Surface is blurred, fat particles cannot be seen distinctly: temperature of the fat was not low enough during comminution, blending and stuffing.

• Sausage is deformed: too rapid drying, case-hardening, smeared fat under the casing.

• Discoloration of the surface: too high smoking when the surface is wet; smoking with high RH; ripening with RH.

• Discoloration inside: insufficient curing salt; insufficient oxygen removal during comminution and stuffing; too old (rancid) fat.

• White spots (yeasts) or moulds on the surface: inefficient drying; ripening room is contaminated with yeasts and moulds.

• Too acidic taste: too high carbohydrate concentration; higher than necessary temperature (starter culture-dependent), starter culture-specific (production of acetic acid in addition to lactic acid).

• Poor sliceability: unsatisfactory pH-drop and/or aw drop; fat smearing inhibits binding; chemical acidulants react too early (before stuffing).

• Spoilage on the surface: under high humidity conditions micrococci, yeasts and moulds can grow causing characteristic off-odours (microorganism-dependent).

• Spoilage inside: too slow drying at elevated temperature; too low initial salt concentration; highly contaminated ingredients; failure of the starter culture; too high initial pH of the meat; too low carbohydrate concentration; insufficient oxygen removal.

MEAT  CURING  ( salamura, pastırma ——-ham( from pork))

Dry curing:

• Meat rubbed with cure mixture (50 kg salt+ 0.5 kg nitrate + 1 kg sucrose )àtheb rubbed with sat àput in to cask and press for 1-2 days.

Wet curing:

• Mixture of (100 kg water+24 kg salt+1 kg nitrate salt + 2 kg sugar ) àboiledàcooled   ( 5 C )àpoured in to cask which is containing meatàlater wash the meat with hot wateràthen put in to cold water (10-30 m)

• ( NO3( nitrate ) —-NO2 (nitrite)

• 3NO2 + GDL ————- 2NO + HNO3 + H2O

• NO + Myoglobin —- nitrosomyoglobin ( color stability)

Pastırma

The Turkish horsemen of Central Asia used to preserve meat by placing slabs of it in pockets on the sides of their saddles, where it would be pressed by their legs as they rode.

This pressed meat was the forerunner of today’s pastırma, a term which literally means being pressed in Turkish, and is the origin of the Italian pastrami.

Pastırma is a kind of cured beef, the most famous being that made in the town of Kayseri.

• series of processes  about a month.

• Fresh meat rests at room temp. for 4-8 hours before being divided.

• salted on one side, stacked, and left for around 24 hours.

• salted on the other side, stacked and left for a further 24 hours.

• rinsed in plenty of water to remove the excess salt

• dried in the open air for a period varying between 3 and 10 days.

• further processing, the meat is hung up to dry again( in the shade and spaced out so that the joints do not a touch one another.)

• After 3-6 days, they are covered with a paste of ground spices known as çemen(Trigonella foenum groecum  ( buy otu tohumu ) seeds, garlic and chilli pepper mixed to a paste with a little water. ) , and left to cure for 10-24 hours in hot weather, and 1-2 days in cold weather.

• Then the excess çemen is removed, leaving a thin layer, and the joints dried again. Finally the pastırma is ready for the table

• Gourmets do not approve of pastırma sliced by machine but insist on the thin slices being cut by hand with a sharp meat knife. They also reject ready cut slices of pastırma as sold packaged in some delicatessens and supermarkets

Making Salami

• Ground meat+spices(garlic,redpepper,black pepper, fennel seed)+salt+starter culture(Pediococcus cerevisiae and Lactobacillus plantarum. )Curing, IncubatingDrying  (totaly around 3 weeks)

Curing : refrigerate for 2 days and

incubate at 28-30 C, 90% RH

Drying: The temp. during this phase is generally 10-15 C and RH 70-80%.  The maintenance of this high  humidity is necessary to prevent case hardening. During this time, the casing of the salami will mold. This is natural and some say it imparts complexity to the flavor of the salami

Frankfurters

• This product is believed to originate from Frankfurt, Germany in 1487.

• The frankfurter name is often used interchangeably with frank, wiener and hot dog.

• Frankfurters are typically 20–25 mm in diameter and are linked in  12.5 cm lengths.

• a natural casing or a cellulose casing.

• Hot dogs (Hot dogs were first seen in the late 1800s, at baseball games in the Unites States ) are typically smoked.

• The cellulose casing is removed before packaging of this product, which results in what is called a skinless product( over 95% of total)

• 80-90 % lean meat + 10-20 % fat + 5 % potato starch + 0.2-0.4 % red pepper + 0.2-0.4 % black pepper + 0.5 % sugar + 0.05 % nitrate + 0.02 % nitrite + 0.03 % ascorbic acid + 2.5 % salt + 20-30 % water as ice

• Process: 

–meat + salt + nitrate + nitrite

–mix and grind

–rest (-3 C, 12 hours to increase water holding capacity)

–add remaining spices and ice

–grind

–add fat

–add ascorbic acid

–fill to casings

–dry at 40 C, 15-20 minutes

–smoking (75-78 C, 35-45 minutes, horn beech wood or oak wood is used

–phenol and phenol aldehyde is produced to have antimicrobial and antioxidative effect) 

–dip into water , 80 C, 15-20 minutes

–treat with cold waters

–ready to sell

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