In this article we will discuss about the Sausage Fermentation:- 1.Process of Sausage Fermentation 2. Commercial Cultures of Sausage Organisms 3. Action of Sausage Organisms 4. Inhibition of Staphylococci in Sausage Fermentation 5. Economical Production of Sausage.
- Process of Sausage Fermentation
- Commercial Cultures of Sausage Organisms
- Action of Sausage Organisms
- Inhibition of Staphylococci in Sausage Fermentation
- Economical Production of Sausage
1. Process of Sausage Fermentation:
The process of fermenting sausage was probably one of the earliest forms of meat processing. Salting fresh meat and curing fresh meat by drying were man’s earliest attempts at food preservation. Sausage manufacturing probably began before written history.
The first mention of sausage manufacturing in written history was in the 9th century, B.C., when it was mentioned in Homer’s Odyssey. The sausage was called oryae. The play Orya by Epicharmus about 500 B.C. mentions oryae. The word salami was probably coined from the product made in Salamis, Cyprus, a city destroyed in 449 B.C.
Sausages eaten by the Babylonians, Greeks, and Romans were no doubt fermented and dried meat products. Brested (1938) stated that Caesar’s legions in Gaul consumed dry sausages. Descriptions of the process of making sausages confirm that many types of dry sausages were eaten by the Babylonians, Greeks, and Romans.
Pederson (1979) has written an excellent review of the history of sausage uses and manufacturing. The various regions of the Mediterranean developed characteristic sausages, as shown by the salamis known as Genoa, Milano, and Lombardi. The Mediterranean countries consumed a highly seasoned, non-smoked product classified as the Latin type.
The Northern European countries developed a form of the Roman product, but slightly spiced, heavily smoked, moist, and higher in salt content. This product is often referred to as the Germanic type. In the colder areas of Europe sausage was made in the winter months, stored, and aged until the summer; hence it was called summer sausage.
There is little doubt that these sausage products were heavily inoculated with indigenous flora prompting the growth of lactic acid bacteria, yeasts, and mold in and on the surface of the sausage. Surface growth of mold on sausage yields a unique product in several areas of the world.
Early in the 20th century, bacteria were discovered to be responsible for- (1) lactic acid production and (2) nitrate reduction in sausages. The contribution of bacteria to sausage production was considered comparable to the changes brought about in the manufacture of cheeses.
Jensen and Paddock (1940) used various species of lactic acid bacteria to standardize and improve the character of sausages, and were the first to be issued a U.S. patent for sausage fermentation. They showed in their patent that several species of Lactobacillus could be used as starter cultures.
Jensen (1942) found that the pleasant acid tangy character of Thuringer style sausage is formed by several species of Lactobacillus and Leuconostoc. He summarized his work by saying (1) chance inoculation by indigenous bacteria is not economical, and (2) processes for semi-dry sausages could be shortened.
The European process for making sausage required the use of nitrate instead of the common use of nitrite. Niinivaara (1955) isolated a culture from meat, Micrococcus aurantiacus (M-53), which reduces nitrate to nitrite and shows inhibition of other meat flora. A sampling of the microbial population of fermented sausage is shown in Table 7.1.
The sausages were sampled from the marketplace and analyzed for lactic acid bacteria. The predominant species was Lactobacillus plantarum. The colonies spotted on Baird-Parker medium were typically coagulase-negative micrococci or staphylococci. Sausages containing high levels of Pediococcus were fermented with starter cultures.
2. Commercial Cultures of Sausage Organisms:
Deibel and Niven (1957) reported use of the bacterial species, Pediococcus cerevisiae, as a starter culture for the semi-dry summer sausage. P. cerevisiae is a true lactic acid organism belonging to the Streptococcaceae family and differs substantially from other Gram- positive cocci of this family. Its optimum temperature is 43°C, and it grows well in 5-7% saline medium. Everson et al. (1970) stated that its classification as P. cerevisiae was erroneous, and it was reclassified as P. acidilactici.
Deibel et al. (1961B) showed that the ultimate aim of using a starter culture is to gain greater control of the fermentation. They developed lyophilized cultures of P. cerevisiae which performed satisfactorily under United States manufacturing conditions, and the use of P. cerevisiae was approved by the U.S. Dep. of Agriculture.
This culture was first marketed under the name “Accel”. The first commercial starter culture in Europe was the “Bactoferment” (M. aurantiacus) after Niinivaara (1955). It was augmented by a culture called “Duploferment,” a mixture of L. plantarum and M. aurantiacus, in 1966.
In 1971 Rothchild and Olsen were issued a patent describing the process of making sausage using frozen concentrates of P. cerevisiae. In 1976 a U.S. patent was issued to Olsen and Rothchild for a frozen, concentrated bacterial product which maintains viability at -18°C for long periods of storage. This product is sold under the trade name “Lactacel.”
Figure 7.1 shows the growth of lactic acid starter culture in fermenting meats. The pH decreases faster with increasing temperature, and the optimum temperature for fermentation with P. cerevisiae is 43°-45°C. The action of the homo-fermentative organism produces an environment which is excellent for drying (around pH 5.2 to 5.3), and the action of salt and sugars with the lactic acid produces a safe and marketable summer sausage.
The native chorizo-type sausage in the Philippines was studied by Sison (1967). He showed the presence of several strains of Micrococcus, but the fermentation was due to P. cerevisiae, either indigenous or added. Leuconostoc mesenteroides and a Streptococcus strain closely related to S. faecalis were isolated. Lactobacillus brevis was also mentioned as a potential starter culture organism.
The major activity of the lactic acid bacteria is the conversion of sugars, usually glucose or sucrose, to lactic acid by the Embden-Meyerhof pathway. Deketelaere et al. (1974) found that lactic acid was the major acid formed during the fermentation of carbohydrates, with minor amounts of acetic acid, generally about 10 to 1 of lactic to acetic acid. They also found small quantities of butyric and propionic acids. Leuconostoc mesenteroides and Lactobacillus brevis convert slightly less than 50% of the sugar fermented to lactic acid, and a similar amount to ethanol, acetic acid, and carbon dioxide. Streptococcus lactis subspecies diacetylactis produces diacetyl and acetoin which impart a nutty flavor and aroma to some sausages.
Palumbo and Smith (1977) have shown that micrococci dominate the surface of the stuffed sausage during the early stages of the fermentation. These micrococci are killed at pH 5.5 and are not found in the sausages after heat treatments of drying.
The major functions of the micrococci during the fermentation are the reduction of nitrate to nitrite and the production of catalase. Lactic acid bacteria rarely reduce nitrate to nitrite. Staphylococci actively reduce nitrate to nitrite, particularly S. aureus, S. xylosus, and S. epidermidis.
Micrococci are indigenous to all animal species and each species carries a specific flora of micrococci. Excessive nitrite levels in sausage have been noted when using high nitrate concentrations with micrococci, producing a defect in the sausage known as “nitrite burn”.
The micrococci are also lipolytic, and they produce lipase during the early stages of the fermentation. Cantoni et al. (1967) confirmed the action of micrococci on pork fat. There was a dramatic increase in free fatty acids, volatile fatty acids, and carbonyl compounds after 28 days of drying.
Tjaberg et al. (1969) had shown that lactic acid bacteria produce varying amounts of hydrogen peroxide. The micrococci produce catalase which effectively destroys the hydrogen peroxide produced at the surface of the sausage. Haymon and Acton (1978) have summarized the role of micrococci in the flavor development of fermented sausages.
Demeyer et al. (1974) showed increases in free fatty acids and carbonyl compounds in Belgian salami during drying. Triglycerides were partially degraded to free fatty acids and the unsaturated free fatty acids were degraded to carbonyl compounds. The hydrolytic activity was attributed to lipase action of micrococci.
4. Inhibition of Staphylococci in Sausage Fermentation:
Another function of the action of lactic acid bacteria in the production, of sausages is the inhibition of Staphylococcus aureus. In the last 15 years several incidences of food poisoning due to the consumption of fermented meats were reported to the National Center for Disease Control. The inhibition or suppression of Staphylococcus aureus growth also suppresses Enterotoxin A production.
Genigeorgis (1976) has reviewed the competitive aspects of staphylococci with other bacteria in foods. Streptococci and P. cerevisiae were the inhibitoriest to growth of staphylococci and enterotoxin production. Leuconostoc citrouorum and lactobacilli do not inhibit growth and only slightly inhibit production of Enterotoxin B.
The inhibition of staphylococci in sausage is more pronounced as the ratio of lactics to staphylococci increases and as the temperature of fermentation decreases. Higher temperatures (38.9°C is optimum for S. aureus) and brine concentration tend to favor the growth of mesophilic, salt tolerant staphylococci.
The beneficial effect of lactic acid starter cultures in inhibiting or suppressing staphylococcal growth and enterotoxin production in fermented sausages has been demonstrated.
Haymon and Gryczka (1978) have shown that P. cerevisiae limits staphylococcal growth to less than 3 log cycles using 18 hr old broth cultures of S. aureus. Indigenous staphylococci in sausage were limited to less than 2 log cycles of growth at optimum temperatures by P. cerevisiae and Micrococcus varians.
5. Economical Production of Sausage:
The traditional process of fermenting sausages consisted of grinding the meats in some fashion, mixing in sodium chloride and sodium or potassium nitrate, blending in spices and seasonings, and transferring this mixture to curing pans. The meat mixture was tightly packed in layers about 15 to 20 cm (6 to 8 in.) deep and held at 40°C for 48 to 72 hr. During this curing period, nitrate reducing bacteria converted some of the nitrate to nitrite, a substance required for the red cured meat pigmentation reaction.
After stuffing, the sausages were held in a “green” room for 12 to 48 hr at 10°- 15°C. Following the greening the product was moved either to a smoking pit or to a smokehouse for heating and smoking. For dry sausages the green room was followed by drying in a room at ambient temperatures for up to 120 days.
This process for summer sausages has been reduced to 12-24 hr of total processing time since the introduction of starter cultures of P. cerevisiae. Dry sausages are cured or ripened in 24-48 hr with starter cultures instead of the 7-14 days by the traditional process.
Because the sausages are acidified to near their isoelectric point, where they have their lowest solubility, they can be dried more easily at that pH; Drying times for dry sausages such as pepperoni and Genoa have decreased to 25-40 days depending on the caliber of the sausage and on trichinae certification procedures.
The total microbiological population of fermented sausage has changed from chance or random contamination to one of safe and economical production schedules. The fermented sausages in the supermarket are safe from botulism poison and staphylococcus food poisoning, and are wholesome, well defined, processed meat products.