Fermented sausages are meat products that are fermented by adding a certain starter and can be stored for a long time. According to the characteristics of fermented sausages, they can be divided into dry and wet two types. And according to the different maturation time, dry fermented sausages can be divided into short-mature and long-mature two types.

Overview of Fermented Sausages

Fermented sausage refers to the addition of spices, salt, sugar, or other additives to minced meat, which is poured into natural casings. It is processed through natural fermentation, maturation, drying, and other processes under certain temperatures and humidity. And it is meat products that can be preserved for a long time without being sterilized by heating.

To make fermented sausages, we must ensure two aspects: first, to ensure that the product has a long shelf-life; second, to ensure the quality of the product, such as good flavor, taste, texture, and tissue state.

In developing countries, fermented food accounts for 60% of people’s daily food, and it is also one of the common ways to preserve food (including meat). Fermented meat products produced by lactic acid bacteria have a special flavor, which has attracted people’s attention and love. At the same time, because lactic acid bacteria can improve the volatile matter, color, texture, and other factors of meat products, they are widely used in fermented meat products. The famous salami fermented sausage is produced in southern Italy. And in many countries in the world, people use traditional methods to produce many fermented meat products.

Chinese-style fermented sausage is a fermented meat product widely accepted by Chinese consumers. It is ground meat through salt, sugar, sodium glutamate, alkaline phosphate, nitrite, and other seasonings such as white pepper, garlic, etc. It is fermented and matured and has a special flavor, such as Cantonese sausage, Harbin red sausage, and Jinhua ham.

Nowadays, in addition to pork and back fat, some auxiliary materials (such as sweet potato, konjac, chitin) can be added to make new fermented sausages, especially low-fat, low-calorie meat products are deeply loved by people.

Classification of Fermented Sausages

Although there are many types of fermented sausages, according to their characteristics, fermented sausages can be divided into two categories, as below.

1. Wet Fermented Sausage

The fermentation time of wet fermented sausage is relatively short, usually 3 to 5 days, and sodium nitrite is formed during processing. The final moisture content of the product is between 35% and 42%, and the water activity is approximately between 0.95 and 0.96.

In order to reduce product quality problems and color residues in product packaging, the processed raw materials must ensure that the content of microorganisms is low, and a certain amount of carbohydrates must be added during the processing. Smoke and store under the conditions of low temperature and high relative humidity.

In order to reduce the acidity of the product quickly in a short period of time, some chemical acidifiers such as gluconic acid, organic acids such as lactic acid, and other acids can be added during the sausage processing.

2. Dry Fermented Sausage

According to the different maturation time, dry fermented sausages can be divided into two categories, short-mature fermented sausages, and long-mature fermented sausages.

2.1. Short-mature Fermented Sausage

Short-mature fermented sausages are also known as semi-dry sausages, and their maturation time is 1 to 4 weeks. Sausages are marinated with sodium nitrite and sometimes potassium nitrate. Micrococcus is also used as a starter in fermented sausages.

Nowadays, lactic acid bacteria are the main starter of fermented sausages, and a certain amount of sugar and a certain amount of chemical acidifiers such as gluconic acid must be added to the fermented sausage. The use of a starter can improve the microbiological condition of the product, the sensory quality, and extend the shelf life. The moisture content of the final product is between 30% and 40%, and the water activity is between 0.29 and 0.94.

2.2. Long Maturity Fermented Sausage

Long-mature fermented sausages, also known as dry sausages, are more famous all over the world. Such as Chorizo and Salchichón sausages in Spain and parts of the United States, and Salami sausages in Italy. In Europe, fermented sausages have a long history, and some dry fermented sausages have a maturation period of up to 16 weeks. For example, the ripening period of Hungary sausage is 6 weeks and the ripening period of salami is 12 to 14 weeks.

Adding nitrite or potassium nitrate during the curing process can inhibit the growth of certain harmful microorganisms. The initial processing temperature of dry fermented sausage is between 6°C and 15°C, the final water activity reaches 0.85~0.90, and the final moisture content is 20%~30%. Under such conditions, the problem of microbial contamination can be avoided.

Research on Microorganisms in Fermented Sausage

The characteristics of the starter are crucial to the production of fermented sausages, such as the optimum growth temperature of the starter, salt tolerance, and good flavors. The starter can not only hydrolyze the protein but also cannot produce harmful substances. For safety reasons, the starter must have certain antibacterial properties and can inhibit the growth of food-borne pathogens. In short, a good starter can promote product dissolution, digestion, and absorption, and increase the absorption rate of nutrients.

Nowadays, many starters with excellent performance are used in semi-dry fermented sausages and dry fermented sausages. Fermented meat products are produced with lactic acid during the fermentation process. Although it has no special flavor, the sour taste can mask other unwanted flavors and sometimes improve the salty taste of the product. In addition, a lower pH will inhibit the activity of hydrolytic enzymes such as protein and fat in fermented meat products, and can change the flavor of the final product.

Studies have shown that different types of starters have different fermentation characteristics, and the metabolites produced will also have a certain impact on product quality. With the increasing application of starters, there are three types of microbial starters commonly used: bacteria, molds, and yeasts. At present, the selected starters for fermented meat products mainly include Lactobacillus, Streptococcus, Staphylococcus, Micrococcus, mold, and yeast.

The selected lactic acid bacteria starter must meet the following conditions:

• Must be able to effectively compete with the strains in the raw material
• Must produce the right amount of lactic acid
• Must be salt-tolerant and can grow effectively at least at a concentration of 6% sodium chloride
• Should be able to improve the final flavor of the sausage product
• Must be able to grow in the temperature range of 15℃~40℃, and the optimum temperature range is 30℃~37℃
• Must be homo-fermented
• Must not produce a large amount of catalase
• Must not break down protein
• Must be nitrite tolerant and able to grow at a concentration of at least 100mg\kg
• Should be H₂O₂ enzyme positive
• Should be able to reduce nitrate
• Substances that are not conducive to the formation of biogenic amines
• Should not form slime
• Inhibition of harmful microorganisms such as pathogenic bacteria
• Should tolerate other strains in the starter or have a synergistic effect

1. Bacterial

The microbial starters used for fermented sausages are mainly lactic acid bacteria and staphylococci.

The role of starters in fermented meat products in the production process is different. The growth of lactic acid bacteria takes carbohydrates as nutrients, and finally decomposes into lactic acid, which can lower the pH of raw meat and promote maturity, which plays a decisive role in the stability of product quality. Micrococcus and Staphylococcus not only have the function of decomposing fat and protein, but also have the property of producing H2O2 enzyme, which plays a decisive role in the flavor and color of the product.

Therefore, the starter is commonly used in the ratio of lactic acid bacteria and cocci. The ability of cocci to produce acid is weak. The main purpose of adding is: on the one hand, to reduce nitrate to nitrite to promote the color of the product; on the other hand, to make the product produce a unique flavor during the process of fermentation and maturity.

Staphylococcus used in sausages in recent years, the most widespread should be Staphylococcus carnivorus, followed by Staphylococcus xylosus. They are believed to have certain beneficial effects in improving the color and flavor characteristics of the product.

2. Mildew

Mold is the most commonly used fungus in the production of dry fermented sausages, and the commonly used ones are penicillium and Scopulariopsis. It has been reported that Penicillium can be isolated from traditional fermented sausages, and 80% of them have the ability to produce toxins. A total of 17 toxins have been detected in fermented meat products.

Therefore, when selecting mold as a starter, for the safety of consumers, it is necessary to use non-toxin-producing strains. Penicillium nalidiensis and Penicillium chrysogenum are two commonly used non-toxin-producing molds. Because it is an aerobic bacteria, it often grows on the surface of sausages. In addition, these two bacteria are more competitive in growth and can secrete proteases and lipases. Therefore, inoculating these molds on the surface of sausages can effectively increase the aroma of the product and improve the quality of the product. In addition, the massive growth of surface mold can block internal and external oxygen and prevent the rancidity of the sausage.

3. Saccharomycetes

Yeast is also one of the fungal starters commonly used in dry fermented sausages. Among them, Debaryomyces hansenii is the most commonly used yeast starter. The yeast has high salt tolerance, is aerobic, and has weak acid production capacity. It generally grows and reproduces on the surface of sausages. Adding this bacteria can increase the aroma and flavor index of dried sausages.

Usually, it can also be mixed with lactic acid bacteria and micrococcus to obtain better quality products. Yeast can not only improve the flavor and color of dry fermented sausages, but also the growth metabolites will have a certain inhibitory effect on the growth and reproduction of Staphylococcus aureus. It does not have the ability to reduce nitrates, and sometimes it can cause the reduction ability of the inherent microbial flora in the meat to decrease.