Fermented Sausage Production: Microbiology, Quality, and Defects

Methods for Measuring Water Content in Meat

The CRA (water free of meat) can be measured by:

1. Compression between two plates.
2. Centrifugation (e.g., using centrifuge tubes with meat diluted in saline, centrifuged on a glass plate at 70 °C for 30 minutes, or using centrifugal filter paper).
3. Capillarity (where free water is absorbed, and capillary air moves in a graduated U-shaped column).

Dry Fermented Sausage Composition

Dry fermented sausage is a mixture of meat, fat, salt, starter cultures, and spices.

Objectives of Fermentation

The primary objectives include:

• Developing desirable taste and odor.
• Achieving a controlled, low drop in pH.
• Removing the antagonistic effects of undesirable microorganisms.

Starter Cultures

Requirements for Starter Cultures

1. Ability to reduce nitrate to nitrite (e.g., Micrococci).
2. Ability to produce lactic acid (homofermentative strains).

Desired Characteristics of Starter Strains

Starter strains should exhibit the following characteristics:

• Nitrite and NaCl-tolerant.
• Good growth at 27-43 °C, with an optimum at 32 °C.
• Produce no off-odors.
• Be homofermentative.
• Not be proteolytic or lipolytic.
• Not be pathogenic.

Most Commonly Used Microorganisms

The most commonly used microorganisms include:

• Pediococci
• Lactobacilli
• Micrococci

Lactic Acid Bacteria (LAB)

LAB are Gram-positive, non-spore-forming, facultative anaerobic bacteria. They typically do not reduce nitrates and do not produce catalase.

They are categorized into:

• Homofermentative: Produce 90-97% lactic acid.
• Heterofermentative: Produce approximately 50% lactic acid, acetic acid, and CO₂. These often become the dominant population during ripening.

Micrococci

Micrococci are aerobic or facultative anaerobic bacteria that grow at the beginning of ripening. They are crucial for reducing nitrate to nitrite.

A balanced mixture of Lactobacillus and Micrococci is essential for the quality of fermented sausages.

Key Metabolites in Fermentation

Important metabolites include:

• Lactic acid
• Acetic acid
• Diacetyl
• Acetaldehyde
• Hydrogen peroxide
• Bacteriocins

Bacteriocins

Bacteriocins are antibacterial compounds with a very small molecular weight. They are often resistant to pasteurization and sterilization, with some exhibiting significant stability.

Bacteriocin-Producing Microorganisms

Key producers of bacteriocins include:

• Lactococci
• Lactobacillus
• Pediococcus
• Leuconostoc
• Streptococcus
• Enterococcus

Factors Influencing Meat Fermentation

Several factors significantly affect the fermentation process in meat:

• Water content
• Initial microflora
• Addition of salt
• Type of sugar (e.g., simple sugars)
• Liquid smoke application
• Process temperature
• Diameter of the sausage

Common Defects in Fermented Sausages

Defects Related to Exploitation and Dressing

These defects can manifest as:

• Taste: Fishy, bitter.
• Odor: Acetone-like, urine-like, or "sexual" (boar taint).
• Color: Dark red spots, pale coloration, or overall dark appearance.

Defects Related to Process Technology

Technological process issues can lead to:

• Taste: Bitter, excessively salty, or overly sour.
• Color: Gray spots, yellow fat, or black spots.
• Texture: Soft or mushy consistency.
• Precipitated phosphate.
• Rapid NaCl migration (rushing NaCl).
• Internal putrefaction.
• Undesirable mold growth.
• Presence of mites.