Fermentation in Food Products

Fermentation in Food Products

• Fermentation is the oldest food preservation method.
• Fermentation involves the breakdown of carbohydrates (CHO) by bacteria and yeast. This produces acids, alcohols, and some flavor compounds. The process occurs under anaerobic (no oxygen) conditions.
• Fermentation preserves food by preventing microbial degradation.
• Starter cultures are concentrated organisms used to initiate fermentation. These cultures contain specific organisms needed for the desired fermentation process.

Fermentation Process

• Glycolysis is the oxidation of glucose to create pyruvate and energy. This is a key step in many fermentations.
• Fermentation processes use various microorganisms, including Saccharomyces (yeast), Lactobacillus, and Clostridium.
• Fermentation produces different products depending on the specific microorganisms present. Products can include lactic acid, ethanol, carbon dioxide, butanol, acetone, etc.
• These products can be used in industrial processes to create various goods such as wine, beer, fuel, and pharmaceuticals.

Benefits of Fermentation

• Fermentation produces acids, like lactic acid, which preserves food.
• Fermentation adds desirable flavors. (Soy sauce is an example.)
• Fermentation changes food's chemical properties, like converting sugars to alcohol and then to acetic acid.
• Fermented foods can be more nutritious due to vitamins produced by fermentation microorganisms.
• Fermentation can break down complex molecules (like cellulose) into simpler, more digestible sugars.

Controlling Fermentation

• pH: Adding or increasing acid helps prevent undesired microorganisms from growing.
• Salt: Salt tolerance varies. Lactic acid bacteria often tolerate higher salt concentrations than other microorganisms.
• Temperature: Different microorganisms thrive at different temperatures. The optimal temperature impacts the outcome of the fermentation process. Brine (salt water) is used as a preservation method in many processes to prevent the growth of microorganisms that do not grow as well in high salt concentrations..

Uses of Fermentation

• Various foods are produced using fermentation, including vegetables (like sauerkraut and pickles), fruits, dairy products (like yogurt), and meats (like sausages).

Vegetable Fermentation

• Starch and CHO in vegetables are converted into lactic acid by lactic acid bacteria present on the surface of the vegetables.
• Some lactobacilli are homo-fermentative leading to the production of 2 moles of lactic acid, while others are hetero-fermentative producing a combination of lactic acid, ethanol, and carbon dioxide.
• Sauerkraut production involves washing and shredding cabbage, then adding salt and brine. The amount of sugar in the brine affects the final acidity. Optimal temperatures are typically around 18-22°C.
• Types of lactic bacteria involved vary but can include Leuconostoc mesenteroides, Lactobacillus brevis and Pediococcus cerevisiae, and Lactobacillus plantarum. The fermentation process develops acidity and flavor.

Brine-Salted Vegetables

• These processes resemble sauerkraut fermentation using brine (salt solution) to preserve vegetables.
• Salt concentrations generally range from 15-20%, but the lowest concentration must remain at 12% to allow the intended microorganisms to grow well.
• The fermentation process for these typically takes about 12 days at 30°C, with the salt being the primary preservative in this case (not lactic acid.)

Cucumber Pickles

• Fresh cucumbers are used and are packed with acetic acid (0.6%).
• Spices add flavor.
• The salt concentration ranges from 11.25% to 15.90%.
• Microorganisms are lactic bacteria (similar to sauerkraut).
• The final acidity level is typically between 0.6% and 1.2% (as lactic acid) and takes about 7-14 days to develop.

Olives

• Olives are brined similarly to cucumbers.
• Olives are initially soaked in a 1.25%-2.0% lye solution to remove their bitter taste.
• Lactic bacteria are used.
• The final acidity is 0.18%-1.27% and needs to reach a minimum of 0.6% for optimal flavor.

Advantages of Vegetable Fermentation

• Extended shelf life (preservation).
• Easier digestion.
• More nutritious because the process doesn’t involve cooking.
• Safer to eat.
• Adds variety to food options.

Yogurt

• Milk is standardized (10.5-11.5% solids), heated (90°C), then cooled (40-45°C).
• Mixed culture of Streptococcus thermophilus and Lactobacillus bulgaricus is introduced.
• The inoculated milk is incubated at 42°C for 3-6 hours.
• The milk is cooled to 5-10°C to stop fermentation.
• Final acidity is 0.9-1.2% (as lactic acid), with a pH of about 4.4.

Swiss Cheese

• Starter culture combines regular lactic culture with propionic acid bacteria (Propionibacterium sp.) and Streptococcus thermophilus.

Blue-Veined Cheese

• Starter culture is regular lactic culture plus dried spores of the mold, Penicillium roqueforti.

Italian Cheese

• Includes mozzarella, Romano, Provolone, and Parmesan (Grana).
• Starter cultures typically use Streptococcus thermophilus and Lactobacillus bulgaricus.

Latin American White Cheese

• Queso Blanco is the most common unripened, soft cheese.
• Natural microflora or organic acids (vinegar, lemon juice, or glacial acetic acid) can be used for curd formation along with rennet in some cases.

Vinegar

• Vinegar is made through alcoholic fermentation followed by oxidation of the alcohol to acetic acid.
• Yeast ferments food into ethanol.
• Air and Acetobacter bacteria are added to the ethanol to produce acetic acid.

Bread Making

• Fermentation in bread involves yeast (Saccharomyces cerevisiae).
• Yeast produces carbon dioxide, which makes the dough rise.
• Bacteria can also play a role, primarily in flavor development. Leuconostoc mesenteroids are one example of such a type of bacteria present in bread.
• Chemical changes in the dough help provide volume, structure, and texture, as well as impacting flavor.
• Dough conditioners like ammonium sulfate and sugars are added to stimulate yeast.
• Gas production is affected by yeast activity, sugar, amylase, temperature, and salt levels.

Fermented Meat

• Fermented meat generally has a pH below 5.6 and high D-lactic acid.
• Meat products (e.g., sausages) can be fermented, with a range of types using various processes and levels of ripening.
• Fermented meats utilize a variety of LAB types.
• Various methods are used, with different levels of ripening and moisture that impact the final product and flavors.
• Fermentation processes can also affect and reduce food poisoning risks through lactic acid production and low moisture levels, particularly with some types of bacteria.

Fermentation of a Comminuted Meat Matrix

• Particle size, additives (salt, nitrate, ascorbic acid, glucono-d-lactone), temperature, humidity, sausage diameter, casings, and heating/antifungal dipping play a role during production.

Fermentation of Whole Meat Products (e.g., ham)

• Curing by salting is a primary method, possibly along with nitrite and/or nitrate.
• Salt diffusion is assisted/increased by low temperatures.
• The process helps prevent Clostridium botulinum contamination.
• After salt and flavor development, the temperature is increased to aid ripening.
• Ripening time is often 6-18 months.

Composition Changes During Fermentation

• Microorganisms (LAB) cause acidification.
• Nitrates can be reduced to nitrites and nitrosomyoglobin.
• Proteins and lipids are degraded, and dehydration occurs.

Acidification, Dehydration, Microbial Antagonism

• Protein isoelectric points (pH 5.3-5.4) are affected.
• Salt strength is increased, with lactic acid and sodium chloride contributing to the taste profiles.
• Acidification and drying inhibit pathogens.
• Lactic and acetic acids are key fermentation products, influencing moisture and flavor development.
• Various properties are influenced by the ripening process and the level of salt and moisture in the finished product.

Proteolytic and Lipolytic Degradation During Fermentation

• Accumulation of peptides and amino acids (about 1% of dry matter).
• These peptides and amino acids can affect flavor.
• Excess proteolysis can lead to bitter off-flavors.
• Amino acids and peptides are used by microorganisms creating some flavor characteristics
• Fat content can range from 40-60% dry matter.
• Fatty acids are released from triglycerides and phospholipids.
• Free fatty acids constitute about 5% in most fermented products, including meat products.
• Polyunsaturated fatty acids tend to exceed saturated fatty acids.

Generation of Flavor Volatiles

• Lipolysis and hydrolysis of phospholipids followed by fatty acid oxidation are common pathways.
• Microorganisms produce organic acids and modify the products for flavor development (by producing certain alcohols, aldehydes, and other substances).
• Flavor is also affected by additions like spices, smoking, or ripening with yeasts or molds.

Mechanisms for Generation Flavor Compounds

• Carbohydrates, proteins, fats, peptides, and amino acids contribute to flavor in different ways.
• Taste compounds are affected by bacteria and other microorganisms.
• Flavor compounds can develop through microbial actions, or as a result of additions such as smoking or spices.

Product Diversity and Sensory Properties

• Lactic acid production, breakdown of lipids, and degradation of peptides/amino acids influence the flavor/taste profile of fermented meats.
• Oxygen consumption, nitrate reduction, and protein degradation by microorganisms, also effect.