Fermentation (Food Micro-Biology Lecture)

 Fermentation

Fermentation is an anaerobic process in which microorganisms like yeast and bacteria break down food components (e.g. sugars such as glucose) into other products (e.g. organic acids, gases or alcohol).

This gives fermented foods their unique and desirable taste, aroma, texture and appearance.

Starter Cultures

Traditionally the fermenting organisms came from the natural microflora or a portion of the previous fermentation. In many cases the natural microflora is either inefficient, uncontrollable, and unpredictable, or is destroyed during preparation of the sample prior to fermentation (e.g. pasteurization).

A starter culture can provide particular characteristics in a more controlled and predictable fermentation.

Other functions of starter cultures may include: flavor, aroma, and alcohol production, proteolytic and lipolytic activities, inhibition of undesirable organisms.

A good starter culture will convert most of the sugars to lactic acid. Increase the lactic acid concentration to 0.8 to 1.2 % which drops the pH to between 4.3 to 4.5.

Fermented Foods

Fermented Foods are foods which are processed through the activities of microorganisms.

For example: bread, beer, cheese, coffee etc.

• Foods that have been subjected to the action of microorganisms or enzymes, in order to bring about a desirable change.

• Numerous food products owe their production and characteristics to the fermentative activities of microorganisms.

• Fermented foods originated many thousands of years ago when presumably micro-organism contaminated local foods.

• Micro-organisms cause changes in the foods which: Help to preserve the food.

Extend shelf-life considerably over that of the raw materials from which they are made

Improve aroma and flavor characteristics.

Increase its vitamin content or its digestibility compared to the raw materials.

• The term “biological ennoblement” has been used to describe the nutritional benefits of fermented foods.

• Fermented foods comprise about one-third of the world wide consumption of food and 20- 40 % (by weight) of individual diets.

Importance of Fermentation in Food Production

The process of fermentation destroys many of the harmful microorganisms and chemicals in foods and adds beneficial bacteria.

These bacteria produce new enzymes to assist in digestion.

• The fermentation process may improve the nutritional quality of raw material. examples:

• The presence of yeasts in fermented food will increase the vitamin B content.

• Anti nutritional factors such as phytase and lectins may be removed by fermentation process.

• Fermentation may produce an increase in the availability of minerals.

• Fermentation often preserves a raw material, improving safety with regard to food borne pathogens and increasing shelf life.

Role of bacteria in the Production of Fermented Food

The bacteria are divided into three main phyla:

1.Firmicutes

Gram positive bacteria-lactic acid bacteria.

Bacillus and brevibacterium-less common.

2. Proteobacteria

Gram negative bacteria-vinegar fermentation and wine spoilage.

3. Actinobacteria

Staphylococcus-used in meats for flavoring.

Bifidobacterium-added to enhance nutritional worth.

Micrococcus.

Role of molds & yeasts in the Production of Fermented Foods

Molds:

Most commonly used mold in fermentation are: Penicillium and Aspergillus.

Molds are involved in production of moldy ripened cheese and sausages.

Yeast:

Most important are saccharomyces.

Saccharomyces are needed in the production of fermented products like wine, beer, bread products.

Benefits of Fermented foods

The benefits of Fermented foods are:

• Preserving Foods at Low cost.
• Improvement of organoleptic properties.
• Removing unwanted (harmful) properties in raw material.
• Improvement of nutritive content of food.
• Increased economic value.

Advances in Food Fermentation

• Engineering of microorganisms for improved fermentation

Microorganisms develop through genetic techniques that can better ferment                substrates to produce the desired products.

Recombinant DNA technology can be used to genetically improve bacterial strains. Specific genes can be partially or totally eliminated from a strain or replaced. Likewise,

new properties can be introduced into a strain by gene transfer.

Metabolic pathway engineering of various enzymes.

Improvement of the rheological properties of fermentation broths.

Development of more efficient process-driven technologies Examples: solid-state fermentation, ultrasonication, syngas fermentation, and dark fermentation.

New bioreactor designs Examples: High-mass transfer chemical reactors for methanotroph fermentation and versatile tray-type solid-state fermentation bioreactors.

Nutritional value of fermented foods

1. The quantity and quality of food proteins is expressed by biological value, and often the content of water soluble vitamins is increased.

2.The anti nutritional factors show a decline during fermentation.

3.The protein efficiency ratio (PER) of food increases on fermentation.

4.During fermentation certain microorganisms produce vitamins at a higher rate than others. The levels of vitamin B12,riboflavin and folacin are increased by lactic acid fermentation of maize flour.

5.When fermentation is carried out in metal containers some minerals are solubilized by the fermented product, which may cause an increase in mineral content. Phytate content in bread is lowered when the amount of yeast or the fermentation time is raised.

Health Benefits of fermented Food

The beneficial effect of fermented food which contains probiotic organism consumption includes:

Improving intestinal tract health.

Enhancing the immune system.

Synthesizing and enhancing the bioavailability of nutrients.

Reducing symptoms of lactose intolerance.

Decreasing the prevalence of allergy in susceptible individuals.

Reducing risk of certain cancers.

Some fermented foods are said to have definite health benefits.

Reports suggested that fermented milk products such as yogurt can reduce serum cholesterol levels and help avoid cancers, particularly those associated with the colon.

Bio Yogurts are said to have restorative effects on the gut microflora, assisting recovery of a normal balanced flora after oral antibiotic therapy.

They have an ability to improve digestion. Some fermented foods are more easily digested than the original raw material. People who can not digest lactose properly can often consume some types of fermented dairy products without harmful effects.

Health benefit of Some Fermented Foods

Kimchi: vitamin A, thiamine (B1), riboflavin (B2), calcium, and iron anti cancer.

Sauerkraut: Vitamin C, K & B, Iron, Potassium, copper, manganese, Good for stomach, anti cancer.

Coffee: Anti cancer, help in treatment of Diabetes type II

Chocolate: Improve circulatory system, rich source of flavonoids, decrease cholesterol level.

Cheese: Prevent tooth decay, improve sleep & relieve tension.

Yogurt: protein, calcium, vitamin D, riboflavin, vitamin B6, B12, Prevent osteoporosis, reduce the risk of High blood pressure, decrease gastrointestinal infections, improve immune system, digestion, against allergies, build bone density.

Pickles: Cancer reduction, antibiotic production, improve mental health.

Vinegar: Detoxification, help in weight loss, skin problems, lower blood pressure and cholesterol, ease arthritis.

Safety of Fermented Foods

The improved food safety arising from fermentation is largely due to lactic acid bacteria, a group of organisms that predominate in most fermented foods.

They inhibit the growth of spoilage flora of the food material and of any bacterial pathogens.

Fermented foods are safer than their unfermented counterpart owing to the following:

• Inhibition of the growth of most pathogenic bacteria

• Removal of natural toxic components.

• Inhibition of the formation of bacterial toxins

Food and water-borne viruses, a frequent cause of gastroenteritis, may survive high levels of acidity.

Most toxins produced by some algae, bacteria and molds are also unaffected by fermentation. Therefore, it is crucial not to rely only on fermentation to eliminate or reduce hazards to safe levels.

For this reason, fermentation is frequently combined with other processes such as soaking, washing, cooking and pasteurization to ensure adequate safety.

In addition, it is important to observe good food safety practices to ensure fermented food safety. These includes:

• Ensuring that the starting materials used do not come into contact with manure or compost.

• Using good fresh food as starting materials.

• Using only starting products from healthy animals.

• Observing appropriate levels of hygiene and sanitation to avoid contamination during handling.

• Observing proper fermentation procedures.