Chemical preservatives And Biological Preservations

Chemical preservatives and Biological preservations (Preservation by fermentation):

Chemical preservatives:

1. Organic acid and their salts.
2. Sulphur dioxide (SO₂)
3. Nitrate (NO₃) and Nitrite (NO₂₎
4. Smoking and wood smoke

#Organic acids and their salts :

Various organic acids and their salts are used as chemical preservatives. Some of them are:

1. Propionic acids and their salts
2. Benzoic acids or benzoates.
3. Sorbic acid and sorbates.
4. Acetic acid and acetate.
5. Boric acid.

• Propionic acids and their salts:

Propionic acid is short chain of fatty acid, which are digestible fatty acid (harmless but may produce pungent smell.) Sodium and calcium propionate are ideal preservatives for baked goods.They are effective against yeast and mold than bacteria.

Application :

They are used in butter, jam, jellies, apple slices, malt extract, etc.

• Benzoic acid or benzoates:

These naturally occur in several varieties of vaccinium species (cranberry). These are effective against yeast and mold than bacteria. Its salt forms are more suitable preservatives as they are more soluble i.e. sodium benzoate, potassium benzoate, calcium benzoate, etc. Efficacy in Ph dependent is used in food having Ph less than 4.

Application:

They are used as preservatives for fruits like fruit juices, jam, jellies, carbonated beverages, pickles, tomato ketchup, saur kraut (cabbage's prickles), preservations of colour juices (grapes, strawberry)

• Sorbic acid and Sorbates:

These chemical preservatives are harmless, digestible like fatty acid. These chemicals preservatives are effective against yeast and mold. Due to low dissociation constant, it is effective up to Ph- 6.

Applications:

Dairy product (cheese), meat products (sausages, beef, poultry), dried fish product, fruits, and vegetables, confectionary, baked products, etc.

• Acetic acid and acetate:

Acetic acid and its derivatives like chloroacetic acid, para acetic acid, dihydro acetic acid and sodium diacetate (salt) have been referred as the chemical preservative of food. These are effective against yeast and bacteria than mold.

Applications:

These are used for the preservations of pickles, sausages, cheese, malt syrup and incorporated in wrapping matter.

• Boric acid:

Boric acids or sodium tetraborate (Na₂B₄O₇)are used in food. These are effective against yeast and mold and then bacteria. It is non-toxic to food and used in high concentration about 0.5 to 1%...are used in food. These are effective against yeast and mold and then bacteria. It is non-toxic to food and used in high concentration about 0.5 to 1%.

Applications:

It is used in the preservation of neutral foods like butter, etc.

#Sulphurdioxide:

It has antimicrobial, antioxidant properties and inhibits enzymatic and non-enzymatic browning properties of food. These are effective against bacteria and yeast than mold. Most countries banned the use of sulphur dioxide in fresh fruits and vegetables that are eaten raw. Sulfite is counted among the top 9 food allergens. Since hexavalent sulphur is more stable than potassium metaphosphate (K₂S₂O₅) is commonly used in food processing.

K₂S₂O_{5 ⇒} K₂SO₃+ SO₂

(heated) potassium sulphide

Application:

1. Used in the preservation of the raw and semi-finished product.
2. Used for preservation of juice concentrate, pulp squash (up to 350 up to 200 ppm.)
3. Used in beer (70-80 ppm), wine (100-250 ppm) as preservatives.

# Nitrate (NO₃^-)and Nitrite (NO₂^-):

The nitrate and nitrite are used as the preservative, color stabilizer and flavouring agent in meat and fish product. Nitric oxide thus formed inhibit the reaction that occurs within many enzymes including porphyrin compounds (Fe- containing compound).

NO₃ ^⇒ NO_{2 ^⇒} HNO₂ ⇔ NO

(Reduction) (H⁺) (nitrous acid) (nitric acid)

It is used as the preservative at low pH, Lactic Acid Bacteria (LAB) are used to reduce pH. When nitrite combine with amino acid produces nitrosamine, a potent (powerful chemical mutagens or carcinogenic agents) causing mutation.

(heat)

Myoglobin + NO → Nirosohemochrome

(purple colour) (Nitric oxide) (stable pink color)

Applications:

Used for the preservation of meat and meat products.

# Sugar and salt:

These compound decreases water activity (a_w) and hence have and hence have a detrimental effect on the microorganisms. Sugar such as glucose, sucrose increases unavailability of water for microorganisms and causes osmotic effect, so that food remain preserved. Food like sweet and condensed milk, jellies, syrup (fruits), candies, honey, etc. are preserved due to the high concentration of sugar. Salt like sodium chloride used in brine solution have the following effect:

• Dehydrates food by drawing out in tying of moisture.
• Ionizer to form chloride ion i.e. harmful to microorganisms as the interface with an action of some proteolytic enzymes.

# Smoking and wood smoke:

Smoking and smoke are used as food preservatives and it also adds flavour to food. It helps in tenderization (hardening of meat) and color improvement. Wood smoke contains many anti-microbial constituents such as formaldehyde such as HCOOH, phenol, cresol, aliphatic acid, ketones, acetaldehyde, etc.

#Applications:

Mainly used in preservation of meat and meat products (for example: in the process of making dry meat, etc.)

• Advantages of chemical preservatives:

The advantages of using chemical preservatives are as follow:

1. They act as the antioxidant in food .
2. They delay spoilage and enhance color, flavor, maintain its consistency and texture of food.
3. One of chemical preservative i.e. butylated hydroxytoluene (BHT) are phenolic chemical compounds that are often added to packaged foods to preserve their shelf life.

• Disadvantages of using chemical preservatives: The following are disadvantages of using excess chemical preservatives in food which are as follow:

1. The excess use of sulphur dioxide in food may cause health hazard like swelling and irritation of body leading to allergy. As it is listed in top 10 food allergens.
2. The excess use of nitrite may lead to cancer due to its carcinogenic agents and may cause mutation.
3. Various acids like organic acids, may bring food in acidic nature and may give sour flavor to food by deteriorating its original flavour if they are used in the high amount of food.
4. Excessive use of these chemical preservatives may cause health hazards like stomach pain, brain disorder, paralysis, etc.

Biological preservation / Preservation by fermentation:

This method of preservation of food is based on the production of alcohol, organic acid (lactic acid, propionic acid, butyric acid are produced during fermentation and carbon dioxide produced as the byproduct during fermentation also acts as preservatives.It is one of the ancient methods of food preservation which in been used from many years ago. It does not cause any health hazard as like other artificial food preservatives. But is is the time-consuming method of food preservations.Some Nepali fermented food products are:

Advantages of Biological Preservation:

1. The fermented food products help to maintain the correct balance of normal flora (bacteria) in gut.
2. This method of preservation include the natural ingredients for the growth of beneficial microorganisms , or probiotic as commonly known.
3. The food obtained through this process contain increased levels of folic acid, which is very important for pregnant women in preventing birth defects, along with various other vitamins including the vitamins B.
4. They are also rich in enzymes, which are needed for digestion and absorption of food and also increase flavor in food.
5. The fermented food containing lactic acid bacteria improves intestinal tract health, improves the bioavailability of nutrients, reduces symptoms of lactose intolerance and decreases the prevalence of allergy in susceptible people.

Reference:

1. Jay, MJ. Modern Food Microbiology. 3rd. Delhi: CBS Publications and Distributors, 1987.
2. Frazier, Wc and Westhoff DC. Food Microbiology. 3rd. New-Delhi: Tata MCGraw-Hill Publishing Company Limited, 1986.