The Chemistry of Food Preservation

Senior Presentation CHEM401

Done by: Farah Kanj

Supervised by: Dr. Rami Oweini

Fall Semester: 2016-2017

Outline What is Food Preservation ? Methods of Food Preservation a) Description of Each Method b) Advantages and Limitations Conditions for Food Spoilage World Trends Affecting Food Science Conclusion

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What is Food Preservation ? Food preservation is the process of

treating and handling food in such a way as to stop or greatly slow down spoilage to prevent foodborne illness and extend its shelf-life.

How a food is processed can affect its appearance, odor, flavor, and texture.

Institute of Food Technologist IFT 2

Different Methods of Food Preservation

1. Pickling2. Canning3. Freezing4. Biopreservation5. Nitrates and Nitrites

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Food Preservation Method #1 Pickling Pickling is a method of preserving

food in an edible anti-microbial liquid. Pickling can be broadly classified into

two categories

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Pickling

Chemical Fermentation

1) Chemical Pickling: In chemical pickling, the food is placed in

an edible liquid that inhibits or kills bacteria and other micro-organisms.

Typical pickling agents include brine (high in salt), vinegar, alcohol, and vegetable oil.

Common chemically pickled foods include cucumbers, peppers, and corned beef.

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2) Fermentation Pickling: In this process, the food contains sufficient moisture, a

pickling brine may be produced simply by adding dry salt.

Natural fermentation at room temperature by lactic acid

bacteria (LAB) produces the required acidity. Both Pickling processes take place at acidic pH=4.6 or lower

which is sufficient to kill most bacteria.

U.S. Food and Drug Administration Center for Food Safety and Applied Nutrition 6

Food Preservation Method #2 Canning The canning technique was developed by the

French Chemist Nicolas Appert in 1795. It is a popular way of preserving fruits,

vegetables, and meats. It involves cooking food, sealing it in sterile cans

or jars, and boiling the containers to kill or weaken any remaining bacteria as a form of sterilization. Canning

Water – Bath Pressure

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1.Water – Bath Canning: This method usesa large kettle of boiling water.

Filled jars are submerged in the waterand heated to an internal temperature of 212 °C for a specific period of time.

It is used for processing high-acid foods,such as fruit, and tomatoes.

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2. Pressure canning: Pressure canning uses a large kettlethat produces steam ina locked compartment.

The filled jars in the kettle reachan internal temperature of 240°Cunder a specific pressure at 10-15pounds per square inch of pressure measured by gauge.

It is used for preserving vegetablesand other low-acid foods,such as meat, poultry, and fish.

Internet Journal of Food Safety, Vol. 4, 2004, p. 21-32 9

Food Preservation Method #3 Freezing Freezing has been successfully employed for

the long-term preservation of many foods, providing a significantly extended shelf life.

Pathogen growth is stopped below –4°C

Because of differences in cellular composition, foods actually begin to freeze at different temperatures ranging from about –0.6°C for some kinds of fish to –7°C for some kinds of fruits.

Fellers ,C. Public Health Aspects of Food Preservation Fennema, O., Principles of Food Science 10

Food Preservation method #4 Biopreservation Biopreservation is the use of natural or controlled

macrobiotic or antimicrobials as a way of preserving food and extending its shelf life.

One of the most common forms of food biopreservation is fermentation, a process based on the growth of microorganisms in foods, whether natural or added. These organisms mainly comprise lactic acid bacteria (LAB) which add unique flavor and texture to food.

Examples of biopreserved food are cheese, yogurt, and sausage.

Ananou S, Maqueda M, Martínez-Bueno M and Valdivia E Biopreservation, an ecological approach to improve the safety and shelf-life of foods 2007

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Food Preservation Method # 5 Nitrates and Nitrites Nitrates (NO-

3) and nitrites (NO-2) have

been used as chemical preservatives in cured meats for centuries especially in hams and bacon.

They are added in the form of sodium nitrate and sodium nitrite in food.

Because of the relatively high toxicity of nitrite, the maximum allowed nitrite concentration in meat products is 200 ppm.

Gunnar, K. Nitrates and Nitrites in Food12

Method Advantages

Limitations

Pickling • Improve flavor• More

Nutritious• Increased level

of Vitamin B6

• Changes taste of the food

• Not safe against some pathogens

Canning Extend the shelf life of food from 1-2 years

Contamination by clostridium botulinum which lead to severe illness

Freezing Frozen Food contain no preservatives

Pathogens are deactivated but not killed

Biopreservation

Biopreserved food improve intestinal tract health

Decrease some vitamins in the human body

Nitrates and Nitrites

Characteristic Flavor

Nitrosamine include liver cancers in animals

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Conditions For Food Spoilage Food spoilage is a naturally occurring

process. Factors that affect food spoilage include:a. Microorganism: cause food borne illness

and are called pathogenic microorganisms.b. Light Exposure: Could result in change in

color and vitamin loss in food.c. Temperature: The ideal temperature for

bacterial growth is 30°C - 37°C .d. Insects and rodents: These creatures

require food to survive and can damage food, making it more exposed to further deterioration.

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World Trends Affecting Food Science1. Handling new technologies -

nanotechnology in food and feedAs a twenty-first century technology, nanotechnology has enormous impact in a broad variety of areas. Nanotechnology in the food chain can be used for instance during the cultivation, production, processing or preserving of food .

2. Fighting biological risksThe spread of pathogenic food-borne microorganisms, such as Salmonella, within the food chain poses a major challenge to food safety. Geslain, C. Trends In Food Science & Technology 15

Conclusion Over the years many food preservation

methods have been improved to increase the shelf-life of foods while minimizing changes to the quality and nutritional content.

In general, freezing is thought to be one of the easiest and most cost effective ways to preserve your food cause it contains no preservative. 1

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