Food preservation technique: Smoking

Smoking is the process of flavoring, cooking, or preserving food by exposing it to smoke from burning or smoldering material, most often wood. It is an ancient method of preserving food using wood smoke. It is believed to be almost as old as the use of fire itself.

Smoking is still widely used in fish and meat and some other foods. The smoking process allows cured meats, poultry, game and seafood to be subjected to smoke in a controlled environment. The smoke is produced by smoldering hardwood chips, vines, herbs, fruit skins, or spices.

While smoking process, some reactions occur between food and smoke. After smoking process, a second covering shell occurs in food or meat products. Smoking operation which adds some volatile compounds to the product inhibits bacterial growth and gives a specific taste to the product. This smoke influences the flavor, aroma, texture, appearance and shelf life of foods. The process can be performed at temperatures that range generally from 65°F to 250°F.

Food smoking is part of a revival of old crafts and traditional foods, and an increase in food awareness – people want to know what's in the food they are eating. The trend is towards high-quality ‘slow’ food, with local, natural ingredients free from chemical additives. Smoking is a way for farmers, smallholders, hunters and fishermen to make use of large amounts of meat or fish at certain times of the year.

Meats and fish are the most common smoked foods, though cheeses, vegetables, and ingredients used to make beverages such as beer, smoked beer, and lapsang souchong tea are also smoked.
Food preservation technique: Smoking

Food preservation: Fermentation

Fermentation is one of the oldest ways of preservation food products with desirable properties such as extended shelf-life and good organoleptic properties. It is an essential metabolic phenomenon that basically takes place in absence of oxygen (O2).

Fermented foods are staples of the human diet and usually have an improved microbial stability and safety. In addition, some can be stored even at ambient temperatures. Furthermore, there are several examples of fermentation processes which lead to an increase in nutritional value or digestibility.

Fermentation happens commonly in yeast and bacteria and also in oxygen-starved muscle cells, as in the case of lactic acid fermentation. Microorganisms are integral part of the processing system during the production of fermented foods. In terms of microbiologists, fermentation is a primary means of producing ATP by the degradation of organic nutrients anaerobically, in presence of suitable microorganisms.

Science of fermentation is called zymology. Research shows that fermentation processes have been developed in order to preserve foods for times of scarcity by preserving the food by organic acid and alcohols at the same time it imparts desirable flavor, texture to foods, reduce toxicity and decrease cooking time.

Fermentation is employed in the production of foods and its major roles including:
(1) Preservation of food through formation of inhibitory metabolites such as organic acid;
(2) improving food safety through inhibition of pathogens or removal of toxic compounds;
(3) improving the nutritional value and also makes the food palatable by enhancing its aroma and flavor.

Food preservation: Fermentation 

Food preservation: Acidification

Acidification is a method of food preservation. All microorganisms have a pH at which they grow best, and range of pH above or below which they will not grow.

U.S Code of Federal Regulations defines that acid and acidified food as foods having a pH of 4.6 or lower.

Acids are used to decrease the pH of foods. By doing so, they can improve its microbial stability and impact its taste by imparting their own flavor and modifying the taste perception of other ingredients. By improving the food's microbial stability, the acids can be used as preservatives in acidification processes.

Generally, it is not possible to preserve all foods by adding acid to the point where no microorganisms will grow. Most foods would be too acid to be palatable. Enough acid may be used to inhibit the growth of microorganisms provided that such treatment is combined with some other method of preservation.

Methods of drying and/or addition of salt or sugar to foodstuffs are often combined with a reduce pH – increase acidification.
Food preservation: Acidification

Smoking of fish

Smoking is often used to preserves and flavor meat, fish, and cheese, etc.  It is likely the practice of smoking meat and fish outdates the art of cooking in containers, as open-fire contact (roasting) with food must have been the earliest form of cooking even before earthen ware pots were made.

The importance of wood as fuel, with wood smoke as an integral part of that and perhaps later its utilization in food processing is tied to the same aspect of civilization.

At a dig in Bishkupin, Poland, scientists discovered a fish scales and bones of bass, bream, catfish, pike and roach showed the site to be an eight or tenth century fish smoking plant, which prepared large catches from Biskupin Lake for a large population.

Smoking foods is one of the most ancient food preservation process and in some communities one of the most important. Native Americans of the East Coats and Caribbean preserved fish and haunches of venison by stretching them over cane or wooden racks above a slow, fragrant fire of grass, herbs and mesquite or hardwood.

When Spanish expeditioner Hernando De Soto reached Tampa Bay, Florida, he studied the Timucua method of building strong wood scaffolds over the fore for the roasting of deer, dog, alligators, fish and snake.

Fish could easily be smoked. Before the invention of the chimney, houses normally had thick smoke above head level, slowly finding its way to the smoke hole. Hanging gutted fish on the rafters lightly preserved it by drying and partially cooking it.

More modern methods of smoking fish us formulation of liquid smoke to provide flavor and a range of methods of drying to reduce water activity on the surface. Most drying methods use heat to change the relative humidity of the air passing over the fish.
Smoking of fish

Radiation preservation of foods in United States

In depth food radiation studies in the United States began in the early 1950s, when both radiation sources and processing requirement were developed to practical point.

Most of the studies have been government sponsored at least partly because the 1958 Food Additive Amendment to the Food, Drug and Cosmetic Act required advance proposal from the Food and Drug Administration (FDA) before any particular irradiated food could be publicly sold.

Earlier work (1947-1952) was carried out by at least three private companies in the United States.

A similar circumstance prevailed in other countries, resulting, worldwide, in predominantly government sponsored food irradiation research programs.

Because of the lack of research facilities in many third world countries, specialized agencies of the United States also became actively involved in international food irradiation research programs.
Radiation preservation of foods in United States

Food processing: quick freezing

The two basic ways to achieve the freezing of foods are quick and slow freezing. The technical features of the quick freezing process are ultra rapid freezing at very low temperatures (-30 to -40 ° C) designed to bring the inside the product to a temperature of -18°C as quickly as possible. Rapidly frozen foods have a much longer storage life than foods stored in cold stores.

The products that are generally preserved by quick freezing are meat, fish, some vegetables such as peas, spinach, cauliflower, carrots, beans etc.

When the quick freezing process is used, these liquids solidify to form extremely fine crystals of ice, and the cellular structure is left intact, whereas, in the ordinary freezing process, where low temperatures are reaching more slowly, the texture of the product is altered.

In quick freezing, large quantity of food can be frozen in a short period of time.

Quick freezing is a method of increasing the shelf-life of perishable foods by subjecting them to conditions of temperature low enough to inhibit the oxidative, enzymatic and microbial changes, which are responsible for the changes in flavor and color of foods.

Quick freezing is ideal for producing good quality frozen foods. The food freezes immediately and keeps its shape and appearance.

Quick freezing is obtained by one of the following methods:
*Freezing Tunnel or Blast Freezer
*By Direct Contact with Metal Plate Surfaces maintained at Low Temperatures
*By immersion in (or by Spraying)  a Low Temperature Liquid
Food processing: quick freezing 

Water in Food Preservation and Shelf Life

Water in Food Preservation and Shelf Life
Drying and freezing are common food preservation techniques. Foods are dehydrated or frozen the available water and extend shelf life.

The control of water level in foods is an important aspect of food quality as water content affects the shelf life of food.

For example, foods may be more desirable either crispy or dry. Freezing and drying are common food preservation processes that are used to extend the shelf life of foods because they render water unavailable or pathogenic or spoilage bacteria.

If the water in foods is frozen quickly, there is less damage to the food at the cellular level.

Preservatives may be added to a formulation to prevent mold or yeast growth. Humectants which have an affinity for water are added to retain moisture in foods.
Water in Food Preservation and Shelf Life