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 preserving foodstuf f : canning the general principle of canning process

preserving foodstuf f : canning the general principle of canning process

 Definition of canning process :

It is the process of preserving foodstuff, vegetables or fruits, in airtight containers, whether glass or metal, and sterilizing them according to the nature of the food product and type of containers and their size,  then cooling them to the required temperature.

Steps required to prepare the product for canning :

1- receiving

Choosing suitable varieties of vegetables and fruits  for canning and should be in an ideal state of maturity, and the period between harvest and delivery of the crop to the factory should not be too long, because the  long period leads to the loss of some food components and begin the enzymatic and microbial activity, and this lead to loss in the nutritional value of the product

2- washing

We carry out the washing process to get rid of the impurities and pollutants associated with the crop. The washing process varies according to the hardness of the fruits, and sometimes substances such as hydrochloric acid are added to increase the efficiency of the washing process. before this washing process we may soak  the crop with water for period of time 

3- grading

We carry out the sorting process to get rid of foreign impurities and remove the infected, damaged or late-ripening fruits and exclude the raw fruits that are not fully ripe, then we perform the grading process according to the size of the fruits or the degree of maturity or their chemical composition (the degree of  sweetness)

4- peeling

This process affects the amount of waste that occurs and thus the final costs of the product:

Exfoliating methods are:

  •  Manual peeling using ordinary knives, and this method requires a large labor force and  therefore it is an expensive method
  • Peeling by mechanical friction, which is a cylinder lined from the inside with a coarse material called carborundum
  •  Exfoliate with hot water or steam
  •  Peeling using alkaline materials: This method is done by immersing the fruits in a hot alkaline solution. The concentration of alkali and the temperature depend on the type of fruits and their degree of ripeness. In practice, sodium hydroxide is used 1.5-2% with a  temperature of 90 ° C and a time period of 0.5-3 minutes. After this process we wash the fruits well with water to remove traces of alkali

5- cutting

It is conducted for the fruits that need to be cut into smaller pieces and is not necessarily a basic stage in the canning of all vegetables and fruits, but rather it is a special stage

6- blanching

The aim of this process is to destroy the enzymes that cause unwanted changes in color and taste in addition to other aims which are:

  • Secondary washing process
  • Eliminate a large number of microorganisms
  • In addition to getting rid of unwanted substances such as mucous materials in okra and getting rid of starches that cause turbidity in the preservation solution in legumes
  • Get rid of gases trapped in the tissues of leaf cells

The blanching process is done in two ways:

  •  The intermittent method is an easy and fast method in which the required materials are placed in baskets and then it is immersed in hot water for a certain period of time according to the type of material.
  • The continuous method. Here, the required materials are placed in a spiral cylinder that rotates at a specific speed

7- sulphuring

This process is done by adding SO2 with blanching water or immediately after branching process, to facilitate the penetration of SO2 into the tissues

8- Cooling

The cooling process is considered an important stage immediately after blanching to reduce the effects of the hot temperature on the product, where the product is immersed in basins in which renewable cold water or we use cold water  sprinklers during the passage of the product on a conveyor belt.

9- Packing

After cooling the food, we use special containers for packing food which are coated from the inside with chemically insulating materials to prevent interaction between the packed food and the metal of the container  and sometimes the filling process is done in glass containers so that it can be closed tightly and a vertical space must be left commensurate with the size of the container  and Its percentage varies according to the substance, and often the filling is done with a saline or sugary solution, where the sugary solutions are at a concentration of 65 - 70% and the brine solutions are at a concentration of 16%

10- exhausting

It is useful for getting rid of the gases trapped inside the package


11- Closing

After the elimination of the gases, a sealed operation takes place in order to prevent gas exchange between the contents of the container and the outer environment

12- sterilization

The sterilization process gets rid of all microorganisms and enzymes, as the containers are treated on the temperature between 100-120 ° C and for a period of time that varies according to the material

13- Cooling

The process is carried out quickly to stop the effect of high temperature on the foodstuff in addition to the effect of sudden cooling on the microorganisms that were not affected by the sterilization process, which leads to the rupture of their membranes.

14- Paste the data and fill the containers in appropriate boxes

15- Adequate Storage

The storage process is carried out in ventilated stores, away from direct light, at a temperature of 15-20 ° C

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