Process of canning effects on vegetables

From the textural standpoint, vegetables may be divided into those that are eaten raw and valued primarily for their crispness, those that are eaten cooked and valued for their softness and those that can be consumed in either form such as cauliflower and carrots.

Vegetables like peas, beans, greens are sometimes canned. The retention of original color is of great importance effecting the marketability and consumer response.

In the process of canning, vegetables are heated to destroy spoilage disease causing microorganisms.

Such heat treatments also produce a number of of undesirable chemical and textural changes in the vegetables. The textural changes are due to partial destruction of the cell wall and cell membrane.

Blanching, plus the strong heat treatments applied to nonacid vegetables, appears to be responsible for the large vitamin losses in canning.

Heat treatments also cause chemical alteration of the green pigment chlorophyll, thus resulting in a processed vegetable with less green color.

During canning chlorophyll gets converted to pheophytin due to the high temperature used. Sometimes to retain the color and to neutralize the acid, alkali is added.
Process of canning effects on vegetables

Irradiation sterilization

Irradiation or ionizing radiation is a type of ‘cold’ sterilization, where the piece being sterilized is not exposed to heat. However, due to the poor heat transfer properties of many types of products, small increases in temperature above ambient can occur in the irradiated product.

Similar to sterilization by heat that requires high temperatures for specified times, sterilization of foods by irradiation requires high enough radiation doses to inactivate bacterial spores.

Radiation sterilization can be accomplished using one of three forms of radiation: gamma sterilization using radioisotopes, electron beam using electron accelerators, or beta radiation using an electron accelerator.

The irradiation sterilization process extends beyond treatment of health care products to commodities and irradiation of food to destroy pathogens such as salmonella and E. coli to make our food safer to eat.

Irradiation sterilization of foods, including meats and poultry, was extensively studied in the 1950s and 1960s, mostly by the US government. Irradiation sterilization effectively kills microorganisms because of its ability to break the chemical bonds of organic compounds, producing highly reactively species known as free radicals.
Irradiation sterilization

Food sterilisation

Sterilisation is a technique to prolong the shelf life of foods.  It is the complete destruction or elimination of all viable organisms in/on a food product being sterilised.

For some canned products they are heated for up to one hour. All micro-organisms are killed during this process. After sterilisation the product is free of germs and, if stored correctly, have a shelf life of several years.

Classical sterilisation treatments are subdivided into two categories: sterilisation by heating (thermal processing) and sterilisation without heating (non-thermal processing).

Thermal processing is widely practiced in spite of some problem such as that the process might reduce nutrition or deterioration the quality of foods.

Non-thermal processes include high pressure processing, pulsed electric fields, ultraviolet radiation, food radiation, chemical treatments, and use of magnetic fields.

Thermal processing is further divided into two categories as in-container sterilisation and aseptic sterilisation.
Food sterilisation

Loss of Quality

Loss of Quality
Just as important as selecting for food quality is the prevention of the loss of quality. The most pervasive problems are probably control of staling and prevention of moisture migration.

Staling as a process is well understood and much progress has been made in understanding how to delay the staling process in wheat flours. However, cooked rice stales and becomes hard within 24 hrs of cooking; arresting the staling process would allow cooked rice of good quality and practicable shelf life to be offered.

Much remains to be understood to control staling so that it can either be stopped when it has reached as desired level or completely inhibited.

Moisture migration limits the shelf life of many products where a high moisture region is in contact with a low moisture region. The manufacturer is unable to give consumer the experience of a fresh baked product.

The pastry is designed to be hard and brittle to contrast with the moist and malleable meat content. Around the meat, a high moisture jelly is injected after baking. Within a few days, moisture migrates from the jelly into the pastry and the case becomes soft, losing flavor and texture contrast with the filling.
Loss of Quality