The products prepared by this method can be retained from a few days to a month because the spoiling organisms are partially killed or their growth is inhibited for a short period. The use of various temporary preservation methods are depends on the product to be kept temporarily.
i) Asepsis or Absence of Infection:
The number of microorganisms present in food product largely initiates spoiling process while handling the fruits and vegetables for manufactures of the products. The general cleanliness while picking , grading , packing , and transportation of raw material increases the keeping quality of fruits and vegetables. Washing or wiping of the fruit and vegetables before using in manufacture should be strictly followed as the dust particles adhering to the raw material accompany micro organisms. Maintain hygienic conditions at all stages during preservation.
ii) Low Temperature:
The low temperature, 0 0 to 4.4 0C , check the growth , multiplication and actively of microorganisms, but to do not kill them. It also retards chemical changes to a greater extent. Ex. Cold Storage.
iii) Exclusion of Moisture:
Moisture is one of the favourable things for the growth of microorganisms specially moulds. It plays a great role in dried products as it collects on the surface and results in micro organism’s growths. Moisture is also responsible to dilute the concentrated sugar solutions which are generally without preservatives. It is , therefore, essential to save the product from moisture and should be stored in a dry atmosphere.
iv) Exclusion of Air:
The air is also necessary for growth of microorganisms. If the products are saved from air prolong the keeping qualities especially fruit products. Aerobic organisms cause great spoilage if they get external air. So fermented products and pickles must be created in air- tight containers to check their growth.
v) Mild Antiseptics:
The use of antiseptic in small quantities prevents the growth of microorganisms either by osmosis or by poison or by both for a short time or several weeks after opening the bottles.
Light sugar syrup is used in canning of fruits which retains the colour, flavour, and shape of the fruit products. Vinegar and spices check the spoilage of tomato sauce for few weeks after opening of the bottle.
This is a process in which the product is subjected to a temperature that kills a great many, but not all, of the microorganisms present. The heat not only kills many organisms but greatly weakens and delays the development of those not killed, which is an important factor in the keeping of pasteurized products. This is a better method for fruit juices as practically all the microorganism which can grow in liquid are killed by heat.