Food Technology | Chemical Technology - Chemical Engineering PDF Download

34.1 Introduction

Food technology has evolved into an interdisciplinary area of applied science and engineering based on chemical engineering and food science. India is primarily based on agriculture. The demand for uniform and high quality  food round the year even at remote places from production centre has led to improved food processing technologies. Food industries are almost double the size of chemical industries.

34.2 Food industries can be divided into following sections: 

• Consumer food industry (confectionaries, cocoa products, bakery products, soft drinks etc.)
• Grain processing
•  Marine products
• Dairy products
• Poultry and meat products
• Fruit and vegetable processing
• Fats and oils
• Sugar

34.3 Emphasis of food industries 

Food industries emphasize on four different operations namely food storage, food processing,  food transport and food preservation. 

(i) Food storage

Food storage includes improved storage of food such as refrigeration cycles, refrigerants, and better insulation. Food industries process the raw materials as soon as they are recovered. Sometimes due to unavoidable circumstances such as early arrivals, non-availability, market price considerations which change according to time, the raw materials have to stored before processing.

The storing area should be well ventilated, shaded, should use water baths, and if necessary, cold storage must be used. Before storage, all bruised, shriveled, discolored or soured portions should be removed.

(ii) Food Processing
Food processing involves conversionof raw plant and animal tissues into edible ingredients and separation of inedible and hazardous components, extraction or concentration of nutrients, flavors, colors and other useful components and removal of water.

Table:Classification of Unit Operations of Food Processing

• Sugar obtained from sugar cane is converted to final sugar by refining process.
• Milling is the process of converting grain into powder (flour) by mechanical means.
• In milling operation, grain is cleaned and crushed between two steel rolls. 

(b) Canning:

• Fresh food like fruits, vegetables, meat, fish etc. are preserved for long time storage by heat treatment and sealing into air-tight containers.
• These cans may be made by tin, untinned steel, which is often plastic-lined, aluminium or glass.
• Heat treatment is given to the container by placing them in a steam pressure vessel at a temperature of 121˚C depending on container size and nature of food. · The toxin produced by microorganism is clostridium botulinum. Therefore processing must be done to destroy this organism.

(c) Concentration:

• Foodstuff which naturally contains high percentage of water is concentrated before preservation.
• Milk is evaporated from 8.6% solid content to 45% solid content.
• Fruit juices are also concentrated before marketing.
• Usually the volume is reduced to one- third of the original volume.
• For food concentration three processes are available- evaporation with evaporators, reverse osmosis and freeze concentration.

(d) Freezing:

• Freezing does not kill the microorganisms which cause spoilage, but freezing inactivate microorganisms.
• Nutrients are not destroyed by freezing.
• Inactivation of enzymes by heat treatment(blanching) is done before freezing to prevent unwanted changes.
• To improve the quality of final product, the amount of water in food is reduced before freezing.

(e) Drying:

• Cereal grains, fruits, pastas, milk, coffee, tea, some vegetables and meats are dried.
• After drying volume is reduced to one tenth of the original volume.
• Dried foods are easy to transport and store.
• The nutritive value of dried food is usually unchanged but vitamin content is reduced.
• Microbial growth is controlled.

(f) Pasteurization and sterilization: 

• Heat treatment inactivates the microorganisms but changes the taste of food and its appearance.
• The high temperature short time(HTST) method  exposes the milk to 73˚C for not less than 16sec, followed by rapid cooling. This process is called pasteurization.
• Pasteurization kills pathogenic (disease causing) microorganisms, eliminates food borne disease and inactive enzymes.
• Milk can be stored for several months at room temperature.

(g) Fermentation:

• All organisms are not detrimental.
• Fermentation produces carbon dioxide but no putrid odor.
• Fermentation is decomposition of carbohydrate.
• These industries produce vinegar, wine, beer and other alcoholic beverages. It is also used in making bread, cheese, salting of food etc.

(h) Irradiation:

• Irradiation is required to kill microorganism present in food.
• Irradiation is used to preserve proteinous food such as meat, fish, fresh fruits, vegetables, flour, spices etc.
• Irradiation doesnot denaturate protein, does not alter taste and does not leave any radioactive residue in the food. 
• Loss of vitamins is less as compared to canning, freezing or drying.

(i) Packaging:

• The objective of packaging is to store and transport safely without deterioration of food.
• Containers are sealed so that no outside contaminant can enter and cause food spoilage.
• Cardboard boxes, cans, glass bottles, polythene, plastic coated paper, finely woven cloth are commonly used for packing.