Processing of Horticultural Crops

Introduction

Introduction
The term canning refers to a process which involves heating food stuff in hermetically sealed containers for a specific time at specific temperature to eliminate microbial pathogens that endanger public health and micro-organisms as well as enzymes that deteriorate food during storage.

History of canning: Important historical developments in canning are as under:

• The credit for invention of canning goes to Nicholas Appert, a French confectioner who was awarded a prize in 1809 by the French government for developing new method of heat preservation of food in sealed container and after whose name the process of canning is known as Appertization.
• In year 1810, Appert published the first book on canning entitled “The Art of Preserving Animal and vegetable substances for many years” which is the first known work on canning.
• The work of Appert consists of packing food in glass bottles, closing with corks and heating the container in boiling water for several minutes depending upon the type of the food.
• In 1810, Peter Durand got first British Patent on canning of foods in tin or metal containers.
• In 1813, Doukin, Hall and Gamble introduced the practice of post processing incubation of canned foods.
• In 1825 T Kensett and E Duggett were granted US patent for preserving food in cans.
• In 1825, Thomas Kenett, an American developed first kettle pan.
• 1837 Winshow was first to can corn from cob.
• 1839 Tin cans came into wide use in limited states.
• 1845 S. Elliott introduced canning in Australia.
• Louis Pasteur (1864) discovered that food spoilage was caused by micro-organisms which were destroyed at elevated temperature and technique was known as Pasteurization. This understanding helped to form a scientific basis for establishing and revolutionizing the canning industry.
• 1873 Andrew Shriver developed first retort pressure cooker.
• 1890 Max Ann developed first double seaming machine.
• 1895 Russel made first bacteriological study of canning.
• 1916 Bitting gave the index of processing time and temperature relationships for food products.
• 1920 Ball, a mathematician developed mathematical calculation for heat sterilization.
• 1921 Magoon and Culpepper, horticulturist by trade, gave idea of exhausting and vacuumin processed products.
  
• 1928 Heat process calculations were completed for the canning industry.
• The civil war in America and later the Boer war and the Great European war of 1914 with their enormous requirement of foods for the fighting forces gave a further impetus to the canning industry.

Presently large quantity of fruit, vegetables, meat, sauces, and confectionary products are preserved by canning. There is a great scope for the development of canning industry as it is one of the processes which does not involve the use of any chemical in preservation.

Manufacturing of cans: Metal cans are mainly used in the national and international trade for canning of fruits and vegetables. Open top sanitary (OTS) cans are made from tin plates which are very thin sheets of steel lightly coated with tin (0.00025 cm thick) on both sides. Tin can is cut into proper sizes with a trimming and slitting machine. The pieces provide body blanks. After notching and slitting, the flat can body is passed through an edging machine where hooks are formed. The can body is then bent into a cylindrical shape and side seam is soldered. These operations are carried in the can manufacturing factory. Now the cans are supplied in the flattened form to the users to lower the packing and transportation costs. The can ends are supplied separately along with the cans.

During preparation of can, the first step consists of reforming the cans in can reformer to give them a cylindrical shape. The cans are then flanged by using a flanger, which curls the rims/edges outward at each end. One end of the can is now fixed to the flanged can body by means of a double seaming machine which firstly form the seam and secondly tightens it. The finished cans are now tested for any leaks with the help of a vacuum/air pressure tester. Finally, after the filling of the cans with fruits or vegetables the second lid (end cover) after coding is fixed similarly for airtight sealing of cans.

The empty can after placing lid on both the sides can be tested for any leakage by using empty can tester. For testing, the probe of empty can tester is sealed empty can to which air is pumped to about 15-20 psi. Any leakage is judged by immersing can in water. In case of any leakage, the defect in the double seamer needs to be rectified before starting any production. Different sizes of the cans used in canning are showed in Table-7.1.

Table7.1: Trade name and sizes of cans used in canning of fruits and vegetables.

Trade name	Trade size	Size mm
A1	211×400	68×102
1 lb jam	301×309	78×90
A1 tall	301×411	78×119
A2	307×408	87×114
1 lb butter	401×212	103×70
2 lb jam	401×400	103×102
A 2 1/2	401×411	103×119
7 lb jam	603×513	157×148
A10	603×700	157×178