Canning and Fish Packaging Technology

Unit 5 - Changes in canned foods and spoilage

5.2.2.3.2.Post-processing spoilage
Another microbial spoilage is ‘post-processing spoilage’. In spite of conducting preparation, processing and can cooling in a proper way, sometimes heat processed cans spoil due to entry of microorganisms into the can. Leakage of cans is the only reason for this kind of spoilage. The reasons for this spoilage are

• Loose double seam
• Sudden increase or decrease of pressure in the retorts
• Physical damage at the double seam

As water sucked into the can while can cooling, microorganisms present water get into it and spoil the food. Sometimes, leaked cans close by itself and due to gases produced inside, the cans bulge. Such a spoilage is called as ‘leaker spoilage’. In such cans, a variety of microorganisms (mixture of non-spore formers or spore formers) are present. Addition of 4-7 ppm of free chlorine in can cooling water minimises this spoilage. In air cooling this spoilage is much less than in water cooling.