Retort Packaging

Boiling Water

 

Introduction

 

The form of food has evolved due to internal and external factors such as lifestyle changes among consumers and advancements in food manufacturing processes. The demand for convenience in food is on the rise, which has been identified as an accompanying risk factor for food safety. Reduced cooking processes mean increased potential contact with living microorganisms in food, which in turn can lead to exposure to diseases.

 

To overcome this challenge, many products are adopting methods to eliminate or annihilate microorganisms during the manufacturing process, ensuring consumer safety. This is referred to as sterilization and pasteurization. Pasteurization removes harmful microorganisms but not completely, slowing down their growth rate, while sterilization involves the complete elimination of harmful microorganisms.

 

Even with sterilization and pasteurization during processing, any subsequent contact with external harmful microorganisms would negate the process, making the development of packaging that prevents such contamination necessary. This has led to the introduction of retort food packaging. So, what exactly is retort packaging?

 

Retort

 

Retort food refers to food that is sterilized under high temperature and pressure and then packaged. The name derives from the retort, a round bottle used in chemical experiments where this process was first applied. Invented in the 19th century, this method is used to provide fresh and long-lasting food in areas where it is challenging to do so, such as the military or disaster zones.

 

The manufacturing process of retort food is as follows. The food is placed in retort packaging material, which is usually made of aluminum foil and plastic, capable of withstanding high temperatures. The packaged food is then placed in a retort machine under high temperature and pressure for sterilization, killing most harmful microorganisms. After sterilization, the food is packaged and stored for transportation. The sterilization process for retort food typically occurs at 121℃ for 15 minutes, a level that kills most microorganisms, thus extending the safety and shelf life of the food.

 

Retort Packaging For sterilization, the packaging must withstand temperatures above 121℃ and pressures over 2bar. This requires materials with high melting points. For instance, although polyethylene (PE) with a melting point (Tm) above 121℃ can be used, in practice, the actual temperature of the content can locally exceed 121℃, causing melting in areas where the film's heat resistance is weaker. Therefore, for safe sterilization, polypropylene (PP) with a melting point above 160℃ should be used. This material, typically a composite PP, has higher heat resistance but is relatively rigid and challenging to extrude, requiring specialized technology and additional processing settings.

 

Once manufactured and placed in contact with the content, the packaging can withstand the heat of sterilization. After sterilization, to maintain sterility, tight packaging that prevents external intrusion is necessary. Aluminum (Al) is commonly used for this purpose. Its metal structure and dense arrangement make it difficult for even small microorganisms and molecules like air to penetrate. However, using thick aluminum (over 12 microns) can be challenging in packaging due to its rigidity and significantly increased cost.

 

Aluminum is also prone to tearing and puncturing, requiring the use of an additional film layer. To compensate, polyamide film, commonly known as nylon film, is used, and PET is often used for appearance quality, printing, and heat resistance. Typically, a PET/Al/Nylon/CPP structure is common, but configurations without Al, using Alox-coated PET film, exist for characteristics like microwave cooking.

 

Conclusion

 

While the sterilization of the food itself is crucial, delivering it safely to consumers largely depends on the packaging. The composition of packaging material must be understood to convey safety to consumers, and awareness of environmental impact is necessary to avoid over-packaging. Understanding packaging allows us to infer the characteristics, consumption methods, and storage of the contents. Therefore, food storage and packaging mutually enhance understanding and influence each other.

 

Today, we explored retort food packaging. Technical details not covered here will be addressed in future writings, as they are extensive and often not practically useful for consumers. If you have any questions or messages, please leave a comment.