Aseptic Packaging of Food Products

In comparison to classical canning, aseptic packaging is preferred for heat sensitive and nutritional foods & beverages for obtaining a finished product with better sensory qualities and higher nutrient retention explain R Sharma and S. Balasubramanian

The term “aseptic” implies the absence or exclusion of any unwanted organisms from the product, package or other specified areas, while the term “hermetic”(strictly “airtight”) is used to indicate suitable mechanical properties to exclude the entrance of microorganisms into a package and gas or water vapour into or from the package. Aseptic packaging thus can be defined as filling the commercially sterile products into sterile containers under aseptic conditions and sealing of the containers so that the re-infection is prevented, i.e. so that they are hermetically sealed. There are two specific fields of application of aseptic packaging:

Reasons for Use of Aseptic Packaging

• Historical Development
• Aseptic Filling System
• Aseptic Packaging Systems
• Pack Selection and Pack Criteria

Criteria for Aseptic Packaging of Foods

• Packaging of pre-sterilized and sterile products: e.g.: dairy and milk products, puddings, desserts, fruit and vegetable juices, soups, sauces.
• Packaging of nonsterile product to avoid infection by microorganisms: e.g.: Fresh products such as fermented dairy products like yoghurt
• Aseptic packaging enables containers to be used that are unsuitable for in-package sterilization;
• The advantage of high-temperature-short-time sterilization processes which are thermally efficient generally give rise to the product of superior quality compared to those processed at lower temperatures longer times
• It extends the shelf life of products at normal temperatures by packaging them aseptically.

In comparison to classical canning, aseptic packaging is preferred for heat sensitive and nutritional foods & beverages for obtaining a finished product with better sensory qualities and higher nutrient retention. Nielsen carried out the first aseptic packing of foods (especially milk in metal cans) in Denmark prior to 1913 and in 1921 patent for this process (termed aseptic conservation) was granted. In 1917, Dunkley in the USA patented sterilization with saturated steam of cans and subsequent filling of pre-sterilized product. In 1923, aseptically packaged milk from South Africa reached a trade fair in London, England in perfect conditions. The American can company developed a filling machine in 1933, called the Heat-Cool-Fill (HCF) system which used saturated steam under pressure to sterilize the cans and ends.

The sterile cans were filled with sterile products and the ends sealed on in a closed chamber, which was kept pasteurized with steam or a mixture of steam and air. Three commercial plants were built and operated on this principle until 1945. In the 1940’s, Martin developed a process in which empty metal cans were sterilized by treatment with superheated steam at 2100C prior to being filled with cold, sterile product. In 1950, the Dole Company bought the first commercial aseptic filling plant on the market. At the end of 1940, a dairy enterprise and machinery manufacturers in Switzerland (Alpura Ag, Bern, and Sulzer Ag, Winterthur) combined to develop UHT-sterilized, aseptically canned milk, which was marketed in Switzerland in 1953. However, this system was not economical mainly because of the cost of the cans.

Long shelf life milk packaged in this manner was first sold in Switzerland in October 1961. An aseptic filling system must meet a series of requirements, each of which must be satisfied individually before the whole system can be considered satisfactory. The container and method of closure must be suitable for aseptic filling, and must not allow the passage of organisms in the sealed container during storage and distribution. It is also desirable for the container to have certain physical properties that will help in minimizing chemical changes in the product during storage.

• The container or part of it exposed to the product must be sterilized, after it is formed and before being filled.
• The level of sterilizing effect is related to the probable initial contamination of the container surface. The container sterilization process may be single-stage, either within the aseptic filler as apart of its operation or as a preliminary process or it may be two-stage with the second stage forming part of the filler operation.
• The container must be filled without contamination by organisms either from the equipment surfaces or from the atmosphere that surrounds the filler. Filling is done in an enclosed area that is supplied with a sterile atmosphere (air sterilized by heating or filtration).
• If any closure is needed, it must be sterilized immediately before it is applied.
• The closure must be applied and sealed in place to prevent the passage of contaminating organisms, while the container is still within a sterile zone.

Aseptic packaging system

The aseptic packaging system must be capable of filling the product produced by the HTST or UHT system in an aseptic manner and sealing the container hermetically so that sterility is maintained throughout the handling and distribution processes. Any aseptic packaging system should be however capable of meeting the following four criteria.

1) It should be able to be connected to the processing system in a manner that enables the aseptic transfer of product to take place. 2) It could be able to effectively sterilize before use. 3) It could be able to carry out the filling, sealing and critical transfer operations in a sterile environment. 4) It must have the ability to be cleaned properly after use.

The type of packaging material used is influenced by the nature of the product, the cost of both the product and the package and the preferences of the consumer. The most widespread consumer package for aseptic products is the paper-based carton, which is used for many dairy products, fruit juices and other beverages. In addition to retail or consumer aseptic products, bulk-packaging systems are in use for products, which are then further processed and/or repacked into consumer-sized packs.

Before considering the packaging material themselves, it is instructive to consider the various functions that retail food package is called on to perform. Although there are more than hundred different aspects to be considered when developing a new package, these may be conveniently grouped under twenty-two headings. The greatest demands on packaging arise from the requirements of perishable foods such as milk, fruit juice, vegetables in brine, and so on, which have been processed to give long shelf-lives at ambient temperatures.

Criteria for Aseptic Packaging of Foods

Canned and aseptically packed foods come under this category, and a package of an aseptic food will certainly need to fulfill the following criteria;

• It should contain the product.
• It should prevent physical damage to the packaged product. It should run smoothly on filling lines.
• It should withstand packaging processes.
• It should be easy to handle throughout the distribution process.
• It should prevent dirt and other contamination.
• It should be able to protect the product from odours and taints.
• It should be resistant to rodent attack.
• It should be able to stop insect infestation.
• It should be biologically safe i.e. non-toxic.
• It should be compatible to foodstuff.
• It should provide sterility for the product.
• It should prevent the ingress of microorganisms.
• It should show evidence of tampering.
• It should control moisture loss or gain.
• It should offer a barrier to oxygen.
• It should be protective against the light.
• It should maintain gas atmospheres, i.e. CO2/N2.
• It should communicate all the information regarding the product and manufacturers.
• It should have a good sales appeal.
• It should be easy to open.
• It should be cost-effective.

The above-given pack criteria are separated into seven areas, mainly as follow:

• Product containment: The need to contain the product in the sense that liquids or powders do not leak out is obvious.
• Physical protection: This is again obvious when dealing with fragile foods like eggs or snack foods, but minor impacts on fresh fruits, for example, will release enzymes and lead to browning and softening. Equally important is the adverse effects on sales of damaged packages themselves-even though the product is in good condition.
• Food safety: The need to ensure that the aseptically packed food retains its sterility, through a package that prevents adventitious contamination by microorganisms is very important. Tamper evidence is also now, unfortunately, a desirable requirement, in the face of malicious contamination situations. The other aspect of food safety is the avoidance of long-term chronic effects from the food packaging materials themselves.
• Shelf-life: For dried foods moisture gain is a major factor in determining shelf-life, atmospheric oxidation, often catalyzed by light, is more critical for aseptically packed foods such as milk, fruit juices, or cream soups. Hence good oxygen and light barrier, as provided by tinplate or aluminum foil, is needed to ensure maximum shelf life for these products.
  However, shelf life can be determined by marketing considerations as less than the technically available maximum. This could occur in situations where, for example, a plastic container preferred for sales purposes could not give the shelf life of glass or metal packaging.
• Communication of information: The package should need to tell the purchaser what food is inside it and whose product it is. Apart from this, more information should be passed on to the customer, such as net weight, list of ingredients, batch number, use-by date, nutritional information, and so on.
• Sale-appeal: The package must look attractive and ‘catch the eye’ of prospective purchasers, and it should also be easy to open and dispense the product.
• Cost-effectiveness: Value for money in packaging is more important than looking for the lowest price. A cheap but dimensionally variable container could cause more downtime during production or an increase of ‘leakers’ in the market place, thereby negating the apparent cost-saving. Conversely, spending more to make a pack look more attractive could be justified in increased sales.

Comparison of Various Packaging Material

The main types of packaging materials are compared and it is apparent that technically there are many options available in a given packaging situation (Table 1). In addition, while, conformance with all of the 19 technical criteria is not always essential, the three commercial aspects can never be ignored in today’s free market. Hence a final decision on which form of packaging should be used will invariably involve marketing and sales considerations.

Major Categories of Aseptic Packaging Systems

Can system: It includes hermetically sealed cans

Bottle systems: Glass containers and plastics bottles fall into this category. The bottles can further be divided into; a) Non-sterile bottles; b) Sterile blown bottles; c) Single station blowing, filling & sealing

Sachet and pouch systems: This system classified into Form-fill-seal systems and Lay flat tubing

Cup systems: The aseptic packaging of food into cups can be into; Pre-formed plastic cups; and Form-fill and seal cups

Carton systems: This type of aseptic packaging system includes form-fill-seal cartons and Prefabricated cartons

Bulk packaging systems: This type of system classified into; Metal drum; and Bag-in-box Packaging Lines for Aseptic Processing There are five basic types of aseptic packaging lines as given below;

Film & Seal: Pre-formed containers made up of thermoformed plastic, glass or metal are sterilized, filled in an aseptic environment and sealed.

Form, Fill & Seal: Roll of material is sterilized, formed in a sterile environment, filled and sealed. e.g. Ex tetra packs n Erect, Fill & seal: Using knocked, down blanks, erected, sterilized, filled sealed. e.g. Ex. Gable-top cartons, Cambri-block.

Thermoform, Fill, sealed roll stock, sterilized, thermoformed, filled, sealed aseptically. e.g. Ex. Creamers, plastic soup cans.

Blow, Mold, Fill & Seal. e.g. Different package forms used in Aseptic UHT processing are cans, paperboards/plastic/foil/plastic laminates/flexible pouches, thermoformed plastic containers, bag in box, bulk totes.

TABLE 1 Comparison of Various Packaging Materials

Materials Technical advantages

Glass Impermeability, inert material, product visibility, axial strength, withstands vacuum/pressure

Conclusion and Scope of Aseptic Packaging

There are a number of limitations and disadvantages during the actual application of this technology. However, we can’t ignore the advantages of various lacunas of the process. Thus, it can be concluded that aseptic packaging of sterile/non-sterile food and food products is the most significant innovation in the field of food science and technology and there is a big scope in this area.