Aseptic Packaging
The term aseptic is derived from the Greek word septicos which means the absence of putrefactive micro-organisms
. Aseptic means sterile or free of bacterial contamination. Aseptic is commonly used to describe food processing and packaging techniques for non-refrigerated storage or long-life products.
In practice, generally there are two specific fields of application of aseptic packaging technology:
1. Packaging of pre-sterilized and sterile products. Examples are milk and dairy products, puddings, desserts, fruit and vegetable juices, soups, sauces, and products with particulates.
2. Packaging of non-sterile product to avoid infection by micro-organisms. Examples of this application include fermented dairy products like yoghurt.
Aseptic packaging technology is fundamentally different from that of conventional food processing by canning. Conventional canning renders food products commercially sterile, the nutritional contents and the organoleptic properties of the food generally suffer in the processing. Moreover, tinplate containers are heavy in weight, prone to rusting and are of high cost.
Advantages of
Aseptic Packaging TechnologyThe three main advantages of using aseptic packaging technology are:
Packaging materials, which are unsuitable for in-package sterilization, can be used. Therefore, light weight materials consuming less space offering convenient features and with low cost such as paper and flexible and
Semi-rigid plastic materials can be used gainfully.
Sterilization process of high-temperature-short time (HTST) for aseptic packaging is thermally efficient and generally gives rise to products of high quality and nutritive value compared to those processed at lower temperatures for longer time.
Extension of shelf-life of products at normal temperatures by packing them aseptically.
Besides the features mentioned above, additional advantages are that the HTST process utilizes less energy, as part of the process-heat is recovered through the heat exchangers and the aseptic process is a modern continuous flow process needing fewer operators.
Aseptic Processing MethodologyAseptic processing comprises the following:
Sterilization of the products before filling
Sterilization of packaging materials or containers and closures before filling
Sterilization of aseptic installations before operation (UHT unit, lines for products, sterile air and gases, filler and relevant machine zones) Conventional Process Flow Aseptic Process Flow
Maintaining sterility in this total system during operation; sterilization of all media entering the system, like air, gases, sterile water
Production of hermetic packages
Sterilization of Products
Ultra-high temperature processing or (less often) ultra-heat treatment (both abbreviated UHT) is the partial sterilization of food by heating it for a short time, around 12 seconds, at a temperature exceeding 135C (275F), which is the temperature required to kill spores in the product.
With subsequent cooling, usually to ambient temperature and sometimes to an elevated temperature to achieve right viscosity for filling. Heating and cooling should be performed as rapidly as possible to achieve the best quality, depending upon the nature of the product. A fast heat exchange rate is desired for cost reasons.
Various heat transfer methods are used, but essentially the systems can be divided into direct and indirect heat exchange methods. Table 1 summarizes the characteristics of the heat exchange systems used for aseptic processing of liquids.
Filling
Once the product has been brought to the sterilization temperature, it flows into a holding tube. The tube provides the required residence time at the sterilization temperature. The process is designed to ensure that the fastest moving particle through the holding tube will receive a time/temperature process sufficient for sterilization.
A deaerator is used to remove air, as most products, which are aseptically processed, must be deaerated prior to packaging. The air is removed to prevent undesirable oxidative reactions, which occur as the product temperature is increased during the process. The deaerator generally consists of a vessel in which the product is exposed to a vacuum on a continuous flow.
The sterilized product is accumulated in an aseptic surge tank prior to packaging. The valve system that connects the surge tank between the end of the cooling section and the packaging system, allows the processor to carry out the processing and packaging functions more or less independently. The product is pumped into the surge tank and is removed by maintaining a positive pressure in the tank with sterile air or other sterile gas. The positive pressure must be monitored and controlled to protect the tank from contamination.
Seals and Closures
Any aseptic system must be capable of closing and/or sealing the package hermetically to maintain sterility during handling and distribution. The integrity of the closure and seal is therefore of paramount importance. The integrity of the heat-seals used in most aseptic systems is principally influenced by the efficiency of the sealing system used and by contamination of the heat seal area by the product. To avoid recontamination, the production units, which are tight are required. Maintenance and preventive maintenance is needed to ensure satisfactory seam quality as well as to prevent damage of the packaging material in general, which may interfere with the tightness of the container. Thus, units are produced which are sufficiently tight to prevent re-infection of the product.
Types of Aseptic Packs
Food
A great variety of packages may be aseptically filled now as listed.
Carton Boxes: Some of the existing aseptic carton boxes may now be filled with particulates, also aseptically.
Bags and Pouches: Pillow pouches are usually used for packaging of milk; three-sided sealed pouch, however, is suitable also for aseptic packaging of particulates up to particle sizes of 12 and bag sizes from 1-5 liters. For standing pouches machine uses closed pouches from a reel with sterile interior surfaces, the exterior of which is sterilized in a hydrogen peroxide bath when the web with pouches enters the aseptic cabinet. The bags are then cut from the web, filled and sealed.
Special Need of Plastics in Aseptic Packaging
Packaging for aseptic was particularly demanding of the long shelf-life, high seal integrity and consumer appeal. However, because plastic material is so important to aseptic packaging, it is useful to discuss some special properties demanded of plastics by aseptic process itself. They are as follows:
Chemical resistance and wettability
Thermal stability
Low levels of contaminating microorganisms; and
Resistance to ionizing radiations
Package Structure and Composition
Aseptic package has not only to protect the product but also to maintain the quality of the product. Hence the structure as well as composition of aseptic packaging are more complex and vary depending on product application, package size and package type. Factors such as seal strength and integrity, package shape, stiffness and durability, as well as barrier properties determine the choice and/or combination of materials required. Generally to achieve all required properties, aseptic packages incorporate more than one material in the structure that is assembled by lamination or co-extrusion process. Examples of some materials commonly used in aseptic packaging are given in Table 2.
by: Sandeep
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