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 Technology
The 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 Methodology
Aseptic 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.
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.