Aseptic Processing Pdf

[Madeleine Harrier]

Asepticprocessing is a processing technique wherein commercially thermally sterilized liquid products (typically food or pharmaceutical) are packaged into previously sterilized containers under sterile conditions to produce shelf-stable products that do not need refrigeration.[1] Aseptic processing has almost completely replaced in-container sterilization of liquid foods,[2] including milk, fruit juices and concentrates, cream, yogurt, salad dressing, liquid egg, and ice cream mix. There has been an increasing popularity for foods that contain small discrete particles, such as cottage cheese, baby foods, tomato products, fruit and vegetables, soups, and rice desserts.[1]

Aseptic processing involves three primary steps: thermal sterilization of the product, sterilization of the packaging material, and conservation of sterility during packaging.[3] To ensure commercial sterility, aseptic processing facilities are required to maintain proper documentation of production operations, showing that commercially sterile conditions were achieved and maintained in all areas of the facility.[4] Any breach of a scheduled process for the processing or packaging system means that the affected product must be destroyed, reprocessed or segregated and held for further evaluation.[4] In addition, the processing and packaging system must be cleaned and re-sterilized before processing and/or packaging operations can resume. Packaging equipment and packaging materials are sterilized with various media or combinations thereof (i.e., saturated steam, superheated steam, hydrogen peroxide and heat and other treatments).[4]

Aseptic processing was derived from Olin Ball's heat-cool-fill (HCF) machine that was developed in 1927.[5] While HCF was successful in improving the sensory quality of the processed chocolate milk as compared to canned product, the use of the equipment was hindered by its cost, maintenance, and inflexibility to process various container sizes, rendering the machine a failure.[6]

Later in the 1940s, the Dole Aseptic Process was developed by McKinley Martin.[5] The foods processed ranged from soups to specialty sauces, fruits, and dairy products.[6] This process involved four steps:[5][6]

Roy Graves began sterilizing milk in the 1940s. The milk that was drawn from the cow went through a pipeline, into a vacuum tank, which was then heated to 285 F, then cooled to room temperature. The product, packaged in metal cans, was widely accepted by consumers lacking access to fresh milk, including the U.S. military.[7]

In 1959, the food industry saw the advent of the use of paper-foil-plastic laminated containers called tetrahedron. In 1962, the Swedish company Tetra Pak, introduced this container to the United States market. They sold pasteurized milk and beverages in the containers. Roy Graves' company started sterilizing this container with chlorine and were able to aseptically fill and hermetically seal the container. The use of these containers was not accepted by the American consumers due to their difficulty in opening. It was widely used by the U.S. Navy.[7]

Sterilization of aseptic packaging material is a crucial step in aseptic food processing. These containers are sterilized to kill microorganisms present on the container during forming and transport and prior to filling.[8] There are numerous methods used to sterilize the containers, the most commonly used methods include: heat, hot water, chemical sterilants (hydrogen peroxide or peracetic acid), and radiation or a combination of methods.[7][8]

Equipment used in aseptic processing of food and beverages must be sterilized before processing and remain sterile during processing.[1] When designing aseptic processing equipment there are six basic requirements to consider: the equipment must have the capability of being cleaned thoroughly, it must be able to be sterilized with steam, chemicals, or high-temperature water, sterilization media should be able to contact all surfaces of the equipment, meaning the equipment does not contain any cracks, crevices or dead spots, the equipment must be able to be kept in a sterile state, it must have the ability to be used continuously, and lastly, the equipment must comply with regulations.[7]

Aseptic packaging consists of filling and sealing a sterilized packaging material with a sterilized product. Aseptic packaging material not only has to assure sterile conditions within the package and protect the product from physical damage, but also maintain the quality of the product inside the packaging.[8] To achieve this, a laminate material is formed from the following components: semi-rigid paper, aluminum, and plastic.[3] Paper (70%) provides the stiffness, strength, and the efficient brick shape to the package; potential for bacteria needs to be addressed.[10] Low-density polyethylene (24%), the most common plastic used for aseptic packaging, located on the innermost layer forms the seals that make the package liquid-tight. Aluminum (6%) is located on the inside of the aseptic package, forming a barrier against light and oxygen, thereby eliminating the need for refrigeration and preventing spoilage without using preservatives.[11] Most packaging material used in aseptic packaging is made from plastics instead of metal or glass containers due to the relatively low cost of producing plastic material when compared to metal and glass. Plastics are lighter than metal or glass making them cheaper and easier to transport. Plastics also required much less energy to produce than metal and glass.[3] These factors have made plastic the packaging material of choice for use in aseptic processing.

There are a lot of factors that can influence the type of aseptic container chosen for a product. The following factors may influence the choice of packaging material for aseptically processed products: functional properties of the plastic polymer (gas and water vapor barrier properties, chemical inertness, and flavor and odor absorption or scalping), potential interactions between plastic polymer and food product, desired shelf life, economical costs, mechanical characteristics of the packaging material (molding properties, material handling characteristics, and compatibility with packaging and sterilization methods), shipping and handling conditions (toughness, compression), compliance with regulation, and targeted consumer group.[12]

Aseptic processing preserves food quality through fast heat treatment followed by a short holding time and rapid cooling.[1] Compared to canning where food products are subjected to high temperature processing, the fast heat treatment provided by aseptic processing enables heat-sensitive characteristics of the food to be better retained.[1]

The flavor of aseptically processed food products is minimally changed.[1] Dairy products could have a cooked flavor because of exposure to sulfhydryl groups. The flavor is reduced during storage as the sulfhydryl groups oxidize. Severely treated milk could have a bitter flavor because of proteolysis.[1]

Dairy products could have changes in color, an effect caused by Maillard browning. This depends on the amount of reducing sugar, the formation of pyralysins and melanoidins, the severity of the treatment, and the storage temperature.[1]

Fruit juice viscosity is unaffected. Processed sliced fruit and vegetable pieces are softer compared to unprocessed pieces as a result of the solubilization of pectic materials and loss of cell turgor.[1]

Aseptic Processing achieves sterility through a flash-heating process with temperatures ranging from 91 C to 146 C and is minimally processed. Due to the significantly lower processing time and temperature range used in aseptic processing compared to conventional sterilization, such as canning, products that are aseptically processed are able to retain more nutrients.[13] Riboflavin, pantothenic acid, biotin, niacin, and vitamin B6 are unaffected. Approximately 10% of thiamine and vitamin B12, approximately 15% of folic acid and pyridoxine, and approximately 25% of vitamin C are lost during aseptic processing.[1]

Foods that are processed aseptically have better nutritional, vitamin, and natural pigment retention (chlorophyll, anthocyanins, betalains, carotenoids) compared to canned food products because of the lower temperature the foods are subjected to upon processing.[1] Aseptic processing provides flexibility in using various container sizes as well as possibility of addition of bioactive and heat-sensitive components after processing (probiotics, omega-3 fatty acids, conjugated linoleic acids).[1]

Aseptic processing costs more than canning because sterilization of the packaging materials requires different machinery and can get complex.[1] In addition, maintaining air sterility in the processing room is difficult.[1]

Inspections of aseptic processing is one of the most complex inspection of food manufacturing operations. Process authorities are required to establish a process that ensures commercial sterility for the following:

The general regulatory requirements for all U.S Food and Drug Administration (FDA) regulated foods are found in section 21 of the U.S. Code of Federal Regulations (CFR) Part 117. Section 113.40 lists specific requirements for aseptic processing and packaging systems, including specifications for equipment and instrumentation. One requirement of the FDA regulations is that all thermal processing operations must be conducted under the operating supervision of an individual who has completed an FDA-approved course of instruction on control of thermal processing systems, container closures, and acidification procedures. The Better Process Control School provides a section on aseptic processing and packaging systems, and will meet the FDA requirement for supervisors of aseptic operations.[14]

Processing authorities are responsible for aseptic systems must be aware of certain factors unique to aseptic processing and packaging operations, therefore specific knowledge in this area is essential. Neither the FDA nor other regulatory agency maintains a list of recognized processing authorities, however, certain organizations are widely recognized within government agencies and the industry as having the experience and expertise. The FDA regulations rely upon aseptic processing and packaging authorities to establish parameters for sterilization of product, packages, and equipment so that commercial sterility of the end product is assured.[14]

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