Packaging retortable-pouch

T oods packaged in flexible containers and processed for commercial sterilization are a part of the trend toward improved quality in convenience foods. The retorted pouch has the package integrity of the metal can coupled with the food quality, reheating, and serving convenience of frozen, boil-in-the-bag foods (1). Its use for combat rations has especially interested military R D personnel because of the functional advantages over the metal can (2). 

Flexible multilayer packaging is used for retort processing of various food products. These retort pouches are capable of preserving their contents for many months up to 1-2 years. A layer of aluminium foil normally provides the primary barrier properties of the packaging. A typical structure would be PET polyester ( 18 p,m)/print 5 pm/adhesive 3 pm/aluminium foil ( 20 pm)/adhesive 4-5 pm/cast PP 30 pm. 

The latest feature in food packaging is the retortable pouch as a replacement for an open topped can. At the moment economics are improving as the cost of steel and tinplate rises. However, filling speeds for pouches are considerably lower and additional strength outers (for stacking) add to the cost. 

Other kinds of heat-based sterilization are used in food apphcations. For instancy retortable packaging is typically exposed to 120°C for 30 minutes or more in retort sterilization treatments that cook the food inside the package Used for hotels, restaurants, and the military, retortable pouches are made from multilayer films combining layers of POs and other polymers (see Case 16.1) [16-6]. 

SUITABILITY OF POLYMER-BASED RETORTABLE POUCHES FOR PACKAGING OF FISH PRODUCTS... 

The total thickness of the pouch and individual thickness of the different layers of all the retort pouches are presented in the Table 2. It has been observed that there is not much variation of thickness of pouches of individual layers from one laminate to another. The thickness of different pouches ranged from 135-110 pm for the opaque retort pouches and 150-120 pm for the clear pouches. Both imported and indigenous pouches were having uniform thickness throughout the same specimen. The OP-B pouch was having one extra nylon layer apart from polyester, aluminum foil, and cast polypropylene layer. In case of clear pouches, CP-C had only two layers that is polyester and CPP, whereas in CP-A, there were three layers, where the outer polyester layer was coated with aluminum oxide and nylon was also present. In the case of CP-B, the polyester layer was quoted with silicon dioxide. The thickness of the pouch had a direct influence on the heat penetration characteristics and product quality. Non uniform thickness can affect the machine performance, product protection, and integrity of the packages (Hemavathi, Anupama, Vani, Asha, Vijayalakshmi, Kumar, 2002). The... 

Lampi, R. A. Retort pouch. The development of a basic packaging concept in today s high technology era. J. FoodProc. Engg., 4, 1-18 (1980). 

Ravishankar, C. N., Gopal, T. K. S., and Vijayan, P. K. Studies on heat processing and storage of seer fish cuny in retort pouches. Packag. Technol ScL, 15, 3-7 (2002). 

Bindu, J., Gopak T. K. S., and Nair, T. S. U. Ready to Eat Mussel Meat Processed in Retort Pouches for Retail and Export Market. Packag. Technol. Scl, 17, 113-117 (2004). 

Gopakumar, K. Retortable pouch processing. K. Gopakumar (Ed.), Fish packaging technology, materials, and methods, Concept publishing company. New Delhi, pp. 113-132 (1993). 

Vijayalakshmi, N. S., Sathish, H. S., and Rangarao, G. C. P. Physico-chemical studies on indigenous aluminum foil based retort pouches vis-a -vis their suitability for thermal processing. Popular plastics Packaging, 48, 71-74 (2003). 

Therrtial Sterilization of Pouches of Beef. Methodology for food thermoprocessing in cylindrical metal containers assured food sterility in flexible packages. Beef slices (1.25 cm thick) were steam cooked to an internal temperature of 72°C and vacuum sealed in pouches to give a fill of 120 g. These pouches of beef were processed in a standard retort with complete water circulation and a superimposed air pressure of 1.7 X 105 Pa. The retort schedule—a 40-minute cook at 118°C plus come-up time followed by a 30-minute cooling time—achieved a F0 (lethality value) of 6. 

This information is utilized today in barrier packaging encompassing EVAL resins as the premier barrier resin for applications including retort, hot-fill and aseptic packaging in film, pouches, bottles, thermo-formed sheet and molded applications. Foods include tomato products, juices, sauces, barbeque sauces, salad dressings, apple products, cranberry products, meat, cheese flavoring and fish products. Other applications include pesticides, medical and pharmaceutical, and chanical products. These applications are expanding daily. 

The packaging for the military s ration, the Meal, Ready-To-Eat (MRE) has stringent performance requirements which must be met in order for the food to maintain quality and nutrition. The MRE must have a shelf life of three years at 27°C or six months at 38°C. [1] The military specification requires that the oxygen transmission rate (OTR) of the packaging must not exceed 0.06 cc/mVday and the water vapor transmission rate (WVTR) must not exceed 0.01 g/mVday. Also, the MRE food pouches are retorted at 121°C (250°F) for 30 to 60 minutes, which are the typical conditions required to kill microorganisms and sterilize the contents. [2, 3]... 

In order to meet the military performance specification, a foil laminate structure is currently used in the MRE food pouch. However, current research is investigating alternative multilayer polymeric packaging structures. [4, 5] Ethylene co-vinyl alcohol (EVOH) is one polymer that is being researched. EVOH is a crystalline, random copolymer of ethylene and vinyl alcohol. EVOH is known to be a superior barrier to oxygen however the barrier properties of EVOH diminish as the humidity increases. Also, the hydrophilic nature of the material becomes a problem with retort packaging applications because the process requires water and steam for sterilization. EVOH resins absorb moisture as a function of humidity and temperature, decreasing the barrier properties of the resin during the retort process. 

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