FLEXIBLE RETORT POUCH DEFECTS Identification and Classification Manual Chapter Page Foreword 1 Flexible Retort Pouch Defects Status Date Identification and Classification New 31/05/2002 FOREWORD An important element in the production of any safe, wholesome and good quality pouched product, is that each pouch meets recognised standards. This flexible retort pouch defect identification and classification manual has been prepared in order to: 1. clarify current regulatory requirements for classification of flexible pouch defects; 2. provide information to assist in the communication of issues associated with the integrity of hermetically sealed flexible retort pouches, testing procedures for seal strength and integrity; and 3. provide a standard terminology and description for industry and government inspectors. This manual provides for standardised classification criteria as well as uniform terminology for the assessment of flexible retort pouches. It also provides details of the various tests, against which a flexible retort pouch may be assessed. It is important to understand that not all of the tests are required to be performed by the processor as part of their quality control system. 31/05/2002 Flexible Retort Pouch Defects Identification and Classification Table of Contents 1. INTRODUCTION 2. GENERAL 2.1 Background 2.2 Pouch Material Characteristics and Specifications 2.1.1 Basis Weight of the Laminate 2.2.2 Laminate Tensile Strength 2.3 Pouch Laminates 2.4 Types of Pouches 2.4.1 Pre-formed Pouches 2.4.2 In-line Formed Pouches 2.5 Container Terminology 3. INTEGRITY FACTORS 3.1 Pouch Filling 3.2 Exhausting the Filled Pouch 3.3 Seal Formation 3.3.1 Hot Bar Sealer 3.3.2 Impulse Sealer 3.4 Handling of Closed Pouches 3.5 Post-process Pouch Handling 3.5.1 Pouch Drying 3.5.2 Outer Wrapping 3.5.3 Transit Packaging 31/05/2002 Flexible Retort Pouch Defects Identification and Classification Table of Contents 4. EXAMINATION AND EVALUATION PROCEDURES 4.1 Container Examination and Tests 4.1.1 Visual Examination 4.1.2 Static Load Burst Test 4.1.3 Internal Burst Test 4.1.4 Tensile Testing 4.1.5 Residual Air Test - Destructive Test 4.1.6 Residual Air Test - Non-Destructive Test 4.1.7 Dye Test 4.1.8 Incubation Test 4.1.9 Gas Leak Detection 4.2 Inspection of Sealed Retort Pouches 5. DEFECT SEVERITY CLASSIFICATION 5.1 Serious Defect 5.2 Minor Defect 6. INDEX/GLOSSARY 7. DEFECT CATEGORIES 8. BIBLIOGRAPHY Chapter Page 1 1 Flexible Retort Pouch Defects Status Date Identification and Classification New 31/05/2002 CHAPTER 1 INTRODUCTION This is a compliance manual for flexible pouch defect identification and classification. It is intended as a reference manual for use by quality control and inspection personnel tasked to evaluate the integrity of flexible retort pouches. Container integrity is the ability of an hermetically sealed container to deliver safe wholesome food to the consumer. Container integrity may be compromised by a wide variety of defects. These defects may arise throughout the various stages of container manufacturing, filling, sealing, processing, and handling, before the container reaches the consumer. The material in this manual will: 1. provide a basis for assessment of container integrity, by using standard criteria; 2. assist in communicating specific defect conditions, by using standardised terminology; and 3. provide a severity classification of the various defect types, by using standard criteria. These defect classification standards are applicable to both domestic and imported product. This manual also provides some general information on flexible pouch manufacturing (including factors on pouch integrity and thermal processing) and testing procedures, of which inspectors and pouch processors should be aware. The information contained in Chapters 2, 3, and 4 is included for reference purposes; specific compliance standards for processing and thermal processing may be found in the CFIA Facilities Inspection Manual. Chapter Page 2 1 Flexible Retort Pouch Defects Status Date Identification and Classification New 31/05/2002 CHAPTER 2 GENERAL 2.1 BACKGROUND The retort pouch is a flexible laminated food package that can withstand thermal processing. It has the advantage of offering the shelf stability of metal cans, coupled with the texture and nutrient value associated with frozen foods. The retort pouch has been considered the most significant advance in food packaging since the metal can, and has the potential to become a feasible alternative to the metal can and glass jar.16 The U.S. Army promoted the concept of flexible retortable pouches for use in combat rations in the 1950's. The idea was to have a lightweight, easy-to-pack, shelf-stable food container in order to eliminate the heavier traditional can. Research continued through the 1960's. In 1965 the first commercial retort pouches were produced in Italy. In Japan, retort pouch technology has been widely accepted16 and there are many varied products on the shelf, ranging from sukiyaki to soup. Examples of some retort pouches are shown in figure 2.1. The retort pouch has a number of advantages compared to a metal can. 1. The thin profile permits a reduced heating time and thus less of a chance to overcook the product while producing better color, firmer texture and less nutrient loss. The manufacturer has reduced energy requirements for pouch production as compared to that for metal cans.14 The pouch (because of its thinner profile) transfers heat faster to its critical point. During processing, this permits the required amount of heat for proper sterilisation to reach the critical point with minimal overcooking of the product near the peripheral container areas. Thus, for those food commodities subject to quality loss from excessive heating during the process cycle, the flexible container offers the benefit of higher quality together with better retention of the heat-sensitive nutrients. 2. Some pouches have an easy to open notch that eliminates the requirements for can openers and reduces the risk of cuts. 3. Labels can be printed into the laminate, making them permanent. 4. Flexible pouches are easier to distribute and therefore have lower transportation costs and require less disposal space. 5. Storage space for empty flexible pouches is also reduced. A 45 ft. Chapter Page 2 2 Flexible Retort Pouch Defects Status Date Identification and Classification New 31/05/2002 trailer holds 200,000 8 oz cans or 2.3 million retort pouches. The retort pouch system has disadvantages in processing. 1. The first obstacle is that processors often require a large capital investment for the unique machinery. Filling is slower and more complex compared to metal can lines. 2. The thermal process is complex due to the number of critical processing parameters which must be monitored (e.g., residual air, pouch thickness, steam/air mixture). Also, special racking systems may need to be set up in order to provide optimal heating media flow and prevent pouch to pouch contact. 3. Since pouches are more easily punctured they may require over- wrapping for distribution. 4. Specialised equipment such as a burst tester, or a tensile tester is required for leak detection and container integrity evaluation. Figure 2.1 Examples of Retort Pouches Chapter Page 2 3 Flexible Retort Pouch Defects Status Date Identification and Classification New 31/05/2002 2.2 POUCH MATERIAL CHARACTERISTICS AND SPECIFICATIONS The choice of materials for the manufacture of retort pouches is very important. The package must protect against light degradation, moisture changes, microbial invasion, and oxygen ingress and package interactions. The material must have sound structural integrity and be able to withstand retort temperatures as well as normal handling abuse. It must also comply with regulatory requirements. There are approximately 16 basic laminating materials with 100 different possible combinations. Characteristics essential to a satisfactory retort pouch are:   Low gas permeability (oxygen)   Low moisture permeability   Low hydrophilic properties   Heat sealable and sterilisable   Constructed of appropriate material (material must be approved by the Canadian Food Inspection Agency (CFIA))   Resistant to penetration by fats, oils and other food components   Physical strength to resist physical abuse during packing, retorting, storage and distribution (i.e., tearing, pin-holing, fatigue, impact and abrasion)   Absence of solvent residues. Chemically inert polypropylene films require manufacturing catalysts, which must be removed with solvents before the film can be used for foods.   Bonding materials for the laminates must not migrate into the foods.   High light barrier. A processor may purchase pouches in a number of different forms. The flexible pouches can be a pre-formed three-side sealed pouch or formed as an in-line operation with the filling and sealing combined in a pouch packager. There are several retort pouch filling and sealing systems commercially available. One design is shown in figure 2.3, where the retort pouches are formed from roll stock by folding a single roll along its centerline and heat sealing the sides together. The tubular material is automatically cut to length and the bottom is sealed just prior to the product filling operation. Control of the laminate quality begins with the component material. Close control of each raw material used in the manufacture of the retort pouch must be ensured by establishing the specifications which the final laminated pouch must meet, and by establishing an effective monitoring program. Two important properties which need to be monitored during laminate fabrication are the basis weight of the laminate and the Chapter Page 2 4 Flexible Retort Pouch Defects Status Date Identification and Classification New 31/05/2002 laminate tensile strengt.h 2.2.1 Basis Weight of the Laminate The basis weight of the laminate is determined by the use of a laboratory balance. A sample of the pouch material is cut from the pouch material and weighed. The equivalent weight of the sample in grams is then converted into pounds per ream. Note: 1 ream equals 516 sheets of paper. 2.2.2 Laminate Tensile Strength The laminate tensile strength is measured using an Instron or similar tensile tester. The bond strengths of polyester film to foil, and polypropylene film to film are measured to ensure that the retort pouch material complies with the manufacturer's specifications. Processors generally choose the pre-formed pouches. These have three seals already formed, thus requiring a single heat bar for closing. Pouches are usually transported to the plant in master cartons of 1000 or more units. Processors inspect empty flexible pouches prior to use for: pouch dimensions, pouch shape, correct material, and manufacturer defects (i.e., delamination, abrasions, tear notch anomalies). These observations should be recorded and those pouches not meeting the manufacturer parameters must be culled out as the hermetic integrity of the pouch may be compromised. 2.3 POUCH LAMINATES As shown in figure 2.2, most retort pouches are constructed with a 4-ply laminate consisting of a polyester outside layer, a nylon 2nd layer, an aluminum foil 3rd layer, and a polypropylene inside layer. The aluminum foil can be laminated with either the matte or the shiny side exposed to view. Normally the matte side is to the outside. Some pouch material has polyvinylidene chloride (PVDC or SARAN®), ethylene vinyl alcohol (EVOH) or nylon instead of the aluminum foils in the middle layer. The components of the laminate are held together with adhesive, which are usually modified polyolefilms such as ethylene vinyl acetate (EVA). Chapter Page 2 5 Flexible Retort Pouch Defects Status Date Identification and Classification New 31/05/2002 Each component performs a specific function that is critical to product shelf life stability and container integrity. In some cases a clear layer, to permit viewing of the product, replaces the foil layer. The materials of choice are generally SARAN® (PVDC), EVOH or nylon. While these plastics are good barriers to oxygen molecules, they are not complete barriers, and therefore the shelf life of the container is reduced substantially. Figure 2.2 Pouch Laminations 2.4 TYPES OF POUCHES 2.4.1 Pre-formed Pouches The pre-formed retort pouch, which is the type most commonly used by the food processor, has three sides already sealed by the retort pouch manufacturer.