The Role Of Packaging

Published Date: 02 Nov 2017

2.1.1 The Role of Packaging

Food packaging is a necessity for every kind of food. Without food packaging the safety and quality of food would be compromised and pervasive as almost all the food is packaged in some way. [a.b]. An ideal food packaging must be able to perform a number of different tasks: protecting the contents from contamination and spoilage, making transportation and storages of the product easy, providing a uniform measurement of contents, promoting the product and inform the consumer, and finally convenience, as consumers usually prefers a convenient packaging [a,c].

According to books by Gordon L. Robertson, he mentioned that an appropriate design packaging is essential to allow a package to protects what it sells as well as to sell what it protects [a,b,c]. Hence there are four primary function of packaging which must be interconnected, assessed and considered simultaneously in the packaging development process [c]

Containment

The ability of a packaging to contain the product is very obvious and tends to be overlooked by many. All products must be able to be contained in the packaging before any transportation. Without the containment function, contamination and the loss of product would be rather extensive. Hence, the containment function provides a huge contribution into protecting the environment from the uncountable products which are moved from different locations in all sorts of events. A faulty design packaging could lead to a major pollution to the environment.

Protection

The primary function of a package is to protect the packaging`s content from the outside environmental effects such as gases, water, moisture, vapor, odors, micro-organisms, shocks, dust, vibrations and compressive forces. It is also to protect the environment from the product. For most of the food, the protection provided by the packaging is an essential part in the preservation process. For example, aseptically packaged milk and fruit juices in paperboard cartons can only remain aseptic for a period of time as long as the package provides protection. A vacuum-packaged meat will not achieve its desired shelf life as well if the package allows oxygen to enter. In general, once the integrity of the package is breached the product can no longer be preserved. Packaging protects or conserves much of the energy expanded during the production and processing phase of the product. For example, the energy required to produce the product would take its form in terms of the energy required to convert the raw materials to the product; transportation takes its form of energy as transport fuel. Although the production of the packaging film requires a little more energy to produce the package, the spoilage of the product itself without the packaging has a larger consequence as compared to the usage of the packaging with a smaller increase in the total energy production. [c]

Convenience

Packaging plays an important part in allowing products to be used conveniently, in this modern, industrialized society, lifestyles are undergoing tremendous changes. However, food/ food packaging is still a necessity in our daily lives. These changes have caused a demand for greater convenience in household products such as food that can be prepared beforehand and can be cooked or reheated in a very short time, and if possible, without removing them from the package; re-closeable openings on the drink bottles to allow consumption on the go and many more. In addition, apportionment function of packaging should also be considered in the design of the food packaging where in this context, the package function to reduce the output to a manageable desirable "consumer’ size from industrial production. Another factor would be the relation of the primary package to the convenience of use by the consumers to allow easy holding, opening and pouring as appropriate as possible. Hence all these have cause the packaging to respond to those demands and changes.[c]

Communication

As mentioned above, "a package must protect what it sells and sell what it protects" that is defined as the role of the package as a "silent salesman" [a,b]. The distinctive branding and labeling allows the package to communicate its messages to the consumers enabling a self-service basis in the supermarkets to support the modern methods of consumer marketing. For example, consumers can make their purchase of products just by the numerous clues provided by the graphics and the distinctive shapes of the packaging which includes the ingredient and nutritional information, as well as the country of origin. The Universal Product Code (UPC) are also incorporated as a function on the packaging itself for a more accurate and rapid reading using a modern scanning equipment at the retail checkouts. [a,c]

2.1.2 New Technologies in Food Packaging

As mentioned, traditional basic function of packaging aims to protect, communicate, convenient, and contain. These functions are not totally exclusive but an interconnected network within each other. Therefore, after all these years of experimenting and research, human have developed many different types of food packaging that is suited for different storage condition instead of adopting the traditional packaging using passive barriers to delay the negative effects in the environment [f]. Food packaging has been progressing into a new era. Some of these include technologies such as controlled atmosphere storage and modified atmosphere storage, intelligent/smart food packaging and also active packaging. These systems are incorporated into the packaging with the intention to increase the shelf-life of the products.

Modified Atmosphere Packaging

The controlled/modified atmosphere storage is a relatively old process according to ancient writing. Certain forms of modified atmosphere storage were used in China, Greece and other early civilizations. In some of those reports, some of the fruits were sealed in the package together with grass and fresh leaves. Over time, as the grass, fruits and the leaves the atmosphere inside the packaging was modified into an environment high in carbon dioxide and low in oxygen which retard the process of the fruit ripening inside the package. A similar study was done in the 1930s on the effects of carbon dioxide and storage temperature that would affect the inhibition of microbial growing on the meat surfaces. The results show an extension in product shelf life. Hence, in the late 1950s the first significant trails of retail size modified atmosphere packaging (MAP) took place with vacuum-packed meat, fish and coffee. In the 1970s and 1980s there are an increase in the number of researchers who are interested in the gas preservation techniques and commercial applications of MAP using nitrogen (N2), oxygen (O2) and carbon dioxide (CO2) have steadily increased since then. The purpose of using MAP is to extend the shelf life of food products and to prevent (at least retard) any undesirable changes in the wholesomeness, safety, sensory, characteristics, and nutritive value of foods by the following three principles[d]:

Reduces undesirable physiological, chemical/biochemical and physical changes in foods

Controls microbial growth

Prevents product contamination like any other packaging techniques

Active Packaging and Intelligent/ Smart Packaging

Active and smart / intelligent packaging is the main areas in which most of those innovative ideas from researches have been applied which satisfy the needs to widen and redefine the functions of food packaging.

Figure 1: Figure 2.1Model of packaging function [e]

In active packaging, the protection function has a shift in the concept from passive to active. The primary basic primary packaging materials only function as an inert barrier for protection of the product against oxygen and moisture; these functions were considered to be `passive’. As the packaging technology developed, new packaging materials have been developed to provide `active’ protection for the product. In which active packaging has been defined as a system that the product, the package and the environment interacts in a positive way to extend the shelf life or to achieve some characteristics that cannot be obtained otherwise. All the active packaging technologies would involve physical, chemical, or biological action for changing interactions between the packaging, the product, and the package headspace for a certain desired outcome. Hence, they can be divided into three categories mainly releasing system, absorber, and other system. [e]

According to figure 2.1, smart packaging was placed above the communication function in where, smart packaging is a provider of enhanced communication while active packaging is a provider of enhanced protection. Therefore, in the whole packaging system, smart packaging is responsible for sensing the environment and processing information to its consumer and manufacturer, it possess the ability to track the product, sense the environment inside or outside the package, and communicate with human. For example, a smart package would be able to monitor the quality/safety condition of a food product and give early warning to the consumer of food manufacture. Active packaging is the component responsible for taking action (e.g release of an anti-microbial) in order to protect the food product. [e] An ideal food packaging would have all the various functions from smart, active and traditional packaging working together for an appropriate situation to provide a total packaging solution.

2.2. Active Packaging Technology

2.2.1 Introduction

As the standards and quality of everyday living increases, people are now demanding for more minimally processed and ready-to-eat `fresh’ food products; this is due to the fact that recently there are more food-borne microbial outbreak in the world [I]. The demands includes the globalization of food trade as well as the distribution from centralized processing in which all of these factors creates a major challenges for the food-packaging industry with respect to the maintenance of the products safety and quality. As the standards of food packaging increases, the function of a traditional packaging system seems to have reached its limit with regards to further shelf life extension of the packaged food. [h] In order to surpass that limit and to improve the quality, safety and integrity of the packaged food; newly innovated active and intelligent packaging concepts have been developed to meet those demands.

As mentioned, traditional food packages are designed to delay the adverse effects of the environment on the food product from its passive barriers. The active packaging concept will allow packages to interact with food and the environment so as to provide an active role in food preservation. [h] According to a European, Actipack project; Active packaging has been defined as the packaging which `changes the condition of the packed food to extend shelf life or to improve safety or sensory properties, while still maintaining the quality of packaged food’.

2.2.2 Types of Active Packaging

Active packaging systems are specially designed to be a diverse, broad concept for specifically certain range of food product shown in the table below (Table 2.1). Active packaging consist of two main categories; (i) active releasers/emitters, i.e packaging that releases beneficial active compounds into the food/surrounding. This category usually consists of anti-microbial, anti-oxidative active packaging which includes aroma and carbon dioxide releasers. (ii) Active scavengers/absorbers, i.e packaging that absorb unfavourable components from the package headspace and/or the food itself. This category consists of oxygen, carbon dioxide, ethylene scavengers, and moisture and aroma absorbers. [e, h]

Types of Active Packaging

Food Products

Oxygen scavengers

Smoked and Cured meats, fish, cheese, bakery products, fresh pasta, ground coffee, tea, chips, vegetables, milk powder, cakes, cookies, beer, wine and beverages

Ethylene scavengers

Fresh produce, fresh-cut products

Carbon dioxide scavengers

Ground coffee

Moisture regulators/absorbers

Dry products, meat, poultry, fish

Aroma scavengers/ absorbers

Citrus juices

Antioxidative packaging

Cereals, milk powder

Carbon dioxide releasers

Fish, Meat, butter, poultry

Microwave susceptors

Ready-to-eat meals, French fries, popcorn

Antimicrobial packaging

Meat, poultry, cooked ham, fish, cakes, bakery products, fruits, cheese

Table 1: Table 2.1Potential application of Active Packaging technologies. [h]

2.2.1.1 Oxygen-Scavenging Packaging

In the past, oxygen-sensitive foods and beverages were packaged in various ways to minimize their exposure of oxygen in the environment. The oxygen maybe present in the package at the time of sealing, there could be possibility that it could enter the pack by the permeation or leakage over the storage life. The presence of oxygen will allow reactions in the food package. The impact of oxygen on food quality, and shelf life is not only dependent on the quantity of oxygen available for chemical oxidation or support of growth of organisms but also the rate of the reactions of food which consumes the oxygen.[d]

Oxygen-scavenging are classified as an active scavengers/absorbers packaging where O2 absorbers are used in the packaging. i.e powdered iron or ascorbic acid. Using these powdered irons, it would allow the possibility to reduce O2 concentration in the headspace to less than 0.01%, this is much lower than the typical 0.3-3.0% residual O2 levels which is achievable by vacuum or gas flashing. The reaction using powdered iron scavenger is shown below.

Fe  Fe2+ + 2e

½ O2 + H2O +2e  2OH-

Fe2+ + ¼ O2+ ½ H2O  Fe (OH)3

Fe(OH)2 + ¾ O2 + 1 ½H20 Fe (OH)3

For those well know O2 scavengers, most would take the form of small sachets contacting various iron-based powders, together with various catalysts that scavenge O2 within the food package and irreversibly convert it to a stable oxide. As shown in chemical equation above, water is required for O2 absorbents to function, in some sachet; the water is added during manufacturing, while in others, moisture must be absorbed from the food before O2 can be absorbed. Iron powder is separated from the food by keeping it in small sachets which are not meant to be eaten. They are highly permeable to O2 and sometime water vapor. Usage of iron-based scavengers can be a disadvantage as they normally cannot pass the metal detectors that are often installed on packaging lines. Hence, non-metallic O2 scavengers which includes organic reduction agents i.e ascorbic acid, ascorbate salts or catechol and enzymic O2 scavenger systems using glucose oxidase or ethanol oxidase, which can be added into sachets, adhesive labels or immobilized into package surfaces are substituted with the iron-based scavengers. [c] In addition, in order to prolong the product shelf life and enhance the overall performance of the absorbent, films are contained with PVdC or EVOH copolymer as it gives a good barrier layer. These films have an O2 permeability of [< 0.004 X 10 -1[mL(STP)cm cm-2 s-1 (cm Hg)-1] and the headspace O2 reduced to around 100ppm in 1-2 days and remain at that level for the duration of the storage period, provided packaging integrity is maintained. [c]

2.2.1.2 Carbon Dioxide Generating/ Absorbing System

There are mainly two types of carbon dioxide active packaging. These are sachets available that are based on either ascorbic acid and ferrous carbonate or ascorbic acid with sodium bicarbonate that absorb O2. Due to the reaction give back an equivalent volume of CO2. The emission of CO2 responding to O2 gas absorbed can be described by the following reaction:

4 FeCO3 + 6 H2O + O2 4 Fe (OH)3 + 4 CO2

In absence of this mechanism, the packaging would collapse due to the volume reduction or pressure decrease of the headspace atmospheric gas. In addition, the high CO2 concentration in the package can also contribute to retarding microbial growth. [c,e]

CO2 gas absorbing sachets are rare, whereas absorbent sachets that contain Ca(OH)2 in addition to iron powder are more common, as a result it absorbs CO2 as well as O2. In applications such as packaging for roasted or ground coffee, this is a very useful function as the fresh roasted coffee itself releases considerable amount of CO2 and unless removed, it can cause the packaging to swell or burst due to the pressure built up. [c]

2.2.1.3 Ethanol Generating Systems

Ethanol (ethyl alcohol) has been used as an antimicrobial agent for many years. According to Gordon L. Robertson, previously this method was used to prevent mold spoilage of fruits. In Japan high-moist bakery used this method vastly to extend the shelf life up to 20 times as ethanol exhibits antimicrobial effects even at low concentration. The sachets contain ethanol and water, which are adsorbed onto SiO2 powder and filled into a paper- EVA copolymer sachet. A main disadvantage of using the ethanol vapors other than cost would be the formation of off-flavour and off-odors in the product. The absorption of ethanol from the headspace by the food can go up to 2% concentration in the food which results in regulatory problems. However, there would not be an issue if the food is required to be heated in an oven before consumption as the ethanol being volatile will evaporate off. Some sachet contains traces of vanilla or other flavours which are used to mask the odor of alcohol. [c]

2.2.1.4 Anti-microbial Packaging

According to (Han, 2000) Antimicrobial (AM) packaging is a system that can kill or inhibit the growth of micro-organisms and thus extend the shelf life of perishable products and enhance the safety of packaged products. Most of the AM packaging systems are based on direct contact between packaging material and the surface of the food. The AM agents are incorporated into or coated on the packaging layer. Some of these AM functional groups would be attached to the polymer backbone. This would include bioactive agents such as enzymes and other organic compounds which could be incorporated in the packaging material matrix maintaining their AM activity as themselves. [a,d,e]

Tremendous research and development were carried out over the last decade for film testing with AM properties to improve food safety and shelf life. Among many applications such as oxygen-scavenging packaging and moisture-control packaging, AM packaging would be one of the most promising innovations of active packaging technologies. The creation of new AM packaging systems can be discovered by incorporating various AM and materials into conventional food packaging. Table 2.2 shows potential AM agents anti food grade-grade preservatives. These agents can be classified into three groups; chemical agents, natural agents, and probiotics. [a,d]

Table 2: Table 2.2 Examples of potential Antimicrobial agents for Antimicrobial food packaging system . From ref [d]

Classification

Antimicrobial agents

Organic acids

Acetic acid, benzoic acid, latic acid, citric acid, malic acid, mixtures of organic acids

Acid salts

Potassium sorbate, sodium benzoate

Acid anhydrides

Sorbic Anhydride, benzoic anhydride

Para benzoic acids

Propyl paraben, methyl paraben, ethyl paraben

Alcohol

Ethanol

Bacteriocins

Nisin, pediocin subtilin, lacticin

Fatty acids

Lauric acid, palmitoleic acid

Fatty acid esters

Glycerol mono-laurate

Chleating agents

EDTA, citrate, lactoferrin

Enzymes

Lysozyme, glucose oxidase, lactoperoxidase

Metals

Silver, copper, Zirconium

Antioxidants

BHA, BHT,TBHQ, iron salts

Antibiotic

Natamycin

Fungicides

Benomyl, Imazalil, sulfur dioxide

Sanitizing gas

Ozone, chlorine dioxide, carbon monoxide, carbon dioxide

Sanitizers

Cetyl pyridinium chloride, acidified NaCL, triclosan

Polysaccharide

Chitosan

Phenolics

Catechin, Cresol, Hydroquinone

Plant Volatiles

Linalool, eugenol, thymol, allyl isothiocyanate, cinnamaldehyde

Plant/Spice extracts

Grape seed extract, rosemary oil, basil oil,beta acid

Probiotics

Lactic acid bacteria

2.2.1.4.1 Chemical Anti-microbial Agent

In food preservation, the entire packaging ingredient should be food-grade additives as the chemical agents are mixed with food ingredients and incorporated into packaging additives /inserted into the headspace atmosphere where AM agents are in contact with and consumed with the food products. Due to such applications, the chemical AM agents should be controlled as a food ingredient regardless of the initial position of the chemical AM agents (in the food product, in the packaging material, or in the package headspace atmosphere).

In the case of the non-food-grade chemicals, one way to introduce the chemicals into the food packaging system is through a chemical binding of the AM agents to packaging material polymers (Immobilization), the simplest form of fabricating AM plastic packaging is by extruding the polymer master batch together with the active substances which in this case the AM agents. [d,e] One application is the silver substituted zeolites called Zeomic®; to date, it is the only Food and Drug Administration (FDA) approved materials for direct food contact. Zeomic® is widely used for food applications especially in japan as a polymer additive. The sodium ions present in zeolites are substituted by silver ions, which have a high antimicrobial activity against a large range of bacteria and molds with a very low human toxicity; the substituted zeolites are incorporated into polymers such as low desnity polyethylene (LDPE), polypropylene, etcetera. The microbial cell present in the food product will then take the Silver ions up which would disrupt the cells` enzymatic activity. [c,I]

The other common types of chemical AMs used by researchers are the types of organic acids which are due to their efficiency and cost effectiveness. Previously, many organic acids which include fatty acids are naturally existing chemicals. Now, most of them are produced by chemical synthesis or chemically modified from the natural acids. I.e Sorbic acid, Sorbates, Fungicides.

2.2.1.4.2 Bioactive Anti-microbial Agent

Bioactive Anti-microbial (AM) agents/ Natural AM agents are a naturally occurring AM agent which includes herb extracts, spices, enzymes and bacteriocins. Food manufacture are now using more of these naturally occurring AMs to sterilize and/ or to extend the shelf life of food as the consumers are demanding usage of chemical preservatives-free food. The extracts from these herbs and spices contains multiple natural compounds and are known to have a wide AM spectrum against a wide range of micro-organisms. [d]. Examples of natural extracts are Linalool from Sweet Basil herb , Amexol from Rosemary (Rosemarinus officinalis L.), grapefruit seed extract and many more (Table 2.2).

One of the popluar natural AM agents is sweet basil herb as mentioned above, this etcetera agent has been used widely in food products and as an ingredient in dental products. The immobilization of basil extract into LDPE films are effective AM activity against various microorganism such as staphylococcus aureus, Listeria annocua, Escherichia coli and saccharomyces cerevisiae. In general, natural antimicrobial agents can be coated on the packaging itself or even blending with polymer with the natural substance by extrusion technique to create an antimicrobial film [k]