Food Packaging Technology 3(2+1)

Lesson- 28 Protective functions of food packaging

28.1. Introduction

All packaging aims at preventing contamination of foods by providing a barrier to soils, microorganisms, insects and/or rodents. Depending on the food product, packaging is also designed to control other environmental interactions, including oxygen uptake, moisture loss or gain, aroma loss or gain, food component absorption by the packaging material (scalping), package-component migration into the food, and light transmission.

Packaging works with the preservation approach by preventing microbial contamination, inhibiting microbial growth, and minimizing quality loss. However, after packaging it is possible that foods can deteriorate from one or a combination of biological, chemical, and physical reasons. Destruction and inhibition of microorganisms are the main concerns of food preservation approaches, related to preventing food spoilage and food-borne illness, along with providing the highest food quality (appearance, aroma, taste, texture, etc.) possible.

28.2 Packaged food interaction with surrounding environment

28.2.1 Environment gasses (Oxygen, nitrogen and carbon did oxide)

Exposure to oxygen can cause deterioration of many foods due to oxidation of lipids and other oxygen-sensitive components such as aromas, colors, and vitamins. These foods benefit from packaging that can maintain a vacuum or nitrogen atmosphere and provides a barrier to oxygen.

Foods such as fresh meat, poultry, bakery and pasta products, and chilled prepared foods benefit from packaging that can maintain either a vacuum or a targeted low concentration of oxygen and high concentration of carbon dioxide to prevent oxidation and control microbial growth. High concentration of oxygen combined with high concentration of carbon dioxide maintains color of fresh red meat. Fresh

Table28.1: Interactions possible among food, package and the environment

S.N.	Food	Packaging	Environment	Direction
1.	Color, flavor, nutrient degradation	Light transmission	Light	Environment to Food
2.	Color, flavor, etc. oxidation; respiration	Oxygen permeation	Oxygen	Environment to Food
3.	Carbonation loss; respiration	Carbon dioxide permeation	Carbon dioxide	Food to Environment
4.	Stickiness; texture loss; microbial growth	Water vapor permeation	Water vapor	Environment to Food
5.	Dehydration; texture increase	Water vapor permeation	Water vapor	Food to Environment
6.	Aroma and/or flavor change	Aroma permeation	Aroma	Environment to Food
7.	Aroma and/or flavor change; toxicity	Package component migration		Packaging to Food
8.	Aroma and/or flavor loss	Absorption (scalping)		Food to Packaging

 

fruits and vegetables are respiring and thus need packaging that allows permeation of oxygen in and carbon dioxide out at appropriate rates. Proper design of fruit and vegetable packaging takes into account the different respiration rates of different fruits and vegetables and controls package-head-space oxygen and carbon dioxide concentrations to targeted levels that reduce product respiration rate and increase shelf life.

 28.2.2 Water Vapor

Food stability and food properties, it is appropriate to use water activity, aw, as a measure of the degree of water association with the food’s nonaqueous constituents plays a very important role. Food which is in equilibrium with its environment.

 

                                            a_w = ERH/100

Where:

ERH- Equilibrium relative humidity

The water activity affects food stability in a number of different ways. A typical relationship between water activity and moisture content (moisture isotherm) and the relative rates for a number of chemical reactions, enzyme activities, and microorganism growths that lead to food deterioration.

 Table 28.2: Approximate Amounts of Oxygen and Moisture with which Foods Can Interact before Unacceptable Change

S.N.	Food or beverage	Maximum O2                        gain(ppm)	Maximum water gain or loss
1.	Canned milk, vegetables, flesh foods, baby foods, soups, and sauces	1–5	3% loss
2.	Beers and wines	1–5	3% loss
3.	Instant coffee	1–5	2% gain
4.	Canned fruits	5–15	3% loss
5.	Dried foods	5–15	1% gain
6.	Dry nuts and snacks	5–15	5% gain
7.	Fruit juices, drinks and carbonated  soft drinks	10–40	3% loss
8.	Oils, shortenings, and salad dressings	50–200	10% gain
9.	Jams, jellies, syrups, pickles, olives, and vinegars	50–200	3% loss
10.	Liquors	50–200	3% loss
11.	Condiments	50–200	1% gain
12.	Peanut butter	50–200	10% gain

 

28.2.3 Aroma

Undesirable interactions of food with the environment include the possibility of loss or gain of aromas. Loss of food aromas to the environment reduces the fresh character of food. Gain of aromas from the environment can include engine fuel and exhaust vapors, as well as the aromas of other products such as cosmetics and cleaning agents. Thus, packaging that retains food aromas and excludes foreign aromas is important for maintaining food quality.

 28.3 Packaged food interaction with light

Solid foods are least sensitive to light, because the penetration of light into the food decreases exponentially. However, the situation is different for liquid foods. Diffusion in the liquid exchanges light-sensitive food components between the surface and interior, so that light-degraded compounds are replaced with non-degraded compounds at the surface that are subsequently degraded. The light-degraded compounds can also interact with compounds in the interior to cause further degradation. The quality of food depending on food composition, light can catalyze a number of reactions that lead to chemical deterioration. Light in the high ultraviolet (2900–4000 Å) and low visible (4000–4500 Å) wavelengths catalyzes lipid, color, flavor, and vitamin degradation.

 28.4 Packaged food interaction with Physical stresses

Food physical deterioration can result from bruising, deformation, breakage, or abrasion due to subjection of food to compression, shock, or vibration. Bruising of fresh fruits, vegetables, meat, poultry, and seafood can lead to chemical and biological deterioration. Deformed, fragmented, or abraded food is viewed as inferior by consumers. Rigid and semi-rigid packages protect food from compression damage to the extent they maintain their integrity under compression. Flexible packaging provides little or no protection against compression damage. Thus, primary flexible packages of food are often placed in semi-rigid or rigid secondary packages. All packages, including flexible packages, limit shock and vibration damage to the extent they restrict movement of the food. Beyond protecting food from physical deterioration, the packaging must maintain its integrity to provide its other functions. Failure of the packaging material will result in food contamination from soils and microorganisms, as well as increased interactions with the atmosphere.

 28.5 Packaged food interaction with packaging materials

In scalping (sorption), a component of a food product is absorbed by the packaging material without transfer to the surrounding atmosphere. To varying degrees, all materials used for food packaging have been found to interact with food in one or both ways. Possible migrating substances include plastic monomers and plasticizers, paper coating and adhesive components, metals and metal coatings and glass component ions. The greatest concern is with migration of low molecular weight substances from polymeric plastic materials in contact with food. The existence of these substances in packaging does not necessarily produce migration. The greatest concern with scalping is also with polymeric plastic materials, with resulting loss in food quality. The migration and scalping phenomena are very important to food safety and quality.