The project has three subsidiary objectives:
1. To understand the mechanism behind the barrier properties of packaging and how these are affected by external and intrinsic factors.
2. To study how oxygen, carbon dioxide and light penetrate traditional and new packaging materials, as well as the effect of these factors on food products.
3. To find packaging materials with optimum light and gas barriers to ensure optimum food quality and shelf life.
Light is undesirable for many food products
It is known that light, often in combination with oxygen, can deteriorate the quality of food products. In this project we have particularly studied the effect of light and/or oxygen on the quality of cooked and sliced meat products and various dairy products. Cooked and sliced meat products become grey in the presence of sufficient quantities of oxygen combined with light. For transparent packages, the problem with discolouration can be minimised by controlling all the factors that affect the amount of oxygen in the packages.
With dairy products it is usually the effect of light and not the presence of oxygen that limits the sensory quality. Experiments performed with low-fat sour cream and cream cheese showed that packaging with a sufficient light barrier protected the products against light-induced flavour changes. Trials with butter showed that light waves in the visible spectra have different effects on the different light sensitive components of the butter. This is important information when developing product-specific light protective packaging materials.
Active packaging and correct gas mixture for optimum quality and shelf life
Packaging in modified gas atmosphere is currently used for a range of food products to maintain quality and extend shelf life. Sufficient gas barriers in the packaging and choice of gas mixtures tailored to the product are important issues in this connection. Two of the areas studied in the project have been the effect of CO2 emitters (active packaging) and critical factors for retaining a purple colour in ground meat in a gas mixture of CO2/N2. Using fresh meat raw materials with a high O2 consumption rate favours a rapid conversion to a purple colour while minimizing levels of residual O2 in headspace.
Easily perishable food products are packaged in atmospheres containing CO2 gas, which has an antimicrobial effect. A certain volume of the gas has to be available to inhibit microbial growth, giving relatively large volumes of the packages and high transport expenses. By using a CO2emitter, the volume of the packages can be reduced. Extensive trials with salmon fillets, packed either in small consumer packages or in larger packages for semi-finished products, showed that a CO2 emitter developed by Nofima Mat worked well and can give a shelf life similar to packages with a threefold as large gas volume, giving the possibility of halving the transport costs.
Packaging respiring vegetables is complex
Fruit and vegetables respire (use O2 and emit CO2) in varying degrees depending on product type, variety, growing conditions and storage conditions. To be able to choose the optimum packaging for fruit and vegetables, it is important to have sufficient knowledge about the product's respiration under different storage conditions. At Nofima Mat we have developed a respirometer that can measure respiration for different products.
