This article explains what modified atmospheric packaging (MAP) means to the poultry industry and how it meets the quality demands of modern consumers for fresh foods.
MAP is also known as gas flushing or protective atmosphere packaging. It is used to extend shelf life and maintain visual, textural and nutritional appeal of fresh foods. It involves developing a protective gas mixture of high purity oxygen (O2), carbon dioxide (CO2) or nitrogen (N2), and enclosing fresh food with the gas inside the packaging. This is designed to minimise the inward and outward diffusion of MAP gases, water vapour and atmospheric air. Each gas blend is carefully developed to meet the specific respiration needs of each packaged food product. A key advantage of MAP packaging is to enable fresh food to be delivered to consumers without having to add chemical preservatives or stabilisers. The modern consumer expects consistency, freshness, flavourful products and in-stock availability from its food brands. Processors and marketers depend on MAP packaging to meet these expectations.
As with other flesh foods, the spoilage of chilled poultry stored in anaerobic (oxygen free) conditions is largely due to the growth of bacteria called pseudomonads (P.) such as P.fluorescens, P.putida and P.fragi. While human infections from these are rare, occurring only in patients with compromised immune systems, when these organisms reach populations of 100-million CFUs (colony forming units) per square centimetre, an unpleasant off odour can be detected.
Another key factor underpinning the success of MAP packaging is temperature. Studies have shown that portions of fresh chicken stored at an atmosphere of 25 per cent CO2 and 75 per cent N2 could last for 10 days at below 2.0 °C in trays with non-permeable film without developing off odours or discolouration associated with pseudomonad-type bacteria. But at 3.3 °C in the same atmosphere over the same period, spore-forming bacteria called clostridium botulinum were found to grow, which are the dangerous toxins that cause botulism.
The studies show that higher CO2 concentrations give better protection, but the higher concentration also causes the tray packaging to deform, because the CO2 reacts with moisture to form a vacuum in the tray. Pure CO2, however, is widely used for shipping unpackaged bulk and par-cooked chicken, where a central kitchen distributes to stores for the final cooking steps to be done.
To deliver fresh poultry from producer to supermarket fridges, the low temperatures must be continuously maintained via a very well monitored and unbroken cold supply chain. This has now focused the whole of the fresh food industry on quality and safety, from farm to supermarket.
Afrox has developed an extensive range of quality gases and gas mixtures that cover all current MAP processes. Called FoodFresh, these gases fulfil the requirements of quality assurance, hygiene and freshness demanded by the food industry.
Gases are supplied in dedicated high-capacity, high-pressure steel cylinders, each with a certificate of compliance guaranteeing the quality. The overall quality of FoodFresh gases and gas mixtures is achieved by carefully controlling both the preparation and filling procedures for each cylinder of a FoodFresh mixture.
In addition to MAP solutions, Afrox and its parent company, The Linde Group, have been providing innovative solutions to the poultry industry internationally for decades. Afrox’s expertise and solutions extend through to every phase of poultry processing and the cold food chain, chilling, individual quick freezing (IQF), water purification, and MAP packaging and solutions for keeping food continuously cold during transportation.
Hans Strydom is the Afrox technical services manager for special products and chemicals