samedi 23 août 2008

Protecting Your Meat From oxygen

John Solomon is business development leader, specialty foods and consumer goods for Multisorb Technologies. He has 12 years experience in the packaging industry for food service and retail applications.

How does oxygen degradation affect meat?
JS: Oxygen exposure degrades and spoils food in four main ways: colour oxidation, flavour oxidation, lipid or fat oxidation and microbiological spoilage. Colour change is the main reason to regulate the oxygen content of meat packaging—usually a loss of redness in products such as ham or turkey. Consumers see this as signs of aging, possible mishandling or potential spoilage.

Various microorganisms can also produce colour changes in food. Pseudomonas turn it yellow, green, or red. Bacilli blacken food. Yeasts typically form white colonies on meat, or create red to pink discoloration in sea food. Fungi can exhibit a wide range of watersoluble colors. Temperature and packaging integrity play a role in the rate at which food degrades. But most of the pathogens—or organisms that cause disease—that spoil meat need oxygen to survive. (Processed meats are formulated to combat the growth of anaerobic pathogens that can live without oxygen.) Microbiological spoilage can go undetected in packaging, and in extreme cases pathogens can multiply to levels that cause food poisoning.

Ham packed with oxygen sorbents had lower counts of yeast, mould and psychrotrophic bacteria than meat without. The product looked better, as it turned grey more slowly.

A slimy texture can form on meat as bacteria grow, giving an unattractive iridescent ‘shine’. Putrefaction occurs as bacteria break down the proteins, creating foul odours that taint flavours. Pseudomonas, bacilli, and fungi hydrolyse proteins, giving food a bitter and offensive taste, and loss of nutrition. The biochemical oxidation of fatty acids can affect both colour and flavour. Food will also become rancid through the hydrolysis of triglycerides. Each of these degradation processes can be slowed by oxygen sorbents inside processed-meat packaging.

What methods are available to combat and control oxygen degradation and food spoilage?

JS: Modified-atmosphere packaging (MAP) techniques replace the air in the container by flushing it with nitrogen (N2) or carbon dioxide (CO2). The tray is then sealed with a plastic film. MAP will always leave some oxygen behind, and more oxygen will seep through the plastic film. Sorbents can eliminate both the residual oxygen and the additional gas that seeps in over the expected shelf life of the product.

How can the removal of oxygen in packaging enhance brand appeal?

JS: With the oxygen removed, the natural colour of meat can be preserved for several weeks. The redness of cured meat is faint. It’s easily oxidised by a free-radical reaction that’s started by light. So it’s important to remove oxygen before the product is exposed to daylight or display lighting. That way, it will keep an appealing and healthy appearance. If not, the colour will fade within a few hours of packaging. The product will turn completely brown or grey within a few days. There are other less-obvious benefits to removing oxygen: natural aromas and flavours are retained; rancidity is minimised.

How can sorbents increase shelf life?

JS: Removing oxygen also slows spoilage by aerobic microorganisms, including yeasts, bacteria and moulds. For example, users of Multisorb’s Outgredients oxygen sorbents say shelf lives sometimes double.
The objective is to pull the oxygen level down to 100ppm within a few hours, and to zero within 24 hours. This avoids rapid discolouration in meats. Storage life is extended. Pseudomona bacteria that spoil food can’t grow as there’s not enough oxygen.

How can oxygen sorbents enhance MAP?

JS: Oxygen sorbents are not alternatives to MAP. In fact, the two processes complement each other to produce even better results. MAP lines using Multisorb’s Outgredients have been found to operate faster and better.
For example, Cornell University tested packaged ham with and without oxygen sorbents over 79 days. (The meat was N 2:CO2 (70:30) back-flushed, vacuum, and atmospheric pressure packed.) Ham packed with oxygen sorbents had lower counts of yeast, mould and psychrotrophic bacteria than meat without. The product looked better, as it turned grey more slowly. In the middle and late stages of the experiment, you could easily see that the ham was redder.

Are Outgredients necessary for products packaged in plastic?

JS: All plastics are permeable to gas. Oxygen transmission rates of lidding films used in vacuum packaging are low. Typically they’re around 40cc/m /24h/atm at 25°C at 100 percent rh. But rates of 5 to 50cc/m 2/24h/atm have been recorded. Over time enough oxygen will seep into a plastic pack to discolour meat. Of course, you could use aluminium-foil laminate as the metal layer is impervious to gas. But many consumers like to see meat before they buy it. The metal may block the oxygen, but it also hides the meat. So clear film is still necessary, and oxygen ingress is unavoidable.

How are oxygen sorbents placed inside packaging?

JS: Asian consumers look for the sorbent inside packaging and will not buy food where a sorbent cannot be easily seen. For these applications Outgredient sachets can be dropped into the package. But North American and European consumers aren’t used to loose components inside packaging so there are alternatives. Self-adhesive oxygen sorbents can be discreetly applied to the underside of lidding stocks, and hidden under outside branding labels. Consumers don’t usually see them.

Are they safe?

JS: Sorbents are made with food-safe ingredients. They’re resinbonded and don’t leak or spill if sliced open with a knife.

Source: Asia Food Journal

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