Processed lunch meat has a shelf life of up to 120 days. Think of cutting a slice of ham or turkey and putting it in your refrigerator. Would you pull it out 4 months later for a tasty sandwich?
The conventional conclusion might be that processed meats are so laden with chemicals that the extension is due to this. But what causes the extension is not additives but a process called HPP (High Pressure Processing) which is applied to the meat after it is packaged. High Pressure Processing involves the processing of products in a water chamber at pressures up to 87,000 lbs per square inch. (Do not attempt this at home!). The pressure ruptures the membranes of bacteria and destroys them-this would include the bacteria that spoil the food and, more importantly, pathogens such as listeria and salmonella. What distinguishes this process from conventional heat treatment is that HPP is a "cold" process with no heat applied; this prevents deterioration of both the nutritional quality of the food and its freshness (flavor.) The process is being used for not only meats but for "fresh" juices and for packaged guacamole.
HPP is a response to a number of food poisoning outbreaks in the meat, juice and other industries. One of the most notable was with Ball Park Franks and Listeria monocytogenes in 1999, an outbreak that resulted in at least 50 illnesses in 11 states and 6 deaths. It also revealed the vulnerabilities of the food industry to emerging pathogens (disease causing micro-organism). Traditionally, processed deli meats, hot dogs, etc are cooked prior to packaging-the ham or turkey or hot dog is cooked whole in a large chamber to USDA (United States Department of Agriculture, who regulates meat) standards. Subsequent to cooking, the products are cooled, sliced and packaged. The problem with this system is that while the heat treatment can kill the pathogens, there are possibilities for re-contamination of the product from humans, equipment or the environment from cooking to packaging. Listeria is a pathogen which is very widely distributed, thrives in cold temperatures (meat plants) and can find a welcome home in the damp confines of drains, meat coolers. refrigeration units, equipment and floors. Incomplete cleaning can only multiply its numbers and since the meat products are largely exposed between processing and packaging they can contaminate the product and reach consumers.
HPP eliminates this risk since it is a final process after packaging so there are two safeguards for eliminating pathogens, the current heat treatment before slicing, etc. and a large eraser at the end of the line.
Juices also have been implicated in a number of food pathogen outbreaks driven in part by consumer preferences for fresh, non pasteurized juices. Such products though provide no intervention to destroy any pathogens brought in with the product and-let's face it-fruit and vegetables are grown outdoors. HPP provides the same advantages of a "kill step"process and because there is no heat, the flavor profile of a "fresh juice."
Guacamole is an interesting application. If you've made guacamole, you are immediately faced with how perishable it is, as it starts oxidizing and turning brown as soon as cut. This is due to chemical activity-a reaction dependent on the cut flesh, a natural enzyme in avocados and oxygen. In the home we can delay this by wrapping the avocado tightly in cling wrap (reduce oxygen) or rub lemons on the surface (the acidity slows down the chemical reaction). Although these measures help, producing an extended shelf life packaged and palatable guacamole then becomes almost impossible without killing the patient. So for food service operations, if you want to serve guacamole, this means buying ripe avocados and preparing them immediately with much labor and waste. The introduction of HPP though allows the inactivation of the enzymes with no heat and minimal effect on flavor, color or texture. It also permits a new food category, processed and packaged guacamole in pouches or plastic tubs with a long shelf life. Since the vast amount of avocados are produced in Mexico it also allows the processing to take place at the avocado processor not the back room of the restaurant. The result is the consumer is served "fresh guacamole" which is not made in the restaurant.
You may wonder why these products aren't labeled with some new sobriquet-"ultra cool fresh processing" and it's because they don't have to be as processes aren't always required to be labeled like ingredients
For the curious, a video describing the process follows.
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