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Stainless steels have been utilized for many years in the food, dairy, and pharmaceutical industries. Most commonly used in product contact areas, stainless steels are relatively corrosion resistant, readily cleaned, and durable. Contrary to what the name may imply, "stainless" steels are not corrosion proof. They are, however, corrosion resistant if cared for properly.


The corrosion resistance of stainless steels is provided by a thin, invisible, chromium-rich oxide surface film. This film is formed by chromium atoms uniting with oxygen. Given enough chromium content in the stainless steel, this surface film will regenerate on its own, in the presence of air. The stainless steels most commonly used in the above mentioned industries possess the ability to regenerate this film. These are types 304, 316, and the low-carbon versions 304L and 316L. If the surface film is compromised, so is the corrosion resistance.


Important to the corrosion resistance of stainless steels are maintaining a clean, relatively smooth surface, and allowing the natural oxide film to regenerate. The second condition cannot be met without having satisfied the first.


Obviously, the method of cleaning largely depends on the application. Common methods are Cleaning-In-Place (CIP) and Cleaning-Out-of-Place (COP). CIP requires the circulation of caustic, acid, rinse, and sanitizing solutions at a prescribed flow rate. The flow rate depends on the system design and must be high enough to induce turbulent flow. The generally accepted rule is to provide at least 5 feet per second of flow velocity throughout the system. COP requires dismantling of parts, soaking, and brushing. Sometimes, the soaking and brushing can be replaced by the use of a COP tank.


More important than the method of cleaning is following the manufacturers' recommendations for cleaning. The equipment manufacturers can provide the "mechanical" details of the required cleaning. These include required flows or velocities, methods of equipment disassembly, possible trouble spots which require special vigilance, etc. The chemical manufacturers can provide the expertise when it comes to the required cleaning and sanitizing chemicals, solution concentrations, temperatures, times, etc. The chemical side of the issue is very dependent on the nature of the product being processed, length of runs, and local water conditions. A specific program should be implemented only after careful examination of the process and conditions.


Stainless steel should be kept free from cracks, pits, or deep scratches. Soil can collect in these areas, not allowing the oxide film to form, and reducing corrosion resistance. Mechanical abrasion should be avoided where possible, as this too, will break the oxide film. Improperly used cleaning chemicals and sanitizers can destroy the oxide film. A prime example of this is high concentrations or extended contact times of chlorine-based sanitizers.


Once the oxide film is broken and corrosion starts, pitting usually follows. Pitting further accelerates the corrosion activity by further breaking down the oxide film. This process results in a "snowball" effect that once started, accelerates very rapidly. It is important to point out that corrosion doesn't always follow a disruption in the oxide film. So long as the surface is clean, the film will usually regenerate in the presence of air.


Wherever possible, air drying should be allowed following the cleaning process. This may involve opening sanitary connections, as well as disassembling or opening equipment, valves, and pumps. Air drying should be allowed as often as economically feasible. Some smaller plants may be able to do it daily, while larger processors, running around the clock, may only be able to provide the time once every month or two.


The information provided here is meant to be a simple guideline. Actual practices will vary from application to application. If you have further questions regarding this material, please feel free to contact us.




Ask this question of the next ten food service employees you meet and you may find answers varying wildly. But if, one believes that, one of the critical factors in controlling bacteria in food is controlling temperature, then it is essential to use a thermometer. For safety, foods must be held at proper cold temperatures in refrigerators or freezers and they must be cooked thoroughly. It is essential to use a thermometer when cooking to prevent undercooking and, consequently, prevent foodborne illness.


Many food handlers, nonetheless, are hesitant to use a thermometer. Many believe that visible indicators, such as color changes in the food, can be relied on to determine if foods have been cooked to an endpoint that ensures bacterial destruction. Recent research, however, has shown that color and texture indicators are not reliable. For example, ground beef may turn brown before it has reached a temperature at which bacteria are destroyed. A cook preparing hamburger patties and depending on visual signs to determine safety by using the brown color as an indicator is taking a chance that pathogenic microorganisms may survive. A hamburger cooked to 160°F, regardless of color, is safe.


It is simple to say that using a thermometer is the only reliable way to ensure safety. Most cooks know that to be safe, a product must be cooked to an internal temperature high enough to destroy any harmful bacteria that may have been in the food. But, what about the "doneness" of most foods.


When we use the term "doneness," many use the term "doneness" to refer to the sensory aspects of food. Aspects such as, texture, appearance, and juiciness. Unlike the temperatures required for food safety, these sensory aspects are subjective. The temperature which indicates "doneness" varies, as does the temperature at which different pathogenic bacteria are destroyed.


A roast or steak that has never been pierced in any way during slaughter, processing, or preparation and has reached an internal temperature of 145°F is safe to eat. A cook looking for a visual sign of "doneness" might continue cooking it until it was overcooked and dry. A cook using a thermometer can feel reassured the food has reached a safe temperature.


Likewise, poultry should reach at least 160°F throughout for safety, but at this temperature the meat has not reached a traditional "done" texture and color (the red color of poultry does not change to the expected color of white until temperatures are well above 160°F), and many cooks prefer to cook it longer to higher temperatures. Food safety has and continues to be the number one concern in the food industry. For 90 years, our food safety system has been built on the policy that all members of the food industry, not any agency of the government, have the primary responsibility for the safety and integrity of the foods they produce. No one has a more vested interest in food safety than the people who make food products.


The NY Times was cited as reporting that the administration proposed a significant rise in funding for US food safety programs. An unidentified senior White House official was quoted as saying, "What we are trying to do is take the agencies that deal with food inspection from the 19th century to the 21st century. We are carrying out the first update of our food safety programs in 90 years."


So what’s the big deal? The sudden prominence of concern, really reflects the nasty variant of the common (and usually harmless) intestinal bacterium Esherichia coli. Specifically, the new super-bug, E.coli O157:H7.


In the words of the Federal Drug Administration (FDA), E.coli O157:H7 is a dastardly organism that causes "hemmorrhagic colitis, a severe illness, the symptoms of which include high fever, vomiting, and bloody diarrhea, with consequent dehydration. In hospitalized patients with weakened or immature immune systems, the infection can progress to a life-threatening kidney disease with a mortality rate of 6%. The sick-food alarm began ringing after O157:H7 killed three customers of a Jack-in-the-Box restaurant in 1993. In August 1997, the organism caused a 25-million pound recall of hamburger meat from Hudson Foods, Inc., a plant in Nebraska. Although the variant is being found in less food samples each year, FDA says it still causes more than 20,000 infections and 250 deaths each year in the United States.


E.coli is not the only problem. The bad food bacteria, which also includes salmonella, campylobacter and shigella, causes between 6.5 and 33 million cases of foodborne illness and about 9,000 deaths annually in the United States.


A comprehensive system of assessing the risks of human illness from microbial pathogens in the food supply has yet to be devised. What is known is that most pathogenic bacteria are destroyed between 140°F and 160°F. For further food safety information, call the USDA’s nationwide toll-free Hotline at 1-800-535-4555. Specialists are available Monday through Friday, from 10 a.m. to 4 p.m. Eastern Time, in addition, general food safety information is available 24 hours a day, 7 days a week.


What does Chester-Jensen have to do with food safety? The answer is really very simple. For close to a century, we’ve understood the need for food safety. In fact, Chester-Jensen has provided innovation and leadership in this field (pasteurization), as well as in the field of safe hot and cold food processing equipment. This experience, coupled with our committment to quality is available to you today.


We welcome your comments!



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