Guest Columns

Cheese Technology

Proactive suggestions to reduce recalls in the U.S. cheese industry

Dr. Mali Reddy

Dr. Mali Reddy serves as president of the American Dairy and Food Consulting Laboratories and International Media and Cultures (IMAC Inc.), Denver, Colorado. He holds several degrees including M.S. and Ph.D. degrees from Iowa State University in food technology and microbiology. He is a guest columnist for this week’s issue of Cheese Market News®.

After a product is suspected or confirmed to be mislabeled or to present a health hazard to consumers, recalls ensue. According to FDA records, in the month of June 2016, in one week period alone (June 2-June 8), there were 20 recalls — a number I find scary.

The recent massive recalls of frozen foods produced by CRF Frozen Foods in Pasco, Washington, due to Listeria contamination led to the company closing its processing facility. In another recent instance, 10 million pounds of dry flour product produced by General Mills has been recalled due to the pathogenic bacteria, E. coli O121. Another massive Salmonella outbreak was linked to poultry, according to CDC.

Because of these massive outbreaks and recalls due to Listeria, E. coli and Salmonella, FDA is undertaking an extensive mission to investigate and check various food production facilities and foods in order to protect the public. FDA and CDC have developed a system to track the genetic makeup of Listeria, E. coli and Salmonella. Once a food related outbreak is identified, they can match the DNA from contaminated food with the pathogenic bacteria making people sick and potentially trace it to the originating food processing plant.

What do we have to do to eliminate such problems due to pathogens and subsequent recalls in the dairy food and cheese industry? To answer this question, the following areas have to be reviewed and corrected: raw milk; pasteurized milk in the cheese vat during ripening; anticaking agents used in the finished shredded cheese; and manufacturing practices, plant sanitation and employee education. Let us analyze briefly why these areas are of much concern.

• Raw milk

We all know that raw milk coming from farms has some form of pathogenic bacteria. Consequently, if such a contaminated raw milk is brought into the dairy food processing plant, it will further contaminate the milk silos and the plant environment (outside the manufacturing area).

A precaution prior to pasteurization is proper refrigeration of the raw milk. However, refrigeration does not reduce the already present pathogens in the raw milk, and at times some psychrotrophic pathogenic bacteria can grow and multiply in refrigerated raw milk.

Having said that, how can we protect the raw milk received at the cheese plant? The best way to retard such pathogenic bacteria (as well as spoilage type bacteria) is through activation of the lacto peroxidase (LP) system by inoculating the raw milk in silos using a milk silo culture. The end product of the activated LP system can retard the wide spectrum of pathogenic bacteria. The activated LP system coupled with subsequent pasteurization will help to kill or inactivate the pathogenic bacteria.

• Pasteurized milk during ripening

The pasteurization temperature of 161 F for 15 seconds should inactivate (kill) the pathogenic bacteria present in raw milk. However, according to the literature, some of the pathogenic bacteria, especially some strains of Listeria monocytogenes, can survive pasteurization if they are embedded in the white blood cells or if their initial concentration is significantly high. Such a thermally injured (but not killed) pathogenic bacteria can revive in the cheese vat during ripening period, since the ripening temperature and the highly nutritive milk (pH 6.5 + 0.1) are ideal for their revival.

How can we solve this inherent problem? The best answer is adding 1 to 2 percent of properly prepared nutritionally balanced bulk liquid starter (with natural starter culture produced bacteriocins) as soon as pasteurized milk starts to go into cheese vat. In my opinion, the use of direct set cultures cannot stop the revival or rejuvenation of the subdued pathogenic bacteria.

• Anticaking agent used in the finished shredded cheese

Cheese usually is produced under meticulous conditions to eliminate any possible pathogen contamination. However, not much attention has been paid when it comes to the usage and the kind of anticaking agent used in the shredded or diced cheese.

An anticaking agent should be produced with the least human exposure and also should be high heat treated at a low pH (spray dried) to eliminate even subdued pathogenic bacteria. Subdued or injured pathogens may not be detected in regular routine bacteriological testing of the anticaking agent. However, such an injured pathogen can revive to normality after being added to the highly nutritious cheese product. In my opinion, the anticaking agent products must be produced by spray drying at low pH and bagged without much human involvement. Since an anticaking agent is ending up in the finished cheese, it must be manufactured under strict sanitary conditions just the way cheese is produced. The anticaking agent used also must be allergen free or hypoallergenized and should not have any stigma in the eyes of the consumer.

• Manufacturing practices, plant sanitation and employee education

Since our main concentration is pathogenic bacteria, any of the manufacturing areas where pathogens can revive or survive or multiply should be discouraged.

For example, not sanitizing cheese vats and equipment properly between the vat fills, not sanitizing or using protective cultures to prevent contamination or survival or proliferation of pathogens in the brine tanks etc., certainly encourages growth and prevalence of pathogens. Floor drains must be routinely sanitized, and dilute cooper sulfate can be used periodically on floors and floor drains to eliminate the survival of pathogens, especially Listeria.

Rather than spending too much energy and resources on checking and rechecking for pathogens in the plant environment, take extra preventive measures on a daily basis to eliminate such problems (total quality management). Since our tolerance level for pathogens (especially Listeria) in cheese is zero, plant personnel should take extra preventive and proactive measures rather than emergency reactive measures.

As always, I emphasize and recommend that all plant personnel must be educated and given in-house training programs to teach them practical techniques to curtail pathogen problems in the dairy plant environment and in the products. A simplified basic bacteriology training class for plant employees is an excellent way to begin the fight on the pathogens and recalls. This is a concerted group effort which involves all the plant personnel.

I cannot stress enough the importance of the aforementioned practices to eliminate these economically devastating recalls to protect the dairy industry. They can be accomplished through few minor technological improvements and employee education.


The views expressed by CMN’s guest columnists are their own opinions and do not necessarily reflect those of Cheese Market News®.

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