by George Looby, DVM
On June 6 the University of Connecticut (UConn) was the site of an all-day workshop on food safety in the cheesemaking industry. This intensive overview of the subject was conducted by Dr. Dennis D’Amico of the Department of Animal Science in the College of Agriculture and Natural Resources. Dr. D’Amico is an assistant professor of dairy foods. His primary activities focus on improving the safety and quality of milk and value-added dairy products. Before coming to UConn, he was a founding member of the Vermont Institute for Artisan Cheese.
In the last three decades, the number of artisan cheese operations in the U.S. has grown from very few in 1980 to more than 900 today. Most of these operations are small, relying on limited resources to achieve their goal of supplying a growing niche market. Often these makers are using outdated equipment and facilities, making them candidates for breeches in good current practices relating to the manner in which their equipment is sanitized and maintained. In keeping with the demands of a certain segment of their customer base, they will often purchase raw milk — a practice which opens many undesirable doors. These artisans often rely on the 60-day aging standard which cannot ensure that the product offered for sale is acceptable.
Cheesemaking is not without its hazards. One of which is radiological. Physical objects can find their way into product. False fingernails from workers on the line is near the top of the list, as are wood splinters, packaging material, buttons — you name it. Perhaps more common are invisible chemical agents such as antibiotics, cleaners, sanitizers and cosmetic lotions. However, the clear “winners” over many years are milk-borne pathogens.
Listeria monocytogenes is everywhere in nature, and especially on dairy farms where it can be found in silage, feces and water and where some animals may be inapparent carriers. It is estimated that it can be found in 2-4 percent of the raw milk in bulk tanks throughout the world. That is a lot of milk poising as a potential source of infection. Listeria monocytogenes is also very tolerant of low temperatures enabling to grow during refrigeration. For individuals with weak immune systems, mortality rate may run as high as 30 percent.
E. coli is another bug whose name frequently appears in the headlines. In the field of food safety, E.coli is used as a marker for the presence of fecal contamination, so its presence in any food processing facility should set off all sorts of alarms. One serotype that is notable is O157:H7 which is found in ruminants who can serve as reservoirs without exhibiting any outward signs. In humans even a few (1000) organisms can set off a wide range of symptoms depending on the status of the individual’s immune system.
Salmonella are commonly incriminated in cases of food poisoning, and with over 2,500 serotypes, this is not a unexpected finding. Again, it is found in 2-5 percent of bulk tank samples worldwide. Staph aureus is carried by 30-50 percent of humans in the nose, on the skin and on the hair. It is a very common cause of contagious mastitis in cattle so is often found in raw milk and is capable of producing a heat stable toxin that can withstand pasteurization temperature. This fact reinforces the need for cooling milk immediately after milking, this step slows down bacterial growth, which in turn slows down the production of toxin.
Food safety begins on the farm and involves the implementation of several simple but often overlooked steps. In a milk handling/cheese making facility, the traffic flow needs to be designed in such a way as to eliminate backtracking. Employee training must emphasize the need to comply with strict one-way traffic flow. Foot baths need to placed at all points of entry (only one or two if properly designed), they must be properly maintained and most importantly used. Air temperature and humidity control must be in place to avoid condensation and fogging. Air flow must be so directed as to take it from the cleanest areas progressively to and through the less clean areas of the building. Pest control measures should be in place which should include dumpster placement. Drains and traps should be cleaned after each production run, and trench drains should be avoided where food is processed.
Equipment used in processing should be cleanable to the microbiological level, all surfaces should be impervious with no edges that might act as traps. Cleaning schedules should be well organized with each individual involved carefully trained in all areas of his/her involvement. The steps taken in the clean up should be done in exactly the same way each time, and all components of the process well documented. Critical cleaning and sanitizing must be done on a daily basis, some can be performed weekly while a monthly cleaning may suffice in less critical areas.
The materials used in cleaning and sanitation can poise a potential danger to those handling them, so each person in the clean-up crew must be aware of the potential danger. Protective garments must be worn to be in compliance with local, state and federal regulations in place to protect workers from accidents and careless handling. Proper documentation of all steps in plant cleaning is essential if an operation is to avoid possible legal action. Chlorine-based products are those most commonly used in the cleaning and sanitizing of food processing equipment. Such preparations are effective in removing food residues from equipment, they are inexpensive, but their effectiveness is affected by the pH and hardness of the water available. The downside to their use is that they dissipate rapidly, are corrosive to metals and damaging to rubber parts but they do destroy the bad bugs. Other products commonly used in the industry are quaternary ammonium compounds and peroxyacetic acid, each of which is effective and use dependent on individual preference.
The cleaning of equipment and premises should both follow the same basic concept — to progress from the cleanest area to the less crritical areas and never backtrack. To achieve maximum compliance equipment and supplies used in for clean-up activities should be color coded to insure that those brushes used in the cleanest part of the plant are never used in less clean areas. One requisite that some found interesting was that the use of high pressure hoses should never be allowed in areas where food is prepared, on equipment after it has been cleaned and sanitized and never on or near open drains. Drains should never be cleaned when food is exposed, use dedicated equipment only for that purpose and the hydrogen peroxide/quat hybrid is an excellent agent to use in these areas.
Pathogens, those bacteria which may cause illness, react in a variety of ways when subjected to the cheese-making process. Among these are the response of a given species to the cooking time and temperature of the curd and the acidity of the starter. Other factors may include post manufacture conditions and recontamination. The temperature at which cheese is held during aging process is another factor for consideration and it is critical that all cheese made with raw milk be aged for at least 60 days. Salt is added to most cheeses and its presence can have positive effect on controlling bacterial growth.
The other speaker for the day was Cathy Strange, global cheese buyer for Whole Foods Markets. In her presentation Cathy offered examples of small producers whjo have become suppliers to Whole Foods to the mutual benefit of each. As a supplier to Whole Foods every producer, regardless of size, must comply with a list of requirements that ensure the producer and Whole Foods are operating from the same playbook.
In addition to acting as an outlet for the small producer, Whole Foods has also developed a loan program geared to the small producer to allow him/her to expand, upgrade or modify their individual operations. These loans can range from $1,000 to $100,000 depending on the needs, abilities and qualifications of the applicant.
The wealth of information that the attendees were able to take home and incorporate into their own operations was more than most could digest in one sitting, but when one returns to the workshop manual, all of the pieces should fall into place. For those wanting to become more knowledgeable about the subject, send an e-mail to