Explore this issueApril/May 2016
Nobody really knows when cheese making started. Several myths describe how cheese making originated with one of the most popular legends dating back 4,000 years ago. It describes an Arab trader who had to cross the desert and he carried milk in a pouch made from a sheep’s stomach. Since there was rennet in the lining of the pouch, and with the heat generated by the sun, the milk separated into whey and curd. When he tasted the whey in the evening, he found that it satisfied his thirst, and the curd his hunger.
According to recent findings by the research group of Richard Evershed from the University of Bristol, cheese making dates back to the Neolithic period, much before the Arab trader story. His group found traces of dairy fat in ancient ceramic fragments, supposedly used as cheese-strainers, in Poland, which suggest that people have been making cheese in Europe for up to 7,500 years.
However, some of the cheeses we know today, like Gouda, Parmesan, and Cheddar, have their beginning in the Middle Ages.
The mass production of rennet is said to have started around 1860 and industrial cheese production followed in the 20th century.
Types of Cheeses
Considering that cheese is made from a single ingredient, milk, how is it possible to have so many different types of this product? There are many factors affecting cheese making, from the milk source and its quality to several factors involved during production.
How many varieties of cheeses are being produced? This is a difficult question to answer. Cheese can be classified using different criteria. Such as milk source (e.g. cows, goat, sheep, or buffalo milk), softness degree (soft, semi-soft, semi-hard, and hard), by geography (country or region), production method, curing or ripening duration, fat content, etc. According to the International Dairy Federation, there are 500 types of cheese. Sandine and Elliker mention 1,000 and the website Cheese.com references more than 1,700 different cheeses.
The Global Cheese Market
As previously mentioned, large scale industrial production of cheese emerged in the 19th century and exhibited breath-taking growth. By the end of the 19th century, the industry was reported to have produced 98 million kilogram (kg) of cheese per year and by end of the 20th century, it was already 10 times as much. It is estimated that in the U.S., about 30 percent of all milk goes into cheese production. And the global cheese market is estimated to have a value of U.S. $80 billion and will reach U.S. $105 billion in three years from now, with a healthy growth of a CAGR of 4.4 percent.
Specifically for Parmigiano Reggiano, the production of cheese wheels levels around 3.3 million per year, limited by the geographic region in which it can be produced and the amount of milk coming from that region. Based on the sales price of approximately U.S. $18/kg at a major Italian supermarket (price on Jan. 16, 2016) and the average weight of a cheese wheel of 38 kg, this results in a total U.S. $2.2 billion sales value—which gives plenty of incentive for fraud.
What is Food Fraud
Food fraud encompasses two aspects: the deliberate misrepresentation of a product, e.g. a champagne label on a bottle that contains sparkling wine from a region other than the French champagne; and the deliberate modification of a product, e.g. by dilution, addition, or replacement of an expensive ingredient with a cheap one.
Although not the oldest business in the world, food fraud is not far from it. In 1820, the first book on food adulteration (and methods of detection) was written by Fredrick Accum, a German chemist living in London. The subtitle on the cover features cheese as a product of adulteration. The chapter on cheese adulteration is titled “Poisonous Cheese” and discusses the addition of red lead to annatto for coloring. Today, the addition of red lead is less likely, however, a look at the USP Food Fraud Database reveals that other adulterants are being used.
Fraudulent practices affecting milk include dilution with water to increase the volume in conjunction with melamine to increase the apparent protein content. Although the main purpose of adulteration practices is solely economic, some cases also pose a safety risk to consumers. For example, the instance of melamine added to milk caused the death of several children in China when used in infant formula.
Premium milks from buffalo, sheep, or goat are frequently mixed with less expensive cows milk. In some countries, cows’ milk is more expensive and mixtures with goat and sheep milk have been reported.
Other typical adulteration includes the use of reconstituted milk powder instead of fresh milk, as well as the addition of detergent, urea, formaldehyde, hydrogen peroxide, salt, potato starch, and hydrolyzed leather. Some compounds are approved to use within legal limits, and beyond this point they may be consider adulterants, such as cellulose used as an additive to prevent clumping of the product, including grated cheese.
The USP Food Fraud Database carries no less than 474 entries on milk and milk products for the years 2000 to 2015, and milk adulteration is the second most frequently reported issue. This is in stark contrast to the European Rapid Alert System for Food and Feed database called RASFF. This database contains only 30 entries in the same timeframe when queried for product category “milk and milk products” and hazard category “adulteration/fraud.” None of them list the Risk Decision as “serious.” Interestingly, melamine does not even appear in the query results, even when querying the RASFF database using only the criteria “milk and milk products” under category and “serious” under Risk Decision. This is due to the fact that although the database contains 337 entries on melamine, only four notifications relate to melamine in milk, and in all cases the Risk Decision is “undecided.” This indicates that the RASFF portal does not provide a good representation of food fraud cases when only searched in the hazard category “adulteration/fraud,” a definition that should be revised by the European Authorities. It also does not correlate with the report provided to the European Parliament in 2014 on food fraud. This report lists milk and milk products, including cheese, as fourth most frequently adulterated product category.
With regards to the misrepresentation of products, Europe has created legislation to protect premium food products.
In its latest regulation EC 1151/2012, superseding the earlier regulation EC 510/2006 on quality schemes for agricultural products and foodstuffs, the European Commission clearly defines in article 12 the use of the PDO (Protected Designated Origin) label. Currently 600 products carry the PDO label, of which 186 are cheeses, 49 are from Italy.
The remainder of this article will focus on Parmigiano Reggiano cheese, one of the most popular PDOs, which was first registered in 1996. The region in which it is produced is limited to Parma, Reggio Emilia, Modena, and parts of the provinces of Mantua and Bologna, on the plains, hills, and mountains between the rivers Po and Reno. Cattle, which milk is used for the production of Parmigiano, cannot be fed silage or fermented feeds, and no additives or preservatives can be used. It was apparently Benedictine monks who started producing this cheese. Today’s production of a wheel requires 600 liters of milk. The resulting cheese wheel is left to dry and forms a natural, edible crust. The minimum maturation time is 12 months, longer than many similar cheeses.
To protect PDO products, like Parmigiano Reggiano cheese, the European Commission has bilateral agreements with some countries. There is no such agreement with the U.S., which is why one can find generic products on the market labeled Parmesan, Champagne, Camembert, etc. that do not have their origins in Europe.
Common Approaches to Detect Food Fraud
The forms of adulteration like dilution with water, skimming, or removal of fat and addition of fluid skim milk can be detected from specific gravity and fat content. Immunological technologies and polymerase chain reaction, or PCR, can be used to determine a blend of milks (e.g. cows’ milk in goat) and results are expressed as approximate content (percentage). The addition of cows’ milk can also be detected by the presence of ß-carotene, which is absent in goat milk. There are other technologies that have been or are still being used for the detection of adulteration of milk and cheese.
Today, routine checks for incoming materials are often done by near infrared spectroscopy (NIR) or fourier transform infrared spectrometry, or FTIR. These are useful techniques as they assess profiles instead of single parameters. NIR technology focuses mainly on three major chemical entities: C-H, N-H, O-H, and C-O-H, representing sugar, water, protein, and fat. This is insufficient to identify all adulterants or changes unrelated to any of these structures.
Novel Methods of Detection
Nowadays, cases of fraud tend to be substantially more sophisticated, and scientists are behind some of them. In many instances fraudsters take advantage of the limitation of detection methods or by the fact that many compounds are not normally associated with foods and therefore are not looked for. Melamine is a very good example: In order to perform this fraud and keep it covered, it is important to understand that one of the quality parameters for milk, protein content, is not measured directly. Instead, it is assessed by methods (Kjeldahl and Dumas), which determine nitrogen content. Such methods do not only determine nitrogen in the protein structure, but also nitrogen in other compounds present in the sample. Therefore, more nitrogen does not necessarily translate into more protein and thus higher quality.
Since many fraudsters target methods of analysis, it is critical to develop new strategies to counteract. One good option is the use of novel technologies that allow the simultaneous assessment of a wide range of different variables, which in their entirety, is difficult to fool.
Among the novel technologies worth mentioning is the combination of high-resolution mass spectrometry with sophisticated multivariate statistical analysis. The data generated by the mass spectrometric analysis are processed by software that generates a three dimensional model (see Figure 1), which looks like a sphere. A key precondition for developing these models is to have a certain number of reference samples known to be authentic. The non-targeted approach that Mérieux NutriSciences has developed to verify the authenticity of Parmigiano Reggiano was built on one reference sample provided by the Parmigiano Reggiano Consortium.
After the model has been built, unknown samples are analyzed and compared with the multi-variable model. The model will distinguish samples that are compliant (authentic Parmigiano Reggiano) from those which are not. If not, there is a high probability that a sample is adulterated or mislabeled.
In case of the Parmigiano Reggiano model, the high-resolution non-targeted mass spectrometry in conjunction with statistics already provided a good prediction rate. This could be further improved by assessing additional targeted variables, e.g. compound only present in silage feed. This approach yielded a 100 percent prediction rate when tested on blind samples sent by the Parmigiano Reggiano Consortium.
The principle of this non-targeted approach can easily be transferred to other premium products as long as reference materials are available. In the case of extra virgin olive oil, not only the country and region could be predicted, but also the year of the olive harvest.
The work demonstrates that older and costly approaches do not always lead to better or more accurate results. The novel non-targeted approach, based on numerous examples, can result in ideal prediction of adulterated or mislabeled sample.
Popping, is chief scientific officer at Mérieux NutriSciences Corp. Reach him at firstname.lastname@example.org. And de Dominicis is head of research and development at Mérieux NutriSciences in Italy. Reach him at email@example.com.