Cell Counts For Farmers Producing Cheese

Marco Nocetti, is the Head of Laboratory for the Consorzio del Formaggio Parmigiano-Reggiano in Italy. At a recent Pfizer Animal Health press briefing he told Charlotte Johnston, TheCattleSite junior editor why low cell counts are a must for farms that supply milk for cheese.
calendar icon 18 October 2010
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The Parmigiano-Reggiano Cheese Consortium uses somatic cell counts (SCC) as well as other parameters to ensure quality control.

Background

Parmigiano-Reggiano was established in 1934. It now has 237,000 cows dedicated to the production of milk. There are 3,676 farms which supply 15 per cent of national milk production to the 405 Parmigiano-Reggiano member dairies.

To make 1kg of cheese, 16 litres of milk is required, with one wheel of cheese weighing 39 kgs.

In 2009, 2,946,384 wheels of cheese were produced.

Annual turnover from 2008 production (sold in 2009) was €807 million from dairies to traders.

Parmigiano-Reggiano production is 27 per cent of the export quota.

The Parmigiano-Reggiano has specifications that producers must meet. These include feed and production regulations.

Feeding

Mr Nocetti says that the feeding of cattle is based mainly on forage originating from the production area.

"Forage is at least 50 per cent of dry matter intake, and usually alfalfa or lucerne."

For producers adhering to Parmigiano-Reggiano's standards, silage and other fermented fodders/ animal feeds are strictly forbidden.

This, Mr Nocetti explains, is to prevent contamination of clostridia.

Clostridia can cause secondary fermentation which converts sugars and organic acids, resulting in significant losses of dry matter and digestible energy.

No feed additives are permitted either.

Production

The process to make Parmigiano-Reggiano is a complex one, says Mr Nocetti.

Milk is used raw, which means that it cannot be refrigerated. It must therefore be delivered twice a day to the dairy, within two hours of milking.

Copper processing cauldrons are half filled with the naturally skimmed evening milk, and half of the mornings whole milk.

Whey starter is added to milk. This is a natural starter culture of lactic ferments obtained from the spontaneous acidification of the whey remaining after the previous day’s cheese processing.

Natural rennet (which is exclusively obtained for Parmigiano-Reggiano from calves) is used to help curdle the mixture at a temperature of 33-35 degree Celsius for 10-12 minutes.

The curd is then broken up into grains of approximately two to four millimeters and cooked slowly, the temperature gradually increasing from 35 degree to 55 degrees in 15 minutes.

The curd grains are then left to settle for 60 minutes. The mass that is left is then placed into moulds for two to three days.

After this the moulds are put into a bath of salt for 20-25 days at a temperature of 16-18 degrees.

The cheese is then left to mature for 12 months, however it normally continues to be stored at a temperature of 18-20 degree for 20 to 24 months.

Why do Parmigiano-Reggiano dairies need low SCC milk?

Mr Nocetti says that whilst SCC don't have an affect on protein levels in the milk, they do have an effect on other nitrogen compounds such as serumprotein.

High SCC effect milk quality and therefore cheese yields. As cell counts increase, casein levels fall.

Yields

Milk with SCC greater than 100,000 cells/ ml have a casein index of 79.7 per cent. A cell count greater than 300,000 cells/ ml has a casein index that falls to 77.5 per cent. For a cell count great than 600,000 cells/ ml this decreases to 72.4 cells/ ml. Although this may not seem like a large difference the effects on yields are substantial.

A milk batch with 0.1 units more of casein will give 3.3 kg more cheese for every 1,100 kg cauldron.

So even with the same quantity of milk, Mr Nocetti explained, less cheese is made.

For example, 1100 kg of milk, from cows with a cell count of 250,000 cells/ ml, will have a fat percentage of 2.6 and a casein percentage of 2.48.

The same amount of milk, with SCC of 500 ml and a casein percentage of 2.43, will produce 1.58 kg less cheese.

To put this into monetary value, for a dairy with 10 vats (about 500 cows) this equates to a loss of 15.8 kg of cheese per day, or 5,767 kg/ year.

Effectively, through high cell counts, this business is losing €56,228 per year.

Quality

Coagulation

As well as affecting nitrogen compounds, high cell counts also increase levels of sodium, chloride and potassium.

The pH level of the milk increases as cell counts increase. Although a relatively small increase, the change in pH levels has a large impact on coagulation time.


When SCC is less than 400,000 cells/ ml, and pH is 6.67, coagulation time is close to 10 minutes. When cell counts increase to above this, pH reaches 6.71 and coagulation time takes over 12 minutes.

This alternating coagulation time, results in inadequate drawing of the serum from the rind. This in turn produces 'bianchi' or 'smorbi', which during the ageing process transforms into defects on the cheese, said Mr Nocetti.

Inadequate draining of the cheese also causes other defects, such as demineralisation, called 'sfoglia'.

Whey starter

One of the unique processes when producing Parmigiano-Reggiano is the use of natural indigenous why starter.

The whey starter, consisting of lactobacilli, acidifies the milk and curd, destroying undesired bacteria, primarily coliforms and clostridia.

Lactobacilli is a bacteria which helps acidify the product. Lactobacilli is very sensitive to even low amounts of antibiotic residues, much more than coliforms.

These residues then kill the lactobacilli, meaning that the cheese isn't acidified, and the coliforms survive.

These coliforms then produce gas, leaving big balls of air in the cheese, devaluing the product.

Mr Nocetti says that the lower the SCC, the reduced need for antibiotics. Higher cell counts mean that farmers treat the animals with antibiotics, increasing antibiotic residue.

Concluding, Mr Nocetti said that although changes to milk with high SCC only appear small, the effects on cheese quality and yields are substantial.

October 2010
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