**3. Bacteriological quality criteria for industrial processes**

The importance of bacteria in raw milk, as in other food products, is reflected by the fact that the microbiological quality criterion is a "bacteriological criteria".

Preserving and controlling the quality of raw milk is a worldwide concern and is reflected by a "common" criteria of total bacterial counts (TBCs) around 100,000 (105 ) cfu/ml (**Figure 1**).

In the European Union, the directive No 853/2004 defines "Raw milk" as the secretion of the mammary gland of farmed animals that has not been subjected to temperature above 40°C, or undergone "any treatment that has an equivalent effect" [15]. The directive also indicates that the milk, must be "cooled immediately" to not more than 8°C in case of daily collection, or not more than 6°C, if the collection does not occur daily. For cow milk, the bacteriological standard should be lower or equal to 100,000 cfu/ml (determined from the rolling geometric average over a 2-month period with at least two samples per month); for food business operators, the bacteriological level should be below or at 300,000 cfu/ml (**Figure 1**).

In Finland, for example, regarding the criteria for raw milk quality, three classes are defined depending on the bacterial load at farm level: E (excellent), I (first

### **Figure 1.**

*The about 105 cfu/ml "Total bacterial counts in raw milk" world challenge [12–15, 26, 27]. Note: TBC, total bacteria counts; TCC, total coliform counts; SPC, Standard Plate Count.* 

class) and II (non-acceptable for dairy processes), for bacterial counts <50,000, ranging between 50 and 100,000, and exceeding 100,000 cfu/ml, respectively. In 2017, the bacterial content was on average of 5200 cfu/ml (equivalent to 3.71 log10 units) at farm level [16].

The microbiological criteria rely on a culture-based reference method, SPC, which accounts for Standard Plate Count agar method. Total colony forming units of bacteria, eventual yeast and moulds are determined per ml or g of milk, after 32°C for 48 h or 30°C for 72 h incubation: the so-called pour-method is recommended for the analyses [17]. Concerning bacteria, particularly viable mesophiles, aerobes and facultative anaerobes can be enumerated.

As for any method of analyses, drawbacks exist concerning the SPC method:


*Quality and Safety of Bovine Raw Milk: Present Challenges and Technological Solutions DOI: http://dx.doi.org/10.5772/intechopen.83507* 

• The SPC method also ignores important bacterial groups, when considering further treatments to which raw milk is subjected: the level of Gram (+) bacterial types, such as *Bacillus*, *Paenibacillus*, and *Clostridium* present as spores in raw milk, can only be revealed after a preliminary heat treatment of the raw milk samples. Hence, key spoilage bacteria that limit the shelf life of HTST milk [21, 22] are not considered by SPC.

Recently, high-throughput DNA sequencing or molecular barcoding approaches, as non-culture-based methods, were also applied to raw milk, and allowed a more accurate estimation of microbial/bacterial diversity in samples [23, 24].

However, the difficulties and costs for sampling and testing food materials also apply to raw milk testing: in USA, it was already estimated that one analysis of a cost of 5 \$ (US dollars) would result in an annual cost of 150 million \$, if performed daily at the farm level; similarly, if every milk tanker would be tested at the processing plant for one microbial agent, this would lead to a cost of 21 millions \$ [25]. With such costs, it seems impossible to identify all risks for raw milk.
