The title of the research project is, ‘An investigation to compare results of Somatic Cell Counts to a traditional Quality Indicator in Raw Milk’. The title was then further broken down into a subtitle of, ‘An investigation to compare results to establish if there is correlation or relationship between Somatic Cell Counts (SCC) and Total Viable Counts (TVC) in Raw Milk from three dairy herds in County Tyrone.
This investigation will compare the microbial results from three dairy herd’s in County Tyrone. SCC’s are determined using Lactoscan rapid technology whilst TVC’s will be carried out using the traditional ISO method of enumeration.
Silage, faeces, animal bedding and soil contain large numbers of bacteria. The challenge is to reduce numbers entering raw milk to a minimum.
Milk contaminated with bacteria from teat surfaces will, in turn contaminate milking equipment, clusters, milk receivers, pipelines and the bulk tank on the farm prior to collection for processing. Without adequate cleaning, contamination will build up, particularly in hard to clean areas, such as pipeline joints which is why it is vital for TVC’s and SCC’s to be monitored watchfully (O’Brien, 2018).
Food quality and safety is principal within the food industry, as consumer demands and expectancies have risen over the years, resulting in strict legal obligations and controls throughout the supply chain. Traditional microbiological techniques within the food industry are of very much use and an admirable indicator of raw milk quality but with new innovative technologies available rapid methods are sought to be of more use (Membré, 2007).
Rapid microbiological technologies are time saving devices which allow for automation, standardisation, reliability and faster microbial results of food samples allowing decisions to be made instantaneously to allow effectively and efficiently business operations.
The Food industry are moving away from traditional methods and adapting to new rapid methods, although automation comes with a considerable cost, food companies believe the benefits of the machinery overlook these costs.
3.2. Raw Milk
Milk is very nutritious and is susceptible to contamination and growth of a multitude of bacteria. Jensen, 1995 milk provide protein, minerals, vitamins and fatty acids.
Raw milk may contain anything from a few thousand bacteria per ml if it comes from a hygienic farm and up to several millions if the standard of hygiene, chilling and sanitation is poor. Daily cleaning and disinfection of all equipment is there for most decisive factor in the bacteriological quality of milk according to Bylund, 2003.
Bylund states under optimal conditions it would be possible to achieve a bacterium count of less than 20,000 cfu/ml (Bylund, 2003).
Rapid chilling of raw milk on farm to below 4oC contributes greatly to the quality of milk at farm pre-collection. Chilling the raw milk acts as a hurdle in preservation of milk along with a combination of other hurdles. Chilling milk on farm slows down the growth of the bacteria in milk, thus prominently improving its keeping qualities.
There are three principle sources of infection, inside the cow, the udder and everything the milk comes in contact with. The most common microorganisms in raw milk of high quality is restricted to a few groups of bacteria. Commonness of main groups of bacteria in low count raw milk respectively are Micrococcus, Streptococcus, Asporogenous gram-pos. rods, Gram-neg. rods and spore formers according to Bylund, 2003.
Current economic situation which many dairy farmers in Northern Ireland is of much uncertainty and dependable on monthly milk payments. Generally, milk quality is related to the payment system to farmers, with the milk price being related to protein content, fat content, TVC and or SCC depending on the processor. Some processors also include the concentration of free fatty acids in the milk in their payment system. Milk quality is affected by genetics, feeding of the dairy cow, lactation number, lactation period and management of the cow. These factors are often not possible to take into consideration before the milk is processed; however, they are often recognised at processor levels as seasonal variations according to PAŠIĆ et al., 2016. But TVC and SCC can be monitored and controlled to ensure higher end payments are received (Murphy et al., 2016).
3.3. Milk Quality
There are two key elements to producing high quality milk according to O’Brien, 2018. Producing milk of low SCC, shows a reflection of good udder health and mastitis control in the herd. Secondly low TVC, a low TVC is an indicator of good milking plant hygiene and milk storage regimes.
3.3.1. Importance of Milk Quality
High quality raw milk is required to make high quality dairy products. Once raw milk is defective, it cannot be improved during processing, and defects often become more pronounced and affects yield and profitability of many products. Therefore, it is imperative that raw milk be produced and handled from farm to processing facilities under conditions that do not reduce its quality or, consequently, the quality of the product. Many factors can influence the quality of raw milk from seasonality, lactation period, breed to hygiene practices.
3.3.2. Milk Quality Tests
Milk testing and quality governance is an essential component of any milk processing whether small artisan enterprise or large processors supplying to international markets. Milk being made up of 87% water is prone to adulteration by corrupt middlemen and unfaithful farm workers. Moreover, its high nutritive value makes it an ideal medium for the rapid multiplication of bacteria, particularly under unhygienic production and storage at incorrect temperatures. Harding, 1995 states the principle in order for any processor to make good dairy products, high quality raw materials are essential. A milk processor will only be assured of the quality of raw milk if certain basic quality tests are carried out at various stages of transportation of milk from the producer to the processor and finally to the consumer with initial TVC’s and SCC’s used to predict yields and quality through various models (Harding, 1995).
3.4. Somatic Cell Counts (SCC)
SCC is a main indicator of milk quality which is widely used in the dairy industry to dictate the price per litre the producer receives. The majority of somatic cells are leukocytes (LKCS) commonly known as white blood cells (WBC) which become present in increasing numbers in milk usually as an immune response to a mastitis-causing pathogen and a small number of epithelial cells, which are milk-producing cells shed from inside of the udder when an infection occurs in cows according to Oliver, 2010.
3.5. Total Viable Count (TVC)
TVC is the number of bacteria in a sample that can grow and form countable colonies on Standard Methods Agar after being incubated at 30°C for 72 hours in accordance with ISO 4833-1:2013. European Union (EU) legislation specifies that total bacterial count (TBC) in milk should be less than 100,000cfu/ml. Conversely and ideally on many farms a TBC of less than 15,000/ml can be reached with goof hygiene practices emphasized (British Standards Institution, 2013).
3.6. Microbiological Guidelines
Microbiological guidelines are issued for food category to determine if the product is acceptable for human consumption, by assessing the safety and quality of the food product in accordance to the established standards