Cleanliness The environment of production has a great effect on the quality of milk produced From the food science perspective, the production of the highest quality milk should be the goal However, this is sometimes not the greatest concern of those involved in milk production Hygienic quality assessment tests include sensory tests, dye reduction tests for microbial activity, total bacterial count(standard plate count), sediment, titratable acidity, somatic cell count antibiotic residues. and added water The two common dye reduction tests are methylene blue and resazurin. These are both synthetic compounds which accept electrons and change colour as a result of this reduction As part of natural metabolism, active microorganisms transfer electrons, and thus rate at which dyes added to milk are reduced is an indication of the level of microbial activity Methylene blue turns from blue to colorless, while resazurin turns from blue to violet to pink to colourless. The reduction time is inversely correlated to bacterial numbers. However, different species react differently. Mesophilics are favoured over pscchrotrophsa, but psychrotrophic organisms tend to be more numerous and active in cooled milk Temperature Milk production and distribution in the tropical regions of the world is more challenging due to the requirements for low-temperature for milk stability. Consider the following chart illustraing the numbers of bacteria per millilitre of milk after 24 hours 2.600 10°C 11,600 18800 15.5°C180,000 20°C 450.000 Traditionally, this has been overcome in tropical countries by stabil izing milk through means other than refrigeration, including immed iate consumption of warm milk after milk ing, by boil ing milk, or by conversion into more stable products such as fermented milk Mastitis and antibiotics Mastitis is a bacterial and yeast infection of the udder milk from mastitic cows is termed abnormal. Its SNF, especially lactose, content is decreased, while Na and Cl levels are increased, often giving mastitic milk a salty flavour. The presence of mastitis is also d by increases in bacterial numbers, includ ing the possibility of human6 Cleanliness The environment of production has a great effect on the quality of milk produced. From the food science perspective, the production of the highest quality milk should be the goal. However, this is sometimes not the greatest concern of those involved in milk production. Hygienic quality assessment tests include sensory tests, dye reduction tests for microbial activity, total bacterial count (standard plate count), sediment, titratable acidity, somatic cell count, antibiotic residues, and added water. The two common dye reduction tests are methylene blue and resazurin. These are both synthetic compounds which accept electrons and change colour as a result of this reduction. As part of natural metabolism, active microorganisms transfer electrons, and thus rate at which dyes added to milk are reduced is an indication of the level of microbial activity. Methylene blue turns from blue to colorless, while resazurin turns from blue to violet to pink to colourless. The reduction time is inversely correlated to bacterial numbers. However, different species react differently. Mesophilics are favoured over pscchrotrophsa, but psychrotrophic organisms tend to be more numerous and active in cooled milk. Temperature Milk production and distribution in the tropical regions of the world is more challenging due to the requirements for low-temperature for milk stability. Consider the following chart illustraing the numbers of bacteria per millilitre of milk after 24 hours: 5°C 2,600 10°C 11,600 12.7°C 18,800 15.5°C 180,000 20°C 450,000 Traditionally, this has been overcome in tropical countries by stabilizing milk through means other than refrigeration, including immediate consumption of warm milk after milking, by boiling milk, or by conversion into more stable products such as fermented milks. Mastitis and Antibiotics Mastitis is a bacterial and yeast infection of the udder. Milk from mastitic cows is termed abnormal. Its SNF, especially lactose, content is decreased, while Na and Cl levels are increased, often giving mastitic milk a salty flavour. The presence of mastitis is also accompanied by increases in bacterial numbers, including the possibility of human