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The report on the done work
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To present results of work in the form given in tab. 5.3 and to write conclusions about the content of vitamin C and enzymes in various samples of milk.
Table 5.3
| Research technique | Mass fraction in milk | |
| Vitamin С | Fermentov | |
Control questions:
1. What vitamins contain in milk?
2. Essence of a technique of definition of enzymes in milk
3. What is enzymes?
Laboratory work № 6
Studying of technological features of production of pasteurized milk.
Work purpose: To study the theory and practice of thermal treatment of milk. To get acquainted with processing equipment of carrying out pasteurization of milk.To learn to define efficiency of pasteurization.
Task:
1. To investigate influence of temperature and endurance on efficiency of thermal treatment.
2. To investigate influence of the mode of thermal treatment of milk on an inactivation of enzymes.
3. To investigate influence of technology factors on efficiency of pasteurization.
Short theoretical data
Pasteurization – the most widespread way of processing of milk. Pasteurization has possible to destroy pathogenic and vegetative microflora and to make milk and dairy products harmless to consumption. However any thermal impact on dairy raw materials is reflected both in separate components of milk, and in milk as to polydisperse system in general. Therefore it is necessary to select carefully the modes of thermal treatment at technological processing as much as possible to keep the biological value of dairy products.
Pasteurized call the milk subjected to thermal treatment at certain modes and then cooled. Production of pasteurized milk, despite a variety of his types, consists generally of operations, identical to all types of milk: acceptance and assessment of quality of raw materials; raw materials preparation; normalization; cleaning; homogenization; pasteurization; cooling; fasovaniye and packing; marking; storage and realization.
The technological scheme of production of the milk pasteurized
Acceptance and assessment of quality of raw materials
Purification of milk
Milk reservation
Milk normalization
Homogenization
Milk pasteurization
Cooling
Fasovaniye, packing and marking
Storage and realization
The efficiency of pasteurization caused by extent of death of pathogenic microflora influences the choice of the modes and ways of pasteurization (t, ° C and time τ, c), the interrelation of which is established in the form of the following equation:
lnτ= á – β t;
where τ-time of influence of temperature, with;
á, β – coefficients which, according to Cook, for a tubercular stick have according to value 36,84 and 0,48;
t – temperature of pasteurization, ° C.
Depending on these factors appoint three modes of pasteurization:
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- long – at t = 60-63o With with endurance of 1800 with (30 min.);
- short-term – at t temperature = 74-78o With with endurance 20 with;
- instant – at t = 85-87 about With or t = 95-98o With without endurance.
The choice of the mode of pasteurization is defined by technological conditions and properties of a product, and also an indicator of heat stability of milk.
To establish whether pasteurization milk was exposed, whether there was a thermal treatment enough, conduct researches on availability of enzymes of phosphatase and peroxidase. Enzymes are quite sensitive to heating that allows to determine efficiency of various ways of thermal treatment of milk by degree of their inactivation.
Long and high-temperature pasteurization destroy alkaline phosphatase therefore presence of active phosphatase at pasteurized milk indicates or low-quality pasteurization, or hit of raw milk after thermal treatment. As the temperature maximum of destruction of phosphatase is higher than a temperature maximum of destruction of pathogenic microorganisms and toxins, negative reaction to phosphatase reliably protects the consumer from a possibility of spread of diseases through milk and dairy products.
Peroxydase enzyme more thermostable. It collapses at a temperature of 75 ° C with endurance of 10 min., at 80 ° C with endurance 20-30 with or 85o With without endurance therefore on peroxidase it is possible to determine efficiency only of high-temperature pasteurization by test. Also lactoalbumin test can be applied to definition of efficiency of high-temperature pasteurization of milk. She serves for establishment of pasteurization at a temperature over 80 ° C.
Equipment, devices and technical means:
Milk tests, chemical ware (pipettes, test tubes, droppers, measured cylinders), a water bath, an electric tile, holders, solution of yodistokaliyevy starch, 0,5% - ny solution of peroxide of hydrogen, working solution for definition phosphotazy, a system precipitator zinc-copper, the distilled water.
Work performance order
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