Biology 代写 不同类型牛奶发酵率

Biology 代写 生物论文代写

MATERIALS USED

100mL of Long Life UHT cow milk (whole milk)

100mL of Pasteurized cow milk (whole milk)

100mL of Unpasteurized cow milk (raw milk)

18 test tubes

Three 10mL measuring cylinders (+/- 0.05mL)

Water bath

Weighing scale (+/- 0.005g)

Vernier pH probe

6 containers

1 thermometers

Clock

Naming tags

Test tube racks

Thermophilic starter culture containing Lactobacillus bulgaricus and Streptococcus thermphilus

SOURCE OF MATERIALS USED

All the milk, I personally bought with the exception of the raw cow milk that was given to me by a farmer in the rural Kiambu area of Central Kenya. The raw milk had not gone through any further processing after the cow was milked and was packed in a sterilized white plastic bottle.

The Thermophilic starter culture was acquired courtesy of and with permission from the manager of the Palmhouse Dairies in Kiambu. The manager also took time to carefully explain to me the precautions, storage and handling of the Thermophilic starter culture.

The rest of the equipment was provided to me by the Braeburn College laboratory with the help of one lab technician.

D. PROCEDURE UNDERTAKEN

All equipment needed was first sterilized before the experiment was conducted in hot boiling water for 15minutes.

pH of the milk samples was taken before the experiment began. The pH probe after each pH recording was rinsed with distilled water and wiped with tissue

18 test tubes were placed in racks in the water bath of constant temperature. 9 test tubes were placed in each rack so as to differentiate the ones that had the Thermophilic starter culture from the ones that didn’t have. They were then correctly labeled( using milk type and trial)

Three 10mL measuring cylinders were used to measure the volume of each milk type. I used 10mL of milk for the experiment for the different types of milks and for each trial. Different measuring cylinders were used so as to avoid any mixing between the different milk types as these could affect the results I get.

0.11g of the Thermophilic starter culture was weighed on a weighing scale. A white sheet of paper was placed on the weighing scale to avoid the culture form sticking on the surface of the weighing scale. This also made it easier in transporting the culture and putting it in the 9 milk samples that required it.

The culture was mixed thoroughly with the milk using a sterilized wooden splint till all the culture was dissolved.

pH was taken using a pH probe, for the first hour, taken after every 20minutes then after that, after every hour for a total of 7hours.

NOTE:

The pH of the milk was determined by inserting the Vernier pH probe directly into the milk before the Thermophilic culture was added into the milk and also during the fermentation process of all the 18 samples. pH of the milk without the Thermophilic starter culture was taken beforehand so as to avoid contamination with the ones that contained the Thermophilic starter culture. Between pH measurements of each and every sample, the pH electrode was rinsed with distilled water and wiped with tissue after each measurement was taken because the glass bulb in the pH probe is sensitive to heat so I ruled out rinsing it in boiling water.

For the first hour of the experiment, pH was taken after 20minutes. This was done so as to detect how fast the fermentation process was taking place for each and every sample. After the first hour, pH measurements were taken after every hour for the next 6 hours and then finally the pH reading was taken after 24 hours were finalized.

During pH readings, the milk samples were in the water bath at a constant temperature.

Biology 代写 生物论文代写