The mixture was allowed to stand for at least 5 min and subsequently filtered. 5 ml of the filtrate was collected in a test-tube and then placed in boiling water bath for at least 5 min. The test-tube containing filtrate was then cooled in cold water and the contents were examined for presence of turbidity. Results discussion Table 4: Turbidity test results Sample Observation Pasteurized milk a cloudy pale yellow solution with precipitation was observed. Uht milk a cloudy pale yellow solution was observed. Sterilized milk a clear pale yellow solution was observed. The turbidity test is useful in telling us if a sample of milk is sufficiently sterilized, whereby a clear solution will be observed.
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Secondly, it was observed that the dilution of products of a more art viscous consistency, such as sour cream and lemon curd, did not yield a homogenous consistency as compared with the milk samples and yoghurt. As such, the titrated naoh may not have actually reacted with all the acid molecules as some acid molecules may be trapped inside the granular particles. This can be overcome by vortexing the cream and water mixture in a sealed round-bottom conical flask to ensure a homogenous solution is obtained, allowing us to obtain more accurate titration results. Thirdly, for runny liquid samples such as milk, there is a risk of spillage due to splashing when the magnetic stirrer operates probably due to the large exposed opening of the porcelain basin. Splashing can be overcome by using a conical flask to contain the samples and place a white tile under the conical flask so that the change in colour of milk can be made more obvious. This is because a conical flask has a much narrower neck and therefore a significantly narrower opening, thus minimizing spillage from splashing. In this way, more accurate titration results can be obtained. For lemon curd, simply measuring the citric acid concentration is insufficient to conclude a quality product. This is mainly due to the possibility of adulteration of lemon curd by adding more citric acid chemical, just like how milk was adulterated by the adding melamine. As such, additional qualitative methods can be employed, such as measuring the concentration of certain chemical substances more unique to lemon, such as limonene. Turbidity test for pasteurized, uht and sterilized milk materials Ammonium sulphate powder Pasteurized milk uht milk Sterilized milk method.0g of ammonium sulphate, (NH4)2SO4, was dissolved.0 ml writing of pasteurized milk.
Hence, it can be deduced that this sample of lemon curd has passed the quality control measure. Citric acid is used as the reference for quality control of lemon curd mainly because citric acid is present in the largest quantity in lemons. Hence, measuring citric acid concentration present will be a good measure of the quality of the lemon curd. As such, this is a quality lemon curd sample. Even though this lemon curd product expired on February 2012, the citric acid content should not be significantly affected by microbial decomposition mainly because the acidic environment due to citric acid is not suitable for most bacteria presentation to thrive. Discussion There are a few experimental procedures which can be improved. Firstly, as mentioned in the results of experiment 1, the faint pink observed to mark the end-point of titration is subject to a large margin of human error. As such, a better method to solve the issue of colour subjectivity is to use a colorimeter to determine an intensity of pink as the end-point of titration, thus eliminating any inaccuracies that result from human error.
Of naoh required for neutralization. This second observation also proves that pH is not a true measure of total lactic acid content in dairy products as this small difference in pH is accompanied by a larger than proportionate difference in volume of naoh required for neutralization. Experiment 3: Titratable Acidity of Lemon Curd Table 3: Titration of lemon curd against.105m naoh sample mass of sample (g) average mass of sample (g) initial burette reading (ml) final burette reading (ml) vol. Of naoh used* (ml) Lemon Curd.00.00.00.20.80.35.00.20.90.30.00.00.60.40 *As 3 sets of titration were conducted for each sample in order to improve the precision and reproducibility of the titration results, the average volume. Of naoh used in titration so as to be more precise. C nao- o ch 2 c o- na o ch 2 c o- na h 2 c oh 2 c oh o 3naoh à 3H2o - (2) Amount of naoh used (Average vol. Of naoh used) x naoh (20.35/1000.105).14 x 10-3 mol estate From (2 citric acid : naoh is 1:3 amount of citric acid.00g of lemon curd (amount of naoh used) /.13 x 10-4 mol Molar mass of citric acid 6(12) 8(1).
Of naoh used) x naoh (12.30/1000.105).29 x 10-3 mol From (1 lactic acid : naoh is 1:1 amount of lactic acid.99g of yoghurt.29 x 10-3 mol Mass of lactic acid.99g of yoghurt (amount of lactic acid) x (molar. This is because lactic acid is an organic acid and hence it is a weak acid. As such, lactic acid only partially dissociates, giving a h that is lower than the total lactic acid concentration. This is due to the low acid dissociation constant, ka, of lactic acid. However, by proportionality, it is observed that higher concentrations of lactic acid molecules will give a higher deprotonated. This is observed in Table 2 where the lower pH of yoghurt corresponds to a higher average volume of naoh required to neutralize the lactic acid present. In addition, another observation is that yoghurt requires more than twice the volume.1m naoh to neutralize the lactic acid present as compared to sour cream even though yoghurt is lower in pH.11. This is mainly attributed to the presence of probiotics added into yoghurt. As such, this means that more lactose in yoghurt is converted into lactic acid, resulting in the marked difference in average vol.
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This suggests that pasteurized milk contains slightly more microbes than uht milk, which goes in tandem with the properties of make pasteurized milk. This is because pasteurized milk is heated to about 65oC for at least 30 minutes in order to preserve the flavor of milk, while uht milk is heated at 135oC for about 2 seconds6. Hence, fewer microbes are killed in pasteurized milk than uht milk. As such, pasteurized milk will have slightly higher lactic acid concentration which is produced from the fermentation of lactose by microbes. However, the magnitude of difference.001 g/100mL obtained from the titration results is too small to make the above conclusive deduction. Of naoh used is almost identical for both milk samples as there is only a difference.05 ml, making the titration results somewhat anomalous.
The main reason for this anomaly is the subjectivity of the end-point of titration. The colour change of phenolphthalein from colourless to pale pink is very difficult to ascertain by naked eye for the inexperienced, unlike workers in this industry who carry out large volumes of titrations every day. As such, the faint pink that i observed in pasteurized milk is most probably not the true end-point of titration or it could be that the faint pink i observed in uht milk is over the end-point of titration for uht milk. Experiment 2: Titratable Acidity of Cream Table 2: Titration of sour cream keywords and yoghurt against.1m naoh cream sample pH of sample average pH mass of sample (g) average mass of sample (g) initial burette reading (ml) final burette reading (ml) vol. Of naoh used* (ml) sour Cream.48.49.00.00.00.60.40.40.50.01.60.20.18.104.22.168.80.40 Yoghurt.43.38.01.99.00.90.10.30.34.00.90.60.22.214.171.124.30.30 sour Cream. Of naoh used) x naoh (5.40/1000.105).67 x 10-4 mol From (1 lactic acid : naoh is 1:1 amount of lactic acid.00g of sour cream.67 x 10-4 mol Mass of lactic acid.00g of sour cream (amount of lactic acid).
Initial and final burette readings were recorded in Table 3 below. The procedure was repeated two more times. Results, experiment 1: Titratable Acidity of Milk. Table 1: Titration of pasteurized and uht milk against.01m naoh. Of milk measured (ml) average vol.
Of milk (ml) initial burette reading (ml) final burette reading (ml) vol. Of naoh used (ml) average vol. Of naoh used* (ml). Pasteurized Milk.0.0.00.65.126.96.36.199.188.8.131.52.80.35 uht milk.0.0.00.70.184.108.40.206.220.127.116.11.00.30 Pasteurized Milk ch 3 ch o- na o ch 3 ch. Of naoh used) x naoh (12.35/1000.0107).32 x 10-4 mol From (1 lactic acid : naoh is 1:1 amount of lactic acid.0ml of pasteurized milk.32 x 10-4 mol Concentration of lactic acid (in mol/100mL) equivalent in pasteurized milk (1.32 x 10-4). Of naoh used) x naoh (12.30/1000.0107).31 x 10-4 mol From (1 lactic acid : naoh is 1:1 amount of lactic acid.0ml of uht milk.31 x 10-4 mol Concentration of lactic acid (in mol/100mL) equivalent in uht milk (1.31 x 10-4). As such, both samples are deemed safe for consumption. The titratable acidity of pasteurized milk is also observed to be slightly above that of uht milk by a very minute concentration.001 g/100mL.
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Experiment 2: Titratable Acidity of Cream.00 g of sour cream was transferred to a white porcelain basin. 10.0 ml of water was added to the sample and mixed and pH was then long measured. 1.0 ml of phenolphthalein indicator was added to the diluted sample. The burette was filled up with.1m naoh and then titrated against the sour cream sample. Initial and final burette readings were recorded in Table 2 below. The procedure was repeated thrice for both sour cream and yoghurt. Experiment 3: Titratable Acidity of Lemon Curd.00 g of lemon curd gender was transferred to a white porcelain basin. 10.0 ml of water was added to the sample and mixed. The burette was filled up with.1m naoh and then titrated against the lemon curd sample.
3 sets of titrations for 3 different groups of food products, mainly pasteurized milk and uht milk, sour cream and yoghurt, and lemon frog curd, were carried. Experiment 1: Titratable Acidity of Milk.0 ml of pasteurized milk was transferred to a white porcelain basin. 1.0 ml of phenolphthalein indicator was then added to this sample. The burette was filled up with.01m naoh and then titrated against the pasteurized milk sample. End-point of titration was identified when a pale pink colouration persisted for at least. Initial and final burette readings were recorded in Table 1 below. The procedure was repeated thrice for both pasteurized and uht milk.
14/9/12. Yoghurt (f n alive yoghurt expires on 11/9/12.1M sodium hydroxide (actual concentration.105M) pH meter, experiment 3: Titratable Acidity of Lemon Curd. Lemon curd (Waitrose lemon curd expired on Feb.1M sodium hydroxide (actual concentration.105M). Methods, titration of selected food products against naoh of known concentrations were carried out in order to determine the titratable acidity of these food products. The titratable acidity in lactic acid or citric acid equivalent was then determined by via stoichiometric ratio of the acid to the amount of naoh, as seen in the stoichiometric calculations below.
The titratable acidity test allows us to determine the titratable acidity of a sample as lactic acid (for dairy products) or citric acid (for lemon curd) equivalent. Basically, ta, as an acid equivalent, of a food product measures the total amount of that particular reference acid in the selected food. This reference acid is the major acid component, amongst all types of acid present in the food, which we want to quantify. Ta is different from pH as pH only measures the h dissociated from the acid molecules. Hence, ta is a more accurate measure of the degree of spoilage of dairy products summary than. The turbidity test however, serves a different function in terms of quality control. It is usually used by the industry to test if sterilized milk products have been sufficiently sterilized. Titratable Acidity of Selected foods. Materials, phenolphthalein as indicator.00ml burette.0ml graduated pipette, white porcelain basin, magnetic stirrer.
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Kalkulator, wybierz produkt który ciebie interesuje, produkt. Typ, grubość, metoda docinania, wymiary. Szerokość (cm) - wysokość (cm) - aby zakupić towar o london podanych wymiarach należy zakupić w sklepie, artcop sztuk. Print, reference this, published: 23rd March, 2015, milk and dairy products, such as cream and yoghurt, are an important food group in the food pyramid. This food group provides us with calcium, which is not only crucial in strengthening our bones, but also important in many biological processes, such as facilitating the release of neurotransmitters that transmit nerve impulses across a synapse. Since dairy products serve such importance in our diet, dairy products manufacturing industry takes extra precaution in ensuring that these products meet the guidelines set by statutory bodies, one of which is that the maximum lactic acid content allowed in milk.15 w/w. Hence, the industry will employ various methods to determine the quality of milk. As such, in order to better understand these industrial methods, 2 groups of experiments relating to titratable acidity (TA) of selected foods and turbidity test for pasteurized, uht and sterilized milk were carried out.