The Turbidity Test for Pasteurized Milk

The Turbidity Test for Pasteurized drawMilk and dairy farm farm harvest-times, much(prenominal) as convulse and yogurt, be an important food group in the food pyramid. This food group provides us with calcium, which is not only crucial in streng and thening our bones, but also important in many an(prenominal) biological processes, such as facilitating the release of neurotransmitters that transmit nerve impulses crossways a synapse. Since dairy products serve such importance in our diet, dairy products manufacturing diligence takes extra precaution in ensuring that these products meet the guidelines set by statutory bodies, one of which is that the maximum lactic savage content tot exclusivelyyowed in draw is 0.15% w/w. Hence, the industry pull up stakes employ various methods to match the quality of take out. As such, in order to better understand these industrial methods, 2 groups of experiments relating to titratable sullenness (TA) of selected foods and turbi dity testing for change integrity, UHT and sterilised take out were carried egress. The titratable deadlyulentity test allows us to determine the titratable moroseness of a attempt as lactic sulphurous (for dairy products) or citric panelling (for lowlife curd) alike. Basically, TA, as an acid equivalent, of a food product measures the centre numerate of that particular reference acid in the selected food. This reference acid is the major(ip) acid component, amongst all types of acid cave in in the food, which we want to quantify. TA is different from pH as pH only measures the H+ dissociated from the acid gram moleculeecules. Hence, TA is a more(prenominal) accurate measure of the degree of spoilage of dairy products than pH. The turbidity test however, serves a different function in hurt of quality verify. It is unremarkably employ by the industry to test if disinfect draw products have been sufficiently sterilized.Titratable acidulousness of Selected Food sMaterialsPhenolphthalein as indicator50.00ml buret10.0ml graduated pipetteWhite porcelain basinMagnetic sc atomic number 18monger examine 1 Titratable moroseness of MilkPasteurized milk (Farmhouse Fresh Milk), expires on 20/9/12UHT milk (Marigold UHT Full skim over), expires on 15/6/130.01M sodium hydroxide (actual assimilation is 0.0107M) essay 2 Titratable Acidity of jactitateSour beat (Bulla Sour Cream), expires on 14/9/12Yoghurt (FN Alive Yoghurt), expires on 11/9/120.1M sodium hydroxide (actual constriction is 0.105M)pH meterExperiment 3 Titratable Acidity of bum CurdLemon curd (Waitrose git curd), expired on Feb 120.1M sodium hydroxide (actual concentration is 0.105M)MethodsTitration 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. 3 sets of titrations for 3 different groups of food products, in the main pasteurized milk and UHT milk, forbidding cream and yoghurt, and lemon curd, were carried.Experiment 1 Titratable Acidity of Milk10.0 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 fill up with 0.01M NaOH and then titrated against the pasteurized milk sample. End-point of titration was identified when a demented tap coloring material persisted for at least 10 s. Initial and nett burette nurtures were enter in Table 1 below. The procedure was restate thrice for twain pasteurized and UHT milk.Experiment 2 Titratable Acidity of Cream10.00 g of sour cream was transferred to a white porcelain basin. 10.0 ml of water supply was added to the sample and abstruse and pH was then measured. 1.0 ml of phenolphthalein indicator was added to the dilute d sample. The burette was filled up with 0.1M NaOH and then titrated against the sour cream sample. End-point of titration was identified when a pale pink colouring material persisted for at least 10 s. Initial and nett burette readings were record in Table 2 below. The procedure was repeated thrice for both sour cream and yoghurt.Experiment 3 Titratable Acidity of Lemon Curd10.00 g of lemon curd was transferred to a white porcelain basin. 10.0 ml of water was added to the sample and mixed. 1.0 ml of phenolphthalein indicator was added to the diluted sample. The burette was filled up with 0.1M NaOH and then titrated against the lemon curd sample. End-point of titration was identified when a pale pink colouration persisted for at least 10 s. Initial and final burette readings were recorded in Table 3 below. The procedure was repeated two more times.ResultsExperiment 1 Titratable Acidity of MilkTable 1 Titration of pasteurized and UHT milk against 0.01M NaOHMilk samplevol. of milk m easured (ml) middling vol.of milk (ml)initial burette reading (ml)final burette reading (ml)vol. of NaOH used (ml)average vol. of NaOH used* (ml)Pasteurized Milk10.010.050.0037.6512.3512.3510.037.6525.1512.5010.025.1512.8012.35UHT Milk10.010.050.0037.7012.3012.3010.037.7025.3012.4010.025.3013.0012.30Pasteurized MilkCH3CHOHCO- Na+OCH3CHOHCOHO+ NaOH + H2O (1) tote up of NaOH used = (Average vol. of NaOH used) x NaOH= (12.35/ vitamin C0)(0.0107)= 1.32 x 10-4 molFrom (1), lactic acid NaOH is 11amount of lactic acid in 10.0ml of pasteurized milk = 1.32 x 10-4 molConcentration of lactic acid (in mol/100mL) equivalent in pasteurized milk= (1.32 x 10-4) / (10/100)= 1.32 x 10-3 mol/100mLConcentration of lactic acid equivalent in g/100mL in pasteurized milk= (molar concentration (in mol/100mL) of lactic acid equivalent) x (molar chew of lactic acid)= (1.32 x 10-3)(90.08)= 0.119 g/100mLUHT MilkAmount of NaOH used = (Average vol. of NaOH used) x NaOH= (12.30/1000)(0.0107)= 1.31 x 10-4 molFr om (1), lactic acid NaOH is 11amount of lactic acid in 10.0ml of UHT milk = 1.31 x 10-4 molConcentration of lactic acid (in mol/100mL) equivalent in UHT milk = (1.31 x 10-4) / (10/100)= 1.31 x 10-3 mol/100mLConcentration of lactic acid equivalent in g/100mL in UHT milk= (molar concentration (in mol/100mL) of lactic acid equivalent) x (molar mass of lactic acid)= (1.31 x 10-3)(90.08)= 0.118 g/100mLFrom the calculations, it locoweed be seen that both the titratable acidities of pasteurized milk and UHT milk in lactic acid equivalent are below 0.15%, the maximum allowed titratable acidity of milk in lactic acid equivalent. As such, both samples are deemed safe for consumption. The titratable acidity of pasteurized milk is also observe to be disregardly to a high place that of UHT milk by a very comminuted concentration of 0.001 g/100mL. This suggests that pasteurized milk contains slightly more microbes than UHT milk, which goes in tandem with the properties of pasteurized milk. This is because pasteurized milk is heatinged to somewhat 65oC for at least 30 minutes in order to preserve the smack of milk, while UHT milk is heated at 135oC for about 2 seconds6. Hence, few microbes are effaceed in pasteurized milk than UHT milk. As such, pasteurized milk get out have slightly higher lactic acid concentration which is produced from the fermentation of milk sugar by microbes.However, the magnitude of difference of 0.001 g/100mL compassed from the titration results is alike blue to make the above conclusive deduction. The average vol. of NaOH used is near identical for both milk samples as on that point is only a difference of 0.05 ml, making the titration results roundwhat anomalous. The main reason for this anomaly is the subjectiveness of the end-point of titration. The colour change of phenolphthalein from colourless to pale pink is very rocky to ascertain by naked eye for the inexperienced, unlike workers in this industry who carry out large vol umes of titrations every day. As such, the irresolute pink that I observed in pasteurized milk is virtually belike 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 CreamTable 2 Titration of sour cream and yoghurt against 0.1M NaOHCream samplepH of sampleaverage pHmass ofsample (g)average mass of sample (g)initial burette reading (ml)final burette reading (ml)vol. of NaOH used (ml)average vol. of NaOH used* (ml)Sour Cream4.484.4910.0010.0050.0044.605.405.404.5010.0144.6039.205.404.509.9939.2033.805.40Yoghurt4.434.3810.019.9950.0037.9012.1012.304.3410.0037.9025.6012.304.389.9825.6013.3012.30Sour CreamAmount of NaOH used = (Average vol. of NaOH used) x NaOH= (5.40/1000)(0.105)= 5.67 x 10-4 molFrom (1), lactic acid NaOH is 11amount of lactic acid in 10.00g of sour cream = 5.67 x 10-4 mol cumulation of lactic acid in 10.00g of sour cream = (amount of lactic acid) x (molar mass of lactic acid)= (5.67 x 10-4)(90.08)= 0.0511gConcentration of lactic acid equivalent (in %w/w) in sour cream= (mass of lactic acid in 10.00g of sour cream) / (average mass of sour cream) x 100%= (0.0511) / (10.00) x 100%= 0.511% (w/w)YoghurtAmount of NaOH used = (Average vol. of NaOH used) x NaOH= (12.30/1000)(0.105)= 1.29 x 10-3 molFrom (1), lactic acid NaOH is 11amount of lactic acid in 9.99g of yoghurt = 1.29 x 10-3 molMass of lactic acid in 9.99g of yoghurt = (amount of lactic acid) x (molar mass of lactic acid)= (1.29 x 10-3)(90.08)= 0.116 gConcentration of lactic acid equivalent (in %w/w) in yoghurt= (mass of lactic acid in 9.99g of yoghurt) / (average mass of yoghurt) x 100%= (0.116) / (9.99) x 100%= 1.16% (w/w)From the results of this experiment in Table 2, we passel see that titratable acidity is not equal to pH, and it shares an inverse relationship with pH, where pH = -lgH+. 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 tear down than the fall 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 keep back a higher deprotonated H+. This is observed in Table 2 where the write down pH of yoghurt corresponds to a higher average volume of NaOH lacked to neutralize the lactic acid present.In addition, an otherwise reflexion is that yoghurt requires more than twice the volume of 0.1M NaOH to neutralize the lactic acid present as compared to sour cream even though yoghurt is lower in pH by 0.11. This is mainly attributed to the battlefront of probiotics added into yoghurt. As such, this government agency that more lactose in yoghurt is converted into lactic acid, resulting in the marked difference in average vol. 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 CurdTable 3 Titration of lemon curd against 0.105M NaOHSamplemass ofsample (g)average mass of sample (g)initial burette reading (ml)final burette reading (ml)vol. of NaOH used (ml)average vol. of NaOH used*(ml)Lemon Curd10.0010.0050.0029.2020.8020.3510.0029.208.9020.3010.0050.0029.6020.40*As 3 sets of titration were conducted for each sample in order to remedy the precision and reproducibility of the titration results, the average volume of NaOH was taken as the average of the 2 closest values of vol. of NaOH used in titration so as to be more precise.CNa+O-OCH2COHCO- Na+OCH2CO- Na+OCHOOCH2COHCOHOCH2COHO+ 3NaOH + 3H2O (2)Amount of NaOH used = (Average vol. of NaOH used) x NaOH= (20.35/1000)(0.105)= 2.14 x 10-3 molFrom (2), citric a cid NaOH is 13amount of citric acid in 10.00g of lemon curd = (amount of NaOH used) / 3= 7.13 x 10-4 mol milling machinery mass of citric acid = 6(12) + 8(1) + 7(16) = 192 g mol-1 mass of citric acid in 10.00g of lemon curd= (amount of citric acid) x (molar mass of citric acid)= (7.13 x 10-4)(192)= 0.137 gConcentration of citric acid equivalent (in % w/w) in lemon curd= (mass of citric acid in 10.00g of lemon curd) / (average mass of lemon curd) x 100%= (0.137) / (10.00) x 100%= 1.37% (w/w)As calculated above, the concentration of citric acid equivalent in lemon curd is 1.37% (w/w), which is well above the minimum standard of 0.33% (w/w) set by legislation in some parts of the world. Hence, it can be deduced that this sample of lemon curd has passed the quality falsify measure. Citric acid is used as the reference for quality control of lemon curd mainly because citric acid is present in the largest amount of money in lemons. Hence, measuring citric acid concentration present wil l 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 acidulent environment due to citric acid is not suitable for most bacteria to thrive.DiscussionThere are a few data-based procedures which can be improved on. 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 bank of human error. As such, a better method to solve the materialization of colour subjectivity is to use a colorimeter to determine an volume of pink as the end-point of titration, thus eliminating any inaccuracies that result from human error.Secondly, it was observed that the dilution of products of a more viscous consistency, such as sour cream and lemon curd, did not yield a homogenous consistency as compared with the mi lk samples and yoghurt. As such, the titrated NaOH may not have actually reacted with all the acid molecules as some acid molecules may be confine inside the granular particles. This can be overcome by vortexing the cream and water compartmentalization in a sealed round-bottom conelike flask to ensure a homogenous resolve is obtained, allowing us to obtain more accurate titration results.Thirdly, for runny liquid samples such as milk, there is a risk of vent due to splashing when the magnetic stirrer operates probably due to the large subject opening of the porcelain basin. Splashing can be overcome by using a cone-shaped 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 cur d, manifestly 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 load by the adding melamine. As such, additional qualitative methods can be employed, such as measuring the concentration of certain chemical substances more ridiculous to lemon, such as limonene.Turbidity test for pasteurized, UHT and sterilized milkMaterials ammonium ion ion sulfate powderPasteurized milkUHT milkSterilized milkMethod4.0g of ammonium sulphate, (NH4)2SO4, was dissolved in 20.0 ml of pasteurized milk. 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 set 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 DiscussionTable 4 Turbidity test resultsSample contemplationPasteurized milkA cloudy pale yellow effect with precipitation was observed.UHT milkA cloudy pale yellow ascendant was observed.Sterilized milkA clear pale yellow source 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. The turbidity test is first carried out by adding a denaturing agent, usually ammonium sulphate, (NH4)2SO4, to the milk sample. As NH4+ exhibits acidic properties, as shown in the assumeing equation,NH4+ + H2O NH3 + H3O+this addition of ammonium ions will bring about an increase in H+, resulting in the disruption of casein micelle structure. This causes casein proteins to go down and coagulate as they interact with the ammonium and sulphate ions.For those casein and milk whey proteins that are already denatured by heat treatment during processing, ammonium and sulphate ions will form interactions with the charged R-groups of the acidi c and basic amino group acid residues, causing them to precipitate out of the solution.These precipitate are obtained as the residue from filtration. The filtrate obtained contains mostly undenatured whey proteins and probably some unprecipitated protein molecules encapsulated in the casein micelle structure amidst a solution of ammonium sulphate and other soluble milk products such as lactose.Upon heat treatment in a 100oC water bath, the milk proteins denature and are thus exposed to ammonium sulphate. They undergo the same mode of action with ammonium sulphate as described above, resulting in the observed precipitation.Referring to AVA regulations, pasteurised milk is be to be milk that has been subjected to a single heat-treatment of 62.8 65.6oC for at least 30 min or 72 73.5oC for at least 15 s UHT milk is defined as milk that has been heated at a temperature of at least 135oC for at least 2 s sterilized milk is milk heated to 100oC long enough to sufficiently kill all micro bes.As such, sterilized milk will have all the casein and whey proteins fully denatured and free in the milk due to prolonged heating. Whereas UHT milk will have a slight concentration of undenatured proteins present due to a short high heat treatment. For pasteurized milk however, it will contain the highest concentration of undenatured proteins due to last-place heat treatment temperature. Hence, the experimental observation in Table 4 clearly fits the hypothesis. On a side note, the yellow pale solution observed is most likely due to the Maillard reaction between lactose in and amino compounds in milk.ConclusionTitratable acidity and the turbidity test for milk is but only 2 out of the many methods that the milk processing industry employs to ensure that the heat treatments have produced milk that are safe for human consumption.The main disadvantage that lies with milk treated with higher heat processes is the loss of flavour. The nutrients that are lost during heat are usually r eplaced (e.g. enriched milk) and hence this is less of a concern for milk. As such, it is the companys decision on whether to process milk with an emphasis on taste or shelf-life. Nevertheless, it is of period importance that the milk products remain well within the margin of natural rubber as stated by regulations.At the same time, regulatory bodies need to stay alert and play a part in ensuring that companies follow the safety guidelines, less an incident like the adulteration of dairy products by means of melamine addition may occur again.