Dairy Chemistry Practical Write Ups Chemical Quality Testing Essay 

Table of Contents

1. Volumetric analysis. Acetic acid content of vinegar

1.2 Introduction:

1.3 Aim

1.4 Health and safety

1.5 Materials and Methods:

1.5.1 Task 1: Standard solution making

1.5.2 Task 2: Titration

1.5.3 Task 3: Percentage determination of acetic acid in vinegar

1.6 Results and calculations

1.7 Discussion

1.8 References

2. Qualitative detection of carbohydrates using food samples.

2.1 Introduction

2.2 Aim

2.3 Health and safety

2.4 Materials and Methods:

2.5 Results:

2.6 Discussion:

2.7 References

3. Determination of fat in Wensleydale cheese using the Gerber Method.

3.1 Introduction

3.2 Aim

3.3 Health and safety

3.4 Materials and Methods:

3.5 Results of the Gerber method

3.6 Discussion

3.7 References

4. Determination of crude protein in milk by the Kjeldahl method

4.1 Introduction

4.2 Aim

4.3 Health and safety

4.4 Materials and Methods:

4.5 Calculations

4.6 Discussion

4.7 References

5. Chemical Quality Testing in Modern Dairy Business

References

1. Volumetric analysis. Acetic acid content of vinegar

1.2 Introduction:

Volumetric Analysis is a method in which the amount of a substance is determined by measuring the volume of a second substance that combines with the first in known proportions. Usually, it is used to determine the unknown concentration of known reactant. In this particular experiment, the Sodium Hydroxide (NaOH) molar concentration was known (0.1 M). In chemistry, molarity is a concentration unit, defined to be the number of moles of solute divided by the number of litres of solution (Helmenstine, 2016). In this volumetric analysis, Hydrochloric Acid (HCI) concentrations have not been given and were meant to be defined.

Volumetric analysis is often referred to as titration. The procedure of titration is used for determining the amount of acid (or base) in a solution by determining the volume of base (or acid) of a known concentration that will ultimately react to it. Several inorganic acids and bases and hundreds of organic compounds are sufficiently determined using this method(Csuros,1998).Vinegar is a common household item containing acetic acid as well as some other chemicals.  To determine the molarity of acetic acid in the vinegar sample it is necessary to calculate moles of NaOH which is required to neutralise the acetic acid in vinegar(SchoolWorkHelper, 2017).Legally the amount of acetic acid in the vinegar has to have minimum 4% of acetic acid (Fda.gov, 2017).

This analysis involves three primary processes: determining the concentration of HCl solution, determining the percentage of acetic acid in vinegar and the titrations performed. To determine the molarity of acetic acid in vinegar sample it is necessary to calculate moles of NaOH which is required to neutralise the acetic acid in vinegar.

1.3 Aim

The aim was to determine the molarity of the 0.1 M hydrochloric acid solution, also to determine the level of acetic acid in vinegar sample during titration process.

1.4 Health and safety

• It is the responsibility of everybody who is working in the laboratory to take reasonable care of themselves and those working around them.

• Personal Protective Equipment (PPE) should be worn  all the time in the laboratory such as:

• Safety glasses or goggles.
• Provided coat
• Hear net
• Gloves if needed.

Use of NaOH

Solid sodium hydroxide is corrosive, hygroscopic and caustic, therefore should not come into contact with exposed body parts, or metallic surfaces of the weighing balance. Though fairly corrosive when dilute, NaOH is a mild irritant that should be handled with care. In case aqueous NaOH spills on naked skin surfaces, proper rinsing with flowing water should be administered, while any spills on the working benches should be cleaned instantly. Preparation of aqueous NaOH solutions from its solid state should only be done by adding solid NaOH into the water in the conical flasks, and not the reverse.

Use of HCl

Though dilute, HCl is a highly corrosive acid that should be kept away from the human skin, metal surfaces and the working benches. In the case of any spills, the acid should be cleaned with plenty of water.

Use of Vinegar

Vinegar is an HC2H3O2 (acetic acid) solution, and so likely to corrode metal surfaces. At its native state, it is a mild irritant and should be kept away from coming into contact with human skin and anybody openings. Vinegar should be used in a place with free air circulation.

1.5 Materials and Methods:

1.5.1 Task 1: Standard solution making

• 2 g of solid sodium hydroxide (NaOH)was weighed out using laboratory scales and weight boat.
• 100 g of water measured using measuring cylinder
• Required amount of NaOH was transferred  into labelled beaker
• Water added to beaker with NaOH and stirred until NaOH completely dissolved
• Solution was transferred into 500 ml volumetric flask, and water added up to the mark
• Solution stirred through

1.5.2 Task 2: Titration

• 250 ml conical flask was rinsed with distilled water
• 25 ml of 0.1 M hydrochloric acid (HCl) solution was pipetted and added to conical flask
• 2-3 Drops of indicator phenolphthalein then   added in to solution
• The burette was properly  rinsed out  with 0.1 M NaOH
• 50 ml burette  filled with NaOH (0.1 M)
• NaOH was then used to titrate into the conical flask to reach the end point (Colour change).
• Colour appeared light pink.
• Readings were taken at the end point
• Repeated two –three times until three readings with no more than 0.1 ml were achieved 

1.5.3 Task 3: Percentage determination of acetic acid in vinegar 

• 10 ml of vinegar was pipetted into 100ml volumetric flask
• Water added until the mark
• 3 drops of phenolphthalein were added into vinegar solution
• A 50ml burette was filled with 0.1 M NaOH solution
• Titration started until the colour of resultant solution changed from colourless to pale pink.
• The final reading of burette was then recorded
• The procedure was repeated in order to achieve second reading, aiming for the two be within 0.2 ml of each other.

1.6 Results and calculations   

Table 1:  Amount of NaOH 0.1 M required for titrating 25 ml HCl solution of 0.1M

Three titrations appeared within 0.1 ml of each other as required. The following calculations were done to determine the molarity of the HCl:

 Molarity of HCl = Volume of NaOH x 0.1

25

Using the formula provided results appeared: Molarity of HCl=0.1202M

0.1 M of NaOH should neutralise0.1 M of HCl.

Table 2:  Amount of NaOH required to titrate 25 ml of vinegar

Titration was carried out until two readings within 0.2 ml were achieved, as per practical handout requirements:

25.2 x 25.23= 25.25 ml2

For the calculation of percentage of acetic acid, formula used below:

Percentage (w/v) acetic acid = volume of 0.1 M NaOH x 0.24

Which then appears that percentage of acetic acid in this particular case equals to 6.06%.

1.7 Discussion

Experiment one

The amounts of HCl were meant to be 0.1 M, and results appeared as 0.12 M, which is a little high. Therefore, there have been some errors in the procedure which may be influencing the results. The following discussion will explain possible errors which may appear in the process such as intrinsic error in the method, the end point is not identical every time, as the colour changes are not instant. The equivalence point is not always identical. There was possibility of using an excessive amount of NaOH this may happen due to the fact that titrant colour of the end point wasn’t identified correctly. Another possible reason for this particular mismatch could have been human error, during the amount of liquid filled up into the burette. Another possible reason could have been misreading the volume, for example, a parallax problem (when someone reads the volume looking at an angle), or error in counting unmarked graduation marks. When reading the volume on the burette scale it is not uncommon to read both upper and lower value in different lighting conditions, which can make a difference.

Experiment two

Expecting acetic acid in vinegar has to be at least 4% as that’s the legal requirement; the results appeared in the titration of vinegar where 6.06% which is a good result (Fda.gov, 2017). However, also there could be some errors in the true value as the same set-up was used as for experiment one. Vinegar that has a minimum of 4% acetic acid and a maximum of 8% conforms to legislation and can be legally sold in the UK. So if the value was correct at 6.06%, potentially there could be an opportunity for the company to save money by reducing the acetic acid content closer to the 4% minimum.This could be achieved by adding water, therefore,  reducing the amount of acid used. Acetic acid is obtained from first producing alcohol from malt and then using acetic acid bacteria to produce acetic acid. The traditional method is done in a barrel half filled with alcohol and takes a long time. The quicker way is to pump oxygen through the liquid. As the most expensive component in the vinegar is the acid, reducing the acid level would save a lot of money, as long as this did not affect the quality characteristics of the product, such as colour, flavour and aroma.

1.8 References

Csuros, M. (1998). Environmental sampling and analysis. 1st ed. Boca Raton: Springer.

Fda.gov. (2017). CPG Sec. 525.825 Vinegar, Definitions – Adulteration with Vinegar Eels. [online] Available at: https://www.fda.gov/iceci/compliancemanuals/compliancepolicyguidancemanual/ucm074471.htm [Accessed 25 Apr. 2017].

Helmenstine, A. (2016). Here’s What Molarity Means in Chemistry (Definition and Examples). [online] ThoughtCo. Available at: https://www.thoughtco.com/molarity-definition-in-chemistry-606376 [Accessed 25 Apr. 2017].

SchoolWorkHelper. (2017). Titration of Vinegar Lab Answers. [online] Available at: https://schoolworkhelper.net/titration-of-vinegar-lab-answers/ [Accessed 25 Apr. 2017].

2. Qualitative detection of carbohydrates using food samples. 

2.1 Introduction 

The qualitative and quantitative analysis is used to determine the composition of foods, beverages and their ingredient’s (Nielsen, 2003). Qualitative analysis in this particular test was used to determine the presence of carbohydrates in food samples. Carbohydrates in food can include anything from the simple monosaccharide – glucose to the very complex polysaccharide’s (Eliasson, 2006).  Carbohydrates can be reducing or non-reducing sugars; they can be detected through the use of Benedict test, Fehling’s test and Molisch test.  Benedict is a test which determines the presence of reducing sugars because of the way it has been prepared and carried out. It can be determined by colour changes – blue would stand as a control point, brick red would mean positive result (reducing sugars) (Anon, 2017). Fehling’s is another test to determine reducing sugars in food samples. In this test the presence of aldehydes but not ketones is detected by reduction of the deep blue solution of copper (II) to a red precipitate of insoluble copper oxide (Anon, 2017).  Molisch test is used to determine carbohydrates in general. This is based on the dehydration of the carbohydrate by sulfuric acid or hydrochloric acid to produce an aldehyde, which condenses with two molecules of phenol resulting in a red- or purple-coloured food samples which will indicate positive results (Guiwa, 2017)

2.2 Aim

The aim is to detect of carbohydrates and reducing sugars in food samples provided.

2.3 Health and safety  

• It is the responsibility of everybody who is working in the laboratory to take reasonable care of themselves and those working around them.

• Personal Protective Equipment (PPE) should be worn  all the time in the laboratory such as:

• Safety glasses or goggles.
• Provided coat
• Hear net
• Gloves if needed.

2.4 Materials and Methods:

Solid food was ground up in pestle and mortar before testing.  There were six different types of food samples placed in clean test tubes and this step been followed by adding 6 ml of water into test tubes. Tubes have been shacked in order to dissolve as much as possible carbohydrates. Then it has been divided into three aliquots for following tests.

1. For Benedict test, there were added 2 ml of Benedict reagent into samples and it has been placed in boiling water bath for five minutes. After five minutes it has been taken out and colour changes have been recorder.

1. The table below: Colour changes meaning:

(Biology Notes for IGCSE 2014)

2. For Fehling’s solution (equal volume of Fehling’s A and B solutions) 2 ml were added into test tubes and it has been placed into boiling water bath for three minutes. After required time samples had been taken out of water bath and results has been recorded. If solution changes colour from blue and forms a red or green precipitate then it means this test is a positive result.

3. For Molisch test 5 drops of reagent has been added to the test tubes and shaked well. Then 1 ml of concentrated sulphuric acid carefully added.  And results appeared has been recorded If results has a purple ring at the junction of the two layers, this counts as positive result.

2.5 Results:

1. The table below provides with results appeared during testing: