Discussion Examples for Acidity Measurement of Soft Drinks | Citric Acid Equivalence and Titration Errors

What Is Acidity Measurement of Soft Drinks?

Acidity measurement of soft drinks is an analysis in which the acidic components contained in beverages are quantified to evaluate sourness and quality.
The sourness of beverages is caused by organic acids such as citric acid and malic acid, carbonic acid in carbonated beverages, phosphoric acid contained in cola beverages, and other acidic components.
These acidic components affect not only taste but also preservability and pH.

In acidity measurement, the acids in the beverage are neutralized with a NaOH standard solution, and the amount of acidic components is calculated from the amount of NaOH consumed up to the endpoint.
Because beverages contain multiple acids, the measurement result may be expressed not as the amount of a specific acid itself but as acidity converted to citric acid or another representative acid.

Main Items to Include in the Results

In the results of acidity measurement of soft drinks, organize the type of beverage, sample amount, dilution factor, presence or absence of degassing, concentration of the NaOH standard solution, titration volume, indicator, endpoint pH, acidity, citric-acid-equivalent value, and other information.
Because soft drinks may be colored or carbonated, pretreatment conditions are also important.

Main Items to Include in the Results

• Type of sample beverage
• Presence or absence of carbonation
• Sample amount
• Dilution factor
• Presence or absence of degassing treatment
• Presence or absence of heating treatment
• Concentration of the NaOH standard solution
• NaOH titration volume
• Type of indicator
• Whether a pH meter was used
• Color change at the endpoint or endpoint pH
• Blank value
• Acidity expressed as citric acid equivalents
• Average value from multiple measurements
• Variation in titration values
• Comparison with food labels and among beverages
• Causes of error and points for improvement

Reference Experimental Values and Calculation Examples for Acidity Measurement of Soft Drinks

Here, the process of neutralizing acids in soft drinks with a sodium hydroxide standard solution and expressing the result as acidity in citric acid equivalents is organized using reference experimental values.

Soft drinks contain acidic components such as citric acid, malic acid, phosphoric acid, and carbonic acid.
In neutralization titration, these acids are titrated together, and the acidity may be expressed by converting the total amount to citric acid, a representative acid.
However, dissolved carbon dioxide in carbonated beverages, beverage color, endpoint determination, and whether degassing is performed affect the measured value.

Reference Experimental Conditions

Concept of Neutralization Reaction and Citric Acid Equivalence

Citric acid is a triprotic acid, and 1 mol of citric acid reacts with 3 mol of NaOH.
Therefore, when determining the equivalent amount of citric acid from the amount of NaOH, the amount of NaOH is divided by 3.

Titration Results for Different Soft Drinks

Reference examples are shown for titrating 10.00 mL of each beverage with 0.100 mol/L NaOH.
Carbonated beverages are treated as samples after sufficient shaking to remove carbon dioxide.

Example Calculation of the Amount of NaOH

First, the amount of NaOH used in the titration is determined.

Amount of NaOH = NaOH concentration × NaOH titration volume

For the lemon-flavored beverage, the NaOH concentration is 0.100 mol/L and the titration volume is 7.85 mL = 0.00785 L.

Amount of NaOH = 0.100 mol/L × 0.00785 L = 7.85 × 10−4 mol

The amount of acid corresponding to this amount of NaOH is then determined as citric acid equivalents.

Example Calculation of Citric Acid Equivalent

Because citric acid is a triprotic acid, the amount of citric acid is one-third of the amount of NaOH.

Amount of citric acid = 7.85 × 10−4 mol ÷ 3 = 2.62 × 10−4 mol

Using 192.1 g/mol as the molar mass of citric acid, the mass expressed as citric acid equivalents is determined.

Citric acid equivalent = 2.62 × 10−4 mol × 192.1 g/mol = 0.0503 g

Therefore, the acid in 10.00 mL of the lemon-flavored beverage is determined to be 0.0503 g in citric acid equivalents.

Example Conversion to Acidity

Because the citric acid equivalent in 10.00 mL of sample has been determined, it is multiplied by 10 to express the acidity per 100 mL.

Acidity (g/100 mL) = Citric acid equivalent in 10.00 mL × 10

For the lemon-flavored beverage, the citric acid equivalent in 10.00 mL is 0.0503 g.

Acidity = 0.0503 × 10 = 0.503 g/100 mL

Therefore, in this reference example, the acidity of the lemon-flavored beverage is 0.503 g/100 mL.

Comparison Before and After Degassing Carbonated Beverages

Carbonated beverages contain dissolved carbon dioxide, which shows acidity as carbonic acid in water.
If titration is performed without sufficient degassing, carbonic acid is also neutralized and the acidity may be overestimated.

In this reference example, the acidity without degassing was 0.375 g/100 mL, whereas it was 0.317 g/100 mL after sufficient degassing.
To reduce the effect of carbonic acid, degassing before titration is important.

Comparison of Endpoint Determination in Colored Beverages

In dark-colored beverages, the pale red color of phenolphthalein is difficult to see, making endpoint determination more prone to error.
Here, a tea beverage is compared when titrated directly and when titrated after dilution.

In dark-colored samples, visual endpoint determination tends to shift.
Dilution or use of a pH meter may reduce variation in endpoint determination.

Checking Reproducibility by Repeated Measurements

The same sample is titrated multiple times to check the variation in titration volume.
Here, an example is shown in which an orange juice beverage was measured three times.

The three titration volumes were within the range of 6.19 to 6.22 mL and agreed relatively well.
Standardizing endpoint determination and burette reading makes it easier to obtain reproducible measurements.

Differences in Converted Values Depending on the Type of Acid

Soft drinks may contain not only citric acid but also malic acid, phosphoric acid, lactic acid, and other acids.
When the result is expressed as citric acid equivalents as in this experiment, it does not directly indicate the actual type of acid present.

Acidity expressed as citric acid equivalents is a value that combines the acidic components in the beverage and expresses them as citric acid.
Another analytical method is necessary to determine the actual types of acids in detail.

Example Comparison of Sugar Content and Acidity

The taste of soft drinks is greatly affected not only by acidity but also by sugar content.
Even when acidity is the same, sourness may be perceived as weaker when the sugar content is high.

The sugar-acid ratio is the value obtained by dividing sugar content by acidity.
The larger the sugar-acid ratio, the stronger the sweetness is relative to sourness, and the less noticeable the sourness tends to be.

Example Calculation of the Sugar-Acid Ratio

If the sugar content of an orange juice beverage is 11.5 °Brix and the acidity is 0.397 g/100 mL, the sugar-acid ratio is calculated as follows.

Sugar-acid ratio = Sugar content ÷ Acidity

Sugar-acid ratio = 11.5 ÷ 0.397 = 29.0

This value can be used as a guide for comparing the balance between sourness and sweetness.

Example of How to Write the Results

A 10.00 mL portion of each soft drink was titrated with 0.100 mol/L NaOH standard solution, and the acidity expressed as citric acid equivalents was determined.
For the lemon-flavored beverage, the NaOH titration volume was 7.85 mL, the citric acid equivalent was 0.0503 g/10.00 mL, and the acidity was 0.503 g/100 mL.
The acidity was 0.397 g/100 mL for the orange juice beverage and 0.199 g/100 mL for the sports drink, showing differences in acidity depending on the type of beverage.

In the carbonated beverage, the acidity was 0.375 g/100 mL without degassing, whereas it was 0.317 g/100 mL after sufficient degassing.
This suggests that dissolved carbon dioxide increases the titration value and may cause acidity to be overestimated.

In addition, in dark-colored samples such as tea beverages, the phenolphthalein endpoint was difficult to observe.
When a pH meter was used, the acidity was 0.118 g/100 mL, which was close to the value obtained after dilution.
In dark-colored samples, the method used to determine the endpoint may affect the measured value.

Points for Connecting the Results to the Discussion

In acidity measurement of soft drinks, it is useful not only to calculate acidity from the titration volume but also to discuss the beverage components, carbonation, coloration, and the relationship with sugar content.

• Has the amount of acid been correctly calculated from the NaOH concentration and titration volume?
• Has the fact that citric acid is triprotic been correctly reflected in the calculation?
• Has the amount in 10 mL been correctly converted to acidity per 100 mL?
• For carbonated beverages, can it be explained that insufficient degassing may cause acidity to be overestimated?
• For dark-colored beverages, can the difficulty of determining the indicator endpoint be discussed?
• Can it be explained that acidity expressed as citric acid equivalents does not directly indicate the actual type of acid present?
• Can the relationship between sugar content and acidity be compared and related to the perception of taste?
• Can burette reading, sample amount, NaOH concentration, and overtitration beyond the endpoint be discussed as sources of error?

Example Discussion

In this experiment, the acids in soft drinks were neutralized with a 0.100 mol/L NaOH standard solution and determined as acidity in citric acid equivalents.
The lemon-flavored beverage had an acidity of 0.503 g/100 mL, the highest value among the samples measured in this experiment.
In contrast, the acidity of the sports drink was 0.199 g/100 mL and that of the tea beverage was 0.118 g/100 mL, confirming that the amount of acidic components differs depending on the type of beverage.

The titration volume for the lemon-flavored beverage was 7.85 mL.
When the amount of NaOH was calculated and the fact that citric acid is a triprotic acid was taken into account, the citric acid equivalent in 10.00 mL of sample was 0.0503 g.
When converted to 100 mL, the acidity was 0.503 g/100 mL, showing that beverages requiring larger titration volumes also have higher acidity.

In carbonated beverages, the acidity was measured as higher under conditions without degassing.
This was considered to result from dissolved carbon dioxide existing as carbonic acid in the beverage and being neutralized by NaOH.
Because the titration volume decreased after sufficient degassing, it is necessary to standardize the degassing conditions when comparing the acidity of carbonated beverages.

In addition, in dark-colored beverages, endpoint determination using an indicator is difficult and overtitration may occur.
In the tea beverage, the endpoint was easier to determine when the sample was diluted or when a pH meter was used than when it was titrated directly.
This suggests that the method used to determine the endpoint in colored samples affects the measurement error.

When acidity and sugar content were compared, beverages with higher acidity did not necessarily taste more strongly sour.
In beverages with high sugar content, sourness is softened by sweetness, so the impression of taste is affected not only by acidity but also by the sugar-acid ratio.
Therefore, when discussing the taste of soft drinks, it is important to consider acidity, sugar content, and the sugar-acid ratio together.

Summary

In acidity measurement of soft drinks, the amount of acid is determined by neutralization titration with a NaOH standard solution and expressed as acidity in citric acid equivalents.
Because citric acid is a triprotic acid, the amount of NaOH is divided by 3 to convert it to the amount of citric acid.

In this reference example, the lemon-flavored beverage showed high acidity, while the tea beverage showed a low value.
In addition, the presence or absence of degassing affected the measured value for carbonated beverages, while endpoint determination affected the value for colored beverages.
In a report, it is useful to discuss titration calculations, citric acid equivalence, the effects of carbonic acid, endpoint errors caused by coloration, and the relationship with sugar content in relation to one another.

Principle of Neutralization Titration

Neutralization titration is a method for determining the amount of an acid or base using the reaction in which an acid and a base react to form water and a salt.
In acidity measurement of soft drinks, acidic components in the beverage are neutralized with a NaOH standard solution.
If the NaOH concentration and titration volume are known, the amount of acid can be determined from the amount of base required for neutralization.

However, the acids contained in soft drinks are not necessarily of only one type.
Citric acid, malic acid, phosphoric acid, carbonic acid, and other acids differ in the number of hydrogen ions that can be neutralized per molecule and in their titration curves.
Therefore, in experiments, the measured total acid amount may be expressed by converting it to citric acid.

What Is Citric Acid Equivalence?

Citric acid equivalence is a method of expressing the various acidic components contained in a beverage by calculating them all as citric acid.
Soft drinks may actually contain acids other than citric acid, but their acidity may be converted to a citric acid amount to make comparison easier.
This makes it easier to compare the strength of sourness and the amount of acidic components among beverages.

Citric acid is a triprotic acid and has three acidic hydrogens per molecule, so the reaction ratio with NaOH must be taken into account in the calculation.
However, the citric acid equivalent does not mean “the actual amount of citric acid alone contained in the beverage.”
It is simply a value expressing the acidity as citric acid.

Citric acid H3Cit + 3NaOH → Na3Cit + 3H2O

How to Calculate Acidity in Citric Acid Equivalents

To determine acidity in citric acid equivalents, first calculate the amount of NaOH from the concentration and titration volume of the NaOH standard solution.
Next, use the fact that 1 mol of citric acid reacts with 3 mol of NaOH to convert this to the amount of citric acid.
Then, use the molar mass of citric acid to convert the amount of substance to mass and calculate the acidity as a proportion of the sample amount.

If the beverage was diluted before measurement, the dilution factor must be correctly reflected.
It is also important to clearly state the units used for acidity, such as per 100 mL, per 100 g, or mass percent.
Without consistent units, comparisons among beverages or with labeled values cannot be made.

Amount of NaOH = NaOH concentration × NaOH titration volume

Amount of citric acid = Amount of NaOH ÷ 3

Mass of citric acid = Amount of citric acid × Molar mass of citric acid

Main Acids Contained in Soft Drinks

Soft drinks contain various acidic components to adjust taste and preservability.
Citric acid and malic acid may be involved in fruit-juice beverages, lactic acid in lactic-acid-bacteria beverages, phosphoric acid in cola beverages, and carbonic acid in carbonated beverages.
These acids affect the sourness and pH of the beverage.

In neutralization titration, these acidic components react together with NaOH.
Therefore, the acidity determined by titration reflects the total amount of titratable acids in the beverage rather than only a specific acid.
Citric acid equivalence expresses this total acid amount as citric acid.

Importance of Degassing Carbonated Beverages

Carbonated beverages contain dissolved carbon dioxide, which shows acidity as carbonic acid in water.
Therefore, if a carbonated beverage is titrated directly, not only acids such as citric acid and phosphoric acid but also carbonic acid consumes NaOH.
This effect may cause the acidity to be determined as higher.

If the effect of carbonic acid is to be reduced, degassing is performed before measurement.
Methods such as stirring, ultrasonication, heating, and reduced pressure may be used for degassing, but the method specified in the laboratory manual should be followed.
If degassing is insufficient, acidity originating from carbonic acid remains and affects the measured value.

Colored Beverages and Endpoint Determination

Some soft drinks are colored by fruit juice, caramel coloring, colorants, and other substances.
In titration using an indicator, the color of the sample itself may make it difficult to see the color change at the endpoint.
In particular, the pale red color of phenolphthalein is difficult to judge in red or brown beverages.

When the endpoint is difficult to observe, using a pH meter to judge the endpoint pH is effective.
In addition, diluting the sample may lighten its color and make the indicator change easier to observe.
However, when the sample is diluted, the dilution factor must be reflected in the calculation.

Discussion of the Phenolphthalein Indicator

Phenolphthalein indicator may be used in neutralization titration.
Phenolphthalein is colorless under acidic conditions and shows a pale red color under weakly basic conditions.
When an acidic sample such as a soft drink is titrated with NaOH, the pale red color begins to persist near the endpoint.

However, soft drinks are often colored, making determination of the pale red color difficult.
In addition, if titration is continued until the color becomes distinctly dark red after passing the endpoint, the amount of NaOH becomes excessive and the acidity is overestimated.
The endpoint is judged as the first point at which a pale color persists for a certain period.

Discussion When Using a pH Meter

A pH meter allows the endpoint to be determined from changes in pH without relying on the color change of an indicator.
In colored or turbid beverages, using a pH meter can reduce subjective errors in endpoint determination.
In addition, if a titration curve is prepared, the endpoint can be estimated from the sharp change in pH.

However, a pH meter also has sources of error.
Insufficient calibration, contamination of the electrode, insufficient temperature compensation, and reading the value before it stabilizes can affect the result.
When using a pH meter for acidity measurement, calibration with standard solutions and electrode cleaning are also important.

Concentration Error of the NaOH Standard Solution

In acidity measurement, the concentration of the NaOH standard solution serves as the basis for the calculation.
If the NaOH concentration is inaccurate, the calculated acidity is systematically shifted.
Sodium hydroxide readily absorbs CO2 from the air, and its concentration may change during storage.

Therefore, it may be desirable to standardize the NaOH standard solution before use.
Depending on whether the concentration of the standard solution is treated as higher or lower than the actual value, the acidity expressed as citric acid equivalents is also calculated as higher or lower.
Management of the standard solution is directly related to the reliability of titrimetric analysis.

Discussion When Acidity Is High

When acidity is high, the beverage is considered to contain a large amount of titratable acidic components.
Fruit-juice beverages, sports drinks, and strongly sour beverages may contain large amounts of citric acid, malic acid, and other acids, resulting in larger NaOH titration volumes.
In cola beverages, phosphoric acid may contribute, while in carbonated beverages, the effect of carbonic acid must also be considered.

However, a high measured acidity does not necessarily result only from a large amount of actual acid components.
Titration beyond the endpoint, insufficient degassing of carbonated beverages, errors in NaOH concentration, failure to detect the endpoint because of coloration, and mistakes in the dilution factor may also cause the acidity to be determined as high.

Discussion When Acidity Is Low

When acidity is low, the beverage is considered to contain a small amount of acidic components.
Beverages close to water, mildly sour beverages, and beverages dominated by sweetness may require only a small amount of NaOH for titration.
Beverages with low acidity may be perceived as less sour.

However, if acidity is determined as low, possible errors include stopping titration before the endpoint, excessive dilution of the sample, failure to reflect the dilution factor in the calculation, incorrect handling of the NaOH concentration, and collecting too little sample.
If the measured value is lower than expected, the operation and calculation should be reviewed.

Relationship Between Sweetness and Acidity

The taste of soft drinks is not determined by acidity alone.
In beverages containing large amounts of sugars or sweeteners, sourness may be perceived as mild even when the acidity is high.
Conversely, in beverages with little sugar, the same acidity may be perceived as more strongly sour.

In other words, acidity indicates the chemical amount of acidic components, but perceived sourness is also affected by sugar content, flavorings, carbonation, temperature, and other factors.
In a report, it is useful not to simply equate acidity with the sensation of sourness but to discuss that other components also affect the perception of sour taste.

Effects of Carbonation and Related Errors

Dissolved CO2 affects the measured value in carbonated beverages.
CO2 dissolves in water to form carbonic acid and is neutralized by NaOH.
Therefore, if a beverage is titrated while it still contains carbonation, carbonic acid consumes NaOH in addition to acids such as citric acid and phosphoric acid, and the acidity may be determined as too high.

If degassing is insufficient, the amount of remaining CO2 differs among samples and the variation in titration values increases.
When comparing carbonated beverages, the degassing conditions must be standardized and it must be clearly stated how the effect of carbonic acid was handled.

Effect of the Dilution Factor

When the acidity of a soft drink is high or its color is dark, the sample may be diluted before titration to make measurement easier.
Dilution can adjust the NaOH titration volume to an appropriate range and may also make the endpoint color easier to observe.
However, when the sample is diluted, the result must be converted back to the acidity in the original sample.

Forgetting to apply the dilution factor causes the acidity to be greatly underestimated.
Conversely, applying the dilution factor twice causes the acidity to be overestimated.
It is important to dilute accurately using a volumetric flask or volumetric pipette and clearly write the calculation process.

Error When the Endpoint Is Exceeded

If too much NaOH is added beyond the endpoint, the NaOH titration volume becomes larger than the actual value.
As a result, the acidity expressed as citric acid equivalents is calculated as too high.
When an indicator is used, continuing titration until the color becomes clearly dark rather than stopping at the point where a pale color persists may result in overtitration.

Near the endpoint, NaOH is added one drop at a time and the flask is thoroughly mixed while the change is observed.
Even when a pH meter is used, small amounts must be added so that the sharp change in pH is not missed.

Error When Titration Is Stopped Before the Endpoint

If titration is stopped before the endpoint, the NaOH titration volume is underestimated and the acidity is determined as low.
Even if the color appears to change temporarily, the endpoint has not yet been reached if the color disappears when the flask is mixed.
Insufficient mixing may locally create a basic region and cause the endpoint to be misidentified.

To avoid the error of stopping before the endpoint, the solution is thoroughly mixed during titration and the persistence of the color or stability of the pH is confirmed.
Particularly for samples with high acidity, neutralization may take time, so operations near the endpoint must be performed carefully.

Discussion When Titration Values Vary

When repeated titrations give varying values, possible causes include individual differences in endpoint determination, NaOH addition rate, burette-reading errors, sample-aliquoting errors, insufficient mixing of diluted solutions, and insufficient degassing of carbonated beverages.
In soft drinks, color and carbonation may make endpoint determination more difficult than in ordinary colorless solutions.

When the variation is large, it is important to discuss not only the average value but also what may have caused the variation.
Repeating measurements under the same conditions until close titration values are obtained can improve the reliability of the results.

Causes of Error in Acidity Measurement of Soft Drinks

Causes of error in acidity measurement of soft drinks include concentration errors in the NaOH standard solution, endpoint-determination errors, burette-reading errors, sample-aliquoting errors, mistakes in the dilution factor, insufficient degassing of carbonation, difficulty observing the endpoint because of coloration, and insufficient calibration of the pH meter.
The way these errors appear differs depending on the type of beverage.

For carbonated beverages, the effect of CO2 is important; for colored beverages, endpoint-color determination is important; and for fruit-juice beverages, the presence of multiple organic acids is an important point for discussion.
Organizing the factors that increase and decrease the measured value makes it easier to write the report discussion.

When the Results Can Be Considered Good

Acidity-measurement results for soft drinks can be considered good when repeated titration volumes are close to one another, the endpoint is clear, and the dilution factor and degassing conditions have been handled correctly.
In addition, if the obtained acidity does not greatly contradict the type of beverage or its taste characteristics, the result is easier to consider reasonable.

For example, if strongly sour fruit-juice beverages show high acidity and mildly sour beverages show low acidity, the results agree with the characteristics of the beverages.
For carbonated beverages, the change in acidity before and after degassing can also be used as material for discussion.

Example Discussion When the Experiment Did Not Go Well

When acidity measurement does not go well, possible causes can be considered from results such as varying titration values, difficulty observing the endpoint, acidity being higher or lower than expected, unstable values for carbonated beverages, or trends among beverages that are difficult to explain.
It is useful to organize the causes according to sample treatment, degassing, dilution, standard solution, endpoint determination, and calculation.

How to Write Points for Improvement

In a discussion of acidity measurement of soft drinks, writing not only the causes of error but also points for improvement makes the report easier to organize.
Points for improvement can be divided into sample treatment, standard solutions, titration operation, and calculation and analysis.

Improvements to Sample Treatment

• Sufficiently degas carbonated beverages
• Standardize the degassing conditions for all samples
• Accurately aliquot the sample
• Dilute when necessary
• Thoroughly mix the solution after dilution
• Consider using a pH meter when the sample is strongly colored

Improvements to Standard Solutions and Titration Operations

• Standardize the NaOH standard solution
• Store the NaOH standard solution in a tightly sealed container
• Remove air bubbles from the burette
• Read the scale at eye level
• Add the titrant one drop at a time near the endpoint
• Thoroughly mix the flask
• Perform multiple measurements and calculate the average value

Improvements to Calculation and Analysis

• Confirm the reaction ratio between citric acid and NaOH
• Correctly reflect the dilution factor
• Clearly state the units of acidity
• Explain the meaning of the citric acid equivalent
• Consider the effects of carbonic acid and multiple acidic components
• Compare the result with the type and taste characteristics of the beverage
• Check the variation in titration values

Difference Between a Superficial Discussion and a Good Discussion

In a discussion of acidity measurement of soft drinks, simply writing that “the acidity was high” or “the sample was titrated with NaOH” results in a superficial discussion.
A good discussion relates the meaning of citric acid equivalence, neutralization titration, the effects of carbonation and coloration, endpoint determination, and causes of error.

Examples of Expressions That Can Be Used in Reports

The following expressions can be used when writing the results and discussion of acidity measurement of soft drinks.
Adjust the necessary parts according to your own experimental results.

• The acidity of a soft drink is an indicator representing the amount of titratable acidic components contained in the beverage.
• In neutralization titration, acidity can be determined from the amount of NaOH that reacts with the acidic components.
• Citric acid equivalence is a value expressing the total amount of acid in the beverage as citric acid.
• Acidity expressed as citric acid equivalents does not necessarily represent the actual amount of citric acid contained.
• The larger the NaOH titration volume, the greater the amount of acidic components considered to be present in the sample.
• In carbonated beverages, residual CO2 may consume NaOH and cause acidity to be overestimated.
• In colored beverages, the endpoint color of the indicator may become difficult to distinguish.
• Titrating beyond the endpoint causes acidity to be overestimated.
• Stopping titration before the endpoint causes acidity to be underestimated.
• For diluted samples, the dilution factor must be correctly reflected in the calculation.

Points to Check When Discussing Acidity Measurement of Soft Drinks

Checking the following points before writing the report makes the discussion easier to write.

• Is it explained what acidity represents?
• Is the principle of neutralization titration described?
• Is the meaning of citric acid equivalence explained?
• Is the reaction ratio between citric acid and NaOH understood?
• Are the types of acids contained in soft drinks considered?
• Is the effect of degassing carbonated beverages considered?
• Is the difficulty of endpoint determination caused by coloration considered?
• If a pH meter was used, is calibration considered?
• Are concentration errors in the NaOH standard solution considered?
• Is the dilution factor handled correctly?
• Is the variation in titration values checked?
• Do the points for improvement correspond to the causes of error?

Summary

Acidity measurement of soft drinks is an experiment in which the acidic components contained in a beverage are neutralized with a NaOH standard solution and expressed as acidity in citric acid equivalents.
Soft drinks may contain multiple acids such as citric acid, malic acid, lactic acid, phosphoric acid, and carbonic acid.
Therefore, the citric acid equivalent must be interpreted not as the actual amount of citric acid itself but as the total amount of acid expressed as citric acid.

Beverages with high acidity require larger NaOH titration volumes and are considered to contain larger amounts of acidic components.
However, in carbonated beverages, dissolved CO2 affects the result, in colored beverages endpoint determination affects the result, and in fruit-juice beverages multiple organic acids affect the result.
In addition, the concentration of the NaOH standard solution, dilution factor, endpoint determination, and calibration of the pH meter are also important sources of error.

In a report, rather than simply writing that “the acidity was high or low,” organize and discuss the principle of neutralization titration, the meaning of citric acid equivalence, the effects of carbonation and coloration, titration errors, dilution factors, and points for improvement.
In acidity measurement of soft drinks, it is important to understand the connection between food taste and quality and titration procedures in analytical chemistry.