Here you can get contents about What is pH? and ph meter? and also some of its application in food processing industry

1. UNIT 4
pH meter and Application of
pH meter
Measurements and Instrumentation in Foods
Done By:
Nirenjana.V
Nivedya.P
II BE( Food Processing and Preservation
Technology)
Avinashilingam Institute of Home Science and
Higher Education for Women
Course Instructor: Dr. Hema Prabha

2. pH meter and Measurement of
pH
What is pH?
PH, quantitative measure of the acidity or basicity of aqueous or other
liquid solutions.
The measurement was originally used by the Danish biochemist to
represent the hydrogen ion concentration, expressed in equivalents per
litre, of an aqueous solution: pH = −log[H+]
Measurements and Instrumentation in Foods

3. What is pH?
The pH scale is logarithmic and inversely indicates the
concentration of hydrogen ions in the solution. This is because
the formula used to calculate pH approximates the negative of
the base 10 logarithm of the molar concentration of hydrogen
ions in the solution.
More precisely, pH is the negative of the base 10 logarithm of
the activity of the H+ ion.
At 25 °C, solutions with a pH less than 7 are acidic, and solutions
with a pH greater than 7 are basic. Solutions with a pH of 7 at
this temperature are neutral.
The neutral value of the pH depends on the temperature, being
lower than 7 if the temperature increases. The pH value can be
less than 0 for very strong acids, or greater than 14 for very
strong bases.
Measurements and Instrumentation in Foods

4. What is pH meter?
A pH meter is a scientific instrument that measures the hydrogen-ion
activity in water-based solutions, indicating its acidity or alkalinity
expressed as pH.
The pH meter measures the difference in electrical potential between a
pH electrode and a reference electrode, and so the pH meter is
sometimes referred to as a "potentiometric pH meter".
The difference in electrical potential relates to the acidity or pH of the
solution.
The pH meter is used in many applications ranging from laboratory
experimentation to quality control.
Measurements and Instrumentation in Foods

5. Building a pH meter
Measurements and Instrumentation in Foods
• Specialized manufacturing is required for the electrodes, and details of their design and
construction are typically trade secrets.
• However, with purchase of suitable electrodes, a standard multimeter can be used to
complete the construction of the pH meter.
• However, commercial suppliers offer voltmeter displays that simplify use, including
calibration and temperature compensation.

6. Why ph measurement is important in food
industry?
Measurements and Instrumentation in Foods
The lower the pH reading, the more acid the food. In order to preserve foods
with acidity, the regulation requires the pH to be 4.6 or below. At these levels,
toxins formed by the deadly organism causing botulism are inhibited. We refer
to foods which have readings greater than pH 4.6 as low-acid foods
How pH influence in preserving foods?
Acidifying (Acidified Foods)
Adding acid to a product with a initial pH greater than 4.6 in order to reduce it
below 4.6 is called acidifica- tion. This results in an acidified food. Low-acid
fruits and vegetables (those with a pH greater than 4.6) are often preserved by
acidification.

7. Methods of measuring pH in food industry
Measurements and Instrumentation in Foods
The methods for measuring pH fall roughly into the following
four categories:
• Indicator methods.
• Metal-electrode methods (including the hydrogen-electrode
method, quinhydron-electrode method and antimony-electrode
method)
• Glass-electrode methods.
• Semiconductor sensor methods.

8. Indicator methods.
Measurements and Instrumentation in Foods
Litmus paper is paper treated with a blue dye that turns red when in contact
with acids. The measurements are taken from the degree of color
the paper turns, the deeper the red, the greater is the degree of acidity.
Indicators and Titrations.As base is added the pH will increase, causing the
indicator to change to its basicform, causing a visible colour change. The point in
the titration at which the colour changes is known as the endpoint of the titration.

9. Metal Electrode method
Measurements and Instrumentation in Foods
Quinhydrone electrodes
• Quinhydrone electrodes are used in potentiometric titrations to overcome the problems that are faced
while using the hydrogen electrodes. It also allows the use of un-platinized metal electrodes.
• The quinhydrone electrode may be used to measure the hydrogen ion concentration (pH) of a solution
containing an acidic substance.
• However, it is not reliable above pH 8 and cannot be used with solutions that contain a strong oxidizing
or reducing agent.
Hydrogen electrode method
• A hydrogen electrode is made by adding platinum black to platinum wire or a platinum plate.
• It is immersed in the test solution and an electric charge is applied to the solution and the solution is saturated with
hydrogen gas.
The electrode potential is measured between platinum black electrode and silver chloride electrode.
Antimony-Electrode Method
• This method involves immersing the tip of a polished antimony rod into a test solution, also immersing a
reference electrode, and measuring pH from the difference in potential between them.
• This method was once widely used because the apparatus is sturdy and easy to handle.
• However, its application is now quite limited because results vary depending on the degree of polish of
the electrode, and reproducibility is low.

10. Glass electrode method
Measurements and Instrumentation in Foods
• The glass electrode method uses two electrodes, a glass
electrode and reference electrode, to determine the pH of a
solution by measuring the voltage (potential) between them.
• This method is the one most commonly used for pH
measurement, since the potential quickly reaches
equilibrium and shows good reproducibility, and because
the method can be used on various types of solutions, with
oxidizing or reducing substances having very little impact on
the result.
• The glass electrode method is widely used, not only in
industry but also in many other fields.

11. Calomel electrode
Measurements and Instrumentation in Foods
• PH meter, electric device used to measure hydrogen-ion activity (acidity
or alkalinity) in solution.
• Fundamentally, a pH meter consists of a voltmeter attached to a pH-
responsive electrode and a reference (unvarying) electrode.
• The pH-responsive electrode is usually glass, and the reference is usually
a mercury–mercurous chloride (calomel) electrode, although a silver–
silver chloride electrode is sometimes used.
• When the two electrodes are immersed in a solution, they act as a battery.
The glass electrode develops an electric potential (charge) that is directly
related to the hydrogen-ion activity in the solution

12. Measurements and Instrumentation in Foods
Ion selective electrodes
• Ion Selective Electrodes (ISE) are used to measure the
specific ion concentration in a solution usually in a real
time basis.
• The electrodes consist of a sensor that converts the
activity of an ion that is dissolved in a solution into an
electrical potential.
• Rather than the glass bulb the sensing part of the
electrode is made as an ion-specific membrane along
with an ion specific reference electrode.
• ISE are used in water treatment plants, manufacturing
facilities and laboratories where real time measurements
of specific ions are required for purification results, quality
control and solution analysis.

13. Measurements and Instrumentation in Foods
Silver chloride electrode
• A silver chloride electrode is a type of reference electrode, commonly
used in electrochemical measurements.
• the silver chloride electrode is the most commonly used reference
electrode for testing cathodic protection corrosion control systems in
sea water environments.
• Commercial reference electrodes consist of a plastic tube electrode
body.
• The electrode is a silver wire that is coated with a thin layer of silver
chloride, either physically by dipping the wire in molten silver chloride,
chemically by electroplating the wire in concentrated hydrochloric
acidor electrochemically by oxidising the silver in a chloride solution.
.

14. Semiconductor sensor methods
Measurements and Instrumentation in Foods
Direct, glass free measurement of pH in various liquids
is a well-established application of the ion sensitive field
effect transistor (ISFET).
Applying the same semiconductor technology for the
measurement of ion concentrations is now possible for
frequently analysed ions such as calcium, sodium,
potassium and nitrate.

15. Applications of pH meters in Foods
In Food Processors
Measurements and Instrumentation in Foods
◦ Ph meter is an important tool for food processors.
◦ Some food processors requires to check pH when making certain food products.
◦ Meters that measure pH level are used to insure that food products have an adequate
acidity level that will prevent the growth of food borne pathogens.
◦ Proper use of pH meter is a critical factor in establishing and maintaining safe food
products.

16. Measurements and Instrumentation in Foods
Measuring the pH of food products in steps:
◦ Calibration should be done frequently and calibrate electrode tests should be
recorded.
◦ Calibration should be done with known buffers at both 4.0 and 7.0 pH.
◦ Distilled water should be used to rinse pH meter electrodes.
◦ Food should be in liquid form or in puree form for measurement.
◦ Distilled water can be used to increase moisture level without changing pH.

17. Measurements and Instrumentation in Foods
Applications of pH.
◦ In the food industry, pH is principally used to govern the physical and
chemical reactions required to produce food and prevent the growth of
pathogens. This is exemplified while producing dairy and alcoholic
beverages as it involves fermentation.
◦ Useful yeasts and molds that chemically modify the input materials work
optimally at specific pHs. Further, pH values must be monitored to inhibit
the growth of pathogenic microorganisms that can cause food spoilage or
adversely impact the taste and quality of the final product. Thus, accurate
pH measurement equipment can ensure product quality and compliance
with food safety regulations.

18. Measurements and Instrumentation in Foods
Applications of ph meter in food industry
◦ To know the ph in buffer solution and buffer substances in food
◦ Maintaining perfect and accurate pH levels helps in keeping the milk from the turning sour.
◦ Ph meter helps in analyzing the exact ph value in food grade products and the ensuring high levels of safety and
quality.
◦ Ph meter is used to measure ph in canned foods .
Influence of pH in Bakery
Baked cakes were evaluated for pH, standing height as an index to volume, moisture, deformation, crust color, and crust
and crumb browning. Volume, color and browning were all significantly affected by pH adjustment. As acidity increased,
cakes had less volume and a gummy, pudding-like texture.

19. Measurements and Instrumentation in Foods
Ph meter measuring ph in canned foods

20. Measurements and Instrumentation in Foods
Applications of ph meter in food industry
◦ Monitoring of pH levels during the process of food production is a vital step in the production of high-
quality foods.
◦ Maintaining a prope r pH range is essential in many of the physical and chemical reactions that take place
during food processing.
◦ Incorrect pH levels during production of yogurt, for example, can lead to discoloration, excessive free whey,
and additional or insufficient tartness.
◦ In the manufacturing of jelly, pH levels can affect consistency.
◦ From wine and cheese to jelly and yogurt, maintaining the proper pH level is a critical factor in the production
of many food products.

21. Measurements and Instrumentation in Foods
Applications of ph meter in food industry
Proper pH level not only affects the look, taste, and quality of food products, but also maintaining a proper pH
level is a food safety issue.
A low pH reading of 4.6 will help prevent the growth of deadly bacteria such as botulism in canned or
preserved foods.
Accurate monitoring of pH during the production of these types of foods may be mandated by state

22. Measurements and Instrumentation in Foods
Applications of ph meter in food industry
Some food processors will need to check pH when making certain food products.
Proper use of a pH meter is important for food processors.

23. Measurements and Instrumentation in Foods
pH In dairy
◦ Several good examples of the importance of pH come
from the dairy industry.
◦ Most milk has a pH of around 6.8, making it very
slightly acidic.
◦ When the pH of milk is different than this, it might
indicate a problem with the cattle that produced it.
◦ Certain sorts of infection will make milk more acidic.
◦ The acidity of mik will also determine the quality of the
cheese that it goes on to make.

24. Measurements and Instrumentation in Foods
Cont...
◦ While the cream is being matured and milk is being soured, there is a
chance for harmful bacteria to multiply.
◦ This can be controlled by keeping the pH value closer to 5.
◦ A similar approach is taken during the manufacture of butter:a high pH,
closer to that of drinkable milk, will yield a sweeter butter; a lower pH
will generate sour butter.
◦ The pH is typically influenced through the addition of citric acid
extracts.
◦ Some dairy products, like yogurt, must be made especially acidic.

25. Measurements and Instrumentation in Foods
Ph in meat and fish
◦ pH is often used to assess the quality of meat when it is first brought into a
factory.
◦ Different cuts of meat contain muscular tissue and fat in different proportions.
◦ When the pH is too high, the quality of the meat will deteriorate – it won’t
become as dark, and some aroma will be lost.
◦ Certain sorts uf meat and fish, like fillet beefsteak, oysters and salmon are often
consumed raw.
◦ This makes screening for toxins especially important.
◦ In case of shellfish, this means several rounds of high-pressure washing.

26. Measurements and Instrumentation in Foods

27. Measurements and Instrumentation in Foods