physical properties of food and rheology

1. BANASTHALI VIDYAPITH
Department of Bioscience & Biotechnology
M.Tech. Biotechnology II Semester
BT 512: Food Biotechnology
Topic: Physical Properties of Food- RHEOLOGY
Submitted to: Submitted By:
Dr. Pracheta Sanmi Sharma
Roll No: 2251096
ID: LSMT22004

2. Content
1. Physical Properties of Food.
2. Properties of Fluid Food [RHEOLOGY]
3. References.

3. Physical Properties of Food
• Physical characteristics of raw, unprocessed, as well as processed food
materials include
1. Particle size.
2. Shape.
3. Bulk density and True density.
4. Porosity.
5. Surface area.

4. Particle size
• Important physical attributes used in terms of screening foreign materials
• Used in evaluating the quality of food.
• METHODS:
1. Project area method: It includes calculation of major, minor and intermediate diameter.

5. 2. Micrometer Measurement: Here dimensions of the material are
measured by using a micrometer and vernier caliper.

6. Shape
• Shape effect grade is given to fruit or raw products.
• Commonly recognized expected shapes of fruit or vegetable will be
categorized under the highest grade and vice versa.
• Parameter used to define shape: roundness and sphericity.

7. True Density (ρt)
• True density for solid: Ratio of
the total mass or weight to the
volume of material
• Volume of fruit= new level of
water-original water level (Y)
• Mass of fruit= x
• Density= mass/volume
= x/y

8. • True Density for Powder: Ratio of
the total weight of powder to the
true volume of the powder.
• Weight of empty bottle= W1
• Weight of bottle+ powder= W2
• Weight of powder (X)= W2-W1
• Weight of bottle + water + powder=W3
• True volume of powder (Y)= W3-W2
• True density (ρt)= X/Y
Pycnometer

9. Bulk Density (ρb)
• Bulk Density= weight of Powder/
Bulk volume of powder
Weight of Powder= X
The volume of Powder= Y
Bulk Density (ρb)= X/Y

10. Porosity and Surface Area method
•Porosity: Defined as a percentage of the volume of intergrain
space to the total volume of grain bulk.
Porosity(ε)= {1- ρb / ρt } x 100
•Surface Area: This method is used to estimate the amount of
wax applied to the fruit, and the amount of packaging film to wrap
the fruit.
• It uses the Graphical method same as the Project area method, used
under particle size.

11. Properties of Fluid Food [RHEOLOGY]
• The rheological properties of liquid food are based on flow and
deformation responses when subjected to stress.
• Factors that determine the properties of liquid food are shear rate
and shear stress.
• Based on the rheological properties all liquids food can be classified
into two:
1. Newtonian fluids.
2. Non-Newtonian fluids.

12. Newtonian fluid
• A Newtonian fluid is a fluid whose stress versus strain rate curve is
linear and passes through the origin. The constant of proportionality is
known as viscosity.

13. Non-Newtonian Fluid
• A non-Newtonian fluid is a fluid whose flow properties are not
described by a single constant value of viscosity, i.e. the shear rate-
shear stress plot is not linear or the plot does not begin at the origin.

14. Rheology in food having viscous nature
• Water, Juice, and edible oil show a linear relationship between shear
stress and shear rate.

15. Rheology in food having viscous and plastic
nature
• Food having viscous nature show Shear thinning behavior, i.e, shear
rate and viscosity are inversely proportional to each other.
• Example: Tomato ketchup, soups, mustard sauces, mayonnaise, etc.
• Here, when the shear rate is increased by applying shear stress then
viscosity will decrease and make viscous food easy to flow.

16. Rheology in food having shear thickening
behaviour
• Here shear rate and viscosity are directly proportional to each other.
i.e, when shear rate increase, viscosity will also increase i.e, Reverse
of shear thinning.
• Known as Dilatant Liquid.
• Example: partially gelatinized starch, corn starch, cream, etc.

17. References
1. He, Jiayan, Gadi V.P. Reddy, Mengdi Liu, and Peijian Shi. “A General Formula for Calculating
Surface Area of the Similarly Shaped Leaves: Evidence from Six Magnoliaceae Species.” Global
Ecology and Conservation 23 (2020). https://doi.org/10.1016/j.gecco.2020.e01129.
2. “Mango.” Wikipedia. Wikimedia Foundation, December 26, 2022.
https://en.wikipedia.org/wiki/Mango.
3. “Istock.” iStock. https://www.istockphoto.com/photos/deformed-banana.
4. “R/Mildlyinteresting - Siamese Mango.” reddit.
https://www.reddit.com/r/mildlyinteresting/comments/if9r2v/siamese_mango/.
5. “Measurement of Wood Volume Using Water Displacement Method.”
https://www.researchgate.net/figure/Measurement-of-wood-volume-using-water-
displacement-method_fig9_322593979.
6. “Food Science and Technology Books.” Fundamentals of Food Biotechnology, 2014, 519–20.
https://doi.org/10.1002/9781118384947.oth01.
7. “Physical Properties of Food Materials - Microsoft.”

18. THANK YOU