Cryogenic Grinding is the technique of Pulverizing at sub-zero temperatures (-17.78°C) to minimize the loss of essential oils.Cryogenic grinding technology can efficiently grind most tough materials and can also facilitate cryogenic recycling of tough composite materials and multi component scrap

1. Cryogenic Grinding
1

2. INTRODUCTION
 Cryogenic grinding, also known as freezer milling, freezer grinding
and cryo-milling is an act of cooling or chilling a material and then
reducing it into a small particle size.
 The term “Cryogenics” originates from Greek word “Kryos” and
“Genic” which means creation or production by means of cold.
 Cryogenic grinding technology can efficiently grind most tough
materials and can also facilitate cryogenic recycling of tough
composite materials and multi component scrap.
2

3. PROBLEMS FACED IN CONVENTIONAL
GRINDING PROCESS
 High heat generation (43°C-92°C)
 Gumming and clogging of mills
 Oxidation and related degradation
 Loss of etheric oil
3

4. CRYOGENIC GRINDING
 Cryogenics can also be defined as a branch of
engineering specializing in technical operations
at low temperature ( temp. below -150°C).
 Cryogenic grinding process uses cryogenic
liquids (cryogens) to achieve low temperature in
cryogenic grinding system.
4

5. CRYOGENS
 The extremely low temperature are produced by
using substances called “cryogens” such as
liquid nitrogen.
 All cryogenic liquids are gases at normal
temperatures and pressures. So, these gases must
be cooled below room temperature to liquefy
them.
 They have boiling points below -150°C.
5

6. FLUID BOILNG POINT
(K)
Helium-3 3.19
Hydrogen 20.27
Neon 27.09
Nitrogen 77.09
Air 78.8
Fluorine 85.24
Argon 87.24
Oxygen 90.18
Methane 111.7
6

7.  Cryogens are stored in vessels called as Dewar flask
which provides good insulation.
7

8. HEALTH HAZARDS OF CRYOGENIC
LIQUIDS
 Skin and eye hazard
 Cold embrittlement
 Oxygen enrichment
8

9. ADVANTAGES OF CRYO GRINDING
WITH LIQUID NITROGEN
 Higher retention of etheric oils
 Prevention of oxidation and rancidity
 Increased throughput and power saving
 Finer particle size
 Reduction in microbial load 9

10. CRYO GRINDING UNIT
The principal parts of system are :
 Feeder
 Pre cooler
 Liquid nitrogen distribution system
 Grinder
 Temperature controls
 Sensors 10

11. 11

12. Cryogenic pre-cooler
 The cryogenic pre-cooler is a cooling device made up
of a screw conveyor enclosed in a properly insulated
barrel and a system to introduce liquid nitrogen into
the barrel, thereby providing refrigeration within the
system.
 The function of the cryogenic pre-cooler is to remove
the heat from the material before it enters the grinder.
12

13. Feeding raw material into the
hopper
Chilling of spices with liquid
nitrogen
Feeding of material in mill
Grinding in mill at lower
temperature and inert atmosphere
Packing 13

14. INDUSTRIALLY USED CRYOGENIC
GRINDER
14

15. Traditional grinding system Cryogenic grinding system
 Heat is developed inside the grinding
mill.
 Temperature below 00C inside the
grinding mill.
 Heat developed, leads to evaporation
of essential oil and melting of heat
sensitive fats.
 Negligible loss of volatile compounds.
 Grinding elements becomes greasy
and even harms the machine by
blocking it.
 Not in cryogenic process.
 High energy consumption  Low energy consumption.
 High capacity motors are required to
grind the material.
 Low capacity motors are used to grind
the material.
 No control on particle size.  Particle size is under control.
15

16. Ambient ground Cryo-ground
16

17. ADVANTAGES
 Cryogenic grinding improves the aroma by minimizing
the loss of essential oils (approx. 3- 10% loss) which is
approx 15-43% in conventional processing.
 Spices processed using cryo-grinding has better natural
color, as compared to conventional process, this is very
much important for chilly and turmeric.
17

18.  Finer particle size can be achieved without aroma
loss and natural color change.
 Overall grinding capacity can be increased by 2
to 3 times, as process equipment will not have
thermal fatigue due to heating up.
18

19. DISADVANTAGES
 The application of cryogen in moist atmosphere
may cause formation of ice around the delivery
nozzle and the piping system carrying the
cryogen. This may cause a possible blockage in
the delivery system of liquid nitrogen
 Expensive
19

20. APPLICATIONS
 Cryogenic grinding of spices, cocoa and
chocolate, vanilla-sugar, dehydrated meat, etc.
 Thermoplastics
 Thermo sets
 Adhesives & waxes
 Explosives
20

21. CASE STUDY-1
21

22. Cryogenic grinding of black
pepper
C.T. Murthy, Suvendu Bhattacharya et al.
Journal of Food Engineering 85,(2010)
22

23. Objective
 Cryogenic grinding of black pepper at different
temperature and feed rates was conducted, and
was compared with conventional grinding.
 Comparing the particle size of powder, yield of
volatile oil, sensory attributes of powdered
samples are studied
23

24. Materials and Methods
 Black pepper
The samples were of medium size (4mm dia. ). Broken and
immature seeds and foreign matter was removed from
the samples prior to treatment.
 Grinder and grinding trails
A pin mill was employed for grinding the black pepper
under ambient and cryogenic conditions.
24

25.  Black pepper was loaded onto the hopper and was fed to
the grinder with the help of a vibratory feeder.
 After adjusting the feed rate to the required level, liquid
nitrogen was introduced into the grinding zone of the pin
mill such that the desired temperature was attained.
 Samples were collected in thick polyethylene bags and
were sealed immediately. All experiments were repeated
twice. 25

26. 26

27.  Particle size of powder
Particle size distribution of ground black pepper was
determined using a vibratory sieve shaker with a set of
British Standard (BS) sieves. Average particle size was
then calculated for the powder.
 Gas chromatographic analysis
The samples were analyzed in a gas chromatographic
analyser.
27

28.  Sensory studies
I. The powdered samples were subjected to sensory assessment.
Odour profiles were carried out by a trained panel consisting of
12 members.
II. The overall quality grading indicate that the mean score of up to 2
is not usable, 3 and 4 is poor, 5 is average, 6 is fair, 7 and 8 is
good, 9 and 10 is very good.
28

29. Results and Discussion
Cryogenically ground samples (C1–C9) are initially
compared with ambient ground samples (A1, A2) in terms
of quantity of volatile oil yield, particle size of the powder,
and quality of volatile oil.
29

30. Gas ChromatographicAnalysis of
Volatile Oil
30

31. Sensory Attributes of Powdered
Samples
31

32. Conclusions
 The pilot scale cryogenic grinding studies of black pepper have been
conducted and the product characteristics are compared with ambient
ground samples.
 The average volatile oil yield in case of cryogenic grinding is 1.7
mL/100 g whereas it is 0.9 mL/100 g for ambient system.
 The gas chromatographic analysis of volatile oil indicates that the
ratio of monoterpenes to sequiterpenes varies from 1.35 to 1.85 in the
case of cryogenic grinding, whereas, the ambient ground samples
have a very low ratio 0.22–0.31.
32

33.  Sensory assessment of cryogenically ground samples indicated
that these samples are distinctly high in top notes which
represent freshness, and is marginally high in basic notes.
 Hence, the quality of cryogenically ground sample is better
than the conventionally ground samples.
33

34. CASE STUDY 2
34

35. Cryogenic grinding technology enhances
volatile oil, oleoresin and antioxidant activity
of cumin (Cuminum cyminum L.)
S. N. Saxena et al
International Journal of Seed Spices 4(2), 2014
35

36. Objective
 To prove that cryogenic grinding of cumin is better than
non cryo-grinding in terms of higher retention of volatile
oil, total oil, total phenolic content, total flavonoid
content and antioxidant properties of ground powder.
36

37. Materials and Methods
 Seeds of two varieties of cumin (GC-4 and RZ-209), were
cleaned and used for cryogenic grinding and non cryo
grinding.
 Ground powder was used for extraction of volatile oil and
total oil as well as total phenolic content, total flavonoid
content and antioxidant properties of ground powder.
37

38.  Grinding of seeds
For cryo-ginding:
Fed in hopper
Liquid nitrogen
sprayed and blend
Brittle material
enters impact mill
Packed quickly
38

39.  To obtaining seed powder through non-cryo grinding
dried seeds was ground separately by domestic mixer
grinder.
 Essential oil was extracted from seed powder and was
estimated using all glass Clevenger apparatus.
 Crude seed extract was used for determination of the total
phenol and flavonoids concentration, as well as
antioxidant activities.
39

40. Result
 Cryogenic grinding not only retains the volatiles
in both the genotypes but enhanced the recovery
also.
 Non cryogenic or normal grinding at ambient
temperature causes 18-19 % loss of volatile oil in
both the genotypes.
40

41. 41

42. 42

43. Conclusion
 From present study it could be concluded that
cryogenic grinding technology is superior to non
cryogenic grinding for retention of flavour and
antioxidant properties of cumin irrespective of
the genotype.
43

44. SUMMARY
 As the cost of raw materials and energy is increasing day
by day, it is very necessary to use optimum quantity and
at the same time getting the required quality.
 Cryogenic grinding can be used as a solution.
 Value added products are obtained.
 Spice industries of our country will earn considerable
foreign exchange by exporting more value added
processed spices, in place of exporting whole spices.
44

45. REFERENCE
 Andres, C. (1976). “Grinding spices at cryogenic temperatures retains volatiles and oils”.
Food Processing, 37(9), 52-53.
 D. Landwehr, and M.H. Pahl, “Cold grinding of spices,” International Journal of Food
Technology and Food Process Engineering, vol. 37, 174-185, (1986).
 J.R. Russo, “Advanced techniques in new spice plant-cryogenic grinding material handling,”
Food Engineering International, vol. 1, 33-35, (1976).
 Murthy, C. T., Krishnamurthy, N., Ramesh, T., & Srinivasa Rao, P.N. (1996). Effect of grinding
methods on the retention of black pepper volatiles. Journal of Food Science and
Technology, 33(4), 299-301.
 R.K. Kumar, “Modification and performance evaluation of indigenous cryogenic grinder,”
M.Tech. Thesis, Dept. of Agrl. and Food Engg., IIT Kharagpur, Kharagpur, India, (2001).
 S. Balasubramanian, M.K. Gupta, and K.K. Singh K. K, “Cryogenics and its application with
reference to spice grinding: a review,” Critical reviews in food science and nutrition, vol. 52,
781-794, (2012).
 Singh, K. K., & Goswami, T. K. (1996). “Physical properties of cumin seed”. Journal of
Agricultural Engineering Research, 64(2), 93-98.
 S. Li, S. Ge, Z. Huang, Q. Wang, H. Zhao, and H. Pan, “Cryogenic grinding technology for
traditional Chinese herbal medicine,” Cryogenics, vol. 31, 136-137, (1991).
 Venetucci, J. M. (1980). “Cryogenic grinding of food stuffs” In N. R.Braton, Cryogenic
recycling and processing, 148-181 CRC Press Inc., USA.
 Wolf, T., & Pahl, M. H. (1990). Cold grinding of caraway seeds in impact mill. International
Journal of Technology and Food Process Engineering, 41(10), 596-604.
45

46. 46