Les procédés d’agglomération par sollicitations mécaniques. Application à la structuration de la semoule de blé dur pour la fabrication du couscous

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Les procédés d’agglomération par sollicitations mécaniques. Application à la structuration de la semoule de blé dur pour la fabrication du couscous

Bettina Bellocq, Bernard Cuq, Agnès Duri-Bechemilh, Thierry Ruiz

To cite this version:

Bettina Bellocq, Bernard Cuq, Agnès Duri-Bechemilh, Thierry Ruiz. Les procédés d’agglomération par sollicitations mécaniques. Application à la structuration de la semoule de blé dur pour la fabrication du couscous. 16. Congrès de la société française de génie des procédés (SFGP 2017), Jul 2017, Nancy, France. �hal-01602787�

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LES PROCÉDÉS D’AGGLOMÉRATION PAR SOLLICITATIONS MECANIQUES.

APPLICATION A LA STRUCTURATION DE LA SEMOULE DE BLÉ DUR POUR LA FABRICATION DU COUSCOUS .

Be#na Bellocq

Under the supervision of:

Pr. Bernard CUQ, Dr. Thierry RUIZ and Dr. Agnès DURI

UMR IATE INRA Montpellier – France

16^ème Congrès de la Société Française de Génie des Procédés

Nancy – 12 Juillet 2017

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Plan

1 2 3 4

INTRODUCTION - WET AGGLOMERATION DURUM WHEAT SEMOLINA AND MIXERS IMPACT OF THE PROCESS

CONCLUSION

5 HYDROTEXTURAL ANALYSIS

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Plan

LES PROCEDES D’AGGLOMERATION PAR SOLLICITATIONS MECANIQUES PLAN

1 2 3 4

INTRODUCTION - WET AGGLOMERATION DURUM WHEAT SEMOLINA AND MIXERS IMPACT OF THE PROCESS

CONCLUSION

5 HYDROTEXTURAL ANALYSIS

(5)

INTRODUCTION

AgglomeraVon is largely used to

improve the powders properVes and behaviour:

- Reduc8on in dust produc8on.

- Enhancement in ﬂowability.

- Increase in bulk density.

- Reduc8on in segrega8on.

- Cocoa beverage powders - Instant soluble coﬀee - Culinary powders - Flavors powders - Protein powders - Infant formulas

- Couscous grains - Dairy powders - Milk powders - Bakery mixes - Starch

Agglomerated food powders

1.1. WET AGGLOMERATION OF FOOD POWDERS

During the agglomeraQon process…

…the naVve small parVcles are gathered to form larger assemblies with speciﬁc porous structures, called

the agglomerates.

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INTRODUCTION

LES PROCEDES D’AGGLOMERATION PAR SOLLICITATIONS MECANIQUES

2. AgglomeraVon is largely used to

improve the powders properVes and behaviour:

- Reduc8on in dust produc8on.

- Enhancement in ﬂowability.

- Increase in bulk density.

- Reduc8on in segrega8on.

Agglomerated food powders

- Cocoa beverage powders - Instant soluble coﬀee - Culinary powders - Flavors powders - Protein powders - Infant formulas

- Couscous grains - Dairy powders - Milk powders - Bakery mixes - Starch

- Couscous grains

1.1. WET AGGLOMERATION OF FOOD POWDERS

During the agglomeraQon process…

…the naVve small parVcles are gathered to form larger assemblies with speciﬁc porous structures, called

the agglomerates.

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hOp://www.cjtech.co.kr/Process%20Principles%20Agglomera8on%20Granula8on.htm

INTRODUCTION

1.2. WET AGGLOMERATION - PROCESS

During the agglomeraQon process, a liquid binder (water) is sprayed

over an agitated powder bed.

It generates a_racVve interacVons and links between the naQve

parQcles and …

… Promotes the spaVal

arrangement of the naVve parVcles

with the binder.

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4. INTRODUCTION

The variability of the raw materials associated with the diﬀerences between diﬀerent apparatus induce a high degree of complexity in the process.

The pneumaVc mixing granulators (e.g.

steam jet, spray drying, or ﬂuid bed) use air steam to agitate the parQcles under

low shear condiQons.

The mixing granulators (e.g. mechanical mixer, pan, disk, or drum granulators)

use mechanical system to agitate the parQcles.

Ex. Fluidized bed

Ex. Planetary mixer

Diﬀerent technologies have been used for wet agglomeraQon processes. They can be classiﬁed in two categories according to the type of the mixing energy.

1.2. WET AGGLOMERATION - PROCESS

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INTRODUCTION

1.3. WET AGGLOMERATION - MECHANISMS

The cohesion forces generate interacVons between parQcles, and promote granules growth.

Wet agglomeraQon process is classically described as a combinaQon of successive mechanisms at diﬀerent rates :

- We#ng and nucleaVon.

- Growth and consolidaVon.

- Breakage, erosion, rupture

Native powder

GROWTH

NUCLEATION

WETTING

Water drops

CONSOLIDATION

Agglomerates

GROWTH

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6. INTRODUCTION

1.3. WET AGGLOMERATION - MECHANISMS

Native powder

GROWTH

NUCLEATION

WETTING

Water drops

CONSOLIDATION

Agglomerates

GROWTH

RUPTURE

+

^RUPTURE

+

Wet agglomeraQon process is classically described as a combinaQon of successive mechanisms at diﬀerent rates :

- WeZng and nuclea8on.

- Growth and consolida8on.

- Breakage, erosion, rupture

The rupture forces and shearing eﬀects, lead to breakage and to reduce

the granule size.

The wet agglomeraQon process is a balance between growth and breakage

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Schema of the hydrotextural diagram (Ruiz et al., 2005)

1.4. HYDROTEXTURAL APPROACH

INTRODUCTION

Hydrotextural approach is used to describe agglomeraVon mechanisms based on changes in compactness and

diameter of the agglomerates as a

funcQon to the water content.

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7. 1.4. HYDROTEXTURAL APPROACH

INTRODUCTION

Hydrotextural approach is used to describe agglomeraVon mechanisms based on changes in compactness and

diameter of the agglomerates as a funcQon to the water content.

Hydrotextural diagram is limited by the saturaVon curve unQl which

agglomerates are completely ﬁlled by

water.

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1.4. HYDROTEXTURAL APPROACH

INTRODUCTION

Hydrotextural approach is used to describe agglomeraVon mechanisms based on changes in compactness and

diameter of the agglomerates as a funcQon to the water content.

Hydrotextural diagram is limited by the saturaVon curve unQl which

agglomerates are completely ﬁlled by water.

Agglomerates were analysed by measuring :

Size = Median diameter

Water content = Mass of water / Mass of dry product Compactness = Volume of solid / Total Volume

Satura3on degree = Volume of liquid / Volume of void

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8. INTRODUCTION

1.5. CASE OF THE COUSCOUS GRAINS

Mixing and rolling

(~ 300 µm)

(~ 1500 µm)

Troo small

recyclates Wet

Too large

Sieving Crushing

Semolina

Wet couscous grains

Water

Drying recyclates ^Dried

Too small Too large

Steam cooking

Crushing

Dust

Sieving

Final couscous grains

Co oki ng Dry in g

Cooked couscous grains

Ag gl om er aV on

- 3 unit operaVons.

- Polydispersity of the size cause a high raQo of out of

scope (too large >2 mm, or too

small <1 mm).

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INTRODUCTION

- 3 unit operaVons.

- Polydispersity of the size cause a high raQo of out of

scope (too large >2 mm, or too small <1 mm).

- AgglomeraVon is a key unit operaVon to control the size of the couscous grains.

1.5. CASE OF THE COUSCOUS GRAINS

Mixing and rolling

(~ 300 µm)

(~ 1500 µm)

Troo small

recyclates Wet

Too large

Sieving Crushing

Semolina

Wet couscous grains

Water

Drying recyclates ^Dried

Too small Too large

Steam cooking

Crushing

Dust

Sieving

Final couscous grains

Co oki ng Dry in g

Cooked couscous grains

Ag gl om er aV on

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9. INTRODUCTION

1.6. OBJECTIVES

Our objecVves were:

à  To describe the agglomeraVon by analysing experimental invesQgaQons.

à  To understand how the process impact the agglomeraQon.

à  To understand how the raw material (diameter and protein) impact the agglomeraQon.

AGGLOMERATION ROLLING COOKING DRYING

Durum wheat semolina Wet agglomerates Cooked agglomerates Couscous grains

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INTRODUCTION

1.6. OBJECTIVES

Our objecVves were:

à  To describe the agglomeraVon by analysing experimental invesQgaQons.

à  To understand how the process impact the agglomeraQon.

à  To understand how the raw material (diameter and protein) impact the agglomeraQon.

AGGLOMERATION ROLLING COOKING DRYING

Durum wheat semolina Wet agglomerates Cooked agglomerates Couscous grains

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Plan

1 2 3 4

INTRODUCTION - WET AGGLOMERATION DURUM WHEAT SEMOLINA AND MIXERS IMPACT OF THE PROCESS

CONCLUSION

5 HYDROTEXTURAL ANALYSIS

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2.1. RAW MATERIAL

MATERIAL & METHODS

Wheat powder (durum wheat semolina)

- Large parQcles (d

₅₀

= 287 µm) with distribuVon of diameters.

- Dense naQve parQcles (not porous).

Biochemical composiQon : starch (85%), proteins (12%), ﬁbres (2%), and lipids (1%).

- Components are partly soluble.

CharacterisQcs Values Method

Water content (%) 16.4 (± 0.5)

Method 44-15A AACC

Protein content (%) 12.4 (± 0.4)

Method 050 (AFNOR

ParQcle size mediam diameter (µm) 287 (± 8)

Laser granulometry

ParQcle size span (-) 1.56 (± 0.17)

Laser granulometry

True density (g/cm

³

) 1.478 (± 0.005)

Helium pycnometry

PlasQc limit (%) 59 (± 1)

Aqerberg tests

Liquid limit (%) 76 (± 2)

Aqerberg tests

Durum wheat semolina

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11. 2.2. MECHANICAL MIXERS

LES PROCEDES D’AGGLOMERATION PAR SOLLICITATIONS MECANIQUES Nozzle

K rotaQve blase

Nozzle

RotaQve blade

Nozzle

RotaQve blade

RotaQve bowl

Planetary mixer Horizontal mixer Ver8cal mixer

Mixers Speed

(rpm) Froude number

(-) Water content

(-) Mixing Qme

(min)

Planetary 70 - 180 0.03 – 0.16 0.33 – 0.38 – 0.45 0 – 5 - 15

Horizontal 114 - 228 0.02 – 0.05 0.39 – 0.42 – 0.49 0 – 5 - 15

VerQcal 80 - 200 0.03 – 0.17 0.33 – 0.38 – 0.45 0 – 5 - 15

MATERIAL & METHODS

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2.2. MECHANICAL MIXERS

Nozzle

K rotaQve blase

Nozzle

RotaQve blade

Nozzle

RotaQve blade

RotaQve bowl

Planetary mixer Horizontal mixer Ver8cal mixer

Mixers Speed

(rpm) Froude number

(-) Water content

(-) Mixing Qme

(min)

Planetary 70 - 180 0.03 – 0.16 0.33 – 0.38 – 0.45 0 – 5 - 15

Horizontal 114 - 228 0.02 – 0.05 0.39 – 0.42 – 0.49 0 – 5 - 15

VerQcal 80 - 200 0.03 – 0.17 0.33 – 0.38 – 0.45 0 – 5 - 15

MATERIAL & METHODS

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11. 2.2. MECHANICAL MIXERS

LES PROCEDES D’AGGLOMERATION PAR SOLLICITATIONS MECANIQUES Nozzle

K rotaQve blase

Nozzle

RotaQve blade

Nozzle

RotaQve blade

RotaQve bowl

Planetary mixer Horizontal mixer Ver8cal mixer

Mixers Speed

(rpm) Froude number

(-) Water content

(-) Mixing Qme

(min)

Planetary 70 - 180 0.03 – 0.16 0.33 – 0.38 – 0.45 0 – 5 - 15

Horizontal 114 - 228 0.02 – 0.05 0.39 – 0.42 – 0.49 0 – 5 - 15

VerQcal 80 - 200 0.03 – 0.17 0.33 – 0.38 – 0.45 0 – 5 - 15

MATERIAL & METHODS

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2.2. MECHANICAL MIXERS

Nozzle

K rotaQve blase

Nozzle

RotaQve blade

Nozzle

RotaQve blade

RotaQve bowl

Planetary mixer Horizontal mixer Ver8cal mixer

Mixers Speed

(rpm) Froude number

(-) Water content

(-) Mixing Qme

(min)

Planetary 70 - 180 0.03 – 0.16 0.33 – 0.38 – 0.45 0 – 5 - 15

Horizontal 114 - 228 0.02 – 0.05 0.39 – 0.42 – 0.49 0 – 5 - 15

VerQcal 80 - 200 0.03 – 0.17 0.33 – 0.38 – 0.45 0 – 5 - 15

MATERIAL & METHODS

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12. 2.3. WET GRANULATION PROCESS

MATERIAL & METHODS

Stage 1 - Mixing Stage 2 – Water addiVon and agglomeraVon Water

Mixing Mixing

Powder

Wet agglomerates

Water added manually or using a water spraying nozzle with a

constant ﬂow rate (2 g/sec).

Power consumpVon by the mixer arm during

the process.

Final mass close to 50% of the capacity

of the mixer.

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0.71 mm 0.85 mm 0.90 mm 1.25 mm 2.00 mm MATERIAL & METHODS

2.4. AGGLOMERATES CHARACTERISTICS

Size distribuVon

by sieving: d50, span, yield per sieves.

DistribuVon of water content

by weighing ader oven drying at 105°C for 24h.

DistribuVon of compactness

hydrosta8c balance (Precisa serie 321 LX 120+ density kit).

To describe the agglomeraVon mechanisms and the product characterisQcs, we

evaluated the size distribuVon and the agglomerates characterisVcs on each

sieve.

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Plan

1 2 3 4

INTRODUCTION - WET AGGLOMERATION DURUM WHEAT SEMOLINA AND MIXERS IMPACT OF THE PROCESS

CONCLUSION

5 HYDROTEXTURAL ANALYSIS

(27)

RESULTS

3.1. DESCRIPTION OF THE GRANULATION

0 0.1 0.2 0.3

0 0.5 1 1.5 2

Mass frequency (%)

Dough pieces Agglomerates

Nucléi Fragments

Small

Large dispersion in size was observed. Speciﬁc shape and hydrotextural

characterisQcs allow disQnguishing 5 types of structures according to their diameter:

- Small (0.3 – 0.5 mm) = naQve parQcles of semolina

- Fragments (0.5 – 0.6 mm) = mechanical erosion of larger structures - Nuclei (0.6 – 1.0 mm) = primary associaQon of semolina parQcles - Agglomerates (1.0 – 2.0 mm) = associaQon of fragments and/or nuclei

- Dough pieces (>2.0 mm) = associaQon of agglomerates which passes the

percolaQon state

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15. RESULTS

0.4 0.6 0.8

0.5 1 1.5 2 2.5 3

Compactness (solid volume fracVon)

Diameter (mm) 0.2

0.4 0.6

0.5 1 1.5 2 2.5 3

Water content (g/g dry ma_er)

Diameter (mm)

AgglomeraQon growth of semolina to produce couscous grains leads to:

- Increasing water content - Decreasing compactness

according to an increase in the

median diameter of the structures.

EvoluQon of the size distribuQon of the agglomerated structures with water

content and compactness shows:

(i)   A conVnuous growth process associated with the expansion of their

internal structure.

(ii)   A fragmentaVon of the dough pieces.

3.1. DESCRIPTION OF THE GRANULATION

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.

0 0.2 0.4

0 0.5 1 1.5 2

Mass frequency (%)

Diameter (mm)

wi = 0.330 wi = 0.377 wi = 0.454

Polydispersity of the size. 5 structures with speciﬁc characterisQcs of size, compactness and water content.

An increase of the water content lead to an increase of the median diameter of the populaQon in the mixer aser the granulaQon.

RESULTS

3.2. IMPACT OF THE WATER CONTENT

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17.

0.2 0.4 0.6

0.3 1.3 2.3

Diameter (mm)

wi = 0.330 wi = 0.377 wi = 0.454

0.4 0.6 0.8

0.3 1.3 2.3

Diameter (mm)

wi = 0.330 wi = 0.377 wi = 0.454

An increase of the water content increase the mean water content

of each structure aser the granulaQon.

An increase of the water content decrease the mean compactness content of each structure aser the

granulaQon.

3.2. IMPACT OF THE WATER CONTENT

RESULTS

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.

0 0.2 0.4

0 0.5 1 1.5 2

Diameter (mm)

80 rpm 200 rpm

0.2 0.4 0.6

0.3 1.3 2.3

Diameter (mm)

80 rpm 200 rpm

0.4 0.6 0.8

0.3 1.3 2.3

Diameter (mm)

80 rpm 200 rpm

- The raQo of the 5 structures is diﬀerent à An increase of the speed leads to an increase of the breakage and erosion mechanisms.

- No impact of the speed in the water content and the

compactness of each structure.

RESULTS

3.3. IMPACT OF THE MIXING SPEED

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.

19.

0 0.1 0.2 0.3

0 0.5 1 1.5 2

Diameter (mm)

VerQcal Horizontal Planetary

0.25 0.45 0.65

0.55 1.05 1.55 2.05 2.55 Water content (g/g dry ma_er)

Diameter (mm)

0.25 0.45 0.65 0.85

0.55 1.05 1.55 2.05 2.55

Diameter (mm)

- The raQo of the 5 structures is diﬀerent à More breakage and erosion mechanisms in the

planetary mixer.

- The mixers do not have an impact on the water content and the

compactness of each structure.

RESULTS

3.4. IMPACT OF THE MIXERS

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Plan

1 2 3 4

INTRODUCTION - WET AGGLOMERATION DURUM WHEAT SEMOLINA AND MIXERS IMPACT OF THE PROCESS

CONCLUSION

5 HYDROTEXTURAL ANALYSIS

(34)

20. DISCUSSION

0.4 0.6 0.8 1

0.3 0.4 0.5 0.6

Compactness (/)

Water content (g/g dry ma_er)

PasQc limit wp ∼ 0.59

Increasing diameter

4.1. DATA ANALYSIS

(35)

DISCUSSION

0.4 0.6 0.8 1

0.3 0.4 0.5 0.6

Compactness (/)

Increasing diameter

4.1. DATA ANALYSIS

Analysis of the mean values of water content and

compactness.

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20. DISCUSSION

0.4 0.6 0.8 1

0.3 0.4 0.5 0.6

Compactness (/)

Increasing diameter

4.1. DATA ANALYSIS

Analysis of the mean values of water content and

compactness.

Analysis of the heterogeneity of water content and

compactness around their

mean values.

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DISCUSSION

0.4 0.6 0.8 1

0.3 0.4 0.5 0.6

Compactness (/)

Increasing diameter

4.1. DATA ANALYSIS

Global heterogeneity W

_G

= (W

_max

- W

_min

)/ W

_moy

Analysis of the mean values of water content and

compactness.

Analysis of the heterogeneity of water content and

compactness around their

mean values.

(38)

20. DISCUSSION

0.4 0.6 0.8 1

0.3 0.4 0.5 0.6

Compactness (/)

Increasing diameter

4.1. DATA ANALYSIS

Global heterogeneity W

_G

= (W

_max

- W

_min

)/ W

_moy

Local heterogeneity W

_L

= (W - W

_moy

)/ W

_moy

Analysis of the heterogeneity of water content and

compactness around their mean values.

Analysis of the mean values of water content and

compactness.

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DISCUSSION

4.2. MEAN VALUES ANALYSIS

0.4 0.6 0.8 1.0

0.2 0.3 0.3 0.4 0.4 0.5 0.5 0.6 0.6

We have represented on the diagram the mean values of water content and compactness of the structures for all the process condiVons.

The process condiQons do not change the hydrotextural properVes of the structures:

they are all saturated by water.

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22. DISCUSSION

4.3. LOCAL HETEROGENEITY ANALYSIS

-0.3 -0.1 0.1 0.3

-0.5 -0.3 -0.1 0.1 0.3 0.5

Compactness standard deviaVon (-)

Water content standard deviaVon (-)

The ﬂuctuaVons of the water content and the compactness are correlated around their respecQve mean values for all the process condiVons.

The growth of the agglomerates respects an associaVon by same sizes and hydro-

textural categories.

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Plan

1 2 3 4

INTRODUCTION - WET AGGLOMERATION DURUM WHEAT SEMOLINA AND MIXERS IMPACT OF THE PROCESS

CONCLUSION

5 HYDROTEXTURAL ANALYSIS

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23. •  5 structures in the mixer aser the granulaQon.

•  ConQnuous growth process is associated with the expansion of the internal structure.

•  The process (water content, speed and mixers) has a signiﬁcant inﬂuence on the yield of the agglomeraQon, but …

•  … does not have an inﬂuence on the agglomerates properVes (water content and compactness) as a funcQon to their size.

•  FluctuaVons of the water content and the compactness are correlated around their respecQve mean values à associaVon by same sizes and hydro-textural categories.

CONCLUSION

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QUESTIONS ?

Thanks for your aqenQon

Be#na Bellocq

Under the supervision of:

Pr. Bernard CUQ, Dr. Thierry RUIZ and Dr. Agnès DURI

UMR IATE INRA Montpellier – France

16^ème Congrès de la Société Française de Génie des Procédés

Nancy – 12 Juillet 2017