Fruit powder characteristics, industrial problems, solutions, role of fruit powder in foo processing.

1. Fruit Powders
PREETI BIRWAL
PH.D (DE)
ICAR-NDRI

2. Introduction
 The popularity of fruits may be attributed to consumer perception of
their health benefits.
 In the case of fruit juices, many consumers are now looking for healthy
alternatives to the traditional carbonated beverages.
 Fruits are rich in dietary fibre as well as phytonutrients, especially
antioxidants, and have no cholesterol.
 The availability in the market of natural fruit juices derived from fresh
fruits is a welcome alternative
 Fruits are important sources of vitamins and carbohydrates. They are
naturally sweet and low in calories. Different fruits contain different type
of vitamins, so it is important to have a variety of fruits.
 Fruits are the important intake of our daily diet life. There is no cause of
side effect by fruits because it provides necessary vitamins to our body.
The vitamins are important to humans for providing energy to away
from various kinds of sickness

3. Fruit Powder
The powder can be used as an ingredient for cooking food or as a
flavoring agent in some products. Its advantages consist of
 (a) a long shelf life at ambient temperature due to low water
activity,
 (b) low logistic expenditures due to little weight and volume, and
 (c) vast multi disciplinary uses.

4. One of the widely spread methods of preserving such products
consists in drying both fruits and berries as well as organization of
production of various kinds of the new products in a form of
powders either from juices and extracts ( totally soluble) or powders
obtained from whole fruits including cellular tissue and other
components of fruits which undergo processing to two directions are:
 I- production of soluble fruit-dairy powders by spray drying;
 2- production of fruit and vegetable powders by convective
drying.

5.  The drying of pure (without any additives) juices from fruits is quite
Complex. It is determined primarily by the thermoplastic properties
of the drying material as well as the considerably hygroscopic nature
of the powder-like product.
 Chemical composition of juices is very complex too, approx. 90% of
dry substances in juices and purees made up of hydrocarbons:
monosaccharides (glucose, fructose), disaccharides (saccharose)
and polysaccharides.
 To the nutrient substances are added hydrocarbons, nitrogen
containing substances, organic acids, plyphenol substances,
vitamins etc. Under the influence of temperature and air oxygen
inside the spray drying chamber various complicated transformations
of component substances may take place which reveal themselves in
changing of color and decrease of the nutrient quality.

6. Steps
 Sorting
 Grading
 Cleaning
 Sulphating
 Alkaline dip
 Blanking
 Juice extraction
 Clarification
 Filtration
 Juice concentration
 Drying

9. Drying
 Drum Drying
 Spray Drying
 Freeze Drying
 Microwave and dielectric Drying
 Spouted Bed Drying
 Pneumatic and Flash Drying
 Superheated Steam Drying
 Fluidization Bed drying
 Foam Drying
 Rotary
 Belt and Tunnel Drying

10. Fruits and Vegetables
 Fruit puree( Grapes, apple,
cherry)
 Grape juice
 Lime juice
 Pear juice
 Pineapple juice
 Mango juice
 Orange juice
 Citrus juices
 Blueberry juice
 Beetroot juice
 Carrot juice
 Passion fruit juice
 Acerola juice
 Coconut juice
 Other vegetable juices

12. Dryer Selection Chart
A guide to dyer selection

13.  FORMULATION AND EVALUATION OF A POWDER
 Production of powder by drum dryer using maltodextrin and Arabic
gum as adjuncts
 MD were preferred in facet of appearance, color, and overall liking,
while those with AG were favored in their aroma and taste.
 Micro-encapsulated powders
 Sugar-rich products
 Fruit powder is just one step past drying fruit, too; after a brief
conditioning phase, all you have to do is pulverize it. For best color,
taste and texture, use the freshest, ripest fruit available.

14. Powder characteristics
 Bulk density
 Particle morphology
 Angle of repose
 Wettability
 Dispersion
 Solubility
 Moisture content
 Free flowing
 Fine
 Dustless
 Granules
 Agglomerated
 Lumps
 Hygroscopic
 Hydrophobic
 Thermoplastic

16. A typical
two-
stage
spray
dryer
Source: Dairy Processing Handbook.
Published by Tetra Pak Processing
Systems AB, S-221 86 Lund, Sweden.
pg. 369.

17. Operating conditions
 Electricity heater heated inlet air until 80-200°C.
 when outlet air temperature was in the range of 100-110°C.
 Rotary atomizer with 25000-rpm speed.
 Cyclone with effective diameter 10 cm separated the air-powder
mix.
 The ambient air ambient temperature is about 20-25°C and relative
humidity of 35-45%.
 0.5-0.8 g cm3 density.

18. Source: Dairy
Processing
Handbook.
Published by Tetra
Pak Processing
Systems AB, S-221 86
Lund, Sweden. pg.
370.
FILTERM
AT
DRYER

19. Factors Affecting Powder Properties
Inlet temperature
 Powder properties such as moisture content, bulk density, particle size,
hygroscopicity and morphology were affected by inlet temperature.
 It was found that at a constant feed flow rate, increasing the inlet air
temperature reduced the residual moisture content.
 Increased temperature caused the reduction in bulk density. An
increase in the inlet air temperature often results in a rapid formation of
dried layer on the droplet surface and particle size and it causes the
skinning over or casehardening on the droplets at the higher
temperatures. This leads to the formation of vapor-impermeable films
on the droplet surface, followed by the formation of vapor bubbles
and, consequently the droplet expansion increase of drying air
temperature generally causes the decrease in bulk, particle density
and provides the greater tendency to the particles to hollow

20.  higher inlet air temperature leads to the production of larger
particles and causes the higher swelling.
 The higher drying temperature is lower the moisture content and
increase its hygroscopicity (its capacity to absorb ambient
moisture). This is related to the water concentration gradient
between the product and the surrounding air, which is great for the
less moist powder.
 On the other hand, the increase of inlet air temperature has
reduced the yield and it might be caused by melting of the powder
and cohesion wall and therefore the amount of powder production
and yield was reduced
 When the inlet air temperature was low, the particles showed a
shriveled surface, while increasing drying temperatures resulted in a
larger number of particles with smooth surface.

21. Air flow rate
 The increased residence time led to the greater degree of moisture
removal.
 As a result, an increase of the drying air flow rate, decrease the
residence time of the product in the drying chamber and it leads to
have higher moisture contents.
 In addition, the effect of drying air flow rate of powder bulk density
depends on its effect on moisture content due to the sticky nature
of the product.

22. Atomizer speed
 The residual moisture content was decreased when increasing the
atomizer speed.
 At higher atomizer speed, the smaller droplets were produced and
more moisture was evaporated resulting from an increased contact
surface.

23. Feed flow rates
 Higher flow rates imply in a shorter contact time between the feed
and drying air and making the heat transfer less efficient and thus
caused the lower water evaporation.
 The higher feed flow rate showed a negative effect on process yield
and that was resulting the decreased heat, mass transfer and the
lower process yield. In addition, when higher feed rates were used,
a dripping inside the main chamber was observed, when the
mixture was passed straight to the chamber and that was not
atomized and finally resulting the lower process yield.

25. Type of carrier agent
 The result showed that the higher the maltodextrin dextrose
equivalent (DE) causes higher the moisture content in the powder.
This probably due to the chemical structure of high-DE
maltodextrins, which have a high number of ramifications with
hydrophilic groups, and thus can easily bind to water molecules
from the ambient air during powder handling after the spray drying.
 Additionally, higher maltodextrin DE caused the increase in bulk
density in the powder due to its stickiness.
 The higher maltodextrin DE was produced the lower glass transition
temperature and it lower the elevation of the Tg in fruit pulp-
maltodextrin mixture

26.  The result was revealed that the particles produced with
maltodextrin 10DE showed the lowest moisture adsorption rate,
while the samples were produced with maltodextrin 20DE and gum
Arabic had more hygroscopic and with faster water adsorption and
the lower moisture in the powders
 The different type of carrier agent was having the variance in
powder solubility

27. Problems
 Some researchers claimed that drying of fruit juice could produce
the fruit powder that reconstituted rapidly to a fine product
resembling the original juice.
 Nonetheless, there are some difficulties in drying the fruit juice with
high sugar content due to their thermoplasticity and hygroscopicity
at high temperatues and humidity levels causing their packaging
and utilization in trouble
 These characteristics are attributed to low molecular weight sugars
such as fructose, glucose and sucrose and organic acids such as
citric, malic and tartaric that are the major solids in fruit juices
 The low glass transition temperature (Tg), high hydroscopy, low
melting point, and high water solubility of these solids lead to highly
sticky or rubbery product when dried

28.  Natural hygroscopic and thermoplastic property physical properties
of fruit juice aided to drying.
 These of fruit juice is the basis problem in transport and agent
materials include corn syrup; natural gums, sucrose, handling of fruit
juice powder produced in spray malt dextrin etc…caused powder
production and prevent dryer agent materials include corn syrup;
natural gums, sucrose, malt dextrin

29. The drum drying parameters such as
 drying temperature,
 Feed rate,
 rotation speed,
 feed concentration, and
 surrounding air condition
are influential to the attributes of drum-dried food such as particle size,
bulk density, moisture content, and solubility

30. Stickiness issues during spray drying
• Stickiness on the drier wall (spray drying)
• Wet and plastic appearance
• Agglomeration and clumping in packing container
• Operational problems
• Losses

31. Sticky
product
Hot air
Non-sticky
product

32. Products exhibiting stickiness during drying
• Products with high amount of sugars or organic
acids
– Fruit juices/pieces/purees/leathers
– Honey
– Molasses
– Whey (acid or sweet)
– High DE maltodextrins (DE>30)
– Pure sugars- glucose, sucrose, fructose
– High acid foods
• High fat foods

33. Major factors causing stickiness
• High hygroscopicity
• High solubility
• Low melting point temperature
• Low glass transition temperature
(related to thermoplasticity)

34. What is a glass transition?
– Amorphous
• non-aligned molecular structure
• very hygroscopic
• go through glass transition
• predominant in dried food
– Crystalline
• aligned molecular structure
• non hygroscopic
• no glass transition
Physical states of dried solid materials

35. Semi-crystalline solid Liquid solution
Grinding
Extrusion cooking
Thermal melting & cooling
Rapid water
removal- drying
Rapid cooling below Tg
water <-135oC
honey <-45oC
Amorphous solid
(glass)
Crystalline solid

36. Solid Liquid
Glass transition
Stickiness
Property of an amorphous solid

37. _______________________________________________________
Food materials Tg (o
C)abc
_______________________________________________________
Fructose 14
Glucose 31
Galactose 32
Sucrose 62
Maltose 87
Lactose 101
Citric acid 6
Tartaric acid 18
Malic acid -21
Lactic acid -60
Maltodextrins
DEd
36 (MW=550) 100
DE 25 (MW=720) 121
DE 20 (MW=900) 141
DE 10 (MW=1800) 160
DE 5 (MW=3600) 188
Starch 243e
Ice-cream f
-34.3
Honeyg
-42 to -51
Glass transition temperature of various food materials

38. Spray drying of sticky product
some guideline
• Drying below the glass transition temperature (often
not feasible)
• Mild drying temperature conditions
• Increasing the Tg by adding high molecular weight
materials (such as maltodextrins)- a predictive
approach needed according to the composition
• Immediate cooling of the product below its Tg
• Appropriate drier design to suit the sticky product

39.  The thermoplasticity and hygroscopicity troubles occurring in drying the fruit
juice with high sugar content can be overcome by adding some drying
carriers such as maltodextrin (MD) and Arabic gum (AG).
 These drying adjuncts are high molecular weight compounds that have high
Tg , accordingly, they can raise the Tg Value of feed and the subsequent
powder.
 MD is the most popular in spray drying due to its physical properties such as
high water solubility; while, AG is recommended
 For fruit juice drying due to its emulsification properties and ease of dissolution
in water.
 MD consists of b-D-glucose units linked mainly by glycosidic bonds and are
typically classified by their dextrose equivalent (DE).
 MD could improve the stability of fruit powder with high sugar content
because it reduced the stickiness and agglomeration problems during
storage.

40. Dust Prevention
Dust generation can lead to a number of problems for food powders.
These can be summarised as follows:
(i) Health problems, in particular allergy problems;
(ii) (ii) contamination and plant hygiene issues due to dust settling and
sticking onto equipment; and (iii) fire/explosion hazards.
(iii) Sensors for measuring carbon-monoxide have been developed
and are already industrially implemented in the dairy industry

41. Changes during Storage
 Loss of vitamins
 Loss of natural pigments
 Browning reaction and rill of sulphrous groups
 Oxidative degradation and flavor loss
 Texture and reconstitute ability
 Glass transition point
 Microbiological hazard