Details description fmd

1. Ankan Kheto
Foam Mat Drying

2. Why Foam mat Drying
 Dehydration of heat-sensitive, high sugar content and viscous
foods, which are difficult-to-dry and sticky under relatively mild
conditions.
 Liquid food should be capable of forming stable foam.

3. Introduction
 Foam mat drying is special form of conveyor driers in which
liquid foods (usually fruit juices) converted to stable foam and
placed on a perforated conveyor.
 The foam is usually 2-3 mm thick and dried rapidly in two stages
by parallel and then counter current air flows.
 Vegetable (i.e. solubilized soya protein) protein, gum and various
emulsifiers (e.g. glycerol, monosterate and propylene glycol) are
used as foaming agents.

4. Process diagram for Foam Mat Drying
Cooler Heater
Screens Flaker
Dryer
Gas
Warm air
Moist
air
Concentrate
Dense Powder Dense Solid
Foam
Porous Solid
Containers
Foaming
agent
Hot liquid

5. Key parameters
 Stable gas-liquid foam is the primary condition for successful
foam drying.
 Surface area exposed is directly proportional to moisture
removal rate.
 Capillary diffusion is also the main reason for the moisture
movement within the product.

6. Foam
 Structure
 Colloidal dispersion in which gas is dispersed in a continuous liquid phase
 Dispersed phase (internal phase) is larger than the continuous phase (external
phase)
 Polyhedric foam
 Ratio of dispersed phase to continuous phase is larger
 Large number of bubbles and form a honeycomb structure
 Examples: Egg white foam and beer foam
 Dilute bubbly foam
 Ratio of dispersed phase to continuous phase is small
 Individual bubbles retain their spherical shape
 Examples: Choco mousse

7. Foam formation methods
 Sparging or bubbling:
 A known amount of air is bubbled through an orifice into a
known quantity of liquid
 Liquid may be completely converted to foam if a large amount of
gas is introduced
 Stability of the bubble formed highly depends on the viscosity of
the liquid
 This method manages the desired bubble size by adjusting the
diameter of the orifice
 This method is not used in food processing industries; however,
it is commonly used for basic foam studies

8. Contd..
 Whipping or beating:
 Incorporation of unlimited amount of air into known quantity of
liquid.
 The size of the air bubble will increase and subsequently break
into small bubbles because of the mechanical agitation.
 The final size of the bubble depends on the speed of the
agitator, the geometry of the apparatus and the rheological
properties of the liquid.
 Widely used in the food processing industries
 Electric hand blender takes about 3–5 min to obtain consistent
foam.

9. Contd..
 Shaking
 Foam is obtained by agitating the liquid forcefully.
 The volume of the foam formed by shaking depends on the
factors like the amplitude and frequency of shaking, shape of
the container, the volume, protein content and temperature of
the liquid taken.
 This method tends to be slower than by bubbling or whipping
under same conditions; hence, it is not commonly practiced on
large-scale foam production.

10. Foam Characteristics
 Foam Expansion (FE) = {(Volu of Foam - Initial volu of Pulp) /
(Initial volu of Pulp)} * 100
 Foam Stability = (Initial foam volu * time interval) / change in
foam volu
 Foam Density (g/cm3) = mass of foam / volu of foam
 Mechanical or thermal stability: Foam not collapsing for at least
1 hr.

11. Foaming Agents
 A surfactant that reduces the surface tension between two liquids
or between a liquid and a solid and facilitates the foam formation.
 It should be able to adsorb readily at the air-water interface,
reduce interfacial tension, withstand thermal and mechanical
agitation
 Foaming agents should posses the following properties
 Stabilize foams effectively and rapidly at low concentrations
 Perform effectively over the pH range
 Perform efficiently in the medium with foam inhibitors such as fat, alcohol
or flavor substances

12. Foam Stabilizers
 Decrease the instability of foams, polysaccharides are employed
as stabilizers.
 Being hydrophilic, they do not adsorb at the interface.
 Enhance the stability of foam proteins by a thickening or a gelling
effect.
 Act by either increasing the viscosity of the continuous phase or
by forming a 3D network that retards the movement of
components within the foam.
 Example: Cellulose gum, Xanthan gum, Arabic gum, Starches,
Pectins and Gelatin etc.

13. Types
 Continuous Foam Mat Dryer
 Continuous belt vacuum dryer for drying of milk foam, where the foamed milk
of 45% w/w solids was deposited on the stainless steel belt, tensed over
heating and cooling drums. Various combinations of radiant heaters were
placed above and below the belt to precondition the feed, and to dry the
product. Then, the dried product was scrapped from the belt, which rolled over
the cooling drum.
 Microwave Foam mat Drying (MFD)
 Foams are dried in a thin layer which resulted in limited throughput even in
optimized drying conditions, is a main drawback of the foam mat drying.
 Foam Mat Freeze-Drying
 Dehydrated products with excellent final quality because of the low
temperatures during the process and the direct sublimation of water from
solid to vapor states.

14. Advantages
 Rapid drying and low temperature of products results in high
quality product.
 Foam drying is three times faster than drying a similar type of
liquid.
 Considerably cheaper than vacuum, freeze and spray drying
method.
 Uniform heating, Storage reliability and Simplicity.

15. Disadvantages
 High capital cost (but lower than vacuum drying).
 Large surface area is required for high production rate.

16. References:
 Kudra, T. and Ratti, C. (2006) Foam-mat drying: Energy and cost analyses. Can.
Biosyst. Eng. 48, 3.27–3.32
 Mehran Azizpour , Mohebbat Mohebbi, Mohammad Hosein Haddad
Khodaparast .(2016) Effects of foam-mat drying temperature on physico-chemical
and microstructural properties of shrimp powder, Innovative Food Science and
Emerging Technologies ,34, 122–126
 Sangamithra a, Sivakumar Venkatachalam, Swamy Gabriela John and Kannan
Kuppuswamy. (2015), Foam mat drying of food materials: A review, Journal of Food
Processing and Preservation, 39, 3165–3174
 Z. Hardy & V. A. Jideani.(2017) Foam-mat drying technology: A review, Critical
Reviews in Food Science and Nutrition, 57:12, 2560-2572
 Ana María Chaux-Gutiérrez, Adriana Barbosa Santos, Diana Maria Granda-
Restrepo & Maria Aparecida Mauro. (2017) Foam mat drying of mango: Effect
of processing parameters on the drying kinetic and product quality, Drying
Technology, 35:5, 631-641

17. Thank You…..