Refractance Window® Dryer (Model 5 33m long)

Uses hot water which is reheated to

improve efficiency;

Relatively low product temp. (~70°C);

Short drying times: 3-5 min;

Modular design, Continuous operation

Handles most liquid products without the

need for a non-sugar carriers

Retains color & nutrients

Unique Features of RW Drying

Refractance Window Drying - a novel contact surface drying system

Drying of Different Products

Fruits (blueberry, raspberry, grape extracts, mango etc), Vegetables incl. asparagus, carrots, squash; Herbal products (spices, teas, aloe vera) Marine resources (algae, carotenoids); Other products for food, nutraceutical & pharmaceutical

uses.

Method of Refractance Window® Drying

Water vapor

Hot water tank

Endless polyester belt

Circulating hot

water

Cooling

section Dried product Product

application

Heating section

RW Drying Analysis

Air

Water

Product

Control

Volume

radq airconvq

OHconvq2

condq

evpq

Air

Water

Product

Control

Volume

radq airconvq

OHconvq2

condq

evpq

(1) outinrate EEE

aconvevpradwconvcondrate qqqqqq (2)

q" is heat flux in W/m2

(3) aconvevpwconvrate qqqq

Energy balance

zero zero

Heat/mass quantity Eqn. #

Convective heat from water to

product, q”conv(w)

= hw (Tw –T1) (4)

Convective heat loss from

product surface, q”conv(a)

= ha (T2 -Ta) (5)

Evaporative heat loss, q”evap = (L /A) dM/dt (6)

Blue-Green Algae

Grape Extract

Haematococcus Pluvialis

Carrot

Color Quality of Dehydrated Products

Spray-dried green algae

Aquatic Resources

Preparation of fresh puree

Application of Puree on belt

Flaky product ejecting from dryer

RW Drying of Vegetables

Drying of Pumpkin Puree

RW Drying of Asparagus Soup Mix

Spray feeding of small volume samples

Dried Product

Drying Section , DS

Cooling Section, CS

Inner-side

Center

Outer-side

Blower 1 Blower 2

Computer

Use LabView

Data Logger Ambient air

Hot water Inlet

Hot water Inlet Hot water Outlet

Cold water

Outlet Cold water Inlet

Inlet, 0 DS12 DS24 DS36 DS48 DS60 DS72 End

Temperature record setup

MC = 3.055% (wb)

Freeze dried mango

0.25 MD 0.35 MD 0.45 MD

Spray & Drum Drying of Mango

Drum drying

0

10

20

30

40

50

60

70

80

90

Pi DS12 DS24 DS36 DS48 DS60 DS72 Pf

Mo

istu

re C

on

ten

t, %

BS at 0.007 m/s BS at 0.009 m/s

Drying section

RW Drying Curve

MC = 1.64 %, wb

Drying time,

min

MC

(%wb) Tgi Tgm Tge

5.5 1.64 18.45 21.28 24.28

4.25 2.49 17.96 22.05 25.26

3.52 4.20 12.78 15.63 17.58

Water vapor

Hot water tank

Endless polyester belt

Circulating

hot water

Cooling

section

Dried

product

Product

application

Heating section

Tg & RW Drying

Current Research Activities in Food Engineering Lab 129

• Novel Food Drying Methods Refractance Window Drying

Combination Drying (for energy efficiency)

• Extraction of anthocyanins & bioactives from berries

Power ultrasound, Electromagnetics

• Rheological & Thermomechanical properties of foods Controlled stress-strain rheometry (fluids)

Viscoelastic properties of solid foods (biofilms)

• Thermal properties of foods Modulated DSC (Glass transition studies)

Rheological & Thermomechanical Analysis of Food

Dynamic Mechanical Analyzer

• Rheometer – measures both viscosity and viscoelasticity of fluids, semi-solids and solids

• It provides information about the material’s:

Viscosity – function of shear rate or stress, time & temperature dependence

Viscoelastic properties (G’, G”, tan ) with respect to time, temperature, frequency, stress and strain

Transient responses (relaxation modulus, creep compliance, creep recovery)

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0 10 20 30 40 50 60

Temperature (°C)

Vis

cosi

ty,

Pa

s

FreshGel

FD

RW

SD

Viscosity of fresh aloe gel compared to gels reconstituted from powder

Q200 DSC

Current Applications:

• Tg of fish gelatin films and

dehydrated products;

• Properties of wheat & potato starch;

• Properties of food packaging materials