Slide 1

Chaughule, Thorat - Statistical Analysis/Design of Experiments

because the number of experiments is reduced as compared to a full factorial design (for
three variable system, 15 in the case of CCD compared to 27 for a full-factorial design).
Generally, for a large number of variables, the number of experiments grows exponen-
tially and becomes impractical. A full factorial design typically is used for five or fewer
variables. Factorial designs and CCD can be used for fitting second-order models. A
second-order model can significantly improve the optimization process when a first-
order model suffers lack of fit due to interaction between variables and surface curva-
ture. A general second-order model is defined as:

Andrade and Flores, 2004 have used RSM for optimization of spray drying of Roselle
extract (Hibiscus sabdariffa). Optimization of spray drying process for Inulin obtained
from chicory root extract was done by RSM by Nogueira et al. (2000). Brodhead et al.
(1994) have suggested the use of multifactorial approach using factorial and or compo-
site design because of the number of the effects involved in spray drying. Table 8.3 lists
some of the different application of CCD in Food dehydration (Mason et al., 2003; Antony,
2003 ; Montgomery, 2003).

Table 8.3. Applications of statistical designs for food dehydration in the literature

Reference Design Drying material

& method

Factors & levels Response

Koc et al,

2010

Central

Composite

rotatable

design

(CCRD)

Spray drying of

yogurt for deter-

mination of opti-

mum processing

conditions

The inlet (150-180°

C) and outlet air

temperatures (60-

90° C) and the feed

temperature (4-30°

C)

Maximum survival

ratio of lactic acid

bacteria, maximum

overall sensory

attributes, minimum

color change, and ac-

ceptable moisture

contents

Jadhav et al.,

2010

RSM, central

composite

design

Optimization of

pretreatment

prior to solar cab-

inet drying of

green peas.

Blanching time (1- 5

min) and potassium

metabisulphite

(KMS) concentration

(0.2-0.5%)

Color, hardness, re-

hydration ratio,

shrinkage, overall

acceptability

Han et al.,

2010

RSM, ortho-

gonal rotat-

able central

composite

design

Optimization of

process parame-

ters for micro-

wave vacuum

drying of apple

slices

Microwave power

(8-16 W/g) , vacuum

level (0.075-0.095

MPa) , and initial

moisture content

(0.3-1 kg/kg db)

Drying time, sensory

quality and porosity.

Giri & Prasad

2007

RSM Optimization of

microwave-

vacuum drying of

button mu-

shrooms

Microwave power

level (115 to 285 W),

system pressure (6.5

to 23.5 kPa), and

slice thickness (6 to

14 mm)

Color, texture, rehy-

dration ratio, and

sensory attributes

Birchal et al,

2005

Full factorial

design

Optimization of

conditions for

spray drying of

milk

feed flow rate, the

atomization rotation

and the inlet air

temperature

Residual moisture

content, tapped bulk

density, cohesion

force enhancement