Characteristics of spray dried dahi powder

containing 100% dahi .

that maltodextrin concentration has significant effect

on TS of reconstituted dahi powders.

Viscosity

Viscosity is the important rheological property in

Survival Rate of lactobacilli during spray drying

case of dahi and the values ranges from 800-920 Cp

As dahi used for spray drying was prepared once

in freshly prepared dahi (Rathi et al, 1990). It has

in bulk and then maltodextrin was added after

been reported that most of the aroma compounds

incubation at various levels, the initial count of

and rheology (viscosity) of yoghurt are lost during

lactobacilli in all dahi samples was remains constant

spray drying process (King, 1994). Results shows

and it was 2.1 × 10 7 cfu/ml. The parameters for spray

that viscosity of reconstituted dahi without added

drying of dahi samples were adjusted so that the

maltodextrin was 12.5 Cp and as the maltodextrin

outlet temperature remains constant i.e. at 70 o C.

concentration increases the viscosity of reconstituted

The powder from cyclone separator was collected

dahi also increases. Highest viscosity obtained was 62

and used for lactobacilli count. Table 1 shows colony

Cp for the sample containing 87.5% dahi and 12.5%

count and survival rate for reconstituted dahi

maltodextrin. These values indicates that there is

powder. The survival rate was calculated by using

much more losses occurred in rheological properties

following formula

of spray dried dahi powder as compared to other

methods such as freeze drying in which viscosity

The survival rates for the other samples containing 5,

of dahi ranges from 100-150 Cp (Rathi et al, 1990).

7.5,10 and 12.5% maltodextrin were 0.6, 0.62, 0.5 and

This shows that maltodextrin concentration has

0.4% respectively. The samples containing 5 and 7.5%

significant effect on viscosity of reconstituted dahi

maltodextrin shows somewhat more survival rate

powders (p < 0.05).

than the sample without added maltodextrin. This

may be due to encapsulating effect of maltodextrin

Total Solids (TS)

(Oldenhof et al., 2005). The survival rate for the

samples containing 10 and 12.5% maltodextrin are

TS of dahi without addition of maltodextrin were 12%.

0.5 and 0.4% respectively, may be because of less

The TS of reconstituted dahi samples increases as the

moisture content of powder from which they were

maltodextrin concentration increases. Results shows

reconstituted. These results are in conformation with

the research of previous workers (Kim and Bhowmik

1990).

Table 3. Survival rate, viscocity, acidity, wettability and TS test results of the solutions of spry dried dahi powders

Outlet air temperature

MD content

Survival Rate

Viscosity

Acidity (%

Wettability

TS (%)

( o C)/blower speed (rpm)

(%)

(%)

(Cp)

lactic acid)

(s)

0

0.5±.2

12±.3

0.936±.3

178±.2

12.0±.3

5

0.60±.3

25±.4

0.936±.1

230±.4

16.5±.4

70 o C /2200

7.5

0.62±.4

38±.5

0.918±.4

270±.4

19.1±.5

10

0.5±.5

50±.2

0.900±.6

290±.5

21.2±.3

12.5

0.4±.5

62±.3

0.900±.3

300±.3

23.9±.4

Note: rpm = rotation per minute, MD= maltodextrin

Survival rate, Viscocity, Acidity, Wettability and TS values are mean ± standard deviation.

859