COURSE CODE : FST 4822

COURSE NAME : LABORATORY FOR CHEMISTRY AND TECHNOLOGY OF PLANT AND ANIMAL

EXPERIMENT NO. : 1 (DAIRY)

EXPERIMENT TITLE : PROCESSING OF DADIH

GROUP NO. : 1

GROUP MEMBERS :

TAN YIH YING 147732

SOON HONN KEONG

FONG PUI KUAN

CHOW SOOK YEE

OON XIAO YI

TAY PEI YIH

148820

149352

148485

149250

148201

HANITA HANIM MOHD ALI

MARDHIAH SUAIDAH BT SHAFIE

HANIS NADIA YAHYA

SITI NORLELA BINTI MOH SALLEH

149217

146573

150897

146106

LECTURER: DR. SEYED HAMED MIRNOSSEINI

INTRODUCTION

Dadih is a dairy product produced by bacterial fermentation of milk. The bacteria used to make dadih

are known as "yoghurt cultures". Worldwide, cow's milk is most commonly used to make yoghurt, but milk

from water buffalo, goats, sheep, camels and yaks is also used in various different parts of the world. In

theory the milk of any mammal could be used to make yoghurt. Soya yoghurt, a non-dairy yoghurt

alternative, is made from soy milk; this is not an animal product, being made from soy beans.

Dairy dadih is produced using a culture of Lactobacillus delbrueckii subsp. bulgaricus and

Streptococcus salivarius subsp. thermophilus bacteria. In addition, Lactobacillus acidophilus, Lactobacillus

bifidus and Lactobacillus casei are also sometimes used in culturing dadih. The milk is first heated to about

80 °C to kill any undesirable bacteria and also to denature the milk proteins so that they set together rather

than form curds. The milk is then cooled to about 45 °C. The bacteria culture is added, and the temperature

is maintained for 4 to 7 hours to allow fermentation. (Coyle, 1982).

Dadih can be easily prepared at home. To produce a quart of dadih, a quart of milk is heated

(generally to 180 °F or 80 °C) and then cooled to approximately 110 °F or 43 °C. An inexact test for the

temperature is to test it with a finger: if the finger can be left in the milk for ten seconds, the milk is at about

the correct temperature. Once the milk has cooled, a tablespoon of yoghurt containing live active cultures is

added to the scalded milk and mixed well. The dadih is poured into a container and incubated for the desired

length of time. The fermentation time depends on the desired texture and tang in the final product. A shorter

period yields a slightly runnier product with a mildly sour flavor, while a longer period yields thicker and

tarter dadih. (Najmieh, 2007).

Result:

A) Chemical Analysisi. Viscosity

Table 1: Viscosity of

Formulation A

Table 2: Viscosity of Formulation BFormulation B

1 2 Mean ±SDT (°C) 24.80 24.50 24.65 ± 0.2121Η ( mPa T) 47.20 35.80 41.50 ± 8.0610 [ pa] 73.16 55.46 64.31 ±12.5158

[1/s] P 1550.90 1550.90 1550.90 ± 0.0000

Table 3: Viscosity of formulation CFormulation C

1 2 Mean ± SDT (°C) 24.00 24.40 24.20 ± 0.2828Η ( mPa T) 20.20 19.70 19.95 ± 0.3536 [ pa] 31.26 30.63 30.95 ± 0.4455

[1/s] P 1550.90 1550.90 1550.90 ± 0.0000

Table 4: Viscosity of formulation DFormulation D

1 2 Mean ± SDT (°C) 24.20 24.60 24.40 ± 0.2828Η ( mPa T) 13.80 14.90 14.35 ± 0.7778 [ pa] 21.46 23.18 22.32 ± 1.2162

[1/s] P 1550.90 1550.90 1550.90 ± 0.0000

Formulation A1 2 Mean ± SD

T (°C) 24.50 24.40 24.45 ± 0.0707Η ( mPa T) 17.40 17.40 17.40 ± 0.0000 [ pa] 26.98 26.92 26.95 ± 0.0424

[1/s] P 1550.90 1550.90 1550.90 ± 0.0000

B) Sensory Evaluation

Types of

Formula-tion

Taste

Mean±SD

Flavour

Mean±SD

Overall acceptability

Mean±SDG1

G2

G3

G4

G1

G2

G3

G4

G1 G2 G3 G4

A1 1 3 1 1.50±1.00

03 3 4 4 3.50±0.57

71 2 3 2 2.00±0.81

7

B2 3 3 2 2.50±0.57

74 3 3 3 3.25±0.50

03 3 3 3 3.00±0.00

0

C4 4 3 3 3.50±0.57

72 2 2 3 2.25±0.50

03 2 2 3 2.50±0.57

7

D2 1 2 1 1.50±0.57

73 3 3 2 2.75±0.50

02 2 2 2 2.00±0.00

0

Table 5: Sensory Evaluation of Dadih

Scale:1: Worst 2: Bad 3: Normal 4: Good

Formulation A Formulation B Formulation C Formulation D

Figure 1: Dadih of Different Formulations

Discussion:

The dadih is prepared by using the acid method. The citric acid was used as the acidic medium. Citric

acid has various functions. It contributes refreshing taste to many foods and helps to prevent microbial

growth which can cause spoilage, and finally acts as a chelating agent, and its salts act as buffers that

stabilize pH (D.M.A Manan et al, 1998). Citric acid can introduce the sourness to the yoghurt. Besides, the

citric acid causes the textual changes by reacting with the casein protein in the milk to form coagulation.

Coagulation increases the viscosity of the dadih (Richard, 1962).

Generally, stabilisers or emulsifier such as gum are used during the manufacture of some dairy

product, but in dadih only stabilisers are added to the milk base. The primary aim of adding the stabilisers to

the milk base is to enhance and maintain the desirable characteristic in dadih such as texture and viscosity. It

also can refer as hydrocolloid and their mode of function in dadih includes first, the binding of water and

second promotion of an increase in viscosity. Thus, the molecules of the stabilisers can form a linkage

between milk constituents. Another factor which determines the level of stabilisers added to the dadih milk

is the percentage of milk solid present. The effect on the casein of some hydrocolloids such as gum that used

in experiment can stabilise the casein micelle (Tamime and Robinson, 1999).Tamime and Robinson (1999)

also explained that the binding water into milk base is achieved by stabiliser is it binds the water as water of

hydration. It also reacts with the milk constituents (mainly the proteins) to increase their level of water

hydration. Besides, it also stabilises the protein molecules in the form of a network that retards the free

movement of water. Therefore, the functions of hydrocolloids in dadih are as gelling or thickening agents

and stabilising agents.

According to the result, the viscosity of the dadih is decreasing from formulation B, C, A, and finally

to formulation D. However, from the experiment, the hydrophilic colloids bind water and consequently

increase the viscosity of dadih and also help prevent the separation of whey from dadih. Thus, it is able to

contribute the good coagulation property. The dadih formulation B had shown the highest viscosity in the

result while the formulation D shows the lowest viscosity. The formulation D is added 1 litre of water to

dilute the milk powder and thus it consequently decreases the viscosity of the dadih. Besides that, the dadih

for formulation D also added the least amount of gum which is only 0.1% of gum compare to formulation B

and C. Theoretically, the formulation C supposing to have highest viscosity rather than formulation B

because it is added the highest amount of gum which is 0.5% as the stabilisers in the dadih which can

increase the viscosity. Yet, it shows the second higher viscosity in the result. It may due to the human error

during experiment. The inaccuracy in measurement of amount of gum would affect the texture and viscosity

of the dadih.

From the result of sensory evaluation, the flavour of formulation B was much more preferred than

the other three formulations and this is mainly due to the different amount of stabilisers added in dadih. The

taste of formulations B, C and D was rated equally higher than that of formulation A. The taste was mainly

contributed by the coagulation compounds present in the dadih which is the stabilisers and other compounds.

The gum is used to increased the viscosity and gel formation of the dadih. The overall acceptability of the

dadih made from formulation B was the highest rated followed by formulations C, D and A which is 3.00

followed by 2.50, 2.00 and 2.00 respectively. The formulation A get the lowest acceptability because there is

not stabilisers added to the dadih. The poor texture is produced in the formulation A dadih. Meanwhile, the

formulation D also gives the poor acceptability due to the use of milk powder in processing dadih. The dadih

produced by liquid milk will have smooth texture compare to the dadih produced using the milk powder.

The most beneficial quantity of stabilizer to add to dadih has to be determined experimentally by each

manufacturer. This is because excess amount of stabilizer would contribute rubbery texture and hard solid

mass.

Conclusion

In this experiment, the added citric acid helps to increase acidity of dadih, which helps to prevent

microbial growth, provide buffering capacity due to presence of ions in the solution and also introduce sour

taste to the dadih. From the result, dadih with the formulation D has the lowest viscosity while dadih with

formulation B has the highest viscosity. The viscosity is affected by the amount of gum added to the dadih.

However, there is human error that affects the accuracy of the result of viscosity. Dadih with formulation B

is supposed to have the highest viscosity. In conclusion, the different amount of gum used in the dadih

processing will have different effect on the physical property and sensory attributions of dadih. In this

experiment, dadih produced by using formulation B has the best overall acceptance compared to other types

of formulation.

APPENDIX

Refferences

1. Coyle, L. Patrick (1982). The World Encyclopedia of Food. Facts On File Inc.. p. 763. ISBN 978-

0871964175. http://books.google.com/books?id=iuPJlbBOst8C. Retrieved 11 August 2009.

2. D.M.A Manan et al, (1998), Lactose content of modified enzyme-treated dadih, Food Chemisty

Volume 65, Issue 4, June 1999, Pages 439-443

3. Najmieh (2007). A Taste of Persia: An Introduction to Persian Cooking.

4. Richard, F.D. (1962), Modern Dairy Cattle Management Prentice Hall-Inc- Dadih, pg. 238.

5. Tamime, A.Y. & Robinson, R.K. (1999). Yoghurt: Science and Technology (2nd ed.) Woodhead

Publishing Ltd. pp. 36-40.