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Effect of Different Levels of Volume Reduction of Skim Milk on the Storage Life of Dahi Prepared from Cows Milk

M. J. Uddin
Scientific Officer
Biotechnology Division, Bangladesh, Livestock Research Institute, Savar, Dhaka-1341, Bangladesh.

M. R. Hassan
Bangladesh Livestock Research Institute, Biotechnology Division, Savar, Dhaka-1341.

S. Ahmed
Bangladesh Livestock Research Institute, Biotechnology Division, Savar, Dhaka-1341.

M. Asaduzzaman
Bangladesh Livestock Research Institute, Biotechnology Division, Savar, Dhaka-1341.

Abstract/ Executive Summary:

This study was conducted to measure the feasibility of using skim milk to evaluate the storage life of dahi at room temperature (31-32°C) and refrigeration temperature (5°C). In this experiment, five different types of dahi were prepared from whole milk and skim milk with volume reduced, the dahi samples were designated as A, B, C, D and E. All the dahi samples were stored at room temperature and refrigeration temperature. Quality of dahi was also monitored by using physical (smell and taste, body and consistency, color and texture) and chemical (acidity) tests. From the result of the physical study, it was found that the score of A, B, C, D and E types of dahi samples statistically differ significantly kept at room temperature and at refrigeration temperature. In case of chemical tests, acidity value of dahi samples kept at room temperature and at refrigeration temperature differ significantly. It is evident that, concentrated skim milk (volume reduced by 30-40%) is better. But very high concentration (volume reduced by 50%) deteriorates the quality of the product. On the other hand, low concentration (volume reduced by 20%) is not so acceptable. Finally, it is concluded that storage life was relatively longer when 30-40% skim milk volume was reduced to prepare dahi. The findings of the current research can be used by the commercial dahi producers to manufacture dahi having low cost and high storage period.

Keywords: Dahi, Storage life of, Skim milk, Levels of volume reduction

Location: Dairy Technology Laboratory, Department of Dairy Science, Bangladesh Agricultural University (BAU), Mymensingh.

Start Date:

End Date:

Program Area: Postharvest and Agro-processing

Commodity: Yogurt

Objectives:

1. To assess the keeping quality and storage life of prepared dahi at different levels of volume reduction of skim milk.

2. To compare the physical and chemical characteristics of dahi prepared from different levels of volume reduction of skim milk both at room temperature and refrigeration temperature.

Methodology:

The concerned experiment was carried out at the Dairy Technology of the Department of Dairy Science, Bangladesh Agricultural University, Mymensingh. Whole milk was collected from BAU Dairy Farm, Mymensingh. Skim milk: Skim milk was collected from whole milk by separating cream with the help of a cream separator. At first the whole milk or skim milk collected from dairy farm were weighted and heated to boiling temperature until reduced by 20% of the volume of milk. Sugar was added to the milk at the rate of 1 0% at the boiling time of milk. Milk was stirred thoroughly during heating with the help of a stirrer. After desired heating the milk pan was taken out from the heater and then the warm milk was kept for some time to cool down near 42ºC and inoculated with 3% starter cultures collected from laboratory. After inoculation warm milk of 42ºC was then poured into several plastic cups which were washed by pre-boiled water. Then the cups were kept undisturbed at an incubation temperature of 37ºC until complete coagulation. After complete coagulation (4-5 hrs), the dahi samples were taken out from the incubator and were stored in a refrigerator at about 5ºC for analytical purpose. Five different concentration of dahi were prepared from skim milk. The prepared dahi samples were preserved at ordinary room temperature (31-32°C) and refrigeration temperature (about 5 ºC) in the laboratory until spoilage to monitor their storage life. To observe the storage life, firstly prepared dahi samples were divided into two groups, having all five kinds of dahi in each group. There after, one group was kept in the laboratory at room temperature and other group was kept in the laboratory refrigerator at the temperature about 5 ºC The quality of dahi kept at room temperature were measured 12 hours interval, on the other hand, quality of refrigerated dahi was measured every day upto 16 days. Data collected from different parameters were subjected to statistical analysis in Completely Randomized Design (CRD) where there are 3 replication and 5 treatments. Data collected from the experiment statistically analyzed by using the MSTAT statistical program. Analysis of variance test was done to find out the statistical difference between the treatments. The difference among treatments means were compared by Latin Square Design (LSD).

Source of Information: Bangladesh Journal of Livestock Research, Vol: 13 (1 & 2), PP: 46-55, 2006, ISSN: 1022-3851

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Considering all the parameters studied this experiment, it may be concluded that, skim milk can successfully be used to prepare good quality dahi and at the same time it can be stored properly at room temperature (32ºC) and refrigeration temperature (5ºC). It is evident that, concentrated skim milk (volume reduced by 30-40%) is better. But very high concentration (volume reduced by 50%) deteriorates the quality of the product. On the other hand, low concentration (volume reduced by 20%) is not so acceptable. The findings of the current research can be used by the commercial dahi makers to manufacture dahi having low cost and high storage period. It will make this exclusive food item available to many of our poor people as well as open a good way to use the skim milk that comes as a by product from the creamery.

Knowledge Management: Journal