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Qualitative Characteristics of Dahi Prepared Form Nonfat-dry Milk Fortified with Vegetable Oil

J. Begum
Department of Dairy Science, Bangladesh Agricultural University, Mymensingh

M.N. Islam
Department of Dairy Science, Bangladesh Agricultural University, Mymensingh

M.M. Rahman
Bangladesh Inland Water Transport Authority (BIWTA), Chittagong, Bangladesh

A. Nahar
District Artificial Insemination Center, Barisal, Bangladesh

Abstract/ Executive Summary:

In this experiment attempts were made to prepare dahi from non-fat-dry milk (NFDM) by adding vegetable oil and also to evaluate their qualitative characteristics. For this purpose 100. 150 and 200 gms of NFDM was dissolved in water in three different containers along with 40 gm of soyabean oil to make one litre milk of each type. The prepared samples were designated as A, B and C type milk. Whole milk was collected from BAU Dairy Farm and used as control sample. The control sample was named as 'D' type sample. Initial quality of all four types of milk samples were determined in the laboratory. There after dahi was prepared from each type of milk and during dahi preparation 5 gm of gelatin was added in each of three different reconstituted milk samples except whole milk. Quality of prepared dahi samples were measured with the help of some physical (smell and taste, body and consistency, colour and texture) and chemical (pH level, acidity percentage, total solids, fat content, protein content, ash content) tests. From the result it was found that the overall score of A, B, C and D type dahi samples were 78.20±4.02, 81.87±1.17, 84.70±1.30 and 92.03±2.29 respectively. The difference between them were statistically significant. On the other hand, mean value of total solids, fat, protein and ash content A, B, C and D type dahi samples were 330.1±8.5, 392.7±4.2, 455.9±7.6. 310.9±1.4 and 46.4±0.6, 48.6±1.7, 46.8±1.6, 55.9±1.4 and 60.1±8.5, 75±2.7, 101.6±1.8, 57.9±3.9 and 10.3±0.6, 12.9±0.1, 15.4±0.35, 8.8±0.15 g/kg respectively. Statistically the above parameters differ significantly. Finally it was concluded that acceptable quality dahi could be prepared from skim milk powder by adding vegetable oil and 200g of. skim milk powder per liter was found suitable which would produce dahi nearly similar to the quality of whole milk dahi.

Keywords: Dahi, Non-fat-dry milk, Vegetable oil and gelatin

Location: Dairy Science, Bangladesh Agricultural University, Mymensingh

Start Date: 04-08-2004

End Date: 30-10-2004

Program Area: Postharvest and Agro-processing

Commodity: Yogurt

Objectives:

1. To manufacture dahi from skimmed milk powder fortified with vegetable oil, 2. To recommend appropriate level of skimmed milk powder to be used for the manufacture of dahi, and 3. To compare the prepared dahi samples with that of dahi samples prepared from whole milk.

Methodology:

Site and period of experiment - The present experiment was conducted at the Dairy Science, Bangladesh Agricultural University, Mymensingh, during the period from 4 August to 30 October, 2004. Chemical analyses were done at the Dairy Technology laboratory, Department of Dairy Science and Fish Nutrition Laboratory, Department of Aquaculture, Bangladesh Agricultural University, Mymensingh. Collection of samples - Whole milk was collected from BAU Dairy farm Mymensingh and non-fat dry milk powder was collected from Bagha-Bari-Ghat Milk processing plant, Milk- Vita, Shahjadpur. Preparation of milk samples - For the preparation of different types of reconstituted milk 100, 150 and 200gm of skim milk powder was mixed separately in three different types of beaker in about 500 ml of water. When the content of each container dissolved completely then 40 gm of vegetable oil ( soyabean oil ) was added in each container. There after water was again added to the content of each container to make it one liter. Then finally mixed sample were properly blended by blending machine. Before blending the blender was cleaned and sterilized properly. In order to reduce the natural flavor of Soybean oil, 1-2 drops of vanilla flavor was added with each type of milk at the time of blending. The three samples were named as A, B and C type milk samples respectively. On the other hand whole milk collected from BAU Dairy Farm was treated as control sample and named as ‘D’ type milk. Chemical analysis - Before preparation of various types of dahi (from whole milk and different combinations of skim-milk with vegetable oil) initial chemical quality of whole milk and different combinations of skim-milk with vegetable oil was analysed in the laboratory to observe their quality. The following parameters were measured to observe their initial quality. - Specific gravity , Acidity (%), Total solids (g/kg), Fat (g/kg),Protein (g/kg), Ash (g/kg) Specific gravity test was performed by using Quevene Lactometer, according to the method described by Aggarwala and Sharma (1961). Acidity was determined by titrating with N/10 sodium hydroxide solution using the procedure of Aggarwala and Sharma (1961). Total solids and ash content of the milk samples were determined by oven drying method according to AOAC (1980). Fat percent was determined by Babcock method. Crude protein was determined by Kjeldhal procedure as described by AOAC. Dahi from whole milk The collected whole milk was heated to boiling temperature until reduced upto 20 to 25% of the volume of milk and also to destroy the viable organisms that were present in milk. At the time of boiling milk, sugar was added at the rate of 10 percent. During heating, milk was stirred thoroughly with the help of spoon. After desired heating milk pan was taken out from the heater and allowed to cool down to near 37°C and inoculated with 3% starter cultures collected from laboratory. After inoculation warm milk of 37°C was then poured into several preboiled water washed plastic cups and kept undisturbed at an incubation temperature of 37°C until complete coagulation. After complete coagulation (3.5-4 hrs. ), the dahi samples were taken out from the incubator and were stored in a refrigerator at about 5°C for analytical purpose. This type of dahi was identified as ‘D’ type dahi for analytical purpose. This type of dahi was identified as ‘D’ type dahi for the experimental purpose. Dahi from different levels of non-fat dry milk (10%, 15%, and 20% with the addition of 4% vegetables oil Milk samples were heated to boiling temperature to reduce their volume upto 20% to 25%. In order to improve the texture of dahi 0.5% gelatin was added with each milk samples during boiling. After desired heating (Volume was reduced to 25%) milk pan was taken out from the heater and allowed to cool down near 37°C and 3% culture was added and after that same procedure was followed for the preparation at different levels levels of powders milk based dahi which was used for whole milk dahi. These three types of dahi was designated as A,B and C type dahi respectively. Finally four different types of dahi which were prepared in this experiment were as follows: Dahi ‘A’ = 10% (100g/L) non-fat dry milk + 4% vegetable oil + 0.5% gelatin, Dahi ‘B’ = 15% (150g/L) non-fat dry milk + 4% vegetable oil + 0.5% gelatin, Dahi ‘C’ = 20% (200g/L) non-fat dry milk + 4% vegetable oil + 0.5% gelatin, and Dahi ‘D’ = Whole milk. Data analysis Design: Completely Randomized design (CRD) Replication: Three, Treatments: Four, Program: SPSS Data collected from this experiment were analysed to see the difference between treatments. For this purpose analysis of variance tests were done and in case of significant difference LSD tests were done to compare the difference between mean values of treatments.

Source of Information: BANGLADESH RESEARCH PUBLICATIONS JOURNAL; ISSN: 1998-2003, Volume: 6, Issue: 1, Page: 35-45, September-October, 2011

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

From the result it was found that the overall score of A, B, C and D type dahi samples were 78.20±4.02, 81.87±1.17, 84.70±1.30 and 92.03±2.29 respectively. The difference between them were statistically significant. On the other hand, mean value of total solids, fat, protein and ash content A, B, C and D type dahi samples were 330.1±8.5, 392.7±4.2, 455.9±7.6. 310.9±1.4 and 46.4±0.6, 48.6±1.7, 46.8±1.6, 55.9±1.4 and 60.1±8.5, 75±2.7, 101.6±1.8, 57.9±3.9 and 10.3±0.6, 12.9±0.1, 15.4±0.35, 8.8±0.15 g/kg respectively. Statistically the above parameters differ significantly. Finally it was concluded that acceptable quality dahi could be prepared from skim milk powder by adding vegetable oil and 200g of. skim milk powder per liter was found suitable which would produce dahi nearly similar to the quality of whole milk dahi.

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