Lesson 12. RABRI – PRODUCT DESCRIPTION, METHODS OF PREPARATION, YIELD, PACKAGING AND SHELF LIFE
Module 4. Rabri
Lesson 12
RABRI – PRODUCT DESCRIPTION, METHODS OF PREPARATION, YIELD, PACKAGING AND SHELF LIFE
Rabri is a sweetened concentrated whole milk product with thickened malai layer obtained by evaporation and concentration of milk. Buffalo milk is preferred for preparation of rabri.
12.2 Method of Manufacture
12.2.1 Traditional method
Whole buffalo milk is taken in a karahi and slowly heated at simmering temperature. The milk is not allowed to boil so that clotted cream may form on its surface. Slow evaporation of moisture takes place and the layer of resulting clotted cream is continuously removed with a fork and placed on the sides of karahi. When the volume of milk is considerably reduced, sugar @ 5-6 percent of milk is added and stirred. The clotted cream collected on the sides of the pan is gently added back to the sweetened concentrated milk. The clotted cream is broken into small bits by wooden ladle before addition to milk. Whole mass then appears to be concentrated sweetened milk with clotted cream. Higher the amount of clotted cream better will be the quality of rabri.
Fig. 12.1 Flow diagram for preparation of Rabri
12.2.2 Improved batch method
A small scale process was developed for the manufacture of rabri. The process includes heating of whole buffalo milk with 6% fat in a steam jacketed stainless steel kettle to 90-95˚C and holding at this temperature for some time without any agitation. The malai (pellicle) formed on the surface of milk may be removed in a separate container after every 10 min. After collecting about 500 g malai, the temperature of milk is raised to boiling. Pre-determined quantity of sugar (@ 6% on milk basis) is added to the concentrated milk and mixed well. Subsequently, malai collected in a separate vessel is added back and mixed. The product is then cooled to < 10˚C and served.
12.2.3 Large scale manufacture of rabri
Two types of concentrated milks were used as base materials for large scale production of rabri. In one process, buffalo milk with 2% fat was concentrated to 35% TS in a scraped surface heat exchanger. In another method buffalo skim milk was concentrated in a vaccum pan to contain 35% total solids.
The concentrated milks were heated upto 90˚C followed by addition of sugar @12% of the product. The mixture was then cooled to 70ºC and calculated amount of malai is added to it. The malai could be prepared from buffalo milk by simmering it in an open kettle. However rabri obtained by these two methods was liked ‘slightly’ by judges indicating necessity for further improvement in the process.
12.3 Chemical Composition
Chemical composition of rabri depends on initial quality of milk, type of milk, degree of concentration, quantity of sugar added and method of manufacture.
Table 12.1 Chemical composition of rabri
12.4 Microbiological Quality of Rabri
Microbiological quality of rabri that is sold in market is given in Table 12.2.
Table 12.2 Microbiological quality of rabri
It was observed that rabri having slightly cooked flavor and pleasant sweet creamy taste is liked most by the consumers. The samples having more layers of malai along with some liquid portion were rated high in market. Rabri samples having light yellow and white colour with slight tinge of browning are more preferred by the consumers.
12.6 Changes in Milk during Manufacture of Rabri
The following changes occur in milk due to prolonged heating during preparation of rabri.
• The viscosity of milk increases
• There is a gradual lowering of pH with corresponding increase in acidity of the product.
• Minerals, specially calcium and phosphorus get trapped in clotted cream part.
• Depending on the intensity and duration of heat treatment, browning intermediates are formed in varying degrees.
• Due to release of -SH groups, a cooked flavor develops in the product.
• A considerable loss of heat sensitive vitamins occurs during the preparation of the product.
• Both casein and whey proteins get denatured as a function of heat and increased concentration of total solids.
• There is a gradual lowering of pH with corresponding increase in acidity of the product.
• Minerals, specially calcium and phosphorus get trapped in clotted cream part.
• Depending on the intensity and duration of heat treatment, browning intermediates are formed in varying degrees.
• Due to release of -SH groups, a cooked flavor develops in the product.
• A considerable loss of heat sensitive vitamins occurs during the preparation of the product.
• Both casein and whey proteins get denatured as a function of heat and increased concentration of total solids.
12.7 Yield
Yield of rabri depends on total solids of milk, ratio of concentration of milk and amount of sugar added. In general 25-28 per cent yield can be expected from buffalo milk.
12.8 Shelf Life
Rabri can keep well for about 2-3 days at room temperature and 10-15 days at refrigeration temperature.
Reference
1) Gayen,D. and Pal,D.(1991) studies on the manufacture and storage of rabri.Indian J. Dairy Sci.44(1): 84-88
Last modified: Wednesday, 26 September 2012, 8:56 AM