The following extracts from the handbook Technology of Indian Milk Products would be of interest to Dairy & Food Technologists
Section 2.2 - Hygienic Handling of Raw Milk: Recommended Practices
Membrane Technologies (Pg 71)
Since the introduction of pressure-driven membrane separation processes,
intensive R&D efforts have led to the application of Reverse Osmosis
(RO), Ultrafiltration (UF), Microfiltration (MF) and Nanofiltration
(NF) in the dairy industry. R&D work indicates potential RO application
for concentration of milk for products like khoa and of UF application
for the manufacture of shrikhand, paneer and chhana. Application of
these processes permits higher energy saving, higher yields and superior
product quality compared to traditional processes of thermal evaporation.
Section 3.1: Desiccated
Innovations (Pg 103)
The Alfa-Laval group has developed a Contherm-Convap SSHE system
that has been successfully employed for the large-scale production
of khoa. Concentrated mass emerging from Convap at about 90°C
is pumped through a holding tube to impart characteristic flavour
The NDRI process for mechanized production of khoa employs two
SSHEs arranged in a cascade fashion. During khoa manufacture, milk
is concentrated to 65-69 per cent TS levels. During initial stages
of concentration (up to 45 per cent TS level), the capacity of the
system (kg of milk processed per hour per unit heat transfer area)
depends upon the mass-flow rate of milk, steam pressure, rotor speed
and number of blades.
Continuous khoa machine: An Inclined Scraped Surface Heat Exchanger
(ISSHE) was developed at the National Dairy Development Board (NDDB),
Anand, for continuous production of khoa. The plant comprises a
balance tank, a positive displacement pump and an ISSHE. Milk concentrate
is used as feed.
In industrial production of khoa, energy conservation is an important
consideration. Concentration of milk in an open pan is energy intensive.
Double effect evaporators or pressure driven membrane separation
process of Reverse Osmosis (RO) presents prospects for process upgradation.
Preservation of Khoa (Pg 106)
some research has been carried out to improve the shelf life
of khoa using preservatives, like nisin, potassium sorbate and sodium
and potassium metasulphites.
Khoa Powder (Pg 107 - 108)
Various processes tried for making khoa powder include reverse osmosis,
tray drying, spray drying, fluidized bed drying and roller drying.
Tray drying at atmospheric pressure: A flow diagram for
the preparation of khoa powder by tray drying process
*Drying is done for 4 hours under atmospheric pressure and for
3 hours under vacuum (25 inches of mercury).
Figure 3.1.2 Khoa powder production from buffalo milk by
tray drying (atmospheric pressure/vacuum)
Section 3.4: Fat-rich Products
Mechanized Manufacture (Pg 186)
Figure 3.4.2 Industrial process for continuous production
of ghee, with cream as starting material (Dr Punjrath)
Defects in Ghee (Pg 188)
Regarding rancidity in dairy products, hydrolytic changes are more
relevant than oxidative changes.
The fat splitting enzyme, lipoprotein lipase, is found in milk.
It is sensitive to heat and is destroyed by proper pasteurization.
Lipase activity can deteriorate milk flavour rapidly. Homogenized,
unpasteurized milk may become rancid in a matter of minutes. Even
a small contamination of pasteurized, homogenized milk with raw
milk gives a rancid flavour. Homogenizing the raw milk at 40°C
appears to give the greatest lipase activity.
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