Khoa Making Equipment

Khoa is a heat desiccated product and made by concentrating whole milk at atmospheric pressure, unlike concentration under vacuum in the milk evaporators.Milk is boiled and evaporated by stirring. The stirring and scraping is done to avoid milk deposits sticking on the heating surface. Initially the scraping is slow as the water content is high and the surface deposition is slow. At final stage, the intensity of scraping increases. The product is taken out in a high viscous and yet flowable form, as it is hot. The cooled mass gets solidified and is called ‘Khoa’.

i. Karahi

Traditionally khoa is made in the open vats, “Karahi” referred earlier. The Karahi offers advantages such as its availability, cost, extent of repair and maintenance,and versatility in use. This can use any heating source like coal, wood or Liquefied Petroleum Gas (LPG). Initially milk has large water content hence agitation/scraping is slow and intermittent. As the concentration increases the fouling of heating surface increases. Hence, vigorous scraping is required. Also the heat intensity is reduced progressively as the water availability for evaporation reduces. All these operations are performed manually and depended on the skill of the operator.

ii. Jacketed Kettle

Hemi-spherical jacketed kettle is shown in figure 3.14. Small entrepreneurs and dairies prefer this equipment. However, this unit has disadvantage of low capacity and the curvilinear profile which causes surface fouling. The scraping of surface,loading of raw milk and unloading of finished product is manual. This unit differs from ghee kettle primarily on the design of scraping mechanism, as the degree of scraping required is more for Khoa during its manufacture.

iii. Conical Process Vat

It is an improved version of Jacketed vessel developed at NDRI Karnal, for its scraping ability and product handling (Fig.3.15). This equipment has straight-line profile of the heating surface, hence, easy to scrap. The scrapers are motorized with speed regulation; hence, scraping speed can be varied in relation to the requirement of the product. Product is loaded from the top while it can be unloaded through an axial discharge mechanism. A batch type Scraped Surface Heat Exchanger (SSHE) is also placed in figure 3.16. This makes about 10-12 kg khoa per hour.

iv. Continuous khoa-making Machine

This machine is developed and perfected to manufacture 50-60 kg of Khoa per hour. An inclined scraper surface heat exchanger has been developed at National Dairy Development Board, Anand. Both of these units prepare khoa @ 45-50 kg per hour from raw milk and 300-350 kg per hour from condense milk. These units are required for large-scale manufacturing of khoa and are used mostly by established dairy plants.

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