274 INTRODUCTION hoa is partially dehydrated, heat desiccated milk product and it is widely used as a base material for preparation of numerous indigenous sweets. The increasing demand of khoa based indigenous sweets has created need for large scale industrial production, ensuring uniform product quality, product safety, energy conservation, etc. Development of an industrial scale khoa making plant has been a challenge to dairy scientists since several years. Many efforts have been made in mechanization of khoa making process to improve heat transfer and also to overcome the drawbacks of traditional methods as well as to commercialize the process for industrial requirements. Extensive studies were also carried out on the hydrodynamics and heat transfer of thin film scraped surface heat exchanger (TFSSHE) for processing of liquid, concentrated liquids, and particulate viscous foods. Studies were also undertaken on the applicability of thin film scraped surface heat exchanger (SSHE) for the mechanization of khoa. According to PFA rules, revised in 2002, khoa is a product obtained from cow or buffalo milk or a combination thereof by rapid desiccation and having not less than 30% fat on dry matter basis of the finished product. According to Indian Standards (IS: 4883-1980), khoa shall be heat coagulated milk-product obtained by partial dehydration of milk of buffalo, cow, sheep, and goat or their admixture. Milk solids suitably processed may also be used. It shall not contain any ingredient foreign to milk except citric acid in danedar khoa added to develop desirable characteristic. A large variation in quality of market surplus indicates three major varieties of khoa viz. pindi, dhap and danedar. Chemical composition, sensory characteristics and end uses of such varieties are found to be different. These varieties of khoa are received in Delhi market, which is the biggest khoa marketing centre in the country today. These types of khoa differ in quality and also in price. All of these varieties are in demand and are required for specific types of sweets as shown below (De, 1980). Gross composition and specific sweets prepared from different khoa is given in Table-1. The work on continuous khoa making machine gained momentum in recent years as a result of greater emphasis laid for the manufacture of indigenous milk products in the organized sector. For handling high viscosity products with or Mechanized Manufacture of Danedar Mechanized Manufacture of Danedar Mechanized Manufacture of Danedar Mechanized Manufacture of Danedar Mechanized Manufacture of Danedar Khoa using Thr Khoa using Thr Khoa using Thr Khoa using Thr Khoa using Three Stage S ee Stage S ee Stage S ee Stage S ee Stage SSHE SHE SHE SHE SHE * Dairy Engineering Division, NDRI, Karnal 132001 Haryana 2012-045 Received:October 2011; Accepted:July 2012 A.K.Dodeja and Ankit Deep National Dairy Research Institute, Karnal-132001 (Haryana) The present investigation is undertaken to explore the feasibility of three stage SSHE for manufacture of danedar khoa. Trails were conducted to optimise the process parameters such as initial acidity of milk, mass flow rate, steam pressure and scraper speed. Initial acidity of milk was varied from 0.16 to 0.19% LA. The mass flow rate was varied between 170 to 210 kg/h. Three levels of scraper speed were taken in first, four levels in second stage and three levels in third stage i.e. 200, 175 150 rpm, 200, 175, 150, 125 and 25,20,15 rpm respectively. The quality of danedar khoa so produced was evaluated in terms of sensory evaluation and textural profile analysis. The best quality of danedar khoa was prepared by using standardized milk with 0.18% LA initial acidity and keeping scraper speed 175, 150, 15 rpm for first, second and third stage SSHE and flow rate 190 kg/h and steam pressure 4, 2 and 1.5 kg/cm2. Keywords: Scraped surface heat exchanger (SSHE), Danedar Khoa, heat transfer coefficient Research Article K