Letter to the Editor Vishal Kumar*, Dinesh Rajak, Raushan Kumar, Vikash Kumar and Pratibha Devi Sharma Design and Development of Low-Cost Makhana Grading and Roasting Machine Abstract: The currently available technology of Makhana processing is not only indigenous and manual but also cumbersome and painstaking. The process involves hand- ling of hot roasted seeds which require two to three laborers to process 8–9 kg of popped Makhana per day. With the view to mechanize the unit operation involved in Makhana processing, grading and roasting machine were designed and developed. Grader was developed based on engineering properties of Makhana while the roaster was designed based on preliminary experiments for Makhana, i.e. shell breaking force at different temperatures and for varying residence time. The grader performed best at feed rate of 20 kg/h with grading effectiveness of 0.99, 0.955 and 0.95 for grade 1, grade 2 and grade 3 Makhana seeds respectively. The developed roasting machine worked satisfactorily with 100% popping efficiency at machine capacity around 23.0 kg/h. The residence time of seeds in the roaster was 2.6 min and the average temperature of roasted seeds of grade 1, grade 2, grade 3 was found to be 271.33°C, 281.1°C and 280.7°C respectively. Keywords: Makhana, grader, roaster, residence time, popping *Corresponding author: Vishal Kumar, Rajendra Agricultural University, Pusa, Samastipur, India, E-mail: vishal.cae@gmail.com Dinesh Rajak, Rajendra Agricultural University, Pusa, Samastipur, India, E-mail: dinesh_rajak@yahoo.com Raushan Kumar, Indian Institute of Technology – Roorkee, Roorkee, Uttarakhand, India, E-mail: raushan_kumar@yahoo.com Vikash Kumar, Indian Institute of Technology Kharagpur, Kharagpur, India, E-mail: kvikash44@facebook.com Pratibha Devi Sharma, Rajendra Agricultural University, Pusa, Samastipur, India, E-mail: pratibha_pusa@yahoo.com 1 Introduction Makhana, Euryale ferox, is considered a potential aquatic cash crop in India particularly in Bihar. Other than India, this unique product is grown in China, Nepal and Bangladesh. Edible part of Makhana contains 12.8% moisture, 9.7% protein, 0.1% fat, 0.5% minerals, 76.9% carbohydrates, and 1.4 mg/100 g of carotene. Calorific analysis gives a value of 362 kcal/100 g for raw Makhana and 328 kcal/100 g for popped Makhana [1]. Thus, the calorific value of Makhana compares well with staple food materials such as wheat, rice, etc. Although lacking in fats, Makhana is considered superior to dry fruits such as almonds, walnut, coconut and cashew nut in terms of sugar, protein, ascorbic acid and phenol content [2]. It has also significance with having natural precious medicinal values. Various human ailments such as respiratory, circu- latory, digestive, renal and reproductive system may get cured after regular Makhana consumption. Ayurveda (a traditional medicine native to the Indian subcontinent and a form of alternative medicine) mentions it to have spermatogenic and aphrodisiac properties [3, 4]. The traditional processing of Makhana, i.e. grading, roasting and popping of Makhana seeds is very tedious and back breaking work. The Makhana seeds are first graded, cleaned and dried manually. Grading is done so that the heating and impact force for pop making remain uniform. The nuts (Figure 1) are then preheated, tem- pered and roasted in a cast iron pan in single layer over the fire with continuous stirring. Within 2 min, a crack- ling sound is heard from the nuts being roasted. This is an indication of the optimum roasting of nuts. The roasted nuts, 5 to 7 in number, are scooped quickly by hand from the pan and kept on a hard surface and sudden impact force is applied on them by means of a wooden hammer. The workers involved in the operation usually burn their hands. As soon as the hard shell breaks, the kernel pops (Figure 2) out in expanded form, which is known as Makhana and shell splits are separated out manually [5]. No effort has been made to improve the process technology and to increase the capacity of Makhana pro- cessing. Although the method and sequence of operation in Makhana processing is known at domestic level, no scientific information regarding processing is available in literature. Thus, there is a need to study the basic pro- cesses involved, the properties of Makhana seeds and to doi 10.1515/ijfe-2013-0056 International Journal of Food Engineering 2014; 10(3): 357–366