The present invention relates to a mechanized system for primary roasting of raw makhana seeds of uniform size and a process of roasting for further production of popped makhana. The invention also relates to develop an alternate of drudgery and injury prone manual roasting process.
This invention aims to increase the fuel efficiency of primary roasting with increased capacity using LPG gas as heat source in place of firewood. The process for primary roasting of makhana seeds for production of popped makhana was investigated and optimum conditions for roasting were developed.

Prior art
Processing of makhana seed to produce popped makhana involves a series of unit operations as described in the flow diagram (Figure 1).
At present all the unit operations of makhana processing are performed manually. Further a machine for final roasting and popping operations was developed and manufactured commercially Patent no. 674/BEL/2013; Mechanized system for popping and decortication of makhana seed (gorgun nut), Euryale ferox. The main purpose of primary roasting of raw makhana seeds is the gelatinization of all starch present in the kernel.
Still the primary roasting operation is done manually. In manual primary roasting operation, 1-2 kg raw makhana seeds of uniform size are placed into iron pan. Heating of the pan is done using firewood. The seeds are continuously agitated while roasting. Completion of the roasting is identified by taking out some seeds and breaking them to check whether the starch present in the core of kernel is gelatinized. The process is cumbersome, involves drudgery with low fuel efficiency. A machine was developed for primary roasting of makhana seed by M/s Jwala Engineering & Consultancy Services, Ambala. The machine consist of double wall cylinder placed horizontally, which is heated by thermic oil with energy requirement of 18 kW and 6-7 kg seeds can be fed in one batch. An agitator is placed in the inner cylinder to mix the seeds during roasting. The outlet is opened and closed by pneumatically operated pistons. The roasting is not uniform in the machine and cases of fire hazards were observed frequently. Further, there is no mechanism to identify the completion of roasting because sampling cannot be done. Commercial roasting machines for different commodities, such as wheat, coffee beans, groundnut, rice, and hazelnut are available. Gas-solid fluidized bed roaster is used for wheat roasting at temperature range of 280-350 ºC for 30-45 s. Coffee roasting is done using drum/hot air fluidized bed at 180-250 ºC for 30 min. Groundnut roasting is done in a rotary drum roaster at 160 ºC for 40-60 min. Rice flakes roasting and puffing is done using salt as heat transfer medium at 200-250 ºC for 20-30 s. Hazelnuts are roasted in electric oven at 150 ºC for 20 min. However all these commercially available roasting machines are not suitable for primary roasting of raw makhana seeds. Popping or flaking is undesirable character while primary roasting of makhana. Further, the hard and thick seed coat of makhana seeds coupled with high moisture content at the time of primary roasting differentiates its roasting conditions from other grains. Roasting of other grains is done at low moisture content (?15%). Therefore the heat transfer requirements for makhana are different from other grains. The critical processing factor in primary roasting of makhana is the optimum level of moisture content during roasting and also at the end of the roasting. Any decrease of even 1% moisture lead to very poor popping quality. Gelatinization of the starch during roasting should take place with sufficient level of water in the kernel at the end of primary roasting. Heat transfer media (sand or salt), cannot be used as these reduce the moisture content very fast and gelatinization does not take place. Non-uniform heating of makhana seeds during roasting results into poor popping efficiency and sometimes no popping. Therefore proper agitation during roasting is essential. In commercial roasters for other grains, the variation in seed size is very less and therefore roasting time and temperature is independent on seed size. Whereas in case of makhana, the seed size varies from 6 mm to 13 mm and may be segregated into 12 to 18 sizes. The process conditions and gelatinization behaviour is highly size dependent. Thus, quick changes in heat transfer rate become crucial factor along with agitation level and process conditions for primary roasting of makhana.

Objective of the Invention
Main aim of this invention was to develop the mechanized system for primary roasting of raw makhana seeds. Therefore the present invention was done with the following objectives:
1. To develop a mechanized system for primary roasting of makhana seeds.
2. To develop optimum roasting process for primary roasting of makhana seeds of uniform size.

Details of Invention (Roasting Machine)
Traditional roasting method of makhana seed and experiments conducted for roasting of makhana seed. In this invention suggested that the roasting should be done in an open pan. The moisture content of seed should be around 25% immediately after completion of roasting. Heat transfer medium such as sand, salt cannot be used for roasting. Although the sand and salt increase the heat transfer rate, but excessive loss of moisture before gelatinization of the kernel results in the poor popping of the seeds. Therefore heat transfer through conduction in an open pan is the most suitable option for primary roasting of makhana seeds. Continuous stirring of the seed during primary roasting was another essential requirement to prepare good quality popped makhana. The basic as well as critical factor, which affect the popping quality and recovery of popped makhana are:
a. Sun drying of seeds: the seed moisture content before roasting must be 30±1%. Roasting of seeds at higher moisture lead to leakage of some gelatinized kernel from the seed. Roasting at lower moisture results into incomplete gelatinization and popping is reduced.
b. Size grading of seeds: The seed must be graded on the basis of average diameter. The difference in diameter of two consecutive grades should not be more than 1 mm. For gelatinization of the starch present in the kernel, the temperature of kernel should reach to 90 ºC. The temperature gradient inside a seed depends upon seed diameter, therefore, more than 1 mm difference in seed diameter results in non-uniform gelatinization of kernel. Thus, the precise grading of the seed is essential for uniform roasting in a roasting machine.
c. Temperature of inner surface of pan: In conduction heating, the heat transfer rate depends upon the temperature gradient. Therefore roasting at lower temperature need longer duration heating, which leads to the high moisture losses. While very high temperature of pan during roasting results into quick but non-uniform gelatinization. It also results into dark colored popped makhana. Therefore pan temperature during primary roasting should be optimum and the supply of heat should be sufficient to maintain the optimum temperature during the entire roasting process.
d. Completion of gelatinization: During roasting process, the high moisture starch present inside the seed is gelatinized. The intermolecular bonds of starch molecules breakdown in the presence of water and heat, allowing the hydrogen bonding sites to engage more water. This irreversibly dissolves the starch granule in water and the water present inside the kernel acts as a plasticizer. The kernel powder is converted into kernel form and its colour is changed to yellowish from white.
e. Roasting duration: Roasting duration of seeds depends upon the heat supply, quantity being roasted in a batch and seed size. Large diameter seeds take longer duration for roasting of seeds.
f. Moisture reduction limit during primary roasting: Initial moisture content of makhana taken for primary roasting is about 30% after sun drying, whereas, at the completion point of roasting, moisture content should reach at 25%. Therefore, the heating must be done in such a way that the starch present in the core of seed is gelatinized before the moisture content reaches to 25%. If the seeds are heated further, the moisture content may go below 25% and poor popping efficiency will reduce and dark colour popped makhana will be obtained.
g. Agitation speed during roasting: Continuous movement of seeds and mixing is important for uniform heating and proper starch gelatinization. Poor agitation results into dark colour popped makhana whereas very high agitation may cause poor roasting.
h. Tempering method: After completion of the first roasting, the hot seeds are transferred into gunny bags. Seeds are then stored for about 48 h so that the crystallization of starch takes place in stable forms for further popping to obtain bright colour popped makhana.
Considering the above critical factors, the primary roasting machine was envisaged to be a batch type roasting pan. The pan is heated from the bottom using LPG as heat source. The seeds are agitated continuously and kept in rotating motion during the entire operation. The primary roasting machine consist of a pan, heat supply system, mechanism to rotate the pan, mechanism for continuous agitation of seeds and a quick discharge mechanism of hot roasted seeds. The ergonomics and safety factors were also considered in the design of primary roasting machine. The components and power transmission mechanism of the primary roasting machine is as below:

Brief description of drawings
Figure 1 shows unit operations involved in makhana seed processing
Figure 2 shows photograph of the raw makhana roasting machine.
Figure 3 shows the front view of roasting machine
(1) Discharge gate cover
(2) Agitator finger assembly
(3) Roasting pan
(4) Rotatable plate to mount burner
(5) Hollow shaft
(6) Flange assembly
(7) LPG gas burner
(8) Discharge chute
(9) Gear box
(10) Driven gear mounted on shaft
(11) Seed discharge outlet
(12) Main frame
(13) Agitator mounted beam
(14) Motor
Figure 4 shows the top view of roasting machine
Figure 5 shows the side view of roasting machine
Figure 6 shows the Isometric view of roasting machine

Detailed description
Primary roasting machine
The Roasting machine developed for makhana seed works on the principal of parching and heating (Figure 2). The machine consists of five main parts as described below.
Roasting Pan: The primary roasting machine was designed to roast about 10 kg seeds in one batch. Uniform roasting of seeds takes place only when the thickness of seed layer on the pan is not more than 20 mm or only two layers of seed in a pan in stationary position. On the basis of this constraint and capacity envisaged, the pan diameter was calculated. On the basis of enthalpy, heat transfer coefficient during conduction and rigidity of material, mild steel was selected to fabricate the roasting pan (3). However, the pan may also be made with other steel and alloys, which do not deform during heating. The pan is made of 10 mm thick mild steel plate however it can also be made with sheet of more thickness or by casting also. A rim of 105 mm is welded at the periphery of the pan to avoid spillage during roasting. A hole of 100 mm is made at the centre of the pan for discharge of roasted seed. The diameter of the hole may be increased depending upon the discharge rate required. The pan is concave in shape and the concavity is 30 mm at the centre. The pan is fitted on a hollow shaft (5) which acts as discharge pipe. The pan assembly is placed in horizontal plane and rotated by reduction gear to ensure uniform rotation speed during the roasting. A detachable discharge gate cover (1) is made from mild steel. The cover is heavier at the bottom. The cover keeps the discharge gate closed during roasting and it is removed after completion of roasting to discharge the seeds.
Heating system: The LPG has been used as heat source for heating the pan for roasting. However, the other energy sources, such as oil fired, natural gas, and electric heater can also be used as heat source. In this system the burner (7) is placed 100 mm below and 200 mm away from the center of the pan bottom. The burners are mounted on the rotatable plate (4) so that the distribution of heat supply to the pan can be changed for uniformity when the lot for roasting is very less in comparison to designed capacity. More burners can also be fitted depending upon the batch size and heat required for primary roasting.

Power Transmission: The pan of the machine rotates in horizontal plane, which is mounted on a hollow shaft (5). The rotational speed of the pan can be as high as high as 100 rpm. The total load of pan is on a flange (6). For uniform, vibration free and smooth power transmission, the shaft is rotated by reduction gear drive mechanism. The power for rotating the pan is transmitted through a combination of driven gear (10) on the shaft, driven gear mounted on output of reduction gear box (9). A three phase AC electric motor (14) drives the gear box. The speed of motor is controlled by variable frequency drive. However, the speed can be fixed also depending upon the need.

Agitation system: The seeds are agitated by agitator finger assembly (2), which touch the roasting pan surface. The agitation fingers are made of mild steel in which 9 bars of 5 mm diameter and 450 mm in length are placed at 20º from horizontal plane. These fingers are joined at one end with a handle, which is fixed on mounting beam. The fingers are tied at the joint using a tie rod. Tip of the agitator fingers touch the pan surface. Inclination of finger assembly should not be more than 30º to avoid breakage of seed. The distance between agitating fingers is 25 mm where these touch the pan surface. The distance may vary between 15-30 mm. Two agitators are placed at opposite locations, however more than two agitators can also be placed. The agitators are fixed whereas the pan rotates and therefore the seeds are agitated continuously during roasting. Rotating motion may be given to the agitator when rotational speed of the pan has to be decreased or in the case of fixed pans. In case of fixed agitator, as in the developed machine, the agitator should touch the pan surface at the place beneath which the burner is located. This is a critical factor for production of good quality whitish makhana.

Discharge mechanism: When the detachable gate cover is opened, the seed passes through the hollow shaft due to gravity and comes out from the bottom end discharge outlet (11). A discharge chute (8) is fixed below the discharge outlet. When seeds fall on the chute, these flow on the chute due to gravity and collected in a jute bag.

Pre roasting process
The pre-roasting process is performed in the following manner:
Washing: Raw seeds are taken out from storage tank and washed with water to remove dirt, stones, snails and membranous cover. Mild abrasion may be given for proper washing in some cases.
Sun-drying: The clean seeds are sun dried by spreading on a mat or cemented floor for 2-3 h under bright sun light till the moisture content of seeds reaches to about 31%.
Grading: The dried seeds are categorized into 7-12 grades according to their diameter by means of a set of sieves. This facilitates uniform heating of each nut during roasting and increases the efficiency of processing. Grading can also be done any using screen graders available commercially.
Storage: The dried and graded seeds must be kept in shade prior to roasting. All the pre- roasting operations should be completed in 8-10 h and primary roasting should be completed within 12-16 h after taking seeds out from water. In case the roasting is not done within 16 h, the seeds should be transferred into water again.
Primary roasting process:
Roasting of graded seeds is done in ascending order of size grade as the lower seed size grade may tend to loose moisture quickly as compared to higher grade size. Primary roasting of makhana should be done in following manner:
• Pre-heating of pan: The pan is heated without seed till pan temperature reaches to about 250 ºC. The pan rotates continuously during this initial heating process.
• Loading of seeds: 8-10 kg of graded seeds is poured manually on the roasting pan when preheating is completed. Loading of more than 10 kg of seeds may form more than two layers of seeds on the pan surface and heating may not be uniformly distributed to all the seeds. In case of seed lot is less than 5 kg, quick heating of seeds may take place with non-uniform roasting.
• Agitation: Pan is rotated at 30-50 rpm for proper agitation of the seeds. Lower agitation may cause non-uniform heating of the seeds and poor gelatinization of starch whereas the higher agitation may not allow seed to absorb the heat properly and roasting duration is increased. The agitating finger should touch the pan surface continually for proper agitation.
• Primary roasting time: Duration of roasting depends upon the grade size as well as the lot size of seeds. Greater the seed size more will be the roasting time and similarly if the lot size is more it will take longer time and vice versa. However, in any case, the roasting duration should not be more than 5 min for seeds of 6-8 mm size and 8 min for seeds of 9-13 mm size. Heating time is reduced by increasing LPG flow rate.
• Testing sample: In between the roasting process, a few seeds are taken out and tested by breaking the seed. When the makhana powder present in the core of seed is converted to rubbery yellowish paste, the roasting is said to be complete. Continues crackling sound is another indicator of completion of roasting.
• Collection of roasted seed: The discharge cover placed at the centre of pan is removed after completion of roasting. The pan is rotated continuously whereas heating is stopped. The seeds are discharged and collected in jute bags without touching.
• Tempering: The mouth of jute bags are tied and kept for 48-72 h for the tempering, in which the soft kernel is crystallized and forms a solid kernel structure. Tempering is a critical factor in primary roasting process. Each batch of roasted seed should be collected in separate bags. These bags are kept away from each other. The bags are not placed in a closed container.
The novelties of the process over conventional method are as follows:
• The mechanized system for primary roasting of makhana is a cost effective system with high throughput capacity.
• Heating is done by LPG gas system and hence dependency on electricity is not there. The pan can be rotated manually also.
• Maintains uniform temperature and heat supply can be enhanced immediately to reduce moisture loss, particularly at the end of roasting period. The other heating systems do not increase heat supply immediately.
• Unique system of unloading the hot roasted seeds where the seed is transferred into bags without touching.
• Roasting of all grades of makhana seeds is possible. Any batch size between 5-10 kg can be roasted in the machine.
Example
The following typical examples are given to illustrate the process of the present invention to be carried out in actual practice and should not be construed to limit the scope of the present invention.
The makhana seed of variety Swarna Vaidehi were used to test the performance of the machine. The makhana seeds were taken out from water and spread in thin layer for 3 h under sun for drying till 31% moisture content was reached. Then the seeds were segregated in 7 grades (7, 8, 9, 10, 11, 12 and >12mm). Each grade of the seed was roasted separately in the roasting machine. Then the empty pan was heated till 270 ºC and pan was rotated at 50 rpm. Position of the burner was adjusted during pre-heating so that uniform heating of pan surface take place. Then the pre weighted makhana was poured in the pan and roasting of seeds was done. After 4 min of roasting the LPG flow rate was increased to maximum and, sample were taken after every 30 s and tested. After completion of roasting, the discharge gate was opened and heating was stopped. The roasted seeds were collected in jute bags, tied and kept in shade for 48 h for tempering. The moisture content of roasted seed was about 20% after tempering. Then the seeds were popped using makhana popping machine operated at standard operating conditions. The popped makhana recovery was calculated and reported as below (Table 1):
Table 1. Recovery of popped makhana after roasting in developed roaster
Seed size
(mm) Weight of seed (kg) Time of roasting (min) Popped makhana recovery
(% by weight of roasted seed)
12 2.104 5.30 40
11 2.810 4.37 40
10 6.628 8.54 50
9 9.470 8.26 50
8 5.000 5.18 48
7 6.088 5.54 45

Table 2. Colour values of popped makhana
S.No. Seed size (mm) L* a* b* z
1 12 70.32 3.02 20.72 26.58
2 11 71.73 2.46 19.74 28.74
3 10 72.34 3.40 22.23 27.84
4 9 68.20 4.00 21.32 24.02
5 8 70.39 4.21 24.17 24.62
6 7 72.02 2.60 19.27 29.38

It may be observed that the roasting time increased with size of lot and size of seed. Theoretically a recovery of 55-60% popped makhana is obtained on the basis of roasted seed weight. Remaining 40-45% part is seed coat and bran. Primary roasting of makhana seeds with the present invention yielded 45-50% popped makhana recovery. The colour values showed that the popped makhana was brighter with whitish colour.

Claims:1. A batch type mechanized system for primary roasting of raw makhana seed and process for rotates of raw makhana seeds comprising of;
a. A concave mild steel roasting pan mounted on a hollow shaft rotates at 30-50 rpm in horizontal plane
b. LPG fired burners fitted on a rotating plate below the pan bottom to supply the heat to the roasting pan.
c. A unique discharge mechanism with detachable lid to unload the hot roasted seeds from the pan through the hollow shaft.
d. Power transmission to the shaft through gear box and gear assembly to ensure vibration-free rotation of the pan.
e. Unique fixed agitating assembly placed at 20-30° angle from the horizontal for continuous agitation of the seeds during roasting.
f. A process of primary roasting in which the graded seeds are roasted in the roasting machine at 250 °C and above, agitating the seed continuously, and completion of roasting in 5-8 min, unloading the roasted seeds within 15 s in a jute bag, packaging and tempering of the roasted seeds to maintain the seeds moisture above 20% after 48 h of roasting.
2. As claimed in claim 1, the primary roasting machine is for roasting of all sizes grades of makhana seeds and each grade of seed is roasted separately.
3. As claimed in claim 1, the agitation system ensures that the seeds are rolled by the agitator after every 0.1 s.
4. As claimed in claim 1, the agitation system can also be rotated in opposite direction of rotation of pan to reduce the rotational speed of the pan.
5. As claimed in claim 1, the machine can roast the other seeds and nuts where heating is done though conduction.
6. As claimed in claim 1, the roasting process comprise of sun drying up to 31±1% moisture content followed by grading into 7 different sizes (6-12 mm), roasting of each grade separately in the mechanized system and tempering of each lot separately. The seed should be roasted within 12-16 h after taking out from water.
7. As claimed in claim 1, the roasting of each grade of seed at 30-32% moisture content, roasting pan temperature between 250 º-300 ºC, completion of roasting in 5-8 min, slow cooling of seed with about 3-4% moisture loss in 48 h.
8. As claimed in claim 1, more than two agitator arms can also be placed to reduce the rotational speed of the pan and increase the agitation.