Performance evaluation of high capacity mechanised dehusking equipment for green arecanut ( Areca catechu L . )

India is a major arecanut (Areca catechu L.) growing country. Of the many problems identified in arecanut processing, dehusking is found to be a major one, which is cumbersome and needs to be mechanised. Presently, there are a few types of equipments available, but these machines are basically of low capacity and cater to small arecanut growers. Performance evaluation of three high capacity green arecanut dehusking equipments was taken up, to work out its possible adoption for entrepreneurship development. Equipment under evaluation consisted of power mounted dehusker with hook tooth cutting blade fixed in a cutting wheel to dehusk the outer shell with a nut ejection system coupled with a vibrating deck of trays to grade and convey the dehusked nuts. The Blade-Knurl shaft speed ratio was optimised as 1:11. Whole nut recovery per cent ranged from 81.84 ± 1.87 to 82.52 ± 1.95 per cent. The unhusked per cent and partially husked percentage ranged from 7.60 ± 3.71 to 7.81 ± 4.68 and 8.29 ± 2.15 to 8.85 ± 2.82, respectively. The broken nut percentage ranged from 1.03 ± 1.36 to 2.06 ± 2.72 percentage. The total cost of operation for two-belt, four-belt and six-belt model was ` 162 h-1,` 237 h-1 and ` 262 h-1, respectively. Better dehusking efficiency with reduced damage to the nuts achieved in mechanical dehusking would enable the farmer to realise additional yield with saving in time and lower cost of operation.


Introduction
Arecanut (Areca catechu) is an important commercial crop in India. Its production in India is dominant in the coastal region within 400 kilometres from the coastline, and also in some other noncoastal states of India. It is popularly known as betel nut, as its common usage in the country is for mastication with betel leaves (Vion et al., 2017). 'Areca' is taken up from the Malayan language, which means 'cluster of nuts'. It has commercial and economic importance not only in India but also in China and South-East Asia. Within India, Karnataka produces 67.22 per cent of the crop, followed by Kerala and Assam (www.dasd.gov.in, 2020). There are two varieties of arecanut viz., White Supari and Red Supari (Anand et al., 2012). White Supari is prepared by harvesting fully ripened arecanut followed by sun-drying for 40 to 50 days. After drying the nut, shell of the nut has to be removed by hand/machine. Red Supari is prepared by harvesting the tender (green) arecanut, peeling off the husk and boiling it (Vion et al., 2017). White variety accounts for 60 per cent of the product with the rest going for red. During the crop cycle, adopting modern input technologies, including mechanisation, is required to improve productivity (Ramappa and Manjunatha, 2013). Among many problems, identified, dehusking has been identified as a tedious and time-consuming process which needs to be mechanised (Pradeep and Raghvendra, 2012;Asokan et al., 2014).
Dehusking is the most important activity in the entire arecanut processing (Baboo, 1981;Balasubramanian and Panwar, 1986;Aviara et al., 2012). The raw fruit has to be peeled to get its kernel, and this has to be done within 24-36 hours after harvesting (Aviara et al., 2012;Asokan et al., 2014;Suhas et al., 2016). Otherwise, cutting will not be easy, and quality will start deteriorating. Manual dehusking of arecanut is a slow process and needs skilled labour. Due to the lack of skilled labour, fresh areca nuts cannot be dehusked immediately. Some efforts have been made to develop a dehusking unit for dry arecanut (Varghese and Jacob 1998;Jarimopas and Niamhom, 2004;Niamhom et al., 2007;Jarimopas et al.,2009;Aware et al., 2016;Suhas et al.,2016;Bellubbi et al., 2018). The machines are not suitable to dehusk fresh green/tender arecanuts, which needs a different mechanism for peeling (Vijayakumar et al., 2017;Nalawade et al., 2018). Most of the reported equipment for dehusking of green arecanut is manually operated or of very low capacity of few kilograms per hour which is not acceptable for commercial production (Kiran et al., 2014;Asokan et al., 2014;Joy et al., 2015;Alfaz et al., 2018). The machines of low capacity will not be suitable for large scale dehusking process, custom hiring and entrepreneurship development. For commercial adoption of equipment, it should be of higher capacity and also need to have good dehusking efficiency with lower broken nuts. The machine should be simple in design, easy to operate by unskilled person and portable. The present investigation was taken up to study the dehusking efficiency of high capacity tender (green) arecanut dehusking equipment and its suitability for adoption for entrepreneurship development based on its capacity, performance and cost economics.

Preparation of arecanut for dehusking
Fresh green arecanuts of Thirthahalli variety were selected for the present investigation. The arecanuts were harvested 7-8 months after flowering. The harvested nuts were collected free of external, unwanted materials and transported to arecanut processing yard. The basic concept of a dehusking machine of the tender arecanut is depicted in Figure 1. The important components are cutting wheel, blade, tub and knurl shaft. Dehusking is done by shearing action between cutting wheel and the knurl shaft. To get the best output in terms of the higher dehusking and a lower amount of unhusked, partially husked and broken nuts, the ratio between the speed of cutting wheel and the knurl shaft need to be optimised. A preliminary experiment was carried out to optimise the speed ratio between cutting wheel and knurl shaft, which could be adopted for high capacity green arecanut dehusker.

Optimising the speed of dehusking equipment
Optimisation of speed of operation of arecanut dehusking was carried out based on the speed ratio between the knurl shaft and wheel/blade shaft. The data was recorded in terms of feed inlet and output viz., whole nuts, unhusked nuts, partially dehusked nuts and broken nuts. A set up was made to vary the speed ratio between the blade shaft and knurl shaft in the range of 1:10 to 1:12 (Vishwanathan, 2014;Patent No: 259204).The optimum ratio was fixed based on various parameters like whole nut recovery, unhusked, partially dehusked and broken nuts. Based on the optimum ratio, performance evaluation of three models of arecanut dehusking equipment was carried out at the optimised speed of operation. Each trial was replicated five times.

Functional parts of arecanut dehusking machine
The arecanut dehusking machine consists of a power source, feeding conveyor, feeding hopper, outer frame, discharge outlets, transmission cover and top safety cover (Fig. 2).

Equipment for dehusking of green (tender) arecanut
Three models of arecanut dehusking equipment viz., two-belt model, four-belt model and six-belt model were selected for evaluation (Fig. 3). The general specification of the equipment is given in Table 1.

Conveyor
The conveyor is made of plastic cups attached to the conveyor chain, which forms like a bucket elevator. Conveyor cups are designed to carry single arecanut which is transferred to the dehusking zone. The number of conveyors in the dehusking machine varied from 2, 4 and 6 based on the model selected. Each conveyor has 24 cups fitted on it.

Cutting wheel
The cutting wheel is made of aluminium with a diameter of 295 mm and a width of 63 mm. The wheel is provided with single or plurality of the blades. If the first wheel is provided with one blade, the next wheel is provided with more than one blade. Further, the wheel is provided with a plurality of steps or pit like openings where the blades can be fixed. Cutting wheels are fixed on a mild steel shaft of 35 mm diameter and 460, 810, 1165 mm length for three models under consideration which receives power from the gear transmission mechanism.

Cutting blade
The cutting blade is hook tooth type, made up of stainless steel. The curved blade has 12 sharp teeth on its circumference on one side with a radius of curvature 135 mm and a length of 145 mm. The thickness of the blade material is 1.25 mm. A set of cutting blade consists of 6 blades, fixed on the outer periphery of the cutting wheel. Blade imparts cutting force on the arecanut radially, which aids in dehusking operation. The depth of cutting blade (4-6 mm) can be adjusted as per physical properties and condition of the nuts to be dehusked.

Tub
The tub is like a rectangular channel to allow arecanut to peel off and deliver to the vibrator trays. It is made of aluminium (155 mm x 85 mm x 80 mm) and holds the arecanut against the knurl shaft for peeling. Once the husk is peeled off, the tub opens with the help of cam attached to it, to eject the dehusked nuts.

Husk separator
Husk separator is made by fixing toothed wheel to the shaft of 30 mm diameter with a length of 625, 990, 1342 mm for different models under investigation. Tooth removes the peeled husk which gets stuck between the blades. Teeth wheel is made up of mild steel and fixed behind the cutting wheel.

Nylon brush
Nylon brushes are attached to a mild steel shaft of diameter 20 mm and a length of 340, 690, 1050 mm for different models under investigation.
Brushes while rotating at an optimum speed, remove the fibres stuck to the wheel and blades.

Knurl shaft
Knurl shaft is made up of stainless steel of diameter 20 mm diameter and a length of 620, 980, 1330 mm for different models under investigation. The knurl shaft rotates arecanut, which was pressed by the tub to peel the husk. The knurl shaft is roughsurfaced one which gives enough friction to rotate the arecanut to a particular position enabling dehusking.

Vibrator
Vibrator consists of a deck of trays of length 910, 1240, 1595 mm for different models under investigation with a width of 250 mm and a total height of 220 mm. The arecanuts after dehusking reaches the vibrator which grades the arecanuts into various categories viz., whole nuts, unhusked and partially dehusked nuts and broken nuts.

Operation of equipment
Initially, raw materials are fed into the dehusking machine through feed hopper. The nuts in the feed hopper are lifted by the plastic cups embedded on the conveyor and transferred to the dehusking zone. The teeth of the blade hold the nuts and peels off the husk while the knurling shaft rotates the nut to the required position. The tub moves forward laterally to release or allow the peeled or dehusked nut to fall into the outlet or discharge chamber, i.e., peeled or dehusked nut comes out of the machine. Husk will be removed from the blade by husk separator and discharged through the outlet.
Further, the nylon brush removes the fibres entangled in the brush. Due to the application of high shearing force, the husk is peeled off from the periphery of the nut and gets ejected to the vibrating trays. The motion of the blade and the knurling shaft is synchronised in such a way that when the blade is rotated/pushed forward in the anti-clockwise direction, the knurling shaft is rotated in the clockwise direction. Each dehusking unit is provided with two sets of cutting blades fixed in the cutting wheel deriving power for its operation from the electric motor. The motor capacity ranges from (0.75 to 1.5 kW) depending on the capacity of the equipment.The sound generated by the equipment during the evaluation was recorded by the sound level meter (Make-Lutron Electronic Enterprises Co., LTD; Model-SL-4012; least count of 0.1 dB).

Performance evaluation of the equipment
After the dehusking operation, 1000 numbers of arecanut was randomly sampled for a specific time of operation. Various fractions viz., whole nuts, unhusked nuts, broken nuts, partially dehusked nuts were collected from each outlet and separated manually and weighed using a balance (Make: Avery; least count of 0.01g). Each experiment was replicated five times.
Operational capacity: (Balasubramanian and Kokila, 2014) c = q t t where, c is the operational capacity of the dehusking machine (kg h -1 ), q t is the total quantity of fresh arecanuts used for dehusking (kg) and t is the time taken for dehusking the given quantity (h).
Whole nut recovery efficiency (Balasubramanian and Kokila, 2014) η d = (1-q uh ) x 100 q t where η d is the whole nut recovery of the machine (%) q t is the total quantity of fresh arecanuts used for dehusking (kg) and q uh is the total quantity of unhusked, partially dehusked arecanuts and broken nuts (kg).
Power consumption (Indian Standard, IS 12411:1988) The difference between the two consecutive energy meter readings was taken as power consumption for a specific period. The power consumption (kWh) was calculated, giving the due allowance to the type of drive.

Cost economics
Cost economics of operation of arecanut dehusker, including fixed and variable cost was calculated as per the procedure enumerated by Regional Network for Agricultural Machinery (RNAM) test code (Anonymous, 1983). The cost of operation per hour was also worked out. The performance of various capacities of arecanut dehusker was compared with conventional manual dehusking in terms of saving in time, labour and cost. The break-even point and payback period of the equipment were also worked out as detailed below (Muthamil Selvan et al., 2007)

Optimisation of speed of operation of equipment
Optimisation of speed of operation of equipment dehusking of arecanut was carried out based on the speed ratio between blade shaft and knurl shaft. The performance evaluation data is given in Table 2. With the increase in the blade to knurl ratio from 1.10 to 1.11 the whole nuts recovery percentage increased significantly from 79.63 ± 1.67 to 85.74 ± 1.54 and with further increase in the blade to knurl ratio to 1:12, the whole nut recovery percentage reduced significantly from 85.74 ± 1.54 to 78.33 ± 1.87. The unhusked percentage reduced significantly from 10.61 ± 1.08 to 6.84 ± 0.91, with an increase of ratio from 1.10 to 1.11. With further increase in the blade to knurl ratio to 1:12, the unhusked kernel percentage increased significantly from 6.84 ± 0.91 to 8.73 ± 0.77. A similar trend as that of the unhusked kernel was observed in the case of partially husked kernels.
The broken kernel percentage reduced significantly from 2.02 ± 0.21 to 1.05 ± 0.12 with the increase in the blade to knurl ratio from 1:10 to 1:11. With further increase in the blade to knurl ratio to 1:12, the broken kernel percentage increased significantly from 1.05 ± 0.12 to 4.27 ± 0.38. Based on the results of whole nut recovery, unhusked percentage, partially husked percentage and broken percentage, with the variation of the blade to knurl ratio from 1:10 to 1:12, it was observed that the highest whole nut recovery of 85.74 ± 1.54 per cent with lowest unhusked percentage (6.84 ± 0.91), partially husked percentage (6.37 ± 0.29) and percentage of broken nuts (1.05 ± 0.12) was Breakeven (kg annum -1 ) =

Statistical analysis
The data were analysed as per Completely Randomised Design (CRD). Statistical significance was determined at p <0.05 by ANOVA, and the means were separated using Duncan's Multiple Range Test according to Panse and Sukhatme (1989). Each treatment was replicated five times. observed at the blade to knurl ratio of 1:11. Keeping these results as a base, all the models of the arecanut dehusking under evaluation was operated by using the fixed blade to knurl ratio of 1:11 (Vishwanathan, 2014;Patent No. 259204).

Comparative performance of the mechanised dehusking machine
Various models of dehusking machine for fresh arecanuts under investigation was evaluated for its performance in terms of operational capacity, dehusking efficiency compared with the traditional manual dehusking method (Fig. 4). The performance evaluation of the three models of dehusker is given in Table 3.

Operational capacity
The operational capacity of mechanical dehusking was found to be 379.7 ± 9.46, 683.0 ± 6.48 and 984.7 ± 4.64 kg h -1 for two-belt, four-belt and six-belt model of arecanut dehuskers, respectively. The capacity of manual dehusking was 5 to 6 kg h -1 . Variation in the dehusking capacity in the three models under investigation was mainly due to the number of belts. In the case of manual dehusking, the operator needs to apply the force required to peel the husk using a knife. The application of force by the machine is limited in such a way that blades penetrate to required depth without damaging nut inside the shell. When dehusking was done by hand, the operators experienced drudgery as the time elapsed. Therefore the average capacity per labour was 5-6 kg h -1 which was lower than mechanical dehusking. In mechanised dehusking operation, nuts were lifted one by one and transferred to the dehusking zone. Operational capacity varied with the number of belts in accordance with the size Two-belt model Six-belt model Dehusked arecanut Fig. 4. Performance evaluation of the arecanut dehuskers and positioning of the nut during the dehusking process.

Performance evaluation of equipment
Performance of equipment was evaluated in terms of whole nut recovery per cent, unhusked nut per cent, partially husked nut and broken nut per cent. The whole nut recovery per cent ranged from 81.84 ± 1.87 to 82.52 ± 1.95. The unhusked per cent and partially husked percentage ranged from 7.60 ± 3.71 to 7.81 ± 4.68 and 8.29 ± 2.15 to 8.85 ± 2.82, respectively. The broken nut percentage ranged from 1.03 ± 1.36 to 2.06 ± 2.72. The power consumption of two belt model, four belt model and six belt model of dehusker were 0.77 ± 0.02, 1.21 ± 0.02 and 1.26 ± 0.03 kWh, respectively.

Noise level
For agricultural machines,the noise level is an important ergonomically aspect as it has effects on the hearing ability of the workers. As per the Occupational Safety and Health Administration (OSHA;www.osha.gov/laws-regs/regulations/ standard number/1910/1910, the permissible exposure limit (PEL) is 90 dB for all workers for an 8-hour day. In the three models under evaluation, the maximum sound level was in the range of 86.19 ± 0.31 to 89.44 ± 0.29 dB, and the minimum sound level was in the range of 83.51 ± 0.30 to 85.91 ± 0.62 dB, which was well within the permissible accepted limit and hence acceptable.

Economics of various models of arecanut dehusker
The data and information collected both on the conventional method of dehusking and by using mechanised dehusking machine were analysed for the cost of dehusking. For working out the cost economics of the equipment, the  (Table 4). From Table 4, it is seen that the total cost of operation for two-belt, four-belt and six-belt model was ` 162 h -1 , ` 237 h -1 and ` 262 h -1 , respectively. The custom fee of the equipment is ` 184 h -1 , 266 h -1 and ` 270 h -1 . Effective capacity of 340, 615 and 850 kg h -1 was recorded for the three models of dehuskers under investigation. The corresponding break-even period of three models was 1.64, 1.70 and 2.23 years, respectively (Table 5).

a) Cost of dehusking by manual method
The capacity of the two-belt model, four-belt model and six-belt model of arecanut dehuskers were 375 kg h -1 , 675 kg h -1 and 975 kg h -1 , respectively The cost economics study revealed significant percentage saving in time, labour and cost by the adoption of the arecanut dehusker for dehusking of green arecanut (Table 5). Per cent saving in time, labour and cost ranged from 88.80 to 95.70 per cent, 77.78 to 86.96 per cent and 63.60 to 77.40 per cent for two-belt model, four-belt model and six-belt model, respectively. As the capacity increases, the per cent saving in time, labour and cost also increased due to the higher capacity of the equipment per unit time. Thus, it was seen that the high capacity arecanut dehusker for green arecanuts could be adopted in the arecanut production catchment, thereby leading to entrepreneurship development. This would lead to strengthening of quality raw material in the supply chain of industries involved in the production of the value-added products from arecanut, as the dehusking process could be carried out within the recommended time after harvesting.

Conclusion
Dehusking of green arecanut is a time consuming, but very important unit operation in the processing of green arecanut. This operation needs to be completed within 24-36 hours after harvesting so that the best quality product reaches the post-harvest value chain. Hence, there is a need to adopt high capacity green arecanut dehusking machine. Performance evaluation of three models of the dehusker revealed significant percentage saving in time, labour and cost by the adoption of the arecanut dehusker for dehusking of green arecanut. The effective capacity of the three models is 340, 615 and 850 kg h -1 with corresponding breakeven period of 1.64, 1.70 and 2.23 years, respectively. The equipment can be adopted by entrepreneurs at the arecanut catchment, thus generating revenue and getting a better finished product as dehusking can be carried out within the stipulated time.