Egusi Fruit Coring Machine

J. agric. Engng Res. (1999) 74, 121}126 Article No. jaer.1999.0418, available online at http://www.idealibrary.com on

Egusi Fruit Coring Machine C. O. Akubuo; E. U. Odigboh Department of Agricultural Engineering, University of Nigeria, Nsukka, Enugu State, Nigeria; e-mail: [email protected] (Received 23 July 1996; accepted in revised form 10 February 1999)

Based on relevant physical properties of the egusi fruit, a coring machine was designed to remove the seed-bearing core of the mesocarp and endocarp. The purpose of coring is to expose the seed-bearing core to microorganisms to achieve complete decomposition of the mesocarp and endocarp within a short period of time. The coring machine consists of reciprocating ring coring cutter which can be operated manually or by an electric motor. It produces a cylindrically shaped seed bearing mesocarp and endocarp core of the fruit. The prototype machine can core about 458 fruits/h when operated manually at 8}10 rev/min and about 2390 fruits/h when motorized at 50 rev/min, as against a hand peeling rate of 29 fruits/h. Decomposition of the mesocarp and endocarp of the seed-bearing core of the fruit took 2 d as against 7 d for the traditional method of processing.  1999 Silsoe Research Institute

1. Introduction The egusi fruit physically resembles the water melon in many respects. The Nigerian name, &&egusi'' is used here instead of &&melon'' because of the apparent confusion regarding the correct name of the food seeds generally agreed to be of the Citrullus species (Odigboh, 1979). It is a #eshy fruit which is generally green in colour, though some varieties have their green colour streaked with white. The external surface of the fruit is relatively hard and smooth. The majority of the fruits are nearly spherical in shape but some are ellipsoids having slightly elongated head-tail axial dimensions (Nwosu, 1988). Unlike water melon, the #esh of the egusi fruit is bitter and therefore not edible. Egusi fruit is grown for the seeds which are very nutritious, rich in protein and very important in the Nigerian diet. The seeds contain about 53% oil by weight (Oyolu, 1977) and 32)6% crude protein (Oyenuga, 1968) and also unsaturated fatty acids. Its amino-acid content compares well with those of soybean and whole poultry egg (Oyolu, 1977). The seed is a major soup ingredient in Nigeria and about 77 Mt are produced annually (Oyenuga 1968). Egusi fruit yield 1}15 t/ha and mature in 12}15 weeks after planting (Nwajinka, 1984). The traditional method of extracting egusi seed from the fruit involves manual cracking of the fruits with wooden clubs or cutting o! the 0021-8634/99/100121#06 $30.00/0

head or tail portions of the fruits with a knife, all done in order to create access for microorganisms to enter and cause the decomposition of the #eshy mesocarp and endocarp. The fruit so treated is left for about 7 d to decompose. Then the seeds are removed by washing in water. The traditional method requires a lot of time and labour. The task is unattractive especially because of the repulsive odour from the decomposing biomass. Consequently, the quantity of fruits a farmer can process is limited (Onyemelukwe, 1991). The decomposition period can be shortened if an extensive cut surface area is created for entry of microorganisms. The preliminary e!ort in this regard by Nwosu (1988) did not yield any practical result as the machine he designed was not built because of its complexity. Although substantial work on the shelling of egusi seeds has been reported in the literature (Odigboh, 1979; Makanjuola, 1976; Olude, 1978; Modupe, 1984), nothing has been reported on the extraction of the seeds from the egusi fruit. This paper discusses the physical characteristics of the egusi fruit and the design and testing of an egusi fruit coring machine intended to facilitate the extraction of the seeds. 2. Some physical properties of the egusi fruit A photograph of the common variety (Colocynthis citrullus) of egusi fruit is shown in Fig. 1. It is nearly

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3. The coring machine

Fig. 1. A common variety of the egusi fruit (Colocynthis citrullus): A, small size 9}11 cm diameter range; B, medium size 11}13 cm diameter range; C, large size 13}16 cm diameter range

spherical in shape. Figure 2 shows the transverse and longitudinal sections of the egusi fruit. The transverse section is obtained by cutting the fruit across the head}tail axis. The epicarp (A) is a thick tough outer coat strongly attached to the much softer #eshy mesocarp (B) to form what is jointly referred to as the rind (Nwosu, 1988; Ramalingam et al., 1977). The epicarp does not decompose easily and cracking is necessary to initiate decomposition. The endocarp (D) is segmented and separated from each other by the septum (C). Within the segments are the seeds (F) which lie on their #at sides in planes nearly perpendicular to the head}tail axis, with their heads directed towards the central septum and distinctly separated from each other by the #esh component of the endocarp. The longitudinal section is obtained by cutting the fruit along the head}tail axis. The edges of the seeds are displayed and look like thick lines perpendicular to the head}tail axis. The seeds are symmetrically arranged all around the central septum and are concentrated more within the central portion of the fruit than at the ends. On average, the seeds constitute 3)5% of the fruit by weight (Nwosu, 1988). Relevant physical properties of the egusi fruits grouped into three diameter ranges of 9}11, 11}13 and 13}16 cm were determined using 40 egusi fruits in each diameter range making a total of 120 fruits. The physical properties determined were: the characteristic dimensions, weight, volume and density. The results are presented in Table 1. The sphericity of the variety studied was found to be about 1)03 on the average showing that the shape of an egusi fruit closely approximates to that of a sphere. Therefore, an egusi fruit can roll on any of its sides. The density of about 0)87 g/cm shows that the fruit can #oat in water, a characteristic that can be utilized in handling the fruits.

The physical characteristics of the egusi fruit (Table 1) were used to design the coring machine (Fig. 3). It consists of a ring coring cutter (E) with one coring stroke in every cycle of reciprocation; a cutter carrier (P) which carries the ring cutter forward and backwards in its reciprocating motion and a hopper (G) for feeding the fruits into the coring zone. The machine is powered manually by a crack handle and also by a 0)56 kW electric motor (B). On cranking the machine or turning the motor on, the crankshaft (C) transmits the motion to the connecting rod (D) which results in reciprocating motion of the ring cutter (E). The egusi fruit (F) sits on an adjustable platform (H) as it leaves the hopper and the cutter cuts it by pushing it against a stationary support (K) to produce cylindrical seed bearing mesocarp and endocarp cores. As a fruit is being cut, the resulting core

Fig. 2. Transverse and longitudinal sections of an egusi fruit: (a) Transverse section; (b) longitudinal section; A, epicarp; B mesocarp; C, septum; D, endocarp; E, central septum; F, egusi seed, H, minor diameter; I, intermediate diameter; M, major diameter; S, stalk

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Table 1 Physical characteristics of the egusi fruit in three sizes with an average moisture content of 96)8% wet basis small, 9}11 cm diameter range; medium, 11}13 cm diameter range; and large 13}16 cm diameter range Mean values Parameters Major diameter (a), cm Intermediate diameter (b), cm Minor diameter (c), cm Geometric mean diameter (abc), cm SphericityR Unit volume, cm Unit weight, g Unit density, g/cm

Small size 9)60 10)01 9)85 9)82 1)02 560)60 500)46 0)88

(0)62)* (0)58) (0)69) (0)45) (0)01) (1)78) (4)47) (0)02)

Medium size

Large size

11)70 (0)60) 12)60 (0)56) 12)48 (0)51) 12)25 (0)56) 1)05 (0)03) 1085)29 (4)54) 918)19 (3)83) 0)86 (0)05)

14)80 (1)01) 14)91 (1)10) 15)65 (1)35) 15)12 (1)20) 1)02 (0)02) 2093)45 (3)16) 1817)20 (5)5) 0)88 (0)04)

geometric mean diameter (Mohsenin, 1970) * Values in parenthesis are standard deviations; R Sphericity" major diameter

pushes against the earlier core inside the carrier which is then ejected at the tail end of the carrier. Descriptions of the major component parts of the machine are given in the following sections. 3.1. ¹he ring cutters Three ring cutters were constructed. The size of each cutter depends on the dimensions of the egusi fruit

(Table 1). Figure 4 shows a photograph of the cutters. One end of each cutter is serrated while the other end is not. Serration of the cutters makes it easy to pierce the smooth tough epicarp of the fruit and so facilitates the coring action. The three cutters are each 16 cm long but of di!erent diameters and made to be detachable to allow for change in size to match the fruit sizes. The small sized cutter (A) is 8 cm in diameter, the medium sized cutter (B) has a diameter of 10 cm while the large sized cutter (C) is

Fig. 3. Egusi fruit coring machine: (a) top view; (b) front view; (c) side view; B, electric motor; C, crankshaft; D, connecting rod; E, ring cutter; F, egusi fruit; P, cutter carrier; G, hopper; H, platform; K, stationary support; M, pulley; N, v-belt; R, frame; S, runner rail; T, ball bearing. Overall dimensions of the frame length 1)6 m, width 0)7 m, height 0)6 m

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3 mm thickness. The size and shape of the hopper as determined from the characteristic dimensions of the egusi fruit (Table 1), facilitates the free #ow of the fruits by gravity into the coring section. The hopper contains about four fruits per loading.

4. Performance test

Fig. 4. Ring cutters: A, small size; B, medium size; C, large size

12 cm in diameter. They are used to core fruits in the diameter ranges of 9}11, 11}13 and 13}16 cm, respectively. There are four equally spaced sharp blades on the periphery of each cutter (Fig. 4). These blades cut the shell of the rind produced during coring into quarters. Figure 5 shows the cylindrical seed-bearing cores and quarters of the rind produced by the cutters. Each ring cutter is attached to a cutter carrier designated as (P) in Fig. 3. The carrier is such that each ring cutter can be "tted to it without necessarily changing it. It carries the ring cutter forward and backwards in its reciprocating motion. It is made hollow in order to receive from the cutter and temporarily hold up to two seed bearing cores. The two connecting rods (D) of the crankshaft for the slider-crank mechanism are attached to the rear end of the carrier as shown in Fig. 3. The carrier is 14 cm in diameter and 24 cm long, folded from 3 mm thick mild sheet. 3.2. ¹he hopper The hopper (G) shown in Fig. 3 is 20 cm long, 17 cm wide and 50 cm high. It is made from a mild steel sheet of

Fig. 5. Egusi fruit after coring: (a) core from small sized fruits; (b) core from medium sized fruits; (c) core from large sized fruits. A, cylindrical core of seed bearing mesocarp and endocarp; B, shell of rind cut into quarters

Some tests were performed to evaluate the performance of the egusi coring machine in terms of the capacity of the machine and the e!ectiveness of coring with respect to the decomposition time of the cores. Egusi fruits harvested from the same "eld on the same day were used for the tests. The fruits were weighed and their diameters recorded. As their weights varied in the range of 350}1800 g, the fruits were grouped into three diameter ranges of 9}11, 11}13 and 13}16 cm and then cored group by group. Fifty fruits from each diameter range were used for the performance testing of both the manually operated machine and the motorized one. There were three replicate runs in each diameter diameter range test. This gave a total of 150 fruits for a diameter range test in both the manual and motorized runs. The times of actual coring were recorded as shown in Table 2. In both tests, the fruits were manually loaded in the hopper regardless of their orientation. The three cutters were used to core fruits in the respective diameter ranges. The machine was cranked manually at 8}10 rev/min. It required up to 10 s to attain this speed before coring could start and the process was repeated each time a fruit was cored. In the motorized tests, the machine was run at about 50 rev/min. Coring was still accomplished in one revolution but at a much faster rate. For a given fruit size range and a given cutter size, the platform (H) in Fig. 3 was adjusted so that one fruit occupies the coring section while the one on top of it clears well from the coring section. As the cored fruit is carried away by the ring cutter in its return stroke, space is created for the next fruit to drop by gravity in the coring section and the possibility of fruits piling up in the coring section does not arise. For continuous manual operation, a second operator is needed to start loading the hopper when the "rst three fruits have been cored. Only one operator is required for motorized runs. Cores were produced manually in order to compare the production rate with that of the machine and to give a measure of the usefulness of the machine. Three operators were used to manually peel the egusi fruits. Fifty fruits were given to each operator, making a total of 150 fruits for each diameter range. The actual time of peeling by the operators, excluding their rest periods were recorded as shown in Table 3. Ten fruits from each diameter range were cracked by hand in the traditional way

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Table 2 Coring by machine Time of coring, min Operation

Small sized fruits (9}11 cm dia. range)

Medium sized fruits (11}13 cm dia. range)

Large sized fruits (13}16 cm dia. range)

Manual cranking (8}10 rev/min)

6)4 6)0 5)8

6)5 6)8 6)6

7)0 6)9 7)1

Average

6)1

6)6

7)0

Average rate of coring, fruits/h

492

455

429

Motorized (50 rev/min)

1)5 1)0 1)3

1)2 1)5 1)2

1)5 1)1 1)0

Average

1)27

1)3

1)2

Average rate of coring, fruits/h

2362

and allowed to decompose. The period in days for the hand-cranked fruits and the seed bearing cores to decompose were also recorded. Decomposition was regarded as complete when the seeds were easily hand-picked without washing them in water.

4.1. Analysis and discussion of results Coring of each fruit was completed in one revolution of the crankshaft, and, when in full operation, ejection of one core also took place in each revolution. Thus, the capacity of the machine is dependent on the revolution of the crankshaft. By manually cranking at 8}10 rev/min, the capacity of the machine was found to be about

2308

2500

458 fruits/h, while the capacity was about 2390 fruits/h when run at 50 rev/min using an electric motor. For speeds up to 60 rev/min, it was observed that there was no fruit in the coring section most of the time because the operator could not cope with loading at that speed. This limits the speed of the machine to 50 rev/min. The manual production of similar cores by peeling gave an average production rate of 29 fruits/h as against the production rates of 458 and 2390 fruits/h when the machine was manually cranked and motorized, respectively. This indicates that the machine has a great measure of usefulness and the production rates of 458 and 2390 fruits/h are considered adequate for a medium to large size farming enterprise. Visual inspection of the cylindrical seed-bearing mesocarp and endocarp cores produced from the

Table 3 Hand peeling of egusi fruits by three operators Time of peeling, min Operator

Small sized fruits (9}11 cm dia. range)

Medium sized fruits (11}13 cm dia. range)

Large sized fruits (13}16 cm dia. range)

1 2 3

92 90 91

100 98 101

125 126 124

Average

91

99)7

125

Average rate of peeling fruits/h

33

30

24

Overall rate of peeling by hand"29 fruits/h.

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Table 4 Performance data for the egusi coring machine as an average for both manual cracking and motorized results from 50 fruits in each diameter range

the mesocarp and endocarp was accelerated by coring; the seed-bearing pulp of the fruit core took 2 d to decompose as against 7 d for the traditional method.

Diameter range, cm

References

Decomposition period, d Uncored fruit*

Cored fruit Manual cracking

Motorized

9}11 11}13 13}16

6)5 7)0 7)5

2 2 2

2 2 2

Average

7)0

2

2

* Averages of ten hand-cracked fruits from each diameter range.

manual cranking of the machine and motorized tests showed no di!erence in the shape of the cores in all fruit diameter ranges. This is expected since the same cutters are used in all the tests. The e!ectiveness of the coring machine was also evaluated in terms of the decomposition time of the cored fruit as presented in Table 4. The decomposition of the mesocarp and endocarp of the seed-bearing core took 2 d as against 7 d for the traditional method.

5. Conclusions On the basis of the physical characteristics of egusi fruits as determined, a coring machine was designed, constructed and tested. The production rate of the manual prototype machine was about 458 fruits/h while that for the motorized machine was 2390 fruits/h as against a hand-peeling rate of 29 fruits/h. The decomposition of

Makanjuola G A (1976). An evaluation of some mechanical methods of shelling melon seeds. Nigerian Journal of Technology, 2(1), 1}11 Modupe F F (1984). Dehulling of egusi (Colocynthis citrullus). Bachelor of Science Project Report. Department of Food Science and Technology, University of Nigeria, Nsukka, Nigeria Mohsenin N N (1970). Physical Properties of Plant and Animal Materials, (Vol. I) New York: Gordon and Breach Nwajinka C O (1984). Design of a thin layer equipment and its use to investigate drying characteristics of melon seeds (Citrullus vulgaris). Bachelor of Engineering Project Report. Department of Agricultural Engineering, University of Nigeria, Nsukka, Nigeria Nwosu R C (1988). Engineering properties of egusi fruit and the design of egusi seeds extraction equipment. Bachelor of Engineering Project Report. Department of Agricultural Engineering, University of Nigeria, Nsukka, Nigeria, June Odigboh E U (1979). Impact egusi shelling machine. Transactions of the American Society of Agricultural Engineers, 22(6), 1264}1269 Olude L G (1978). A combined chemical}mechanical methods for skin removal from melon seed. Bachelor of Science Thesis. Obafemi Awolowo University, Ile-Ife, Nigeria Onyemelukwe C N (1991). Design and fabrication of a coring machine to aid de-pulping of egusi fruit. Bachelor of Engineering Project Report. Department of Agricultural Engineering, University of Nigeria, Nsukka, Nigeria, July Oyenuga V A (1968). Nigeria's Food and Feeding Stu!s. Ibadan, Nigeria: Ibadan University Press Oyolu C (1977). A quantitative and qualitative study of seed type in egusi (Colocynthis citrullus L.). Tropical Science, 19(1), 55}61 Ramalingam S T; Pereira S; Pereir C T (1977). Modern Biology for Secondary Schools. FEP International Limited, Singapore