Scholarly article on topic 'Effect of Moisture Content on Physical Properties of Animal Feed Pellets from Pineapple Plant Waste'

Effect of Moisture Content on Physical Properties of Animal Feed Pellets from Pineapple Plant Waste Academic research paper on "Agriculture, forestry, and fisheries"

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Abstract of research paper on Agriculture, forestry, and fisheries, author of scientific article — M.F. Zainuddin, S. Rosnah, M. Mohd Noriznan, I. Dahlan

Abstract Presently, pineapple residues are recycled through open burning before replanting, thus contributed to the air pollution. One of the possible ways to manage pineapple residues is by converting them into animal feed by densification process. Densification of biomass into pellet can increase bulk density, improve storability, reduce transportation costs, and enables easier handling with proper storage equipment. The range of pellet's friability, bulk density, true density and porosity are between 0.85 - 1.22%, 303.31 - 345.24kg m-3, 1502.65 - 1520.35kg m-3 and 77.022 - 80.05%, respectively. Thus, from the analysis, the best condition to produce pellets from pineapple plant waste, was at 35% of moisture level.

Academic research paper on topic "Effect of Moisture Content on Physical Properties of Animal Feed Pellets from Pineapple Plant Waste"

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Agriculture and Agricultural Science Procedia 2 (2014) 224 - 230

"ST26943", 2nd International Conference on Agricultural and Food Engineering, CAFEi2014"

Effect of Moisture Content on Physical Properties of Animal Feed Pellets from Pineapple Plant Waste

M.F. Zainuddina, S. Rosnaha *, M. Mohd Noriznana, I. Dahlanb

aDepartment of Process and Food Engineering, Faculty of Engineering, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia. bDepartment of Animal Science, Faculty of Agriculture, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia.


Presently, pineapple residues are recycled through open burning before replanting, thus contributed to the air pollution. One of the possible ways to manage pineapple residues is by converting them into animal feed by densification process. Densification of biomass into pellet can increase bulk density, improve storability, reduce transportation costs, and enables easier handling with proper storage equipment. The range of pellet's friability, bulk density, true density and porosity are between 0.85 - 1.22%, 303.31 - 345.24 kg m-3, 1502.65 - 1520.35 kg m-3 and 77.022 - 80.05%, respectively. Thus, from the analysis, the best condition to produce pellets from pineapple plant waste, was at 35% of moisture level.

© 2014 The Authors. Publishedby Elsevier B.V. This is an open access article under the CC BY-NC-ND license


Peer-review under responsibility of the Scientific Committee of CAFEi2014

Keywords: Agro-waste; densification; extrusion; moisture content; pellets; pineapple plant waste

1. Introduction

Malaysia produced a total of 334,400 tonnes of pineapple fruits in 2012. The harvested area was around 15,611 hectares, which produces 21.42 tonnes of pineapple fruits per hectare (FAO, 2014). In agricultural processes, a lot of residue from pineapple planting, which is called agro-waste, is produced during harvesting activities (Wan and Zainuddin, 2013). Currently, the agro-waste had become an environmental issue since there is no appropriate method in handling these residues. Therefore, pineapple residues are recycled through open burning before

* Corresponding author. Tel.: +60389466366 E-mail address:

2210-7843 © 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license


Peer-review under responsibility of the Scientific Committee of CAFEi2014

doi: 10.1016/j.aaspro.2014.11.032

consecutive replanting process (Ahmed et al., 2008). One of the possible ways to manage pineapple residue without harming the environment is by converting these residues into value-added products (Ahmed et al., 2002). Animal feeds have become an increasingly critical component of the integrated food chain since there is an increase in demand for animal products including meat (Philip, 2010). The utilization of agro-wastes as animal-feed, especially for herbivores, could reduce the amount of agro-waste, obtained worldwide, yearly. According to Kellems et al. (1979), post-harvest pineapple plant material is a forage resource that is used only to a limited extent although it could be used to increase animal-feed production in tropical areas where pineapples are widely grown. The challenges of feeding these materials to livestock in fresh form or as ground materials are the difficulty in mixing them with other ration ingredients, costs and difficulties in transportation and storage process (Terril et al., 2007). Since pellets have better flow properties, pellet densification can reduce wastage and improve transportation and also storage (Adapa et al., 2006). For the proper design, handling and transportation system, the physical properties of the pellets need to be determined (White and Jayas, 2001).

The advantages of pellets are not only easier for transportation and storage, but also, improved flow properties and feeding (less dust, less wastage, lower labor cost). Furthermore, feed pellets are much more precise and easier to control over the desired feed ration for individual animals or groups of animals with greater nutritional needs, such as immature stocks or lactating females (Mahapatra et al., 2010 and Supriya et al., 2012). According to Supriya et al. (2012) and Tumuluru et al. (2010), there are several techniques of biomass densification process such as globulation, compression, balling and extrusion by using screw press. The extrusion by screw press involved applying pressure to a wet mass until it passes through the calibrated openings of a screen or die plate of the extruder. Then, it went through further process to shape it into small extruded segments which eventually break under their own weight.

In recent years, physical properties of various pellets such as alfalfa (Adapa et al., 2006), peanut hulls (Fasina, 2007), corn-soybeans (Parsons et al., 2006), canola and sunflower meal (White and Jayas, 2001) have been studied. However, there is no information available in the literature about the physical properties of pellets from pineapple plant waste after extrusion process and their relationship with moisture content. Therefore, this study was carried out to determine the physical properties (bulk density, true density, porosity and friability) of the whole pineapple plant waste by using different moisture content levels (35%, 40%, 45% and 50%) of the sample. The moisture content is important as the appearance and stability of the pellets depend on the amount of water contained during pellet processing.

2. Meteríais and methods

2.1 Materials

Three different varieties (Josapine, MD2 and Moris) of pineapple crop, were collected from the Pineapple Farm, in MARDI Serdang, Selangor. 1 kg of sample from the leaves and stems of different varieties of pineapple plants were picked randomly at the same time. The pineapple leaves and stems were manually chopped and washed using tap water. Then, the samples were cut into 2-3 cm and dried using an oven (OF-G22W, Jeio Tech, Korea) at 60 °C for 72 hours to preserve the nutritional content of the materials (Steyn, 1959). Both of the samples (stem and leaves) were separated. The samples were grounded and sieved into 1 mm particle in size by using the Mill Grinder (Retsch, SM200 Rostfrei, Germany). Then, both of the samples were dried for 24 hours at 60 °C. The dried samples were kept in the refrigerator (HVF-301S, Hesstar, Kuala Lumpur) for further analysis.

2.2 Moisture content determination

The moisture content is crucial because it can affect the physico-chemical and stability of the pellets (Mahapatra et al., 2010). The evaluation on the effect of moisture content on the physical properties of pellets was carried out at four moisture levels (35%, 40%, 45% and 50%). The chosen range of moisture content (35%-50%) used is due to the fact that the equipment only operate if the moisture content for the sample exceeds 30%. The moisture content of

the sample was measured on a wet basis (w.b.). The samples with the desired moisture contents were prepared by adding an amount of distilled water as calculated from the following relation (Co^kun et al., 2005):

Q = Wi{Mf - Mt)/(100 - M/) (1)

where, Q is the mass of distilled water added, kg; Wi is the initial mass of the sample,kg; Mi is the initial moisture content mass of the sample in % (dry basis); Mf is the final moisture content of the sample (dry basis.).

2.3 Pelletization process

The pelletization process was conducted by using an Extruder (Kompaktextruder KE 19, Brabender, Germany). 500 g of sample with different moisture content level (35%, 40%, 45% and 50%) was compacted in the extruder with parameters such as temperature, screw speed and die diameter, fixed at 100°C, 150rpm and 8mm, respectively. The length of each of the pellet was about 3 cm. According to the Bureau of Rice Research and Development (2012), first class pellets must have a size less than 8.0 mm in diameter and less than 3.2 cm in length.

2.4 Friability test

20 pellets were selected randomly and weighed by using electronic balance (ER-120A, A&D, Japan). Then, the pellets were rotated at 25 rpm for 4 minutes by using an electronic friabilator (DF-3, Distek, USA) . The samples were subjected to roll and fall for 100 times by means of drum rotation and followed by removal of any loose dust generated from the pellets during the test. The pellets were dedusted and weighed. The percentage of weight loss was calculated using the following formula (Deveswaran et al., 2009):

Percentage friability = 'nitiol weight-final weight x 100 (2)

u Initial weight v 7

2.5 True density

True density measures the weight per unit volume of powder material, excluding the voids (Michcrafy et al., 2007). The true density of single-components and binary mixtures were measured using a helium gas pycnometer (AccuPyc II 1340) Pycnometer Micromimetics, U.S.A.). The pressure difference between the known reference volume and total cell sample was taken as a measurement (Karunanithy et al., 2012). The test was carried out by measuring 1.0 g for each sample. The results of the true densities of pellets were reported in triplication.

2.6 Bulk density

Bulk density is determined by filling a 200 ml cylinder with the sample from a set height, tapping twice (to obtain uniform packing and to minimize the wall effect, if any) and weighing the contents by using a digital balance. The bulk density was calculated as the ratio of the sample's mass to the cylinder volume (Liu et al., 2013).

Pb=mb/Vb (3)

where pb is the bulk density (g cm-3), Vb is the volume of cylinder (cm3) and mb is the total mass of the pellets (g).

2.7 Porosity

Fraction of the volume of voids over the total volume and void spaces in a material is a measurement for

porosity; it generally lies between 0 - 1. The porosity was calculated by the true density and bulk density measured as explained by Stelte et al. (2010).

_ . . Bulk Density *

Porosity = 1--- x 100 (4)

True Density

2.8 Statistical analysis

Triplicate measurements were conducted at all physical properties analysis of the pellets. The data were analyzed using Microsoft Excel and SAS 9.0 system (SAS Institute Inc., Cary. NC, USA) to analyze the mean, standard deviation, and least significant difference test (LSD) (P < 0.05).

3. Results and discussion

Table 1. Effect of moisture content on the pellets' physical properties.

Moisture Content (%) Friability (%) Bulk Density (kg m-3) True Density (kg m-3) Porosity (%)

35 0.85±0.20a 303.31±0.01a 1520.35±0.25a 80.05±0.61a

40 0.91±0.05a 322.92±0.01a 1513.85±0.55b 78.67±0.68a

45 1.02±0.02a 322.92±0.01a 1508.50±0.10c 78.59±0.69a

50 1.22±0.09a 345.24±0.02a 1502.65±0.75d 77.02±0.82a

*Means with the same letter are not significantly different at p>0.05 for each column.

The data obtained on the effect of different levels of moisture content on the pellets' physical properties is presented in Table 1. There were variations in the pellets' physical properties at different moisture content, with friability (%) values ranging from 0.85 to 1.22%, bulk density(kg m-3) from 303.31 to 345.24 kg m-3, true density (kg m-3) from 1502.65 to 1520.35 kg m-3 and porosity (%), from 80.05 to 77.02%.

3.1 Friability

Friability or durability refers to the tendency for the pellets to form dusts or to break-up/off when subjected to destructive forces. It is the ability of the compressed pellets to avoid fracture and breaking apart during handling and transportation. The production of fines or dust during handling, transportation and storage would create health hazards and inconvenient environment for the workers (Vinterback, 2002). Karunanithy et al. (2012) suggested that fines up to 5% (by weight) would be an acceptable level, but greater than 5% would reduce storage capacity and create problems in flow characteristics. Table 1 shows that friability of the pellets varied between 0.85 to 1.22%. According to the values, all pellets that have different moisture content showed an acceptable level of friability value, which is below 5% of fines. This low friability indicated that the pellets were able to withstand the shear forces when subjected to mechanical shock or attrition. These pellets also had high storage capacity. From Table 1, the lowest friability was observed at 0.85% for 35% of moisture content, while the highest was at 1.22% for 50% of moisture content. The results depicted that there was no significant (P > 0.05) increase in the pellet's friability percentage with increasing moisture levels. There were no significant differences due to the similarity of chemical composition in the pellets including lignin, extractive, cellulose, hemicellulose, structure and fraction in leaf to stem (Karunanithy et al., 2012). Based on the study by Kaliyan and Morey (2009a), they found that the increase of moisture content from 10 to 15% (w.b.), increased the friability of pellet from the corn stover. Li and Liu (2000) and Ohmberger and Thek (2004) stated that the optimal condition of moisture content for the densification process of woody biomass was between 6 - 12% and 8 - 12%, respectively. However, the pineapple plant residue pellets required higher moisture content to produce optimum condition for friability compared to the corn stover and woody biomass.Thus, 35% of moisture content is the optimum condition for the pellet since the friability test shows that the friability percentage is the lowest compared to others.

3.2 Bulk density

Bulk density had a significant role viewed in transport and storage efficiency. In addition, bulk density provided a strong influence in the form of transport equipment, storage and conversion process (Karunanithy et al., 2012). From Table 1, the mean values of the pellets' bulk density were 303.31±0.01 kg m-3and 345.24 ± 0.02 kg m-3for 35% and 50% moisture content, respectively. For 40% and 45% moisture content, the bulk density had the same value which was 322.92 ± 0.02 kg m-3. Among the feedstocks, moisture content at 35% had the lowest value while moisture content at 50% had the highest value of bulk density. The bulk density of the pellets were found not to increase significantly (P > 0.05) with the increase in moisture content. This result was proven by White and Jayas (2001), whereby they reported that there was no significant difference on bulk density of canola meal pellets by increasing the moisture content. Bulk density of the pellets in this study was higher compared to the corn stover (131 - 158 kg m-3) and switchgrass (115 - 182 kg m-3) as reported by Mani et al. (2005). Similarly, Kaliyan and Morey (2009a) also reported a lower bulk density of 103 - 160 and 181 - 220 kg m-3, respectively, for corn stover and switchgrass. Several researchers have reported that densification would result in bulk densities in the range of 450 to 700 kg m-3 depending upon feedstock and densification conditions (Kaliyan and Morey, 2009b; Kaliyan et al., 2009). Fasina (2008) reported a four-fold reduction of storage space due to the pelletization of peanut hulls. In general, bulk density of the pellet increased 2 - 13 times depending upon the feedstock, densification equipment, and process conditions (Karuranithy et al., 2012). So, the pellets from pineapple waste showed higher bulk density compared to the others, which led to reduced transportation costs, and enabled easier handling with proper storage equipment. Adequate storage space is necessary in order to keep large supply of feedstock safely in hand.

3.3 True density

True density is a fundamental material property for accurate characterization of powder mechanical properties. It measures the average density of a large volume of the powder in a specific medium (usually air). True density of the feedstocks for all the moisture content ranged between 1502.65 to 1520.35 kg m-3, as shown in Table 1. There were significant differences (P < 0.05) in the true density values with increasing moisture content. The results of this experiment exhibited the same pattern as Barnwal et al. (2011), whereby the true density of maize powder decreased with increasing moisture content. Mani et al. (2005) reported lower true density for corn stover (1170-1399 kg m-3) and switchgrass (946-1173 kg m-3) compared to pineapple plant waste (1502.65-1520.35 kg m-3). According to Kaliyan and Morey (2009b), density depended on the types of feedstock, machines and process variables. In conclusion, all the results gave significant differences at P < 0.05, and these true density values were used to determine the percentage of porosity.

3.4 Porosity

Porosity has influence in the transportation and the storage of pellets. Moisture content at 35% yielded the highest porosity value of 80.05% whereas, moisture content at 50%, gave the lowest value of porosity, 77.02%. There were no significant difference (P > 0.05) in terms of the porosity values obtained for all the moisture content (35-50%). The porosity decreased with the increase in moisture content as shown in Table 1. The result is comparable to Karunannithy et al. (2012), whereby it was stated that the feedstocks from sawdust showed 85% of porosity. However, the highest porosity was recorded from cotton stalk, which is 93% of porosity. From the results, low porosity of the feedstock at moisture content 50% indicated that the void space was less and the feedstock within the given volume would result in low compressibility. Furthermore, high porosity of feedstock at moisture content 35% indicated that the sample was compacted, thus resulting in higher compressibility. The results contradicted with Mahapatra et al. (2010), who found that the porosity increased with the increase in moisture content. This might be due to the different types of feedstocks, machines and process variables used (Kaliyan and Morey, 2009b). As a conclusion, 35% of moisture content was inferred as the optimum condition for the pineapple waste pellets due to the higher percentage of porosity and higher compaction obtained, compared to the others.

4. Conclusions

The physicochemical properties of the pineapple waste pellets at different moisture content level, in terms of friability, bulk density, true density and porosity were determined in this research. It could be concluded from this study that moisture content ranging from 35 to 50%, had no significant effect upon the physical characteristics of the pellets except for true density. Based on this research, the best condition for the pellets was at 35% of moisture content with lowest value of friability (0.85 ± 0.28%) and higher value of true density (1520.35 ± 0.35 kg m-3) and porosity (80.05 ± 0.86%). Pelleting could increase the bulk density of the pellets, thus reducing the amount of space required for transportation and storage. Pelleting of pineapple plant waste could potentially increase the utility of this forage as a natural fiber source for ruminants. Pelleting also had an added value of increasing its flexibility for feeding. As a result, densification of pineapple waste into pellets could reduce costs and solve problems related with handling, transportation and storage.


This research was supported by Research Universiti Grant of Universiti Putra Malaysia and Malaysian Pineapple Board (MPIB) for the advised and sample material.


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Accepted for oral presentation in CAFEi 2014 (December 1-3, 2014 - Kuala Lumpur, Malaysia) as paper 79.