Different alternative pellet binders affect the durability and density of Indigofera pellet

Indigofera is one of the many legumes that contains high protein which can be utilized as ruminant protein source. Indigofera utilization for feed industries may be limited by its volume especially during transportation. To reduce high volume of Indigofera transportation, pelleting is needed. Binder is one of the main components in producing pellet. This research aimed to analyse the effect of different binders in the durability, bulk density, density, organic matter content, dry matter content, and crude protein content of Indigofera pellet. The treatments used were LignoBond DD ® as standard binder, sago flour, cornstarch, and tapioca flour. The results showed that pellet durability and density were significantly affected by pellet binder while bulk density, organic matter, dry matter, and crude protein were not affected. The best alternative pellet binder that has the same result as LignoBond® as standard binder is tapioca flour.


Introduction
Ruminant protein source is limited only from plant-based protein, therefore abundant plant-based protein is needed to maintain the quality of ruminant feed.Indigofera is one of the many options available for plant-source protein for ruminant.Indigofera is highly adaptive protein-packed plant that can be found in many types of land, from dry, muddy, acid, to high salinity soils [1,2].The protein content of Indigofera leaves sampled from across Indonesia are ranged from 29 -30% [2].Indigofera is good forage for ruminants not only because of its high-protein content, but also due to its low tannin and saponin content which ranged from 2.4-7% and 0.8-1.2%,consecutively [3,2].
The abundant source of Indigofera leaves in Southeast Sulawesi is potential for ruminant feed sustainability, even it can supply the need of ruminant feed in other regions, especially in densely populated area where forage source is limited.However, Indigofera leaves are voluminous, thus hinder the effectiveness of its transportation.The great distance between regions in Indonesia caused the decreased physical and chemical quality in the Indigofera transported.In order to reduce the decrease in its quality, turning Indigofera leaves into pellet may be beneficial.By making green forage into dry matter pellet can reduce the storage up to five times because most forage contains about 80% water [4].
Pellet is feed materials that were mixed, then compacted and moulded by mechanical process [5].By converting raw materials into pellet, the density of the materials can be increased and transport of materials can be more efficient [6].Pelleting includes many steps that may increase the risk of crumbling the pellet either during production, delivery, or storage.The use of pellet binder in producing green forage pellet is crucial.Pellet binder is the material added in the pellet mixture in order to bind all the feed materials and maintain the shape of pellet [7].There are some natural materials that can be used as pellet binder.The main characteristic for pellet binder is the high content of starch, such as contained in cornstarch, cassava flour, rice flour, wheat flour, tapioca flour, molasses etc. [4].This research aimed to analyze the physical and chemical qualities of Indigofera leaves pellet made with different binders.

Materials and Methods
The materials used in this research were Indigofera leaves, tapioca flour, sago flour, cornstarch, and LignoBond ® DD binder.The equipment used were blender, disc mill, digital scale, pellet machine, oven, and Kjeldahl analysis kit.The research used completely random design with four types of binder (LignoBond DD®, tapioca flour, sago flour, and cornstarch) as treatments and four replications.The data collected was then analyzed by ANOVA and continued by Duncan's Multiple Range Test.
Indigofera leaves were collected from Southeast Sulawesi area, then dried under the sunlight.The dried leaves were then grinded into fine powder.The pellet production was done by weighing Indigofera powder and the various binders with the ratio of 100:1; then adding 20% of water and mixed thoroughly; the mixture then was put into pellet machine with the mould diameter of 8 mm [8].The moulded pellet was then dried by 60 0 C oven for two days.The final product was then examined for physical quality and nutrient content after 2 weeks storage.
The durability of Indigofera pellet was examined by spinning 500 grams of pellet into tumbling box with 50 RPM of speed for 10 minutes, then was sieved [4].The pellet durability index was then evaluated by counting the percentage of after-spinning and before-spinning weight [9].The bulk density (gcm -3 ) was evaluated by comparing the pellet mass with its volume.The relative density (gml -1 ) was evaluated by statter test [10].The organic matter, dry matter, and crude protein content were evaluated by standard Kjeldahl method [11].

Durability
The durability of pellet is described as the ability of pellet to resist attritions against physical impact, friction, and pressure during storage and transport [12,13].The higher pellet durability indicates that the pellet is more resistant to impact thus lengthen the pellet strength during storage and transport.The durability of Indigofera pellet obtained in this study ranges from 91.07%±0.81 to 93.96%±0.56.Different alternative binders used in producing Indigofera leaves pellets did not differ greatly from LignoBond DD ® as the standard binder.Pellets produced with cornstarch binder was significantly less durable than other binders (LignoBond ®, sago flour, and tapioca flour).The durability, density, relative density, organic matter, dry matter, and crude protein content of Indigofera pellets made with different binders showed in table 1.
The highest durability index was obtained in tapioca flour binder treatment (93.96%±0.56).This might be caused by the amylose content of tapioca flour which reach 20-28% [14,15].Binder acts in maintaining the pellet shape and make sure the pellet remains intact [16].Alternative natural binders used in this research showed the same durability index as the pellet made with standard LignoBond DD ® binder.This can be assumed that tapioca and sago flour may be used as the alternative for Indigofera pellet binders.

Bulk Density
The bulk density of pellets is used to determine compactness and texture of pellets.The compact texture of pellet mixture contributes in maintaining its shape and reducing air pockets under pressurization during pellet making.The results of this research showed that using varied pellet binders did not affect the bulk density of Indigofera leaves pellet.Sago flour, cornstarch, and tapioca flour used as Indigofera pellet binder did not reduce the density of pellet compared to standard use of LignoBond DD ® binder.It can be assumed that the starch contained in sago, tapioca flour and cornstarch can maintain the compact texture of Indigofera pellet as well as LignoBond DD ®.

Density
Pellet density indicates the pellet mass that can be contained compared to its volume.The higher pellet density showed that more masses can be packed in the same volume [17].The highest Indigofera pellet density obtained in this research was showed in tapioca flour treatment, which did not differ from LignoBond DD ® treatment.The lowest density was showed in pellets made with sago flour binder.The difference in pellet density might be due to the varied ability of starch and lignin contained in each binder to bind the Indigofera flour during pellet production.The Indigofera pellet density obtained in this research is higher than Indigofera pellet observed in Febrianti et al [18] which ranged from 1.05 -1.18 gcm-3, but lower than Gliricidia pellet observed in Royani and Herawati [17] which ranged from 1.66 -2.00 gcm-3.

Chemical properties of Indigofera pellets
The dry matter, organic matter, and crude protein content of Indigofera pellets made with natural binders (sago flour, tapioca flour, cornstarch) showed no significant difference compared to LignoBond DD ®.This can be assumed that the use of natural binders did not affect the nutrition content of Indigofera pellets.Dry matter of Indigofera pellet is in reverse with its water content.Higher water contents increased the risk of mold growth and reducing the qualities of pellet.The maximum water content of pellet is around 12-14% [19].
Organic matters are mostly composed of carbohydrates, crude protein, crude fat, crude fiber, and vitamin [20].Different binders used in this research did not affect the organic matter of Indigofera leaves pellet.Organic matter of Indigofera pellet observed in this research are close to the organic matter of kikuyu grass pellet made with different binder which are ranged from 82.89 -86.34% [21].
The crude protein content of Indigofera pellet made from various binders did not differ.The observed crude protein content of Indigofera pellet in this research are ranged from 25 -26%, which is lower than the protein observed in Antari et al [2] which ranged from 28 -34%, but the same as observed in Kumalasari et al [22] which ranged from 25 -26%.The results of this research showed that natural binders may be used to substitute commercial binder without affecting the dry matter, organic matter, and crude protein content of Indigofera pellets.

Conclusion
The use of alternative, more natural binder in producing Indigofera pellet is proved to increased durability and density of Indigofera pellet while maintaining the nutrient content of Indigofera.The best alternative binder for Indigofera pellet that is on par with LignoBond DD ® as standard pellet binder is 1% tapioca flour.

Table 1 .
Physical and nutrient qualities of Indigofera leaves pellets with different binders