Design, Fabrication And Performance Evaluation Of Pedal Operated Groundnut Decorticator

CHAPTER THREE
MATERIAL AND METHODS
3.1    Physical Properties of Biological Materials
    Physical properties are any property that is measurable, whose value describe a state of a physical system.  Physical property can be observed or measured without changing the composition of matter. Physical properties are use to observed and describe matter.  Physical properties include: size, shape, volume, porosity, weight, density, moisture content and colour.
Groundnut (Arachis hypogea) is one of the major export crops of Northern Nigeria. The mechanization of the post-harvest shelling of groundnuts and other legumes, such as cowpea and soyabean produce in Nigeria is long overdue (Asota et al.,2006,).  
3.1.1    Sample Preparation
The groundnut seed (Arachis hypogea) used for all the experiments in this study (Plate.3.1) were purchased from produce merchant in Ilorin, Kwara State, Nigeria. The seeds were cleaned in an air screen cleaner to remove all foreign materials such as dust, dirt and chaff as well as immature and damaged seeds.

3.1.2    Determination of Size and Shape
To determine the average size of a groundnut seed, hundred samples were randomly selected from the bulk of groundnut pods .The length, breadth and thickness of each groundnut pod and seed were determined by measurements using vernier calipers with an accuracy of ±0.1mm. (Sinsomboon, 2009)
    The geometric mean diameter (Dg) was determined using the following equation as given by (Mohsenin, 2008):
Dg=〖(lbt)〗^(1/3)                                     (3.1)
    The sphericity (S) of the seed was also calculated as given by (Mohsenin, 2008):
S=〖(lbt)〗^(1/3)/l                                    (3.2)
    The indices used to describe the shape of groundnut seed in this study is based on the sphericity and the geometric mean diameter.
3.1.3    Determination of Moisture Content
The moisture contents of groundnut seeds were determine using the oven drying method as expressed by (Chakrayerty, et al., 2004).  The initial weights of samples were determined using the digital balance.  Triplicate samples were dried in air-convection oven set at temperature of 1030C and monitored over a period of 6 hours at 30 minutes intervals until the weights of the samples were found to be constant.  Moisture content on dry basis, Mcdb was determined by Oven drying method at 130oC for 6hrs as reported by Chakraverty, (2004).
Moisture Content db=(W_1- W_d)/W_d  x 100%
3.1.4    Determination of Mass, Volume and Density
    The mass of 100 unit of groundnut kernel was measured using a digital weighing scale of 0.1g accuracy while the volume was determined using water displacement method. A known volume of distilled water was put in a measuring cylinder while the seed was then poured into the cylinder the change in level of the water in the cylinder is taken as the volume of the seed. The density was then computed using the relation given by Ndrika, (2004) as:
    Bulk density , Bd ="mass(g)" /("volume(" 〖cm〗^3 ")" )                        (3.3)