eChapters

Theory

Removal of outer sheath is called husking and removal of kernel from maize from maize cob is called shelling. The performance of the sheller is expressed in terms of capacity, percentage of unshelled kernels (corn) and percentage of breakage. The above terms are defined as:

Aim

To determine the efficiency of groundnut decorticator

Apparatus required

Manually operated groundnut decorticator

Weighing balance

Groundnut pods

Aim

To determine the effectiveness of the spiral separator.

Materials required

Spiral separator

Weighing balance

Sample divider

Stopwatch

Grain mixture (round and others)

Aim

To evaluate the performance of the gravity separator.

Materials required

Specific gravity separator

Weighing balance

Sample divider

Stopwatch

Grains

Aim

To determine the effectiveness of inclined belt separator

To determine the capacity of inclined belt separator

Materials required

Inclined belt separator

Weighing balance

Feed material

Sample divider

Aim

To study the working principle and cleaning efficiency of air-screen seed cleaner cum grader

Apparatus required

Lab model air-screen seed cleaner cum grader

Seed sample

Weighing balance

Theory

Fluidized bed drying is a method of drying by keeping the material in fluidized/ floating condition inside a chamber by hot air. In this drying process higher rate of moisture migration takes place.

Aim

To draw the drying characteristic curve for given grain by thin layer drying.

To determine the drying constant, heat utilization factor and coefficient of performance.

Aim

To study the determination of drying rate of agricultural products

Problem

In a drying experiment on paddy at an air temperature of 60ºC, the following data were obtained. Prepare a drying rate curve for the experiment. Initial weight of the sample is 1250 gm and initial moisture content is 35% (d.b).

Aim

To study the numerical problems on grain moisture content and equilibrium moisture content.

Problem 1

Five hundred kilograms of paddy at 22% moisture content (wb) is dried to 14% moisture content (wb) for milling. Calculate the amount of moisture removed in drying.

Theory

This type of moisture measurement is called brown-duvel fractional distillation method. The method is recognized as an official method for determination of moisture content. In this method, directly measures the volume of moisture in cubic centimeter. This apparatus consists of flask, burner, thermometer, condenser, graduated cylinder. This apparatus consists of flask in which grain sample is boiled with mineral oil.

Theory

Indirect methods are based on the measurement of electrical properties of the grain that depends upon moisture content. There are two indirect methods namely (i) electrical resistance and (ii) dielectric methods are used. The electrical conductivity or resistance of a product measures its moisture content at a given compaction and temperature. The electrical resistance is depends on its moisture content, degree of compaction, grain temperature and impurities present in the sample. The universal digital moisture meter measures the electrical resistance of the grain at a given compaction. Universal moisture meter gives fairly accurate readings of moisture content on wet basis. In dielectric method, grain moisture content can be measured with the help of dielectric properties of the grains.

Theory

The amount of moisture in a product is given on the basis of the weight of water present in the product and is usually expressed in percent. Moisture content is designated by (i) wet basis (wb) and (ii) Dry basis (db). The moisture content on dry basis is more simple to use in calculation as the quantity of moisture present at any time is directly proportional to the moisture content on dry basis.

Theory

Texture testing is a well-established technique for evaluating the mechanical properties of raw materials, food structure, pre- and post- harvest quality control checks. The texture testing has many applications across wide range of foods including cereals, fruits, vegetables, meat, poultry, fish, baked foods, confectionaries, snacks, dairy, gelatins, pasta, etc. Food texture analysis of foods can highlight the quality improvement throughout the supply chain. At research and development stage, new or alternative ingredients can be compared with existing ingredients.

Texture profile parameters

The texture profile parameters including hardness, firmness, crispiness, rupture strength springiness, chewiness, cohesiveness, gumminess, gel strength, adhesiveness, consistency, crunchiness, elasticity, extensibility, fracturability, stiffness, stringiness, toughness, work to cut, penetrate and shear can be measured by the mechanical food texture analyzer.

Theory

The energy available in food is expressed in unit is called joules or calories. One kilocalorie is equal to 4.184 kilojoules. The kilocalorie is defined as the amount of heat required to raise the temperature of 1 kg of water by 1°C. The calorific/ energy value of foods is usually determined using the instrument called bomb calorimeter. It is working based on the principles of calorimetry. Basically, this device burns a food sample and transfers the heat into a known mass of water. It measures the heat produced when the food sample is ignited by an electric spark in the presence of oxygen and platinum which acts as a catalyst. The quantity of food sample to be tested is placed inner part and known volume of water is taken in outer part of the bomb calorimeter. When the food sample is electrically ignited, the surrounding water absorbs the heat produced. The energy value of the food is calculated by measuring the rise in temperature of water.

Theory

Specific heat is defined as the amount of heat needed to raise the temperature of one kg of the material by one degree at constant pressure without a change in state. With food materials, specific heat is a function of different components of a food, moisture content, temperature, and pressure. Specific heat is an important parameter in thermal analysis of food processing and equipment used in heating or cooling of foods. The numerical values of specific heat of the food materials are used in designing food processes and processing equipment. It can be used to calculate the heat load imposed on the refrigeration equipment by the freezing of foods. An apparent specific heat is used in freezing or thawing and in most food processing applications.

The specific heat of a food increases as the product moisture content increases. In unfrozen foods, specific heat capacity is relatively constant with respect to temperature. However, for frozen foods, there is a large decrease in specific heat capacity as the temperature decreases. The specific heat of a material can be determined experimentally by static (adiabatic) calorimetry or differential scanning calorimetry. It can be also predicted quite accurately with the help of a number of empirical equations. The equations are empirical expressions, obtained by fitting experimental data into mathematical models. The mathematical models are based on one or more constituents of the food. Since water is a major component of many foods, a number of models are expressed as a function of water content.

Aim

To determine the thermal conductivity of the agricultural materials probe method.

Materials required

Thermal conductivity probe

Stainless-steel sample container

Grain or powder sample

Graph sheet

Power source

Aim

To determine the angle of repose of the given biological materials.

Materials required

Angle of repose apparatus
Grains
Scale

Aim

To determine the water solubility and absorption index of given food powder.

Materials required

Digital centrifuge machine

Graduated measuring cylinder

Beaker and distilled water

Theory

The volume of food material play an important role in design of storage bins, conveying equipments, separation equipments, etc. Volume of larger products such as fruits and root crops can be determined using the platform scale or water displacement method.