CHAPTER ONE

GENERAL INTRODUCTION

1.1 Background of the study

Preservation of fruits, vegetables, and food is essential for keeping them for a long time without further deterioration in the quality of the product.

Several process technologies have been employed on an industrial scale to preserve food products; the major ones are canning, freezing and dehydration.

Among these, drying is especially suitable for developing countries like Cameroon with poorly established low-temperature and thermal processing facilities.

It offers a highly effective and practical means of preservation to reduce post-harvest losses and offset the shortage in supply.

Therefore, fruits and vegetables are agricultural products that are known for their rich vitamins, high concentration of moisture and low fats.

They are highly perishable due to the excess moisture present in them, especially at harvest.

They are seasonal crops and are mostly available during the production season.

They are usually abundant in the markets a few weeks in the year and scarce throughout the next periods of the year.

These significant quantities available¶ in the market cannot entirely be ¶sold, hence, huge losses.

That is why it is more important to reduce vegetable and fruit wastage and improve their storage conditions by drying them.

Drying of product is one of the oldest forms of food preservation methods known to man.

It is the removal of moisture from the product to an optimum level (which the critical rate is about 10 to 15% of moisture depending on the product) in order to prevent deterioration and preserve their nutritive values.

Drying is a simultaneous heat and mass transfer process. The heat stirs up the moisture in the product by external medium usually air.

The relative humidity is a very important factor in drying in that it determines the moisture-holding capacity of the drying air.

Apart from exposing the product to direct sun energy (traditional method of drying), there are indirect (what will be the case in our study) methods of achieving better quality dried products that are free from inefficiencies of sun-drying that is characterized by the problems of losses, contaminations, rewetting and uncontrolled drying rate.

This results in loss of flavour, colour, taste, and case hardening, heat stress and contamination by birds, flies and animal droppings.

Dryers are one of the most important equipment in the food processing industries.

Many dryers have been developed and used to dry agricultural products in order to improve their storage conditions. Most of them use only electricity (hydraulic, photo-voltaique, etc) as a source of energy or a combination of electricity and other forms of energy.

This work is therefore aimed to reduce fruits and vegetable wastage and improving their storage conditions by drying them and reducing as much as possible the moisture.

With the specific objectives of designing and developing an electrical/biomass dryer (using heating resistance and charcoal as biomass type) for rural area and at the end testing the performance of the dryer by drying cassava immediately after harvesting in order to reduce the moisture content from about 70% to  15%.

I.2.Purpose of the study

The main purpose of this study is to investigate the variables affecting the production and preservation of foodstuffs so as to conceive an appropriate drying system to satisfy this need.

 I.3. Scope of study

The study was limited to the conception٫ realization and optimization of a cassava dryer. However٫ our researches were carried out in Bamenda.

I.4.Research questions

The questions to be answered in this study are:

1. How hot air is used for drying?
2. How to proceed to perform the efficiency of our cassava drier?

 I.5. Research Hypothesis

H1: For drying, hot air will circulate across the product by the help of fans (forced convection).

H2: The efficiency of our cassava dryer will be perfomed by using a battery with high power storage.