PROJECT TOPIC- EFFECTS OF MOISTURE AND TEMPERATURE ON THE THERMAL PROPERTIES OF LABLAB BEAN
Knowledge of thermal properties is essential in the efficient and economical design of all food processing operations involving heat transfer. It is also of great importance in the development of thermal models for generating accurate numerical results (sudhaharini, 1997). The knowledge of the thermal properties and how these properties change during processing as a function of temperature are of primary importance in heat transfer processes.
This information is required to make proper design of food processing equipments, especially heat exchangers (de moura et al., 1998). The thermal properties of food often required for heat transfer calculations include, specific heat capacity, thermal conductivity and thermal diffusivity. Thermal conductivity is defined as the ratio of heat flux density to temperature gradient in a food material. It is a measure of the ease with which heat flows through a food material and this property can be used to predict or control heat flux in food processing operations such as cooking, freezing, sterilization, drying or pasteurization (Fontana et al., 1999).
Specific heat or heat capacity is the amount of heat required to raise the temperature of a unit mass of a food material by 10C. It is the ability of a food material to store heat relative to its ability to conduct (loose or gain) heat. Specific heat is an important thermal property used in heat transfer and energy balance calculations (Kaletunç, 2007). Thermal diffusivity is the ratio of thermal conductivity to specific heat and is the rate at which heat diffuses within a food material.
This property helps in estimating processing time of heating cooling, freezing and cooking (Fontana et al., 1999). It is also used in calculating temperature change in storage bins because of fluctuations in external and internal temperature (Irtwange and Igbeka, 2003). Because water is one of the major constituents of food materials, understanding of the effect of moisture content on thermal properties would contribute extensively to analysis of thermal processes (Wang and Brennan, 1993).
Values of most thermal properties of food can be correctly estimated directly from the temperature and moisture content of the food (Lozano, 2000). Lablab bean (Lablab purpureus) is specie in the family Fabaceae. It is native to Africa and it is cultivated throughout the tropics for food. It is also called hyacinth bean, dolichos bean, seim bean, lablab bean, Egyptian kidney bean, Indian bean, chicharo and Australian pea. It is known as ‘Danwari’ in Hausa and ‘Apama’ in Igbo.
The plant is variable due to extensive breeding in cultivation, but in general, they are annual or short-lived perennial vines. The wild species is perennial. Lablab bean can be prepared as porridge, combined with rice and also with maize. The Protein content of lablab bean ranges from 22.4 to 31.3%, fat content 1% and carbohydrate content 46 to 63.3% (Osman, 2007). Lablab is one of the lesser known legumes of arid and semi-arid land.
It is classified by the National Academy of Science (NAS, 1979) as potential source of protein that has not been explored yet. Processing of lablab bean is time-consuming and does not conserve energy, thus, this study will enable Engineers to design processing equipments which will reduce the processing time of lablab bean. A perusal of literature shows that data on the thermal properties of lablab bean does not appear to be available.
- Objective OF Study
The objective of this study is to determine the effects of moisture and temperature on the thermal properties of lablab bean.