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The main objective of this research was to develop a mathematical model of heat and mass balance of the bread baking process to predict the temperature and water content of bread at different heating temperatures and times. The model was able to predict the bread temperature and water content at different oven temperatures (180, 190, 200, 210 and 220°C). The results showed that the bread temperature and weight loss of bread increase with increasing oven temperature, when, the oven temperature increased from 180 to 220°C, the temperature of bread increased from 112.73 to 168.49°C and the weight loss of bread increased from 22.40 to 52.46%. The results also showed that the bread temperature and weight loss of bread increase with increasing time, this increment starts to decline after 18-20 min, until it reach equilibrium after 30 min. The weight loss of bread increases with increasing bread temperature. It indicates that when the bread temperature increased from 20.00 to 131.69°C, the weight loss of bread increased from 0.00 to 40.79% at 200°C oven temperature. The model was validated with an experimental data and showed a reasonable agreement with those measured, where; it ranged 20.00 to 131.69°C theoretically while it was from 25.00 to 119.00°C experimentally during the baking at 200°C oven temperature. The weight loss data was in a reasonable agreement with those measured, where; it ranged 0.00 to 40.79% theoretically while it was from 0.00 to 48.69% experimentally during the baking at 200°C oven temperature.

The main aim of this work is to study the effect of water temperature on masculinization, growth and survival of Nile tilapia. To achieve that two experiments were carried out to study the effect of water temperatures (25°C, 30°C and 35°C) and periods of time (1, 2, 3 and 4 weeks) on the male ratio, mortality rate and weight of Nile tilapia fry in the first experiment. While the second experiment aimed to evaluate the growth and survival rate of sex reversed tilapia fry which obtained from the first experiment. The obtained results indicated that the male ratio and mortality rate increased with increasing the water temperature and period of time rearing. The highest value of male ratio and mortality rate (91.50% and 17.13%) was obtained at 35°C water temperature and four weeks of rearing. The weight of Nile tilapia fry significantly increased from 0.16 to 1.51 g, 0.30 to 2.67 g and 0.27 to 2.05 g at 25°C, 30°C and 35°C, respectively after 1, 2, 3 and 4 weeks of rearing. The Nile tilapia fry previously treated by water temperature and period of time rearing increased each of body weight, weight gain and specific growth rate, while the feed conversion ratio decreased with increasing the water temperature and period of time rearing.

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