Afs2301:Food Engineering Question Paper
Afs2301:Food Engineering
Course:Bachelor Of Science In Food Science And Nutrition
Institution: Meru University Of Science And Technology question papers
Exam Year:2014
QUESTION ONE – (30 MARKS)
(a) What do you understand by the law of conservation of energy and mass? (2 Marks) (b) Briefly define or discuss these terms as encountered in food engineering. (i) Specific heat capacity (ii) D-value (iii) Reverse osmosis (iv) Rising film evaporator (v) Laminar flow (5 Marks) (c) Dry foods heat poorly in a microwave oven. Briefly discuss. (3 Marks) (d) What is the quantity of heat required to raise the temperature of 20 litres of milk from 22°?? to 78°??. Take mean heat capacity of milk to be 4.0???? ????-1??-1. (3 Marks) (e) Briefly discuss the principle of a fluidized bed drier. (3 Marks) (f) A student was carrying out an experiment and obtained the following data. Calculate Dvalue during cooking of a food sample at constant temperature. Time (min) Number of Micro-organisms 0 2 × 105 3 4.3 × 104 6.5 6.32 × 103 8 2.0 × 103 (3 Marks)
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(g) Discuss one application of size reduction in liquid food product suggesting the equipment you would employ. (3 Marks) (h) Briefly discuss the principle of pulsed electric fields as a non-thermal food preservation method. (3 Marks) (i) Calculate ‘g’ in a centrifuge that can spin at 2000 rev/min with a maximum radius of 20cm. (3 Marks) (j) Why are consumers opting for minimally processed food product? (2 Marks)
QUESTION TWO – (20 MARKS)
(a) A cook observed that when equal amount of cooking oil and water are subjected to the same amount of head, oil heats faster, discuss. (4 Marks) (b) A cold storage wall (3??6????) is constructed of 15cm thick concrete (thermal conductivity is 1.37??/??°??) insulation must be provided to maintain a heat transfer rate through the wall at or below 0.05??/??°??. Calculate the required thickness of the insulation. The outside surface temperature of the wall is 38°?? and the inside wall temperature is 5°??. (10 Marks) (c) A cook bought two frozen samples A and B. After thawing process, there were large pools of blood under sample A compared to B. Discuss. (3 Marks) (d) Discuss the principle of ultrasound in food preservation. (3 Marks)
QUESTION THREE – (20 MARKS)
(a) Discuss four non-thermal food processing technologies highlighting the principles. (8 Marks) (b) How much sugar must be added to 300kg of aqueous sugar solution in order to increase the concentration form 20 to 60 %. (4 Marks) (c) Food sample was ground from an average size of 500??m in diameter to an average size in diameter of 100??m. The net energy consumption was 0.6kw/h per tonne. What would be the net energy consumption for reducing the particles to 20??m diameter product; (i) According to Rettinger’s law (3 Marks) (ii) According to Kick’s law (3 Marks) (d) Surface hardening is a problem encountered in drying. Discuss steps you would take to minimize chances of surface hardening. (2 Marks)
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QUESTION FOUR – (20 MARKS)
(a) Discuss the principles by which microwave oven heat food. (8 Marks)
(b) Discuss four application of emulsification in food industry. (8 Marks)
(c) 1000kg of a juice stream contained 10% weight of suspended pulp which are separated in a vacuum filter to produce clear juice and wet solids containing 20% moisture. How much of clean juice and wet solid is produced. (4 Marks)
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