JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B. Tech III DAIRY AND FOOD ENGINEEING Previous Question Paper (April - 2018 - R15)
Part A is compulsory which carries 25 marks. Answer all questions in Part A. Part B consists of 5 Units. Answer any one full question from each unit. Each question carries 10 marks and may have a, b and c as sub questions.
PART - A
Explain the Maxwell model.
Answer
The Maxwell model is a viscoelastic model representing a material as a spring and a dashpot connected in series. It describes how a material exhibits both elastic deformation (spring) and viscous flow (dashpot) when subjected to stress, where the total strain is the sum of the elastic and viscous strains.
What is the effect of pH on the milk quality?
Answer
The pH of milk is a critical indicator of its freshness and bacterial quality. Normal fresh milk has a pH between 6.6 and 6.8. A decrease in pH (acidification) indicates the conversion of lactose into lactic acid by bacteria, which leads to souring, curdling during heat treatment, and reduced shelf life.
Write about the procedure of quality evaluation of milk before processing.
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Discuss the method of Pasteurization.
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Write the importance of emulsifier in butter manufacturing.
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Enlist basic factors/parameters for the designing of dairy plant, discuss any one.
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Discuss the hysteresis effect during drying.
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Write about boiling point elevation.
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Write Mechanism of Ultra-filtration.
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What is reaction kinetics? Write their application in food engineering.
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PART - B
Enlist the Physico-chemical properties of milk. Explain physical properties of milk.
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Milk is balanced diet. If yes or no and then why.
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Why does the acidity of fresh milk change after it kept under ambient condition? Name the properties of the milk which are helpful in detecting adulteration.
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What is centrifugation? Explain their principles.
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Explain the process of sterilization in packages and cold point.
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Explain the working principle and mode of operation of Vat.
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Discuss the effect of high temperature on nutritive value of milk.
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Write the microbiology of fresh milk.
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Discuss the factors that affect the growth or multiplication of microorganisms.
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What is spoilage? Discuss the causes of food/milk spoilage.
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Discuss the Process of cream churning. Draw flow chart of cream manufacturing process.
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Define chemical preservatives. Write about various chemical preservative with their effect on product quality.
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2000 kg of paddy with 24% moisture on wet basis are to be dried to 13 % moisture content (wet basis). Calculate the weight of bone dry products and water evaporated.
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Explain in details the spray drying of liquid food products. Discuss Instantization process to make dry powder instant soluble.
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What is evaporation/concentration? Discuss the Mass and heat balance for single effect evaporator with suitable figure.
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Potato flakes (moisture = 75% wb) are being dried in a concurrent flow dryer. It was found that 70% of original water has been removed in a dryer. Determine (i) mass of water removed/kg of potato flakes, (ii) composition of dried potato.
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Five centimeter potato cubes are individually quick frozen (IQF) in a blast freezer operating at -40°C and with a surface heat transfer coefficient of 30 W/m² K. If the freezing point of the potato is measured as -1.0°C and the density is 1180 kg/m³, calculate the expected freezing time for each cube. If the cubes are then packed into a card board carton measuring 20cm × 10cm × 10cm, calculate the freezing time. Also calculate the freezing time for IQF freezing of 2.5 cm cubes. (Additional data: the thickness of cardboard is 1.5 mm, the thermal conductivity of the card is 0.07 W/mK, the thermal conductivity of potato is 2.5 W/mK and the latent heat of crystallization is 2.74 × 10&sup5; J/kg.
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Define filtration. Discuss the Filtration theory with neat diagram.
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Write about Thermal death time curve and First order reaction kinetics.
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Explain the freezing curve for a food with neat diagram.
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