Mass Transfer - Food Engineering - Engineering Sciences Previous Year Questions

1

2008 · Engineering Sciences · Food Engineering · Mass Transfer

Engineering Sciences (XE) 2008

Convective mass transfer coefficient of water vapour diffusing from a water surface to air depends primarily on

A

velocity of air

B

viscosity of water vapour

C

density of water vapour

D

specific heat of water vapour

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2

2008 · Engineering Sciences · Food Engineering · Mass Transfer

Engineering Sciences (XE) 2008

Two food materials A and B, each having 14% moisture content (dry basis) are stored in a constant relative humidity chamber at 30°C for equilibration. The final moisture contents of A and B are 6% and 12% (both in dry basis), respectively. The final water activity a_wA of A and a_wB of B are related as

A

a_wA : a_wB = 0.65:1

B

a_wA : a_wB = 1:1

C

a_wA : a_wB = 1.2

D

a_wA : a_wB = 2:1

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3

2009 · Engineering Sciences · Food Engineering · Mass Transfer

Engineering Sciences (XE) 2009

At atmospheric pressure, the solubilities of CO₂ in a beverage at 15.5 °C and 0 °C are 1.0 volume and 1.7 volume respectively. The pressure (in atm.) required to carbonate the beverage at 4.5 °C so as to maintain a gas volume of 4.0 is

A

1.04

B

1.47

C

1.67

D

1.76

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4

2012 · Engineering Sciences · Food Engineering · Mass Transfer

Engineering Sciences (XE) 2012

The rate of drying (in kg/h) is

A

128.79

B

126.35

C

77.81

D

0.0485

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5

2014 · Engineering Sciences · Food Engineering · Mass Transfer

Engineering Sciences (XE) 2014

For a typical food sorption isotherm curve (Figure 1), which one of the following statements is CORRECT ?

A

Y-coordinate of A represents monolayer water content of food, A-B represents water absorbed in the multilayer within the food and B-C represents free water within the capillary network of the food.

B

Y-coordinate of B represents monolayer water content of food, A-B represents water absorbed in the multilayer within the food and B-C represents free water within the capillary network of the food.

C

Y-coordinate of A represents monolayer water content of food, Y-coordinate of B represents water absorbed in the multilayer within the food and B-C represents free water within the capillary network of the food.

D

Y-coordinate of A represents monolayer water content of food, A-C represents water absorbed in the multilayer within the food and Y-coordinate of C represents free water within the capillary network of the food.

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6

2016 · Engineering Sciences · Food Engineering · Mass Transfer

Engineering Sciences (XE) 2016

Which one of the following is not used in mass transfer analysis?

A

Biot number

B

Peclet number

C

Schmidt number

D

Sherwood number

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7

2017 · Engineering Sciences · Food Engineering · Mass Transfer

Engineering Sciences (XE) 2017

Bread is wrapped in 0.1 mm thick cellophane film having water vapour permeability of 1.82 x 10^-10 m³ water (STP)/s.m².atm/m at 38 °C. If the surface area of pack, vapour pressure of water inside and outside of the pack is 0.20 m², 10 mm Hg and 5 mm Hg, respectively, the loss of water vapour at 38 °C in g/day is ______ .

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8

2018 · Engineering Sciences · Food Engineering · Mass Transfer

Engineering Sciences (XE) 2018

Identify an example of a classical diffusional mass transfer process without involving heat, among the following.

A

Drying of food grains

B

Carbonation of beverages

C

Distillation of alcohol

D

Concentration of fruit juice

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9

2018 · Engineering Sciences · Food Engineering · Mass Transfer

Engineering Sciences (XE) 2018

The oxygen transmission rate through a 2.54 x 10^-3 cm thick low density polyethylene film with air on one side and inert gas on the other side is 3.5 x 10^-6 mL cm^-2 s^-1. Oxygen partial pressure difference across the film is 0.21 atm. The permeability coefficient of the film to oxygen is _____ x 10^-11 mL (STP) cm cm^-2 s^-1 (cm Hg)^-1.

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10

2019 · Engineering Sciences · Food Engineering · Mass Transfer

Engineering Sciences (XE) 2019

A shallow-bed horizontal belt type solvent extractor is operating on 0.3 mm thick soybean flakes with 0.5 m bed depth and a forward speed of 0.8 m min⁻¹ with miscella flux rate of 0.25 m min⁻¹. If porosity of the flakes is 60%, the distance between washing nozzle and miscella collecting receptacle (cm) is __________ (round off to 1 decimal place).

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11

2019 · Engineering Sciences · Food Engineering · Mass Transfer

Engineering Sciences (XE) 2019

An extruded snack food is packed in a barrier film having water vapour transmission rate of 0.02 mL m⁻² day⁻¹. Pack surface area is 0.0012 m² per gram of dry food solids, EMC of the food is 6% (d.b.), initial moisture content is 2% (d.b.), critical moisture content is 5% (d.b.) and slope of moisture sorption isotherm is 3.4% (d.b.) per unit water activity (a_w). Sealed pack is stored at 30 °C. Assume that the vapor pressure of pure water at 30 °C is 31.7 torr. Time required for the food to reach the critical moisture content (days) is __________ (round off to 1 decimal place).

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12

2021 · Engineering Sciences · Food Engineering · Mass Transfer

Engineering Sciences (XE) 2021

Match unit operation in Column I with its application in food processing in Column II.

Column I	Column II
P. Hydrogenation	1. Removal of soft wax
Q. Blanching	2. Shortening of fat
R. Leaching	3. Inactivation of enzyme
S. Winterization	4. Separation of dye

A

P-2, Q-4, R-2, S-1

B

P-2, Q-3, R-4, S-1

C

P-4, Q-1, R-2, S-3

D

P-4, Q-2, R-1, S-3

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13

2021 · Engineering Sciences · Food Engineering · Mass Transfer

Engineering Sciences (XE) 2021

Which of the followings is/are commonly used medium/media in the supercritical fluid extraction of spices and tea?

A

Water

B

Carbon dioxide

C

Dichloromethane

D

Carbon dioxide with Ethanol

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14

2024 · Engineering Sciences · Food Engineering · Mass Transfer

Engineering Sciences (XE) 2024

Which one of the following statements regarding moisture sorption isotherms of a dried food is NOT correct?

A

At a given temperature, the difference between adsorption and desorption moisture isotherms is known as hysteresis.

B

At a given temperature and water activity, an adsorption isotherm exhibits higher equilibrium moisture content than a desorption isotherm in hysteresis.

C

At a given moisture content, effect of temperature on a moisture sorption isotherm follows the Clausius- Clapeyron equation.

D

The Guggenheim-Anderson-de Boer (GAB) equation is a multilayer moisture sorption model.

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15

2024 · Engineering Sciences · Food Engineering · Mass Transfer

Engineering Sciences (XE) 2024

A 2 mm thick palladium sheet of \(1000 \ mm^2\) cross section is used as a diffusional membrane to purify hydrogen. The hydrogen concentration is maintained at a steady state with \(c_h = 1.5 \ kg \ m^{-3}\) and \(c_l = 0.3 \ kg \ m^{-3}\) on the two sides of the membrane as shown in the figure below.
The rate of hydrogen purification is (in units of \(kg \ hr^{-1}\)) \(\_\_\_\_\_ \times 10^{-6}\) (rounded off to one decimal place).
Given: The diffusion coefficient of hydrogen in palladium is \(1.0 \times 10^{-8} \ m^2 \ s^{-1}\).

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16

2025 · Engineering Sciences · Food Engineering · Mass Transfer

Engineering Sciences (XE) 2025

At 873 K, hydrogen diffuses under steady state condition through a 5 mm thick palladium sheet with a cross-sectional area of \( 0.3 \; m^2 \). The concentrations of hydrogen at high and low pressure ends of the sheet are \( 3 \; kg \; m^{-3} \) and \( 0.5 \; kg \; m^{-3} \), respectively. The amount of hydrogen (in kg per day) passing through the sheet is (rounded off to two decimal places)__________
Given: At 873 K, diffusivity of hydrogen = \( 1.8 \times 10^{-8} \; m^2 \; s^{-1} \)

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17

2025 · Engineering Sciences · Food Engineering · Mass Transfer

Engineering Sciences (XE) 2025

A fruit juice is concentrated using an ultrafiltration membrane. A feed stream at 10 kg/min with 6% total solids (by weight) is increased to 20% total solids (by weight). The membrane tube has 10 cm inside diameter and the pressure difference across the membrane is 2000 kPa. If the permeability constant of the membrane is \(5 \times 10^{-5}\) kg water/ (m\(^2\) kPa s), the length of membrane tube (in m) is _______. (rounded off to 2 decimal places)

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