Food Processing Unit Operations Multiple Choice Questions on “Sun Drying”.
1. Why meats are not recommended for out-of-doors drying?
a) Meats are high in protein, making them ideal for microbial growth
b) Meat gets decomposed easily
c) Meat absorbs the outdoor odours
d) Vitamin B12 is lost during sun drying
Answer: a
Clarification: Meats are high in protein, making them ideal for microbial growth. Along with the microbial spoilage it can also undergo oxidation and enzymatic autolysis which further decreases the quality of the meat.
2. What is hybrid solar dryer?
a) It is designed and constructed using direct solar energy and a heat exchanger.
b) It represents solar dyer but uses irradiation instead of sun rays
c) It is designed and constructed using direct solar energy and irradiation rays
d) It is used for only hybrid and genetically modified foods
Answer: a
Clarification: A hybrid solar dryer was designed and constructed using direct solar energy and a heat exchanger. The dryer was operated during normal sunny days as a solar dryer. Drying is carried out at night with stored heat energy in water which was collected during the sun-shine time and with electric heaters.
3. What is the lower limit of moisture content by sun drying method?
a) 15%
b) 10%
c) 8%
d) 13%
Answer: a
Clarification: The lower limit of moisture content by sun drying method is approximately 15%. For sun drying of foods, hot days are required with minimum temperatures of 35°C and also with the low humidity.
4. Is sun drying and solar drying same?
a) True
b) False
Answer: b
Clarification: In sun drying, the product is exposed directly to solar radiation and more or less effectively to the wind. In solar drying, the produce is contained in an enclosed space, and the air in contact with it is heated by solar radiation.
5. Are these statements about the location for the sun drying true?
Statement 1:Low lying swampy areas are preferred for the sun drying of the products.
Statement 2:High relative humidity is preferred.
a) True, False
b) True, True
c) False, True
d) False, False
Answer: d
Clarification: The location for the sun drying is selected to take the maximum advantage of climatic conditions. Low lying swampy areas with a high relative humidity should be avoided and racks should be sited away from forests or high buildings which will reduce the air movement or cast a shadow over the racks.
6. What are the modes of heat transfer employed in solar drying systems?
a) Radiation and convection
b) Conduction and convection
c) Conduction and radiation
d) Radiation and conduction
Answer: a
Clarification: Solar drying systems can be categorized mostly on the basis of the mode of transfer of heat engaged. These are radiation and forced convection. Drying is a twofold process which includes 1.The heat transfer to the product from a heating source and 2.Mass transfer of moisture from the interior of the product to its surface and from the surface to the surrounding air.
7. Are these statements about the solar dryer true?
Statement 1: It is designed to collect and enhance solar radiation.
Statement 2: This drier is faster than sun-drying
a) True, False
b) True, True
c) False, True
d) False, False
Answer: b
Clarification: Solar dryer is designed to collect and enhance solar radiation. This drier is faster than sun drying and also requires less drying area but cannot be used on cloudy days.
8. What type of air temperature and humidity do the solar driers generate?
a) Highair temperature, lowhumidity
b) Lowair temperature, high humidity
c) Lowair temperature, lowhumidity
d) Highair temperature, highhumidity
Answer: a
Clarification: Solar driers generate low humidity and high air temperature which results in faster drying. Solar driers are more expensive that natural sun drying but is faster compared to the sun drying.
9. What are advantages of sun drying?
a) Economical and environmentally friendly
b) Fast drying and environmentally friendly
c) Environmentally friendly
d) Economical
Answer: a
Clarification: Sun drying is the most common, cost-effective and environmentally friendly method of preservation of agricultural products. The demerits of this process are that exposure of produce to weather elements such as rain, UV rays of the sun, contamination by wind-borne dirt and infestation by pests and other microbes.
10. Which of the following is an important parameter in sun drying rate?
a) Convective heat transfer coefficient
b) Conductive heat transfer coefficient
c) Mass transfer coefficient
d) Dynamic mass transfer coefficient
Answer: a
Clarification: A portion of the sun radiation incident on the uneven surface of the groundnut reflects back into the environment. The remaining part of the sun energy is absorbed by the product surface and hence increases the product surface temperature which propagates the water vapor formation inside the product. Then the diffusion of water vapor gets started and the mass of the product decreases from the surface of the product.