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Protein quality: It is the digestibility and quantity of essential amino acids for providing the protein in correct ratio for human consumption. There are various methods that rank quality of different types of protein. Some of the popular methods are Protein digestibility corrected amino acid score (PDCAAS) and Digestible indispensable amino acid score (DIAAS). Read more
Protein are complex nitrogenous organic compounds which are essential for physical and mental growth and development of body. They are defined as long chain polymer of α – amino acids bounded by peptide linkage. Therefore, protein are polypeptides of high molecular weight ranging from 5000 to many millions.
Food contamination: According to National Center for Biotechnology Information (NCBI) research, Food contamination is generally defined as foods that are spoiled or tainted because they either contain microorganisms, such as bacteria or parasites, or toxic substances that make them unfit for consumption. A food contaminant can be biological, chemical or physical in nature, with the former being more common. These contaminants have several routes throughout the supply chain (farm to fork) to enter and make a food product unfit for consumption.
How to protect food from contamination? Read more
Let us consider a column consisting of ideal plates. If we are somewhere at nth plate as shown in figure below, the plate immediately above the plate is n-1 and immediately below is n+1. Subscripts are used on all quantities showing the point of origin of the quantity. Read more
Boiling point diagram for ideal plate is shown in the figure below. The concentration of fluid entering and leaving the nth plate is shown in in the figure. By definition of ideal plate, vapor and liquid leaving the plate n are in equilibrium. So Xn and Yn represents equilibrium concentration.
Since concentration of both phase increase with height of column, Xn-1 is greater than Xn and Y1 is greater than Yn+1. Although the streams leaving the plates are in equilibrium, those entering are not.
When the vapor from plate n+1 and liquid from plate n-1 are brought into intimate contact their concentration tends to move towards an equilibrium state as shown by arrows in above figure.
Here, liquid streams are at their dew point. Heat necessary to vaporize component A is sullied from heat released in condensation of component B. Thus each plate act as an interchange apparatus in which component A is transferred to vapor stream and component B to liquid stream.
Since concentration of A in both liquid and vapor increases with column height, temperature decreases. Temperature of plate n is greater than that of plate n-1 and less than that of plate n+1.
Equilibrium concentration doesn’t necessarily means that reactants and products are present in equal amount. It means that reaction has reached a point where concentration of reactant and product are unchanging with time because forward and backward reaction have same rate.
About Author
Name : Pratiksha Shrestha
pratiksha.shrestha2001@gmail.com
Ms. Shrestha holds masters degree in food engineering and bioprocess technology from Asian Institute of Technology (AIT) Thailand. She is currently working for Government of Nepal at Department of Food Technology and Quality Control (DFTQC), Kathmandu. She is also a teaching faculty in College of Applied food and Dairy Technology (CAFODAT) affiliated to Purbanchal university, Nepal.
More than cleanliness, food hygiene is
It is the process of separation of components of comparable volatility. Production of vapor by boiling liquid mixture and condensing the vapor and allowing part of condensed liquid to still is the working principle of rectification.
In every distillation process, vapor formed in kettle is richer in more volatile component than in remaining liquid. However, the vapor contains certain amount of both components and distillate is rarely a pure substance. In order to increase concentration of volatile component in vapor and to separate the less volatile one, vapor is brought into contact with the stream of boiling liquid that runs down the column.
A stream of liquid with high concentration of volatile component is introduced at the top of the column. The most volatile components are concentrated in vapor phase and least volatile in liquid phase. This way vapor becomes richer in volatile component as it goes up the column, while liquid phase becomes richer in heavier component as it descends the column and separation is achieved.
Separation of mixtures depends upon relative volatilities of components, number of contact stages and reflux ratio. Rectification unit consist of
Typical diagram for rectifying column is shown as below.
In the above figure, feed is introduced into the column ‘A’ at the point that is nearly its center. The plate on which feed enters is called feed plate. All plates above the feed constitute rectifying section. The plates below the feed, including the plate itself constitute stripping section.
The feed flows down the stripping section to the bottom of the column in which definite level of liquid is maintained. Liquid flows by gravity to reboiler ‘B’. Reboiler generates steam (vapor) and returns it to the bottom of the column, which then passes up to entire column.
At one end of reboiler is a weir (dam) and downstream side of this weir collects bottom product which is withdrawn and passed through cooler ‘G’. This cooler also preheats the feed by heat exchange with the hot bottoms. The vapors rising through rectifying section are completely condensed in condenser ‘C’ and the condensate is collected in accumulator ‘D’.
Reflux pump ‘F’ takes liquid from accumulator and delivers it to the top plate of tower. This liquid stream is called ‘external reflux’.
Condensate not picked up by reflux pump is cooled in heat exchanger ‘E’ called product cooler and withdrawn as overhead product.
About Author
Name : Pratiksha Shrestha
pratiksha.shrestha2001@gmail.com
Ms. Shrestha holds masters degree in food engineering and bioprocess technology from Asian Institute of Technology (AIT) Thailand. She is currently working for Government of Nepal at Department of Food Technology and Quality Control (DFTQC), Kathmandu. She is also a teaching faculty in College of Applied food and Dairy Technology (CAFODAT) affiliated to Purbanchal university, Nepal.