Year: 2020

Jun 18

Modification of Fats and Oil: Hydrogenation

Hydrogenation of vegetable oil refers to conversion of unsaturated liquid oil into saturated or partially saturated plastic fat by catalytic addition of hydrogen. Most widely used catalyst is nickel. The main purpose of hydrogenation of vegetable oil is

  1. To modify oil for application in wide range of food uses such as production of margarine, deep frying oil, shortening in biscuit etc.
  2. To extend shelf life of fat by improving oxidative stability by reducing unsaturation. Unsaturated fats and oils are very susceptible to spoilage called rancidity.

For successful hydrogenation, crude oil impurities like phosphorous and sulfur compounds, free fatty acids, and residual soap need to be removed before proceeding for hydrogenation. These impurities have poisoning effect on catalyst and reduce its activity. Canola and rapeseed oil are particularly notorious for high level of natural sulfur which can cause problem in hydrogenation. Read more

Jun 16

Modification of Fats and oil: Fractionation

Different functionalities (nutritional and physical) require specific compositions that are usually not found in a single natural fat or oil. For this reason, fats and oil are often modified in order to achieve these desired compositions and thus physical and nutritional properties. For example; melting behavior, solid fat content are important factors in formulation of shortening and margarine while decreasing poly unsaturated fatty acids (PUFAS) to increase oxidative stability is important in frying oil. Following are the commonly used methods used to modify fats and oil Read more

Jun 15

Protein Quality, Sources and Dificiency

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

Jun 14

Protein and Amino-Acids

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.

 

 

 

 

 

 

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Jun 13

Food Contamination and Food Poisoning

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

Jun 12

Boiling Point Diagram for Ideal Plate

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.