Notes

Jul 29

Working Principle of Atomic Absorption Spectroscopy (AAS)

Atomic absorption spectroscopy (AAS) determines the presence of metals in liquid samples. Metals include Fe, Cu, Al, Pb, Ca, Zn, Cd and many more. It also measures concentration of metals in the sample. Typical concentration range in the low mg/L. In their elemental form, metals will absorb ultraviolet light when they are excited by heat. Each metal has characteristic wavelength that will be absorbed. The AAS instrument looks for a particular metal by focusing a beam of ultraviolet (UV) light at a specific wavelength through a flame and eventually detected by a detector. Read more

Jul 28

Gas Chromatography

Gas chromatography (GC) is a method of chemical analysis for separating chemicals in a complex sample. This technique uses a flow through narrow tube known as column through which different chemical constituents of a sample in a gas stream (mobile phase; carrier gas) at different rates depending on their various chemical and physical properties and their interaction with a specific column filling called stationary phase. As the sample exit the end of column, they are detected and identified electronically. The function of stationary phase in column is to separate different components, causing each one to exit the column at different times (retention time). Other parameters that can be used to alter the order of time of retention are
1. Carrier flow rate
2. Temperature Read more

Jul 26

Single Cell Protein (SCP)

Fig: Single Cell protein (https://sites.google .com/ site/mehdidastgheib/scp2.jpg)

Microbial protein are commonly called single cell protein (SCP) referring to the fact that most of the microorganism used as protein producers are single cells or filamentous individual. SCP is a generic name which refers to dry cells or protein concentrates from microorganism obtained by growing in large amount in variety of abundant and inexpensive culture media and used as protein supplement for human and animal. SCP should not be confused with biomass (ex; mushroom) and microbial biomass. SCP can be produced using different species of bacteria, yeast or fungi.

Read more

Jul 25

Physiochemical changes during ripening of fruits and vegetables

A fruit can be said to be physiologically mature when it has reached its last slow stage of growth and has developed the ability to ripe normally after harvest. It may be commercially mature in an earlier stage when sufficient desirable characteristic have been developed to make it edible. Commercial maturity is the time of harvest related to end used of market requirement. It may be any stage between development and senescence (quality degradation of ripen fruit). Physiological maturity is particular stage of plant. It is the maximum developed stage of fruits and vegetables.
During the development of growth period of fruit, there are many chemical and physical changes taking place in them. Read more

Jul 23

Non Thermal Preservation of Food-Pulsed Electric Field

In this method of food preservation, electric energy at low power is collected over an extended period and stored in capacitor. That same energy is discharged, almost instantaneously at high level of power. When exposed to electric field, plasma membrane of cell becomes permeable to small molecules and the permeation causes swelling and eventual rupture of cell membrane. Rupture of cell membrane depends on factors such as intensity of electric field, number of pulses and duration of pulses. The induced transmembrane potential larger than natural potential of cell membrane cause rupture of cell membrane. Generation of pulse electric requires two devices; a) Pulse power supply and b) Treatment chamber. Read more