A) from food and non-essential amino acids, which can

A) Research background (Introduction and problem statement)

                     Proteins are necessary for the vital activity of all cells of any organism. The surface complex of the cell, all its internal structures are constructed with the participation of protein molecules. Of all organic substances, they constitute the largest mass in the cell (50-70 Nutritional proteins that differ from endogenous proteins must consist of the amino acids on which they break up. This task is performed with the help of enzymes in the intestine. From here, they will be collected. Chains of more than 100 amino acids are formed, which assume different tasks depending on the sequence and location. The exact number of different proteins present in the body does not exist. Only an estimate that starts from about 50,000 proteins. Distinguish for essential amino acids, which are taken exclusively from food and non-essential amino acids, which can be produced by the body.

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The tasks of proteins are as varied as they are. they are responsible for the structure of the body and the development of each cell, and, therefore, enable the contractions of the muscles from which the movement is generated. As enzymes, they provide the functioning of chemical processes in the body. The concentration of ions is regulated by them. Protein transport gland and hemoglobin in the blood act as hormones and antibodies.

Proteins are small universals that are taken with a varied and healthy diet in sufficient quantity. They can be found in meat, fish, dairy products, cereals, fruits and vegetables. Nutrition experts advise you to rely mainly on plant protein sources, since they do not contain cholesterol. The daily requirement is about 0.8 to one gram of protein per kilogram of body weight. That’s roughly starting with a normal weight, depending on the age and sex between 44 and 60 grams per day. If too little protein is consumed, serious shortcomings appear that are evident in hair loss, lack of mood, impaired growth in children, muscle weakness and, in extreme cases, swelling. If you do not provide the body with protein in time, then you can die. That’s why knowing the total concentration, type or functional properties of food are important.

In order to determine protein in food, scientists have created many methods through the history. First, looking at the Kjeldahl method which is based on determining how much nitrogen content is in food since protein contents of food are mostly determined by the basis of total nitrogen content. Kjedal’s method is a time-consuming, therefore in modern laboratory practice the method is often attempted to replace with alternative methods of protein determination. But the Kjeldahl method, despite its complexity, is still the only generally accepted arbitration method for protein determination, and is most often used as a reference for calibration and adjustment of other analysis techniques. For this reason, apparatus for the determination of protein by the Kjeldahl method is available in almost every laboratory for the analysis of food products.

The classical method of Kjeldahl provides three simple steps: decomposition, distillation and titration. After titration, the amount of titrant used corresponds to the concentration of nitrogen that was present in the sample. The recalculation of the protein takes place using the recalculation factor F (6.25 = 0.16 g nitrogen per 1 g protein). The total time of analysis of one sample is about 2 hours. The method is quite sensitive, the limit of determination is 0.1 mg of nitrogen.

Heaters, flasks, glass coolers – when the method was only opened, everything was done exclusively in manual mode. Today, all three stages – decomposition, distillation and titration – can be easily accomplished with the help of automatic systems for protein analysis according to Kjeldahl:

A mineralizer for decomposition of the sample.

Distiller for distilling ammonia.

Scrubber for neutralization of gases.

Next method is called Biuret method. When the copper (Cu 2+) ions interact with peptide bonds under alkaline conditions, the product gives an intense violet-purple color. Biuret reagent, in the finished form can be purchased as a ready reagent in specialized stores. It is mixed with a protein solution, and then held for 15-30 minutes and the absorbance is determined at 540 nm. The main advantage of this method is that it does not interfere with other compounds that absorb at lower wavelengths, and the technique itself is less sensitive to the type of protein, because it uses absorption with peptide bonds that are common to all proteins, rather than to its individual groups. However, the method has a relatively low sensitivity compared to other UV methods.

Problem statements:

Which method should be used to determine plant protein concentration better in vegetable sample?

Which method is the most easy and convenient to use and has more advantages?


1) To determine the method with better accuracy to find the protein concentration in vegetable sample

2) To determine the most advantageous method to find plant protein concentration


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