Food, substance consisting essentially of protein, carbohydrate, fat, and other nutrients used in the body of an organism to sustain growth and vital processes and to furnish energy. The absorption and utilisation of food by the body is fundamental to nutrition and is facilitated by digestion. Protein, highly complex substance that is present in all living organisms. Proteins are of great nutritional value and are directly involved in the chemical processes essential for life.
Proteins are species-specific; that is, the proteins of one species differ from those of another species. A protein molecule is very large compared with molecules of sugar or salt and consists of many amino acids joined together to form long chains, much as beads are arranged on a string. There are about 20 different amino acids that occur naturally in proteins. Proteins of similar function have similar amino acid composition and sequence. Although it is not yet possible to explain all of the functions of a protein from its amino acid sequence, established correlations between structure and function can be attributed to the properties of the amino acids that compose proteins.
Measurement of protein concentration in solution has since long been of essential importance in biological laboratories. The most commonly used ways to determine protein concentrations are the Bradford, Lowry and BCA methods. These methods, however, have definite limitations speaking of sensitivity, dynamic range and - in the case of the Bradford and Lowry assay - compatibility with reducing agents.
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There is a relationship between concentration and absorbance. This relationship is expressed by the Lambert-Beer law, which is more commonly known as Beer's law. This law states that the absorbance of a light absorbing material is proportional to its concentration in solution.
Thus a spectrophotometer is used which is an instrument that measures the amount of photons (the intensity of light) absorbed after it passes through sample solution. With the spectrophotometer, the amount of a known chemical substance (concentrations) can also be determined by measuring the intensity of light/optical density detected.
Two different yogurts were used : a regular one and Skyr. One of the biggest benefits of skyr is its protein content. Producing skyr requires three to four times as much milk as making yogurt, resulting in a more nutrient-dense, high-protein product. In fact, eating high-protein dairy foods like yogurt has been shown to help prevent weight gain and obesity.
The Bradford protein assay is used to measure the concentration of total protein in a sample. The principle of this assay is that the binding of protein molecules to Coomassie dye under acidic conditions results in a colour change from brown to blue (absorbing at 595nm). This method actually measures the presence of the basic amino acid residues, arginine, lysine and histidine, which contributes to formation of the protein-dye complex. The concentration of protein thus is indicated by the change of absorbance by the absorbance of the quantity of bound dye.
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