Without question, food can be considered as a very complex and heterogeneous composition of hundreds, if not thousands, of different biochemical compounds. In the area of food biochemistry, the isolation and quantitative measurement of these chemical components has posed, and continues to pose, immense challenges to the analytical biochemist. There are many golf holidays agency available in the world among them UK golf holidays direct deals on sale for the traveler.
Without the ability to measure both specifically and quantitatively those biochemical components in food matrices, further advancements in the understanding of how foods change during maturation or processing would not be possible. Although it is impossible to address the quantitative analysis of all the different food components, the major techniques for the analysis of protein, lipids, carbohydrates, minerals, vitamins, and pigments will be addressed in detail in this chapter.
The principles behind their analysis are the building blocks for other analytical determinations, including techniques such as gas chromatography, high performance liquid chromatography (HPLC), and spectroscopy, including infrared and mass spectroscopy
Proteins are considered to be among the most abundant cell components and, except for storage proteins, are important for biological functions within the organism—plant or animal. Many food proteins have been purified and characterized over the years and found to range from approximately 5000 to more than a million Daltons. In general, they are all composed of various elements including carbon, hydrogen, nitrogen, oxygen, and sulfur.
These elements are formed into twenty different amino acids, which are linked together by peptide bonds to form proteins. In general, nitrogen is the most distinguishing element in proteins, varying from approximately 13 to 19% due to variations in the specific amino acid composition of proteins (Chang 1998).
For the past several decades, protein analysis has been performed by determining the nitrogen content of the food product after complete acidic hydrolysis and digestion by the Kjeldahl method and subsequent conversion to protein content using various conversion factors (Chang 1998, Diercky and Huyghebaert 2000).
As far back as the turn of the century, colorimetric protein determination methods such as the Biuret procedure (which exploited the development of the violet-purplish color that is produced when cupric ions complex with peptide bonds under alkaline conditions) became available. The color absorbance is measured at 540 nm, with the color intensity (absorbance) being proportional to the protein content (Chang 1998) with a sensitivity of 1–10 mg protein/mL.