Food analysis phenolic compounds

Knowledge of the identity of phenolic compounds in food facilitates the analysis and discussion of potential antioxidant effects. Thus studies of phenolic compounds as antioxidants in food should usually by accompanied by the identification and quantification of the phenols. Reversed-phase HPLC combined with UV-VIS or electrochemical detection is the most common method for quantification of individual flavonoids and phenolic acids in foods (Merken and Beecher, 2000 Mattila and Kumpulainen, 2002), whereas HPLC combined with mass spectrometry has been used for identification of phenolic compounds (Justesen et al, 1998). Normal-phase HPLC combined with mass spectrometry has been used to identify monomeric and dimeric proanthocyanidins (Lazarus et al, 1999). Flavonoids are usually quantified as aglycones by HPLC, and samples containing flavonoid glycosides are therefore hydrolysed before analysis (Nuutila et al, 2002). 

Paganga, G. et al.. The polyphenolic content of fruit and vegetables and their antioxidant activities what does a serving constitute Free Radical Res., 30, 153, 1999. Maatta, K.R. et al.. High-performance liquid chromatography (HPLC) analysis of phenolic compounds in berries with diode array and electrospray ionization mass spectrometric (MS) detection Rihes species, J. Agric. Food Chem., 51, 6736, 2003. 

Canini A, Alesiani D, D Arcangelo G and Tagliatesta P. 2007. Gas chromatography-mass spectrometry analysis of phenolic compounds from Carica papaya L. leaf. J Food Comp Anal 20 584-590. 

Im HW, Suh BS, Lee SU, Kozukue N, Ohnisi-Kameyama M, Levin CE and Friedman M. 2008. Analysis of phenolic compounds by high-performance liquid chromatography and liquid chromatography/mass spectrometry in potato plant flowers, leaves, stems, and tubers and in home-processed potatoes. J Agric Food Chem 56(9) 3341-3349. 

Tomas-Barberan FA, Gil MI, Cremin P, Waterhouse AL, Hess-Pierce B and Kader AA. 2001. HPLC-DAD-ESIMS analysis of phenolic compounds in nectarines, peaches, and plums. J Agric Food Chem. 49(10) 4748 t760. 

Aaby K, Hvattum E and Skrede G. 2004. Analysis of flavonoids and other phenolic compounds using high-performance liquid chromatography with coulometric array detection relationship to antioxidant activity. J Agric Food Chem 52(15) 4595 1603. 

Tomas-Lorente, F. et al.. Phenolic compounds analysis in the determination of fruit jam genuineness, J. Agric. Food Chem., 40, 1800, 1992. 

Tonnesen, H.H., Chemistry of curcumin and curcuminoids, in Phenolic Compounds in Foods and their Effects on Health. 1 Analysis, Occurrence and Chemistry, Ho, C.-T., Lee, C.Y., and Huang, M.-T., Eds., American Chemical Society, Washington, DC, 1992. 

Various excellent reviews are available on phenolic compounds, their chemistry and analysis, content in foods and nutritional significance (Bravo, 1998 Dykes and Rooney, 2006 Manach et al., 2004 Naczk and Shahidi, 2006 Robbins, 2003). From a nutritional perspective, phenolic compoimds (especially tannins) are regarded as antinutritional factors due to their ability to form complexes with dietary proteins and minerals and digestive enzymes (Bravo, 1998). However, lately there has been increasing focus on the positive aspects of phenolics due to their ability to act as antioxidants which may offer potential health benefits such as prevention of diseases such as cancer and cardiovascular disease. 

Stankevicius, M. Akuneca, L Jakobsone, L Maruska, A. Analysis of phenolic compounds and radical scavenging activities of spice plants extracts. Food Chemistry and Technology. 2010 44(2) 85-91. 

Stewart AJ, Mullen W, Crozier A. On-line high-performance liquid chromatography analysis of the antioxidant activity of phenolic compounds in green and black tea. Molecular Nutrition Food Research. 2005 49(1) 52-60. 

Many excellent discussions of natural occurrence, structure, characterization, and analysis of phenolic compounds are available in the literature, and a series of books devoted to flavonoid chemistry has also been published. Detailed discussions on various chromatographic modes, including HPLC, GC, column chromatography (CC), capillary electrophoresis (CE), PC, and TLC, of simple phenolics and polyphenols are also presented in the recent book, Handbook of Food Analysis, volume 1, edited by Nollet (1). Due to their diversity and the chemical complexity of phenolic compounds, this chapter is limited to phenolic compounds that are considered to be important to foods and the food industry. 

Phenolic compounds are of interest due to their potential contribution to the taste (astrin-gency, bitterness, and sourness) and formation of off-flavor in foods, including tea, coffee, and various fruit juices, during storage. Their influence on the appearance of food products, such as haze formation and discoloration associated with browning in apple and grape products, is also significant. Furthermore, analysis of these phenolic compounds can permit taxonomic classification of the source of foods. The importance of each phenolic compound and its association with the quality of various foods is described further in Sec. IV, on food applications. 

Reversed-phase chromatography is the most popular mode of analytical liquid chromatography for phenolic compounds. In most cases, the reported systems for the separation of phenolics and their glycosides in foods are carried out on reversed-phase chromatography on silica-based Cl8 bonded-phase columns. Occasionally, silica columns bonded with C8 were applied in the analysis of phenolic acid standards and coumarins (7), and C6 columns for the analysis of ferulic acid in wheat straw (8). 

HS Lee, BW Widmer. Phenolic compounds. In LML Nollet, ed. Handbook of Food Analysis. New York Marcel Dekker, 1996, pp 821-894. 

The first edition of Food Analysis by HPLC fulfilled a need because no other book was available on all major topics of food compounds for the food analyst or engineer. In this second edition, completely revised chapters on amino acids, peptides, proteins, lipids, carbohydrates, vitamins, organic acids, organic bases, toxins, additives, antibacterials, pesticide residues, brewery products, nitrosamines, and anions and cations contain the most recent information on sample cleanup, derivatization, separation, and detection. New chapters have been added on alcohols, phenolic compounds, pigments, and residues of growth promoters. 

Del Rio D, Stewart AJ, Mullen W, Burns J, Lean MEJ, Brighenti F, Crozier A. 2004. HPLC-MSn analysis of phenolic compounds and purine alkaloids in green and black tea. J Agric Food Chem 52 2807-2815. 

Wang M, Simon JE, Aviles IF, Hirshberg J, Olmedilla B, Sandmann G, Southon S, Stahl W. 2003b. Analysis of antioxidative phenolic compounds in artichoke (Cynara scolymus L.). J Agric Food Chem 51 601-608. 

Mertz, C. Cheynier, V. Brat, P. 2007. Analysis of phenolic compounds in two blackberry species (Rubus glaucus and Rubus adenotrichus) by high-performance liquid chromatography with diode array detection and electrospray ion trap mass spectrometry. J. Agric. Food Chem. 55 8616-8624. 

Garcia-Viguera, C., Bridle, P. (1995). Analysis of non-coloured phenolic compounds in red wines. A comparison of High-Performance Liquid Chromatography and Capillary Zone Electrophoresis. Food Chem., 54, 349-352. 

SBSE can be successfully used in the analysis of environmental samples [93-97] and for food analysis [98, 99]. PDMS is the most commonly used polymer, primarily because of its thermal stability and durability. SBSE has been modified by application of derivatization with different reagents (acetic anhydride, BSTFA, etc) [100-104]. This approach is suitable for the extraction of compounds requiring derivatization. The use of multistep derivatization with several extraction elements (each reaction is performed on a different stir bar) allows efficient extraction, desorption, and chromatographic analysis of compounds with different functional groups (e.g., phenols, steroids, amines, thiazoles, ketones). Acetic anhydride (ester formation), ethyl chloroformate (reaction of acids and amines), tetraethyloborane, and sodium bis-trimethylotrifluoroacetamide have been used for extraction and simultaneous derivatization [105]. 

The detection and identification of phenolic compounds, including phenolic acids, have also been simph-fied using mass spectrometry (MS) techniques on-hne, coupled to the HPLC equipment. The electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) interfaces dominate the analysis of phenohcs in herbs, fmits, vegetables, peels, seeds, and other plants. In some cases, HPLC, with different sensitivity detectors (UV, electrochemical, fluorescence), and HPLC-MS are simultaneously used for the identification and determination of phenolic acids in natural plants and related food products.In some papers, other spectroscopic instmmental techniques (IR, H NMR, and C NMR) have also been apphed for the identification of isolated phenolic compounds. 

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