Authenticity of fruit juices

HPLC chromatograms with peak assignments are given for several commodities along with applications of anthocyanin analyses for determining authenticity of fruit juices. 

For fruits and their products, HPLC techniques for phenolics have been used to study the effect of processing, concentration, and storage on the phenolic composition of juices as well as a potential precursor for an off-flavor compound in juices. Phenolic analysis has been further applied to the detection of economic adulteration and especially to verify the authenticity of fruit juices. This is especially important when cheaper fruits can be added to more expensive ones in a fraudulent manner. In most fruits, the nonanthocyanin flavonoids consist mainly of flavonols and flavanols, with trace amounts of flavones. Glycosides are the predominant forms present. These most often are separated by reversed-phase HPLC on Cl8 columns with gradients consisting of acidified H20 and ACN, MeOH, or EtOH. 

Although there are only a limited number of methods that have been validated specifically for soft drinks, there are around 80 validated methods available for the analysis of fruit juices, most of which would work equally well for soft drinks. These methods are published in the International Fruit Juice Union (IFU) handbook of analytical procedures, which offers the best reference collection of methods for the analysis of fruit juices in the world, with new methods added on a regular basis (Anon, 2004a). The IFU s collection of analytical methods covers most of the main procedures required to assess the quality and authenticity of fruit juices and nectars. The methods are hsted on the IFU s website (http //www.ifu-fruitjuice.com) at the time of writing they cannot be purchased directly from there, but they can be obtained from the Swiss Fruit Union, Zug, and details of how to do this are given on the website. It is possible that at some time the methods will be made available directly from the website. 

Although it is beyond the scope of this chapter to discuss in any great detail methods used to assess the authenticity of fruit juices, a brief summary of this area is given at the end. In the fu st edition of this book, an introduction to HPLC was given to assist newcomer s to the field, but it is now felt unnecessary as this has become such a standard procedure. 

Another inediod of analysis that is used around Europe, and given below, was used by Hofsommer in the analysis of red and black juices as part of an EU-sponsored project in die early 1990s on methods to determine the authenticity of fruit juices (Hofsommer, 1994a). This method has been codaboratively tested by die IFU analytical commission and was found to give acceptable results (Anon, 1998b). The procedure does not involve any sample cleanup for juices the product... 

Establishing Criteria for Determining the Authenticity of Fruit Juice Concentrates... 

Coppola, E., English, N., Provost, J., Smith, A., and Speroni, J. 1995. Authenticity of cranberry products including non-domestic varieties. In Methods to Detect Adulteration of Fruit Juice Beverages, Vol. 1 (S. Nagy and R.L. Wade, eds.) pp. 287-309. AgScience, Aubumdale, Fla. 

ST Kirksey, Jr, JO Schwartz, JA Hutfilz, MA Gudat, RL Wade. HPLC analysis of polyphenolic compounds for juice authenticity. In S Nagy, RL Wade, eds. Methods to Detect Adulteration of Fruit Juice Beverages. Auburndale, FL Agscience, 1995, pp 145-166. 

The analytical detection and measurement of fruit juice adulterants is a rapidly developing field and the interested reader is directed to works dealing specifically with the subject, such as Food Authentication (Ashurst Dennis,... 

Although AIJN and RSK-value guidelines are of great use in the evaluation of fruit juices, there is always the risk of fraud. Today, more sophisticated techniques involving the analysis of stable isotope ratios of the sugars present in juices are a more reliable means of assessing authenticity. 

In the analysis of fruit juices, it is important to determine the levels of the individual acids to assess authenticity and quality. A range of these acids can be determined using an enzyme-linked assays and these procedures have been collaboratively tested and published in the IFU compendium of methods (citric no. 22, isocitric no. 54, D-malic no. 64, L-malic no. 21 and D-and L-lactic acids no. 53). r-Biopharm now distributes the Boehringer Mannheim kits to assess the levels of these acids. Similar kits are available from other suppliers. 

Fry, J., Martin, G.G. and Lees, M. (1995) Authentication of orange juice, in Production and Packaging of Non-carbonated Fruit Juices and Fruit Beverages, 2nd edn (ed. RR. Ashurst), Blackie Academic Professional, Chapman Hall, London. 

Hammond, D.A. (1996) Methods to detect the adulteration of fruit juice and purees, in Food Authenticity (eds RR. Ashurst and M J. Dennis), Blackie Academic Professional, Chapman Hall, London. 

Governments throughout the world advocate the inclusion of fruit juices in a healthy diet. A juice that is 100% derived from its parent fruit or fruits is almost universally regarded as a healthy and nutritious part of a human diet. The main emphasis in health-promoting dietary recommendations is increased consumption of fruit and vegetables. According to the CODEX General Standard for Fruit Juices and Nectars, an authentic fruit juice product... 

To detect adulteration of wine. Bums et al. (2002) found that the ratios of acetylated to p-coumaroylated conjugates of nine characteristic anthocyanins served as useful parameters to determine grape cultivars for a type of wine. Our laboratory utilized mid-infrared spectroscopy combined with multivariate analysis to provide spectral signature profiles that allowed the chemically based classification of antho-cyanin-containing fruits juices and produced distinctive and reproducible chemical fingerprints, making it possible to discriminate different juices. " This new application of ATR-FTIR to detect adulteration in anthocyanin-containing juices and foods may be an effective and efficient method for manufacturers to assure product quality and authenticity. 

Wrolstad, R.E. and Durst, R.W., Use of anthocyanin and polyphenohe analyses in authenticating fruit juices, in Proceedings of Food Authenticity Workshop, ENl Laboratories, Ed., Eurofins Scientific International Group, Montreal, 1998. 

Anthocyanins are water-soluble pigments which impart the red, purple, and blue coloration of many fruits, vegetables, and cereal grains. Their analysis is useful for commodity identification since the anthocyanin fingerprint pattern is distinctive for different commodities. The authors laboratory has demonstrated how HPLC anthocyanin analyses can be effectively applied to determine the authenticity of various anthocyanin containing fruit juices (Wrolstad et al., 1994). 

Fruit juices, whether of natural strength or concentrated, are materials of commerce, to be sold direct or for use in a variety of food and drink applications. It is essential that they conform to legislative requirements for authenticity and purity, whether for labelling purposes (in avoidance of misleading statements), nutritional standards or in respect of food safety in the final product. 

This has always been an objective of fair trade, but the temptation to enhance profitability too frequently intervenes and it is necessary for the buyer at times to carry out testing to ensure the authenticity of a purchased raw material so that the declaration subsequently given can meet the requirements of labelling. Fruit juices have often, over the years, been subjected to sophistry. As analytical techniques have become more objective and accurate in discovering fraud,... 

Fruit juice companies can themselves do a lot of the testing required to assess whether a product is authentic. However, they may not have the expertise necessary to assess the fine detail and an analyst without sufficient breadth of knowledge in this field might miss some subtle deviations in the data for a sample that would be detected by an expert. 

Hofsommer, H.J. (1994a) Analysis of anthocyanins in fruit juices. Paper presented as part of the SGF symposium Progress in the Authenticity-Assurance for Fruit Juices, Parma, Italy, September 1994. 

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