Adulteration, fruit product, detection

The protocols presented here allow one to analyze the anthocyanins in fruit juices, natural colorants, and extracts from various anthocyanin sources. These profiles are useful for the identification of species, varieties, and for quality assessment of commercial products. They are also used to detect misbranding or adulteration of fruit products with other anthocyanin containing fruits, juices, or colorants. 

Table 18.42. Phenolic compounds as indicator substances for the detection of adulteration of fruit products...

It must be guaranteed that the selected indicator substance is stable under the production conditions for the particular fruit product. Therefore, anthocyanins are generally not suitable. For fermented products, 0-glycosides are not suitable because they are degraded by yeast enzymes. Suitable compounds are C-glycosidicaUy bound flavonoids which are resistant to enzymatic hydrolysis and common chemical hydrolysis, e. g., schaftoside (cf. Table 18.42) can be detected even in wine and champagne when the must is adulterated with fig juice. 

Quantitative and qualitative anthocyanin composition must be known in order to determine the feasibility of application of new plant materials as anthocyanin-based colorant sources and to understand the relationships of structures and functions of anthocyanins. In addition, anthocyanin compositions of fruits and vegetables have also been used to detect adulteration of anthocyanin-based products - and as indicators of product quality. - ... 

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. 

Natural products such as wine, fruit juices, flavors, oils, and honey are prime targets for fraudulent adulteration because of their high prices. Sophisticated analytical methods (perhaps including isotope abundance measurements) are required to detect whether natural ingredients have been mixed with ones from cheaper synthetic sources. Isotope abundance is markedly different for natural vs. synthetic molecules and these differences can be exploited to detect adulteration. Several examples follow. 

Isotopic distribution within an element will vary between living organisms depending on the biosynthetic pathways that lead to its formation. Furthermore, the rate at which a molecule crosses cellular membranes will depend on the molecule s isotopic distribution. Hence, detectable differences in isotopic composition can be observed in the products formed. Detection of adulterated vegetable oils, flavourings and fruit juices, as well as the study of metabolism in plants and numerous biomedical applications, use isotopic abundance as a tool. For example, the... 

In the old days. chemists prided themselves on their ability to identify compounds by odor. Smelling unknown chemicals is a bad idea because some vapors are toxic. Chemists are developing electronic noses to recognize odors to assess the freshness of meat, to find out if fruit is internally bruised, and to detect adulteration of food products.13... 

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. 

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. 

PH Gamache, IN Acworth, ML Lynch, WR Matson. Coulometric array detection for HPLC in the analysis of juice products. In S Nagy, RL Wade, eds. Methods to Detect Adulteration of Fruit Juice Beverages. Auburndale, FL Agscience, 1995, pp 120-144. 

Fructose syrup. In addition to the glucose/fructose syrups mentioned above, a fructose syrup has been produced using inulin as a source. Inulin is the fructose analogue of starch, and the chicory root is the standard source for commercial hydrolysis. Fructose syrups are usually too expensive for routine use in beverage production but they have been employed where a particular claim is to be made for fructose. They have also been used for the adulteration of fruit juices as they are chemically difficult to detect. Detection is possible at the sub-molecular level by techniques such as stable isotope ratio measurement. Fructose is also manufactured using sucrose as a starting material. 

Over the past 30 years, extensive research has been carried out to find ways to detect the adulteration of fruit juices. The approaches have developed from simple procedures, such as measuring the potassium and nitrogen contents of juices, to the use of highly sophisticated and expensive equipment to detect the most recent approaches that unscrupulous suppliers may be using to extend their products. Such adulteration often involves the substitution of some of the fruit juice solids by sugars derived from beet, cane, com or inulin, or the addition of cheaper juices or second extracts of the fruit. 

Fingerprinting methods such as the anthocyanin methods and the Kirksey method for polyphenols (Kirksey el al., 1995) offer good ways to check for the addition of other fruits in a product. As the adulterators have become more sophisticated in the approaches that they use to extend juices, there has been a need for more complex methods of analysis. This means that it is now not uncommon to have to use fingerprinting techniques and isotopic methods to detect the most sophisticated forms of adulteration. These sophisticated analytical methods can even involve detection of the isotope ratios within a class of compounds such as sugars (Hammond el al., 1998). Using the RSSL 13C-IRIS approach, which was developed with financial support from the UK Food Standards Agency, it was possible to reduce the detection limit for the addition of C4-derived sugars to juices by about a factor of two. 

Fruit Juice concentrates vary widely in price because of differences in raw product cost and processing yield. For example, wholesale 1978 prices for Pacific Northwest produced concentrates varied from 6.25 per gallon for apple and pear to 35> T5, and 110 per gallon for strawberry, blackberry, and black raspberry concentrates, respectively (. ). The readily available, low priced concentrates are obvious potential adulterants for more expensive concentrates and methods are needed for their detection. 

Table II shows that sucrose levels are highest in peach fruit and very low in blackberry, cherry, and grape. The % C.V. for sucrose content for many of the fruit samples is extremely high, most likely because of enzymic or chemical hydrolysis. The average sucrose content of plum fruit is 38 of total sugars, while processed plums contain only 1. Presence of large quantities of sucrose in prune juice has, in fact, been used as an indication of adulteration ( ). Cherries and grapes contain invertase Cllj 12) which may account for sucrose not being detected in some samples and may also explain the high % C.V. for those fruits. In examining apple Juice concentrates, we did not detect sucrose in seven-fold concentrates whereas we did in fo ar-fold apple concentrates (7.) > the time-temperature conditions allowing for complete hydrolysis in the more concentrated product.

Phenolic compounds have sometimes been used to detect adulterations of fruit juices and jams. Most of them are flavonols, but some HCA derivatives can be used since they are typical of some fruit species such as tartaric derivatives in grape. For example, grape juice can be detected by the presence of caffeoyl-, / -coumaroyl-, and feruloyl-tartaric acids, whereas the presence of quinic esters of HCA would imply adulteration with other fruits. A method has also been developed for detection and quantitation of pulpwash, a lower-quality juice product, in orange juice [9] feruloyl and sinapoyl glucose, in addition to different other phenolic compounds, were present in much larger amounts in pulpwash. 

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