Fruit adulteration

The introduction of synthetic materials into natural products, often described as adulteration , is a common occurrence in food processing. The types of compounds introduced, however, are often chiral in nature, e.g. the addition of terpenes into fruit juices. The degree to which a synthetic terpene has been added to a natural product may be subsequently determined if chiral quantitation of the target species is enabled, since synthetic terpenes are manufactured as racemates. Two-dimensional GC has a long history as the methodology of choice for this particular aspect of organic analysis (38). 

Figure 3.7 shows some early examples of this type of analysis (39), illustrating the GC determination of the stereoisomeric composition of lactones in (a) a fruit drink (where the ratio is racemic, and the lactone is added artificially) and (b) a yoghurt, where the non-racemic ratio indicates no adulteration. Technically, this separation was enabled on a short 10 m slightly polar primary column coupled to a chiral selective cyclodextrin secondary column. Both columns were independently temperature controlled and the transfer cut performed by using a Deans switch, with a backflush of the primary column following the heart-cut. 

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. 

Wrolstad, R.E. et al., Use of anthocyanin pigment analysis for detecting adulteration in fruit juices, in Methods to Detect Adulteration in Fruit Juice and Beverages, Vol. 

Color is often used as an indicator of food quality due to short evaluation times and cost savings. " People consider the colors of raw materials, half fabricates, and final products in order to make decisions to accept or reject food products. For example, levels of anthocyanins have been used to evaluate the adulteration of various pigmented food products, and fruit color is a strong determinant of ripeness. The role of the food handler in controlling the colors of food products is very important because such judgments are subjective. ... 

Herrmann, K. (1979). The possibUity of evidence of adulteration of fruit and vegetable products by means of the phenolic components. Lebensm. Gerichtl. Chem. 33,119-121. 

Carotenoids and their biosynthetic precursors can be used as biomarkers of fruit product quality and adulteration of one product with another, such as fraudulent mixing of apricot jams and spreads with pumpkin extracts (Kurz and others 2008), and for differentiation of various pumpkins and squashes (Azevedo-Meleiro and Rodriguez-Amaya 2007). 

It was concluded from the data that the method is suitable for the differentiation between fruits and may help the detection of adulteration [241],... 

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. 

The major adulteration problem in fruit products is addition of sugar. The simplest method of extending a fruit juice is to add inexpensive sugar and dilute with water to rebalance sweetness. Since most juices are extracted from C4 plants (813C 15%o), and adulterating sugars from corn syrup or cane sugar are from C3... 

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... 

Foods. The determination of antioxidants and food preservatives is a very active part of the gas chromatography field. Adaptations and sample types are almost limitless for example, analysis of fruit juices, wines, beers, syrups, cheeses, beverages, food aromas, oils, dairy products, decomposition products, contaminants, and adulterants. A detailed discussion of this field may be found in Chapter 9. 

Wrolstad, R.E., Hong, V., Boyles, M.J., and Durst, R.W. 1995. Use of anthocyanin pigment analysis for detecting adulteration in fruit juices. In Methods to Detect Adulteration in Fruit Juice and Beverages, Vol. I (S. Nagy and R.L. Wade, ed.). AgScience Inc., Auburndale, Fla. 

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. 

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. 

Nagy, S. and Wade, R.L. (eds.) 1995. Methods to Detect Adulteration of Fruit Juice Beverages, Vol. I. 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. 

For lemon juice, the flavonoid composition was characterized by HPLC with photodiode detection at 287 nm (108), the HPLC condition based on a procedure proposed by Kirksey et al. (103) for the detection of fruit juice adulteration. Hesperidin and eriocitrin were the characteristic flavonoids of lemon juice. Flavonoid content by HPLC was used to study the effects of processing and pulp removal on flavonoid composition in lemon juice. Eriocitrin is also used in distinguishing lemon juice from grapefruit and orange juices, which do not contain this flavonoid. 

The high demand for authentic vanilla extract as a flavoring agent has resulted in frequent attempts at adulteration. An HPLC method for the quantitation of coumarins as an adulterant in a variety of vanilla flavorings, using a 10-yu.m /xBondapak Cl8 column with MeOH-HzO (40 60, v/v) as the mobile phase, was proposed (156). Phenolic analysis could be used further for the detection of mixtures of fruits in jams (157). The phenolics present in different commercial jams of apricot, plum, peach, strawberry, sour orange, apple, and pear have been compared and the characteristic compounds for each different jam identified for potential use as marker compounds. 

A Versari, S Biesenbruch, D Barbanti, PJ Famell. Adulteration of fruit juices dihydrochalcones as quality markers for apple juice identification. Lebensm Wiss Technol 30 585 -589, 1997. 

Adulteration of Fruit Juice Beverages, edited by Steven Nagy, John A. Attaway, and Martha E. Rhodes... 

The adulteration of fruit juices is widespread. As with any commodity, juice manufacturers, blenders and users can secure considerable financial benefit from adulterating fruit juice. It should be emphasised that food safety issues are not normally an issue in fruit juice adulteration. The issue is simply the fact that traders and consumers are being defrauded an adulterated fruit juice sold as pure fruit juice is not as it has been labelled. 

The detection of adulteration and its quantification have spawned some elegant scientific techniques, some borrowed from other fields and some developed specifically for use in fruit juice work. 

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,... 

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. 

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