Wednesday, May 27, 2009

Adulteration of Fruit Juice

Adulteration of Fruit Juice
The adulteration of fruit juice is widespread. As with any commodity, juice manufacturers, blenders and users can secure considerable financial benefit from adulterating fruit juice.

It should be emphasized 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: and adulterated fruit juice sold as pure fruit juice is not as it has been labeled.

Although is becoming is becoming increasingly sophisticated, it is normally seen as falling into one of the three types;
1. Overdilution of juices with water
2. Use of cheaper solid ingredients (particularly sugars)
3. Blending of cheaper with more expensive juices

The issue of too much water being added to juices has largely been addressed through the application of a minimum solids content (measured in degrees Brix).

The second category of adulteration is by far the most common. For example, apple juice will normally contain around 11% by weight of solids.

At least 90% of these solids are carbohydrate – sucrose, dextrose and fructose predominating.

Considerably cheaper sources of carbohydrates in roughly the same proportion as those found naturally in apple juice can be used to ‘stretch’ apple juice by a considerable proportion.

In more sophisticated forms of adulteration the added components can be made to carry a similar ‘signature’ to the juice.

In the third category a cheaper juice can be used to adulterate a more expensive one; for example, elderberry juice can be used to extend strawberry or raspberry juice.

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

Direction of overdilution and the presence of sugars of origins is now carried out largely by measuring key isotope rations (such as carbon 13:12 ratios deuterium: hydrogen rations and oxygen 18:16 ratios) and comparing them with both those found naturally in fruit and agreed international standards.

Another elegant method of detecting sugar addition in particular has been the use of high performance liquid chromatography (HPLC) to determine the presence of oligosaccharides that are characteristics of the added sugars but not the fruit.

The use of enzymatic methods for determining the presence of specific components (e.g., D-malic acid, which does not occur naturally) is also helpful.
Adulteration of Fruit Juice
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