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The Chemical Detective
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Is apple juice made just from apples? It sounds like a simple question that has an easy answer. However, Dr. Nick Low of the Department of Applied Microbiology and Food Science at the University of Saskatchewan has found that it isn’t always to answer this question. In 1990, Low developed a technique involving High Performance Liquid Chromatography (HPLC) to detect trace oligosaccharides (carbohydrates) which are present when fruit beverages have been adulterated with less expensive materials. This test is now called the Low-1 Test.
Chromatography is essentially the separation of components from a mixture and often uses two phases, mobile and stationary. In HPLC, the stationary phase is a packed column and the mobile phase is a liquid; hence High Performance Liquid Chromatography. The separation occurs when the mixture is placed on the stationary phase and the mobile phase is allowed to pass over it. As the mobile phase moves, the components of the mixture that are more soluble in it move and elute off of the column. Thus, the components that have a higher affinity for the mobile phase will elute first. As a result, the components will be separated in a certain order. The order of the elution is characteristic for each mobile phase.
Fruit juices are made up of 95% carbohydrates. The major carbohydrates naturally present in these foods are glucose, fructose, and sucrose. Fruit juice adulteration occurs when less expensive carbohydrates such as those from sugar beet or sugar cane are used by unscrupulous manufacturers to supplement the natural fruit juice. In most cases the adulterant used resembles the major carbohydrate profile of the juice. For example, beet sugar is an ideal adulterant for orange juice while inulin (a fructose polymer) or high-fructose syrup from corn are better suited for apple juice.
Agriculture and Agri-Food Canada, the Food and Drug Administration (USA) and many other regulatory agencies worldwide now use the Low Test(s) for fruit juice authenticity determination. The first major impact of the Low-1 Test occurred in the United Kingdom in 1990 when Dr. Low revealed that there was a high level (~70)% of adulteration of commercial juices. Most of the adulteration was traced back to a company in Israel which had been producing 30% more orange juice than it had oranges!
A modified test (Low-2 Test) was used five years later when Low was on leave at the University of Reading, U.K., in 1995. This time the fruit juice shown to be adulterated was apple. It was found that hydrolyzed inulin was the adulterant which looks and tastes like apple juice. The adulteration was traced back two companies, one in Belgium and one in Holland. The two companies had been selling the adulterated product worldwide and significant quantities were sole to Europe and North America. As a result, every major apple juice seller including Coca-Cola (distributors of the Minute Maid brand) was found with adulterated product.
Since the development of Low-1 and Low-2 Tests, Dr. Low has become world-renowned as a chemical detective in cases of fruit beverage adulteration. Dr. Low is currently working with state-of-the-art equipment to develop authenticity tests that are more sophisticated and sensitive so as to make it more difficult for people to produce fraudulent foods.
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