How Pure Is Your Juice?

[deepali-mohindr]

During my teenage years when we would have 2.5 months off from school, I used to look forward to my travel adventures during the summer break.  Many times my family and I would go back to India to meet our relatives and stock up on things that were not available in the United States like exotic spices, colorful clothes and replicas of the Taj Mahal. One of my most enjoyable moments was going to the local fruit juice vendor -- who seemed to be located in every market -- and have a couple of glasses of fresh squeezed fruit juice. From orange and lemon juice to sugar cane and pomegranate juice, they could squeeze them all right in front of you. Those were the days when I didn’t care much about contamination or the un-hygienic conditions that might have been present. All I wanted was my pure, healthy, unadulterated, freshly squeezed pomegranate juice that was very hard to come by in Northern California.

These days we do have juice shops in Northern California malls and yes, they are clean as well.  But most of the population still goes to the local grocery store to purchase their favorite fruit or vegetable juice. Okay, we know it’s not freshly squeezed, but yes, we do expect the juice to be 100% pure as claimed by the nutritional label and not adulterated. But this is not always the case. According to the Grocery Manufacturers Association, in 2014 it was estimated that food fraud cost the global food industry between $10- $15 billion per year, affecting 10% of all commercially sold food products. And one of the top most adulterated products is juice. Juice adulteration presents an economic and regulatory problem. The most common forms of adulteration include simple dilution and blending of inexpensive and synthetically produced juices into the more expensive ones. The source of sweetener can be other juices or sugar derived from fruits or vegetables. Another type of fraud would be if the juice is labeled as 100% pure but contains artificial flavors.

There are a few ways to analytically determine food fraud in juices: by looking at the profiles of the carbohydrates, organic acids or anthocyanins or by looking at the isotope fingerprint. With the largest scientific portfolio, Thermo Fisher Scientific has the instruments and consumables that you need for all your juice authenticity needs.

Profiling of Carbohydrates

High-performance anion-exchange chromatography (HPAE) coupled with pulsed amperometric detection (PAD) is a well-established technique to identify and quantify carbohydrates in food and beverage samples. This technique is important for quality control, nutritional labeling, authenticity testing, and production process monitoring because it provides key metrics of product quality and related properties, contamination, or adulteration. HPAE-PAD allows direct quantification of

nonderivatized carbohydrates with minimal sample preparation and resolves most carbohydrates from sugar alcohols and organic acids, while not detecting sodium chloride commonly present in fruit juices.

See this application brief for more information: Determination of Carbohydrates in Fruit Juice Using Capillary High-Performance Anion-Exchange Chroma...

Profiling of Organic Acids

The determination of organic acids plays an important role when testing the authenticity of fruit juices.   Certain fruit juices, such as those obtained from pomegranates and various types of berries, are popular because of their high levels of antioxidants and the resulting putative health benefits. The high economic value and the large market demand for these juices make them a likely target for adulteration.

Many analytical methods are available to determine organic acids in juices. However, several organic acids have poor UV absorption and therefore lack sufficient sensitivity for detection. In addition, other components commonly present in these types of samples—such as sugars and phenolic compounds—have a much higher UV absorption, which can interfere with the detection of target analytes. In contrast, virtually all carboxylic acids ionize sufficiently; therefore, ion chromatography (IC) with suppressed conductivity detection is the technique of choice to separate a large variety of organic acids with inorganic anions and detect them with high sensitivity while minimizing the sugar interferences.

See this application note for more information: Determination of Organic Acids in Fruit Juices

Profiling of Anthocyanins

The anthocyanin profile is one of several chemical analyses that are required to determine the authenticity of pomegranate juice. Thermo Scientific has a sensitive, fast and accurate way to determine anthocyanins in commercially available fruit juices using a simple dilution and our Rapid Separation Liquid Chromatography system. Anthocyanins can be separated using a 2.2 μm, Acclaim® RSLC 120, C18 Rapid separation liquid chromatography column and detected at a visible wavelength of 540 nm. The silica-based column used for this solution is designed for rapid, high-resolution separations, which is compatible with ultrahigh pressure instrumentation. The six anthocyanins of interest can be separated in <5 min in pomegranate juices.

See this application note for more information: Fast Determination of Anthocyanins in Pomegranate Juice

Isotope Fingerprinting

Food and beverage products carry a unique chemical signature that relates to the biogeochemical processes that happened during the formation process of the materials that are present in the final product. These biogeochemical processes leave a chemical fingerprint that can be routinely detected in food and beverage products by measuring the stable isotope values of the products; this is what we call the isotope fingerprint of food and beverage products. These stable isotope values can be interpreted to provide conclusive information on the origin of a product, meaning you can identify where in the world or within a country a product has come from, and the authenticity of a product, which means understanding if a product has been changed from its raw composition to something else. By using isotope fingerprints to detect food and beverage fraud, laboratories can:

•  Trace food and beverage fraud with unique answers about origin and authenticity.


• Extend their analytical capabilities.


• Work with an integrated analytical solution, driven by a single software for automated high sample throughput.

See this poster note for more information: Food and beverage fraud prevention using stable isotope fingerprints

Testing for juice adulteration is important for consumer safety. Many people are allergic to particular fruits and vegetables as well as additives and rely on label claims when choosing their products.

Juice manufacturers need to make sure that the raw ingredients being added to a juice are pure and unadulterated. They need to test the raw materials as well as the final product and reflect the correct ingredients/information/claims in the nutritional label.