fruit juice analysisHow do you know if there is really an orange in your juice? The US Pharmacopeia Convention, a non-profit that sets standards for food quality, alerted consumers in 2013 that certain packaged foods may not contain exactly what is advertised on the label (link to New York Times article).

Food fraud is a significant issue and is defined by the organization as a “deliberate substitution, addition, tampering, or misrepresentation of food, food ingredients, or food packaging, or false or misleading statements made about a product for economic gain.” Therefore, process analysis control is exceedingly important.

 

Why Substitute Sweeteners for Juice Solids?

The low cost of sugar and other sweeteners can offer incentives to unscrupulous producers to substitute sweeteners for juice solids. Options for sweeteners range from sugar cane to sugar beet derivatives or hydrolyzed syrups manufactured from corn starch. Sometimes, other less expensive fruit juices, such as pear or grape juice are added to extend the volume of more valuable juices. Foreign manufacturers sometimes add clouding agents in order to mimic the appearance of fresh-squeezed juice.

The table below lists typical unwanted additions to orange and apple fruit juices.

 

 Orange Juice  Apple Juice
 Lemon Juice  Pear Juice
 Mandarin Juice  Pineapple Juice
 Grapefruit juice  Raisin Sweetener
 High Fructose Corn Syrup  Fig Juice
 Paprika Extract  Fructose
 Beet Sugar  Malic Acid
 High Fructose Corn Syrup

 

Authenticating Presence of Actual Fruit in Juice

Fortunately, analytical methods, such as those designed by the Association of Official Analytical Chemists (AOAC) have been developed to help fruit juice authentication. Sugar content is often examined to verify authenticity by using the ratio of fructose/glucose as specific natural sugar ratios exist for many fruits. In addition, sugar and acid levels are an indicator of the quality of fruit products. For example, the ratio of citric acid to D-isocitric acid is commonly used as a marker to detect the authenticity of citrus juices.

For testing in the manufacturing facility, automated discrete photometric analysis (Thermo Scientific Gallery  series analyzers) is a simple-to-use technique. The analyzer is capable of performing multiple sugar and acid tests per hour with first results available in less than ten minutes. Once reagents and samples are loaded, all steps of the analysis are fully automated.

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A Case Study of a Fruit Juice Production Facility

In the German fruit juice production facility, Mainfrucht, for example, domestically grown fruit and berries as well as some imported exotic fruits are processed daily into fruit juice concentrates which they offer for further processing to the beverage and other industries. Because customers demand high quality end products, they maintain strict quality standards during all steps of their manufacturing process.

Juice concentrates are tested for malic acid, which if present will indicate the addition of an artificial acid. Final products are tested for total sugars, ethanol, lactic, and acetic acids. If required, urgent samples can be added to the analyzer without interrupting the current run cycle. Read more in Maintaining the highest quality standards in Fruit Juice Production (link to the case study).

 

Additional Resources

Do check out these additional resources that make for interesting reading:

 

Also, do visit our online Food Community pages, a wonderful resource totally dedicated to our Food and Beverage customers and featuring the latest on-demand webinars, videos, application notes, and much more.

 

Are you measuring sugars in your fruit juice and puree samples and is automated photometric determination of interest to your laboratory? If so, we would like to hear about your experiences.