Quality Control in the Sugarcane Liquor Industry with FT-NIR Spectroscopy

Sugarcane was discovered in India between the 6th and 4th centuries BC by Persians. Today, sugarcane is the world’s largest crop by production quantity. It is cultivated in more than 90 countries with Brazil, India and China as the top three producers. For centuries, sugarcane has been cultivated to produce sugar. Then its cultivation was expanded to produce liquors, and with today’s technology, use of sugarcane is expanding into an extraordinarily diverse range of value-added products such as ethanol, bioelectricity and bioplastics.

There are five major types of sugarcane alcohols: rum, cachaça, rhum agricole, aguardiente, and basi. While rum is made from molasses, a byproduct of sugar production, the rest are made from sugarcane juice. Cachaça is made in Brazil from fermented and distilled fresh sugar cane juice. Rhum agricole is made in Caribbean countries, from fresh sugarcane juice, which is fermented then distilled and aged. Aguardiente is made in Ecuador, Colombia, and other Andean countries. Basi, made in the Philippines and Guyana, is lightly fermented.

To ensure quality and improve productivity, quality control tests are required for every stage of sugarcane liquor production: e.g. test pol and Brix for molasses; test pol, Brix, sucrose and reducing sugars for sugarcane juice; and test ethanol content for final liquor products. Traditional analytical methods used in the sugarcane liquor industry are comparatively expensive, time-consuming, and usually require varied methods to be used for different parameters. On the other hand, near-infrared (NIR) spectroscopy has the advantages of being nondestructive, rapid, and allowing for simultaneous measurements of multiple components. Furthermore, with a calibrated instrument, the end user needs no special skill or spectroscopy knowledge to run the test. 

FT-NIR Spectroscopy for the Sugarcane Liquor Industry

Molasses

Molasses is a byproduct of the sugarcane milling process and is usually very sticky and dark brown in color. As shown below, it can be measured in transflectance mode. The molasses sample is placed in the disposable glass vial with a reflector, that has a fixed gap in order to have a fixed optical path length of measurement. Then the vial is placed on top of the integrating sphere sampling window for transflectance measurement.

Figure 1. Molasses sample in glass vial with inserted transflector analyzed with QuasIR™ 4000 integrating sphere.

Parameters such as Pol, Brix, dry matter, sucrose, and reducing sugars can be analyzed by FT-NIR simultaneously.

Figure 2. Molasses Brix cross-validation result (R²=92.20, RNSECV=0.33).

Sugarcane Juice

Sugarcane juice can be placed in an 8 mm disposable glass vial and analyzed in transmission at room temperature (Figure 3).

Figure 3. Sugarcane juice in glass vial analyzed with QuasIR™ 4000 sample compartment.

Parameters such as Pol, Brix, sucrose, and reducing sugars can be analyzed by FT-NIR within seconds.

Figure 4. Sugarcane juice sucrose cross-validation result (R²=95.08, RNSECV=0.32).

Liquor Products

The ethanol content of final liquor products can be accurately measured with FT-NIR. No sample preparation is needed. Liquor can be transferred into an 8 mm glass vial and measured in transmission. Within seconds, the ethanol measurement can be obtained.

Figure 5. Rum ethanol proof cross-validation result (R²=99.98, RNSECV=0.22).

Conclusion

FT-NIR provides a rapid, nondestructive method for analyzing sugarcane for liquor and other sugarcane-based products. Instantaneous results that are comparable to traditional lab methods can be obtained across a wide range of parameters. Contact Galaxy Scientific’s experienced applications support team for more information.

This information has been sourced, reviewed and adapted from materials provided by Galaxy Scientific Inc.

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