top of page

Detection of bissap calyces and bissap juices adulteration with sorghum leaves using NIR spectroscopy and VIS/NIR spectroscopy

Sobolo (Bissap) is a local beverage consumed in most parts of a west Africa. It is a refreshing drink made from the Bissap leaves. sobolo, is produced by extracting the anthocyanins in bissap (Hibiscus sabdariffa) calyces. The calyces of this herb reportedly contain minerals such as calcium, magnesium, iron and potassium (Adanlawo and Ajibade, 2006) and have antioxidant properties (Ologundudu et al., 2009).

It is a therapeutic beverage made by incorporating natural herbs and spices. For many people in Ghana, especially low-income earners and children, local drinks such as; ‘sobolo’ contribute significantly to the nutritionally-balanced meals and drinks (Dadson, 2020) they take within the day, and this is because it may be the least expensive and most accessible means of obtaining a healthy and nutritious drink outside their homes (FAO, 2009). In other words , a chilled bottle of sobolo the deep red, tangy-sweet hibiscus drink made from bissap calyces to the ordinary Ghanaian is more than just a refreshment. It’s tradition, health, and affordable nutrition in a bottle.

The red coloration of this drink, produced by the anthocyanins present in the leaves of of the Bissap leaves makes it attractive. However due to this characteristics, producers have been found to be adulterating this drink with Soghum leaves and dried avocado seeds to increase its colour. These acts undermining the quality and potential health benefits of the drinks.



A survey was conducted to determine the authenticity of these claims. The survey conducted across Kumasi’s markets, which included 44 vendors and consumers revealed a growing list of questionable additives: dried avocado seeds, artificial coloring, sawdust — and most commonly, sorghum leaves, which are usually reserved for making “waakye”, a dish made by cooking rice and beans.

Vendors admitted to using sorghum to increase volume and enhance the red color of sobolo, making the drink look more appealing while reducing cost. The problem? Sorghum leaves are nutritionally inferior to bissap and reduce the drink’s health benefits.


This study combined the use of Near Infrared Spectroscopy and other conventional techniques to classify and predict the type and level of adulterants in the samples. The Researchers tested bissap samples adulterated with varying amounts of sorghum (0, 5, 10, 20, 30, 40, 50 and 100 %) w/w in three forms: whole, cut, and powdered. They also prepared sobolo drinks using traditional recipes and ran them through physicochemical and sensory tests.

In terms of the physicochemical analysis, their findings revealed the following:

  •   Color changes were subtle—in some cases, sorghum made the drink even redder, fooling both consumers and visual inspections

  • .   Antioxidant levels dropped sharply as more sorghum was added.

  •   In blind taste tests, most participants could not detect low levels of adulteration by taste, smell, or color.

  •   Adulterated sobolo had a higher pH (was less acidic), suggesting a loss of freshness and flavor stability.


Using Chemometric techniques like Principal Component Analysis (PCA) and Linear Discriminant Analysis (LDA), the team could classify and predict whether a sample was pure or mixed even estimating how much sorghum was present. PCA showed no difference between adulterated and unadulterated samples based on forms and concentrations.

LDA showed a 100 % classification for all cut samples and some misclassifications for whole and powder samples for both NIR and VIS/NIR spectroscopy. Also, there were observable differences between adulterated and unadulterated juices produced from cut forms. PLSR models predicted different concentrations of adulterants present in both bissap calyces and juices. Bissap juices adulterated with sorghum leaves are not easily detectable and have reduced concentrations of some beneficial nutritional compounds present in sobolo.


NIR and VIS/NIR spectroscopy, combined with chemometric techniques such as PCA, LDA, and PLSR, as a rapid detection technique, showed good potential for sobolo authentication.


 

What This Means for Consumers and Regulators

While sobolo remains a beloved and culturally significant drink, this research raises a red flag about food fraud and public health risks. Adulterated drinks may not be immediately harmful, but they deprive consumers of the nutritional benefits they rely on, especially in low-income areas.

 

For Ghana Food and Drugs Authority and other stakeholders, this study offers a toolkit for market surveillance and enforcement. It could be a game-changer in regulating local beverages, ensuring consumer safety, and protecting public trust.


Final Sip: Be Aware, Not Alarmed

If you're buying sobolo from your favorite vendor, this doesn’t mean you should stop but it does mean we need better transparency and testing. With accessible technologies and responsible oversight, sobolo can remain the nutritious, safe, and delicious drink Ghanaians love.


Ask your question

  • Was this article educative?

  • Yes

  • No




Comentários


bottom of page