Hyperspectral Imaging as a Rapid Quality Control Method for Herbal Tea Blends

Majolie Djokam,Weiyang Chen,Alvaro Viljoen,Ilze Vermaak,Maxleene Sandasi

doi:10.3390/app7030268

Majolie Djokam, Weiyang Chen + Show 3 more

Open Access

https://doi.org/10.3390/app7030268

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Abstract

In South Africa, indigenous herbal teas are enjoyed due to their distinct taste and aroma. The acclaimed health benefits of herbal teas include the management of chronic diseases such as hypertension and diabetes. Quality control of herbal teas has become important due to the availability of different brands of varying quality and the production of tea blends. The potential of hyperspectral imaging as a rapid quality control method for herbal tea blends from rooibos (Aspalathus linearis), honeybush (Cyclopia intermedia), buchu (Agathosma Betulina) and cancerbush (Sutherlandia frutescens) was investigated. Hyperspectral images of raw materials and intact tea bags were acquired using a sisuChema shortwave infrared (SWIR) hyperspectral pushbroom imaging system (920–2514 nm). Principal component analysis (PCA) plots showed clear discrimination between raw materials. Partial least squares discriminant analysis (PLS-DA) models correctly predicted the raw material constituents of each blend and accurately determined the relative proportions. The results were corroborated independently using ultra-high performance liquid chromatography coupled to mass spectrometry (UHPLC-MS). This study demonstrated the application of hyperspectral imaging coupled with chemometric modelling as a reliable, rapid and non-destructive quality control method for authenticating herbal tea blends and to determine relative proportions in a tea bag.

Highlights

The use of fresh and dried herbs for the preparation of herbal infusions that are popularly consumed for the pleasant taste and most importantly their perceived health benefits, dates back to antiquity
Principal component analysis of the image was performed and the results obtained are displayed in the score image (Figure 1b) and the scatter plot (Figure 1c) constructed after image cleaning, mean centering and standard normal variate (SNV) correction of the data
The variation modelled along principal component 2 (PC2) was 23.1% which explained the chemical variation between the two clusters while the 10.8% chemical variation observed along principal component 3 (PC3) might account for compositional differences within each tea/species

Summary

Introduction

The use of fresh and dried herbs for the preparation of herbal infusions (tisanes) that are popularly consumed for the pleasant taste and most importantly their perceived health benefits, dates back to antiquity. Tea is the most consumed beverage worldwide, second only to water. In 2013, the total retail sales of bagged, loose and concentrated teas in the United States increased by 5.9% reaching a figure of USD$1,751,055,302. In 2012, the total consumption of tea was shown to comprise of 85%. The 2013 statistics for bagged, loose and concentrated tea annual sales reported sales of USD$579,974,381 for black tea (bags), an increase from 2012 of 2.5%. The sales of herbal beverage tea (bags), medicinal teas (bags) and African red tea (bags) increased by 11.0%, 15.4% and 3.5%, respectively. A trend towards the increased consumption of loose tea was noted, especially in specialty tea and coffee shops.

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