Abstract
The freshness of ground roasted coffee escapes extremely fast. For this reason, the evaluation of conservation state of ground roasted coffee must be taken into account for acceptability of coffee. Unfortunately, it is difficult to discriminate the fresh and expired ground roasted coffee physically by our naked eyes. Thus, it is desired to develop an analytical method to evaluate the fresh and expired ground roasted coffee using reliable methods. The objective of this research was to evaluate the potential of UV-visible spectroscopy and chemometrics method for classification of fresh and expired ground roasted robusta coffee. A number of 200 samples of robusta fresh coffee and 200 samples of robusta expired coffee was used. The spectral data were pre-treated using standard normal variate (SNV), moving average smoothing (window: 9) and Savitzky-Golay 2nd derivative (order: 2; window: 11). The analysis data was done statistically using multivariate chemometric techniques, including principal component analysis (PCA) and soft independent modeling of class analogy (SIMCA) in the spectral range of 230-400 nm. PCA with PC1 = 94% and PC2 = 4% showed clear clustering of samples (p ≤ 0.05). UV-visible spectroscopy with SIMCA analysis allowed to classify between fresh and expired ground roasted robusta coffee with a correct classification rate of 100%.
Highlights
Coffee is the second most widely consumed beverages after water
This research proposes a classification method based on UV-visible spectroscopy and principal component analysis (PCA) and soft independent modeling of class analogy (SIMCA), for identifying the conservation state of Robusta ground roasted coffee
The results from PCA unsupervised classification techniques shows the formation of clear separation between fresh and expired samples which indicates that fresh samples group differed notably from expired samples group
Summary
Coffee is the second most widely consumed beverages after water. It is approximately about 1.4 billion cups of coffee are consumed worldwide every day [1]. Indonesia shared 7.5% of 9.6 million tons total world coffee production in 2017 [2]. Lampung province is the second largest production for Robusta coffee in Indonesia. In 2016, total coffee production in Lampung (mostly Robusta coffee) is about 108 thousand tons [3]. It is about 17% of total national coffee production in Indonesia [3]. To keep the sustainability of coffee production in Indonesia, several attempts have been made to improve both production and postharvest aspects of coffee [4,5]
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