Rapid Prediction of Moisture Content in Intact Green Coffee Beans Using Near Infrared Spectroscopy

Abstract

Moisture content (MC) is one of the most important quality parameters of green coffee beans. Therefore, its fast and reliable measurement is necessary. This study evaluated the feasibility of near infrared (NIR) spectroscopy and chemometrics for rapid and non-destructive prediction of MC in intact green coffee beans of both Coffea arabica (Arabica) and Coffea canephora (Robusta) species. Diffuse reflectance (log 1/R) spectra of intact beans were acquired using a bench top Fourier transform NIR instrument. MC was determined gravimetrically according to The International Organization for Standardization (ISO) 6673. Samples were split into subsets for calibration (n = 64) and independent validation (n = 44). A three-component partial least squares regression (PLSR) model using raw NIR spectra yielded a root mean square error of prediction (RMSEP) of 0.80% MC; a four component PLSR model using scatter corrected spectra yielded a RMSEP of 0.57% MC. A simplified PLS model using seven selected wavelengths (1155, 1212, 1340, 1409, 1724, 1908, and 2249 nm) yielded a similar accuracy (RMSEP: 0.77% MC) which opens the possibility of creating cheaper NIR instruments. In conclusion, NIR diffuse reflectance spectroscopy appears to be suitable for rapid and reliable MC prediction in intact green coffee; no separate model for Arabica and Robusta species is needed.

Simultaneous Determination of Some Biochemical Contents of Coffee Arabica (Coffea arabica L.) Varieties and Correlation with Organoleptic Cup Quality in Contrasting Altitudes in Southwest Ethiopia

“…High-altitude coffee varieties have exhibited the higher moisture contents, than the similar coffee varieties from mid-altitude and low altitude; this could be attributed to the presence of relatively high temperate and wind flow rate at mid altitude and low altitude. The moisture contents of all the studied coffee varieties were in the recommended safe range, i.e., below 12.50 %, for importing or exporting coffee beans Adnan, et al, (2017).Moisture content outside the safety range impairs the bean quality and safety. Beans with a moisture content above 12.5% are not allowed to be shipped and traded since it facilitates fungal growth and mycotoxin production (e.g., ochratoxin A) that are risks to human health Adnan, et al, (2017).…”

“…The moisture contents of all the studied coffee varieties were in the recommended safe range, i.e., below 12.50 %, for importing or exporting coffee beans Adnan, et al, (2017).Moisture content outside the safety range impairs the bean quality and safety. Beans with a moisture content above 12.5% are not allowed to be shipped and traded since it facilitates fungal growth and mycotoxin production (e.g., ochratoxin A) that are risks to human health Adnan, et al, (2017). On the other hand, moisture content below 8 % also causes shrunken beans and an unwanted appearance.…”

“…Most coffee importing and exporting countries consider the moisture content of green coffee beans as one of the quality parameters. According to Adnan, et al, (2017), the safety range for moisture content of coffee is 8.0-12.5%, based on the fresh matter. In this study, the moisture contents of coffee varieties, which were cultivated in different altitudes, were evaluated (Table 2).…”

“…The green coffee sample was dried in a dry an oven to a constant weight (100 beans), at 105 ºC for 24 hrs and each sample was cooled and the weight (g) was taken. According to Adnan, et al, (2017) the percentage of moisture content was calculated. The moisture content of the parchment coffee was measured by moisture tester maintain the moisture level from 10.5-11.0% (Sultan et al, 2014).…”

Rapid Determination of Saponins in the Honey-Fried Processing of Rhizoma Cimicifugae by Near Infrared Diffuse Reflectance Spectroscopy

“…It has the advantages of being simple and convenient to use, provides fast analysis, and causes no damage to samples, which is an environmentally-friendly, fast, and convenient non-invasive analysis technology [ 10 ]. For example, it is used to rapidly measure the moisture content of coffee beans [ 11 ], to measure the content of heavy metals in soil [ 12 ], and to determine copper and zinc contaminants in Ludwigia prostrata Roxb, etc. [ 13 ].…”