Vol. 24 No. 7 November 2013 articles 8 The use of near infrared spectroscopy as a tool to optimise the steeping process during malting of barley D. Cozzolino,* S. Roumeliotis and J. Eglinton School of Agriculture, Food and Wine, Faculty of Sciences, The University of Adelaide, Waite Campus, PMB 1, Glen Osmond, SA 5064, Australia. E-mail: d.cozzolino@adelaide.edu.au Introduction T he conversion of barley grain into malt is a complex process involv- ing germination of the grain under controlled conditions. 1–4 During mashing, ground malt is mixed with water and the enzymes present in the malt break down the ground tissue (mainly starch) to yield a liquid called wort, which provides the substrate upon which yeast grows during fermentation and ultimately results in beer production. 1 In this process, the uptake of water by the seeds is the critical and initial step to obtain optimal germination. For malting barley, this is represented by the first stage of the malting process, often referred to as steeping. 1–7 Steeping is the first operation of malting and its purpose is to increase the water content of the grain up to 43–46% w/w; however, such a simple step encompasses several different metabolic processes that affect both germination and the end- quality characteristics of the resulting malt. 2–7 Therefore, detailed knowledge of water uptake by the barley kernels is of importance to better understand the biochemistry as well as to optimise the malting process. 2–7 The initial hours of barley steeping are critical for enzymatic activation as well as for the development and release of hormones that will determine the final quality of the malt. 2,3,5–7 This process is also influenced by kernel morphology, endosperm chemical composition and structure (e.g. protein, starch, lipids, cell wall components), genetic background of the grain (e.g. variety) and environmental factors (e.g. temperature). 2–4,6,7 Overall, the measurement and monitoring of water uptake during steeping is an important quality control step during the malting process. Preliminary results on the use of near infrared (NIR) reflectance spectroscopy to monitor water uptake in barley during steeping are presented in this report. Experimental Twenty (n = 20) whole barley samples (Hor- deum vulgare L) sourced from commercial malting varieties (including Commander, Schooner, Gairdner, Admiral and Navigator) from two harvests (2010 and 2012) and two localities in South Australia (Roseworthy and Charlick) were studied in this work. Whole barley kernels (1.5 g ± 0.01 g) were placed (in triplicate) in a sample holder (40 x 32 x 5 mm) and soaked in a water bath (temperature 22°C). 5 Samples were removed at hourly inter- vals from 1 h to 8 h and again at 24 h. Before analysis, excess water was removed from the sample holder by shaking and from the grain surface using a filter paper. Water uptake was calculated by subtracting the initial weight of grains from the weight of the water absorbed by the grain. 5,6 Samples (grain size approx. 2.5–2.8 mm) were scanned (once) as whole grain (bulk, no selection of grain was made) using an integrating sphere in a Fourier trans- form (FT) multiple processor analyser (MPA) (Bruker Optics, Germany) spectrophotom- eter (12,500–3600 cm –1 ) using a cylindrical glass cell (20 mm diameter × 50 mm height) at 16 cm –1 spectral resolution. 5 Spectra were exported from OPUS software into The Unscrambler software (version X; Camo ASA, Oslo, Norway). Relationships between water uptake and NIR spectra as a function of the time and duration of steeping were evaluated using principal component analysis (PCA); PCA models were developed using full cross- validation. Before PCA analysis, the NIR data were transformed using the standard nor- mal variate (SNV) processing or the second derivative Savitzky–Golay (2 nd derivative, 40 smoothing points). Results Figure 1 shows the principal component score plot of whole barley samples analysed using NIR spectroscopy and collected at dif- ferent times during the steeping process. The first principal component explains 74% of the total variation in the NIR spectra of the barley samples, showing the main changes result- ing from water uptake by the grain from dry seed to the first hour of steeping. The arrows in the figure indicated the direction of these changes during the steeping process. Princi- pal component 2 explains 24% of the varia- tion and indicates the imbibition of water by doi: 10.1255/nirn.1395 Figure 1. Principal component score plot of barley grain samples from different times of steeping and analysed using NIR reflectance spectroscopy.