S. Roumeliotis

Prediction of starch pasting properties in barley flour using ATR-MIR spectroscopy

The objective of this study was to evaluate the feasibility of using attenuated total reflectance (ATR) mid infrared (MIR) spectroscopy to predict starch pasting properties in barley flour samples. A total of 180 barley flour samples sourced from the University of Adelaide germplasm collection, harvested over three seasons (2009, 2010 and 2011) were analysed using both ATR-MIR and the rapid visco analyser (RVA) techniques. Calibrations (n=100) were developed using partial least squares (PLS1) regression and full cross validation. The coefficient of determination (R(2)) and the standard error in cross validation (SECV) were 0.74 (SECV=875 RVU) for peak viscosity (PV), 0.63 (SECV=561 RVU) for trough (THR), 0.80 (SECV=173 RVU) for breakdown (BRK), 0.74 (SECV=126 RVU) for setback (STB), 0.77 (SECV=679 RVU) for final viscosity (FV), and 0.73 (SECV=0.57 s) for time to peak (TTP). The RPD values (SD/SEP) from the validation indicated that only BRK can be accurately predicted (RPD=4). We have demonstrated that ATR-MIR spectroscopy has the potential to significantly reduce analytical time and cost during the analysis of barley flour for starch pasting properties.

Feasibility study on the use of attenuated total reflectance MIR spectroscopy to measure the fructan content in barley

The aim of this study was to evaluate the feasibility of using attenuated total reflectance mid-infrared (ATR-MIR) spectroscopy to predict the fructan content in both barley and malt flour samples. Samples (n = 60) were sourced from commercial and experimental barley grain varieties and their corresponding malts. The fructan content in grain and malt flour was determined using the enzymatic kit from Megazyme (K-FRUC, Megazyme International Ireland). Samples were scanned in a MIR instrument using an ATR single bounce cell (Bruker Optics, Germany). The coefficients of determination in cross-validation (R2) and the standard error of cross-validation (SECV) obtained for the prediction of the fructan content in the calibration set were 0.76 and 0.20%, respectively. The residual predictive deviation (RPD = SD/SECV) value obtained was 2.3, indicating that these calibrations can be used for qualitative determination of the fructan content (e.g. low, medium and high) in the set of samples analysed. This study showed that ATR-MIR spectroscopy might be used as approximate estimates of the true fructan concentration in barley and malt in order to rank samples (low, medium, high) in the context of a breeding program.

Relationships Between Fatty Acid Contents of Barley Grain, Malt, and Wort with Malt Quality Measurements

Although lipids and fatty acids (FA) represent only 1-3% of the grain weight, they can play an important role in regulating, modulating, and determining several chemical and physical properties of the grain and corresponding malts. The aim of this study was to evaluate the relationships between the content of FA in grain, malt, and wort with malt quality characteristics such as hot water extract (HWE) and apparent attenuation limit (AAL) in different commercial malting barley varieties. High and positive correlations were found between myristic acid and HWE (r = 0.71) and between stearic acid and AAL (r = 0.76), with intermediate correlations between palmitic, oleic, linoleic, and linolenic acids and AAL (r = >0.50) in grain. High and negative correlations were found between stearic acid and HWE (r = -0.66), and high and negative correlations were found between palmitic (r = -0.74) and linoleic (r = -0.60) acids and AAL in the wort. Results from this study showed that lipids, as well as the combination of unsaturated and saturated FA, might play a role in determining differences in HWE and AAL between the barley varieties analyzed. No clear evidence on HWE was observed when grain and malt samples from the same variety were compared. These results indicated that lipids and FA should be considered together with starch properties to explain differences between HWE and AAL.

The role of total lipids and fatty acids profile on the water uptake of barley grain during steeping

Steeping is the first operation of malting and its overall purpose is to increase the water content of the grain, as well as to activate the enzymatic pool in the endosperm. The aim of this study was to evaluate the effects of total lipids content and individual fatty acids on water uptake, by commercial barley varieties. The results from this study showed that unsaturated fatty acids, such as oleic acid (18:1-n9), have a role in controlling water uptake by the barley endosperm during steeping. When partial least squares (PLS) regression was used to relate total lipids, individual fatty acids and water uptake, oleic (18:1-n9) acid had a positive effect, while long chain unsaturated fatty acids such as arachidic (20:0) and lignoceric (24:0) acids had a negative effect on explaining 72% of the total variability in water uptake. Water uptake by the endosperm is just a component of the system that is responsible for the overall malt quality properties and chemical characteristics of a given material. In this context, both total lipids and individual fatty acids have a role on determining malt quality in barley.

Study of Water Uptake in Whole Grain Barley by Two-Dimensional Correlation Near-Infrared Spectroscopy

ABSTRACT This study reports the use of near-infrared (NIR) reflectance spectroscopy combined with two-dimensional correlation (2D-COS) spectroscopy to monitor the effect of soaking and water uptake by the barley endosperm (Hordeum vulgare, L). The synchronous 2D-COS maps derived from the NIR spectra of barley endosperm showed similarities that could be explained by the regions in the spectra associated with water as well as with the biochemical and biophysical changes as a consequence of the water uptake by the grain. The results also demonstrated the potential of 2D-COS combined with NIR spectroscopy as an analytical tool to study changes in the biophysical characteristics of whole barley during steeping or soaking. This method can be used to obtain information about the effect of water uptake in other chemical characteristics of the endosperm of cereal grains.

The use of near infrared spectroscopy as a tool to optimise the steeping process during malting of barley

Introduction T he conversion of barley grain into malt is a complex process involving germination of the grain under controlled conditions. 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. 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. 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 endquality characteristics of the resulting malt. 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. 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. 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). 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 (Hordeum 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). Samples were removed at hourly intervals 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. 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 transform (FT) multiple processor analyser (MPA) (Bruker Optics, Germany) spectrophotometer (12,500–3600 cm) using a cylindrical glass cell (20 mm diameter × 50 mm height) at 16 cm spectral resolution. 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 crossvalidation. Before PCA analysis, the NIR data were transformed using the standard normal variate (SNV) processing or the second derivative Savitzky–Golay (2 derivative, 40 smoothing points).