A Model for Predicting the Effects of a Steeping Program on the Germination of Barley with Different Water Sensitivities

Abstract

A method for modelling and simulation of malting barley during and after steeping was developed. The modelling was based on data from laboratory scale experiments with various steeping programs. The developed model takes into account the steeping program with different wet steep and air rest periods, the average moisture content of the grains, and the water sensitivity of the raw material, malting barley. The model can be used for the analysis of steeping and the subsequent germination process and for planning of the steeping programs for achieving homogeneous germination in malting.Key words: Germination, malting, mathematical model, steeping, water sensitivity. -2863(9'8-32Water is an important factor that controls the physical phenomena and chemical reactions in biological materials during processing. In malting, water is needed to start and maintain the germination of seeds in order to produce hydrolytic enzymes and the subsequent hydrolysis of biopolymers leading to endosperm modification. Correct moisture of the germinating seeds is essential for balanced modification. Homogeneity of the raw material, i.e., similarity of the kernels of malting barley both as to physical structure and germination properties, and control of the malting process determine the homogeneity and quality of the end product, malt.Barleys have different degrees of dormancy and water sensitivity as a result of the weather conditions during the grain filling and harvesting period. Dormant embryos are temporarily unable to germinate whereas water sensitive barleys can germinate and are ready to be malted if favourable steeping programs with sufficient air rest periods are used. Simultaneous chitting of the individual kernels enabling an even start of the germination process is needed for the production of homogeneous malt. The steeping program is important not only for the germination but also for the water uptake of the kernels determining the final steepout moisture. A simulation model for describing the water uptake has been published earlier.2 The present paper focuses on modelling the effects of wet and dry periods in the steeping, the water sensitivity of the barley to be malted and the temperature on the homogeneity of germination, i.e., the proportion of grains that germinate during the first day, second day etc. 1%8)6-%07 %2( 1)8,3(7Batches of eight 1 kg barley samples were steeped and germinated in a micromalting unit (Joe White Malting System, Australia). Crop 1993 Kustaa malting barley with 11.6% protein was used in the experiments that were carried out later in 1994. After harvesting, barley was dried to 11% moisture and stored at room temperature. Before steeping barley was screened and the over 2.5 mm fraction was used in the trials.Four sets (A, B, C, D) of eight steeping programs were applied using temperatures between 10 and 20°C. A, B, and C were applied at two temperatures and D at three temperatures (Table I). The experiments were also previously utilised for modelling the water uptake during steeping 2 . The germin...

A Simulation Model for Malt Enzyme Activities in Kilning

“…The models for the enzyme activities during kilning are based on a set of controlled experiments that were designed to cover the normal steeping, germination and kilning conditions with the measurement of essential variables at each malting stage. Thus several models could be developed and many of them have already been published [4][5][6]10 . The biochemical analyses are laborious and thus only a limited number of repeated analyses were possible in practice.…”

“…The following parameter values were obtained when all experiments (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13) were included in the estimation set: d = 2.0 1/s, s = 0.8886 1/s, a 1 = 2.172, a 2 = 0.4725, a 3 = 1.219, and m f = 0.06382 s. Fig. 1 shows the measured and predicted moisture for experiments 1, 5 and 9.…”

“…Dynamic models for the drying of kernels and the survival of starch hydrolysing activities of ␣amylase, diastatic power and limit-dextrinase as well as ␤-glucan hydrolysing ␤-glucanase were developed. The paper completes a series of authors' previous articles focusing on modelling and simulation of the malting process [4][5][6]10 .…”

A Simulation Model for the Control of beta-Glucanase Activity and beta-Glucan Degradation During Germination in Malting

“…Coonce et al 1 modelled malt drying and certain quality changes during kilning. Holmberg et al 2,3 described models for water uptake during steeping and the effect of the steeping program on the homogeneity of germination. Kuusela et al 9 developed a combined index for malt modification, i.e., for the description of barley structure change during malting.…”

“…For instance, Hämäläinen et al developed mathematical models for the main phenomena of mashing that were also incorporated into a simulation program that has been used in practical brewing (see Hämäläinen et al 6 and the references therein). Only a few papers have been published on the modelling of the barley malting and related phenomena [1][2][3]5,9,13,14 . Pietzsch et al 13 proposed two models for barley moisture as a function of time at a single constant temperature steeping.…”