THE EFFECT OF MOISTURE AND NITROGEN LEVELS ON MILLING ENERGY OF BARLEY

Milling energy values of both spring and winter cultivars of barley are shown to be highly influenced by moisture content of samples. Within the range 10 to 18% moisture, the relationship between milling energy and moisture content was linear. For spring barley, milling energy values could be adjusted to a common moisture content of 12% using a correction factor of 25 Joules for each percent moisture. Nitrogen content of malting samples correlated poorly, although still at a significant level, with milling energy and considerable variation in grain hardness could be observed at any nitrogen level considered suitable for malting.     

ASSESSING MALTING QUALITY BY THE AUTOLYSIS OF BARLEY

There has been prolonged speculation over the past thirty years on the relationship between the properties of aqueous extracts of barley and malting quality. On reviewing the literature on this subject, the concensus of opinion is that the total amount of gum or β-glucan in the barley does not correlate with malting quality. The cytolytic potential of both barley and malt, on the other hand, appears the more important parameter. Present evidence is that measurements made on aqueous extracts, either by viscosity or β-glucan determination, are more indicative of barley cytolytic activity than they are a true measure of gum content. Low β-glucan values in some barleys may therefore be artefacts of enzymic hydrolysis.     

EFFECT OF IRRADIATION ON THE MALTING QUALITY OF BARLEY

Two six-row barley cultivars, DL 70 and C 164 were subjected to Co⁶⁰ gamma irradiation in the range of 0 to 250 Krad and malted with and without gibberellic acid treatment. Barley irradiated with doses up to 75 Krad produced normal malts when compared to the controls. Irradiation doses of 125 and 250 Krad significantly increased the malt yields but considerably decreased the α-amylase activity. Gibberellic acid significantly increased the enzyme activity and degree of modification of the irradiated and the control malts.     

ASSOCIATIONS OF THE WAXY (wx) GENE WITH MALTING QUALITY CHARACTERS IN RANDOM INBRED LINES OF BARLEY

Inbred lines were developed from a cross between a waxy and a non-waxy barley, enabling populations with and without the waxy gene to be compared. For all quality characters measured, both waxy and non-waxy types demonstrated wide ranges and waxy lines with fairly high levels of thousand corn weight and hot water extract were obtained. Over three seasons, milling energies were always significantly higher in waxy compared with non-waxy lines and, in waxy types, milling energy was closely related to rate of cell wall modification during malting. In a season, where grain weights were fairly high, the mean extract of the waxy population was significantly lower than that of the non-waxy and it was suggested that large grain could be disadvantageous in waxy lines due to their slow rate of modification.     

THE USE OF PARTIALLY-MODIFIED BARLEY FOR MALTING QUALITY ASSESSMENT

A series of tests based on the changes in the characteristics of barley caused by partial malting were investigated for selection of progeny with high malting potential from a breeding programme. The characteristics of these partially-modified barleys were investigated using NearInfraRed Reflectance Spectrophotometry (NIR), Pearling Resistance (PR), changes in Viscosity of Acidic Extracts, and changes in weight and translucency of the cut surface of boiled grains. NIR carried out on “day-malts” was found to be accurate, whereas other methods were insufficiently accurate for selection.     

HOMOGENEITY OF THE FRIABLE FLOUR OF MALTING BARLEY

A detailed comparison was made of the properties of the friable flours and non-friable residues of two samples of malted barley of different nitrogen contents. The friable flours were sieved and fractionated to give a range of particle sizes, and the intact malt, whole friable flour, non-friable residues and fractionated friable flours were subjected to a range of analyses. Endosperm fractionation studies showed that the pattern of enzymic degradation of proteins in the modified friable flour of low nitrogen malt was more uniform than the corresponding pattern of protein breakdown in the friable flour of high nitrogen malt. Examination of the non friable residues showed that cell wall breakdown in the high nitrogen malt was less extensive than the low nitrogen malt. It is proposed that the high protein levels in the endosperm caused starch/protein compacting which limited endosperm hydration and enzymic modification during malting. The friability scores of high nitrogen malts may given an over estimate of endosperm modification.     

PREDICTING THE GERMINATIVE ENERGY OF DORMANT MALTING BARLEY DURING STORAGE

The management of dormant barley stocks for malting requires a method of predicting germinative energy under given conditions during storage. A method of quantifying the relationship between storage temperature and the dormancy period is developed based on probit analysis. The experimental data were obtained using Triumph barley. The conditions covered in the experimental work were 8°C to 38°C storage temperature at 12% moisture content, wet basis. Combined use of the dormancy model with an existing viability model allows the prediction of germinative energy as a function of storage temperature and moisture content given the initial germinative energy and capacity values. The effects of storage temperature on the variation in germination over time of dormant bariey samples with various initial germinative capacities, and storage moisture contents are investigated using the model. The results indicate that storage at moisture contents below 12% give significant increases in the germination level that can be achieved.     

EFFECTS OF GAMMA IRRADIATION OF BARLEY AND MALT ON MALTING QUALITY

Two two-rowed barley cultivars, Tokak and Clerine, were irradiated at two different dose ranges (0.05–0.75 kGy and 0.5–5.0 kGy) using a ⁶⁰Co source. Irradiation of barley at the medium levels before malting had detrimental effects on most of the malt quality criteria. The detrimental effects of irradiation was lower at doses up to 0.25 kGy. Irradiation of malt samples caused either slight or no deterioration of quality characteristics .     

A RAPID TEST FOR THE PREDICTION OF MALTING QUALITY OF BARLEY

A grinding energy method developed for the prediction of the nutritional value of grass was adapted and used to differentiate barleys of good malting quality from those difficult to malt. This is a very rapid test (a few minutes per sample) and could be used as an initial step in screening for malting quality.     

PATTERNS OF MODIFICATION IN MALTING BARLEY

The modified regions of the starch endosperms of malted grains were fragile and, in thin sections, the cell walls in these regions did not stain readily with Congo Red or Trypan Blue, although scanning electron microscopy demonstrated some cell-wall material remained. Initially the enzymes causing modification came from the scutellum, but later more came from the aleurone layer. Patterns of modification in different grains differed significantly, but usually resembled those recorded previously⁶ except that often modification had advanced further by the nucellar sheaf cells. In grains treated with gibberellic acid modification advanced faster, particularly beneath the aleurone layer, after two days germination. In tumbled or commercially abraded grains, malted with gibberellic acid, modification was even more rapid, but in more than 99% of the grains the same patterns of modification occurred. Two-way modification was a rare event. Rapid, general sub-aleurone modification occurred in grains cut at the apex and dosed with gibberellic acid. Decorticated grains modified exceptionally quickly and, when treated with gibberellic acid, massive subaleurone modification occurred. The cell walls of the tissues that resisted modification fluoresced strongly in ultra-violet light, in contrast to those of the starchy endosperm.     

EFFECT OF STORAGE TIME ON THE MALTING QUALITY OF SOME BARLEY VARIETIES

Changes in the malting quality of some barley varieties were monitored at monthly intervals from harvest All the varieties were found to improve after storage for up to one year. Varieties with poorer malting grades improved at a faster rate than good varieties, although ranking consistent with malting grade was maintained.     

THE EFFECT OF CULTIVAR MIXTURES ON MALTING QUALITY IN WINTER BARLEY

A range of winter barley cultivars was grown, either as pure stands or as components of mixtures, in a trial in 1995–96. For malting quality characters, mean values of mixtures did not differ from mean values of the appropriate monocultures, except for decreases in homogeneity, as determined by a fluorescence test of cell wall modification. When disease pressure was modified by fungicide, hot water extract was not significantly altered, although this may have been due to the restriction of malting to grain retained by a 2.5 mm sieve. One mixture, comprised of three related winter malting cultivars, gave higher hot water extracts than its components, as pure stands, with no adverse effects on homogeneity. This was not simply attributable to lower grain nitrogen content .     

GRAIN AND MALT MILLING ENERGIES RELATIVE TO MALTING QUALITY PARAMETERS IN A MUTANT OF cv. TROUBADOUR

The mutant barley genotype TR49 and its parental cultivar Troubadour were grown at 5 sites throughout Spain in 1990. Large differences between sites were observed for a range of grain and malt quality characters. TR49 had very slightly higher milling energy in the grain than Troubadour, but, during the early stages of malting, showed a more rapid loss in milling energy. From the relationship between milling energy and other quality parameters, this was deduced to result from a more efficient and extensive modification of the endosperm cell walls in the mutant genotype.     

THE MALTING QUALITY OF SOME SPRING BARLEY VARIETIES GROWN IN ENGLAND AND WALES BETWEEN 1880 AND 1980

The malting behaviour of fifteen barley varieties widely grown between 1880 and 1980 has been compared using material grown at two sites in England in 1980. All the varieties examined were considered to be of malting quality at their time of widespread commercial use. Varieties introduced after 1950 gave higher Hot Water Extracts (mean 74·7%) than varieties introduced before 1950 (mean 71·0%), and when the yield data were included to calculate the yield of extract/ha the post-1950 varieties were found to exceed the older varieties by 48·7%. The Kolbach Index of the modern varieties was higher, although there was no evidence of an increase in cold water extract.     

PREDICTION OF THE MALTING QUALITY OF BARLEY BY A MODIFIED ZELENY SEDIMENTATION TEST

The Zeleny sedimentation test, developed to predict the bread-making quality of wheat flour, has been modified to predict the malting potential of barley samples. The test appears promising for the evaluation of malting potential of unknown varieties.     

TESTS FOR SELECTION OF MALTING QUALITY USING UNMODIFIED BARLEY

Various tests for malting potential based on unmodified barley were evaluated. These were based on NearInfraRed Reflectance Spectrophotometry (NIR), sedimentation of meals in cold alcohol or Lactic Acid/Sodium dodecyl sulphate solution, the content of total β glucan as measured by the viscosity of acidic extracts. NIR and sedimentation in Lactic Acid/SDS were found to be the most applicable to the breeding programme at this Institute, whereas the methods based on total β glucan or sedimentation in cold alcohol were unsuitable. The method based on soluble β glucan was only suitable to a breeding programme in which parents with known high β glucan content were used. An hypothesis for the contribution of total β glucan to malting quality is presented. None of the tests investigated were affected by declining dormancy or water sensitivity in the grain.     

APPLICATION OF A COMMERCIAL ENZYME PREPARATION IN THE BARLEY MALTING PROCESS

This paper presents data on barley micromalting with addition of the CELLUCLAST enzyme complex. This is a commercial, multicarbohydrase with distinct β-glucanase and proteinase activities. The enzyme was added to steeping and germination phases, in different quantities (0.05%; 0.75% and 0.1% of initial barley). The enzyme was added to different malting phases: to the 2nd and 3rd steep water, at the beginning of germination on the 1st day by spraying, on the 2nd day of germination and in combination of addition to 3rd steeping water and in germination start (50% of total quantity of each). CELLUCLAST enzyme had a significant effect on reduction of wort viscosity, extract difference, wort filterability and protein breakdown, depending on the quantity of added enzyme and the malting phase to which it was added. There was no negative effect on other malt quality parameters. The best values of cytolytic breakdown parameters (viscosity, extract difference, filtration rate) were obtained with addition of 0.075% of CELLUCLAST, on the first day of germination.     

THE MILLING ENERGY OF MALTED BARLEY AND ITS RELATIONSHIP WITH HOT WATER EXTRACT AND α-AMYLASE ACTIVITY

Hot water extract is dependant on endosperm structure and its breakdown during malting. These endosperm characteristics can be rapidly assessed on 5 g samples by measuring the milling energy of malted barley. α-amylase determinations on the resultant flour indicate that good malting barleys have either moderate or high levels of the enzyme. High levels of α-amylase will not confer good malting quality where endosperm modification has proceeded slowly.     

INFLUENCE OF SOIL NUTRIENT LEVELS ON HARVEST YIELD AND MALTING QUALITY OF BREWING BARLEY

Four levels of N, P and K nutrition (poor, moderate, satisfactory and high) and all their possible combinations with 64 treatments in two replications (128 plots) were studied in a long term field trial on barley yield and malting quality. A standard East-European spring barley “Opal” (bred in Czechoslovakia) was grown in 1986, 13th year of the agricultural experiment, involving various crops in previous years, on a calcareous loamy chernozem soil. The optimum fertility levels for yield enhancement resulted in the poorest malting quality: low modification and extract but long saccharification time and high protein. To solve this problem the brewing industry will have to apply the well-known technological methods available since growers are not likely to give up their fertilizers. Applying soil and plant analysis data, having knowledge about both soil and plant optimum values, the danger of the excessive use of fertilizers can be realized and decreased.