A COMPUTER CONTROLLED MICROMALTER FOR ASSESSMENT OF THE MALTING POTENTIAL OF BARLEY CROSSBREDS

An automatic, computer-controlled micromalter with several advantages over current designs has been constructed. All operations are carried out in the one cabinet, and it is not necessary to intervene at any point during the malting process. The sample containers were constructed so that mechanical deculming of groups of ten large or fifteen small samples could be carried out in ten minutes. Initially, the capacity of the micro malter was 40 × 100 gm or 70 × 60 gm samples. These capacities were doubled by the use of longditudinal dividers slid into each canister, making the apparatus suitable for screening of samples submitted from the early generations of a breeding programme. The results obtained by malting 36 large and 60 small samples of the same variety; six replicates of six varieties; and subsamples of a bulk of a single variety in 37 subsequent runs all indicated that the instrument provided satisfactory separation and ranking between samples of differing malting qualities and grouped samples of similar malting qualities together.     

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.     

A COMPARISON OF SOME RAPID SCREENING TESTS FOR MALTING QUALITY

A series of rapid tests which have been proposed for the assessment of barley malting quality have been compared. The most accurate prediction of hot water extract was obtained by a multiple regression involving α-Amylase, Total Nitrogen and Grinding Resistance.     

AN ASSESSMENT OF THE MALTING QUALITY OF A MUTANT OF THE BARLEY CV. TROUBADOUR GROWN UNDER SCOTTISH CONDITIONS

The barley mutant, TR49, selected in Spain for rapid germination, and its parent cultivar Troubadour, were grown in Scotland in 1991 and assessed for a range of grain and malt quality characters. Results suggested that both genotypes had a potential dormancy problem, although TR49 showed a slight but significant improvement over Troubadour. TR49 produced very large grain which did not completely modify during malting, but still showed an advantage over its parent cultivar for all malting parameters assessed.     

STUDIES ON THE MALTING POTENTIAL OF BARLEY AND MALT WITH THE FALLING NUMBER APPARATUS

The Falling Number Apparatus was investigated as a possible technique for the identification of barleys and malts with high malting potential. The FN method was not as accurate or as rapid as that based on Pearling Resistance. The effect of increasing times of malting on the Falling Times of malts was also investigated to determine whether the progress of malting could be monitored, as was the effect of different cultivars. Testing under conditions inhibitory to amylolytic activity was found necessary to give useful results. Some comparisons with the Rapid Visco Analyser (RVA) are presented.     

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.     

EUROPEAN BREWERY CONVENTION RANKING OF BARLEY VARIETIES FOR MALTING QUALITY

The barleys grown for the E.B.C. Barley Committee in a number of countries have been malted on the small scale in three different ways (conventional procedures, a procedure using gibberellic acid and a hot water resteeping method) in three successive years. The analyses of the resulting malts, and the procedures used to make them, have been statistically examined and it has been found that the ranking of barley varieties for quality shows very good agreement between the different methods, both between varieties and between years. Thus it is confirmed that, even with micromalting methods as dissimilar as the three now studied, barley varieties will in general be ranked in a constant order of excellence.     

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.     

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.     

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.     

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.     

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.     

LIPOLYTIC AND OXIDATIVE CHANGES OF BARLEY LIPIDS DURING MALTING AND MASHING

Lipolytic and oxidative changes of barley lipids were studied during malting and mashing. The amount of lipid decreased by 23% during malting and changes in the composition of lipid classes were minor. On the other hand, during mashing the amount of free fatty acids (FFA) increased which indicated, that lipid hydrolysis had occurred. The same phenomenon was seen when malt flour was soaked in water at 23°C. The triglyceride (TG) and polar lipid (PL) contents were reduced and the proportion of FFA in total lipids was increased. Following similar soaking of barley flour, TG and PL were reduced but the accumulation of FFA and especially linoleic acid (LA) was slight. The results were consistent with the data on lipoxygenase activity (LOX) during malting. During steeping LOX decreased and was 15–20% of the activity of raw barley at the beginning of germination. The activity remained low during germination but rose sharply in the middle of kilning only to decrease again to a very low level at the end of kilning (5%). This in combination with the fact that the proportion of FFA remained high in the soaked malt samples suggests that the oxidation by LOX is negligible in the malt samples. However, the data suggest that mashing of barley, but not that of malt, includes the potential for the formation of highly polar lipid oxidation products.     

ON-LINE MEASUREMENT OF THE MICROBIAL IMPACTS ON THE GERMINATION OF BARLEY DURING MALTING

During germination, the metabolic activity of sterile barley was more pronounced than the activity of barley contaminated by its endogenous microbial population. CO₂ and heat production profiles showed higher peak values when microbial activity was eliminated. Moreover, the maxima in the profiles appeared sooner than with barley in the presence of its natural microflora. More intensive growth of the acrospire was observed with sterile barley and a malt was obtained with a higher and more homogeneous modification. Reverse effects were noticed when sterile barley was inoculated with an Erwinia sp. strain and germination was evaluated. The results provide clear evidence for the strong interaction between microbial and plant metabolism, even for non dormant and non water sensitive barley. The ratio of CO₂ production to heat production levels was a useful tool for on-line monitoring of microbial activity during germination. In this way, the effects of the microbial activity can be taken into account in the development of a more effective control of the malting process. All experiments were performed using a specially designed solid-state reactor.     

EFFECTS OF THE MYCOTOXINS DIACETOXYSCIRPENOL AND DEOXYNIVALENOL ON MALTING CHARACTERISTICS OF BARLEY

In germination tests, the trichothene diacetoxyscerpanol (DAS) caused reductions in the number and total length of rootlets, and the length of the coleoptile, developing from excised barley embryos, but the effects were less than those of T-2 toxin. Rootlet and coleoptile growth was also inhibited during micromating of barley artificially contaminated with DAS before steeping, whilst α-amylase activity of finished malts were reduced by up to 49%, and α-amino nitrogen levels in worts were also lower than in controls. The effects of deoxynivalenol (DON) were less than those of DAS, e.g. the reduction in α-amylase activity caused by DON applied at the rate of 50 μg g-1 grain was less than one-half of that caused by 20 μg DAS g^?1.     

EVALUATION OF MALTING QUALITY IN A BARLEY BREEDING PROGRAMME USE OF α-AMYLASE AND β-GLUCAN LEVLES IN MALT AS PRESELECTION TOOLS

Analysis according to the EBC protocol, immunological determination of a α-amylase and estimation of malt β-glucan using the Calcofluor-FIA method, were used to screen 327 barley breeding lines for malting quality. The results obtained with the α-amylase and β-glucan methods are highly correlated to the important malt quality paramters: extract yield and β-glucan content in the wort. It is recommended that either of the two methods, which are simple to perform are used as prescreening tools in breeding programmes for malting barley.     

COMPARATIVE MALTING PERFORMANCE OF OLD AND NEW BARLEY VARIETIES

A comparison was made of the malting behaviour of eight barley varieties representing a range from ancient to modern types. Plants were grown under controlled conditions in a glasshouse with two different nitrogen treatments and the grain obtained was subjected to a factorial micro-malting analysis. Under the conditions of this experiment there was little evidence of an improvement in malting ability between Plumage Archer and Ark Royal and there is limited scope for further increases in potential hot water extract. It would therefore appear that emphasis should now be given to the production of varieties with good agronomic characteristics which maintain this potential and modify rapidly without the need for abrasion and exogenous GA₃.     

ASSESSMENT OF MODIFICATION PATTERNS IN MALTING BARLEYS

Three cultivars of diverse melting quality were melted end samples taken daily between 2 end 7 days germination. Over this period a linear relationship wee observed in all 3 cultivars, between cell well modification, measured by loss of calcofluor fluorescence, and both wort nitrogen content end loss of milling energy. Differences in the slopes of regression lines suggested variation in patterns of modification, with very rapid proteolysis in Triumph, but a time leg between cell wall modification and degradation of the protein matrix in Koru. These predicted patterns were confirmed by Scanning Electron Micrographs of endosperms from germinated grains.