THE USE OF CHEMICAL AGENTS TO OVERCOME DORMANCY IN MALTING BARLEY*

Treatments were applied to dormant grains pre-drying, during dry storage and in the immediate pre-steep period. The effects on rates of recovery from dormancy were assessed. Only applications of sulphuric acid and gibberellic acid in the pro-drying period subsequently enhanced germination. No treatments applied during dry storage were beneficial. It appeared that oxygen was not needed during storage for grain maturation. Atmospheres of carbon dioxide applied during warm storage reduced subsequent germination but this gas was without effect on grain stored at ambient temperatures. Steeping grains in dilute solutions of mineral acids and some sulphur containing compounds improved their germinability.     

Monitoring a Commercial Barley Store in the North of England and Comparison with a Computer Simulation of Germination

The temperature, moisture and germination variations in a commercial barley store were monitored over two seasons. Initial mean temperatures of 49 and 46°C were observed. These were higher than the safe temperatures for germination predicted by the computer simulation, but still produced maltable barley. This suggested that the model was too conservative. During cooling the air was heated and the bed dried by an average of 1.5%. This ‘dryeration’ effect helped the barley to withstand the higher temperatures. Differential fan control and off‐peak running were tested and the higher 6°C differential control was shown to reduce rewetting. However, lower and more uniform temperatures were achieved with a 2°C differential. The downward flow system was essential to avoid condensation and did not pose any other serious problems. Some of the maltsters' reservations regarding cooling below 15°C, due to concerns over secondary dormancy and reheating to steep temperatures, should be alleviated by this work. Given the range of fan control options that still need to be investigated, computer simulation of the cooling, drying and germination in storage is recommended as a lower cost option than commercial testing.     

Dormancy in Stored Malting Barley: Quantifying the Rate of Break and the Effect of Cooling

The rate of break of dormancy of the varieties Plaisant, Fanfare, Pearl, Halcyon and Chariot, was examined at storage temperatures of 8, 16, 25 and 33°C. The data was fitted using a probit model and the results were compared with those for three previously tested varieties, Triumph, Blenheim and Pipkin. Three varieties - Plaisant, Fanfare and Pearl - were found to emerge from dormancy more slowly than the slowest previously-tested variety, Triumph, suggesting that breeding programs are not assigning a high priority to the issue of dormancy-break-rate. Data provided by Cochrane was also fitted, quantifying the rate of break for a further three varieties. To make the results more accessible to maltsters and store managers, a three-level banding scheme has been proposed. A second experiment examined whether sudden cooling could induce ‘secondary dormancy’. Samples of Fanfare and Plaisant were stored at 12% and 15% moisture content, and dormancy was broken at 33°C and 25°C. Samples were transferred to 8°C at different times. Cooling did not result in a drop in Germinative Energy. Evidence of ‘secondary dormancy’ was not observed.     

Dormancy in Malting Barley: Quantifying the Effect of Storage Temperature on Different Varieties and the Response to Sudden Cooling

The rates of break of dormancy of the varieties Blenheim and Pipkin were examined during storage at temperatures of 8, 18, 26 and 33°C. The results were fitted to an established probit model of dormancy and compared with the previously fitted equations for Triumph. Triumph was shown to be the variety with the slowest recovery rate and this was consistent with the observations of other researchers. A similarity between varieties in the change of recovery rate with temperature suggested a consistency in the controlling reaction. A second experiment examined whether the sudden cooling of warm barley could induce ‘secondary dormancy’. The variety Triumph was stored at 12% moisture content and 33°C. Samples were then transferred to 8 or 15°C at different times. This procedure did not bring about any significant reduction in germinative energy. The only effect of a sudden temperature drop was a reduction in the rate of emergence from dormancy. ‘Secondary dormancy’ was not induced. The work is introduced and the results discussed in the context of the development of a thermally based integrated control strategy for malting barley. The strategy was designed to minimise the use of chemicals.     

MOBILISATION OF ENDOSPERMAL RESERVES DURING THE GERMINATION OF BARLEY

The metabolism of the germinating barley seed is a complicated physiological process. From the point of view of industrial malting, the syntheses of amylolytic and proteolytic enzymes as well as the degradation of endospermal structures are extremely important. In order to control his process the maltster needs to have a good understanding of these processes as well as of the regulatory mechanisms which control them. When a good malting barley is allowed to germinate under traditional conditions for the time needed, a good malt can be produced without this scientific background. The present day brewing industry, however, has to work with barleys which are not of the traditional malting type and furthermore accelerated processes are an economic necessity. Under these circumstances, the maltster needs all scientific help he can get. Biochemical and physiological research on germination provides him with the tools he needs for process control and optimisation.     

A RAPID SMALL SCALE METHOD FOR THE DETERMINATION OF MALT EXTRACT

A rapid, small-scale method was developed using 1 g of ground malt mashed in 10 ml of water at 65°C. The extract was centrifuged and the specific gravity determined using a density meter. The method was compared with an earlier small-scale method and the Institute of Brewing method and was found to have good precision (CV 1.2%). Absolute malt extract values were not significantly different (P = 0.05) from those obtained by the IOB method.     

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.     

IAA,ABA AND GERMINATION OF SPRING BARLEY CARYOPSES DURING POST-HARVEST MATURATION

Changes in the content of indole-3-acetic acid (IAA) and abscisic acid (ABA) were investigated in the caryopses of three spring barley varieties (Alexis, Akcent and Rubin) shortly before harvest and during post-harvest maturation. Simultaneously, the values of the germination index and germinating energy were followed after harvest. The differences in endogenous contents of the phytohormones were determined in the caryopses of all three barley varieties which showed a decreasing pattern during post-harvest maturation while in contrast the values of the germinating energy and germination indices increased. Significant differences were observed between the varieties .     

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 .     

Effects of Genotype and Environment on Malt β-Glucanase Activity

Fifteen genotypes of barley grown in two different locations (Gönen and Besni) were used in this study. The malting characteristics and β-glucanase activities of their malts were determined. Although, malt β-glucanase activities of the samples grown in the Besni location were much higher than those of Gönen samples, the malting quality of the samples from both locations were comparable. The results indicate that both genotype and environment affected β-glucanase activity with a more pronounced effect of the latter.     

THE EFFECT OF KILNING ON THE CAPABILITY OF MALT TO OXIDISE LIPIDS

The influence of kilning on the ability of malt to oxidise lipids was studied. Barley was malted with a standard programme and subsequently dried with varying kilning procedures. The capability of samples taken during kilning to oxidise lipids was determined by the lipoxygenase (LOX) reaction, i.e. by measuring O₂ consumption in an aqueous suspension of samples upon addition of excess amounts of exogenous linoleic acid. Various kilning programmes from isothermal low-temperature kilnings to kilnings with varying temperature profiles induced a two- to threefold increase in the rate of the LOX reaction in the samples taken during the first two to six hours of kilning. However, when lipid changes in the intact kernels were measured, oxidation of the endogenous malt lipids was very limited during the first half of kilning. Furthermore, the rate of the LOX reaction decreased in samples taken during the latter part of kilning, the rate of decrease depending on the kilning programme and especially the final curing temperatures. These results indicate that a possible risk of a marked ability to oxidise lipids remains at moderate kilning temperatures. In conclusion, kilning induces a significant capability to oxidise lipids but does not affect the fatty acid composition of whole kernels. However, in aqueous suspensions of ground malt the oxidative instability created might lead to oxidation of lipids .     

Assessment of Barley Quality by Light Transmission - the Rapid LTm meter

An estimate of the quality of barley endosperm can be obtained from the proportion of light that is transmitted through the grain. Barleys with steely endosperm structure transmit more light than those with mealy endosperm structure. The LTm meter can be used to assess these grains quickly, simply and effectively. By analysing single grains of each sample it is possible to obtain an estimate of endosperm homogeneity. LTm assessments of endosperm quality and homogeneity are related to the quality of malt made from that barley as indicated by either the Calcofluor test or by the LTm meter itself. Thus the LTm meter can be used to predict malting performance from barley quality.     

AREAS OF ABSORPTION RELATING TO MALT EXTRACT VALUE IN MODIFIED NEAR INFRA-RED SPECTRA OF BARLEY FLOUR

Determinations of milling energy, nitrogen, acid-soluble beta glucan and malt extract after micromalting, were made on grain samples of twenty nine barley cultivars. In addition the flour from unmalted grains was scanned over the near infra-red spectrum, and the scan data were subjected to a principal components analysis (PC). Predicted malt extract values resulting from an NIR multiple regression equation with PC terms, correlated well (r = 0.934) with the manual extract values. This confirms previous evidence that malt extract value depends largely on constituents in the resting grain, rather than on malt enzymes. An attempt to locate NIR absorptions relating to malting quality was made by restructuring the NIR spectrum of the samples according to the weightings modified by the regression coefficients in the PC regression equation for hot water extract value. The spectrum reconstructed in this way showed a number of absorption peaks and troughs. From comparison with previous NIR scans it was concluded that a strong peak at the wavelength 2100 nm was due to a starch absorption and this together with minor starch overtone peaks correlated positively with malt extract. Troughs at 2180 nm, 1980 nm and 1700 nm indicated a negative association between malt extract and some proteins. There were also wide troughs at 1830 and 2330 nm indicating a negative relationship between malt extract and beta glucan. Other peaks and troughs in the reconstructed spectrum could not readily be assigned to a constituent. A reconstructed protein spectrum consisted of peaks and troughs that agreed with previous assignations for protein absorbancies. A milling energy reconstruction was approximately the inverse of the malt extract spectrum, and an acid-soluble beta glucan reconstruction was relatively featureless and appeared to be due to the effects of particle size variations.     

A MICROBIOLOGICAL EVALUATION OF BARLEY MALT PRODUCTION

The development of the microflora of barley malt was examined by direct and dilution plating. At all stages of the malting process mesophilic bacteria predominated. Viable counts of bacteria on green malt were 85–600 times greater than on the original barley, but fell to less than one-half of the original level with kilning. Corresponding increases in yeast and, especially, mould counts during malting were smaller. The yeast-like mould Geotrichum candidum was prominent in green malt. Although counts of yeasts and most moulds were considerably reduced by kilning, Mucor spp. proliferated during kilning.     

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.     

EVALUATION OF THE INFRAALYZER 400 FOR THE ANALYSIS OF BARLEY AND MALT

A collaborative study is described of the use of infra-red reflectance for the evaluation of the analytical characteristics of barley and malt. Transfer of centrally-prepared calibrations to other reflectance machines was found to be possible for moisture content and protein content in barley and malt but not for malt extract or malt modification. The examination of infra-red reflectance results, obtained at different wavelengths, by step-wise ascending regression rather than step-wise descending regression showed that the former was more satisfactory, especially in being more rapid in execution.     

Scotch Malt Whisky Distillers Malted Barley Specifications. Twenty Years of Fermentable Extract and Predicted Spirit Yield

Some maltsters and distillers have now used the Recommended Methods of Analysis for Malt Extract and Unboiled Wort Fermentability as a basis for trade for twenty years (1979–1998). As in the first decade of use, there have been ongoing changes in laboratory analysis, barley varieties and production scale processes in the second decade. The opportunity to study effects of such changes on the validity of the analytical methods and predicted spirit yield calculations in the second decade has been taken, as has a study spanning the twenty years. It is concluded that the Recommended Methods, and calculations based on them, are still valid.