Brewing Performance of Malted Lipoxygenase‐1 Null Barley and Effect on the Flavor Stability of Beer

We examined the malting and brewing performances of a lipoxygenase‐1 (LOX‐1) null line of barley (Hordeum vulgare L.). The LOX‐normal malt and the LOX‐null malt were prepared from F₄ populations derived from a single cross. We could not observe any major differences in the general malt characteristics between the two malts. A brewing trial was performed using these malts. The analysis of the wort and beer revealed that the absence of LOX‐1 had little effect on the general characteristics of the wort and beer. In contrast, beer made from the LOX‐null malt showed reduced levels of beer‐deteriorating substances, trans‐2‐nonenal (T2N), and trihydroxyoctadecenoic acid (THOD). In the sensory evaluation, well‐trained panel members recognized the significant superiority of the aged LOX‐null beer in terms of staleness. These results show that the LOX‐1 null barley line can be effectively used to improve the flavor stability of beer without changing the other important beer qualities.     

The effect of mashing on malt endoproteolytic activities

During malting and mashing, the proteinases of barley (Hordeum vulgare L.) and malt partially hydrolyze their storage proteins. These enzymes are critical because several aspects of the brewing process are affected by the soluble proteins, peptides and/or amino acids that they release. To develop improved malting barleys and/or malting and brewing methods, it is imperative to know whether and when the green malt endoproteinases are inactivated during malting and mashing. These enzyme activities are totally preserved during kilning and, in this study, we have determined when they were inactivated during mashing. Samples were removed from experimental mashes that mirrored those used in commercial breweries and their endoproteolytic activities were analyzed. The malt endoproteinases were stable through the 38 degrees C protein rest phase, but were quickly inactivated when the mash temperature was raised to 72 degrees C for the conversion step. All of the proteinase activities were inactivated at about the same rate. These findings indicate that the soluble protein levels of worts can be varied by adjusting the protein rest phase of mashing, but not by altering the conversion time. The rates of hydrolysis of individual malt proteins probably cannot be changed by altering the mash temperature schedule, since the main enzymes that solubilize these proteins are affected similarly by temperature.     

Hardness Changes and Endosperm Modification During Sorghum Malting in Grains of Varying Hardness and Malt Quality

This study examined the interaction between sorghum grain hardness and sorghum malt quality in terms of diastatic power and free amino nitrogen with endosperm modification during malting. The changes in kernel hardness during malting of four commercial sorghum cultivars of differing quality in terms of endosperm texture and potential malt quality were measured using tests for hardness and density, and endosperm modification was followed by scanning electron microscopy. The general pattern of modification during sorghum malting was confirmed to start at the endosperm–scutellum interface and then continue into the floury endosperm toward the kernel distal end. Significantly, a cultivar of intermediate hardness and low malting quality remained harder and modified more slowly than a harder cultivar of high malting quality. It appeared that intrinsic grain hardness and malt amylase and protease activity both affected malt hardness and endosperm modification, but amylase and protease activity had a greater effect because of their degradation of endosperm starch and protein. Of the hardness and density tests studied, the tangential abrasive dehulling device (TADD) gave the best measure of hardness throughout malting; maximum range was 24–100% kernel removed over five days of malting. Also, the data agreed with the observed malt modification rates. Thus, the TADD may have application as a simple and rapid test for estimating sorghum malt quality.     

Fusarium Species on Barley Malt: Is Visual Assessment an Appropriate Tool for Detection?

Fusarium infections in malting barley cause mycotoxin contamination, quality impairment, and processing difficulties. The visual assessment of barley malt is a commonly applied practice in the malting and brewing industry to screen cereal batches for fungal infection, because it assumes a direct connection between occurring symptomatology and actual fungal contamination. The exceedance of a defined limit of red kernels (usually five to seven) in a 200 g subsample of malt is associated with an unjustifiable risk for further processing and can lead to reductions in price or the rejection of the entire batch. The present study evaluated the suitability of this method to ensure product quality and safety. It was further intended to resolve the presumed linkage between kernel discoloration and Fusarium infection. In general, symptomatology showed low predictability for Fusarium contamination. However, significant correlations became apparent between the number of discolored kernels and fungal DNA contents under conditions of higher levels of infection, although this was not the case for mycotoxin levels. Although symptomatology is likely overinterpreted in regard to its reliability as an indicator for Fusarium contaminations, it might still assist in assessing the risk of certain fungal contaminants.     

Improvement of malt modification by use of Rhizopus VII as starter culture

The development of a selected starter culture on malting barley and its effects on malt quality aspects were studied. Application of Rhizopus sporangiospores in a malting process resulted in increased beta-glucanase and xylanase contents of the malting barley and improved starchy endosperm cell-wall degradation. Activation of the sporangiospores and optimization of the inoculation procedure led to a further increase in enzyme levels and to larger and more consistent impacts on cell-wall modification. Whereas the main effect of the starter culture on beta-glucan degradation was observed during malting, a further decrease in beta-glucan during mashing suggests that the microbial enzymes that survived the kilning step were active during mashing. Other quality aspects that were influenced by the starter culture activity were protein modification, wort color, and wort pH. The level of microbial enzymes produced was related to the amount of barley kernels infected with the starter culture.     

Image Analysis of Grain and Chemical Composition of the Barley Plant as Predictors of Malting Quality in Mediterranean Environments

We have explored the possibility of predicting the malting quality of barley grain, indicated by malt extract yield, by characteristics measured either on plants at anthesis or in mature dry grain by image analysis. To produce barley samples with varying levels of all the characteristics studied, we used grain from an experiment designed to study the influence of lowinput husbandry practices on malting quality of barley by growing five malting genotypes at each of four environments (site × season) and with two different agronomic treatments (N fertilization and herbicide-mechanical roguing of weeds). The results showed that nitrogen content in the plant at anthesis was a good predictor of grain protein content, this characteristic in turn being positively correlated with embryo size and grain volume, as estimated by image analysis, and negatively correlated with nonstructural carbohydrate content in the plant at anthesis. Extract yield was positively correlated with Kolbach index (ratio of soluble to total wort protein) and negatively correlated with wort viscosity and barley grain protein content. Thus, the only practical predictor of malt extract was grain protein content.     

Improved Methods for High-Throughput Extraction and Assay of Green Barley Malt Proteinase Activity Facilitating Examination of Proteinase Activity Across Large-Scale Barley Populations

We report efficient sample extraction and assay methods allowing quantitative determinations of proteinase activities from barley malt. The improved methods are used to assay >2,200 developmental lines of malting barley for two subsets of proteinase activity. The distributions of the resulting activities suggest differences in population structures between the two types of proteinases. Comparison of the activities of the green malt proteinases with standard malting quality measurements show highly significant correlations that differ between the proteinase subsets. The pH 4.5 hydrolysis of the artificial substrate Z-Phe-Arg-AMC correlates well with the traditional malting quality measurements, supporting the role of cysteine-class proteinases in mobilization of grain reserves during malting and mashing. Results from assays of gelatin hydrolysis at pH 6.0 suggest that these proteolytic activities may be involved in other aspects of seed C and N dynamics also linked to malting quality measurements. The differences between the pH 4.5 and 6.0 activities assayed here and their association with malting quality measurements suggest different physiological roles for the two proteinase activities in several aspects of seed germination. Either assay could be useful for population surveys, depending on the particular facet of seed metabolism under study.     

Degradation of starchy endosperm cell walls in nongerminating sterilized barley by fungi

Strains of fungi from different origins, including isolates of the natural microflora of barley, were screened for their ability to modify barley starchy endosperm cell walls in situ. In an initial step, fungi were selected that degrade the major component of the cell walls, that is, (1-->3),(1-->4)-beta-D-glucan, in vitro on artificial media. Nongerminating, sterilized barley, obtained by gamma-irradiation, was inoculated with such fungi and subjected to solid state fermentation under conditions resembling those of a traditional malting process. For some strains of fungi, a clear correlation between the production of endo-beta-glucanase and the friability of the treated kernels was found. Image analysis of Calcofluor stained longitudinal sections of barley kernels fermented with the endo-beta-glucanase producing strains showed that starchy endosperm cell walls were modified. As malt quality is inversely related to its (1-->3),(1-->4)-beta-D-glucan content, the selected strains have high potential to be used as starter cultures during malt production, contributing to the processing quality of the final product.     

Germination and Malting Properties of Mutants Derived from Malting Barley cv. Triumph

Four mutants, demonstrating a range of dormancy, were derived from the malting barley cv. Triumph. Although there were environmental effects on the rate of recovery from dormancy, relative performance of the genotypes was consistent. Recovery from water sensitivity was slower than recovery from dormancy for all genotypes, but a similar ranking of genotypes was observed with two mutants germinating more readily than the parental genotype. Exposure of the grain to the plant hormone abscisic acid (ABA) at the end of each wet phase during steeping had a highly significant effect on the malting performance of all samples. However, reduction in extract levels was significantly less in the two mutants that demonstrated more rapid recovery from dormancy. None of the mutants exceeded Triumph for hot water extract level after malting in two seasons at sites in Dundee (eastern Scotland) and Lleida (northeastern Spain). However, one mutant combined rapid recovery from dormancy with high extract levels when grown and malted under Scottish conditions and subjected to unithermal hot water extraction.     

Dual positional and stereospecificity of lipoxygenase isoenzymes from germinating barley (green malt): biotransformation of free and esterified linoleic acid

The lipoxygenase isoenzymes LOX1 and LOX2 from green malt were separated by isoelectric focusing, and their catalytic properties regarding complex lipids as substrates were characterized. The regio- and stereoisomers of hydroperoxy octadecadienoates (HPODE) resulting from LOX1 and LOX2 enzymatic transformations of linoleic acid, methyl linoleate, linoleic acid glycerol esters monolinolein, dilinolein, and trilinolein, and 1-palmitoyl-2-linoleoyl-glycero-3-phosphocholine (PamLinGroPCho) were determined. In addition, biotransformations of polar and nonpolar lipids extracted from malt were performed with LOX1 and LOX2. The results show that LOX2 catalyzes the oxidation of esterified fatty acids at a higher rate and is more regioselective than LOX1. The dual position specificity of LOX2 (9-HPODE:13-HPODE) with trilinolein as the substrate (6:94) was higher than the resultant ratio (13:87) when free linoleic acid was transformed. A high (S)-enantiomeric excess of 13-HPODE was analyzed with all esterified substrates confirming the formation of 13-HPODE through the LOX2 enzyme; however, 9-HPODE detected after LOX2 biotransformations showed (R)-enantiomeric excesses. PamLinGroPCho was oxygenated by LOX1 with the highest regio- and stereoselectivities among the applied substrates.     

Analysis of pregerminated barley using hyperspectral image analysis

Pregermination is one of many serious degradations to barley when used for malting. A pregerminated barley kernel can under certain conditions not regerminate and is reduced to animal feed of lower quality. Identifying pregermination at an early stage is therefore essential in order to segregate the barley kernels into low or high quality. Current standard methods to quantify pregerminated barley include visual approaches, e.g. to identify the root sprout, or using an embryo staining method, which use a time-consuming procedure. We present an approach using a near-infrared (NIR) hyperspectral imaging system in a mathematical modeling framework to identify pregerminated barley at an early stage of approximately 12 h of pregermination. Our model only assigns pregermination as the cause for a single kernel's lack of germination and is unable to identify dormancy, kernel damage etc. The analysis is based on more than 750 Rosalina barley kernels being pregerminated at 8 different durations between 0 and 60 h based on the BRF method. Regerminating the kernels reveals a grouping of the pregerminated kernels into three categories: normal, delayed and limited germination. Our model employs a supervised classification framework based on a set of extracted features insensitive to the kernel orientation. An out-of-sample classification error of 32% (CI(95%): 29-35%) is obtained for single kernels when grouped into the three categories, and an error of 3% (CI(95%): 0-15%) is achieved on a bulk kernel level. The model provides class probabilities for each kernel, which can assist in achieving homogeneous germination profiles. This research can further be developed to establish an automated and faster procedure as an alternative to the standard procedures for pregerminated barley.     

Starch Lipids of Barley and Malt

Barley and malt starches were compared with respect to their lipid content and composition. The starch lipids were first fractionated into internal and surface lipid fractions followed by lipid class and fatty acid analyses of each fraction. Barley starch contained 13 mg/g lipids, of which 9.3 mg were internal lipids and 3.7 mg were surface lipids. The total lipid content of malt starches varied between 11 and 13 mg/g of starch. However, malt starch contained only 1 mg of surface lipids; therefore, the internal lipid contents were as high as or even higher than those in the corresponding fraction of barley starch. Lipid class analyses suggested that the ability for hydrolysis of starch surface lipids was increased in malt. The hydrolysis occurred during the malting or the isolation process, resulting in reduced surface lipid content in malt starch. However, no reduction in the portion of polyunsaturated fatty acids was seen; therefore, lipid oxidation could not have been responsible for the lower content of malt starch surface lipids. Also, not only was the content of starch internal lipids higher in malt, but the composition of these lipids was different when compared to barley starch. The increase in starch internal lipids during malting may be due to transportation and reacylation of free fatty acids that had been liberated by hydrolysis from surface lipids.     

In vivo modeling of beta-glucan degradation in contrasting barley (Hordeum vulgare L.) genotypes

An important determinative of malt quality is the malt beta-glucan content, which in turn depends on the initial barley beta-glucan content as well as the beta-glucan depolymerization by beta-glucanase (EC 3.2.1.73) during malting. Another enzyme, named beta-glucan solubilase, has been suggested to act prior to beta-glucanase; its existence, however, has not been unequivocally proven. We monitored changes in beta-glucan levels and in the development of beta-glucan-degrading enzymes during malting of five lots of contrasting barley genotypes. Two models of in vivo kinetics for beta-glucan degradation were then compared as follows: (i) a biphasic model based on the sequential action of beta-glucan solubilase and beta-glucanase and (ii) a monophasic model assuming that all beta-glucans are depolymerized by beta-glucanase without the previous intervention of another enzyme. Confirmatory regression analysis was used to test the fit of the models to the observed data. Our results show that beta-glucan degradation is mostly monophasic, although some enzyme other than beta-glucanase seems to be required for the early solubilization of a small fraction of insoluble beta-glucans (on average, 7% of total beta-glucans). Furthermore, the genotype-dependent kinetic rate constant (indicating beta-glucan degradability), in addition to beta-glucanase activity, is suggested to play a major role in malting quality.     

Evidence of the glycation and denaturation of LTP1 during the malting and brewing process

The influence of malting and brewing processes on the chemical and structural modifications occurring on LTP1 was investigated by mass spectrometry and circular dichroism. Proteins were first purified from malt, and samples were collected at various steps of beer processing performed on two barley cultivars. The levels of LTP1 found in malt were not significantly different from the amounts in barley seed. However, in malt, both LTP1b, a post-translational form of LTP1, and a third isoform named LTP1c were isolated. Moreover, both of these proteins were found to be heterogeneously glycated but still exhibited an alpha-helix structure. Both glycated LTP1 and LTP1b were recovered during mashing. It was also shown that glycated LTP1 was unfolded during heat treatment of wort boiling, which is in agreement with the denatured form previously isolated from beer.     

Quantitative study of the formation of endoproteolytic activities during malting and their stabilities to kilning

The proteinases of germinating barley (Hordeum vulgare L.) hydrolyze storage proteins into amino acids and small peptides that can be used by the growing plant or, during brewing, by yeast. They are critical for the malting and brewing processes because several aspects of brewing are affected by the amounts of protein, peptide, and amino acids that are in the wort. This study was carried out to quantitatively measure when endoproteinases form in green malt and whether they are inactivated at the high temperatures that occur during malt kilning. Little endoproteolytic activity was present in ungerminated barley, but the activities began forming 1 day into the "germination" phase of malting, and they were nearly maximal by the third germination day. Quantitative studies with azogelatin "in solution" assays showed that the green malt endoproteolytic activities were not inactivated under commercial kilning conditions that use temperatures as high as 85 degrees C but that some actually increased during the final kilning step. Qualitative (2-D, IEF x PAGE) analyses, which allow the study of individual proteases, showed that some of the enzymes were affected by heating at 68 and 85 degrees C, during the final stages of kilning. These changes obviously did not, however, decrease the overall proteolytic activity.     

Effect of selected herbicides on yielding and malting quality of spring barley cultivars

The aim of the study was to determine the effect of herbicides on yields, yield components and malting quality of the grains of barley cultivars. Literature worldwide lacks works on the impact of herbicides on the brewing quality of barley. This work presents the results of field experiments and laboratory studies concerning the evaluation of the impact of herbicides, differing in terms of an active substance, on the yields, weed control and malting quality of selected cultivars of barley. The research was conducted in Poland. The herbicides affected the increase in grain yields of barley, due to their high effectiveness of weed control, resulting in an increase in the number of ears per area unit. Certain herbicides increased grain protein content and grain filling. As for malt extractivity, Kolbach index, Q index, diastatic power and beta-glucans content in wort, there were interactions between herbicides and cultivars. The impact of herbicides on parameters varied depending on cultivars. The herbicides, especially Chwastox Turbo 340 SL (MCPA?+?dicamba) and Secator 125 OD (amidosulfuron?+?iodosulfuron-methyl-sodium), worsened several (not many) malt quality parameters, depending on cultivars, but it did not contribute to disqualifying malting quality of grains. Therefore, all tested herbicides can be recommended for use by farmers.     

Effect of modification of the kilning regimen on levels of free ferulic acid and antioxidant activity in malt

Barley phenolic antioxidants change in response to the kilning regimen used to prepare malt. Green malt was kilned using four different regimens. There were no major differences among the finished malts in parameters routinely used by the malting industry, including, moisture, color, and diastatic activity. Ferulic acid esterase activity and free ferulic acid were higher in malts subjected to the coolest kilning regimen, but malt ethyl acetate extracts (containing ferulic acid) contributed only ～5% of the total malt antioxidant activity. Finished malt from the hottest kilning regimen possessed the highest antioxidant activity, attributed to higher levels of Maillard reaction products. Modifying kilning conditions leads to changes in release of bound ferulic acid and antioxidant activity with potential beneficial effects on flavor stability in malt and beer.     

Oxygen deficiency in barley (Hordeum vulgare) grain during malting

The steep water is generally aerated in industrial barley malting. However, it is questionable whether oxygen actually reaches the embryo, which remains entrapped under the husk, testa, and pericarp until chitting occurs. The aim of our study was to investigate whether barley embryos experience oxygen deficiency during steeping, and whether various steeping conditions affect the oxygen deficiency. Alcohol dehydrogenase Adh2 was induced in all steeping conditions studied. Therefore, oxygen deficiency occurred regardless of the steeping conditions. However, steeping conditions affected the rate of recovery from oxygen deficiency, germination rate, and onset of alpha-amylase production. When barley was subjected to oxygen deficiency by applying N(2) gas during steeping, the timing of the treatment determined its effects. The importance of aeration increased as the process proceeded. Oxygen deprivation at the beginning of the process had little effect on malt quality. Therefore, the timing of aeration is important in the optimization of germination during the steeping stage of malting.     

采后褪黑素处理对鲜切花椰菜保鲜品质及货架期的影响

为研究采后外源性褪黑素处理对鲜切花椰菜货架期间品质及生理的影响,试验以\     

Prevention of oxidative rancidity in rice bran during storage.

The effect of microwave heat on lipoxygenase (LOX) activity in rice bran under various storage conditions was examined. Raw rice bran from the long-grain variety Lemont was adjusted to 21% moisture content and heated in a microwave oven at 850 W for 3 min. Raw and microwave-heated rice bran samples were packed in zipper-top bags or vacuum packs and stored at room temperature (25 degrees C) or in the refrigerator (4-5 degrees C) for 16 weeks. Samples were analyzed for LOX activity at 4-week intervals. LOX activity did not significantly change from its initial value at week 0 for zipper-top and vacuum-packed samples while stored at 4-5 degrees C for 12 weeks, but decreased at week 16. Vacuum packing did not show a significant impact on LOX activity during 16 weeks of storage. Microwave-heated samples stored in the refrigerator did not show significant change in LOX activity for up to 12 weeks but showed a significant (p < 0. 05) decrease at 16 weeks. Results showed that oxidative rancidity of rice bran could be prevented by microwave heating the samples, packing in zipper-top bags, and storing at 4-5 degrees C for up to 16 weeks.