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1.
Previous pilot brewing trials have demonstrated that in the absence of a molecular weight (MW) 12,000 (barley silica eluate (SE) protein), the beer brewed from the malt of these SE −ve varieties formed less haze after accelerated ageing than beers brewed using SE +ve malt varieties. The previously described SE protein was characterised using comparative two-dimensional (2-D) gel electrophoresis immunoblots of barley seed extracts from both SE +ve and SE −ve varieties. The SE protein spot identified was excised and its partial sequence determined, after in-gel cleavage using trypsin and separation of the resulting fragments by reversed-phase high performance liquid chromatography (HPLC). N-terminal sequence analysis of the tryptic peptides from SE +ve and SE −ve varieties identified the SE protein as the barley trypsin inhibitor-CMe precursor (BTI-CMe). The mature BTI-CMe protein is 13.3 kDa and its functional gene is located on chromosome 3H. Cloning of the BTI-CMe protein demonstrated that both SE −ve and SE +ve barley varieties contain a BTI-CMe protein family member that is similar but has a consistently different sequence, primarily in the last 30 amino acid residues of their C-termini.  相似文献   

2.
The influence of milled grain particle size on the kinetics of enzymatic starch digestion was examined. Two types of cereals (barley and sorghum) were ground, and the resulting grounds separated by size using sieving, with sizes ranging from 0.1 to 3 mm. In vitro enzymatic digestion was performed, using pancreatic alpha-amylase, amyloglucosidase and protease, to determine fractional-digestion rates over 24 h. The resulting glucose production rate data were well fitted by simple first-order kinetics. For each sieve screen size, the digestion rate of barley was always higher than that of sorghum. The rate coefficients for digestion showed a decrease with increasing size, and could be well fitted by an inverse square relationship. This is consistent with the supposition that starch digestion in these systems is controlled by diffusion of enzyme through the grain fragment. Apparent diffusion coefficients of alpha-amylase obtained by fitting the size dependence were 0.76 (sorghum) and 1.7 (barley) × 10−7 cm2 s−1, 9 (sorghum) and 4 (barley) times slower than predicted for a molecule of the size of alpha-amylase in water.  相似文献   

3.
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4.
The amount of (1 → 3),(1 → 4)-β-d glucan (β-glucan) accumulated in cell walls of barley (Hordeum vulgare L.) kernel is an important determinant for grain end-use. Grain β-glucan concentration is affected by environmental and genetic factors and usually varies from 3 to 6%. In this study, we have analyzed the β-glucan trait in a doubled-haploid (DH) population of 170 lines grown in three separate field trials. Most of the DH lines showed β-glucan values that ranged from that of the low β-glucan parent (cultivar CDC Bold; 3.3%) to that of the high β-glucan parent (breeding line TR251; 5.4%). Eighty-eight lines of the DH population were genotyped using simple sequence repeat (SSR), amplified fragment length polymorphism (AFLP) and diversity array technology (DArT) markers, which were subsequently integrated into a barley genetic map spanning 1059 cM. Interval mapping and multiple-QTL-mapping (MQM) of quantitative trait loci (QTL) from the three trials indicated seven genomic regions associated with low grain β-glucan concentration. For all putative QTLs, the low β-glucan concentration was contributed by alleles from CDC Bold except for two loci on chromosomes 5H that were derived from TR251. A major QTL located to the centromere region of chromosome 7H was identified by both mapping methods for all three trials. The 7H QTL explained up to 39% of the β-glucan concentration and genetic markers associated with the locus may be used to aid selection of high and low β-glucan barley lines.  相似文献   

5.
啤酒混浊是一个严重的品质问题,它显著缩短啤酒的贮藏与货架时间。为给生产低混浊啤酒大麦提供科学依据,本研究选用混浊特性不同的4个大麦品种,设置不同的氮肥用量与施用时期,探讨氮肥运筹对啤酒混浊性状的影响。结果发现,供试大麦品种之间和氮肥施用时期之间混浊性状差异极显著;澳大利亚大麦品种Franklin和Yerong的酒精冷混浊值(ACHD)显著低于国产大麦品种浙大9号和花30。Franklin的混浊敏感蛋白最低,花30次之,浙大9号和Yerong的混浊敏感蛋白含量较高。增施抽穗期氮肥,显著提高大麦的混浊度。不同氮肥用量之间,混浊敏感蛋白HAP1和HAP3差异极显著,但酒精冷混浊值和HAP2无显著差异;品种与氮肥用量及施用时期之间的互作效应对部分混浊性状表现显著。因此,为生产低混浊的啤酒大麦,生产上首先应考虑选用低混浊品种,并在氮肥施用上适当减少穗肥用量。  相似文献   

6.
The secondary structure of a dough-like zein polymer was compared to the structure present in a wheat viscoelastic system using FT-IR spectroscopy. When zein was mixed at 35 °C, which is above its glass transition temperature (Tg), changes in its secondary structure suggested that the protein loses its native structure, mainly composed of α-helices (68%), and a viscoelastic system is formed by a structural rearrangement that favors β-sheet structures. This rearrangement is very similar to the structural changes observed in gluten viscoelastic polymers. Upon removal of shear stress, the zein polymer showed a rapid decrease in the proportion of β-sheet structures (from 48% to 28% after the first 3 min) in favor of unordered structures. At the same time, the viscoelasticity of the polymer decreased rapidly. In contrast, gluten, in a similar viscoelastic system and held at the same temperature, showed a fairly constant high content of β-sheet structures (49%) coinciding with the slow relaxation time typical of gluten networks after the removal of shear. We speculate that the addition of a protein capable of causing extensive and stable β-sheet formation in the zein–starch viscoelastic polymer could increase the stability and relaxation time of the zein system and, thereby, create the possibility of a zein dough with similar functionality to a wheat viscoelastic system.  相似文献   

7.
The effect of gluten on the retrogradation of wheat starch   总被引：1，自引：0，他引：1  
The retrogradation of amylopectin in a wheat starch and a wheat starch/gluten (10:1) blend prepared by extrusion and containing 34% water (wet weight basis) was studied using X-ray diffraction, differential scanning calorimetry and NMR relaxometry during storage at constant water content and temperature (25 °C). For both samples, amylopectin ‘fully’ retrograded after 2–3 days storage, i.e. the different parameters monitored with time to follow the retrogradation had reached their maximum value, and crystallised predominantly into the A polymorph. Under the experimental conditions used, there was no evidence of any significant effects of the presence of gluten on the kinetics, extent or polymorphism of amylopectin retrogradation.  相似文献   

8.
The effects of moisture content (25–45% wwb) and temperature (75–120 °C) on the viscosity of gluten, soya and rennet casein systems was studied using a capillary rheometer. An attempt was made to relate the viscosities to the glass transition temperature measured by differential scanning calorimetry, dynamic mechanical thermal analysis and the phase transition analyzer. The temperature where the material flowed was also determined by the latter technique. All three-protein systems showed shear and extension thinning. Over the shear rate range investigated (1–103 s−1), gluten had a substantially lower viscosity than the other two proteins, although the difference was less pronounced at the highest temperature studied. This low viscosity is reflected by lower values of the glass transition temperature, the melt flow temperature and the dynamic moduli E′ and E″ in the rubbery state. The results are discussed in terms of the structure and heat induced changes for the three proteins and their relevance to food processing considered.  相似文献   

9.
The effects of modified atmosphere packaging (MAP) [bioriented polypropylene (BOPP-1 or BOPP-2)] in combination with antimicrobial agents Bacillus subtilis, 107 colony-forming units (cfu) ml−1; ethylenediamine tetraacetic acid, calcium disodium salt hydrate (EDTA) (0.1%); or 4-hexylresorcinol (4-HR) (0.15%) on postharvest decay control and quality retention of litchi cv. McLean's Red were assessed as possible replacements for commercial SO2 fumigation. Fruits dipped in B. subtilis, EDTA or 4-HR (5 min) separately, blow dried (25 °C, 3 min), packed in BOPP-1, held for 18 d at 2 °C, 95% RH, and 2 d at 14 °C, 75% RH were significantly less decayed. The antagonist–BOPP-1 combination also promoted the best bacterial survival during storage. B. subtilis was observed to survive effectively in BOPP-1 (16% O2, 6% CO2; 90% RH), but its survival was adversely affected in BOPP-2 (5% O2, 8% CO2; 93% RH). Alternaria alternata and Cladosporium spp. were the major decay-causing fungi in BOPP-1 treatments, and Candida, Cryptococcus and Zygosaccharomyces were the predominant yeasts in BOPP-2 treatments. Combination treatments EDTA, 4-HR or B. subtilis in BOPP-1 inhibited polyphenol oxidase (PPO) and significantly reduced pericarp browning and severity. Although the combination treatments EDTA, 4-HR or B. subtilis in BOPP were equally effective in controlling decay and browning, the EDTA and 4-HR affected the natural pinkish-red colour of the pericarp by showing higher h° values (orange–pink). Among the combination treatments, B. subtilis+BOPP-1 had the best potential to control decay, retain the colour and the overall litchi fruit quality during a marketing chain of 20 d.  相似文献   

10.
The aim of the present work was to study salt effect on the yield and composition of shoot essential oil (EO) and the structures responsible for its biosynthesis in Mentha pulegium L. Shoot EO was extracted by hydrodistillation and composition was determined by GC–MS method. Apical and basal leaves were taken for microscopy analyses; small fresh samples were observed directly without fixation or metallisation with environmental scanning electron microscope (ESEM) and stereomicroscope (SM). Fresh separate epidermis was used for light microscopy (LM). Salt stress enhanced EO yield by about 2.75 times and affected the percentage of menthone, which is the major compound (51%), increasing that of pulegone. Menthone, pulegone, and neomenthol constituting the monoterpene class were found to be the principal components. The anatomical study showed three types of trichomes: (i) non-glandular, multicellular, simple hairs; (ii) small, capitate glandular trichomes; (iii) and peltate glandular trichomes. In control plants, the density and size of trichomes varied with leaf side (abaxial or adaxial) and developmental stage. Salt stress results in significant modifications affecting trichome distribution and size on both sides.  相似文献   

11.
Using thermomechanical extrusion, waxy maize starch and 4% (w/w) lipid were formed into strips. The lipids used were free fatty acids (mostly linoleic) and antioxidant stripped sunflower oil (either previously oxidised or fresh, with and without copper ions). By altering their water content it was possible to store, at the same temperature, sample strips in the glassy and rubbery states. Lipid oxidation was monitored by determining hexanal in the headspace above all stored samples. The molecular weights of the amylopectin in the samples of extruded products (dissolved in dimethylsulfoxide, precipitated and redissolved using a pressure cell) were determined by asymmetric flow-field-flow fractionation, analytical ultracentrifugation and light scattering. The initial rate of hexanal generation was higher in samples stored in the glassy state compared with those in the rubbery state. Waxy maize and extruded samples, at the start of the storage period and after 42 days, were used to establish the molecular weight of the amylopectin. A significant fall (a decrease of 40%) in molecular weight was found on storage of samples containing sunflower oil and copper ions and those containing free fatty acids, irrespective of the method used for molecular weight determination.  相似文献   

12.
Hydroxycinnamate and protein contents and monosaccharide composition were determined for 11 industrial wheat (Triticum aestivum) brans and related to the susceptibility of their arabinoxylans (AX) to enzymatic degradation. There was significant variation in carbohydrate, A/X ratio, protein, hydroxycinnamic acid and diferulic acid (DiFA) content among the wheat brans. In addition, a strong correlation was found between AX and ferulic acid contents. Brans were extracted with water followed by a dry-thermal treatment to remove 90% starch and to inactivate endogenous enzymes and proteinaceous inhibitors. Treated brans were compared with respect to AX degradation by a family 11 xylanase. Digestion with xylanase had a strong impact on the chemical composition of the residual bran. The A/X ratio changed from 0.60 to 1.07. The solubilised AX had an A/X ratio of 0.32. The A/X ratio of enzyme-depleted bran was negatively correlated with the loss of AX. Total DiFA in destarched brans was negatively correlated with the amount of soluble AX. These relationships indicate that structural features of AX and the extent of its cross-linking in the cell walls of the bran tissues influence its susceptibility to xylanase treatment. Thus, the amount of enzyme-solubilised AX was not directly related to the content of AX in the destarched bran. However, brans differed in their susceptibility to xylanase attack.  相似文献   

13.
综述了目前国内外啤酒大麦麦芽品质性状的研究进展。内容包括 :麦芽品质性状的遗传模型和遗传力、配合力 ,影响麦芽品质性状的因素 ,麦芽品质性状间的相关性和相对重要性 ,当前麦芽品质性状研究上的不足之处。  相似文献   

14.
Tannin-containing sorghums, Chirimaugute and DC-75, and a tannin-free sorghum, SV2, were steeped in water, HCl (0·25 ), formaldehyde (0·017 ) and NaOH (0·075 ) for 8 and 24 h. Germination was carried out for 2 and 5 d. Steeping in NaOH enhanced water uptake of the grains compared with the other treatments. All treatments reduced the polyphenol content of the raw grain. Treatment with NaOH or formaldehyde (HCHO) was more effective than water or HCl. Malt quality was measured in terms of diastatic power (DP). Potential DP, determined after the peptone extraction, indicated higher amylase activity in DC-75 malt than in Chirimaugute and SV2 malt. Available DP, determined after water extraction, was low in malt from the tannin-containing varieties that had been treated with water or HCl. Malting alone was not an effective method of reducing the enzyme inhibitory power of the sorghum tannins. Available DP was markedly improved by the NaOH and HCHO treatments of the tannin-containing varieties. It is concluded that steeping in dilute NaOH is effective in detoxifying high-tannin sorghums, reducing the steeping period and enhancing malt quality. Steeping in NaOH appears to be a safer alternative to HCHO for treatment of high-tannin sorghums in the malting industry and for other food uses.  相似文献   

15.
A double antibody, sandwich enzyme-linked immunosorbent assay (ELISA) was developed using polyclonal antibodies specific tobeta-amylase to estimate the amount of ‘free’ (soluble in aqueous saline solution) or ‘combined’ (extracted with saline solution including reducing agent)beta-amylase protein in barley grain and malt. This ELISA was used to quantify the amount ofbeta-amylase in barley grain and malt from four varieties grown at nine sites in South Australia in 1993. The antibody used to develop the ELISA reacted differently withbeta-amylase depending on whether the source was barley grain or malt, and on thebeta-amylase band pattern in isoelectric focussing (IEF) of the barley variety. On the basis of their IEF band patterns barley varieties were divided into two types, designatedBmy1-Sd1 andBmy1-Sd2. Malting resulted in proteolytic cleavage of thebeta-amylase peptide with a reduction in the apparent molecular weight of up toMr4000 and the appearance of new maltbeta-amylase IEF bands that were more basic. The new maltbeta-amylase IEF band patterns still allowed the identification of theBmy1-Sd1 andBmy1-Sd2 IEF types despite the change in molecular weight and pI. The data obtained using thebeta-amylase ELISA were highly correlated withbeta-amylase activity for both the free and combined fractions when the IEF band pattern and its source, barley grain or malt, were taken into account.  相似文献   

16.
Improvement of malt quality is the most important objective in malt barley breeding. The current experiments investigated the variation of malt quality characters among barley genotypes and the difference in genetic variants of HvGlb1, encoding β-glucanase isoenzyme I, between Tibetan annual wild barley and cultivated barley. The correlation between the gene variants and malt quality showed that there was a large difference in the four malt quality parameters, i.e. Kolbach index, diastatic power (DP), viscosity and malt extract, among the analyzed barley cultivars. Kolbach index was negatively and positively correlated with viscosity and malt extract, respectively, while malt extract was negatively correlated with viscosity. Malt β-glucan content was a major determinant of malt quality, and was significantly correlated with Kolbach index (−0.633), malt extract (−0.333) and viscosity (0.672). On the other hand, malt β-glucan content was mainly controlled by malt β-glucanase activity. The correlation analysis showed that the HvGlb1 gene was correlated with malt β-glucan content and three of four main malt quality parameters, except DP. In addition, we also found that the HvGlb1 of Tibetan barley had wider diversity in haplotype than that of the cultivated barley, supporting the hypothesis that Tibet is one of the original centers of cultivated barley.  相似文献   

17.
Proteins in unmalted and malted barley and in brewers’ spent grain (BSG) obtained after mashing were fractionated on the basis of their differential extractability in different media and characterised by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and high-performance liquid chromatography (HPLC). Albumins and globulins were first extracted with 5.0% NaCl and hordeins (barley prolamins) were extracted with 55.0% 1-propanol in the presence, or absence, of 1.0% DTT. Glutelins were then extracted with 2.0% SDS/6.0 M urea/1.0% DTT or with 55.0% 1-propanol/6.0 M urea/1.0% DTT/0.036 M Tris-HCl (pH 8.4). Under non-reducing conditions, monomeric C hordeins and some B hordeins were extracted from unmalted barley, whereas most if not all B, C and D hordeins were extracted under reducing conditions. During malting, disulfide bonds are reduced and B and D hordeins are broken down by proteolysis. No D hordeins were extracted from malt and nearly the same levels of malt B hordeins were extracted both under non-reducing and reducing conditions. B hordeins present in BSG proteins were only extractable under reducing conditions. Whereas most of the C hordeins were extracted from BSG under non-reducing conditions, more C hordeins were extracted under reducing conditions. Mashing probably induced disulfide bond formation resulting in aggregation. Although earlier literature suggested the formation of an aggregate composed of B and D hordein (and glutelin) during mashing, the present work suggests the formation of an aggregate composed of B hordeins in which C hordeins are entrapped.  相似文献   

18.
Eight field experiments were conducted at four sites in the UK in 2003 and 2004 to investigate the effects of sulphur (S) application on yield and malting quality of barley. Significant yield responses to S additions were obtained in five out of the eight experiments, with yield increases ranging from 0.2 to 1.2 t/ha (4.7–22.5%). At the two most S-deficient sites, S application significantly increased malt diastatic power, alpha-amylase activity, friability and homogeneity, and decreased (1→3,1→4)-β-glucan concentration in the wort, indicating an improved endosperm modification during malting. Sulphur applications also significantly increased the concentration of S-methylmethionine (the precursor of dimethylsulphide) in kilned malt, which could impact on beer flavour. When the supply of N was limiting, S applications decreased grain N concentration due to a dilution effect as a result of increased grain yield. In some cases, S applications resulted in decreased grain size. At sites non-deficient or marginally deficient in S, applications of S had little effect on grain or malting quality parameters. The need to maintain an adequate S supply to barley for both yield and malting quality was demonstrated.  相似文献   

19.
Proteolytic degradation of barley proteins is examined in green (unkilned) malt and germinating seeds from Hordeum vulgare L. cv. Harrington. Zymographic analysis of the Harrington green malt extracts using commercial preparations of barley beta-amylase incorporated as a proteolytic substrate in 2-D SDS gels shows multiple proteolytic activities. A developmental study shows that the several green malt beta-amylase-degrading activities appear at around day 2 of germination. The several activities appear to increase and decrease through 7 days of germination in a coordinated fashion. Gels treated with class-specific proteinase inhibitors show that serine-class proteinase activities are responsible for barley beta-amylase degradation seen on the zymograms. Western blot analysis also shows that proteolytic enzymes recovered from 1-D electrophoretic gels degrade barley beta-amylase, and that the degradation is inhibited by PMSF. This is the first demonstration that malt proteinases are capable of degrading important metabolic enzymes in germinating barley, and the first postulated physiological role for the serine class proteinases in barley malt.  相似文献   

20.
Many analytical methods for antioxidant determination in foodstuffs and raw materials based on various principles have been published so far. However, not all of them are applicable to barley and malt. The results of total antioxidant capacity (TEAC) of barley and malt obtained with methods based on ability to eliminate radicals of 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) and 2,2-diphenyl-1-(2,4,6-trinitrophenyl) hydrazyl (DPPH) were compared and statistically evaluated. The average TEAC of barley determined using ABTS and DPPH ranged from 2.1 to 2.5 μmol g−1 and from 1.2 to 1.7 μmol g−1, respectively. The TEAC ranges in malt were 2.7–3.0 μmol g−1 (ABTS) and 1.8–2.6 μmol g−1 (DPPH). TEAC of barley and malt were affected by the weather conditions (year), variety and application of Zn2+ fertilizer. The ABTS and the DPPH methods represent an effective tool for the assessment of antioxidant capacity of spring barley and malt and the factors having an impact on it.  相似文献   

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