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.     

Oxidative degradation of bisphenol a by crude enzyme prepared from potato

When crude enzymes prepared from some vegetables and fruits were incubated with bisphenol A (2,2-bis(4-hydroxyphenyl)propane, BPA) at 37 degrees C, BPA was oxidized by crude enzymes from potato, eggplant, and lettuce. The crude enzyme prepared from potato (Solanum tuberosum) had the strongest oxidative activity for BPA. Its optimal temperature and pH were 40-45 degrees C and 8.0, respectively. More than 95% of BPA was oxidized after the incubation with potato enzyme for 60 min. BPA gave two oxidation products besides insoluble compounds during the oxidation by potato enzyme. The oxidation products were identified to be 4[1-(4-hydroxyphenyl)-1-methyl-ethyl]-benzene-1,2-diol and 4[1-(4-hydroxyphenyl)-1-methyl-ethyl]-benzene-1,3-diol. Enzymatically oxidized BPA lost the estrogen-like activity to enhance the growth of human breast cancer (MCF-7) cells.     

Effect of germination temperatures on proteolysis of the gluten-free grains sorghum and millet during malting and mashing

Our study showed that sorghum and millet followed a similar pattern of changes when they were malted under similar conditions. When the malt from these cereals was mashed, both cereal types produced wide spectra of substrates (sugars and amino acids) that are required for yeast fermentation when malted at either lower or higher temperatures. At the germination temperatures of 20, 25, and 30 °C used in malting both cereal types, production of reducing sugars and that of free amino nitrogen (FAN) were similar. This is an important quality attribute for both cereals because it implies that variation in temperature during the malting of sorghum and millet, especially when malting temperature is difficult to control, and also reflecting temperature variations, experienced in different countries, will not have an adverse effect on the production and release of amino acids and sugars required by yeast during fermentation. Such consistency in the availability of yeast food (substrates) for metabolism during fermentation when sorghum and millet are malted at various temperatures is likely to reduce processing issues when their malts are used for brewing. Although sorghum has gained wide application in the brewing industry, and has been used extensively in brewing gluten-free beer on industrial scale, this is not the case with millet. The work described here provides novel information regarding the potential of millet for brewing. When both cereals were malted, the results obtained for millet in this study followed patterns similar to those of sorghum. This suggests that millet, in terms of sugars and amino acids, can play a role similar to that of sorghum in the brewing industry. This further suggests that millet, like sorghum, would be a good raw material for brewing gluten-free beer. Inclusion of millet as a brewing raw material will increase the availability of suitable materials (raw material sustainability) for use in the production of gluten-free beer, beverages, and other products. The availability of wider range of raw materials will not only help to reduce costs of beer production, but by extension, the benefit of reduced cost of production can be gained by consumers of gluten-free beer as the product would be cheaper and more widely available.     

Modification of the levels of polyphenols in wort and beer by addition of hexamethylenetetramine or sulfite during mashing.

The effects of addition of hexamethylenetetramine (HMT) or sulfite during mashing on the polyphenol content and oxidative stability of wort and beer have been evaluated in a series of laboratory mashings and pilot brews. HMT reduced the concentration of catechin, prodelphinidin B-3, and procyanidin B-3 in wort and beer, whereas the concentration of ferulic acid was unaffected. Sulfite had only a minor effect on the concentration of phenolics in wort and beer. Addition of HMT or sulfite during mashing increased the oxidative stability of the beer slightly as judged by the tendency of formation of radicals (ESR spin trapping technique), although sensory analysis gave identical flavor acceptance scores to beers produced from untreated and HMT-treated wort and lower scores to beer from sulfite-treated wort. No difference in the oxidative stability of the differently treated sweet worts could be detected as judged by the rate of formation of radicals. HMT addition during mashing has thus been demonstrated to be a valuable experimental tool to control the level of polyphenols in wort and for producing brews with various levels of polyphenols from a single malt.     

Oxidative degradation of triazine derivatives in aqueous medium: a radiation and photochemical study

Pulse and steady state radiolysis techniques have been used to determine the bimolecular rate constants and to investigate the spectral nature of the intermediates and the degradation induced by hydroxyl radicals ((*)OH) with 1,3,5-triazine (T), 2,4, 6-trimethoxy-1,3,5-triazine (TMT), and 2,4-dioxohexahydro-1,3, 5-triazine (DHT) in aqueous medium. A competitive kinetic method with KSCN as the (*)OH scavenger was used to determine the rate constants for the reaction of (*)OH with T, TMT, and DHT. The bimolecular rate constants are 3.4 x 10(9), 2.06 x 10(8), and 1.61 x 10(9) dm(3) mol(-)(1) s(-)(1) respectively, for T, TMT, and DHT at pH approximately 6. The transient absorption spectra obtained from the reaction of (*)OH with T, TMT, and DHT have single absorption maxima at 320, 300, and 300 nm, respectively, and were found to undergo a second-order decay. The formation of TOH(*) [C(6)OH-N(5)-yl radical], TMTOH(*) [N(5)OH-C(6)-yl radical], and DHT(*) [C(6)-yl radical] is proposed from the initial attack of (*)OH with T, TMT, and DHT, respectively. A complete degradation of TMT (10(-3) mol dm(-3)) was obtained after absorbed doses of 5 kGy in N(2)O-saturated solutions and 16 kGy in aerated solutions. A similar degradation pattern was obtained with DHT in N(2)O-saturated solutions. Complete degradation was observed with an absorbed dose of 7 kGy. On the basis of the results from both pulse and steady state radiolysis, a possible reaction mechanism involving (*)OH-mediated oxidative degradation is proposed. A complete photodecomposition of DHT was also observed in the presence of ferric perchlorate using ultraviolet light at low pH. Photoinduced electron transfer between Fe(III) and DHT in the Fe(III)-DHT complex and subsequent formation of DHT(*) are proposed to be the major processes that lead to the complete degradation of DHT at pH 3.     

Microbial degradation of phyllosilicates during simulated podzolization

Perfusion experiments were conducted to study mechanisms in the transformation of phyllosilicates by oxalic acid and other complexing agents synthesized by microorganisms that survived partial sterilization. Those resistant to thymol were mostly non-pigmented Pseudomonas sp. and Bacillus but included a few yeasts. The organic acids formed by the microorganisms dissolved large amounts of mineral elements from samples of granites and granitic sand. Organo-metal complexes were formed with Fe and Al. 70–100% of the dissolved Fe were in complexes stable over a wide range in pH. 10–30% of the dissolved Fe and Al were in very stable anionic complexes that were not exchangeable with strong cationic resins. The acidic compounds that were formed solubilized appreciable amounts of ferromagnesian minerals, mainly biotite, and destroyed primary chlorite and some vermiculite. Under some experimental conditions, illite-vermiculite was transformed into vermiculite and biotite into vermiculite or into a white and brittle residue of Si and Al. Because similar mineral transformations have been shown to occur during podzolization in the field, our experiments are thought to provide a satisfactory model of weathering in that soil-forming process.     

GC-ITMS determination and degradation of captan during winemaking

Captan and its metabolite tetrahydrophthalimide (THPI) were determined in grapes, must, and wine by GC-ITMS. Pesticides were extracted with acetone/petroleum ether (50:50 v/v). Because of the high selectivity of the ITMS detector, no interferent was found and cleanup was not necessary. Recoveries from fortified grapes, must, and wines ranged between 90 and 113% with a maximum coefficient of variation of 11%. Limits of quantitation were 0.01 mg/kg for both compounds. In model systems, captan and its metabolites, THPI, cis-4-cyclohexene-1,2-dicarboxylic acid, and 1,2,3,6-tetrahydrophthalamic acid, were determined by HPLC. The degradation of captan during winemaking was studied. Captan degraded in must, giving 100% THPI, and at the end of fermentation, only THPI was found in wine. The degradation of captan to THPI was due to the acidity in must and wine. This metabolite was present at low levels on grapes, and, unlike captan, it had no negative effect on the fermentative process. Model systems showed that the mechanism of disappearance of captan in grapes was due to photodegradation and codistillation.     

Impact of mashing on sorghum proteins and its relationship to ethanol fermentation

Nine grain sorghum cultivars with a broad range of ethanol fermentation efficiencies were selected to characterize the changes in sorghum protein in digestibility, solubility, and microstructure during mashing and to relate those changes to ethanol fermentation quality of sorghum. Mashing reduced in vitro protein digestibility considerably, and a large amount of polymers cross-linked by disulfide bonds were developed during mashing. As a marker of cross-linking, protein digestibility of the original samples was highly related to conversion efficiency. gamma-Kafirin (%) neither correlated to ethanol yield nor conversion efficiency significantly. Solubility of proteins in an alkaline borate buffer in conjunction with SDS decreased substantially after mashing. Solubility and the SE-HPLC area of proteins extracted from mashed samples were highly correlated with ethanol fermentation. Ethanol yield increased and conversion efficiency improved notably with the increase of extracted proteins from mashed samples. SE-HPLC total area could be used as an indicator to predict ethanol fermentation. CFLSM images proved that sorghum proteins tended to form highly extended, strong web-like microstructures during mashing. The degree of protein cross-linking differed among samples, and more open microstructures were observed in samples with higher conversion efficiencies. The web-like protein matrix was found to hold not only starch granules but also some oligosaccharides or polysaccharides inside. The formation of web-like microstructures because of cross-linking reduced conversion efficiency.     

Kinetics of maneb degradation during thermal treatment of tomatoes

The kinetics of maneb degradation in tomato homogenates at high temperatures and at two pH values (4 and 9) and the rate of formation of the toxic metabolite, ethylenethiourea (ETU), were studied. Maneb was measured as carbon disulfide by headspace gas-chromatography and ETU by high-performance liquid chromatography with photodiode array detection. First-order kinetics adequately described the degradation of maneb in tomato homogenates. The degradation rate constants exhibited an Arrhenius temperature dependence in the range from 50 to 90 degrees C and the apparent activation energy (E(a)) was calculated to be 36 KJ mol(-1) in homogenates with natural pH (4). Raising temperature from 60 to 75 and to 90 degrees C, ETU formation was significantly increased. Interestingly, the selectivity toward ETU showed a downward trend when the total conversion increased at longer heating times. When the pH of the tomato homogenates was adjusted to 9, the degradation of maneb proceeded faster at both 60 and 90 degrees C. The combination of alkaline pH and the highest temperature (90 degrees C) resulted in the maximum ETU conversion rates. The results of the present study on the fate of maneb and ETU residues during tomato processing, may prove valuable in estimating potential risk from dietary exposure.     

Release of lipids during yeast autolysis in a model wine system

The release of lipids during the aging of sparkling wines in contact with yeast can influence wine sensory attributes and, especially, foam characteristics. Model systems allow study of the autolysis process in a reasonable period of time compared to natural conditions, at which it can last several months. In this paper, the release of the different classes of lipids during the autolysis of three commercial yeast strains in a model wine medium has been monitored. Due to the absence of accurate quantitative methods, an HPLC method for separating and quantifying the different neutral and polar yeast lipid classes was developed. Lipids were eluted through a YMC PVA-Sil column with a complex solvent mixture. Detection was carried out with a light-scattering detector. The yeasts were suspended in the model wine buffer and incubated at 30 degrees C for up to 12 days. A release of triacylglycerols, 1,3-diacylglycerols, 2-monoacylglycerols, free fatty acids, sterol esters, and sterols was observed over the first 2 days, a period that corresponded to the maximum loss of yeast viability. A decrease in most of these lipids was observed from day 2, possibly indicative of the release of yeast hydrolytic enzymes due to the breakdown of the cell wall. Phospholipids were not detected in any of the autolysates. The mean lipid content in the autolysates as a percentage of the total lipid content in the yeasts was 8.6% for sterol esters, 3.8% for sterols, 2% for triacylglycerols, and <2% for 1,3-diacylglycerols and free fatty acids.     

鸡肉在成熟过程中肌原纤维蛋白的降解机制研究

为了探讨肉在成熟过程中肌原纤维蛋白的降解机制,五只肉鸡分别宰杀后,迅速取出胸肉约3 g为0 d样品,其余肉样剪碎后随机分成六组,一组作为对照,另5组分别用30 mmol/L EGTA、20 mmol/L CaCl2、酶复合抑制剂、100μmol/L细胞凋亡酶3抑制剂（DEVD-CHO）、20 mmol/L CaCl2和酶复合抑制剂处理,在4℃成熟1、3、7 d后取样。通过SDS-PAGE和蛋白质印迹分析测定了骨骼肌中和肉嫩度高度相关的拌肌球蛋白（titin）、伴肌动蛋白（nebulin）、肌间线蛋白（desmin）、肌钙蛋白T（troponin-T）的降解变化。结果显示蛋白水解酶复合抑制剂和DEVD-CHO抑制了蛋白的降解,单独的钙离子加速蛋白降解。这表明肉的成熟是内源酶的作用,钙离子很可能通过激活钙激活酶发挥作用,另外细胞凋亡酶3也很可能参与了肉的成熟。     

漂洗和斩拌对海鲈鱼肌球蛋白理化特性的影响

为探究漂洗和斩拌对海鲈鱼肌球蛋白理化特性的影响,分别提取原料、漂洗鱼糜、斩拌鱼糜的肌球蛋白,通过测定总巯基、活性巯基、表面疏水性、浊度等基本性质,并结合红外光谱和原子力显微镜(atomic force microscope,AFM)技术对肌球蛋白二级结构和表面形貌进行研究。结果表明:相比原料,漂洗鱼糜肌球蛋白总巯基含量降低19.5%,活性巯基增大63.9%,而斩拌鱼糜肌球蛋白总巯基和活性巯基的质量分数相比漂洗鱼糜分别降低22.6%和66.8%,漂洗鱼糜的肌球蛋白变性程度最大;肌球蛋白浊度和表面疏水性在经过漂洗和斩拌均增大,漂洗对表面疏水性影响更大,斩拌对浊度影响更大;红外光谱研究结果显示,漂洗对二级结构影响更明显,原料经过漂洗后,α-螺旋相对含量降低了33.16%,无规则卷曲相对含量增加了79.42%,β-折叠和β-转角分别增加1.11%和10.38%,斩拌后,鱼糜肌球蛋白二级结构变化率较低;漂洗和斩拌都可改变肌球蛋白的表面形貌,使肌球蛋白聚集簇明显减小,聚集高度增加。研究结果证明,漂洗和斩拌对肌球蛋白理化特性有很大的影响,是鱼糜具有更好的凝胶性能的重要步骤。     

Identification of protein degradation during post-mortem storage of pig meat

Eighteen proteins and peptides that were found to change post-mortem in Longissimus dorsi from pig muscle were identified by the use of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The 18 peptides originate from 9 different proteins including the 3 structural proteins (actin, myosin heavy chain, and troponin T) and the 6 metabolic proteins glycogen phosphorylase, creatine kinase, phosphopyruvate hydratase, myokinase, pyruvate kinase, and dihydrolipoamide succinyltransferase. The molecular weight and estimated sequence length of the identified spots show that these fragments result from proteolytic activity in meat. Identification of the parent proteins and the enhanced post-mortem appearance of the degradation products make these specific peptides good candidates for meat quality markers, and further studies of these specific fragments will lead to a better understanding of the proteolytic activities involved in the post-mortem conversion of muscle to meat.     

Olive fruit cell wall: degradation of pectic polysaccharides during ripening

Olive fruits at three stages of ripening (green, cherry, and black) have been studied. After cell wall isolation, the compositions of the cell wall and that of the phosphate-soluble polysaccharides were determined. In cell walls, decreases in arabinose, xylose, glucose, and uronic acid levels were observed, together with a slight increase in mannose on ripening. At the beginning of ripening, fragments of pectic polymers were the major constituents of the phosphate-soluble fraction, with the hemicellulosic ones increasing toward the end of the process. The molecular weight of the fragments solubilized was approximately 6 kDa. After cell wall fractionation, the pectic polysaccharides soluble in imidazole and sodium carbonate were also studied. In both fractions, between the green and cherry stages of ripening, a significant loss of homogalacturonans took place. Between the cherry and black stages of ripening, rhamnogalacturonan side chains were also released in addition to homogalacturonans. In any of the pectic fractions, changes in apparent molecular weight were quantified.     

Thermal degradation products formed from carotenoids during a heat-induced degradation process of paprika oleoresins (Capsicum annuum L.)

The high-temperature treatment of paprika oleoresins (Capsicum annuum L.) modified the carotenoid profile, yielding several degradation products, which were analyzed by HPLC-APCI-MS. From the initial MS data, compounds were grouped in two sets. Set 1 grouped compounds with m/z 495, and set 2 included compounds with m/z 479, in both cases for the protonated molecular mass. Two compounds of the first set were tentatively identified as 9,10,11,12,13,14,19,20-octanor-capsorubin (compound II) and 9,10,11,12,13,14,19,20-octanor-5,6-epoxide-capsanthin (compound IV), after isolation by semipreparative HPLC and analysis by EI-MS. Compounds VII, VIII, and IX from set 2 were assigned as 9,10,11,12,13,14,19,20-octanor-capsanthin and isomers, respectively. As these compounds were the major products formed in the thermal process, it was possible to apply derivatization techniques (hydrogenation and silylation) to analyze them by EI-MS, before and after chemical derivatization. Taking into account structures of the degradation products, the cyclization of polyolefins could be considered as the general reaction pathway in thermally induced reactions, yielding in the present study xylene as byproduct and the corresponding nor-carotenoids.     

土地退化/恢复中土壤可蚀性动态变化

利用EPIC公式计算了不同开垦和退耕年限的土壤可蚀性K值,对黄土高原典型自然恢复区子午岭林区土地退化/恢复过程中土壤可蚀性的动态变化进行了系统的研究。结果表明：土地开垦后,土壤颗粒向粗骨化方向发展,有机碳含量降低,土壤可蚀性逐渐增强;土地退耕过程中,土壤有机碳含量逐渐增加,肥力水平提高,可蚀性逐渐减小;土壤中有机碳含量、全氮含量、水稳性团聚体含量以及团聚度与土壤可蚀性K值相关最为密切;土壤可蚀性的强弱本质上取决于土壤有机碳含量,恢复植被以提高土壤有机质含量,促进土壤团聚体的形成,增强土壤团聚度,是降低土壤可蚀性能的重要途径。     

Apolipoprotein E polymorphism and changes in serum lipids during a family-based counselling intervention

OBJECTIVE: To compare serum lipids and their changes during a family-based health education in children aged 6-17 years with or without the epsilon4 allele of the gene encoding apolipoprotein E (apoE). DESIGN: An intervention study. SETTING: A family-based prevention of risk factors of coronary heart disease in Eastern Finland. The programme consisted of two counselling meetings at children's schools and three at children's homes. SUBJECTS: Four hundred and thirty-nine children with a family history of cardiovascular diseases (CVD) participated in a family-based health education. The children were divided into two groups according to apoE genotype. The risk group consisted of 143 children having apoE epsilon4 allele (genotype epsilon3/4 or epsilon4/4) and the non-risk group of 296 children without apoE epsilon4 allele (epsilon2/3 or epsilon3/3). The final sample of the follow-up study included 354 (81%) children (114 and 240, respectively). RESULTS: Baseline differences were found in low-density lipoprotein cholesterol (LDL-C) (P=0.007) and LDL-C/high-density lipoprotein cholesterol (HDL-C) ratio (P=0.030) among boys and in total cholesterol (TC)/HDL-C (P=0.008) and LDL-C/HDL-C ratios (P=0.006) among girls. Differences between groups in changes during the follow-up were observed only for TC/HDL-C ratio (P-value adjusted for age=0.049) among boys. CONCLUSIONS: At baseline, children with apoE epsilon4 allele had on average a more unfavourable lipid profile than those without apoE epsilon4 allele. However, the effect of about 33 months' family-based health education on plasma lipids did not depend on apoE genotype in children with a family history of CVD.     

Wine distillery wastewater degradation. 1. Oxidative treatment using ozone and its effect on the wastewater biodegradability.

Laboratory-scale experiments were conducted to investigate the impact of ozonation on the degradability of wine distillery wastewaters, usually called vinasses, with the goal of developing combined chemical-biological methods for their treatment. Chemical oxygen demand (COD), biological oxygen demand (BOD), total organic carbon (TOC), and ultraviolet absorbance at 254 nm (UV(254)) were taken as reference parameters to follow the pollution level. The vinasses were treated both directly and after being mixed with domestic sewage. Ozonation of pure vinasses required high ozone doses to achieve a significant efficiency for removing the organic matter. Mixing vinasses with domestic sewage allowed higher degradation rates with ozone. Ozone was also demonstrated to be an appropriate oxidizing agent to improve vinasses's biodegradability and organic matter removal. A mathematical model of the ozonation kinetics based on the film theory concept is also presented.     

Starch degradation by alpha-amylase in tobacco leaves during the curing process

Tobacco (Nicotiana tabacum L.) leaf starch is degraded to sugars through curing (42°C/82.3% relative humidity/72 h). Total carbohydrate content remained almost constant, starch content decreased markedly, and soluble sugar content (mostly glucose) increased. α-Amylase and starch phosphorylase activities increased sixfold and threefold, respectively, whereas β-amylase activity was unaltered and isoamylase activity decreased. Increased α-amylase activity was accompanied by increased α-amylase protein levels. Although tobacco has four α-amylase gene members, only NtAMY1 mRNA levels increased. For other starch degradation genes, such as NtBAM1 and NtBMY2 (β-amylase), NtISO1 and NtISO2 (isoamylase) and NtGWD1 and NtGWD3 (glucan water dikinase), the mRNA levels remained unaltered during the first 48 h of curing. NtAMY1 expression was induced by osmotic stress but was unaffected by high temperature and/or injury stresses. Similarly, soluble sugar contents were largely increased by osmotic stress. This suggests that starch is degraded by α-amylase during curing and that α-amylase is coded by NtAMY1, induced by osmotic stress.