Effect of drying of figs (Ficus carica L.) on the contents of sugars, organic acids, and phenolic compounds

Fresh figs were subjected to two different drying processes: sun-drying and oven-drying. To assess their effect on the nutritional and health-related properties of figs, sugars, organic acids, single phenolics, total phenolics, and antioxidant activity were determined before and after processing. Samples were analyzed three times in a year, and phenolic compounds were determined using high-performance liquid chromatography coupled with mass spectrometry (HPLC-MS). In figs, monomer sugars predominate, which is important nutritional information, and the content of sugars as well as organic acids in fresh figs was lower than in dried fruits. However, the best sugar/organic acid ratio was measured after the sun-drying process. Analysis of individual phenolic compounds revealed a higher content of all phenolic groups determined after the oven-drying process, with the exception of cyanidin-3-O-rutinoside. Similarly, higher total phenolic content and antioxidant activity were detected after the drying process. With these results it can be concluded that the differences in analyzed compounds in fresh and dried figs are significant. The differences between the sun-dried and oven-dried fruits were determined in organic acids, sugars, chlorogenic acid, catechin, epicatechin, kaempferol-3-O-glucoside, luteolin-8-C-glucoside, and total phenolic contents. The results indicate that properly dried figs can be used as a good source of phenolic compounds.     

The influence of early yield on the accumulation of major taste and health-related compounds in black and red currant cultivars (Ribes spp.)

The focus of our study was to investigate the effect of crop load on the accumulation and composition of primary metabolites (sugars and organic acids), selected groups of flavonoids (anthocyanins and flavonols), and total phenolics in two subsequent years in four black currant cultivars ('Titania', 'Triton', 'Tsema', and 'Cacanska crna') and three red currant cultivars ('Junifer', 'Rolan', and 'Stanza'). For the determination and quantification of compounds, high-performance liquid chromatography-photodiode array with a mass spectrometer was used. Significant differences among cultivars were detected in all analyzed compounds. Anthocyanins were the predominant phenolic group and were more abundant in black currant cultivars as compared to red ones. Similar amounts of sugars and organic acids were measured in both Ribes species; however, vitamin C was 3-fold higher in black currants. A larger crop load in the second year had a negative effect on the sugar content of berries and promoted a higher degree of acids, with the exception of vitamin C, which was higher in the year with a lower crop load. On the other hand, the content of anthocyanins and flavonols was higher in the year with a larger crop load, while there were no differences in total phenolic content.     

作物残茬翻埋对土壤性质的影响

Chemical transformation, nutrient release and changes in the energy content of decomposing rape, sunflower and soybean residues confined in buried fiberglass bags were assessed in a laboratory study during a 340-day incubation period. The organic C decreased by about 70% while total N, after initial decay, remained almost constant for each type of residue. The NH₄⁺-N was progressively oxidized and, consequently, the NO₃^--N increased. The C/N ratio narrowed with loss of C. Hemicellulose, cellulose and lignin decreased with different trends for each crop residue. The energy content, was reduced to about 25% in rape, 30% in sunflower and 20% in soybean residues. Total P, K, Ca and Mg contents decreased for each type of residue. The results suggest that the three residues could improve the nutrient pool of the soil.     

Changes in the volatile compounds and chemical and physical properties of Kuerle fragrant pear (Pyrus serotina Reld) during storage

Volatiles from stored Kuerle fragrant pears (Pyrus serotina Reld) were studied using high-resolution gas chromatography and the solid-phase microextraction (SPME) method of gas chromatography/mass spectrometry (GC/MS). The dominant components were hexanal, ethyl hexanoate, ethyl butanoate, ethyl acetate, hexyl acetate, ethanol, alpha-farnesene, butyl acetate, and ethyl (E,Z)-2,4-decadienoate. By using GC-olfactometry, it demonstrated that the volatile compounds from SPME were responsible for the aroma of the Kuerle fragrant pear. The levels of sugars, organic acids, and phenolic acids in Kuerle fragrant pears were investigated using high-performance liquid chromatography (HPLC). Fructose was the dominant sugar, followed by glucose and sucrose. With increasing storage time, sucrose levels decreased; however, changes in fructose and glucose levels were not remarkable. There was a slight decrease in flesh firmness during storage. The general soluble solids concentration (SSC) declined slightly after 5 months storage. Some aroma-related volatile components increased during storage, while others decreased, especially the esters. The organic acids and phenolic acids also changed. The flavor of the Kuerle fragrant pears was affected by the change of volatile compounds and changes in chemical and physical properties.     

The microbial community composition changes rapidly in the early stages of decomposition of wheat residue

It is generally accepted that during the early stages of residue decomposition, easily available compounds are decomposed, leading to a relative increase in more recalcitrant compounds in the later stages of decomposition and that these changes in substrate availability are associated with changes in microbial community composition. However most studies on residue decomposition are conducted over several weeks or months; little is known about the changes in microbial community composition in the first weeks of decomposition. To address this knowledge gap, we incubated wheat residues inoculated with a microbial suspension in mesh bags buried in sand for 30 days, with sampling on days 0, 2, 4, 6, 8, 10, 15, 20, 25 and 30. Of the C added with the residues, 10, 18 and 25% had been respired on days 10, 20 and 30, respectively. The sum of PLFAs (phospholipid fatty acids), as an indicator of microbial biomass, increased strongly in the first 4 days and then decreased. The concentration of bacterial fatty acids was maximal on days 2 and 4, whereas the concentration of fungal fatty acids peaked on day 15. Microbial community composition (based on PLFA patterns) changed rapidly, with significant changes in the first 8 days and from day 8 to day 20. There were no significant changes in microbial community composition after day 20. The concentration of water-soluble C decreased strongly in the first 8 days, suggesting that the rapid changes in microbial community in this period are related to the changes in water-soluble C. Residue C chemistry, assessed by ¹³C NMR spectroscopy, changed little during the incubation period. This study showed that microbial community composition in decomposing residues changes rapidly in the first 1-2 weeks, which is, at least partly, the result of competition for the easily available compounds in the water-soluble fraction. After depletion of the water-soluble compounds, the microbial community composition changes more slowly.     

Evolution of Biochemical Parameters During Composting of Urban Wastes

An experiment was performed for evaluating the most suitable biochemical parameters to measure dynamics of substrate transformation during composting of the organic fraction derived from preselected urban wastes and wood bark mixture. Changes of chemical (organic C, hydrosoluble sugars, total and mineral N, humified fraction, volatile acids and phenolic compounds) and biochemical (microbial respiration, biomass C, qCO₂, dehydrogenase, catalase, urease activities, FDA, and BIF) parameters were monitored for 120 days. Limited changes in organic C, total nitrogen, and humification characteristics were observed during composting. Dehydrogenase and catalase activities, BIF and FDA showed small changes during composting. Urease activity and, with some limitations regarding the early stages of composting, microbial respiration and qCO₂, were found to be the most suitable parameters to measure dynamics of substrate transformation during composting of preselected urban wastes.     

Processes controlling the production of aromatic water-soluble organic matter during litter decomposition

Dissolved organic matter (DOM) plays a fundamental role for many soil processes. For instance, production, transport, and retention of DOM control properties and long-term storage of organic matter in mineral soils. Production of water-soluble compounds during the decomposition of plant litter is a major process providing DOM in soils. Herein, we examine processes causing the commonly observed increase in contribution of aromatic compounds to WSOM during litter decomposition, and unravel the relationship between lignin degradation and the production of aromatic WSOM. We analysed amounts and composition of water-soluble organic matter (WSOM) produced during 27 months of decomposition of leaves and needles (ash, beech, maple, spruce, pine). The contribution of aromatic compounds to WSOM, as indicated by the specific UV absorbance of WSOM, remained constant or increased during decomposition. However, the contribution of lignin-derived compounds to the total phenolic products of ¹³C-labelled tetramethylammonium hydroxide (¹³C-TMAH) thermochemolysis increased strongly (by >114%) within 27 months of decomposition. Simultaneous changes in contents of lignin phenols in solid litter residues (cupric oxide method as well as ¹³C-TMAH thermochemolysis) were comparably small (−39% to +21% within 27 months). This suggests that the increasing contribution of lignin-derived compounds to WSOM during decomposition does not reflect compositional changes of solid litter residues, but rather the course of decomposition processes. In the light of recently published findings, these processes include: (i) progressive oxidative alteration of lignin that results in increasing solubility of lignin, (ii) preferential degradation of soluble, non-lignin compounds that limits their contribution to WSOM during later phases of decomposition.     

Decomposition and nitrogen mineralization from legume and non-legume crop residues in a subarctic agricultural soil

An understanding of the C and N dynamics of crop residues is important for efficient nutrient management. The present experiment was conducted to determine the rate of mass and N loss from alfalfa, faba bean, barley, and rape crop residues in a subarctic agricultural soil. Mass, C, and N losses were measured from residues contained in mesh bags and placed on the soil surface or buried 15 cm below the surface. The mass loss from October, 1988, to May, 1989, was the same for surface and buried alfalfa, barley, and rape residues, averaging 40, 20, and 61%, respectively, while surface and buried faba bean residue sustained 30 and 40% mass loss, respectively. The mass loss of the buried residues continued over the summer but not of those placed on the soil surface, resulting in an average 23% greater mass loss of the buried materials after 1 year. The N loss from October to May was similar from the surface and from the buried placements for the alfalfa, faba bean, and rape residues, averaging 11.3, 10.3 and 38.4 g N kg^-1 residue, respectively, while the surface and buried barley lost 2.9 and 4.2 g N kg^-1, respectively. The C:N ratio of all of the residues increased during the winter. These data indicate that the rate of decomposition and N mineralization from crop residues in subarctic environments can equal that measured in temperate climates. Furthermore, the concurrent loss of mass and N combined with an increase in the C:N ratio of the residues suggests that physical rather than biological processes were functioning during the winter. Most of the mass and N loss from these residues occurred during the winter, out of phase with crop demand, thereby creating the potential for N loss from the system and inefficient use of crop residue N.     

Rates of decomposition and phosphorus release from organic residues related to residue composition

The use of organic residues might be appropriate in maintaining long‐term P requirement of crops. Eight plant residues and two manures in a wide range of C : N ratios were incubated for 12 weeks at 25°C, during which the processes of decomposition and formation of acid‐extractable P (P release) were assessed. Residues were incubated moist in bags and inoculated with a soil suspension. The exponential model was found to be suitable to describe decomposition and P‐release rates from residues. There were two distinct parts of P release in each time curve, which gave two rate constants and were calculated as the slope of each part. The rates of P release of the residues were considerably higher during the first 4 weeks of incubation than during the second phase of incubation (weeks 5–12). Phosphorus release by residues was similar to the decomposition pattern. The residue P content was correlated with P release, but not with decomposition rate. Mass loss and release of P were greater from sunflower and wheat residues than from sheep manure, suggesting that a high C : N ratio does not necessarily retard decomposition. The model parameters of P release were derived which are suitable to estimate the P‐fertilizer effect of organic residues. Our results suggest that the use of organic residues as a source for short‐ and long‐term P supply for crops should be encouraged.     

Soil Properties as Influenced by Incorporation of Crop Residues

Chemical transformation,nutrient release and changes in the energy content of decomposing rape,sunflower and soybean residues confined in buried fiberglass bage were assessed in a laboratory study during a 340-day incubation period.The organic C decreased by about 70% while total N,after initial decay,remained almost constant for each type of residue.The NH4^ -N was progressively oxidized and,consequently,the NO3^-N increased.The C/N ratio narrowed with loss of C.Hemicellulose,cellulose and lignin decreased with different trends for each crop residue.The energy content,was reduced to about 25% in rape,30% in sunflower and 20% in soybean residues.Total P,K,Ca and Mg contents decreased for each type of residue The results suggest that the three residues could imporve the nutrient pool of the soil.     

Fate of nitrogen from crop residues as affected by biochemical quality and the microbial biomass

Net mineralization of N from a range of shoot and root materials was determined over a period of 6 months following incorporation into a sandy-loam soil under controlled environment conditions. Biochemical “quality” components of the materials showed better correlation with net N mineralization than did gross measures of the respiration and N content of the soil microbial community during decomposition. The quality components controlling net N mineralization changed during decomposition, with water-soluble phenolic content significantly correlated with net N mineralization at early stages, and water-soluble N, followed by cellulose at later stages. C-to-N and total N were correlated with net N mineralization towards the end of the incubation only. Cumulative microbial respiration during the early stages of decomposition was correlated with net N mineralization measured after 2 months, at which time maximum net N mineralization was recorded for most residues. However, there was no relationship between microbial-N and net N mineralization. Biochemical quality factors controlling the C and N content of the residue remaining at the end of the incubation as light fraction organic matter (LFOM) were also investigated. Both C and N content of LFOM derived from the residues were correlated with residue cellulose content, and the chemical characteristics of LFOM were highly correlated with those of the original plant material. Incorporation of low cellulose, high water-soluble N-containing shoot residues resulted in more N becoming mineralized than had been added in the residues, demonstrating that net mineralization of native soil organic matter had occurred. Large amounts of N were lost from the mineral-N pool during the incubation, which could not be accounted for by microbial immobilization.     

Effect of sample preparation on the measurement of sugars, organic acids, and polyphenols in apple fruit by mid-infrared spectroscopy

The objectives of this study were (i) to test different conditions of freezing, thawing, and grinding during sample preparation and (ii) to evaluate the possibility of using mid-infrared spectroscopy for analyzing the composition of sugars, organic acids, and polyphenols in apples. Seven commercial apple cultivars were chosen for their large variability in composition (total polyphenols from 406 to 1033 mg kg(-1) fresh weight). The different conditions of sample preparation affected only the phenolic compounds and not sugars or organic acids. The regression models of the mid-infrared spectra showed a good ability to estimate sugar and organic acid contents (R(2) ≥ 0.96), except for citric acid. Good predictions were obtained for total phenolic, flavan-3-ols, and procyanidins (R(2) ≥ 0.94) provided oxidation was avoided during sample preparation. A rapid and simple procedure was then proposed for phenolic compounds using sodium fluoride during sample homogenization at ambient temperature and freeze-drying before spectra acquisition.     

Components of soil organic matter under grass and arable cropping

Components of the organic matter have been studied in three soils from adjacent sites with different long-term treatments: soil I, prolonged arable cultivation; soil II, 17 years under grass after prolonged arable cultivation; and soil III, old pasture. Contents of total organic C in the top 15cm were 0.9% in soil I. 1.7% in soil II and 4.8% in soil III. The light fraction, comprising partially decomposed materials with a specific gravity < 2.06, represented greater proportions of the organic C in soils II and III (20–23 per cent) than in soil I (8.5 per cent). The light fraction of soil III had a relatively high N content.The proportions of the soil organic C released, by hydrolysis, as neutral sugars, uronic acids, amino sugars, amino acids and phenolic acids were generally similar in the three soils, although uronic acids and phenolic acids constituted somewhat greater proportions in soils II and III than in I.The light fractions contained greater proportions of neutral sugars and phenolic acids, and smaller proportions of amino sugars and amino acids than the whole soils.     

添加水稻秸秆对油菜(Brassica napusL.)幼苗生长的影响

近几年,水稻秸秆直接还田对油菜幼苗生长的负效应受到关注。有许多研究在水稻残体或腐解物中检测出了酚酸等被广泛证实具有化感作用的物质,因此在水稻秸秆产生的负效应中,化感抑制作用不容忽视。本研究以酚酸为目标化感物质,以湖北省油菜主栽品种"中双11号"为受体,采用4种采自典型稻油轮作系统中的土壤进行盆栽试验,研究水稻秸秆对油菜幼苗生长的影响。结果表明:(1)整体看来,添加秸秆对油菜幼苗总生物量的主效应在进贤土为正,在汉川土为负,在阳逻和麻城土为无明显影响;(2)功能叶片光合色素含量在全部土壤下的显著降低均出现在播种后33 d之内,与水稻秸秆腐解速率最大值的出现与存在时间上的重叠。秸秆处理对油菜幼苗的负效应在早期强于后期;(3)土壤水溶态酚酸含量为3.3~49.0μg·g-1soil。添加秸秆虽导致土壤中水溶态酚酸浓度增加,但其明显增加主要发生在试验后期,且增量与幼苗生物量化感效应指数呈正相关关系。因此酚酸含量的变化不能解释水稻秸秆的负效应,为揭示秸秆处理的负效应机制,需要转换目标化感物质。     

植茶年限对土壤pH值、有机质与酚酸含量的影响

土壤pH值和有机质是土壤肥力的重要指标,土壤中的酚酸类物质也是一类重要的有机物质,与pH值和有机质关系复杂。本文以四川省名山区茶园土壤为对象,研究植茶年限对土壤pH值、有机质和酚酸含量的影响,并探讨它们之间的相互关系。结果显示:随着植茶年限的延长,各土层土壤的pH值均呈现不同程度的下降趋势,即植茶10年植茶7年植茶5年植茶3年水稻土,表层土壤酸化明显;随着植茶年限的延长,土壤有机质、总酚和水溶性酚含量均呈增加趋势。相关分析表明,0~10 cm土层土壤中,总酚与土壤pH值呈负相关;10~20和30~40 cm土层土壤中,水溶性酚与土壤pH值呈负相关;10~20 cm土层土壤中,总酚与土壤有机质呈正相关;在10~20、20~30和30~40 cm土层土壤中,水溶性酚与土壤有机质呈正相关。说明植茶土壤酚酸含量的增加是影响土壤pH值下降和有机质含量升高的重要因素。     

Effect of steam explosion treatment on barley bran phenolic compounds and antioxidant capacity

A steam explosion pretreatment process followed by methanol extraction has been applied for releasing and extracting phenolic compounds, as well as other effective components, from barley bran. The steam explosion treatment was performed at different temperatures ranging from 210 to 250 °C, with a residence time of 30 s. The effect of residence time was also studied in the range 10 s to 120 s at 220 °C. The extracts were evaluated for their total soluble phenolic content (TSPC) including total free phenolic acids (TFPC) and total soluble conjugates (TSC), identified phenolic acids, total antioxidant capacity (TAC), water-soluble carbohydrates (WSC) and total methanol extracts (TME). High-performance liquid chromatography (HPLC) coupled with a photodiode array detector (PDA) was used in this study for the analysis of p-coumaric acid and ferulic acid in barley bran before and after steam explosion. Our results indicate that TSPC and TAC increased with residence time. They also increased dramatically with temperature up to 220 °C. After steam explosion at 220 °C for 120 s, the TSPC reached 1686.4 gallic acid equivalents mg/100 g dry weight, which was about 9-fold higher than that of the untreated sample. The TSPC and TAC obtained were highly positively correlated (r = 0.918-0.993), which meant that the increase of TAC for the steam explosion pretreated barley bran extracts was due, at least in part, to the increase of TSPC in the methanol soluble fraction. Also, under optimum conditions, the WSC in aqueous solution was 5 times as much as that of the untreated sample, which demonstrated that steam explosion also hydrolyzes carbohydrates into water-soluble sugars. It can be concluded that a proper and reasonable steam explosion pretreatment could be applied to release the bound phenolic compounds and enhance the antioxidant capacity of barley bran extracts.     

Long-term effects of farmyard manure and sewage sludge on some soil biochemical characteristics

 Changes in some soil biochemical properties were investigated following repeated applications of aerobically digested sewage sludge (SS) under field conditions over 12 years, and compared with those of an adjacent soil cultivated and amended with 5 t ha^–1 year^–1 (dry weight) farmyard manure (FYM) for at least 40 years, as well as with those of an adjacent uncultivated soil, in order to ascertain changes in soil quality. A short-term aerobic incubation was used to determine the potential of the samples to mineralize the organic C supplied. Results indicated that cultivation caused a reduction in total, humified and potentially mineralizable organic C, total N, light-fraction (LF) C, total and water-soluble carbohydrates, phenolic compounds, cation-exchange capacity (CEC), microbial biomass C, specific respiration, hydrolytic and urease activities, and an increase in the heavy metal content. Total and water-soluble carbohydrates and phenolic compounds expressed as a percentage of total organic C (TOC) were similar in the differently managed plots. Of the two amendments, FYM treatments showed higher amounts of TOC and N, LF-C, total and water-soluble carbohydrates, phenolic substances, CEC, specific respiration of biomass, hydrolytic and urease activities, similar amounts and characteristics of humified organic matter and lower concentrations of Cu, Zn and Cr. Both FYM and SS were inadequate treatments for the restoration of soil organic matter lost as a consequence of cultivation. Received: 20 October 1998     

Assessment of antioxidant activity of cane brown sugars by ABTS and DPPH radical scavenging assays: determination of their polyphenolic and volatile constituents

Seven cane brown sugars (four from La Réunion, two from Mauritius, and one from France) were investigated for their polyphenol content and volatile composition in relation to their free radical scavenging capacity determined by ABTS and DPPH assays. The thin layer coated on the sugar crystal was extracted by Soxhlet extractor with dichloromethane. The volatile compounds of brown sugars were studied by GC-MS, and 43 compounds were identified. The total phenolic content of brown sugars was determined according to the Folin-Ciocalteu method. Phenolic compounds were quantified in the brown sugar extracts by LC-UV-ESI-MS. Brown sugar aqueous solutions exhibited weak free radical scavenging activity in the DPPH assay and higher antioxidant activity in the ABTS assay at relatively high concentration. The brown sugar extracts showed interesting free radical scavenging properties despite the low concentration of phenolic and volatile compounds. Sugar is a common foodstuff traditionally used for its sweetening properties, which might be accompanied by antioxidant properties arising from molecules (polyphenols, Maillard products) other than sucrose of the cane brown sugars.     

Individual organic compounds in water extracts from podzolic soils of the Komi Republic

The contents of organic compounds in water extracts from organic horizons of loamy soils with different water contents from the medium taiga zone of the Komi Republic were determined by gas-liquid chromatography and chromatography-mass spectrometry. The mass concentration of organic carbon in the extracts was in the range of 290?C330 mg/dm³; the mass fraction of the carbon from the identified compounds was 0.5?C1.9%. Hydrocarbons made up about 60% of the total identified compounds; acids and their derivatives composed less than 40%. Most of the acids (40?C70%) were aliphatic hydroxy acids. The tendencies in the formation of different classes of organic compounds were revealed depending on the degree of the soil hydromorphism. The acid properties of the water-soluble compounds were studied by pK spectroscopy. Five groups of compounds containing acid groups with similar pK_a values were revealed. The compounds containing groups with pK_a < 4.0 were predominant. The increase in the surface wetting favored the formation of compounds with pK_a 3.2?C4.0 and 7.4?C8.4.