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991.
During dough fermentation, yeast (Saccharomyces cerevisiae) changes the physical properties of the dough matrix. In this study, we investigate if different yeast strains have an impact on dough rheology and on the gas holding capacity of fermenting dough. Furthermore, we analyze whether observed differences are linked to the metabolite profiles of the yeast strains. More specifically, the impact of 25 yeast strains on dough spread, dough fermentation properties, and dough metabolite profile was analyzed. Our results demonstrate large differences in the fermentation ability and metabolite profile of the 25 strains. Analysis of metabolites in fermented dough confirmed that acetic acid and succinic acid are likely responsible for the lowering of dough pH during fermentation and that the onset of CO2 release from dough is related to dough pH rather than to the volume of CO2 within the dough. Our results further suggest that the spread test is an inadequate tool to quantify rheological differences observed for strains with different fermentation profiles. 相似文献
992.
Adelheid R. Kuehnle David H. Lewis Kenneth R. Markham Kevin A. Mitchell Kevin M. Davies Brian R. Jordan 《Euphytica》1997,95(2):187-194
Anthocyanidins were identified in 28 Dendrobium species and hybrids selected for analysis based on colour and suitability
in cut flower breeding. Flowers designated pink, red, maroon, orange, bronze, and brown in the trade were placed in RHS colour
groups red-purple, purple-violet, violet on yellow, greyed-purple on yellow or yellow-orange, and brown. This colour range
contained anthocyanins based on cyanidin, with peonidin occurring as a minor pigment. The colours of three blue genotypes,
D. gouldii K280-6, D. biggibum ‘blue’, and D. Kultana ‘blue’, were light violet to purple by RHS standards and contained anthocyanins
based on cyanidin. Peach-coloured flowers were classified as red or red-purple and included pelargonidin glycosides. Anthocyanin
concentrations ranged from 0.13 to 0.18 μmoles/g FW in light lavender and peach, and up to 3.66 μmoles/g FW in brown. Combined
cellular and vacuolar pH ranged narrowly from 4.67 to 5.09 among white, peach, lavender, and brown lines. Predominant copigments
were flavonol glycosides based on kaempferol, quercetin, myricetin, and methylated derivatives. Flavonol aglycones and glycosylation
sites differed little among two colour forms of D. gouldii and two D. Jaquelyn Thomas hybrids. Accumulation of quercetin,
myricetin, and cyanidin indicated flavonoid 3' and 3',5' hydroxylation activities in several Dendrobium. Additional accumulation
of isorhamnetin, syringetin, and peonidin indicated active flavonoid 3'- and 3',5'- O-methyltransferase enzymes.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
993.
994.
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996.
Age-induced diminution of free radical scavenging capacity in bee pollens and the contribution of constituent flavonoids 总被引:12,自引:0,他引:12
Campos MG Webby RF Markham KR Mitchell KA Da Cunha AP 《Journal of agricultural and food chemistry》2003,51(3):742-745
Bee-collected pollen ("bee pollen") is promoted as a health food with a wide range of nutritional and therapeutic properties. The objective of the current study is to evaluate the contribution made through the free radical scavenging capability of bee-collected floval pollens by their flavonoid/phenolics constituents, and to determine whether this capability is affected by aging. The free radical scavenging effectiveness of a bee pollen (EC(50)) as measured by the DPPH method is shown to be determined by the nature and levels of the constituent floral pollens, which can be assayed via their phenolics profiles by HPLC. Each pure floral pollen has been found to possess a consistent EC(50) value, irrespective of its geographic origin or date of collection, and the EC(50) value is determined to a large extent (ca. 50%) by the nature and the levels of the pollen's flavonoids and phenolic acids. Non-phenolic antioxidants, possibly proteins, account for the balance of the activity. Pollen aging over 3 years is demonstrated to reduce the free radical scavenging activity by up to 50% in the most active floral pollens, which tend to contain the highest levels of flavonoids/phenolic acids. It is suggested that the freshness of a bee pollen may be determined from its free radical scavenging capacity relative to that of fresh bee pollen containing the same floral pollen mix. 相似文献
997.
998.
Barbara C. Reynolds Jennifer Hamel Jason Isbanioly Leonardo Klausman Kevin K. Moorhead 《Pedobiologia》2007,51(4):273-280
Our study compared decomposition and litter microarthropod abundance among five plant communities in a mountain floodplain/fen complex located in the southern Appalachian Mountains, USA. We found that the least disturbed plant communities, red maple in particular, have the quickest decomposition, the greatest number of litter microarthropods, the highest soil organic carbon, and the lowest soil pH. Positive correlations were shown between soil organic carbon and total microarthropods; negative correlations were found between soil pH and total microarthropods. No correlations were found between soil moisture and decomposition or total microarthropod numbers. We conclude that soil characteristics related to disturbance, rather than to the presence of a closed canopy, are the main influences on decomposition and litter microarthropods. 相似文献
999.
Beauvais Sheryl L. Cole Kevin J. Atchison Gary J. Coffey Michael 《Water, air, and soil pollution》2002,135(1-4):249-264
Organophosphorus insecticides (OPs) are widely used to control crop pests, and can enter aquatic systems draining agriculturalwatersheds. Because OPs are highly toxic to aquatic organisms,monitoring is important, yet difficult due to the low persistenceof many OPs. Cholinesterase (ChE) inhibition can be used to monitor organisms' exposure to OPs and carbamates; however, highvariability in ChE activity may interfere with the ability of theassay to detect OP exposure. Several potential sources of variation in ChE activity, including water temperature, storage of samples, euthanasia method, and fish sex and size, were investigated in bluegill (Lepomis macrochirus). ChE activity did not vary significantly with water temperature in the range 20–31 °C, or following short-term storage ofeuthanized bluegill up to 8 h at 4 and 19 °C or long-term storage of brain homogenates up to 389 d at –198 °C. There was no difference in ChE activity by euthanasia method (spinal cord severing or anesthesia with Finquel®), nor by sex of fish. Mean ChE activity variedinversely with fish total length. Of the variables investigated in this study, only size needs to be restricted in fish collectedfor monitoring of OPs. 相似文献
1000.
Plant sterols (phytosterols) have been shown to possess serum cholesterol-lowering properties. In recent years, several phytosterol-enriched functional food products have been developed and marketed. Some phytosterol products contain common unsaturated sterols and some contain a subset of phytosterols called phytostanols (saturated sterols, also called plant stanols). Current methods for the quantitative analysis of plant sterols are labor intensive and require sophisticated gas or liquid chromatographs. In this study, a popular commercial spectrophotometric serum cholesterol test kit was evaluated for the analysis of plant sterols. The results indicate that the method could be modified to analyze phytosterols and phytostanols by increasing the incubation time. Both free phytosterols and fatty acyl phytosteryl esters were quantitatively analyzed, but ferulate phytosteryl esters, such as those that are found in corn and other cereals, were not hydrolyzed by the enzymes in the test kit and therefore were not detected. 相似文献