Changes in physicochemical characteristics and volatile constituents of strawberry (Cv. Cigaline) during maturation     

Ménager I  Jost M  Aubert C 《Journal of agricultural and food chemistry》2004,52(5):1248-1254

Changes in the volatile composition of strawberries (cv. Cigaline) at six stages of maturity, from 28 to 44 days after anthesis, were investigated over two harvesting seasons. Volatiles were isolated by direct solvent extraction and analyzed by means of GC-FID and GC-MS, with special attention to the quantification of furanones. Firmness, skin color, soluble solids (SS), titratable acidity (TA), SS/TA ratio, organic acids, and sugars were also determined. With increasing maturity, soluble solids, SS/TA ratio, Minolta a value, and levels of sucrose, glucose, fructose, and malic acid increased, whereas Minolta L value, hue angle (), titratable acidity, and levels of citric acid decreased. Furanones and esters were generally not detected before half-red fruits, whereas C(6) compounds were the main compounds in immature fruits. During maturation, levels of these so-called green components decreased drastically, whereas levels of key flavor compounds increased significantly and were closely correlated with skin color development. Maximum volatile production was observed in fully red fruits.  相似文献   

An Easy Method to Measure Total Particulate Hg in Water Without Chemical Digestion     

Sarica  José  Amyot  Marc  Hare  Landis 《Water, air, and soil pollution》2004,151(1-4):3-10

Particle transport often plays an important role in trace metal cycling in aquatic systems. In this study, we propose a simple method to estimate total particulate Hg in water using combustion as a treatment prior to analysis as opposed to conventional chemical digestion. We also present a field validation of this method in a stream. We sampled water from a stream 24 and 48 h after a heavy storm to obtain two sets of water samples with contrasting particulate Hg levels. Measurements of particulate and dissolved Hg using our new direct combustion method compared favorably with those of total Hg in unfiltered samples (112 ± 15 %). U.S. E.P.A. standard method 1631 gave similar dissolved Hg levels but different particulate Hg levels (calculated as the difference between total and dissolved Hg concentrations) than those obtained with our new method. We suggest that this discrepancy is explained by the propagation of errors resulting from the several calculation steps used in the standard method. Our new method gives reliable results, without labor intensive and costly chemical digestion and analysis of filters.  相似文献   

Potential antioxidant capacity of sulfated polysaccharides from the edible marine brown seaweed Fucus vesiculosus   总被引：12，自引：0，他引：12  

Rupérez P  Ahrazem O  Leal JA 《Journal of agricultural and food chemistry》2002,50(4):840-845

Fucus vesiculosus was sequentially extracted with water at 22 degrees C (fraction 1 (F1)) and 60 degrees C (F2), and with 0.1 M HCl (F3) and 2 M KOH (F4) at 37 degrees C. Soluble fractions (42.3% yield) were composed of neutral sugars (18.9-48 g/100 g), uronic acids (8.8-52.8 g/100 g), sulfate (2.4-11.5 g/100 g), small amounts of protein (< 1-6.1 g/100 g), and nondialyzable polyphenols (0.1-2.7 g/100 g). The main neutral sugars were fucose, glucose, galactose, and xylose. Infrared (IR) spectra of the fractions showed absorption bands at 820-850 and 1225-1250 cm(-1) for sulfate. F1, F2, and F4 also exhibited an absorption band at 1425 cm(-1), due to uronic acids, and their IR spectra resembled that of alginate. F3 had an IR spectrum similar to that of fucoidan with an average molecular weight of 1.6 x 10(6) Da, calculated by molecular exclusion high-performance liquid chromatography. The presence of fucose in this polysaccharide was confirmed by (1)H NMR spectroscopy. This fraction showed the highest potential to be antioxidant by the ferric reducing antioxidant power (FRAP) assay, followed by the alkali- and water-soluble fractions. Sulfated polysaccharides from edible seaweeds potentially could be used as natural antioxidants by the food industry.  相似文献   

Antioxidant activity of ethanolic extracts from several asparagus cultivars   总被引：3，自引：0，他引：3  

Rodríguez R  Jaramillo S  Rodríguez G  Espejo JA  Guillén R  Fernández-Bolaños J  Heredia A  Jiménez A 《Journal of agricultural and food chemistry》2005,53(13):5212-5217

Three different methods (antiradical activity, inhibition of primary oxidation, and ferric reducing power) have been used to evaluate the antioxidant activity of eight different asparagus cultivars and byproducts: white and green asparagus from Alcalá del Río (Guadalquivir Valley, Seville) and American hybrids, native spears, and their byproducts from Huétor-Tájar (Vega de Granada). The correlation between antioxidant activity and total phenol content was studied. Six standards were also tested to validate the modified methods for antioxidant activity determination. Results obtained for antiradical capacity and reducing power were very similar, and a high correlation with phenols was found (R > or = 0.9 for both tests). Sample origin was an important factor, spears from Huétor-Tájar having higher values (ARC between 7 and 10 and P(R) of 0.25-0.33) than those from Alcalá del Río (ARC 0.6-2 and P(R) of 0.05-0.07). Significant differences were found between spears with the same origin, suggesting that genetics are another factor to take into account. Asparagus inhibits lipid primary oxidation, but no correlation between the inhibition percentage and phenols was observed. Asparagus origin was the only factor that led to significant differences: samples from Huétor-Tájar had higher values (POIC between 18 and 32) than those from Alcalá del Río (POIC of 5-9). Byproducts from the canning industry at Huétor-Tájar were also assayed for antioxidant activity; the results obtained suggested that byproducts could be considered as an excellent source of natural antioxidants.  相似文献   

Effect of germination on the carbohydrate composition of the dietary fiber of peas (Pisum sativum L.)     

Martín-Cabrejas MA  Ariza N  Esteban R  Mollá E  Waldron K  López-Andréu FJ 《Journal of agricultural and food chemistry》2003,51(5):1254-1259

The effect of different conditions of pea germination on dietary fiber (DF) composition was studied. Insoluble dietary fiber (IDF) and soluble dietary fiber (SDF) were subjected to acid hydrolysis, and the resultant neutral sugars, uronic acids, and Klason lignin were quantified. Germinated peas exhibited significantly higher contents of total dietary fiber (TDF) than the raw sample, due to the increases of both DF fractions. Under darkness conditions, germination exhibited the highest contents of IDF and SDF. Decreasing IDF/SDF ratios showed that the carbohydrate changes did not take place to the same extent during germination, the SDF fraction being the most affected. The detailed chemical composition of fiber fractions reveals increases of cellulose in the IDF of germinated samples, whereas SDF exhibits a decrease of pectic polysaccharides and also increases of polysaccharides rich in glucose and mannose. The DF results were corroborated by a comparative examination of the cell wall carbohydrate composition.  相似文献   

Possible role of plant phenolics in the production of trichothecenes by Fusarium graminearum strains on different fractions of maize kernels     

Bakan B  Bily AC  Melcion D  Cahagnier B  Regnault-Roger C  Philogène BJ  Richard-Molard D 《Journal of agricultural and food chemistry》2003,51(9):2826-2831

Four trichothecene-producing strains of Fusarium graminearum were grown on three maize grain fractions, whole grain, degermed grain, and the germ, to determine the effect of natural substrates on mycotoxin production. Monitoring the ergosterol content after 25 days of incubation indicated that fungal growth on all grain fractions was comparable. Trichothecene (TCT) production was highest on degermed grain, less on whole grain, and very low or nondetectable on the germ; similar results were found with four different strains. It was concluded that inhibitor(s) of TCT biosynthesis were present in maize germ. The presence of phenolic compounds was investigated in the different fractions. The hydroxamate 4-acetylbenzoxazolin-2-one (4-ABOA), a known inhibitor of mycotoxin production, was found in the degermed and whole grain fractions but not in the germ. Therefore, the TCT inhibition observed on the maize germ fraction used in our study is clearly not linked to 4-ABOA. Other soluble phenolic compounds were found at a much higher concentration in the germ than in the two other fractions. The inhibition property of the soluble ester-bound extracts was tested in liquid culture. A possible role for these compounds is discussed.  相似文献   

Analysis of two bentonites of enological interest before and after commercial activation by solid Na(2)CO(3)     

Gougeon RD  Soulard M  Miehé-Brendlé J  Chézeau JM  Le Dred R  Jeandet P  Marchal R 《Journal of agricultural and food chemistry》2003,51(14):4096-4100

Two natural calcium-rich bentonites used for the removal of wine proteins, originating from Greece and Turkey, were studied by X-ray diffraction, thermal analysis, and solid state NMR, before and after activation by solid Na(2)CO(3). Exchange of Ca(2+) by Na(+) mainly occurs for cations located at the edge of layers and only weakly for interlayer cations. This Na(2)CO(3) activation process leads to an increased efficiency in the adsorption process of bovine serum albumin (BSA) used as a model protein for both bentonites. A direct correlation is observed between the extent of Ca(2+)/Na(+) exchange, the strength of adsorption of BSA, and the extent of unfolding of BSA backbone.  相似文献   

Pectins as possible source of the copper involved in the green staining alteration of cv. Gordal table olives     

Gallardo-Guerrero L  Hornero-Méndez D  Mínguez-Mosquera MI 《Journal of agricultural and food chemistry》2002,50(23):6746-6751

The pectic and pigment compositions and Ca and Cu contents of the alcohol-insoluble solid (AIS) residues were determined in cv. Gordal olives treated with NaOH solution and kept at different constant pH values (3.5-6.5). The same controls were made in table olives presenting green staining alteration. The ratio between the various pectin fractions of the more acid pH experiment samples remained similar in fruits not showing green staining. In altered fruits, the protopectin fraction was lower, and the calcium pectate or EDTA soluble pectins were higher. Regarding the presence of Ca and Cu in the AIS, it was observed that, whereas Ca levels fell at the most acid pH values, those of Cu increased. The concentration of Ca was higher in the AIS of altered olives than in nonaltered ones. The same trend was seen for the zone with or without green staining of an altered fruit. In the case of Cu, the relationship was the opposite: a decrease in the levels of AIS Cu in fruits and zones of fruits with green staining. This result was correlated with the highest concentration of Cu-chlorophyll complexes found in such samples and suggested that pectins might act as a reservoir of Cu involved in the alteration.  相似文献   

Study of carbendazin residue accumulation on greenhouse and field-grown strawberries, after successive treatments with benomyl     

A Mònico-Pifarré  M Xirau-Vayreda 《Journal of the Association of Official Analytical Chemists》1990,73(4):553-556

Benomyl, a systemic fungicide used in preharvest treatments to prevent Botrytis and other fungal diseases, metabolizes to carbendazim (MBC). A study was undertaken to determine if the total residues of MBC of greenhouse and field-grown Douglas strawberries accumulate in fruits after successive fortnightly treatments with a commercial preparation of benomyl. Statistical analysis of the data obtained indicates that residues of MBC do not accumulate in fruits; on the contrary, they decrease over time.  相似文献   

Limited downward migration of pollutant metals (Cu,Zn, Ni,and Pb) in acidic virgin peat soils near a smelter     

S. Dumontet  M. Lévesque  S. P. Mathur 《Water, air, and soil pollution》1990,49(3-4):329-342

The distribution of pollutant heavy metals (Cu, Zn, Ni, Cd, and Pb) was determined in 11 acidic virgin peat profiles located along two transects moving away from a smelter plant in the Noranda region of Quebec. The levels of all five metals were found highest in the 0 to 15 cm layer at site near the smelter, and decreased progressively with the distance from the smelter, up to 42 km. Copper had the highest concentrations (5525 μg g^?1) followed by Pb and Zn. The maximum levels of total metals built up in the peat surface near the smelter were high, approximately reaching the threshold limits for phytotoxicity in peat soils. The amounts of heavy metals moving down and accumulating in the anaerobic zone of the peat profiles were limited. The distribution and enrichment ratios in the profiles showed that Cu, Zn, and Cd would have relatively higher mobility than Pb.  相似文献