Phenolic compounds in olive oils intended for refining: formation of 4-ethylphenol during olive paste storage     

Brenes M  Romero C  García A  Hidalgo FJ  Ruiz-Méndez MV 《Journal of agricultural and food chemistry》2004,52(26):8177-8181

The phenolic composition of "lampante olive oil", "crude olive pomace oil", and "second centrifugation olive oil" was characterized by high-performance liquid chromatography with UV, fluorescence, and mass spectrometry detection. The phenolic profile of these olive oils intended for refining was rather similar to that previously reported for virgin olive oil. However, a new compound was found in these oils, which is mainly responsible of their foul odor. It was identified as 4-ethylphenol by comparison of its UV and mass spectra with those of a commercial standard. Although 4-ethylphenol was discovered in all oils intended for refining, its presence was particularly significant in "second centrifugation olive oils", its concentration increasing with time of olive paste storage. Similar trends were observed for hydroxytyrosol, hydroxytyrosol acetate, tyrosol, and catechol, the concentration of these substances reaching values of up to 600 mg/kg of oil, which makes their recovery for food, cosmetic, or pharmaceutical purposes attractive.  相似文献   

分子蒸馏在小麦胚芽生物活性成分提取中的应用   总被引：5，自引：0，他引：5  

赵妍嫣  唐文婷  姜绍通 《农产品加工．学刊》2004,(11):33-34

简述了分子蒸馏的基本原理、技术特点以及在生物有效组分分离方面的应用现状。重点介绍了分子蒸馏在小麦胚芽中的生物活性成分维生素E及二十八醇提取中的工艺路线，操作要点及主要优点。  相似文献   

选择酶源提高酶法测定有机磷农药的灵敏度     

陆贻通 《农业环境科学学报》1984,(3)

以抑制胆碱酯酶(ChE)技术为依据的酶抑制法,现已和比色、薄层层析法相结合,用以检测和鉴定有机磷农药。其检测下限随着选用不同的酶源而不同。这种对有机磷化合物检测灵敏度变化的原因还很少报道过。Sana Udaya Bhaskar的试验得到了表示一种酶和基质亲合力大小的米氏常数Km,和  相似文献   

农产品物理特性的检测与应用研究进展   总被引：1，自引：1，他引：1  

Annia García Pereir  Antihus Hernández Gómez  何勇 《农业工程学报》2003,19(5):7-11

农产品物理特性在测定农产品的物理特征（如：形状、体积、尺寸、密度、颜色、外观）、水果的坚实度、成熟度和品质及估算谷物的损坏程度、种子的品质、完整性和遗传变化等方面起着非常重要的作用。介绍了几种被广泛应用的农产品物理特性：电导率、光学性质、力学性质和热传导性，并分析了它们在测定水果、蔬菜和谷物的湿度、密度、微波介电频率、成熟度、坚实度及其它一些参数中的具体应用，同时还介绍了专家们在这个领域近三十年来的研究成果。  相似文献   

Phenolic diterpenes,flavones, and rosmarinic acid distribution during the development of leaves,flowers, stems,and roots of Rosmarinus officinalis. Antioxidant activity     

del Baño MJ  Lorente J  Castillo J  Benavente-García O  del Río JA  Ortuño A  Quirin KW  Gerard D 《Journal of agricultural and food chemistry》2003,51(15):4247-4253

The distribution of six compounds with three different polyphenol skeletons have been studied in Rosmarinus officinalis: phenolic diterpenes (carnosic acid, carnosol, and 12-O-methylcarnosic acid), caffeoyl derivatives (rosmarinic acid), and flavones (isoscutellarein 7-O-glucoside and genkwanin), each showing a characteristic behavior and distribution during the vegetative cycle. Only in leaves were all six compounds present, and the highest accumulation rate was related with the young stages of development. Rosmarinic acid showed the highest concentrations of all the polyphenols in all organs. The distribution of this acid in leaves, flowers, and stems suggests that in the first stages of flower growth, levels were due to in situ biosynthesis, and in the last stages, the contribution of transport phenomena was increased. The antioxidant activity of six extracts with different polyphenolic composition was evaluated in aqueous and lipid systems. The results clearly suggest that rosemary extracts are excellent antioxidants in both aqueous and lipid systems.  相似文献   

Antioxidant activity in common beans (Phaseolus vulgaris L.)   总被引：4，自引：0，他引：4  

Cardador-Martínez A  Loarca-Piña G  Oomah BD 《Journal of agricultural and food chemistry》2002,50(24):6975-6980

Beans were pearled to evaluate the feasibility of increasing antioxidant activity and phenolic antioxidants. Phenolics were concentrated mostly in the hull fraction at about 56 mg of catechin equivalents per gram of sample. The methanolic extracts of the pearled bean samples were screened for antioxidant potential using the beta-carotene-linoleate and the 1,1-diphenyl-2-picrylhydrazyl (DPPH) in vitro model systems. The pearled material, also referred to as milled samples, exhibited antioxidant activity that correlated with phenolic content and inhibited DPPH significantly in a dose-dependent manner. Phenolics and antioxidant activities were also examined in chromatographic fractions of methanolic extracts of manually obtained hulls that represented a model used previously to ascertain antimutagenic activity. Fractions extracted with ethyl acetate/acetone and acetone displayed antioxidant activity, which implies potent free radical scavenging activity with antimutagenic activity.  相似文献   

Changes in low molecular weight phenolic compounds in Spanish, French, and American oak woods during natural seasoning and toasting     

Cadahía E  Muñoz L  Fernández de Simón B  García-Vallejo MC 《Journal of agricultural and food chemistry》2001,49(4):1790-1798

The evolution of low molecular weight polyphenols in Spanish oak heartwood of Quercus robur,Quercus petraea, Quercus pyrenaica, and Quercus faginea was studied by HPLC, in relation to the processing of wood in barrel cooperage. The polyphenolic composition of Spanish woods subjected to natural seasoning for 3 years and to the toasting process was studied in relation to those of French oak of Q. robur (Limousin) and Q. petraea (Allier) and American oak of Q. alba (Missouri), which are habitually used in cooperage. The concentrations of benzoic and cinnamic acids and aldehydes of Spanish woods increased during seasoning depending on the duration of this process and in the same way as those of French and American woods. The process having the main influence on the phenolic composition of wood was the toasting. It led to high increases in the concentration of phenolic aldehydes and acids, especially cinnamic aldehydes (sinapic and coniferylic aldehydes), followed by benzoic aldehydes (syringaldehyde and vanillin) and benzoic acids (syringic and vanillic acids). This polyphenolic composition in Spanish oak species evolved during toasting as in French and American oak, but quantitative differences were found, which were especially important in American species with respect to the others.  相似文献   

Mycoflora and occurrence of aflatoxin B(1) and fumonisin B(1) during storage of Brazilian sorghum     

da Silva JB  Pozzi CR  Mallozzi MA  Ortega EM  Corrêa B 《Journal of agricultural and food chemistry》2000,48(9):4352-4356

The present study is a 1-year follow up of the mycoflora of 140 samples of Brazilian freshly harvested (10) and stored (130) sorghum, the levels of aflatoxin and fumonisin contamination detected in the grains, and the prevailing abiotic factors (grain moisture content, water activity, temperature, relative humidity, and mean rainfall) at the time of sampling. The results show a predominance of the genera Phoma (57.1%), Aspergillus (42.7%), Fusarium (25.0%), and Rhizopus (21.4%) and the presence of nine other filamentous fungi. Fusarium, Aspergillus, and Penicillium, the three most important genera in terms of toxicity, presented numbers of colony forming units per gram of sorghum (CFU/g) that varied from 1 x 10(3) to 36 x 10(3), from 1 x 10(3) to 295 x 10(3), and from 1 x 10(3) to 20 x 10(3) CFU/g, respectively. The species most frequently found were Aspergillus flavus and Fusarium moniliforme. Of the total samples analyzed, 12.8% were contaminated with aflatoxin B(1) (concentration mean = 7-33 microg/kg) and 74.2% with fumonisin B(1) (concentration mean = 0.11-0.15 microg/g). This paper is the first report of the natural occurrence of aflatoxins and fumonisins in sorghum grain from Brazil.  相似文献   

Effect of beta-carotene and vitamin E on oxidative stability in leg meat of broilers fed different supplemental fats   总被引：3，自引：0，他引：3  

Ruiz JA  Pérez-Vendrell AM  Esteve-García E 《Journal of agricultural and food chemistry》1999,47(2):448-454

The objectives of this study were to investigate the effects of dietary fat (6% lard and sunflower and olive oil) and supplementation of alpha-tocopheryl acetate or beta-carotene on vitamin E content and lipid oxidation in raw, cooked, and chilled-stored broiler leg meat. Vitamin E increased its tissue level, reducing lipid oxidation. The oxidative stability of leg meat tended to decrease with dietary sunflower oil. Effects of beta-carotene on vitamin E levels and oxidation depended on dietary fat and its concentration in feed, decreasing vitamin E, mainly at 50 ppm. beta-Carotene at 15 ppm acted as antioxidant in fresh and cooked meat in the sunflower and olive oil diets. However, in stored meat, beta-carotene at 50 ppm increased TBARS, probably due to a decrease in vitamin E content and direct prooxidant effects per se. It is suggested that the antioxidant effect of beta-carotene requires the presence of vitamin E in tissues.  相似文献   

Influence of yeast strain and aging time on free amino acid changes in sparkling ciders     

Suárez Valles B  Palacios García N  Rodríguez Madrera R  Picinelli Lobo A 《Journal of agricultural and food chemistry》2005,53(16):6408-6413

An analytical method for the determination of free amino acids in ciders is reported. It is based on high-performance liquid chromatography with an automatic precolumn derivatization with o-phthaldehyde and 3-mercaptopropionic acid and diode array detection. The method was applied to monitor the amino acids during second fermentation of sparkling ciders. This paper reports the influence of yeast strains and aging time on the amino acid composition of sparkling ciders. The application of principal component analysis enables the ciders to be differentiated on the basis of the two factors considered (yeast strain and aging time). The first principal component, which accounts for 58% of the total variance, achieved the separation according to aging time with serine, glycine, alanine, valine, ornithine, leucine, and lysine as the most important variables. The second principal component, accounting for 28% of the explained variance, is closely related to aspartic acid and asparagine and separates the samples according to the yeast strain.  相似文献