气相色谱法快速测定二甲醚液相组分校正因子及其含量

采用吸收法配制二甲醚液相组分标样,以GDX-403为固定相,建立气相色谱法分析甲醇脱水制二甲醚液相组分校正因子及其含量的方法,并对该方法的准确性及各种影响因素进行了研究。该分析方法快速简便,结果令人满意。     

Quality differences of gilthead sea bream from distinct production systems in Southern Europe: Intensive,integrated, semi-intensive or extensive systems

The quality of gilthead sea bream from distinct production systems and geographical locations in Southern Europe was evaluated to differentiate aquaculture products from extensive, integrated and semi-intensive systems from the ones produced intensively. This work analysed the external appearance of fish, yields after filleting as well as nutritional, sensory and histological characteristics of the muscle. The results showed that the yellow-golden line between eyes and the shiny red spot on the gill cover can be important and easy criteria to discriminate aquaculture products. Trimming losses are higher in fish from intensive systems. Lipid content of fish from extensive systems was significantly lower than values observed for fish reared intensively. Samples from the integrated and extensive systems showed the best n-3/n-6 ratio, contrarily to intensive systems, but it is difficult to establish clear quality markers to differentiate gilthead sea bream according to the rearing system. Regarding sensory characteristics, the sea bream flesh from intensive systems seems firmer and denser, having smaller white fibres and higher density of fibres in the dorsal muscle. The taste and odour of fatty fish was less strong in fish reared in non-intensive conditions, but extensive rearing in earthen pond is more propitious to the development of certain characteristics related to the environment.     

Microbiological quality of organic and conventional vegetables sold in Brazil

While searching for healthier diets, people became more attentive to organic produce. Yet, organic foods may be more susceptible to microbiological contamination because of the use of organic fertilizers, a possible source of pathogenic bacteria. In this study, 130 samples of different organic and conventional vegetable varieties sold in Brazil were analyzed for mesophilic aerobic bacteria, yeasts and molds, total coliforms, Escherichia coli and Salmonella spp. Most of the mesophilic aerobic bacteria counts in organic and conventional vegetables ranged from 6 to 7 log10 CFU/g; most of the yeasts and molds counts ranged from 5 to 6 log10 CFU/g and most of the total coliforms counts ranged from 4 to 5 log10 CFU/g. E. coli was found in 41.5% of the organic and 40.0% of the conventional vegetables, and most samples had counts ranging from 1 to 2 log10 CFU/g. Salmonella spp. was not found in any sample. Comparative analyses of the microbial counts of organic and conventional vegetables showed that some organic varieties have greater counts. However, the global results show that this is not a trend. These results indicate the need of good farming practices, and proper sanitization before consumption, to ensure food quality and safety.     

Mycotoxins in maize grains grown in organic and conventional agriculture

Maize is traditionally used for bakery in several countries, and autochthonous varieties are increasingly demanded particularly for organic agriculture, but one of the dangers of cereal consumption is mycotoxin contamination. Mycotoxins are dangerous for health and might be present in any grain depending on genotypes and environments. In the present work we assess the natural levels of fumonisin and deoxynivalenol (DON) contaminations in nine diverse open-pollinated maize varieties grown in four different locations, under organic or conventional conditions, in two regions from the humid Spain during two years. Differences were significant among locations and among varieties for fumonisin contamination but not for DON content. Locations were the main environmental source of variation affecting fumonisins while DON was more affected by years. The Basque locations had more fumonisin than the Galician locations, but there were no differences between organic and conventional environments. Fumonisin contamination was more variable than DON among locations and among varieties. Fumonisin and DON were highly correlated on average but correlations were low for each particular environment. Mean fumonisin and DON were below the threshold allowed by the EU, but the white-kernel medium late variety Rebordanes(P)C2 had more than 4.00 mg/kg of fumonisin in one location, while the early yellow variety Sarreaus had the lowest contamination. We conclude warning producers of the danger of natural contamination with mycotoxins for some varieties in specific environments.     

Selective chromatographic determination of sulfur-containing compounds in work-area atmosphere

Chemistry and Technology of Fuels and Oils -     

Estimation of dietary intakes of fumonisins B1 and B2 from conventional and organic corn

The dietary intakes of fumonisins from 60 samples of conventional and organic corn were assessed. A 13.3% of the conventional corn samples contained fumonisin B₁ and B₂ at mean levels of 43 and 22 ng/g, respectively, while 10% of the organic corn samples contained fumonisins at somewhat lower levels of 35 ng/g (FB₁) and 19 ng/g (FB₂). Overall, the fumonisin levels in the corn samples were much lower than the maximum level of 2000 ng/g (as the sum of FB₁ and FB₂) proposed for unprocessed maize in a recent EU regulation. The fumonisins present in conventional and organic maize are estimated to contribute with very low percentages of 0.21% and 0.17%, respectively, to the level considered at risk for human health. Based on the data exposed in this paper, the farming system is probably not of decisive importance for the final contamination of agricultural products with these mycotoxins.     

The concentration of minerals and physicochemical contaminants in conventional and organic vegetables

In this study, we performed a comparative analysis of the physical-chemical composition and pesticide residue content of lettuce, peppers, and tomatoes that were grown in organic and conventional systems. The vegetables were purchased at the Food Supply Centre of Pernambuco [Centro de Abastecimento Alimentar de Pernambuco – CEASA/PE], Pernambuco state, Brazil. The physical-chemical composition of the vegetables was determined according to the analytical procedures of the Association of Official Analytical Chemist. The minerals (Cu, Cr, Fe, K, Mn, Mg, Na, and Zn) and the heavy metals (Cd, Ni, and Pb) were assessed using atomic absorption spectrometry, and the pesticide residues were determined using a multi-residue analysis. The results were compared by means of a Student's t-test. Principal component analysis was performed to investigate the correlations between the minerals and the heavy metals. The measurements of weight, length, and width of all three of the vegetables that were assessed were higher in the conventional group. There were significant differences (p < 0.05) in the proximate composition of conventional and organic lettuces (moisture, ash and protein) and in all the parameters of conventional and organic peppers. To tomatoes there wasn't significant difference (p > 0.05). All three of the organic vegetables were higher in total dietary fibre. The composition of the minerals and heavy metals varied between all three vegetables. Contamination by pesticide residues was found in conventional peppers and organic tomatoes.     

Co-occurrence and evaluation of mycotoxins in organic and conventional rye grain and products

A study on the co-occurrence of Fusarium toxins in conventional and organic grain and derived products was carried out. A total of 117 samples were collected during the period 2009–2012. Eight mycotoxins were determined using the LC-MS/MS method. Among the investigated mycotoxins, four were of major importance: DON, ZEN, T-2 and HT-2. DON was present at the highest concentration in both the agricultural systems, with its maximum level of 254 ± 23 μg kg⁻¹ being present in conventional rye grain. The co-occurrence of two or more mycotoxins was observed in more than 50% of samples, with the most frequent combination being DON + ZEN. The correlation between the concentrations of T-2 and HT-2, DON and ZEN, as well as T-2 and ZEN was confirmed statistically. The concentration of DON, HT-2 and T-2 was significantly higher in conventional products. Also the higher level of ZEN in organic grain in comparison to derived products was significant. None of the samples contained DAS, while NlV, MAS and 3ADON concentrations were close to the detection limits.     

Patulin assessment and fungi identification in organic and conventional fruits and derived products

In this study, patulin levels in apples and tomatoes obtained in conventional and organic farms with 0 and 100% of rotten area, were determined by gas chromatography–mass spectrometry (GC–MS) to assess the influence of the production system with patulin content. Additionally, mould species were isolated and identified using classic morphological techniques and a DNA barcode system based on nrITS, β-tubulin and calmodulin genes. The most frequently isolated genera were Rhizopus, Mucor, Alternaria, Cladosporium, Botrytis, Aspergillus and Penicillium. Higher patulin levels were found in samples contaminated by Penicillium expansum. Patulin levels were not significantly different in samples obtained from the two production system (conventional and organic). Among the three studied apple varieties, Golden delicious was the most contaminated with patulin followed by Reineta. Fuji apples with 0 and 100% of rotten area did not present quantifiable patulin levels. A survey for first time realized in commercialized tomato products showed that 35.7% of the samples (10 of 28) contained patulin in levels ranging from 3.22 to 47.72 μg/kg. In apple juices, patulin levels ranged from 1.86 to 45.47 μg/kg, which is below the maximum legal requirement (50 μg/kg).     

准噶尔盆地油气资源潜力与中国石化常规—非常规油气一体化勘探策略

准噶尔盆地油气资源丰富,勘探潜力巨大,是我国油气增储上产的主战场之一。近年来中国石油在准噶尔盆地勘探不断取得重大突破,揭示了常规、非常规油气有序共生的分布格局。为进一步吸收邻区油气成果勘探开发经验和地质理论新认识,制定中国石化在准噶尔盆地的油气勘探策略,文章系统分析了准噶尔盆地油气资源潜力及分布特征,指出了目前资源评价中存在的对天然气和非常规油气资源不够重视的问题;通过梳理近年来盆地在多领域、多层系、多类型的重大油气勘探突破,结合中国石化矿权区油气地质条件和勘探实际,提出中国石化下一步在准噶尔盆地的重点突破方向及勘探策略。研究表明,准噶尔盆地目前已进入中下组合勘探为主的新时期,勘探思路也必须随之调整,必须坚持由早期的源外勘探转为源内及近(进)源勘探,由早期的常规油气勘探为主,转为常规—非常规油气并重;并就下一步如何尽快实现中国石化在准噶尔盆地的大突破、大发现和增储上产目标,提出进一步摸清资源家底、组建常规—非常规一体化攻关团队、加强地质—工程一体化联合攻关和加大风险勘探力度等4个方面的勘探策略。