Development of a polymerase chain reaction assay for species identification of goose and mule duck in foie gras products

Polymerase chain reaction amplification of a conserved region of the -actin gene has been used for the specific identification of goose (Anser anser) and mule duck (Anas platyrhynchos×Cairina moschata) foie gras. Universal primers were used for the amplification of a DNA fragment containing three introns and four exons of the -actin gene in goose and mule duck. Sequence analysis of the amplified fragments was necessary for the design of forward species-specific primers in the goose and mule duck -actin genes. The use of species-specific forward primers, together with a reverse universal primer, produced amplicons of different length, allowing clear identification of goose and mule duck foie gras samples. Analysis of experimental mixtures demonstrated that 1% of duck can be easily detected in goose foie gras using the PCR method developed here. This genetic marker can be very useful for the accurate identification of these two species in foie gras products.     

The relationship between the levels of α-tocopherol and carotenoids in the maternal feed,yolk and neonatal tissues: comparison between the chicken,turkey, duck and goose

The relationship between the levels of the lipid-soluble antioxidants, α-tocopherol and carotenoids, in the parental diet, the yolk and the neonatal tissues was investigated for four avian species of commercial importance. The chicken displayed a much greater efficiency in incorporating α-tocopherol from the parental diet into the yolk in comparison with the turkey, duck and goose. Thus, in spite of similar concentrations in the respective diets, the resultant concentration of α-tocopherol in the yolk of the chicken egg was four to five times greater than observed for the other three species. A similar but less dramatic picture was observed for carotenoids: identical dietary provision of carotenoids in the maternal feeds resulted in the chicken eggs displaying between 1·4 and 1·9 times the concentration in the yolk than was observed for the other three species. These differences between the species regarding the levels of α-tocopherol and carotenoids in the yolk were closely reflected in the subsequent concentrations of these components in the livers of the hatchlings. Thus, the concentrations of α-tocopherol and carotenoids in the liver of the day-old chicken were respectively about three and two times greater than in the livers of the other three species. Although the water-soluble antioxidant, ascorbic acid, is synthesised by the embryo as opposed to provision via the maternal diet and the yolk, the concentration of this component in the brain of the day-old chicken was approximately 50% greater than in the brains of the other three species. Thus, it is possible that the antioxidant capacity of the developing turkey, duck and goose may be compromised under conditions of commercial production. All four species displayed a rapid depletion of α-tocopherol and carotenoids from the livers during the first 9 days after hatching. © 1998 SCI.     

鲜鸡肠与鸭肠、鹅肠中6种微量金属元素含量对比研究

目的 对比分析鸡肠与鸭肠和鹅肠中6种微量金属元素含量差异。方法 使用HNO3-HClO4体系消解样品, 采用火焰原子吸收光谱法对鸡肠中的Ca, Fe, Mn, Zn, Cu, Mg 6种微量金属元素进行测定。结果 方法学验证结果显示该方法的线性关系良好, 精密度、准确度和重复性良好。进一步测定了3种禽类肠组织中微量金属元素含量, 鸡肠中6种金属元素含量从高到低依次为Ca>Fe>Zn>Mg>Mn>Cu; 在鸭肠中则为Ca>Zn>Mg≈Fe>Mn>Cu; 在鹅肠中则为Ca>Fe≈Zn>Mg>Mn>Cu。3种家禽肠组织中, 鸡肠的Fe、Mn和Cu元素的含量明显高于鸭肠和鹅肠, 大约高2~4倍, 而Ca含量则远低于鸭肠和鹅肠, 仅为两者的1/5~1/7, Mg和Zn的含量在3中家禽肠组织中相近。结论 鸡肠中除Ca元素外, 其余5种元素都高于或等于鸭肠和鹅肠, 因此在作为动物性中药材使用时, 不建议用鸭肠或鹅肠代替鸡肠。     

Multiplex real-time PCR for the detection and quantification of DNA from duck, goose, chicken, turkey and pork

Meat products made from liver of poultry like duck and goose are popular and often sold as specialities for high prices. As the prices for the basic raw material are high, fraud may be attractive for producers. To prevent consumers from fraud, official control authorities survey such products. In this work, a quantitative multiplex PCR was developed determining the proportion of DNA and meat fractions of turkey, chicken, duck, goose and pork. The precision and accuracy of the PCR system was investigated. To examine the possibility of determining the meat fractions according to the recipe, reference material was produced and different liver–meat products from the market were analysed. For major components, the measurement uncertainty revealed to be at 39 %. For minor components, it was estimated to be 124 %. The results showed that this pentaplex real-time-PCR system is suitable to control the meat properties of such products although measurement uncertainty may be high.     

Mitochondrial markers for the detection of four duck species and the specific identification of Muscovy duck in meat mixtures using the polymerase chain reaction

A polymerase chain reaction (PCR) assay for the qualitative detection of four duck species in meat mixtures, and a second PCR assay for the specific identification of Muscovy duck, have been developed based on oligonucleotide primers targeting the 12S rRNA mitochondrial gene. The specificity of both assays was tested against a wide range of animal species. The technique was applied to raw and sterilized muscular binary mixtures, with a detection limit that ranged from 0.1% to 1.0% (w/w). The short length (less than 100 bp) of the DNA fragments amplified with these primer pairs was found to be essential for the successful amplification in samples with highly degraded DNA, and consequently, it could be very useful in inspection programmes to enforce labelling regulation of heat and pressure-processed products, for which other methods cannot be applied.     

Combination of SYBR Green II and TaqMan Probe in the adulteration detection of Dendrobium devonianum by fluorescent quantitative PCR

‘Zipi Fengdou’ is a restorative food made of the stem of Dendrobium devonianum, Paxt., whose high commercial value presents the constant risk of adulteration with cheaper ‘Foudou’ products made from other Dendrobium species. Therefore, this study developed two assays capable of detecting D. devonianum based on SYBR Green II and TaqMan probe real‐time PCR. By performing the diagnostic real‐time PCR based on SYBR Green II, two DNA fragments (163 and 159 bp) were specifically amplified from the internal transcribed spacer (ITS) region of D. devonianum. The average cycle threshold (C_t) values of two D. devonianum samples collected from different Chinese provinces were shown to be 16.65 for ITS1‐4 and 16.38 for ITS2‐1, which were significantly (P < 0.001, SPSS) different from those of the reference Dendrobium species used as adulterants of ‘Zipi Fengdou’ (34.94 for ITS1‐4, 34.67 for ITS2‐1). Moreover, in the assay based on TaqMan probe real‐time PCR, two TaqMan probes were designed and tested for the quantitative detection of D. devonianum in commercial samples labelled as ‘Zipi Fengdou’. As a result, this assay specifically and sensitively distinguished the processed Fengdou’ sample of D. devonianum from those of adulterant Dendrobium species.     

Detection of chicken and turkey meat in meat mixtures by using real-time PCR assays

In this study, TaqMan-based real-time Polymerase Chain Reaction (PCR) techniques were developed for the detection of chicken and turkey meat in raw and heat-treated meat mixtures. Primers and TaqMan probe sets were designed to amplify 86 bp and 136 bp fragments for the chicken and turkey species, respectively, on the mitochondrial NADH dehydrogenase subunit 2 gene. In the results, it was possible to detect each species at the level of 0.1 pg template DNA with the TaqMan probe technique without any cross-reactivity with nontarget species (bovine, ovine, donkey, pork, and horse) while the detection level was 1 pg template DNA using conventional PCR. The TaqMan probe assays used in this study allowed the detection of as little as 0.001% level of both species in the experimental meat mixtures, prepared by mixing chicken and turkey meat with beef at different levels (0.001% to 10%). In conclusion, TaqMan probe assays developed in this research are promising tools in the specific identification and sensitive quantification of meat species even in the case of heat-treated meat products, and suitable for a rapid, automated, and routine analysis.     

Duplex PCR approach for the detection and quantification of donkey,horse and mule in raw and heat‐processed meat products

Donkey‐related products have been paid more attention for their high nutritional value to human beings. Due to donkey resource scarcity, coupled with gradually increasing market demand, adulterated donkey meat products with other low‐cost animal meat, especially with the similar species horse and mule, are often found in market. Therefore, detection of species fraud in donkey meat products is important for consumer protection and food industries. In this study, a simple and highly specific duplex PCR method, based on the simultaneous amplification of fragments of the mitochondrial ATP synthase subunit 8/6 and ND2, was developed and optimised for the identification of horse, donkey and mule species in raw and heat‐processed meat products. To the best of our knowledge, it was the first time for this strategy applied to these three genetically related animal meat products differentiation to date. The duplex PCR generated a 153‐bp and 83‐bp amplification products for horse and donkey, respectively. While for mule, both of the two length amplification products are appeared on the agarose gel. Target meat species could be detected at a level of 1%, and the results indicated that the duplex PCR assay could be used in the authentification of donkey‐related products with high specificity, cost‐effectiveness and simplicity.     

Properties of Three Sorghum Cultivars Used for the Production of Bili‐Bili Beverage in Northern Cameroon

The malting characteristics of sorghum malts produced locally in Cameroon for Bili‐Bili brewing were compared with those of malts produced in a laboratory. The analytical values of both malts were similar but the brewing potential of the laboratory malts were marginally better than those of the locally produced malts. Of the three cultivars examined, Madjeru had the lowest levels of β‐amylase, maltose levels and fermentability. The worts of the Madjeru filtered the slowest of the three malts. During malting β‐glucanase developed rapidly and development was temperature‐dependent.     

Extraction,optimisation and characterisation of phenolics from Thymus vulgaris L.: phenolic content and profiles in relation to antioxidant,antidiabetic and antihypertensive properties

The objectives of this study were to examine varying extraction conditions of Thymus vulgaris L. as related to phenolic content and profiles of the extracts and their antioxidant, antihypertensive and antidiabetic properties. Phenolics were extracted under various conditions pertaining to free and bound phenolics, solvent type and combination of extraction time and temperature, and these extracts were evaluated in terms of their antioxidant activities and inhibitory activities of angiotensin‐converting enzyme (ACE), α‐glucosidase and α‐amylase. The acetone–water solvent mixture (1:1; v/v) produced the extract with the greatest phenolic content, antioxidant activity and inhibitory activities of ACE and α‐glucosidase. The optimal extraction temperature for maximum phenolic content and antioxidant activity associated with methanol extraction was 60 °C, whereas a lower temperature at 40 °C was required to maximise inhibitory activities for ACE, α‐glucosidase and α‐amylase. An inverse relationship was seen between antioxidant and glucosidase inhibitory activities vs. the ACE and α‐amylase inhibitory activities, which suggests the need for extractions to be directed to specific bioactivities of thyme extracts. Generally, the results indicate major differences in phenolic profiles among the tested extraction conditions with thymol as the predominant phenolic seen in most extractions, while gallic acid, rosmarinic acid or diosmin also predominated in other extracts. Extracts with the same predominant phenolic compound and similar phenolic content showed major disparities in their ACE, glucosidase and α‐amylase inhibitory activities, indicating that the major phenolic profiles of thyme extracts may not be necessarily related to the degree of inhibition of ACE, glucosidase and α‐amylase enzymes.     

The Histochemical Location of Arabinosidase and Xylosidase in Germinating Wheat Grains

α‐L‐Arabinofuranosidase (EC 3.2.1.55) and β‐D‐xylanopyranosidase (EC 3.2.1.37) activities were detected in the endosperms of germinated, dried and sanded wheat grains using the fluorescence of 4‐methylumbelliferone released from appropriate synthetic substrates. The enzymes were not detected in ungerminated grains. Activities were first detected adjacent to the scutellum and advanced into the endosperm with increasing germination time, in some grains being slightly more advanced next to the aleurone layer. They were not detected in other tissues by this technique although analysis of extracts of the other tissues showed that they were present in greater amounts in the embryo and in the aleurone layer. The problems of interpretation caused by these findings are discussed.     

Carotenoids in pungent and non‐pungent peppers at various developmental stages grown in the field and glasshouse

Carotenoids in edible portions of plants can provide health benefits to humans. How growing conditions affect levels of carotenoids in pepper fruits as they mature is not well known. Five cvs of bell pepper (Bell Captain, Melody, North Star, Ranger, Red Beauty) and five cvs of pungent‐type peppers (Anaheim, Ancho, Cayenne, Pimento, Red Cherry) were grown in a glasshouse and in the field. Fruits were harvested at the green, turning (50% green) and mature red stages and analysed for levels of the carotenoids β‐cryptoxanthin, α‐carotene, β‐carotene, capsanthin, lutein and zeaxanthin and totals of these carotenoids. Levels of provitamin A: retinol equivalents (RE) were derived from levels of β‐cryptoxanthin, α‐carotene and β‐carotene. Levels of most carotenoids and RE were significantly higher in glasshouse‐grown plants, and most were higher in fruits at the red stage. Fruits of Ancho type had the most β‐cryptoxanthin, α‐carotene, β‐carotene, total carotenoids and RE, while fruits of Red Cherry type had the most capsanthin and zeaxanthin, and fruits of Bell Captain had the most lutein. Interactions of the main effects variables, ie location of production (field vs glasshouse), stage of development and cultivar, indicated differences in patterns of carotenoid levels and RE. The data indicated that growing conditions influenced carotenoid levels. The more consistent and protected conditions in the glasshouse may have caused carotenoid levels to be increased, especially at the red stage. Published in 2002 for SCI by John Wiley & Sons, Ltd     

Glycoalkaloids in potato tubers: the effect of variety and drought stress on the α‐solanine and α‐chaconine contents of potatoes

Six varieties of Solanum tuberosum L potato grown in the Bolivian highlands under drought stress, with and without irrigation, were analysed for their content of glycoalkaloids (GAs). The plant material consisted of three drought‐tolerant varieties from a local breeding programme (PROINPA), Potosina, Chapaquita and Pampeña, and three control cultivated varieties, Malcacho, Sani Imilla and Desiree, either susceptible or relatively tolerant to drought. α‐Solanine and α‐chaconine were quantified in both the peel and flesh of the tubers. A significant increase in GA concentration (α‐solanine + α‐chaconine) was observed under drought stress conditions in most varieties; average concentration increases of 43 and 50% were registered in the improved and control cultivars respectively. In all tested cultivars, however, the GA concentration remained lower than the recommended food safety level (200 mg kg⁻¹ fresh tubers). It ranged from 52.4 to 100 mg kg⁻¹ fresh tubers in the improved cultivars and from 55.6 to 122.3 mg kg⁻¹ fresh tubers in the controls. In the improved and control varieties the α‐solanine content averaged 42.6 and 35.4% of the total potato GAs respectively and was not significantly affected by drought stress, except in Desiree. In all conditions the peel contained the greatest proportion of total GAs. The hybrid variety Pampeña (new drought‐tolerant variety) contained the lowest amounts of GAs, which were lower than those of the control varieties, with and without irrigation. © 2000 Society of Chemical Industry     

Alterations of the Profiles of Iso‐α‐Acids During Beer Ageing,Marked Instability of Trans‐Iso‐α‐Acids and Implications for Beer Bitterness Consistency in Relation to Tetrahydroiso‐α‐Acids

Age‐induced decomposition of iso‐α‐acids, the main bittering principles of beer, determines the consistency of the beer bitter taste. In this study, the profiles of iso‐α‐acids in selected high‐quality top‐fermented and lager beers were monitored by quantitative high‐performance liquid chromatography at various time intervals during ageing. The degradation of the iso‐α‐acids as a function of time is represented by the ratio, in percentage, of the sum of the concentrations of trans‐isocohumulone and trans‐isohumulone to the sum of the concentrations of cis‐isocohumulone and cis‐isohumulone. This parameter is relevant with respect to the evaluation of bitterness deterioration in aged beers. Trans‐iso‐α‐acids having a shelf half‐life of less than one year proved to be significantly less stable than cis‐iso‐α‐acids, but it appears feasible to counteract degradation if a suitable beer matrix is available. The fate of the trans‐iso‐α‐acids in particular adversely affects beer bitterness consistency. In addition to using hop products containing low amounts of trans‐iso‐α‐acids, brewers may profit of the remarkable stability of tetrahydroiso‐α‐acids, even on prolonged storage, for the production of consistently bitter beers.