麻痹性贝类毒素常规检测分析方法比较与 研究进展

麻痹性贝类毒素作为贝类产品中一种毒性最强、分布广泛的毒素,不仅严重威胁人们的身体健康,而且会造成相当大的经济损失。因此其监测检测方法的研究与改进一直是人们的研究热点。本文分析评述了麻痹性贝类毒素的三种常规检测分析方法的优缺点以及最新研究进展,并探讨了小白鼠生物法、免疫测定法和色谱联用技术作为主要的检测方法由于原理不同,结合不同的研究需求其应用的领域。其中,小白鼠生物测定法虽然概括毒性有效,但是其灵敏度低、误差大、并且需要大量活体动物而逐渐被色谱技术和免疫测定法所取代,此外,神经细胞分析法、毛细管电泳技术和表面等离子体共振传感器技术等方法也逐渐得到应用。不管怎样,这些方法由于需要专业人员、成本高等问题仍需进一步完善。     

超高效液相色谱-串联质谱法同时检测贝类中13种麻痹性贝类毒素

目的 建立超高效液相色谱-串联质谱法可以同时进行测定双壳贝类中13种麻痹性贝类毒素(paralytic shellfish poisoning toxins, PSTs)的方法。方法 用乙酸水溶液提取贝类中的PSTs,经乙酸乙酯除杂,然后用石墨化碳黑固相萃取柱净化,采用UPLC BEH Amide色谱柱 (100 mm×2.1 mm,1.7 μm)分离,电喷雾正、负离子多反应监测模式(MRM)同时检测,基质匹配曲线外标法定量。结果 13种PSTs的线性方程相关系数(r)均大于0.998,定量限为2 ~20 μg/kg,贻贝基质的平均回收率为92%~122%,牡蛎基质的平均回收率为105%~127%,扇贝基质的PSTs平均回收率为107%~144%,相对标准偏差均小于10%。将该方法应用于100份贝类样品中PSTs的检测,共有30份样品、5种PSTs检出,总毒性当量(STXeq)为10.0 ~159 μg/kg。结论 本研究方法灵敏度高,具有良好的重现性,可以准确定量定性13种PSTs ,适用于贝类中PSTs的日常监测。     

Tracing the origin of paralytic shellfish toxins in scallop Patinopecten yessoensis in the northern Yellow Sea

Some dinoflagellate species within the genera Alexandrium, Gymnodinium and Pyrodinium are well-known producers of paralytic shellfish toxins (PST), which led to many poisoning incidents around the world. In the northern Yellow Sea, an important mariculture zone for scallop Patinopecten yessoensis, PST have been frequently detected from scallops. However, there is little knowledge concerning PST-producing microalgae in this region so far. In cruises carried out in 2011 and 2012, scallop and phytoplankton samples were collected from the northern Yellow Sea. PST were detected from scallops by high-performance liquid chromatography with fluorescence detection (HPLC-FLD). Toxin content and profile were remarkably different among the four tissues, i.e. viscera, adductor muscle, mantle and gonad, suggesting apparent toxin transfer and transformation in scallops. Viscera always had the highest content of PST dominated by low-potency N-sulfocarbamoyl toxins C1 and C2, which closely resembled the toxin profiles of net-concentrated phytoplankton samples in spring. Based on the morphological features, cells of Alexandrium spp. in net-concentrated phytoplankton samples were picked out and a partial sequence of the large subunit ribosomal RNA gene (LSU rDNA) was amplified using a single-cell polymerase chain reaction (PCR) method. Cells of both toxic A. tamarense species complex and non-toxic A. affine were identified from the phytoplankton samples based on the partial LSU rDNA sequence information. According to these findings, it is implied that A. tamarense species complex is the major toxic species related to PST contamination in scallops of the northern Yellow Sea. The presence of both toxic and non-toxic Alexandrium spp. in this region requires for a species-specific method to monitor the distribution and dynamics of A. tamarense species complex.     

Antioxidant activity of hydrolysates obtained from scallop (Patinopecten yessoensis) and abalone (Haliotis discus hannai Ino) muscle

Scallop (Patinopecten yessoensis) and abalone (Haliotis discus hannai Ino) muscle were hydrolysed with commercially available food-grade proteases. The resulting hydrolysates showed DPPH and hydroxyl radicals scavenging abilities, reducing power, and ferrous ion chelating capacity. The antioxidant activities of hydrolysate of abalone foot muscle (HAFM) increased with increasing incubation time during the whole hydrolysis process in 180 min. Whereas, the antioxidant activities of hydrolysate of scallop adductor muscle (HSAM) increased at initial stage and peaked after 25-30 min of hydrolysis, and then gradually decreased thereafter. Compared with HAFM, HSAM with comparable hydrolysis time contained more free amino acids (FAA) and small-sized peptides (below 500 Da), which may account for the differences in antioxidant activities versus hydrolysis time curves of the two hydrolysates. The above results indicate that limited hydrolysis of proteins can increase their antioxidant activity, whereas extensive hydrolysis can decrease it.     

Effect of different air/steam convection cooking methods on turkey breast meat: physical characterization, water status and sensory properties

Turkey breast samples were cooked using a forced convection oven at three relative humidity levels (RH=8, 35 and 88%) at 100°C. Cooking parameters (temperature, cook value, and yield), textural and sensory properties as well as water status of the samples were evaluated. The application of different RH levels resulted in different cooking performances and cooked meat quality. Low steam cooking conditions (RH=35%) significantly increased cooking yield (7% higher than the high steam cooking), moisture content and water-holding capacity and had a positive effect on perceived tenderness, as shown by sensory analysis, where steam cooked samples were perceived as the most tender. The more mobile protons of (1)H T(2) (relaxing at times longer than 1s) in low steam samples were related to the higher perceived tenderness. Low steam cooking allowed for less water consumption, making this process an attractive cooking method as compared to high steam, as it also resulted in higher quality cooked turkey meat.     

Effect of steam explosion pretreatment on treatment with Pleurotus ostreatus for the enzymatic hydrolysis of rice straw

The effects of steam explosion (1.5 MPa, 1 min) on the treatment of rice straw with Pleurotus ostreatus were evaluated in terms of the change in composition of the components and the susceptibility to enzymatic hydrolysis. When rice straw was pretreated with a steam explosion prior to biological treatment, the treatment time required for obtaining a 33% net glucose yield was reduced to 36 days from 60 days. The reduction is probably due to loosening of networks of Klason lignin with sugar moieties and partial collapse of the structure during the biological treatment.     

Effect of steam treatment on soluble phenolic content and antioxidant activity of the Chaga mushroom (Inonotus obliquus)

The effect of steam treatment on free phenolic acids in Chaga mushrooms (Inonotus obliquus) was investigated. Untreated and steam-treated (120 °C, 3 h) samples of I. obliquus were extracted with organic solvents and free phenolic acid-containing fractions were isolated. Free phenolic acids were determined by LC/PDA (liquid chromatography/photodiode array), ESI LC/MS (electrospray ionisation liquid chromatography/mass spectrometry), and GC/MS (gas chromatography/mass spectrometry). After the steam treatment, the soluble phenolic content determined by modified Folin–Ciocalteu method was increased and antioxidant activity was enhanced, as confirmed by a DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging activity assay. The amounts of vanillic acid, protocatechuic acid, syringic acid, and 2,5-dihydroxyterephthalic acid were increased significantly as the result of the steam treatment, suggesting that the liberation of low molecular weight free phenolics was enhanced by the steaming process. Consequently, the radical scavenging activity was also significantly enhanced by free phenolics produced using this method.     

Polyamine determination in different strains of the yeast Debaryomyces hansenii by high pressure liquid chromatography

Polyamines (putrescine, spermidine and spermine) participate in many biochemical processes that are indispensable for cell differentiation and proliferation. In the present study, polyamine types were determined in 13 Debaryomyces hansenii strains isolated from different sources by high pressure liquid chromatography. Very low putrescine levels were observed in the strains DhhBCS007, DhfBCS001 and DhfBCS002. Spermidine and spermine were the most prevalent amines detected in all the yeasts, ranging from 7.71 to 18.42 mg/kg of spermidine in the strain L2 and 9.39–18.96 mg/kg for spermine in strain DhhCBS004. D. hansenii strain L2 and CBS004 isolated from citrus fruit and marine water, respectively, were the main polyamine-secreting yeasts. The results will contribute to our ability to select the most appropriate strains for use, as dietary complement (probiotic) in the animal food industry, including aquaculture.     

Effect of osmotic dehydration on Actinidia deliciosa kiwifruit: A combined NMR and ultrastructural study

The effects of individual osmotic dehydration processes (OD) on kiwifruit outer pericarp tissue were studied as reliant on treatment temperature (25, 35 and 45 °C) and extent (0–300 min). Macro (Low Frequency Nuclear Magnetic Resonance, LF-NMR), micro (Light Microscopy, LM) and ultrastructural (Transmission Electron Microscopy, TEM) measurements were performed to evaluate modifications of three cellular compartments, namely vacuole, cytoplasm – extracellular space and cell wall.     

Effect of different pasteurization conditions on bioactivities of Lupinus albus protein isolates

Lupin protein isolate was extracted following the procedure in European Patent (EP 1024 706 B1) in order to use lupin protein for food and pharmaceutical applications. The acid insoluble/neutral pH soluble protein isolate was pasteurized at 65-125 °C for 10-1000 s. The objective of this study is finding out reasonable pasteurization condition for food use, or for good bioactivities like radical scavenging, angiotensin converting enzyme inhibition, and bile acid binding activity. Pasteurization at 65 °C for 10 s did not reduce the microbial count of the protein sufficiently for use in foods. The chemical composition of lupin protein isolates had no change by various pasteurization. The angiotensin converting enzyme inhibition decreased and the DPPH radical scavenging capacity increased after high temperature treatment at 125 °C. The sodium cholate binding capacity was not affected by tested conditions. Pasteurization at higher temperature is useful for producing selective bioactive fractions with suitable microbiological properties.     

Effect of three stored-grain fungi on the development of Typhaea stercorea

This study examined development times and ovipositional preference of hairy fungus beetles (Typhaea stercorea [L.] Col: Mycetophagidae), when reared on pure cultures of Aspergillus flavus Link, Eurotium rubrum König, Spieck and Bremer, and Penicillium purpurogenum Stoll., and the ability of hairy fungus beetles to develop in the presence of high levels of aflatoxin when fed A. flavus grown on coconut agar medium. Results indicate that hairy fungus beetles can complete their life cycle when fed these mold species grown on a defined medium in pure culture. Developmental times were shortest and females laid more eggs on pure cultures of A. flavus compared to E. rubrum, and P. purpurogenum. Lastly, we tested to see the effects of aflatoxin on hairy fungus beetle development. Hairy fungus beetles can complete their life cycle while feeding on a fungal culture producing high levels of aflatoxin. The results suggest that the mold species in the grain mass can influence insect developmental rates and thus population growth rates.     

Effect of antioxidants and competing mycoflora on Fusarium verticillioides and F. proliferatum populations and fumonisin production on maize grain

This study was carried out to determine the temporal effect of the antioxidants butylated hydroxyanisol (BHA) and propyl paraben (PP) at doses of 500 and 1000 μg/g on the growth of Fusarium verticillioides and F. proliferatum inoculated on natural maize grain in the presence of the competing mycoflora and fumonisin production at 0.98 and 0.95 water activity (a_w) over a 28-day storage period. The reduction in the log colony forming units (CFU) of Penicillium, Aspergillus and Fusarium populations was 10-100 fold depending on dose of BHA or PP, a_w and time. However, the populations of all three groups were higher at 0.98 a_w than 0.95 a_w. BHA at 500 μg/g and 0.95 a_w reduced the fumonisin content by 82% after 7-14 days incubation, but at the end of the experimental period the reduction was only 32%. A higher reduction in the level of fumonisin produced (77%) was achieved with BHA at 1000 μg/g after 28 days. PP at 500 and 1000 μg/g decreased fumonisin production throughout the incubation period in the drier treatment, but at 0.98 a_w control of toxin production was only achieved after 7-14 days. The reduction in the fumonisin levels could be due to the combined effect of antioxidants, and the competing mycoflora, mainly Aspergillus and Penicillium species.     

Effect of damaged starch on acrylamide formation in whole wheat flour based Indian traditional staples, chapattis and pooris

Variation in acrylamide content of two Indian traditional products, chapatti and poori was observed with respect to the damaged starch content in whole wheat flour of different wheat varieties from which these products were prepared. Wheat cultivar ‘lokwan’ was milled by altering mill aperture, feed rate and moisture content to obtain whole wheat flour with damaged starch contents ranging from 6.23% to 28.12%. Acrylamide content of the chapatti and pooris prepared from such flours ranged from 12.5 to 65.5 μg/kg in chapatti, and 25.5 to 130.5 μg/kg in pooris. Impact of several additives showed 10 μmol/g flour citric acid, and 100 μmol/g flour calcium chloride to reduce acrylamide in pooris by approximately 54% and 72%, respectively, without altering the sensory analysis of the products.     

Accumulation of vasicine and vasicinone in tissue cultures of Adhatoda vasica and evaluation of the free radical-scavenging activities of the various crude extracts

The indigenous medicinal plant, Adhatoda vasica (L.) Nees. (Acanthaceae), commonly known as vasaka, is used as a herbal remedy for allergen-induced bronchial obstruction, asthma, and tuberculosis and possesses hepatoprotective activity. This plant is a natural source of vitamin C. Tissue cultures of A. vasica, initiated on Murashige and Skoog’s medium supplemented with various plant growth regulators, showed the presence of alkaloids, vasicine and vasicinone. Water extracts of shoot cultures contained high levels of these alkaloids. The vasicine and vasicinone contents in these extracts were 5.98% and 5.2% of dry weight and the water extracts of the selected elite parent plant contained 3–4% dry weight of vasicine. The methanolic extracts of the parent plant and shoot cultures showed quantitative differences in the level of both vasicine and vasicinone. Maximum free radical-scavenging activity of DPPH radicals was observed in the water extracts.     

Effect of Pisum sativum fractions on the mortality and progeny production of nine stored-grain beetles

Yellow field pea (Pisum sativum L.) fractions that were mainly protein (50%), fibre (90%) or starch (85%) were obtained from a commercial pea mill and mixed with wheat kernels or wheat flour. Based on the mortality and the number of offspring produced, protein-rich pea flour was more toxic than fibre, which was more toxic than starch. For the protein-rich pea flour mixed with wheat kernels, the most sensitive insects were Sitophilus oryzae (L.), Sitophilus zeamais Motschulsky and Sitophilus granarius (L.), followed by Cryptolestes ferrugineus (Stephens) which was more sensitive than Tribolium castaneum (Herbst) and Rhyzopertha dominica (F.). For the protein-rich pea flour mixed with wheat flour, Cryptolestes pusillus (Schönherr) was most sensitive, followed by C. turcicus (Grouvelle) and T. confusum (Jacquelin du Val), with T. castaneum being the most resistant. Although protein-rich pea flour did not kill adults to a great extent when mixed with flour, it reduced offspring production significantly. Again C. pusillus was the most sensitive, followed by T. confusum, with T. castaneum offspring being the most resistant. The insecticidal activity of pea fractions decreased after treated wheat kernels were held at 30 °C, 70% r.h. for 8 months. The potential of using pea fractions to control stored-product insects is discussed.     

Short communication: Effect of homogenization on heat inactivation of Mycobacterium avium subspecies paratuberculosis in milk

Mycobacterium avium ssp. paratuberculosis (MAP) can be present in cow milk and low numbers may survive high-temperature, short-time (HTST) pasteurization. Although HTST treatment leads to inactivation of at least 5 log₁₀ cycles, it might become necessary to enhance the efficacy of HTST by additional treatments such as homogenization if the debate about the role of MAP in Crohn’s disease of humans concludes that MAP is a zoonotic agent. This study aimed to determine whether disrupting the clumps of MAP in milk by homogenization during the heat treatment process would enhance the inactivation of MAP. We used HTST pasteurization in a continuous-flow pilot-plant pasteurizer and evaluated the effect of upstream, downstream, and in-hold homogenization on inactivation of MAP. Reduction of MAP at 72°C with a holding time of 28 s was between 3.7 and 6.9 log₁₀ cycles, with an overall mean of 5.5 log₁₀ cycles. None of the 3 homogenization modes applied showed a statistically significant additional effect on the inactivation of MAP during HTST treatment.     

Effectiveness of commercial household steam cleaning systems in reducing the populations of Listeria monocytogenes and spoilage bacteria on inoculated pork skin surfaces

In a previous study conducted in our laboratory, a commercial household steam cleaner was found to be effective in reducing the naturally occurring bacterial populations on 72 beef and 72 hog carcasses processed by four small and very small meat processing plants. The goals of this study were to determine the maximum levels of bacterial reduction caused by treatments using the steam cleaner, and to compare the efficacy of this cleaner with the efficacies of two other commercial household steam cleaning systems in reducing bacterial populations on the surface of pork skin artificially inoculated with ca. 7.61 or of Listeria monocytogenes. The contaminated pork skin samples were treated with the three stream cleaners for 30-180 s in 30 s intervals, and assayed for the populations of L. monocytogenes as well as total aerobic and thermoduric bacteria. The application of steam significantly reduced the population of L. monocytogenes (7.61-), as well as total aerobic (5.68-) and thermoduric (6.12-) bacteria on the surface of pork skin (P?0.05). Significant differences in microbial reductions were observed between different inoculation levels, treatment times, and types of cleaning systems used in the study (P?0.05).     

Effect of wood ash and conidia of Beauveria bassiana (Balsamo) Vuillemin on mortality of Prostephanus truncatus (Horn)

A series of experiments was carried out to investigate the effect of treating maize with wood ash and entomopathogenic fungus on the mortality of the larger grain borer Prostephanus truncatus. Jars of maize were treated with ash and/or conidia of Beauveria bassiana at doses of 0.0005, 0.005, 0.05 and 0.2 g conidia/g ash/100 g maize. Adult P. truncatus were placed on the maize and numbers of live and dead insects were assessed weekly.Ninety-five per cent mortality of P. truncatus was observed after 1 week and 100% mortality after 2 weeks in maize treated with the highest dose of conidia with ash (0.2 g/g). Mortality of P. truncatus in all ash with conidia treatments was significantly higher than untreated controls over a 4-week period, except the lowest dose of conidia at week 4. The three highest concentrations of conidia per gram of ash resulted in significantly (1% level) higher mortality of P. truncatus than ash alone.In an experiment to investigate the possible synergy of ash and conidia, there were no significant differences in mortality of P. truncatus between treatments with the same concentration of conidia regardless of whether the conidia were mixed with ash or applied alone. Larval populations of P. truncatus were observed in all treatments without ash, but only one larva was observed in one replicate of a treatment containing ash suggesting that ash has an important effect in preventing the establishment of a second generation of insects.     

Effect of chitin on the antagonistic activity of Rhodotorula glutinis against Botrytis cinerea in strawberries and the possible mechanisms involved

The influence of chitin on the efficacy of Rhodotorula glutinis in controlling postharvest grey mould of strawberries and the possible mechanisms involved were investigated. The results showed that the antagonistic activity of R. glutinis harvested either from the culture media of NYDB amended with chitin at 0.5% or from the culture media in which chitin was the sole carbon source (NYCB) was improved greatly compared with that without chitin. The application of R. glutinis cultivated in the culture media of the chitin-supplement (0.5%) induced higher β-1,3-glucanase activity and reduced more MDA content of strawberries compared with that R. glutinis cultivated in the NYDB. Moreover, the control efficacy of the cell-free filtrate of the chitin-supplement culture media (0.5%) and NYCB were higher than that of cell-free culture filtrates of NYDB in 2 days incubation, with the associated high level of chitinase activity.