109 research outputs found
Immunogold Labeling of Milk Proteins at Transmission Electron Microscopy
No full textMilk intended for human consumption is subjected to technological treatments to ensure its safety and storage stability. These treatments deeply modify some of its structural and nutritional characteristics. Principal modifications involve proteins that partly adsorb onto the membrane of milk fat globules upon homogenization or whey proteins that undergo denaturation and aggregation during thermal treatments. Transmission electron microscopy is a powerful approach to investigate milk ultrastructure, due to its high-resolution power. Immunogold labeling of β-lactoglobulin and β-casein proteins represents a sophisticated approach to examine their structure and localization following technological processes such as homogenization and UHT treatment. However, liquid milk is a very challenging matrix because of its complex multiphasic nature. To preserve both ultrastructure and antigenicity, and to obtain an efficient labelling in liquid milk samples, some precautions shall be adopted in fixation, embedding, and labeling steps as here reported
Natural Cellulosic Material Characteristics: A Possibility to Develop Antimicrobial Active Fiber-based Packaging
No full textCoconut husk, rubberwood sawdust, and palm leaf base are cellulosic agricultural wastes that have potential to be processed to fiber as absorbing material. This study investigated characteristics (morphological, physiological properties, chemical composition, absorption capacity, and water absorption isotherms) of coconut, rubberwood, and palm fiber. Also, the study aimed to develop an antimicrobial sachet packaging to resist against foodborne pathogens (Listeria monocytogenes, Staphylococcus aureus, Salmonella spp., and Escherichia coli) by adding lime oil (LO) emulsion or Litsea cubeba (LC) oil at 50 to 700 μL into the material (1 g) before, and then dried and placed in the 1-L seal box. Results showed that among the three, coconut performed the best in terms of releasing the essential oil (EO) emulsion against bacteria. Coconut could adsorb and release volatile LO or LC at the lowest concentrations (LO, 500 μL/L; LC, 300 μL/L) to inhibit bacteria compared with the other fibers (700 μL/L) at 35 °C. Results indicated that coconut has a low water absorption rate, which influenced the faster adsorption of EO emulsion in the beginning of the process; therefore, using low concentrations of EO in coconut for bacterial inhibition is possible. Coconut contains 34.5% lignin, 68.7% holocellulose, 37.6% cellulose, and 31.2% hemicellulose. Coconut is suitable as an alternative to the biocomposite material in developing a new antimicrobial packaging design
The volcanology of Idunn Mons, Venus: The complex evolution of a possible active volcano
No full textIdunn Mons is a shield volcano located in the Imdr Regio large igneous rise, a Venusian equivalent to a hotspot geologic province on Earth. Recent studies using emissivity data from ESA's Venus Express Mission, together with experimental laboratory studies on the alteration of volcanic materials on Venus conditions, suggest that Idunn Mons is a possible site for very recent or even ongoing volcanic activity. In this work we carried out geologic mapping of Idunn Mons to characterize its materials and structures and to establish its geologic evolution. This study suggests that Idunn Mons is analogous to oceanic island volcanoes on Earth, with volcanic constructive phases that alternate with flank collapse episodes, resulting in its flat-topped summit morphology. These flank collapse events can be related to the intimate temporal and spatial relationship existing between Idunn Mons and Olapa Chasma, a rift that dominates the large igneous rise and relates to the volcano evolution, suggesting that this is not simply a candidate site for active volcanism but also for active tectonism
Ion-Exchange Chromatographic Method for the Determination of the Free Amino Acid Composition of Cheese and Other Dairy Products : an Inter-Laboratory Validation Study
No full textAlthough free amino acids (FAAs) represent a significant component of ripened cheeses and can provide useful information for their characterization, no inter-laboratory validated analytical method exists which allows a reliable comparison of data obtained by different laboratories and the adoption of quality control schemes based on FAA pattern. The objective of the present work was to test the effectiveness of an analytical protocol for the determination of the FAA composition of cheese and to verify the adequateness of this type of analysis for quality control procedures of Grana Padano PDO cheese as well as for research purposes. After an initial test to compare performances of ion-exchange chromatography (IEC) and HPLC techniques, an inter-laboratory collaborative study (seven laboratories, four samples) was organized to validate an IEC method with post-column ninhydrin derivatization and using l-norleucine as an internal standard. Determined amounts of individual FAA ranged from 8 to over 1380 mg/100 g cheese, with relative standard deviation of repeatability (RSDr) ranging from 0.5 to 4.6%, and relative standard deviation of reproducibility (RSDR) ranging from 1.3 to 9.9% for FAA concentrations over 100 mg/100 g. For lower concentrations, RSDr and RSDR were about thrice as high. On the basis of the results of this investigation, at present, the validated method is adopted as the official method for the determination of FAA patterns in the quality control of Grana Padano PDO cheese
Proteomics Parameters for Assessing Authenticity of Grated Grana Padano PDO Cheese: Results from a Three-Year Survey
No full textAssessing the authenticity of PDO cheeses is an important task because it allows consumer expectations to be fulfilled and guarantees fair competition for manufacturers. A 3-year survey was carried out, analyzing 271 samples of grated Grana Padano (GP) PDO cheese collected on the European market. Previously developed analytical methods based on proteomics approaches were adopted to evaluate the compliance of market samples with selected legal requirements provided by the specification for this cheese. Proteolysis follows highly repeatable pathways in GP cheese due to the usage of raw milk, natural whey starter, and consistent manufacturing and ripening conditions. From selected casein breakdown products, it is possible to calculate the actual cheese age (should be >9 months) and detect the presence of excess rind (should be <18%). Furthermore, due to the characteristic pattern of free amino acids established for GP, distinguishing it from closely related cheese varieties is feasible. Cheese age ranged from 9 to 25 months and was correctly claimed on the label. Based on the amino acid pattern, three samples probably contained defective cheese and there was only one imitation cheese. Few samples (9%) were proven to contain some excess rind. Overall, this survey highlighted that the adopted control parameters can assure the quality of grated GP
A fluorescence in situ staining method for investigating spores and vegetative cells of Clostridia by confocal laser scanning microscopy and structured illuminated microscopy
No full textNon-pathogenic spore-forming Clostridia are of increasing interest due to their application in biogas production
and their capability to spoil different food products. The life cycle for Clostridium includes a spore stage that can
assist in survival under environmentally stressful conditions, such as extremes of temperature or pH. Due to their
size, spores can be investigated by a range of microscopic techniques, many of which involve sample pretreatment.
We have developed a quick, simple and non-destructive fluorescent staining procedure that allows a
clear differentiation between spores and vegetative cells and effectively stains spores, allowing recovery and
tracking in subsequent experiments. Hoechst 34580, Propidium iodide and wheat germ agglutinin WGA 488
were used in combination to stain four strains of Clostridia at different life cycle stages. Staining was conducted
without drying the sample, preventing changes induced by dehydration and cells observed by confocal laser
scanner microscopy or using a super-resolution microscope equipped with a 3D-structured illumination module.
Dual staining with Hoechst/Propidium iodide differentiated spores from vegetative cells, provided information
on the viability of cells and was successfully applied to follow spore production induced by heating. Superresolution
microscopy of spores probed by Hoechst 34580 also allowed chromatin to be visualised. Direct
staining of a cheese specimen using Nile Red and Fast Green allowed in situ observation of spores within the
cheese and their position within the cheese matrix. The proposed staining method has broad applicability and
can potentially be applied to follow Clostridium spore behaviour in a range of different environments
The Geologically Supervised Spectral Investigation as a Key Methodology for Identifying Volcanically Active Areas on Venus
No full textCombining geologic mapping and stratigraphic reconstruction of lava flows at Sapas, Maat and Ozza Montes, three potentially young volcanic structures of Atla Regio on Venus, with analysis of the spectral signature (radar emissivity anomalies) characterizing each mapped flow, Brossier et al. (2021, https://doi.org/10.1029/2020je006722), conclude that some of the lava flows at Maat Mons may be geologically recent (∼25 Ma) (Smrekar et al., 2010, https://doi.org/10.1126/science.1186785; D'Incecco et al., 2017, https://doi.org/10.1016/j.pss.2016.12.002; Zolotov, 2018, https://doi.org/10.1515/rmg.2018.84.10; Brossier et al., 2020, https://doi.org/10.1016/j.icarus.2020.113693, 2021, https://doi.org/10.1029/2020je006722). The lava flows of Sapas and Ozza Montes are consistent with weathered lava flows forming chlorapatite and some perovskite oxides. We discuss the reasons why, besides the importance of the results they obtained, the methodology they used can be very valuable for future investigations with higher resolution datasets
Development of a HPLC method for the simultaneous analysis of riboflavin and other flavin compounds in liquid milk and milk products
No full textA high-performance liquid chromatography method with fluorescence detection was developed for the quantification of
riboflavin (RF), flavin mononucleotide (FMN), flavin adenine dinucleotide (FAD) and their photodegradation products,
lumichrome (LC) and lumiflavin (LF), in liquid milk and milk products. Both sample preparation and chromatographic separation were studied to avoid acidic conditions that proved to affect flavin stability and degrade FAD into FMN. The sample preparation includes centrifugal skimming and ultrafiltration steps and is suitable for routine application. Linear response was obtained for individual flavins in the respective concentration ranges of interest and relative standard deviation (RSD) was lower than 5%, except for FAD (RSD 11%). The recovery ranged between 80–100%. The proposed method proved to be suitable for assessing flavins in commercial liquid milk and fermented milk products, and for monitoring the degradation of FAD, FMN and RF and the formation of LF and LC in bottled milk exposed to light during shelf storage
The Young Volcanic Rises on Venus: a Key Scientific Target for Future Orbital and in-situ Measurements on Venus
No full textAbstract: A number of new Venus mission concepts are being currently evaluated for final approval, such as the NASA VERITAS and DAVINCI+, the Roscosmos-NASA Venera-D and the ESA EnVision proposals. These missions would analyze different aspects of the Earth’s twin planet: the chemistry and structure of its atmosphere, the spectral characteristics and composition of its surface, and its gravity anomalies. The wealth of high-resolution data to be produced by these future missions would likely shed new light on the major science questions. In this regard, one of the major debates concerns whether Venus underwent (and it is currently undergoing) through several episodes of abrupt and catastrophic resurfacing which rejuvenated its entire surface in a short amount of time, or its volcanism has been more steady and constant in time. Recent studies of Imdr Regio, one of the young volcanic rises, have provided hints indicating that volcanic as well as tectonic activity may be still ongoing in that area. The young volcanic rises are generated and supported by underlying active mantle plumes and can be considered as the some of the youngest geologic terrains of Venus. Studying how the rate and styles of volcanic and tectonic activities are evolving through time will tell us more about the interior structure of Venus, shedding some light on the major debate between catastrophic and equilibrium resurfacings. For this reason, we propose here the young volcanic rises, and in particular Idunn Mons of Imdr Regio, as potential target sites for future orbital and in-situ investigations. © 2021, Pleiades Publishing, Inc
Mechanisms of clostridium tyrobutyricum removal through natural creaming of milk: a microscopy study
No full textClostridium tyrobutyricum is the main spoilage agent of late blowing defect (LBD) in Grana Padano and Parmigiano-Reggiano cheeses; LBD is characterized by openings and holes and is sometimes accompanied by cracks and an undesirable flavor. Even a very few spores remaining in the cheese curd may cause LBD; thus, it is essential to eradicate them during milk natural creaming. By this process, most of the bacteria, somatic cells, and spores rise to the top of the milk, together with the fat globules, and are removed with the cream. Previous studies suggested that milk immunoglobulins mediate the interactions between fat globules and bacteria that occur upon creaming but no direct evidence for this has been found. Moreover, other physical chemical interactions could be involved; for example, physical entrapment of spores among globule clusters. To maximize the efficiency of the natural creaming step in removing Cl. tyrobutyricum,, it is essential to understand the nature of spore globule interactions. With this aim, raw milk was contaminated with spores of Cl. tyrobutyricum before going to creaming overnight at 8 degrees C, after which spore and bacteria removal was >90%. The obtained cream was analyzed by light interference contrast and fluorescence microscopy and by transmission electron microscopy (TEM). Results showed that most of the vegetative cells and spores, which were stained with malachite green before addition to milk, adhered tightly to the surface of single fat globules, the membranes of which appeared heterogeneous when stained with the fluorescent dye DilC(18)(3)-DS. Using the same dye, we observed transient and persistent interactions among globules, with formation of clusters of different sizes and partial coalescence of adhering membranes. Transmission electron microscopy examination of replicates of freeze-fractured cream allowed us to observe tight adhesion of spores to fat globules. Ultrathin sections revealed that this adhesion is mediated by an amorphous, slightly electron-opaque material, sometimes granular in appearance. Bacteria also adhered to different fat globules, linking them together, which suggests that adhesion was strong enough to maintain a stable contact. Although we cannot exclude physical entrapment of bacteria among fat globule clusters, we show for the first time that most of the bacteria are adhered to fat globules by an electron-opaque material whose nature has yet to be determined. Immunoglobulins are certainly the best candidates for adhesion but other compounds may be involved
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