Freeze-dried Material Research Articles

Celery (Apium graveolens L.) parenchyma cell walls examined by atomic force microscopy: effect of dehydration on cellulose microfibrils.

Atomic force microscopy (AFM) was used to image celery (Apium graveolens L.) parenchyma cell walls in situ. Cellulose microfibrils could clearly be distinguished in topographic images of the cell wall. The microfibrils of the hydrated walls appeared smaller, more uniformly distributed, and less enmeshed than those of dried peels. In material that was kept hydrated at all times and imaged under water, the microfibril diameter was mainly in the range 6-25 nm. The cellulose microfibril diameters were highly dependent on the water content of the specimen. As the water content was decreased, by mixing ethanol with the bathing solution, the microfibril diameters increased. Upon complete dehydration of the specimen we observed a significant increase in microfibril diameter. The procedure used to dehydrate the parenchyma cells also influenced the size of cellulose microfibrils with freeze-dried material having larger diameters than air-dried material.

The effect of drying methods on viscoelastic behaviour of dehydrated fruits and vegetables

The effect of drying methods on the rheological behaviour of dehydrated apple, banana, carrot and potato was examined by uniaxial compression tests on cylindrical specimens. Samples were dehydrated using four different drying methods: osmotic, conventional, vacuum and freeze drying. After drying samples at varying final moisture, the contents were tested for compressibility using pressures ranging from 0.02 to 8 kg kg - db. A simple mathematical model was used to describe the viscoelastic behaviour of the examined materials. Four parameters with physical meaning were incorporated in the model: the maximum stress (σ max ), the maximum strain (∈ max ), the elastic parameter (E) and the viscoelastic exponent (p). It was shown that all the parameters were dependent on both the drying method and the material. Osmotic dehydration seems to increase the viscous nature of fruits and decrease their elasticity, while freeze-dried materials seem to have the most elastic structure.

Moisture sorption isotherm characteristics of plantain ( Musa, AAB)

Moisture sorption isotherms of fresh, pre-treated and freeze-dried plantain, at 40°C, 50°C and 60°C, were constructed using the static gravimetric method. The pre-treatment involved blanching and infusion in 40° Brix sucrose at 4°C for 16 h. The isotherms of the fresh plantain were of BET type II, while those of the freeze-dried samples were BET type I. Hysteresis was observed between the adsorption isotherm of the freeze-dried plantain and the desorption isotherm of the fresh samples. At low values of a w, below 0.40, the moisture contents of the pre-treated samples were lower than that of the fresh plantain, at corresponding values of a w. However, above a w 0.50 the reverse applied. In both desorption and adsorption an increase in temperature resulted in lower equilibrium moisture contents at corresponding values of a w. The monolayer moisture contents of the moist-infused and freeze-dried samples were lower than those of the fresh material. Of the five models tested the Henderson, S. M. (1952, Agricultural Engineering 33, 29–32) and GAB (1981) versions fitted best to the isotherms of the fresh material. The Iglesias & Chirife model (1978) was the best fit to the isotherm of the infused material. The isosteric heat of sorption for the fresh plantain, ranged from 47.4 kJ/g mol at 18% moisture, dry solids basis, to 73.2 kJ/g mol at 2% moisture, dry solids basis. The comparable range for the freeze-dried material was 42.2–635 kJ /g. mol.

Extraction of pigments and fatty acids from the green alga Scenedesmus obliquus (Chlorophyceae)

In this paper, the efficiency of pigment and fatty acid extraction from resistant algae using Scenedesmus obliquus as an example was examined. We found that adding quartz sand and solvent to freeze-dried algal material and subsequent extraction in an ultrasound bath for 90 min at 4C resulted in excellent extraction of these compounds. This extraction method was compared with a method regularly used for extraction of fatty acids and pigments, i.e. addition of solvents to algal material with subsequent incubation. Our extraction using the ultrasound and sand method was about twice as efficient as this method for both pigments and fatty acids. The ultrasound method is simple, extracts over 90% of the different substances in one step and conserves the relationships of pigments and fatty acids. In addition, no alteration- or breakdown products were observed with the new method. Thus, this method allows accurate quantitative extraction of both pigments and fatty acids from Scenedesmus obliquus and other algae. The method was also been found to be as effective for Cryptomonas erosa(Cryptophyceae), Cyclotella meneghiniana(Bacillariophyceae), Microcystis aeruginosa(Cyanophyceae), and Staurastrum paradoxum (Chlorophyceae, Desmidiaceae) and is thus applicable to a wide spectrum of algae.

Evaluation of methods for measuring polyphenols in conifer foliage

There is a resurgence of interest in the quantification of polyphenols in plant tissues because of their presumed ecological importance in plant–litter–soil and plant–animal interactions. The influence of sample preparation, extracting solvent, foliage quality, and assay method was investigated for the quantification of total phenols and condensed tannins in conifer foliage. Our results suggest that it is not possible to recommend a single optimal protocol for quantification of total phenol and condensed tannin fractions from plant materials. In general, the use of aqueous acetone (50–70% v/v) with freeze-dried materials gave the highest recovery. The Folin-Ciocalteau method for total phenols and the butanol–HCl hydrolysis method for condensed tannins appear superior to other common assays tested. There were large differences (1.4–2.2 times) in the reactivity of purified condensed tannins among species, indicating the importance of an appropriate standard for polyphenol quantification. A solid-state 13C NMR method with an improved "interrupted decoupling" pulse sequence yielded the highest concentrations for condensed tannins. Assuming that 13C NMR provides an accurate measure of total condensed tannin, the other extraction/assay methods used in this study recovered 50–86% of the condensed tannin fraction. The recovery rate is correlated with the nitrogen content of the foliage, which suggests that the formation of protein–tannin complexes may limit the extractability of condensed tannins. While 13C NMR condensed tannin values may give the best value for total condensed tannin concentrations, the water-soluble fraction may have the greatest physiological and/or ecological significance.

The Impact of the Character of Natural Organic Matter in Conventional Treatment with Alum

The objective of this study was to determine if the removal of NOM in reservoir waters in conventional treatment with alum is limited by the character of the NOM. A sequential jar test procedure, which included five treatment steps was employed to study the character of the NOM which could not be removed by flocculation/sedimentation. The NOM in the raw and treated waters was characterised by techniques including dissolved organic carbon (DOC), UV absorbance (UVA), high performance size exclusion chromatography (HPSEC), pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) and diffuse reflectance Fourier transform infrared spectroscopy (DRIFT). HPSEC analysis of the reservoir waters from three sources indicated that the organic fraction remaining after alum treatment was of lower molecular weight than that in the original raw waters. Pyrolysis of freeze dried material (FDM) from one raw water source (Hope Valley Reservoir) and following treatment with a high alum dose at pH 5 (coagulated and non coagulated material) gave by-products that indicated the presence of proteins, polyhydroxyaromatics and polysaccharides.

Physical state of l-histidine after freeze-drying and long-term storage

Liquid samples of l-histidine of varying pH values and mixed with salt, metal ions, polysorbate 80 and sucrose have been analysed by differential scanning calorimetry to evaluate the influence of these additives on the glass transition temperature and crystallisation of l-histidine during freezing and thawing. l-Histidine solutions of varying pH were freeze-dried with and without a thermal cycle and the physical state of the freeze-dried cakes, following long-term storage, were studied by powder X-ray diffraction. Amorphous l-histidine crystallised when it was exposed to moisture, and the identity of the crystalline materials is reported. The crystallisation of l-histidine during freezing and thawing is dependent on the pH of the solution and is shown to be at a minimum at pH 6, which coincides with the p K a of the imidazoline function. Sucrose inhibited the crystallisation of l-histidine during thawing, while sodium chloride or polysorbate 80 did not. The addition of metal ions (Ca 2+ and Mg 2+) up to 10% (w/w) did not depress the glass transition temperature significantly, while the addition of Zn 2+ increased it. The physical state of l-histidine after freeze-drying is shown to be dependent on both the pH of the solution and the freezing cycle. The risk of crystallisation of amorphous l-histidine is low if the freeze-dried material is protected from moisture.

Thermal transitions in freeze-dried carrot and its cell wall components

Differential scanning calorimetry (DSC) was used to measure the glass transition temperature, T g and a sub- T g event in freeze-dried carrot material and different carrot cell wall components, at moistures ranging from 0% to 20% (w.w.b.). Two glass transition temperatures were detected in the freeze-dried carrot material associated with two phases: a sugar-rich phase and a cell wall-rich phase. The water distribution in the different phases is also important and sorption isotherms of freeze-dried carrot and different cell wall components were determined and compared with published results produced on sugar, pectins and cellulose. For the insoluble carrot cell wall materials, a single T g was detected which increased in the order: a Ca 2+ bound pectin-free residue, an esterified pectin-free residue and a cellulose-rich residue. In all cases T g increased with decreasing moisture. Additionally, a sub- T g endothermic event was observed in all the materials which disappeared on rescanning, consistent with results published on ageing of other biopolymers. The T g of the different cell wall residues was modelled, using the Gordon–Taylor and Kwei equations. The latter showed that water–biopolymers interactions are less prominent in the cellulose-rich cell wall residue, shown by a negative value of q.

The pharmaceutical exploration of cold water ascidians from the Netherlands: a possible source of new cytotoxic natural products

Six ascidian species from the Dutch North Sea coast were screened for cytotoxic activity. Freeze-dried biological material was extracted with solvents of different polarity followed by determination of the cytotoxicity. The most active extracts were further separated using different chromatographic techniques. The microculture tetrazolium (MTT) assay was used to determine the cytotoxicity against two human tumor cell lines: COLO 320 (a colon adenocarcinoma) and GLC 4 (a small cell lung carcinoma). The two cell lines were selected for their different response towards known cytostatics. GLC 4 is sensitive and COLO 320 is resistant to most of the known cytostatics. Three of the species tested yielded interesting fractions. From the in colonial Didemnum lahillei we have isolated a compound which is more active against the COLO 320 cell line (IC 50:33 μg ml −1) than the GLC 4 (IC 50:49 μg ml −1). The structure is currently elucidated. Another colonial species, Aplidium glabrum, yielded a very cytotoxic fraction, with an IC 50 of 5 μg ml −1 against the COLO 320 cell line. From our results it can be concluded that the North Sea could be another interesting source of new compounds with pharmaceutical potential.

The impact of the character of natural organic matter in conventional treatment with alum

The objective of this study was to determine if the removal of NOM in reservoir waters in conventional treatment with alum is limited by the character of the NOM. A sequential jar test procedure, which included five treatment steps was employed to study the character of the NOM which could not be removed by flocculation/sedimentation. The NOM in the raw and treated waters was characterised by techniques including dissolved organic carbon (DOC), UV absorbance (UVA), high performance size exclusion chromatography (HPSEC), pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) and diffuse reflectance Fourier transform infrared spectroscopy (DRIFT). HPSEC analysis of the reservoir waters from three sources indicated that the organic fraction remaining after alum treatment was of lower molecular weight than that in the original raw waters. Pyrolysis of freeze dried material (FDM) from one raw water source (Hope Valley Reservoir) and following treatment with a high alum dose at pH 5 (coagulated and non coagulated material) gave by-products that indicated the presence of proteins, polyhydroxyaromatics and polysaccharides.

Determination of phenolic compounds in olives by reversed-phase chromatography and mass spectrometry

A method based on extraction from freeze-dried material and clean up by solid-phase extraction was optimized for recovery of phenolic compounds from olive fruit. The extracted compounds were characterised by reversed-phase liquid chromatography using both ultraviolet, fluorescence and electrospray ionization mass spectral detection. Using this approach, oleuropein was confirmed as the major phenolic in olive fruit. Other compounds whose presence was confirmed include tyrosol, syringic, ferulic and homovanillic acids, quercetin-3-rhamnoside, ligstroside and isomers of verbascoside. Elenolic acid and its glucoside, which are not phenolic but are closely related, were also identified in sample extracts.

A proline-rich peptide originating from decomposing mangrove leaves is one natural metamorphic cue of the tropical jellyfish Cassiopea xamachana

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 183:115-124 (1999) - doi:10.3354/meps183115 A proline-rich peptide originating from decomposing mangrove leaves is one natural metamorphic cue of the tropical jellyfish Cassiopea xamachana J. Fleck1,*, W. K. Fitt2, M. G. Hahn3 1Lehrstuhl für Spezielle Zoologie, Ruhr-Universität, D-44780 Bochum, Germany 2Institute of Ecology, University of Georgia, Athens, Georgia 30602-2602, USA 3Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia 30602-4712, USA *E-mail: juergen.fleck@ruhr-uni-bochum.de ABSTRACT: Planula larvae of the scyphozoan Cassiopea xamachana settle and metamorphose on degrading mangrove leaves of Rhizophora mangle that lie submerged in shallow water mangrove ecosystems. Our prior study (Fleck & Fitt 1999; J Exp Mar Biol Ecol 234:83-94) indicated that marine bacteria are involved in the release of at least 1 peptidic compound from such leaves. The goal of our present study was to isolate and purify at least 1 natural peptidic cue originating from deteriorating leaves by means of ultrafiltration, gel filtration and reversed phase HPLC and subsequently obtain characteristic data of this cue. The ultrafiltrate (<=10 kD) of the homogenate of decaying mangrove leaves was subjected to gel filtration on a Sephadex G 25 column, resulting in 3 fractions which were tested for their capacity to induce metamorphosis of planula larvae in bioassays performed in the laboratory. Fraction I (>=5 kD) was most effective in inducing metamorphosis of 75% of planulae at 1 mg freeze-dried material ml-1 seawater within 24 h. Fractions II and III (both <=5 kD) resulted in metamorphosis of only 1% of larvae or less within 72 h when applied at 5 mg ml-1. Isochratic HPLC separation of Fraction I with 24% methanol yielded 2 biologically active fractions. One fraction (A/B), which induced 47% of the larvae to metamorphose at 0.9 mg lyophilized material ml-1 seawater within 24 h, consisted of a mixture of at least 2 subfractions and was not further analyzed. The other fraction (C) effected metamorphosis of 85% of larvae at a concentration of 0.5 mg ml-1 within 24 h. Matrix-assisted laser desorption ionization (MALDI) mass spectrometry of this fraction revealed a molecular weight of approximately 5.8 kD. Automated amino acid analysis showed that Fraction C was rich in proline (ca 44%) and glycine residues (ca 16%), corresponding to characteristic proline-rich cell wall proteins of plants. Automated sequencing of the natural inducer failed due to a blocked amino terminus. The results of our present study suggest that metamorphic inducers for C. xamachana may emerge nonspecifically as a byproduct of bacterial degradation of deteriorating, proteinaceous plant tissue in their habitat. KEY WORDS: Natural metamorphic inducer · Cnidaria · Peptides · Settlement · Scyphozoa · Mangrove leaves · Proline-rich proteins Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 183. Publication date: July 06, 1999 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1999 Inter-Research.

Scintigraphic evaluation of healing response after heterograft usage for alveolar extraction cavity

Objective. Reconstruction of bone defects remains an important problem in oral and maxillofacial surgery. Restoration of defect sites with various grafting materials is a valuable approach to the solution of this problem. The aim of this study was to evaluate the effects of the use of heterografts on osteoblastic activity by means of a radionuclide technique. Study design. The postextraction alveolar cavities of impacted mandibular third molars on 22 patients were used as a healing model for this study. Granulated freeze-dried heterograft material of bovine origin was used on 11 patients; the other 11 patients constituted a control group. On each patient, three-phase bone scans were performed on postoperative days 7 and 28. Results. Although dynamic and blood pool studies showed similar patterns with respect to the mean values of asymmetry ratios of operation sites to the contralateral sides for the 7th- and 28th-day scans, static-phase bone scans revealed that healing response through osteoinduction was more prominent in the study group than in the control group. A significant increase in the mean value of the ratio from the first scan to the second was observed on static images in the study group (first scan, 1.6 ± 0.2; second scan, 2.0 ± 0.5; p < 0.05). However, the same ratio failed to show any significant change in the control group (first scan, 1.5 ± 0.2; second scan, 1.5 ± 0.3; p > 0.05). Conclusion. Static-phase bone scintigraphy showed that when freeze-dried heterograft material is used to fill alveolar extraction cavities, it stimulates osteoblastic activity, which in turn leads to acceleration of the healing process and helps to maintain the linearity of bony structure. Moreover, radionuclide study can be used to evaluate the viability of freeze-dried heterografts in the 4th postoperative week, at which time no additional increase in perfusion resulting from surgical trauma was found in our series.

Reversed-Phase HPLC following Thiolysis for Quantitative Estimation and Characterization of the Four Main Classes of Phenolic Compounds in Different Tissue Zones of a French Cider Apple Variety (Malus domestica Var. Kermerrien)

Phenolic compounds, which are present in the epidermis zone, parenchyma zone, core zone, and seeds of fruit (Malus domestica var. Kermerrien), were extracted from freeze-dried material by three successive solvent extractions. The dry methanol extract and the dry aqueous acetone extracts were analyzed using reversed-phase HPLC coupled with diode array detection following thiolysis to quantify phenolic compounds according to their classes (hydroxycinnamic acid derivatives, flavan-3-ols, flavonols, and dihydrochalcones). The method is suitable for the determination of the relative proportions of the different classes of polyphenols and provided information on the constitutive units and the average degree of polymerization of oligomeric and polymeric procyanidin structures. Results showed that procyanidins are the predominant phenolic constituents in cider apple fruits, much of them corresponding to highly polymerized structures. Keywords: Apple; phenolics; procyanidins; cider; HPLC; thiolysis

Effect of freeze-drying conditions on shrinkage and porosity of dehydrated agricultural products

Structural properties such as particle density, bulk (or apparent) density and porosity of apple, banana, carrot and potato were investigated after freeze-drying under various drying conditions. The materials were freeze-dried at various pressures, to achieve sample temperature ranging between −50 and −5 °C. For temperatures above the glass transition temperature of the concentrated amorphous solution ( T′ g = −45 ° C), the freeze-dried materials decreased in size. The bulk density of the freeze-dried materials was increased with temperature and an exponential equation was used to express this influence. The final porosity decreased as the sample temperature increased for all the materials examined, ranging between 70 and 95%. The final porosity was related to the complex viscosity of frozen apple and potato which decreased linearly as the temperature increased in the temperature range examined.

Quantitative analysis of flavonols, flavones, and flavanones in fruits, vegetables and beverages by high-performance liquid chromatography with photo-diode array and mass spectrometric detection

A high-performance liquid chromatographic (HPLC) separation method with photo-diode array (PDA) and mass spectrometric (MS) detection was developed to determine and quantify flavonols, flavones, and flavanones in fruits, vegetables and beverages. The compounds were analysed as aglycones, obtained after acid hydrolysis of freeze-dried food material. Identification was based on retention time, UV and mass spectra by comparison with commercial standards, and the UV peak areas were used for quantitation of the flavonoid contents. Examples of HPLC–MS analyses of orange pulp, tomato, and apple are presented. The method has been used to screen foods on the Danish market, and the contents of flavones, flavonols, and flavanones were measured.

Comparison of some additives used in the preparation of freeze-dried lemon juice candidate reference materials

The stability, storage, and distribution of certified reference materials which consist of liquid or frozen fruit juices is rather problematic. As a better alternative a stable orange juice powder has been obtained by freeze-drying to a moisture content below 0.4%. However, freeze-drying lemon juices resulted in unstable materials which collapsed into lumps after standing some weeks in brown bottles under argon. An additive was sought which can be used to obtain stable lemon juice powders without influence on important analytical parameters as amino acids, sugars, organic acids, minerals and flavanone glycosides. The additives pectin, hydroxy ethylcellulose, and hydroxypropyl methylcellulose were examined. Powders containing pectin quickly showed a loss of structure (collapse) and resulted in non-acceptable changes in amino acids, sugars or minerals compared to the original lemon juice. The addition of up to 3% hydroxypropyl methylcellulose seemed more promising, although some minor changes in the sugar and sodium concentration occurred.

Hepatotoxic microcystins and neurotoxic anatoxin-a in cyanobacterial blooms from Korean lakes

Cyanobacterial bloom samples were collected in the warm season during 1992–1995 from the 12 lakes in Korea. Six species each of Microcystis and Anabaena, and two of Oscillatoria were identified in these lakes. The cyanotoxins of 47 samples collected from the lakes were identified as microcystins-RR, -YR, -LR; desmethyl-7-microcystin-LR (7-DMLR), plus anatoxin-a. Microcystins were the main components of these cyanotoxins, while anatoxin-a was detected in samples from a few lakes. Thirty-four of the 47 samples, included microcystins and the total amounts of microcystin ranged between 20–1500 μg/g freeze-dried bloom material. In four of the 26 samples, the samples contained anatoxin-a, though the amounts varied. The total microcystin concentration in 30 samples from the lakes was equal to the cellular microcystin in these lakes because no extracellular microcystin was detected. All the lakes except for Lakes Younglang and Mijae are a source of drinking water, so the presence of cyanotoxin can be a potential threat and requires more attention to water treatment. © 1998 John Wiley & Sons, Inc. Environ Toxicol Water Qual 13: 225–234, 1998

Determination of cadmium and lead in urine by electrothermal vaporization isotope dilution inductively coupled plasma mass spectrometry.

Electrothermal vaporization isotope dilution inductively coupled plasma mass spectrometry (ETV-ID-ICP-MS) was applied to the determination of Cd and Pb in urine samples. The isotope ratios for each element in each analytical run were calculated from the peak areas of each isotope. A relatively low vaporization temperature was used, which separated the analyte from the major matrix components and improved the ion signals of Cd and Pb significantly. Various chemical modifiers were tested to obtain the best signal of Cd and Pb. After preliminary studies, 1% HNO3 was added to the samples as the chemical modifier. The ETV-ID-ICP-MS method was applied to the determination of Cd and Pb in freeze-dried urine reference material NIST SRM 2670 and several fresh urine samples. The results for NIST SRM 2670 agreed satisfactorily with the certified values. The results for other samples obtained by isotope dilution and the method of standard additions agreed satisfactorily. The detection limits were 0.02 and 0.005 ng ml-1 for Cd and Pb, respectively. The precision between sample replicates was better than 11% for all determinations.

Hepatotoxic microcystins and neurotoxic anatoxin‐a in cyanobacterial blooms from Korean lakes

Cyanobacterial bloom samples were collected in the warm season during 1992–1995 from the 12 lakes in Korea. Six species each of Microcystis and Anabaena, and two of Oscillatoria were identified in these lakes. The cyanotoxins of 47 samples collected from the lakes were identified as microcystins-RR, -YR, -LR; desmethyl-7-microcystin-LR (7-DMLR), plus anatoxin-a. Microcystins were the main components of these cyanotoxins, while anatoxin-a was detected in samples from a few lakes. Thirty-four of the 47 samples, included microcystins and the total amounts of microcystin ranged between 20–1500 μg/g freeze-dried bloom material. In four of the 26 samples, the samples contained anatoxin-a, though the amounts varied. The total microcystin concentration in 30 samples from the lakes was equal to the cellular microcystin in these lakes because no extracellular microcystin was detected. All the lakes except for Lakes Younglang and Mijae are a source of drinking water, so the presence of cyanotoxin can be a potential threat and requires more attention to water treatment. © 1998 John Wiley & Sons, Inc. Environ Toxicol Water Qual 13: 225–234, 1998