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Abstract Gels prepared from the polysaccharide gellan are used for aqueous poulticing treatments in paper conservation when the application of water must be restricted. Optimal use of the rigid, yet shapeable gel requires direct contact with the paper surface, which carries the risk of gel residues on the treated surface. We used acid methanolysis as a destructive analytical method to detect rhamnose as a component of gellan, which was undetectable with ATR-FTIR spectroscopy. We show that there is a significant probability of leaving gellan residues on the paper. Conservators should be aware of this potential side effect when considering the use of gellan poultices in direct contact with paper objects.

Disposable non-invasive and compatible real time monitoring tool was developed in order to follow the cleaning process of paper artwork directly in situ . This tool was based on a biocompatible cleaning hydrogel coupled with flow electrochemical diagnostic tool, suitable to verify in situ and in a simple way the assessment of degradation of artwork and the efficiency of cleaning process. In this paper, the results obtained by applying this tool on a great format artwork with a lining as support, “Le Nozze di Psiche”, engraved by Diana Scultori, printed in 1613, are reported. This opera was affected by a structural and chromatic deterioration due to a strong oxidative degradation. Such deterioration was probably accelerated by the adhesive (a mixture of starch paste and animal glue) used in a previous lining intervention. In this case, the cleaning agents used are rigid hydrogels of Gellan gum, modified with hydrolytic enzymes. By using the flow sampling system, all materials removed by the gel was carried up to a thin layer cell containing a selective electrochemical biosensors, suitable to monitor both treatments, the cleaning process and the removal of lining. These were monitored, allowing understanding when both processes were completed, thus avoiding lengthy and unnecessary cleaning applications. The effectiveness of cleaning with Gellan gel was assessed quantitatively by using non-invasive optical reflectance spectroscopy by a portable instrumentation, elaborating data with an improved version of the Kubelka-Munk theory in order to recover the absorption coefficient of the cellulose fibers of “Le Nozze di Psiche”. The concentration of oxidized groups acting as chromophores was obtained by comparing the experimental optical absorption spectra to those simulated computationally by using TDDFT-based calculations. By following the cleaning with Gellan gel the results indicate a large decrease of the concentration of degradation product of cellulose. Moreover, chromatographic analysis were carried out in order to evaluate the amount of acid compound, produced during the aging and present on the graphic artwork, using the Gellan gel after cleaning step. The results obtained from the restoration of “Le Nozze di Psiche” have allowed the restorers to evaluate innovative methods for cleaning treatment of paper artworks with a highly specialized scientific-diagnostic approach. [ABSTRACT FROM AUTHOR]

Wet cleaning of ancient papers is one of the most delicate and important steps in a restoration process. It allows to improve the optical quality of a graphic work as the removal of pollution and of organic substances resulting from cellulose degradation. Nevertheless, washing by immersion – the traditional process – usually involves a substantial impact on the original morphological structure of paper and could be dangerous for water sensitive inks and pigments. Furthermore it is very important that the time of the cleaning process is optimized in order to remove all contaminants, thus minimizing invasive treatments and time costs. In this contest, we have developed an innovative and non-invasive cleaning and diagnostic tools, based on a hydrogels combined with electrochemical sensor, suitable to verify in situ and in a simple way the paper degradation progress, and the efficiency of cleaning treatment. More in detail, the wet cleaning technique is based on the use of a rigid hydrogel of Gellan gum. This gel is able to gradually release the water and also to absorb the water-soluble degradation products present on the paper. Moreover, it is rigid and therefore its application and removal are fairly simple, not leaving residues on the paper surface after treatment. It could be easily combined with selective electrochemical biosensors, suitable to monitor the cleaning process. Using this new tool (a biocompatible hydrogel and an electrochemical sensor) it is possible to know when the cleanup process is completed, avoiding lengthy and sometimes unnecessary cleaning material applications. Here we report the results obtained by applying the proposed system to the “ Breviarium Romanum ad usum Fratrum Minorum ”, a breviary of the 18th century, highlighting the advantage and the potentiality of this new tool with respect to the traditional old paper cleaning methodology. To perform a complete characterization of the proposed system, several invasive and non-invasive techniques, such as spectroscopy, scanning electron microscopy, high-performance liquid chromatography analysis and pH measurements have been used. [ABSTRACT FROM AUTHOR]

Abstract: Gellan gum is an increasingly popular and a naturally occurring hydrocolloid. It is widely used in the food, chemical, and pharmaceutical industries as a stabilizer, emulsifier, thickener, and gelling agent. The gel is also used as a model material to study microwave heating dynamics of biological materials in the food processing industry. In this study, baseline data on dielectric properties of 1% gellan gel containing 0.17% and 0.3% CaCl2 were collected at frequencies between 0.2 and 20GHz and temperatures between 10 and 100°C. These data are compared with those of distilled water containing similar ionic concentrations. Models describing the behavior of the dielectric constant, loss factor, loss tangent and the penetration depth for 0.2–3.2GHz were developed. These models can be effectively used in microwave food processing applications of gellan gel, which will save considerable time and effort often used in empirically determining the dielectric spectra. [Copyright &y& Elsevier]

Abstract: The effect of inulin on the gelation of 0.5wt% low acyl gellan in the presence of increasing concentrations of potassium chloride was investigated by large deformation compression experiments and visible light absorbance. The sugar and salt concentrations varied from 0 to 15wt% and 40–100mM, respectively. Stress and strain at failure along with Young’s modulus were calculated from each compression curve. Samples prior to compression were refrigerated at 5°C for 24h. Reduced gel strength and firmness were observed for all inulin and salt concentrations. Increasing amounts of inulin resulted in an increase in gel strength which was greater for higher potassium concentrations. Elasticity values did not exhibit great diversion. Inulin at concentrations of 5 and 10wt% led to less turbid gels than those with only gellan. Samples containing 15wt% inulin gave absorbance readings greater than 1. [Copyright &y& Elsevier]

The present study prepared an innovative structured fruit (SF) product based on king oyster mushroom (Pleurotus eryngii), litchi juice and gellan gel, and evaluated its textural, nutritional and sensorial properties. The lyophilized mushroom semi-ball sample was immersed in litchi juice containing different concentrations of gellan gel (0.25% and 0.5%), the SF products were obtained after the gelation of gellan gel. The nutritional analysis showed that the SF product possessed higher fiber and protein content, while lower sugar content than fresh litchi fruit. It retained about 30%–50% ascorbic acid, total phenols and total antioxidant capacity of fresh litchi due to the heating process during gel formation. Texture profile analysis revealed that gellan gum improved the texture properties of the structured fruit on hardness, cohesiveness, gumminess, chewiness, and resilience. Sensory descriptive analysis found that most sensorial attributes were highly remained in the final product, but the juiciness was significantly decreased by the addition of gellan gum. Scanning electron microscopy (SEM) observation revealed the synergistic effects between the mushroom and gellan gel resulted in the improved structure properties. In conclusion, the SF product could be a good solution for improving nutritional intake and reducing fruit wastage. • Innovative structured fruit from litchi juice, king oyster mushroom and gellan gum. • Texture was much improved by the combination of king oyster mushroom and gellan gel. • Synergistic effects improved structure properties rather than simple combination. • The structured fruit has higher protein and fiber content while lower sugar content. • Considerable ascorbic acid and phenols content, and antioxidant capacity remained. [ABSTRACT FROM AUTHOR]