How to preserve rice cakes

Conservation

Max Liebermann: female canners (1879)

Conservation (Latinconservare, "Preserve, preserve") describes the extension of the shelf life of objects by reducing chemical aging.

Typically, foods such as food and luxury goods are preserved for a longer or shorter period of time with the help of preservatives and processes. In the case of everyday objects, preservation also includes a reduction in wear and tear and corrosion.

The preservation prevents or delays physical decomposition processes, which z. B. caused by drying out or swelling, as well as chemical decomposition processes such as oxidation and hydrolysis. In the case of biodegradable substances, autolysis and degradation by microorganisms such as putrefactive bacteria, mold and yeasts also take place.

Food and feed

The preservation of food and feed has always been of particular importance. In order to make them durable over the long term, there has been the possibility of preserving for centuries. Physical preservation processes change structure and taste, and a loss of vitamins and aromas is often unavoidable. Chemical preservation processes carry the risk of allergic reactions or hypersensitivity reactions to the preservative. Shelf life, economic efficiency of the process, tolerance, harmlessness and nutrient retention have to be weighed against each other.[1]

Depending on the food or feed to be preserved, the culture area and the technical and economic possibilities, different processes are used or combined.

Increase in osmolarity

The addition of water-soluble substances or the withdrawal of water increase the osmolarity to the point of hypertonicity, whereby water is withdrawn from the contaminating microbes.

Biocides

The addition of biocides either kills the microbe (biocide) or prevents microbial growth (biostatic).

Oxygen deprivation

Withdrawal of oxygen prevents the growth of all oxygen-dependent microbes (Obligatory aerobic), while the growth of microorganisms that do not depend on oxygen, but grow faster with it (optional aerobic) is slowed down.

  • Soaking in airtight liquids, e.g. B. the antipasti in oil
  • Protective gas atmosphere
  • Antioxidants such as ascorbic acid

Temperature deprivation

Since microbes have an optimal growth temperature, their growth can be slowed down by cooling.

  • Cooling at around 4 ° C slows down microbial growth, e.g. B. when storing beer, only psychrophilic microbes can still grow
  • Freezing below the freezing point of water slows down microbial growth, only cryophilic microbes can still grow

disinfection

Disinfection describes the inactivation of microorganisms and inanimate pathogens.

Coating

A coating makes it difficult for microorganisms to enter.

  • Ingrowth of fruits e.g. B. for fruit storage of apples and citrus fruits

drug

In pharmacy, the preservation of medicinal products means protection against microbial spoilage. Such protection is particularly important for the shelf life after opening, since germs can easily be introduced into the medication by opening the medication packaging and removing the medication. Some drugs, especially those that contain water, already require a preservation in order to maintain the perfect microbiological quality over their entire shelf life up to the expiry date.

Medicines for use on the eye and for parenteral administration are made durable through sterilization processes or aseptic production and subsequent sterile sealing; chemical preservation of the drugs is usually not necessary, provided that they are used up during use. However, when packing in containers for multiple withdrawals, preservation is mandatory.

Cosmetics and household chemicals

Cosmetics and cleaning agents are mixed with biocides, such as B. Isothiazolinone, phenoxyethanol or benzoates such as paraben. This is especially necessary if they have a high water content and biologically usable substances.

Building materials

In the case of building materials, other processes are also used, such as B. the impregnation of porous materials with plastics (impregnation) in wood, concrete or sandstone and the painting of surfaces with varnish or a linseed oil varnish.

Art and cultural assets

In the field of fine arts and cultural assets in general, conservation or conservation is an umbrella term for all measures that serve to examine, document, maintain and make legible the authenticity of artistic or culturally-historically relevant works, taking into account their age and history, without changing it irreversibly. The guarantee of object security, disaster prevention and defined and constant ambient climates with regard to room temperature, relative humidity, light and pollutant emissions as well as room hygiene conditions already represent a fundamentally important form of preventive conservation for works of art, their transport and storage. The aim of preventive conservation is to To minimize restorations or to make them unnecessary. Preventive or preventive conservation consists in protecting works of art from damage and preventing them from deteriorating.[2] The control of the room climate (temperature, humidity) and the light irradiation should be emphasized. In order to preserve works of art, it is essential to adhere to these conditions, also during their transport, as well as during and after conservation or restoration.[3] In the document from Vantaa (Finland) the guidelines for preventive conservation were laid down in 2000.[4] Conversely, professional restorations always include conservational elements. Cultural monuments are preserved and cared for in the public interest, see Monument Preservation. Vehicles, especially classic cars, are often preserved with wax to maintain their value.

Corpses and tissue preservation

The preservation of human corpses is known as embalming, now also known as plastination using plastics. Animal bodies can be permanently prepared by drying, tanning the skin parts and stuffing them after removing the (inner) water-rich parts of the organs and replacing the eyeballs. During fixation, glucose, glycerine, thymol, phenol, formalin (carcinogenic and largely forbidden), paraformaldehyde and various drying processes are also used in histology and preparation technology to preserve biological tissue.

evolution

In genetics and biochemistry, conservation is understood to mean the degree of preservation of a gene or protein in the course of evolution, i.e. the similarity and relationship between genes and proteins. If this information is available almost unchanged between different species, one speaks of a "high conservation". From this it can be concluded that the function of the gene or protein is important for the survival of the respective species and that there is a high selection pressure on its function, since naturally occurring mutations in these areas can be associated with negative functional changes. These are possibly lethal and therefore do not have the possibility of being passed on further.

literature

  • Ursula Schädler-Saub and Angela Weyer (eds.): Theory and Practice in the Conservation of Modern and Contemporary Art (Conference files of the International Symposium, January 13-14, 2009 in Hildesheim), (Writings of the Hornemann Institute Volume 12), London 2010, ISBN 978-1-904982-54-8.

Magazines

  • Paper restoration or since 2009 Journal of Paper Conservation, ed. by the International Association of Archive, Library and Graphic Restorers (IADA) - appears four times a year, http://palimpsest.stanford.edu/iada/
  • VDR contributions to the preservation of art and cultural assets: The VDR's specialist journal, ed. from the Association of Restorers (VDR) - appears twice a year, as well as other monographs on special topics, http://www.restauratoren.de.
  • Restauro - Specialist publication for restorers, conservators and preservationists, Callwey Verlag Munich, ISSN 0933 - 4017, http://restauro.de
  • ZKK - magazine for art technology and conservation published since 1987, 2 issues per year, Wernersche Verlagsgesellschaft, ISSN 0931-7198, [1]
  • Restoration and archeology. Conservation, restoration, technology, archaeometry (multilingual), appears annually, Volume 1 was published in 2008, Verlag des Römisch-Germanisches Zentralmuseums - Research Institute for Prehistory and Protohistory Mainz.

Web links

Individual evidence

  1. ↑ http: //www.besserhaushalten.de/bevorratung/vorratshaltung/konservierungslösungen.html
  2. ↑ http: //www.ig-restauratorinnen.at/ecco_beruf_restaurator.htm
  3. ↑ http: //www.doernerinstitut.de/downloads/burmester_Was_ist_PK.pdf
  4. ↑ http: //restauratoren.de/fileadmin/red/pdf/Dokument_Vantaa_web.pdf