Shelf Life

Related Content
Changed on: 08.08.2017

The fact that a food product may have passed its best-before, freshness or shelf-life date does not mean that the product cannot be eaten anymore.

Manufacturers guarantee that a product keeps its full edibility up this point of time when stored correctly; this is only possible if the product maintains its actual edibility for a longer period.
In other words, food products usually last longer than the best-before or freshness date provided. However, it is often difficult to tell how much longer, as it depends on the product in question and also its storage up to this point in time.

If a rough examination using our senses (colour, visual appearance and odour) does not find anything unusual or suspicious and the timeframe between the period the product has exceeded the best-before or freshness date and the actual shelf life is short, then there is no reason not to eat the product.

This is a significant difference to products featuring a so-called expiry dates ("zu verbrauchen bis"). An expiry date is carried by easily perishable goods that contain microorganisms.

A product that has exceeded its expiry date is not considered to be safe anymore. Such a product should not be eaten and be immediately disposed of.

The fact that a food product may have passed its best-before, freshness or shelf-life date does not mean that the product cannot be eaten anymore.

Manufacturers guarantee that a product keeps its full edibility up this point of time when stored correctly; this is only possible if the product maintains its actual edibility for a longer period.
In other words, food products usually last longer than the best-before or freshness date provided. However, it is often difficult to tell how much longer, as it depends on the product in question and also its storage up to this point in time.

If a rough examination using our senses (colour, visual appearance and odour) does not find anything unusual or suspicious and the timeframe between the period the product has exceeded the best-before or freshness date and the actual shelf life is short, then there is no reason not to eat the product.

This is a significant difference to products featuring a so-called expiry dates ("zu verbrauchen bis"). An expiry date is carried by easily perishable goods that contain microorganisms.

A product that has exceeded its expiry date is not considered to be safe anymore. Such a product should not be eaten and be immediately disposed of.

freezing food

Informations on freezing Food

Preparation

Proper preparation is important: cleaning, cutting, etc. is easier to do before freezing a product than after defrosting it -- e.g. as is also coating mushrooms with breadcrumbs. Take a look at your freezer manual, which often contains valuable information from the manufacturer. Additionally, there are numerous websites on the internet providing detailed advice.
Should I first blanche the vegetables or not? A truly difficult question to answer. A certain amount of nutrients will get lost during the blanching process. On the other hand, the remaining nutrients (because the enzymes have been deactivated), colour and flavour will remain longer.

Shock Freezing Process

Make sure the product is frozen as quickly as possible, as this is where most of the quality is lost (slow growing ice crystals will destroy the cell walls, thus, damaging the texture: fruit will become "mushy"). Turn the machine on to full freezing power a few hours before (do it the day before if the freezer is very full). Do not freeze large packages and fill bags as flat as possible. Do not put them on top of each other for freezing. You can always rearrange them later. Do not freeze too many things at once. Note: you can buy frozen products at the supermarket.

Regulating Storage Temperature

Set the storage temperature at a minimum of at least -18 °C, maybe even lower. This way, almost all food should keep for about 10 months when packed appropriately. A longer storage period would not really make sense, as freezers are not intended for keeping foods for times of need or emergencies.

Defrosted Food

Refreezing defrosted food? Basically not a problem from a microbiological perspective, if the item in question is only slightly thawed or the defrosting period was short. Bacteria do not generally reproduce at freezing temperatures, so you do not have to fear that refreezing could damage your health. However, the quality loss could be considerable.

Packaging

Do not underestimate the influence of packaging: unsuitable or very thin materials could let oxygen or odours through. Make sure the package is sealed as tightly as possible after removing most of the air (lack of air-tightness or too much air will lead to freezer burns and dry out the surface. While this is not dangerous, the quality will deteriorate.) Vacuum-packing and sealing is ideal, but a knot in the tightly twisted end of the bag should also do. A wire paperclip should not be used. Only use tins if they stay sealed when frozen and can be filled almost to the top. Do not freeze goods with strong odours such as onions or garlic. This could have a very negative effect on the cake you have frozen before.

Last but not least, label and organise the contents of your freezer to keep track of everything.

Aufgetaute Lebensmittel nicht wieder einfrieren!

Kühlschrank

Aufgetaute Lebensmittel sollen nicht wieder eingefroren werden: Krankheitserreger können sich beim Auftauen vermehrt haben; Gefrierbrand ist schlecht für die Qualität.

Krankheitserreger: Viele Erreger sterben bei Minusgraden nicht ab und können sich nach dem Auftauen wieder vermehren. Besonders heikel sind in dieser Hinsicht leicht verderbliche Lebensmittel wie rohes Fleisch und Fisch oder Rohmilchprodukte. Wurde zu viel rohes Fleisch/Fisch aufgetaut sollte man vor dem nochmaligen Einfrieren die Lebensmittel auf jeden Fall völlig durchgaren (mind. 70 °C für 2 Minuten im Kern des Lebensmittels).

Gefrierbrand: Beim Einfrieren von Lebensmitteln gefriert das Wasser, das in den Zellen enthalten ist, zu Eiskristallen und zerstört die Zellwände. Beim Auftauen tauen dieses Eiskristalle ebenfalls auf, das Lebensmittel verliert Wasser: Dadurch kommt es zu einem Gewichtsverlust und das zubereitete Lebensmittel ist trockener als frisch Zubereitetes.
Beim Wiedereinfrieren bilden sich aus dem Auftauwasser größere Eiskristalle aus, die noch mehr Zellen zerstören; das Lebensmittel weist in Folge trockene Stellen, den so genannten Gefrierbrand, auf.
Produkte die im Handel gefroren angeboten werden, sind in der Regel schockgefroren. Diese Lebensmittel werden innerhalb sehr kurzer Zeit auf die gewünschte Lagertemperatur – 18 °C oder niedriger abgekühlt. Durch diesen raschen Prozess bleiben die Zellwände intakt (es bilden sich nur sehr kleine Eiskristalle) und Lebensmittel behalten ihre Konsistenz und andere Eigenschaften wie Aromen etc.

Tipps

  • Transport: Gefrorenes in Kühltaschen oder -Behältern transportieren, damit die Kühlkette nicht unterbrochen wird. Hinweise auf der Produktverpackung zu Lagertemperatur und Mindesthaltbarkeitsdauer beachten.
  • Einfrieren: Zubereitete Lebensmittel vor dem Einfrieren abkühlen lassen, damit sich kein Kondenswasser im Gefrierfach bildet. Dieses würde gefrieren und große Eiskristalle auf der Speise bilden.
  • Auftauen: Lebensmittel sollten in luftdichten Behältern im Kühlschrank aufgetaut werden. Auftauwasser sorgfältig entfernen und benutztes Küchengeschirr - Messer, Schneidbretter und auch die Hände – gut mit Spülmittel oder Seife und heißem Wasser reinigen.
  • Wiedereinfrieren: Wurde zu viel rohes Fleisch/Fisch aufgetaut, vor dem nochmaligen Einfrieren auf jeden Fall völlig durchgaren (mind. 70 °C für 2 Minuten im Kern des Lebensmittels). Nur so ist sichergestellt, dass alle Keime abgetötet werden.
  • Gefrierbehälter: Zum Einfrieren im Haushalt ausschließlich gefriergeeignete Materialien verwenden. Das sind Gefrierbeutel, Kunststofffolien oder stapelbare Plastikboxen mit einem dicht schließenden Deckel. Ungeeignet sind Pack- und Pergamentpapier, Plastiktragetaschen oder Müllsäcke sowie Joghurt- oder Margarinebecher und Gläser, die brechen oder splittern können.

Food Irradiation

Method

Food irradiation is a physical preservation method using ionising radiation. Electrons or gamma radiation from the radioactive decay of Cobalt-60 are typically used as ionising radiation. However, the food will not become radioactive when subjected to this kind of radiation.

Treatment with ionising radiation kills microorganisms and delays ripening und germination processes, thus, prolonging shelf life.

Method

Food irradiation is a physical preservation method using ionising radiation. Electrons or gamma radiation from the radioactive decay of Cobalt-60 are typically used as ionising radiation. However, the food will not become radioactive when subjected to this kind of radiation.

Treatment with ionising radiation kills microorganisms and delays ripening und germination processes, thus, prolonging shelf life.

Legal Regulations

Legal Regulations

The legal basis for food irradiation is regulated in §9 of the Austrian Food Safety and Consumer Protection Act. It states that it is prohibited to treat food with ionising irradiation or place it on the market without official permission.

Food irradiation is regulated at EU levels in the Framework Directive 1999/2/EC (defines labelling, among other subjects) and Community Directive 1999/3/EC (contains the list of products permitted to be treated with irradiation in the EU). Only dried aromatic herbs and spices may be treated using irradiation in Austria, in accordance with EU Directive 1999/3/EC. There are national permits for any other food products in Austria, while various foods may be treated using irradiation in other countries. Food treated with irradiation must be labelled as "bestrahlt" (irradiated) or "mit ionisierenden Strahlen behandelt" (treated with ionising irradiation).

Detection Methods

Detection Methods

Checking for evidence of food irradiation is done either on frozen excited charge-transfer states or on radical species, formed during irradiation and by decay products. The various analysis methods are described in the following paragraphs.

Luminescence Measurements

These methods are based on charge carriers of mineral impurities -- e.g. traces of soil excited by the irradiation. The charge carriers will go back to their original state by adding energy (heat or light). This causes luminescence which is measured. This includes photostimulated luminescence (PSL), a rapid screening method, and the more elaborate thermoluminescence (TL) method, used for test assurance. Fields of application include spices and tea.

Electron Spin Resonance (ESR)

When treated with irradiation, crystalline structures (bone, shells, etc. in animal products or crystalline cellulose and sugar in plant products) form stable radicals. These radicals absorb microwave radiation in a magnetic field. This method is used to examine poultry, lamb, fish and shellfish, nuts, berries, etc.

Gas Chromatography Mass Spectrometry (GC-MS) of Fat Radiolysis Products

During the irradiation of foods containing fat, the radicals formed lead to the creation of 2-alkylcyclobutanons, which are radiation-specific marker substances and can be detected using GC-MS analysis in the headspace sample. This method is used for meat and fish samples, for instance.

Examinations

Examinations

The Group "Contamination and Special Analytics" is Austria’s sole institute conducting routine examinations on food irradiation. It uses a variety of special equipment enabling it to apply all the methods mentioned above.

Official food inspections test a variety of foods, such as spices, herbal tea, instant soup, poultry, fish, shellfish and crustaceans, etc. to determine whether irradiated herbs or spices have been labelled properly or whether other foods have been illegally treated using irradiation.
We also offer services in the field of special analytics to private clients from production and retail, as well as to other laboratories.

Analysis Results 2013

More than 100 samples of mainly spices, instant soup and shellfish were examined in 2013. The following chart shows which and how many samples were analysed using what methods in detail.

The use of irradiation could be confirmed in eight samples (7.5 %) of a total of 106 samples, the majority of which were instant soup (see chart on the left).


Contact

Dr. Christoph Czerwenka
Phone: +43 50 555-32531
Spargelfeldstraße 191
1220 Wien



Dr. Christoph Czerwenka
Phone: +43 50 555-32531
Spargelfeldstraße 191
1220 Wien



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