Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Light shortens the life of supermarket vegetables

27.10.2008
According to various studies undertaken by researchers from the University of La Rioja, exposure to light reduces the quality of cauliflower, broccoli, chard, leeks and asparagus, which have been processed for sale.

Their latest work has been published in the Journal of the Science of Food and Agriculture, and shows that the useful life of chard is reduced by 11 days if it is exposed to light instead of keeping it in the dark, even though it has been covered in the best protective wrap.

“We have established that there is a negative effect on the sensory quality of minimally processed vegetables (MPV) if they are exposed to light. These are foods that are ready for immediate consumption after being washed, peeled, cut and wrapped in protective polymeric wraps ”, Susan Sanz explains to SINC and who is from the Department of Food Technology at the University of La Rioja. Her team has shown that the useful life of leeks is reduced from approximately 26 to 18 days if they are exposed to light, broccoli from 14 to 11 days, and cauliflower from 11 to 3 days.

According to Sanz, “the colour is affected in particular in non-pigmented green vegetables (cauliflower, asparagus, leeks and the white part of the chard), whereas in green vegetables (broccoli, leeks and the green part of the chard) the sensory attribute which suffers the most deterioration is texture”.

Light activates the opening of the stomata (pores in which gas exchange occurs in plants), causing an increase in respiratory and photosynthetic levels. In the case of chard, for example, the green parts have a high stomatal density, for which reason a greater interchange of oxygen and carbon dioxide occurs, in addition to a loss of water which, similarly, promotes dehydration. The white parts, on the other hand, “respire much less”, but the light affects their coloration more.

The scientists have illuminated various containers storing non pigmented vegetables and have shown that they have atmospheres with higher CO2 levels and less O2 content than those kept in the dark, using the same type of wrap. As regards green vegetables stored in illuminated conditions, they have an increased respiratory rate, although this is compensated for by the photosynthetic activity of the plant itself. In this case, the composition of the atmosphere on the inside of the container and the lifetime of the product depend on the permeability of the wrap used.

Scientists have shown that fresh or near fresh vegetables ”do not usually exceed the two weeks’ useful shelf life”, and that light promotes their deterioration since this accelerates the transpiration and respiration of these plants, and changes the way they behave. Sanz does point out that not only is it important not to break the cold chain, but it is also important to control the atmosphere inside the container so that it suits the type of vegetable”.

The response to light exposure is different depending on whether a leaf, an inflorescence (such as the cauliflower or broccoli), a root or a stem is involved. “These factors should be taken into account when establishing the optimum conditions of process, storage and commercialisation”, Sanz states.

The researcher recognises that the ideal situation would be to keep the vegetables both in the cold and in the dark, which is what actually happens in distributors’ coolers and sales points, but at the end of the day they must be on view to the consumer. Her team is already carrying out tests to see which is the ideal colour for lights at the point of sale so that the vegetables are not affected so much. In any case, they recommend the shelves are refilled frequently so that the products are exposed to light for the least time possible, as well as using “attractive containers, but adapted to each type of vegetable”.

“We are used to seeing clear wraps and it is nice to be able to see the product, but we need to progress towards dyed wraps, which could have a small window in them in order to see inside the product”, Sanz emphasises. She quotes the consumers’ willingness to accept crisp bags as an example. As light affects the oxidation of fatty products, previously clear plastic bags for this product are currently protected by brown paper, or have been replaced directly with bags made from aluminium with a photo of the crisps on the outside.

SINC Team | alfa
Further information:
http://www.plataformasinc.es

More articles from Health and Medicine:

nachricht Correct connections are crucial
26.06.2017 | Charité - Universitätsmedizin Berlin

nachricht One gene closer to regenerative therapy for muscular disorders
01.06.2017 | Cincinnati Children's Hospital Medical Center

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Touch Displays WAY-AX and WAY-DX by WayCon

27.06.2017 | Power and Electrical Engineering

Drones that drive

27.06.2017 | Information Technology

Ultra-compact phase modulators based on graphene plasmons

27.06.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>