Imma Perfetto
Cosmos science journalist
Scientists study how to make the best kimchi
Fermented foods like kimchi have been an integral part of Korean cuisine for thousands of years. Today, most kimchi is made through mass fermentation in glass, steel, or plastic containers, but it’s long been claimed that the highest quality kimchi is fermented in traditional handmade clay jars called onggi.
“We wanted to find the ‘secret sauce’ for how onggi make kimchi taste so good. So, we measured how the gases evolved while kimchi fermented inside the onggi — something no one had done before,” says says Professor David Hu, from the school of Mechanical Engineering at the Georgia Institute of Technology, US, and senior author of a new study in the Journal of the Royal Society Interface.
Hu and Soohwan Kim, a PhD student in Hu’s lab, measured carbon dioxide levels in onggi during kimchi fermentation and developed a mathematical model to show how the gas was generated and moved through the onggi’s porous walls.
Their findings explain why previous studies have shown that kimchi fermented in onggi has more lactic acid bacteria; the porous structure of these earthenware vessels mimics the loose soil where lactic acid bacteria are found, allowing CO2 to escape the container and preventing the bacteria from being suffocated.
“Onggi were designed without modern knowledge of chemistry, microbiology, or fluid mechanics, but they work remarkably well,” says Kim. “It’s very interesting to get these new insights into ancient technology through the lens of fluid dynamics.”
An alternative to single-use hard plastics made from sugar and wood powders
Researchers have created sturdy, lightweight materials made from a sugar-like substance and wood-derived powders which disintegrate on demand. They could be used to make alternatives to single-use hard plastics, according to a new study in the journal ACS Sustainable Chemistry & Engineering.
The team heated isomalt – a sugar alcohol – to a liquid-like stage, and mixed in either cellulose, cellulose and sawdust, or wood flour to produce three potential materials. Then, using commercial plastics manufacturing equipment, the materials were extruded into small pellets and moulded into various objects.
The resulting materials were harder than plastics, lightweight, and dissolved in water within minutes. When coated with a food grade shellac and cellulose acetate, they withstood being immersed in water for up to seven days.
They also repeatedly crushed, dissolved and recycled both coated and uncoated objects into new products which were still as strong as the original items.
“Applications of these materials may include single-use food service items or seasonal and event décor, where products in these categories need only to withstand storage, transportation, and short-term use,” they conclude.
The stripes of these octopuses are as unique as our fingerprints
Biologists studying Lesser Pacific Striped Octopuses (Octopus chierchiae) have discovered their gorgeous stripes are unique to individuals, and remain so over their lifetimes, which may have implications for studying the species in the wild.
According to a new study in PLOS ONE, the researchers photographed the physical development of 25 octopuses over the course of several months after hatching. They found that each had individually unique stripe configurations and even untrained volunteers could accurately identify whether a pair of images depicted the same individual octopus.
“These results demonstrate that laboratory-reared individuals could be identified via photographs taken at different points in their lifetimes, which suggests wild individuals can also be recognised and observed for longitudinal field studies,” the authors write.
They say these results suggest that photo-identification and citizen science could be used as a non-extractive and non-intrusive sampling method for future studies of O. chierchiae in the wild.
A multifunctional patch that detects changes in plant health before growers
Researchers have developed an electronic patch that can be applied to the leaves of plants to monitor crops for infections and stresses such as drought or salinity. The patch has been shown to detect a viral infection in tomato plants (tomato spotted wilt) more than a week before visible symptoms of the disease could become apparent, according to a paper in Science Advances.
The patches are only three centimetres long and consist of a flexible material containing sensors and silver nanowire-based electrodes that monitor volatile organic compounds emitted by plants, temperature, environmental humidity, and the amount of moisture being ‘exhaled’ by the plants via their leaves.
“This is important because the earlier growers can identify plant diseases or fungal infections, the better able they will be to limit the spread of the disease and preserve their crop,” says corresponding author Qingshan Wei, Assistant Professor of Chemical and Biomolecular Engineering at North Carolina State University in the US.
“In addition, the more quickly growers can identify abiotic stresses, such as irrigation water contaminated by saltwater intrusion, the better able they will be to address relevant challenges and improve crop yield.”