The Science of Taste

By David Morris

Structure of a taste bud

In 350 BC, the Greek philosopher Aristotle postulated that varying blends of two tastes, sweetness and bitterness, comprised all flavours. As the understanding of taste developed, it was shown that sourness and saltiness were also distinct tastes. In 1908 the Japanese chemist, Kikunae Ikeda, discovered a fifth subtle and now well established taste known as umami. Until recently, these tastes were universally accepted as the five fundamental detectable tastes that made up all flavours that can be experienced by humans.

The role of smell (olfaction) in flavour wasn’t fully appreciated until as late as 2004, when biologists Richard Axel and Linda Buck discovered the role of the nose in detecting and characterising odours. When you breathe in through your nose, millions of odorous molecules activate and inhibit olfactory receptors at the roof of the nasal cavity. Electrical impulses travel from these receptors to the brain, informing you of what you’re eating. This action is supported by taste buds in the mouth.

Molecules within certain foods can chemically activate senses that are responsible for the sensation of heat, pain or touch. This is known as chemesthesis. Despite being different from taste, chemesthesis can contribute to the flavour of a substance. Examples include the ‘tingle’ on the tongue from ingestion of carbonated drinks, the feeling of heat upon eating a chili pepper, and the cooling feeling from eating gum.

 Taste receptors are mounted on papillae, which are structures found on the front and back of the tongue, the roof and sides of the mouth, and even at the back of the mouth and throat. The idea of a ‘tongue map’ whereby certain areas of the tongue detect certain tastes is a myth, although the concentration of certain receptors may vary in different areas of the tongue.

           Saltiness and sourness are the simplest of the tastes. Sourness arises from the donation of hydrogen ions, which is a characteristic feature of acids. It has been postulated that detection of sour foods defends the body from ailments like indigestion. Similarly, saltiness arises from the dissociation of salt on the tongue, forming sodium and potassium ions. The taste response acts as a warning for your body to replenish electrolytes, but not too much, hence why we find salty foods appealing, but also repulsive in large amounts.

                  

           Bitterness, umami and sweetness are more complicated tastes. They all come from the binding of larger, more complex molecules to large proteins in the taste buds that are typically responsible for signal transduction throughout the body. Bitterness receptors can bind with molecules that are usually toxins or poisons. In this way, the bitter taste warns your body against ingesting molecules that can harm your body.

           Similarly, umami receptors detect glutamate (a component of monosodium glutamate, or MSG, a popular salt substitute), giving off a subtle savoury taste. The subtlety arises because the glutamate is usually bound to sodium, giving off a more powerful salty taste. Glutamate is useful to your body as a neurotransmitter and a catalyst to metabolism, so like salt, the taste warns your body to replenish glutamate, but not excessively.

Tomatoes are rich in umami

           In July of this year, academics at the University of Purdue published a paper in Chemical Senses describing the existence of a sixth taste called oleogustus. Usually, when the body ingests oil or fat, it is in the form of triglyceride, a molecule comprised of three fatty acids chemically bound through a glycerol molecule. This triglyceride is too large to fit into oleogustus receptors and thus can’t be tasted. However, when the fat spoils, the triglyceride is broken down into glycerol and the fatty acids. The fatty acid then binds to the oleogustus receptors and acts as a warning that the food is no longer suitable for ingestion, hence it smells and tastes rancid.

                  

           Each of the aforementioned tastes, as well as the olfactory and chemesthetic systems, have proven essential for the body to be able to consume the correct amount of different types of food, and to protect from ingesting harmful toxins and poisons.

Transition in Pharma

What needs to be prescribed to an industry in distress?

by Toby Benham

Recent large scale closures of R&D sites in the UK from pharma giants Pfizer, Merck, GSK and now Novartis has led to the nationwide desolation of the pharmaceutical industry. With cuts extending around the world, and several big challenges ahead, it appears the industry is heading into a time of transition. To emerge through this transition stronger it is important for pharmaceutical companies to collaborate, working together for the collective good of the field.

Difficult times

The dominant business model adopted in recent times by pharmaceutical companies involved investing heavily into promising drug candidates, attempting to create the next big blockbuster. For associated with these iconic blockbusters are fame and fortune. Drugs such as Lipitor and Plavix have allowed their respective companies to thrive previously. However, the industry has been looming over the edge of the “patent cliff” (when many current blockbuster patents expire) for several years and now companies are lining up for the plunge. It means that these drugs can be manufactured and sold by any generics company at the detriment of the inventor company’s profits. This strategy relies on new blockbusters to come through the system but current pipelines appear relatively fruitless. 

Developing new drugs is an expensive business. Forbes estimates that it now costs approximately $5 billion per new drug created; this is not a sustainable figure. Costs spiral during the 15 years that contribute to getting a drug to market. The drug discovery, optimisation, clinical trials, patent protection and marketing involved are all long expensive processes. However, the main reason that the figure is so high is due to the unseen added cost of research into unsuccessful drug projects. Thus, there could not be a worse time for worldwide scandals to be breaking out in the news, smearing the image of pharma. Just last year, both GSK and Novartis were alleged to have bribed doctors and healthcare officials in China. There are also questions over the safety of some drugs already on the market.  GSK’s “Avandia” for diabetes treatment has been under intense scrutiny for several years now with restrictions in the US only lifted recently. With so many hurdles in the development process - ranging from toxicity to manufacturing - high risk, high reward projects may now be considered just that bit too risky. 

The future

Most importantly, big pharma need to ditch their profit alone method and support one another for their collective benefit. In 2013, data analytics company SAS announced the creation of a globally accessible but private bank of data for pharmaceutical companies to pool clinical trial data. GSK have been the first to share. Perry Nisen, the GSK senior vice president for science and innovation, announced that, “in sharing our data with researchers across the world, we hope to further scientific research and increase understanding about our medicines.”  This exemplary collaborative model will allow companies to improve efficiency and enhance the decision making progress which is so crucial in pushing forward drug candidates. Working on projects across companies should also be encouraged with the chance to explore new opportunities, widen portfolios and spread risk. GSK and Novartis recently announced an asset swapping deal, but this could go even further.

In addition, the big pharmaceutical companies can collaborate with the smaller businesses to flourish from symbiotic relationships. Companies such as Aurigene offer cost effective outsourcing of R&D in their respective areas of expertise, creating what Aurigene describe as a “win-win partnership” that accelerates discovery. The opportunities are not limited to industry with many experts in academia to link up with. Sanofi-Aventis and Pfizer have already created strong partnerships for drug development with Harvard University and UCFS respectively. Back in the UK, Astra Zeneca is building a new headquarters located in Cambridge with the intent to partner with Cambridge University and local hospitals.  By sharing scientific talent and resources, the drug development process gains extra quality and creativity from fresh perspectives. Diversity and partnerships lead to innovation which is essential to feeding hungry company pipelines. A wider communication with regulators would also be invaluable. Hopefully this could put an end to public scandals and improve the clinical trial process. 

Change is required to replace the current unsustainable business model in the pharmaceutical industry. With the right partnerships, a new streamlined, cost effective and innovative R&D system is possible. This will reduce the price of creating a drug by increasing productivity whilst simultaneously cutting expenditures. Through sharing scientific talent, resources and knowledge it is possible for the industry to return from the drop of the patent cliff to emerge stronger by optimising the potential of collaboration. Pharmaceutical companies should consider working in unison for the common goal and share the rewards. This is important not just for the companies concerned but for the patients that benefit as a result.

Is it safe to reuse plastic bottles?

by Rachel Argo

Typically, I will buy a bottle of water and re-use it until I loose it. We all know that re-using a plastic bottle is good for both the environment and our pockets, but by doing this are we increasing our risk of exposure to ‘dangerous’ chemicals in the plastics? Recently bottles have been designed and marketed as being ‘BPA free’. But what is BPA and why have we never heard of it before?

Maybe you have seen strange shaped bottles with coloured filters appearing in people’s handbags, at the gym or on the high street? ‘Bobble’ bottles are an example of these BPA free plastic products. They are made from recycled materials, are recyclable and contain replaceable filters that claim to remove impurities in the water and improve the taste. Bisphenol A (BPA) is a synthetic organic molecule that is used to make certain plastics such as ‘polycarbonate’. Polycarbonate is commonly used to make household items like drinks bottles and tupperware. BPA is also found in epoxy resins that are used to line drinks cans and tins. We come into contact with plastic all the time and admittedly it would be very difficult to exclude from our day-to-day lives. Until recently no one questioned the effect of this plastic heavy lifestyle on our health, so should we stop re-using that water bottle and buy a BPA free one?

Studies have suggested that BPA possesses the ability to pass from the containers to the food or beverages inside. The concern around this possible seeping stems from the chemical’s ability to act as a mimic of the hormone oestradiol and therefore have potential to interrupt hormone patterns and signaling pathways. Animal studies in rats and mice have linked BPA exposure to a range of health problems such as obesity, fertility impairment, respiratory disorders and inflammation, however there is little or no research into the effects on humans and no single study that conclusively proves that BPA is the cause of these diseases. 

A review in 2006 by the European Food Safety Authority (EFSA), concluded that the Tolerable Daily Intake (TDI) of BPA was 0.05 mg/kg body weight/day. This value is an estimation of the amount of BPA that can be ingested per day per kg of body weight daily, over a lifetime without significant risk to health. BPA is licensed by the EU for use in food contact materials, however a directive in January 2011 prevented the use of BPA containing plastics in the manufacture of baby bottles. The most recent review of the molecule’s safety (July 2013) provisionally suggests that diet is the main source of exposure, that the estimation of this exposure is much lower than EFSAs previous estimations and well below the suggested TDIs. 

Due to the lack of conclusive evidence of BPA safety in humans and changing opinion on TDI values, it is hard to decide if it is worth investing in a BPA free bottle. I initially thought that this was a trendy case of false science, but on closer inspection it seems there may be some truth in their safety claims even if we have not established the extent of it.

Catalytic Clothing: How Your Jeans Can Purify Air

by Emilie Bergstrӧm

The UK frequently falls short of meeting EU air pollution emission targets, and it is estimated that air pollution is responsible for 50,000 deaths in the UK each year. Nitrogen oxides, NOx, and volatile organic compounds (VOCs), both produced in massive quantities from motor vehicles and industry, are two of the most prominent classes of pollutants. NOx are known to cause and worsen respiratory diseases, such as asthma and emphysema, and some VOCs are known carcinogens.

It has been known for some time that the harmful NOx and VOCs can be removed from the atmosphere via a catalytic conversion. Nanosized particles of titanium dioxide, TiO2, or nano-titania, are powerful photocatalysts that use sunlight and oxygen to speed up the oxidation of NOx into water soluble nitric acid that can be washed away with the rain, while also converting VOCs into fatty acids and soaps. 

Up until recently, nano-titania catalysts have only been placed on hard surfaces such as the walls of buildings. Helen Storey and Tony Ryan wanted to explore new applications of this technology. They contacted Cristal Global, the second largest supplier of nano-titania, to suggest collaborating on an initiative involving textiles. It was discovered that the efficacy of the catalyst when applied to textiles, particularly denim, was far higher than anticipated.

They have now partnered with the ecological cleaning brand, Ecover, to create a fabric softener able to deliver the photocatalyst to the surface of any piece of clothing during washing. The active agent is packaged within a shell that is attracted towards, and binds to, the surface of the clothing during the wash. Daily wear and washing create no problem for the catalyst particles, and they do not fall off until the cotton fibres of the jeans eventually break.

The key to catalysis, and increasing the rate of removal of NOx, is a high surface area. Nanoparticles have an extremely high ratio of surface area to volume and a pair of jeans has a surface area greater than 195 square feet. It has been estimated that if one person wears Catalytic Clothing for one day, they could remove the same amount of NOx as is produced by the average family in one day. 

A common misconception is that Catalytic Clothing will be a ‘dirt magnet’, putting people at greater risk of exposure to pollutants. This is not the case – the technology won't actively attract any pollutants, but will break down anything that comes within very close proximity of the catalyst's surface.

Lake turns animals into petrified statues

Greek mythology will tell you that Medusa was beheaded a long time ago, so those of you rooting for a supernatural or spiritual explanation I am sorry to disappoint. The real cause of this mummification is no less fascinating. Lake Natron, a vast death swamp located in northern Tanzania gets its name from Natron which is a naturally occurring sodium carbonate compound. The compound is sourced from volcanic ash which when collected by surface runoff, flows into the lake and provides the lake with an unnaturally high alkaline content.

Calcium is more readily precipitated from alkaline solutions so over time high amounts of calcium can be precipitated along the shoreline. When animals die and are immersed in the deadly waters of the lake they become petrified and turn into a bizarre and horrific spectacle. Oddly, the lake isn't completely lethal and is home to flocks of daredevil flamingos that return to nest on an annual basis. I should point out that the poses in the photographs are artificially created by photographer Nick Brandt.

by Danny Stubbs

Brinicles - ‘Icicles of Death’

by Danny Stubbs



Stretching down from the surface of the ocean, these Icy spikes give unfortunate bottom dwellers an unpleasant frosty fate. In short, they form when supersaline (very salty) water subsides from the surface of sea ice and sinks towards the seabed, forming an icy sheath during the process. This phenomenon was first filmed by the BBC as part of their series ‘The Frozen Planet’ in 2011.

So how do these sub-zero spears form? One of the main things you need to know is that salt lowers the freezing point of water by acting as an impurity. At 0°C (the freezing point of water and melting point of ice) there is an equal amount of molecules entering and leaving the solid state. Salt interrupts this exchange of water molecules and stops them entering the solid phase, hence the water remains in a liquid form. At a lower temperature the amount of molecules leaving the solid state balances the amount entering, allowing the water to freeze but at a lower temperature than freshwater. As a result saltwater freezes at minus two degrees Celsius.

As the seawater freezes the salt becomes concentrated because it doesn’t fit in with the lattice structure of the ice and it is cooled below zero degrees. This creates an area of water with high concentrations of salt (brine) at temperatures below freezing. Since salty water is denser than pure water and colder water is denser than warmer water, the brine begins to sink and forms a vertical column called a brine plume that stretches towards the seabed. The water around the column is cooled below zero and begins to freeze, forming a ‘Brinicle’.

What makes them important?Brinicles have a biological impact, they freeze any sluggish organisms that are too slow to escape the freezing of the seabed. However they also create areas that never fully freeze in regions such as in the Antarctic, which prove to be a vital refuge for some critters during the bleak winter months.These brine plumes are also important for the climate because they aid the circulation of water throughout the oceans of the world. The heavy supersaline water that sinks and migrates towards the equator helps replenish the cool water that warms and rises in areas such as the tropics. 

Check out these incredible time lapse images of the Brinicles forming.



While these principles are fresh in your mind, think about why we add salt to icy roads in the winter months. Did you figure it out? The salt lowers the melting point of ice so it more readily turns back into liquid form. Ice and salt – much more compelling than you originally thought!

Polymer Carpets

Hannah Bruce Macdonald

It seems as though every new development nowadays is on the nano-scale, and this is no exception. Professors from the University of Munich and the University of Dresden have improved a method for the synthesis of polymer carpets.

A Polymer Carpet

Polymer carpets are made by grafting styrene polymers onto copper supported graphene and these scientists have discovered that the carpet density and thickness depends on the hydrogenation of the graphene. Graphene is an incredible material, due to its versatility, but what makes it so useful as a support for making polymer carpets is how stable it is to mechanical and chemical influences. The team working on these carpets say that the ‘Polymer carpets exhibit remarkable and unprecedented properties combining extreme thinness, mechanical and chemical stability, robustness, flexibility, and (chemical) sensitivity’. The chemical sensitivity mentioned by the team may sound like a flaw, but this actually means that the nature of the carpet (effectively its thickness, fluffiness or tangled-ness) can be fine-tuned with changes in conditions like the solvent quality, wetting and pH.

Natural (left) and artificial (right) nacre

Polymer carpets are one of those materials that seem to be good at everything. They are similar to biological membranes, such as the outside layer of cells, but have the significant advantage of stability and the ability to withstand considerable pressure. This feature means they have been applied to use in water purification and desalination. Any developments in these fields are of huge importance globally and more research and discoveries in this field could make these polymer carpets a viable solution to the cleanliness of drinking water.

Another unsuspected use of these is in the synthesis of artificial nacre. If, like me, you don’t know what nacre is, it is mother of pearl, the shiny inside coating of some seashells and the outer surface of pearls. Pearls have had many uses over the years, but these tend to be mostly decorative, in jewellery or furniture, but are beginning to be applied in more areas. The pearl is originally made as a surface to protect the molluscs’ soft material from damage through bombardment and protection from parasites. Nacre is now being used as a novel material in medical surgery, as it has been shown to stimulate the growth of cartilage when injected into bones. The ability to make a Nacre alternative in the labs could prove to be advantageous, over having to source it from the sea.

Any improvements in the understanding of the mechanism or the synthesis of polymer carpets is useful, and allows a large step to be taken towards applications such as these, however the greatest use of these diverse materials could yet to be discovered.