Reputations take a long time to build but can be quickly destroyed

 US support for science is one of the things that will be hard to make reliable again.

Here's a story from the Washington Post, about and including an interview with the mathematician Terence Tao.

 The world’s greatest mathematician avoided politics. Then Trump cut science funding.  Terence Tao, often called the “Mozart of Math,” is focused on fundraising after federal research funding to UCLA was suspended.  By Carolyn Y. Johnson

" What’s hardest to restore is the sense of predictability and stability.

"People who support all the positive aspects of America have to speak out and fight for them now. The things that you took for granted, there was bipartisan support to keep certain things in the U.S. running as they have been more or less for the past 70 years because the system worked. That’s not a safe assumption anymore."

Sorority rush (but now even more so)

 The Atlantic has a story about the contemporary unraveling of sorority rush at Southern colleges: now rush is preceded by rush training...

What It Costs to Be a Sorority Girl,  Parents hire coaches for all sorts of extracurriculars; why not to train their daughters to make friends? By Annie Joy Williams 

"It may sound insane to hire someone to train your teenage daughter to talk to other teenage girls, but sorority rush, especially in the South, is a major undertaking. Parents invest in lots of kids’ activities; private coaching is now a common feature of competitive athletics. And getting their kids into the right sorority, parents believe, might help them make the kinds of connections that can get them job interviews someday. ... There are unspoken rules, secret ranking systems, decades of traditions to study, and some hard and fast dos and don’ts, according to Alverson: “You don’t talk about bucks; you don’t talk about boys; you don’t talk about booze,” he told me. “A lot of people say don’t talk about the Bible, but I don’t buy in to that one.” If church is important to you, he said, it’s okay to say that; just remember that “Jesus is not going through rush.”

########

Earlier:

Mongell, Susan, and Alvin E. Roth. "Sorority rush as a two-sided matching mechanism." The American Economic Review (1991): 441-464.

Psycho-social criteria for being accepted as a transplant candidate

 Not all decisions made in transplant centers are made on exclusively medical grounds.  Given the dire shortage of transplantable organs, other factors that predict transplant success are also examined.

The Harvard Gazette interviews Dr. Wei Zhang, a transplant hepatologist at Mass General Hospital.

Facing life-or-death call on who gets liver transplants
Surgeons, medical professionals apply risk calculus that gets even more complex for patients with drinking problems  by Anna Lamb

"Patients with decompensated liver disease, or what commonly has been referred to as end-stage liver disease, have drastically shortened life expectancies without transplantation. In one study, patients in this stage who developed complications lived only two years after diagnosis.

"But a transplant is not always a final solution. As many as 20 percent of all patients with a history of alcohol use disorder will relapse after surgery.

“If we know a patient is going to relapse after liver transplant, the evidence is that the chance of them developing recurrent cirrhosis in three years is about 50 percent and the chance of dying from the recurrent liver disease in five years is about 50 percent,” Zhang said. “We do a lot of interventions to prevent them from going back to drinking and improve their quality of life.”

...

“I also understand that if a patient receives an organ, it means that another patient is not able to receive the organ,” he said. “So when I think of that, I find a little bit of comfort.”

"In the last decade, the field of transplant hepatology has changed drastically. In the not-so-distant past, all patients coming into the hospital with a failing liver and any history of alcohol abuse were denied life-saving surgery.

“When I was doing my residency, most of those patients did not have any chance of being evaluated for liver transplantation,” Zhang said.

"Now, he added, there are still quite a few hurdles that patients need to clear to be approved for transplantation. But there’s hope — especially for those with strong support at home.

...

“Some of the factors that we look at is if a patient has insights, meaning, does the patient think that the liver disease is caused by alcohol?” Zhang said. “There are patients who, for various reasons — one of them is probably stigma — don’t acknowledge that the liver disease is caused by alcohol. The risk is that if they get a liver transplantation, and don’t think they need treatments, they may relapse.”

"The other piece of psychosocial criteria, Zhang said, is social support. This includes having strong family ties, stable housing, and the overall ability to seek support after surgery.

“Then those patients would be considered as good candidates with acceptable risk for post-liver-transplant relapse, and we can move on for a liver transplant evaluation,” Zhang said."

"Dark tourism" as a repugnant market in Germany

 NPR's Planet money has a story about tourists visiting the site of Hitler's bunker in Berlin, and about "dark tourism" more generally:

Hitler's bunker is now just a parking lot. But it's a 'dark tourism' attraction anyway By Greg Rosalsky 

"As Germany made intensive efforts to memorialize Nazi victims in the 1990s and 2000s, they also had to grapple with what to do about infamous sites associated with Nazi perpetrators, like the Führerbunker. Over the years, Germans have shown resistance to anything that gives any whiff of memorializing — or even depicting — Hitler and his henchmen.

...

"For years, the German government resisted even recognizing the location of the Führerbunker. Some found visitation of this site distasteful, and they feared any official recognition of it could help it become a kind of shrine for neo-Nazis.

"The Nobel Prize-winning economist Al Roth has developed a concept he calls "repugnant markets." This is when society has a distaste for particular kinds of market activity and may take actions to outlaw or discourage it. Examples he gives include prostitution, buying and selling human organs, ticket scalping, price gouging in the wake of disasters, and eating dog or horse meat. One might add dark tourism of politically sensitive places to Roth's list.

"Heyne says that, despite official reluctance to recognize the location of the Führerbunker and offer anything interesting for tourists to see there, tourists, with the help of guidebooks, came to the site anyways.

...

"And so, in 2006, the Berliner Unterwelten, with the approval of government authorities, erected the information plaque that still stands there today, the only official recognition that this site has historical significance. They chose to make the sign in both German and English. It shows a schematic of the Führerbunker (and a connected bunker known as the Vorbunker) and a timeline of key events at the site. It has a German title, "Mythos und Geschichtszeugnis Führerbunker," or, in English, roughly, the myth and historical record of the Führerbunker.

...

"Perhaps recognizing that many tourists were coming to the Führerbunker and getting disappointed there was nothing there, a Berlin history museum, in 2016, unveiled a full replica of Hitler's bunker that tourists can now go to. (This is kind of similar to other repugnant markets; despite efforts to discourage or even ban a market, demand often proves irrepressible and finds willing suppliers. Think of the failure of Prohibition)."

Rationing access to mud in the Thames

 There's a lot of mud in the Thames, but access to it is limited to when the tide is low (yes, the Thames has tides in the parts that are close enough to the North Sea, including London).  So treasure hunters known as mudlarks must have a permit from the Port of London Authority.

National Geographic has the story:

There’s a 10,000-person wait list to search for riches in London’s Thames
Mudlarking had long been a niche hobby. Then influencers discovered it. 

Twice a day, sections of the River Thames’s shores are exposed by the receding tide, allowing a growing number of mudlarks like Elaine Duigenan to hunt through the mud for treasure.
By Elizabeth Anne Brown

"For decades mudlarks have been granted permission to hunt along the Thames by the Port of London Authority (PLA), which issued permits for up to three years at a time to a small community of hobbyists. But during the pandemic that community grew dramatically, causing the PLA to upend their application process. They recently announced they are capping the total number of permits, each only valid for one year. To accommodate the surge in interest, the agency created a waiting list, which quickly increased to more than 10,000 people and was closed. Active permit holders could not join the list until their current permit was close to expiring, and many veteran mudlarks missed the window. They fear it might take years to get another permit."

 

Immigrants and the tech economy

 

 This picture, from a tech firm, speaks for itself.

 

The business of Sotheby's---the design of an auction house

 The New Yorker has a story about Sotheby's, focusing on its new owner, but with some interesting descriptions of the auction business.

How a Billionaire Owner Brought Turmoil and Trouble to Sotheby’s
Patrick Drahi made a fortune through debt-fuelled telecommunications companies. Now he’s bringing his methods to the art market.  By Sam Knight 

"A major auction house has many parts. “Sotheby’s is really three businesses, which had been run as one business,” a former employee who joined under Tad Smith told me. Since the late eighties, Sotheby’s has offered loans and other financial products, secured against art (in fact, anything that the auction house will sell) as collateral. When Drahi acquired the company, Sotheby’s Financial Services was lending around eight hundred million dollars a year.

"Next, there is everything under a million dollars in value: the wine, the jewelry, the furniture, the sneakers, the watercolors, the Hermès handbags. These are the collectibles—a nice watch, a decent painting, a rare manuscript, the family silver—that have kept the auction houses ticking for the better part of three centuries. The average price of a Sotheby’s lot is still around fifty thousand dollars.

"And then there is the top end. And the top end is where everything goes to hell. According to the consulting firm Arts Economics, less than half a per cent of works sell for more than a million dollars, and yet these lots make up more than half the total revenue of fine-art auctions. An even smaller fragment—sales of more than ten million dollars—contributes around a quarter."

Demand for surrogacy outstrips supply in England (where commercial surrogacy is illegal)

 Economics in action.

The Guardian has the story:

‘It’s overwhelming’: woman who was UK’s first surrogate closes agency as demand soars
Kim Cotton says laws, little changed since being rushed through in response to her pregnancy in 1985, are ‘dinosaur’  by Jessica Murray 

"Much has changed since Kim Cotton became the UK’s first surrogate 40 years ago, when she was forced to flee hospital on the floor of a car under a blanket, such was the level of media frenzy around her story.

...
"She has spent decades running the surrogacy agency Cots (Childlessness Overcome Through Surrogacy), facilitating more than 1,000 pregnancies. But in September she is closing its doors as soaring demand and a lack of surrogates is making the job more stressful than ever before.

...

"There are now about 400 children a year born through surrogacy to UK parents, up from about 50 a year before 2008, and more than half are now born through international surrogacy arrangements.

"Pro-surrogacy campaigners have blamed the stringent laws in the UK for pushing more people to seek surrogacy arrangements abroad, sometimes in countries with lax or nonexistent regulations. Waiting lists at many British surrogacy agencies are now years long.

“As soon as same-sex parents could go for a parental order, demand doubled, but supplies remained the same,” Cotton says. “There’s also just more infertility around.

...

"The UK’s surrogacy laws have changed little since they were first introduced in 1985, when they were rushed through parliament as a direct response to Cotton’s pregnancy.

"In 2023 the Law Commission published a report with suggested changes, including the creation of a national surrogacy register, and ensuring intended parents in domestic surrogacy arrangements can become parents from the child’s birth.

"Under current laws, intended parents have to apply for a parental order after birth, which can take months and create issues over who makes decisions about the baby’s healthcare in the first weeks of life.


...

“The laws are so antiquated, they’ve not changed since 1985 when I was a surrogate, but it was a kneejerk law that was passed. It’s fossilised. It’s a dinosaur. And it’s just on the back burner now. It’s a damn shame.”

"Campaigners were hopeful the Law Commission report would lead to reform, but the change of government in 2024 has pushed surrogacy to the bottom of the agenda.

"There is also strong opposition from those who are concerned that relaxing the laws could lead to people being coerced into surrogacy by financial need, or wealthy people outsourcing pregnancy because they have the resources to do so.

...

"As well as parental rights from birth, Cotton said she would like to see reform of the expenses system for surrogates. As commercial surrogacy is banned in Britain, advertising for surrogates is not permitted and only “reasonable expenses” are allowed to be paid.

Cotton says this seems to have been accepted as about £15,000-£20,000, although there is no official guidance around what is permitted.

“If the surrogate baby has been living with a couple since the baby was born, how are they going to say, well, no, actually I can’t give you a parental order because you paid a bit too much to the surrogate?” Cotton says. “So we need more clarity.”

Although she is closing down Cots, Cotton is reluctant to leave the world of surrogacy behind completely, and says she will continue to offer advice to people through a surrogacy advice line."

Abhijit Banerjee's column on food and economics, in The Times of India

 Abhijit Banerjee writes a monthly column on food (cooking it and eating it) and economics, in The Times of India

You can see them all at the link, but here's a recent example:

Trade wars and chocolate bars, what India of the 1970s can teach Trump  May 31, 2025,  Abhijit Banerjee in Tasting Economics

"One advantage/disadvantage of being old is that I lived through what is history to so many others. President Trump adores William McKinley, the 25th US president, for his tariffs, but at 78, he is way too young to have lived behind a properly high tariff wall. I, on the other hand, lived in the India of the 1970s, when we had managed to kill almost all international trade through a combination of tariffs and other rules for importing (non-tariff barriers in trade parlance).

I mostly experienced trade barriers through the important lens of chocolate."

Michel Callon (1945-2025)

 Hans Kjellberg  informs me that the eminent sociologist of markets, Michel Callon has died. Kjellberg writes about his long collaboration with Callon, including an interval during the Covid pandemic that involved the three of us:

"A more recent collaboration was the essay “The design and performation of markets: a discussion” that I curated between Alvin Roth and Michel for a special issue of AMS Review on theorizing markets (with Riikka Murto). I had spoken to Michel about contributing an essay to the issue, but when Alvin suggested that they do something together, Michel very quickly accepted this intellectual challenge. Their exchange took place at the height of the pandemic, and I acted as the go-between and facilitator of their (mostly email-based) exchange of ideas. It developed into a great example of what is needed in contemporary society: two intellectual giants coming from very different starting points engaging in an open and earnest conversation to try to understand each other’s point of view. If you have not yet read it, have a look at: https://lnkd.in/dBxJBbtW."

Here's the obit from the Centre for the Sociology of Innovation:

Michel Callon (1945-2025)

"Michel Callon passed away on July 28, 2025. 

...

"With an interest in economics (and economy) since his early days, Michel Callon developed a keen understanding of markets in the late 1990s, focusing on the role of scientific knowledge and technical devices. The 1998 collective volume he edited, The Laws of the Markets, paved the way for an original analysis of market phenomena that many researchers in France and other countries would follow. In Market Devices (2007), Callon, Yuval Millo, and Fabian Muniesa compiled a collection of texts emblematic of the variety of devices used in the organization of markets. In Market in the Making (2021), he analyses how market arrangements work and questions their integration into contemporary society. "

Here are all my blog posts mentioning  Callon.

The science and politics (and lawfare) of abortion pills with other uses in reproductive healthcare

Two recent articles shed some light on how the market for reproductive healthcare is evolving.

 Dr. Jessica Chen writes "I dispensed mifepristone every day in the clinic last week, and not once was it for abortion."  Instead it was to help patients who had suffered a miscarriage, and were still carrying a dead fetus.  

The US is expecting legal wrangling over whether mifepristone can be prescribed by telehealth providers, to women in states that forbid abortion.  Some of the arguments may depend on whether it is an "abortion pill," or a drug with multiple uses in reproductive healthcare.

The Clinical Indications for Mifepristone Go Beyond Abortion Jessica Chen, MD, JAMA
Published Online: August 28, 2025  doi: 10.1001/jama.2025.13376

#############

Considering Telehealth Across State Lines in Uncertain Times, by Nicole Huberfeld, JD1; Katharine O. White, MD, MPH2; Rachel Cannon, MD, MSc2, JAMA Published Online: August 11, 2025 doi: 10.1001/jama.2025.12122

"Since the US Supreme Court decided in 2022 that abortion was no longer protected as part of the constitutional right to privacy, state lawmakers have been empowered by the court leaving abortion policy “to the people and their elected representatives.”1 This phrase has fostered deep conflicts between state laws relating to abortion and laws relating to other health care for people of reproductive age, and it has created new risks for physicians who provide care to patients across state lines."

The Walras-Bowley Lecture: Fragmentation of Matching Markets and How Economics Can Help Integrate Them, by Kamada, Kojima, and Matsushita

 Fuhito Kojima's 2023 Walras Bowley Lecture has just been uploaded to arxiv, and it looks to be an exciting contribution to the market design literature.  It considers the fact that administrative boundaries cause many markets to be fragmented, and hence less thick than they might otherwise be, and how some of the resulting efficiency loss can be recovered.

The Walras-Bowley Lecture: Fragmentation of Matching Markets and How Economics Can Help Integrate Them, by Yuichiro Kamada, Fuhito Kojima, and Akira Matsushita
(August 27, 2025) 

Below is the abstract and opening paragraphs. 

"Abstract
Fragmentation of matching markets is a ubiquitous problem across countries and across applications. In order to study the implications of fragmentation and possibilities for integration, we first document and discuss a variety of fragmentation cases in practice such as school choice, medical residency matching, and so forth. Using the real-life dataset of daycare matching markets in Japan, we then empirically evaluate the impact of interregional transfer of students by estimating student utility functions under a variety of specifications and then using them for counterfactual simulation. Our simulation compares a fully integrated market and a partially integrated one with a “balancedness” constraint—for each region, the inflow of students from the other regions must be equal to the outflow to the other areas. We find that partial integration achieves 39.2 to 59.6% of the increase in the child welfare that can be attained under full integration, which is equivalent to a 3.3 to 4.9% reduction of travel time. The percentage decrease in the unmatch rate is 40.0 to 52.8% under partial integration compared to the case of full integration. The results suggest that even in environments where full integration is not a realistic option, partial integration, i.e., integration that respects the balancedness constraint, has a potential to recover a nontrivial portion of the loss from fragmentation.

Introduction
Many of the most consequential markets in our societies—school admissions, medical resident matching, daycare placements, kidney exchanges—are matching markets, where centralized mechanisms are often employed to improve efficiency and fairness. Over the past several decades, the field of market design has made substantial progress in developing and implementing such mechanisms (e.g., Abdulkadiroğlu and Sönmez (2003) for school choice, Roth (1984) for medical residency matching, Kamada and Kojima (2023) for daycare placements, and Roth et al. (2004) for kidney exchanges). In doing so, it has led economists to assume a dual role as both analysts and engineers (Roth, 2002).

How are those sophisticated mechanisms implemented in practice? Typically, these mechanisms are run by individual cities, districts or institutions, and the implementation is usually confined to narrowly defined administrative or political boundaries. These boundaries can reflect long-standing institutional arrangements, localized funding responsibilities, or jurisdictional autonomy. Regardless of their origins, the consequence is that agents on different sides of a boundary are matched as if they participated in entirely separate markets—even when they live mere blocks apart.

The aim of this paper is to study the implications of fragmentation of matching markets and possibilities for integration. To do so, we begin by offering a detailed descriptive account of fragmented matching markets in practice. We observe that fragmentation is prevalent across a variety of settings globally, from public school systems and childcare allocation to medical residency assignments, foster care placements, and public housing markets, among others. We highlight how institutional boundaries and localized governance create fragmented, parallel markets. Each case underscores the potential inefficiencies due to constrained choices caused by fragmentation, motivating our inquiry into mechanisms that can integrate markets effectively.

Against this background, we then investigate public daycare assignment in Japan in detail. "

Stanford kidney conference, recap

 Stanford Impact Labs (SIL) reports on our recent kidney exchange conference

Global Solutions-focused Summit on Expanding Access to Kidney Transplantation held at Stanford. Physicians, scholars, healthcare practitioners, and policymakers gathered to explore research advances underway in India, Brazil, and the U.S.   by Kate Green Tripp and Marina Kaneko

 "Earlier this month, the Alliance for Paired Kidney Donation (APKD), Stanford economist Alvin E. Roth, and Stanford Impact Labs hosted the Palo Alto Summit, a two-day global convening at Stanford University dedicated to exploring challenges and advances in kidney transplantation around the world.

"On the heels of the 2025 World Transplant Congress in San Francisco, more than 30 physicians, scholars, transplant coordinators, and government officials from the U.S., India, Brazil, Italy, the United Arab Emirates, Qatar, and South Africa gathered to share key learnings, challenges, and advances in the field.

...

" APKD and Roth, the Craig and Susan McCaw Professor of Economics at Stanford’s School of Humanities and Sciences, have teamed up with transplant specialists in India, Brazil, and the United States to form the Extending Kidney Exchange project. 

...

"The summit’s sessions were designed to advance national efforts in KPD in India and Brazil, and deceased donor-initiated chains (DDIC); foster collaboration among leading clinical, policy, and academic partners; and identify actionable steps and shared milestones for KPD in India and Brazil, paired liver exchange in India, and DDIC in the United States. As a transplant strategy, DDIC utilizes kidneys from deceased donors to create a chain of transplants so as to maximize the use of available organs and to connect multiple recipients, especially when there are mismatches or compatibility issues.

...

"“When the very first [nonsimultaneous] chain of kidney transplants took place in 2006, it was not necessarily welcomed as an innovation,” recalls Michael Rees, a transplant surgeon at the University of Toledo and founder of the Alliance for Paired Kidney Donation (APKD). “It is incredibly exciting to reflect on the progress we’ve been able to make across the transplant community since that time, to increase the utility of a single kidney from either a living or deceased donor.”

 

 

##########

Earlier:

Thursday, August 7, 2025 Stanford conference on extending kidney exchange

 

Also of note:

Matthew Gentzkow Named Director of Stanford Impact Labs

"The economist will lead a community of social scientists who want their scholarship to improve people’s lives."
 

 

"Better to exchange kidneys than bombs."

 Some coffee cups  should naturally come in pairs, so that you have one for a friend in need. (These recently arrived in the mail, from Laurie Lee)

Better to exchange kidneys than bombs

I was quoted as having said that to Marco della Cava, the USA Today reporter who wrote about the first kidney exchange between Israel and the UAE.

“Better to exchange kidneys than bombs,” says Roth, adding that using computers to search the world for medical solutions radically increases the chances of patients getting help. “International boundaries are artificial markers. Kidney disease doesn’t care about that.”

Thursday, September 30, 2021 Kidney Exchange between Israel and the UAE (in USA Today, yesterday)

How three Jewish and Arab families swapped kidneys, saved their mothers and made history by Marco della Cava, USA TODAY, Wed, September 29, 2021 AM 

In China, you can hire a woman to disrupt a husband's extra-marital affair

 The Guardian reviews a movie about a kind of covert marriage therapy becoming available in China, in which a 'mistress dispeller" is hired to intervene and covertly disrupt the relationship between a wayward husband and a mistress, with the aim of returning him to his wife.

If your husband’s having an affair, this woman will get rid of her: the gripping film about China’s ‘mistress dispellers’
Available for hire, professional persuaders deceive their way into the lives of cheating men – and see off the extra lover. We meet the maker of a jaw-dropping documentary about a growing phenomenon  by Amy Hawkins

"Wang Zhenxi, a mistress dispeller based in north-central China’s Henan province, is one of a growing number of self-styled professionals who earn a living by intervening in people’s marriages – to “dispel” them of intruders

...

"Teacher Wang’s profession, if it can be called that, has only become a phenomenon in China in the last 10 years. As the country grapples with falling marriage rates, rising divorce rates and an increasing number of young people refusing to wed altogether, an entire “love industry” aimed at promoting and protecting the institution of marriage has emerged. There are dating camps, government-sponsored marriage initiatives and even dating apps aimed at parents wanting to set their unattached children up with partners. “Divorce is easy,” says Teacher Wang’s assistant on a live stream. “It’s easy to just leave. It’s harder to take responsibility and provide your family with a good life.”

...

But while the struggle to find love is a universal one, hiring someone to pretend to be an old friend – so that they can persuade your husband to end his affair on your behalf – is not. Some viewers might wonder why the wife doesn’t just suggest couples therapy. Lo explains that, according to Teacher Wang, therapy is still very stigmatised in China. “To enter as a stranger and a professional into a private setting and ask someone to divulge their family struggles would be unthinkable.” Teacher Wang “would be ejected immediately”.

Meat and dairy allergy ( to alpha-gal), ticks and gene-modified pigs

 A previously rare allergy to a sugar molecule called alpha-gal, found in almost all mammals but humans, is now being spread by tick bites.  But alpha-gal is also the sugar that is genetically engineered out of pigs that are being bred for xenotransplants. So there may be a secondary market for pork chops from those pigs... 

‘We can no longer eat burgers or ice cream — all because of a tick bite’
A bug-borne disease has taken over Martha’s Vineyard and is turning people vegan, locals claim.  by Samuel Lovett 

"Sufferers cannot eat any food products that contains alpha-gal, a sugar molecule carried by the lone star tick and which is present in all mammals — except humans and some monkeys. This means cheeses, milk and meats from beef to venison are all off the menu. For some, even white sugar cannot be tolerated because it is processed using animal-bone char.

"Alpha-gal symptoms including hives, stomach cramps, vomiting and breathlessness often start to appear several hours after eating foods containing the molecule, giving the syndrome its nickname “the midnight allergy”.

...

"Although the prevalence of alpha-gal syndrome on Martha’s Vineyard has rocketed in recent years, the island is “definitely not the worst off”, said Roden-Reynolds. Data from the Centers for Disease Control and Prevention indicates that the Midwest has the highest rates per capita, and the agency estimates that about 450,000 people are living with the disease in the US."

 

Chocolate fermentation and its microbiome (coming to desserts near you)

 The Guardian brings us the latest breakthrough in chocolate science:

Scientists claim to have unlocked ‘secret sauce’ needed for fine chocolate
Results of studying cocoa bean fermentation in Colombia could pave way to manipulate flavour, say researchers  by Nicola Davis 

"Whether you enjoy an aromatic bar with notes of caramel or something less fancy, chocolate can have many tastes. Now researchers say they have shed fresh light on a key ingredient that could open the door to new flavours.

They claim to have unpicked how and why the bacteria and fungi involved in the fermentation of cocoa beans influence the flavour of chocolate.

“We understand now what microbes we need and what they’re doing. And I think that opens up the opportunity … to be a lot more directed [about] how we make our chocolate in terms of its flavour,” said Prof David Salt, co-author of the work from the University of Nottingham.

Writing in the journal Nature Microbiology, the team report how they studied beans fermented at cocoa farms in three different regions of Colombia – Santander, Huila and Antioquia.

...

"The team then used genetic sequencing to identify the microbes involved in cocoa bean fermentation from multiple sites in Colombia and beyond, explore the genes they contained, and hence identify the flavour substances they could produce during fermentation.

As a result, the researchers identified nine microbes that together were predicted to produce the notes of a fine flavour cocoa. They then introduced this community to sterile cocoa beans, and allowed them to ferment.

The upshot, said Salt, was a cocoa with floral, fruity and citrus notes and a recognisable cocoa flavour but with reduced astringency and bitterness."