Spain’s prime minister, Pedro Sánchez, has vowed to “get to the bottom” of the unprecedented power cut that hit the Iberian peninsula on Monday, as energy operators in Spain and Portugal ruled out the possibility of a cyber-attack.

The blackout, which plunged cities into darkness and left tens of thousands of travellers trapped on trains, is thought to have led to the deaths of at least five people in Spain. A family of three died from apparent carbon monoxide poisoning after using a generator in the north-west of the country, while a woman died in Valencia after her oxygen machine failed. Another woman died in Madrid in a fire started by a candle.

Speaking on Tuesday morning after electricity had been restored to both countries, Sánchez said that while it was still too early to know exactly what had gone wrong with the power supply, lessons would be learned to prevent any further large-scale blackouts.

“It’s clear that what happened yesterday can’t happen again,” he said, as he announced the creation of a commission to investigate the incident, which will also examine the role of private energy companies.

The prime minister said his administration would “get to the bottom of this matter”, carrying out any necessary reforms and enacting any necessary measures to ensure there was no repetition of Monday’s events.

Portugal’s prime minister, Luís Montenegro, said his government would ask the EU’s Agency for the Cooperation of Energy Regulators to perform “an independent audit of the electrical systems of the affected countries to fully determine the causes of this situation”.

Despite energy providers in Spain and Portugal concluding that a cyber-attack was not to blame for the loss of power, Sánchez once again stressed that “no hypothesis” was being ruled out while the country’s intelligence services continued their investigations and analysis.

The prime minister also warned people to be on the lookout for fake news that was still circulating, and dismissed suggestions that the blackout was the result of his administration’s decision to phase out nuclear power.

“Those who link this incident to the lack of nuclear power are frankly lying or demonstrating their ignorance,” Sánchez said, adding that nuclear power generation “was no more resilient” than other electricity sources.

Not long after he spoke, Spain’s highest criminal court, the Audiencia Nacional, said it had opened an investigation to determine whether “an act of computer sabotage” could have been perpetrated “against critical Spanish infrastructure”. Announcing the investigation, a judge at the court said cyberterrorism was “among the possible explanations” for the blackout.

Hours earlier, however, Spain’s electricity operator, Red Eléctrica, said the blackout was not the result of a targeted attack.

The operator’s head of services, Eduardo Prieto, said preliminary investigations meant “we can rule out a cybersecurity incident”, adding that there was nothing to suggest “there was any kind of intrusion into the Red Eléctrica control system”.

Prieto said two consecutive events, which took place at 12.32pm on Monday and then a second and a half later, pointed to a “generation disconnection” that had cut off the supply across the peninsula. While the system weathered the first event, it could not cope with the second. Prieto said the problem had originated in south-west Spain, which is where much of the country’s solar energy is generated.

The Portuguese government also ruled out a cyber-attack.

“In Portugal, we have no information related to a cyber-attack or a hostile act at this stage,” a government spokesperson told CNN Portugal, adding: “There would seem to have been an issue in the power transmission network [in Spain].”

By late Tuesday morning, all of Spain’s electricity substations were back up and running and all of the country’s power supply had been restored. Across the border in Portugal, the electricity operator REN said all substations were fully operational and the national network had been “perfectly stabilised” by 11.30pm on Monday.

In a statement early on Tuesday, Spain’s national meteorological office, Aemet, appeared to rule out the weather as a possible culprit. “During the day of 28 April, no unusual meteorological or atmospheric phenomena were detected, and nor were there sudden variations in the temperature in our network of meteorological stations,” said Aemet.

REN also said it had not sent a message circulating on social media on Monday attributing the blackout to a rare atmospheric event. The message, in Portuguese, claimed the shutdown was due to “a fault in the Spanish electricity grid linked to a rare atmospheric phenomenon”.

“REN confirms we did not put out this statement,” a spokesperson told Agence France-Presse.

All of Spain’s airports were operating on Tuesday morning, but the transport ministry advised people to check with their airlines for possible changes and to find out whether they would be able to get to the airport on public transport.

The state rail operator, Renfe, said the country’s train network, which was badly hit by the blackout, was gradually returning to normal but that local train services were suspended in regions including Murcia, Extremadura and Andalucía.

About 35,000 people were rescued from more than 100 trains after the power cut hit on Monday.

Widespread outages are unusual in Europe. In 2003, a problem with a hydroelectric power line between Italy and Switzerland caused blackouts for about 12 hours, and in 2006 an overloaded power network in Germany caused electricity cuts across parts of the country and in France, Italy, Spain, Austria, Belgium and the Netherlands.

Spain and Portugal suffered the worst blackout in living memory in Europe this week. About 55 million people were affected and it lasted more than half a day. Some have blamed renewables and net zero emissions targets, as the two countries boast high levels of wind and solar on their electricity grid and lead Europe in the technologies. But is this true?

Spain and Portugal suffered the worst blackout in living memory in Europe this week. About 55 million people were affected and it lasted more than half a day. Some have blamed renewables and net zero emissions targets, as the two countries boast high levels of wind and solar on their electricity grid and lead Europe in the technologies. But is this true?

The White House accused Amazon of committing a “hostile and political act” after a report said the e-commerce company was planning to inform customers how much Donald Trump’s tariffs would cost them as they shopped.

The press secretary, Karoline Leavitt, was responding to a report in Punchbowl News, which, citing a person familiar with the matter, reported that Amazon would begin displaying on its site how much the tariffs had increased the prices of individual products, breaking out the figure from the total listed price.

“Why didn’t Amazon do this when the Biden administration hiked inflation to the highest level in 40 years?” Leavitt asked during a press briefing.

Amazon’s online marketplace has seen prices rise across the board since Trump announced sweeping tariffs at the start of April, particularly on China, where many products listed on Amazon.com ship from. In response, the company has pressured its third-party sellers to shoulder the burden of the extra import costs rather than pass them on to customers. Amazon did not immediately respond to a request for comment.

“This is another reason why Americans should buy American,” Leavitt continued, though Amazon is headquartered in Seattle.

Amazon moved to distance itself from the report, saying the idea had been considered by Amazon Haul, the company’s recently launched low-cost shopping hub, but had been rejected.

“The team that runs our ultra-low-cost Amazon Haul store considered the idea of listing import charges on certain products. This was never approved and is not going to happen,” said Tim Doyle, Amazon spokesperson.

Online shopping has been upended by Trump’s trade policies. The day before the White House took aim at Amazon, discount retailers Temu and Shein, which ship from China, began displaying 145% “import charges” in customers’ totals to reflect the surcharge on Chinese goods.

Asked if the strident statement from the White House signaled a rift between Trump and Amazon’s billionaire founder, who stepped down as CEO in 2021 and donated $1m to Trump’s inauguration fund earlier this year, Leavitt said: “I will not speak to the president’s relationships with Jeff Bezos.”

Recovery operations to raise the 56-metre British-flagged superyacht Bayesian from the seabed off Sicily, where it sank last summer killing seven people – including the British tech entrepreneur, Mike Lynch – will begin on Wednesday, weather permitting, according to the Italian port authorities.

On 19 August 2024, the luxury vessel, with a 75-metre (246ft) mast, was anchored just off shore near the port of Porticello, in the province of Palermo, when it was struck shortly before dawn by a violent storm. Lynch, once described as Britain’s Bill Gates, and his 18-year-old daughter, Hannah, were among the victims.

Lynch, who in June last year was cleared of fraud charges in the US relating to the purchase of his company, Autonomy, by Hewlett-Packard in 2011, was enjoying a lavish voyage around Sicily to celebrate his acquittal alongside Hannah, and his wife, Angela Baraces, whose company owned the Bayesian. They were joined by eminent figures including Lynch’s attorney from Clifford Chance, Chris Morvillo, and Morgan Stanley International’s chair, Jonathan Bloomer, along with their spouses, Judy and Neda, all four of whom died in the incident. The yacht’s chef, Recaldo Thomas, was the seventh person who died.

Fifteen people survived, including Baraces.

Investigators hope the yacht will yield vital clues: whether a series of human errors led to the sinking, as initially suspected, or if other factors were at play. Once ashore, forensic examination will determine if one of the hatches remained open and whether the keel was improperly raised.

The wreckage sits at a depth of 50 metres in the bay of Porticello, which is under surveillance by Italian authorities.

Experts expect the salvage operation to be fiendishly complex.

Sicilian port officials have declared a 650-metre exclusion zone around the sunken vessel, forbidding ‘‘any navigation, anchoring, diving, swimming or fishing until the work is complete’’. The recovery, which could stretch on for weeks, has been entrusted to Hebo Maritiemservice and Smit International.

A 55-metre barge, the Hebo Lift 2, will arrive in Porticello soon, its 700 m² deck bristling with a heavy-lift crane, specialist diving apparatus and a remotely operated underwater vehicle. Offshore, the Hebo Lift 10 – one of Europe’s largest floating cranes – will use its 83-metre boom to hoist the yacht from the seabed.

To facilitate the lift, the master mast of the Bayesian – standing 75  metres tall and weighing over 24 tonnes – will be cut away. Once raised, the vessel will be towed to Termini Imerese, where prosecutors have opened an inquiry into suspected manslaughter. The captain, James Cutfield, a New Zealander, and two British crew members, Tim Parker Eaton and Matthew Griffiths, have been placed under investigation.

Being put under investigation in Italy does not imply guilt and does not mean formal charges will necessarily follow.

Insurers estimate the salvage will cost about $30 million (£22.4 million), a bill the Bayesian’s underwriters will pick up.

Experts are baffled by how the Bayesian sank within 60 seconds. Some experts speculate the crew may have underestimated the weather bulletin.

Search efforts began within hours of the incident, with divers from the fire brigade working non-stop.

The first body to be recovered was that of Thomas, on the afternoon of the sinking. Two more bodies were recovered two days later, those of Bloomer and Morvillo. In the afternoon, their spouses were also found.

The following day, Mike Lynch’s body was found and a few hours later divers recovered the body of his daughter, Hannah, the seventh and final victim.

All of their bodies have undergone postmortem examinations.

Lucio Di Mauro, a forensic doctor and technical consultant for the Morvillo’s family, said the victims all died due to “so-called mechanical asphyxia by drowning”.

“It is important to clarify that, in forensic medicine, the determination of death by drowning is particularly complex, as there is no single pathognomonic lesion that alone allows for an incontrovertible diagnosis,” Di Mauro added. ‘‘Nevertheless, the data collected are consistent with this pathophysiological mechanism.”

Last September, Italian authorities requested additional security around the wreck of the luxury yacht Bayesian, after fears were raised that material in watertight safes onboard could be of interest to foreign governments.

The authorities were reportedly concerned that two super-encrypted hard drives in the sunken yacht’s watertight safes could fall into the wrong hands.

Lynch was believed to have connections to British, American and other intelligence services and had sold Darktrace, a cybersecurity artificial intelligence company he founded, to US billionaire Orlando Bravo, co-founder and managing partner of Chicago-based Thoma Bravo, in a $5.3bn (£4bn) deal earlier last year.

US sailors had to leap for their lives when a fighter jet fell off a navy aircraft carrier that was reportedly making evasive maneuvers to avoid Houthi militant fire in the Red Sea on Monday.

The F/A-18 fighter Super Hornet jet, along with the vehicle towing it into place on the deck of the USS Harry S Truman, rolled right out of the hangar and into the water, the navy said.

Unnamed US officials indicated to CNN that the ship was swerving to avoid incoming fire from Yemen’s Houthi rebel force. Carriers make a zigzag maneuver when attempting to evade missile fire, causing them to list to one side.

An official account of the ship’s movements was awaited on Tuesday as an investigation was being carried out.

The Truman has been patrolling in the Middle East for several months, and recently had its stint extended by the defense secretary, Pete Hegseth.

It is one of two US aircraft carriers operating in the area, where US forces have been striking the Houthis on a near daily basis using fighter jets, bombers, ships and drones.

“The F/A-18E was actively under tow in the hangar bay when the move crew lost control of the aircraft. The aircraft and tow tractor were lost overboard,” the navy said. The jet was part of Strike Fighter Squadron 136.

The crew members who were in the pilot seat of the Super Hornet and on the small towing tractor both jumped out before the jet and the tug went into the Red Sea. Fighter jets are routinely towed around the hangar deck to park where they are needed.

Monday’s incident was the second F/A-18 operating off the Truman to be lost in six months, after one was mistakenly shot down by the USS Gettysburg late last year.

Associated Press contributed reporting

US sailors had to leap for their lives when a fighter jet fell off a navy aircraft carrier that was reportedly making evasive maneuvers to avoid Houthi militant fire in the Red Sea on Monday.

The F/A-18 fighter Super Hornet jet, along with the vehicle towing it into place on the deck of the USS Harry S Truman, rolled right out of the hangar and into the water, the navy said.

Unnamed US officials indicated to CNN that the ship was swerving to avoid incoming fire from Yemen’s Houthi rebel force. Carriers make a zigzag maneuver when attempting to evade missile fire, causing them to list to one side.

An official account of the ship’s movements was awaited on Tuesday as an investigation was being carried out.

The Truman has been patrolling in the Middle East for several months, and recently had its stint extended by the defense secretary, Pete Hegseth.

It is one of two US aircraft carriers operating in the area, where US forces have been striking the Houthis on a near daily basis using fighter jets, bombers, ships and drones.

“The F/A-18E was actively under tow in the hangar bay when the move crew lost control of the aircraft. The aircraft and tow tractor were lost overboard,” the navy said. The jet was part of Strike Fighter Squadron 136.

The crew members who were in the pilot seat of the Super Hornet and on the small towing tractor both jumped out before the jet and the tug went into the Red Sea. Fighter jets are routinely towed around the hangar deck to park where they are needed.

Monday’s incident was the second F/A-18 operating off the Truman to be lost in six months, after one was mistakenly shot down by the USS Gettysburg late last year.

Associated Press contributed reporting

The first 27 satellites for Amazon’s Kuiper broadband internet constellation were launched into space from Florida on Monday, kicking off the long-delayed deployment of an internet from space network that will rival SpaceX’s Starlink.

The satellites are the first of 3,236 that Amazon plans to send into low-Earth orbit for Project Kuiper, a $10bn effort announced in 2019 to beam broadband internet globally for consumers, businesses and governments – customers that SpaceX has courted for years with its powerful Starlink business.

Sitting atop an Atlas V rocket from the Boeing and Lockheed Martin joint-venture United Launch Alliance, the batch of 27 satellites was lofted into space at 7pm EDT from the rocket company’s launch pad at the Cape Canaveral Space Force Station. Bad weather scrubbed an initial launch attempt on 9 April.

Kuiper is arguably Amazon’s biggest bet under way, pitting it against Starlink as well as global telecommunications providers like AT&T and T-Mobile. The company has positioned the service as a boon to rural areas where connectivity is sparse or nonexistent.

The mission to deploy the first operational satellites has been delayed more than a year – Amazon once hoped it could launch the inaugural batch in early 2024. The company faces a deadline set by the US Federal Communications Commission to deploy half its constellation, 1,618 satellites, by mid-2026, but its slower start means Amazon is likely to seek an extension, analysts say.

Hours or possibly days after the launch, Amazon is expected to publicly confirm initial contact with all of the satellites from its mission operations center in Redmond, Washington. If all goes as planned, the company said it expects to “begin delivering service to customers later this year”.

ULA could launch up to five more Kuiper missions this year, the ULA CEO, Tory Bruno, told Reuters in an interview this month. Amazon said in a 2020 FCC filing that it could begin service in some northern and southern regions at 578 satellites, with coverage expanding toward Earth’s equator as the company launches more satellites.

The web services and e-commerce giant’s Project Kuiper is an ambitious foray into space, with a late start in a market dominated by SpaceX. But Amazon executives see the company’s deep consumer product experience and established cloud computing business that Kuiper will connect with as an edge over Starlink.

Amazon launched two prototype satellites in 2023 in tests it said were successful, before de-orbiting them in 2024. It had been relatively quiet about the program’s development until announcing its first Kuiper launch plans earlier this month.

Elon Musk’s SpaceX, with a unique edge as both a satellite operator and launch company with its reusable Falcon 9, has put more than 8,000 Starlink satellites in orbit since 2019, marking its 250th dedicated Starlink launch on Monday. Its deployment pace has hastened to at least one Starlink mission a week, each rocket with roughly two dozen satellites on board to expand the network’s bandwidth and replace outdated satellites.

That quick pace has helped Musk’s company amass more than 5 million internet users across 125 countries, upend the global satellite communications market and woo military and intelligence agencies that have sought to use Starlink and its manufacturing line for sensitive national security programs.

The Amazon executive chair, Jeff Bezos, has voiced confidence that Kuiper can compete with Starlink, telling Reuters in a January interview “there’s insatiable demand” for internet.

“There’s room for lots of winners there. I predict Starlink will continue to be successful, and I predict Kuiper will be successful as well,” he said.

“It will be a primarily commercial system, but there will be defense uses for these LEO constellations, no doubt,” he added, referring to low-Earth orbit.

Amazon in 2023 revealed its Kuiper consumer terminals, an LP vinyl record-sized antenna that communicates with Kuiper satellites overhead, as well as a smaller terminal whose size it compares to its e-book Kindle device. The company expects to make tens of millions of the devices for under $400 each.

Amazon in 2022 booked 83 rocket launches from ULA, France’s Arianespace and Blue Origin, Bezos’s space company, snagging the industry’s biggest-ever launch deal as it prepared to begin Kuiper deployment.

The European court of justice has ruled that Malta’s “golden passport” scheme is illegal, meaning its cash-for-citizenship programme must be scrapped.

In a long-awaited ruling on Tuesday, the EU’s top court concluded that Malta’s investor citizenship scheme was contrary to EU law. Judges said the scheme represented a “commercialisation of the grant of the nationality of a member state” and by extension EU citizenship, which was at odds with European law. Malta had jeopardised the mutual trust between EU member states necessary to create an area without internal borders, the court argued.

The judges examined a 2020 scheme that allowed people who had given up to €750,000 to Malta and – in theory – spent 12 months in the country to gain citizenship. With a Maltese passport, the person gained EU citizenship and the freedom to live and work anywhere in the union.

The scheme, which had its origins in a 2013 law, has long been criticised by transparency campaigners, who said it opened the door to money laundering, corruption and security risks. In 2021 a Guardian investigation found that multimillionaires with minimal genuine links to Malta were being granted citizenship, sometimes spending only three weeks in the country.

A cache of emails from the Daphne Caruana Galizia Foundation, known as the Passport Papers and shared with international media including the Guardian, revealed that many people claiming to be residents left their Maltese rental properties empty. The Commission referred to the Passport Papers in its arguments to the court, according to the judgement.

The European Commission launched legal proceedings against Malta and Cyprus in October 2020 for selling “EU citizenship”. Cyprus announced it was closing its scheme shortly before the case was launched, but Malta’s government was defiant. In submissions to the court it argued it had exclusive competence to grant nationality, so was entitled to run the scheme.

Responding to the ruling, Malta’s government said it was studying the legal implications, “so that the regulatory framework on citizenship can then be brought in line with the principles outlined in the judgment”.

But it also touted the benefits of the scheme, saying it had generated more than €1.4bn in revenues for the government since 2015.

In a Facebook post, the former prime minister Joseph Muscat claimed the verdict was a political judgment. Muscat was the prime minister when the golden passport scheme was introduced. He resigned in 2020 in response to widespread anger over his perceived attempts – which he denies – to protect allies from an investigation into the 2017 murder of the journalist Daphne Caruana Galizia.

Golden passport schemes sprang up across Europe as cash-strapped governments looked to raise money after the financial crisis. The British government announced in February 2022 that it was scrapping the UK’s “tier 1 investor visa” amid corruption and national security concerns and worsening relations with Russia.

In contrast, Donald Trump announced in February he planned to launch a “gold card” visa, a $5m residency permit for wealthy foreigners.

Matthew Caruana Galizia, the director of the foundation that works to secure his mother’s public interest legacy, described the court judgment as “a win for the people of Malta and for all EU residents who have been unfairly exposed to the whims of money launderers and corrupt criminals buying their way into the EU”. He urged the government “to abolish its citizenship-by-investment programme without delay”.

A European Commission spokesperson welcomed the court decision and called on Malta to implement the judgment: “European citizenship is not for sale,” the spokesperson said. “Investor citizenship schemes breach EU law and as such should be abolished by all member states.”

Brendan Cox, the husband of the murdered MP Jo Cox, has said the Irish rap trio Kneecap have offered only “half an apology”, after criticism of comments in which they appear to call for politicians to be killed.

Kneecap apologised to Jo Cox’s family and that of the MP David Amess, who was also murdered, in the face of mounting criticism, including from Downing Street and Kemi Badenoch, the Conservative leader.

Cox’s remarks come after a video emerged from a November 2023 gig appearing to show a member of the Belfast group saying: “The only good Tory is a dead Tory. Kill your local MP.” The group have also denied allegations they have shown support for Hamas and Hezbollah.

Overnight on Monday, Kneecap – Liam Óg Ó Hannaidh, Naoise Ó Cairealláin and JJ Ó Dochartaigh – posted an apology on X and suggested the condemnation had been an “effort to derail the real conversation” about Gaza.

The band have previously claimed they are facing a “coordinated smear campaign” after speaking out about “the ongoing genocide against the Palestinian people”.

“To the Amess and Cox families, we send our heartfelt apologies, we never intended to cause you hurt,” they said in the 500-word statement. They went on: “Establishment figures, desperate to silence us, have combed through hundreds of hours of footage and interviews, extracting a handful of words from months or years ago to manufacture moral hysteria.”

During an urgent question about the band in the Commons on Tuesday, the Home Office minister Dan Jarvis urged the organisers of June’s Glastonbury festival to “think very carefully” about whether Kneecap should perform there.

During the exchanges, which involved Mark Francois, the Conservative MP who asked the question, referring to the band as “despicable evil”, Jarvis seemingly agreed with another Labour MP who suggested Kneecap’s music should be removed from platforms such as iTunes and Spotify.

Cox told BBC Radio Ulster’s Talkback programme that Kneecap’s most recent statement was only “half an apology”.

“It’s fine to say that you’re sorry for it, but the way that they have actually spoken about it is to suggest that it’s a conspiracy, that they have been targeted unfairly, and for me, that then doesn’t come across as unfortunately particularly genuine,” he said.

Jo Cox was killed in June 2016 by a far-right extremist.

Kneecap said in their most recent statement they “do not, and have never, supported Hamas or Hezbollah”.

They added: “We also reject any suggestion that we would seek to incite violence against any MP or individual. Ever. An extract of footage, deliberately taken out of all context, is now being exploited and weaponised, as if it were a call to action. This distortion is not only absurd – it is a transparent effort to derail the real conversation.”

Keir Starmer’s official spokesperson said on Monday the prime minister believed the band’s comments were “completely unacceptable” and that he “condemns them in the strongest possible terms”.

Katie Amess, whose father, David Amess, was murdered by an Islamic State fanatic in his Southend West constituency, said she was “gobsmacked at the stupidity of somebody or a group of people being in the public eye and saying such dangerous, violent rhetoric”, and demanded an apology.

Scotland Yard is reportedly looking into the alleged call to kill MPs, along with another concert from November 2024 in which a member of the band appeared to shout: “Up Hamas, up Hezbollah” – groups that are banned as terrorist organisations in the UK.

It may be only pasta, pecorino and black pepper, but cacio e pepe is not nearly as easy to make as some would imagine.

However, researchers have come up with a scientific recipe that avoids a lumpy sauce every single time – but it all gets a lot more complicated.

Cacio e pepe is made by cooking pasta and using the resulting starchy water to create a sauce with grated cheese and pepper.

Now researchers recommend that the perfect recipe for two involves dissolving 5g of powdered starch in 50g of water rather than using the reserved pasta water – as traditional recipes do. Then, heat the mixture gently until it thickens and turns clear.

Next, add 100g of water to cool the mixture, before blending it with 200g of cheese and adding toasted black pepper.

The resulting sauce should then be mixed with 300g of pasta that has been cooked in slightly salted water until it is al dente, drained and allowed to cool slightly.

This step helps prevent the excessive heat from destabilising the sauce. Finally, they say a little reserved starchy water can be used to adjust the consistency as needed.

“A true Italian grandmother or a skilled home chef from Rome would never need a scientific recipe for cacio e pepe, relying instead on instinct and years of experience,” the researchers write. “For everyone else, this guide offers a practical way to master the dish.”

Dr Ivan Di Terlizzi, one of the co-authors of the research, said the team consumed about 6kg of cheese for the study, with “most of it eaten with bread”.

“Although we are still not tired of this delicious dish, one of the authors had blood tests showing very high cholesterol levels,” he added. “It’s the price of science!”

“When heated, cheese proteins change their configuration and, therefore, aggregate,” said Dr Daniel Busiello, another co-author of the study from Max Planck Institute for the Physics of Complex Systems in Germany. Starch, he said, mitigates this effect by binding to the cheese proteins, reducing their direct interactions and hence their formation of clumps.

To explore the secret to a smooth and creamy sauce, researchers carried out a number of experiments using a fixed cheese-to-water ratio, but with varying concentrations of starch. The latter was controlled by dissolving known quantities of dry corn starch in the water.

The results revealed fewer clumps occurred at lower temperatures, regardless of starch concentration, with the team adding that the proteins did not start to clump below 65C. As temperatures increased, higher concentrations of starch were needed to avoid clumps forming and prevent the “mozzarella phase” – where huge wads of cheese appear.

“At higher starch concentrations, temperature becomes less of a concern, as the sauce remains smooth even with less precise heat control,” said Busiello.

Busiello added pasta water alone contains too little starch to reliably prevent clumping, only producing a smooth sauce with careful temperature control.

“Our recommended scientific approach uses a starch to cheese ratio between 2% and 3% by weight, allowing home cooks to reliably create a smooth sauce without worrying too much about temperature,” he said.