As the United Kingdom begins contacts to negotiate new trade deals as it leaves the EU in 2019, food will be one of many areas that will need to be addressed. The ongoing spat over chlorine chicken highlights how tastes and safety practices around the world can differ hugely, since what might seem normal practice in one country can seem problematic elsewhere.
In the US, it is legal to wash chicken carcasses in chlorinated water to kill germs - but this has been banned in the EU since 1997. UK Environment Secretary Michael Gove has said the UK should not allow these imports in a post-Brexit trade deal with the US, but Trade Secretary Liam Fox says the practice is perfectly safe.
Anthony Scaramucci, US president Donald Trump's new communications director, indicated that there would 100% be a trade deal between his country and the UK, although he confessed he had no idea what was happening about chlorinated chicken.
Here are five occasions when spats over food have made past trade talks tricky.
'Infested' avocados - Mexico v US (1914-97)
For more than 80 years, the US refused to import Mexican avocados on the grounds that the fruit was infested with fruit flies and other bugs. After the signing of the North American Free Trade Agreement (Nafta) in 1994, the US came under pressure to relax its ban, rather than rely on its pricier home-grown avocados.
Avocados are always used as a pawn in the trading process. Whenever the United States talks to Mexico about opening up other agricultural commodities to US growers... it always comes back to avocados, Jerome Steyhle, who chairs the California Avocado Growers Commission
In 1997 the restrictions started to be lifted, and by 2016 the US was importing 1.7 billion avocados across the border each year, according to marketing group Avocados from Mexico. But the avocado war could be reignited now that President Trump has threatened to renegotiate Nafta - which he described as the single worst trade deal ever approved [by the United States].
Beef wars - US v EU (1988-present)
One of the best known food-related trade disputes was over hormone-fed beef. The use of certain growth hormones in cattle rearing is legal in the US. But in 1988, the EU banned the use of several major growth promotion hormones, which it said posed a potential risk to human health. This was an effective ban on American beef.
A decade later, the World Trade Organization (WTO) ruled the EU's refusal to import US beef was not based on scientific evidence and violated members' obligations. But the trading bloc still wouldn't buy the meat, leading the US to retaliate by levying higher trade tariffs on some of its EU imports.
American ranchers raise some of the best beef on the planet, but restrictive EU policies continue to deny EU consumers access to US beef at affordable prices. For several years we have been asking the EU to fix an agreement that is clearly broken, despite its original promise to provide a favorable market for US beef, US Agriculture Secretary Tom Vilsack said last year.
Stockpiling food - India v US/WTO (2013-14)
Several years ago, India blocked the implementation of a 2013 global trade agreement it feared would stop it stockpiling food for the poor. India refused to back the Trade Facilitation Agreement until it was assured proposed limits to farming subsidies would not affect its US$12bn food-security program. It pays farmers over the odds for grain, some of which it sells to poorer households while the rest is set aside in case of shortages.
The WTO trade agreement simplified customs procedures and was designed to add US$1tn to the global economy, and benefit developing countries in particular, so India's defiance was strongly criticized by the global community. India agreed to lift the veto after WTO members agreed that an arrangement known as a peace clause. It was due to expire in 2017, but will now effectively continue indefinitely.
Cars for cheese - Japan v EU (2013-17)
Negotiations on a big trade deal between Japan and the EU began in 2013. Both sides wanted to slash tariffs on a huge range of goods, to boost trade, but this is a sensitive process because domestic producers tend to be wary of foreign competition.
The Japanese side was particularly keen to boost car sales in Europe, while the EU negotiators wanted to sell more dairy products. Loosening the dairy rules wasn't such a big deal for hard cheeses such as cheddar and gouda, which are not made in Japan. But Japanese dairy farmers do make softer cheeses, which proved a roadblock in the final stages of the talks, earlier this year.
After some late night haggling, the EU's Agriculture Commissioner, Phil Hogan, secured a compromise. The EU would have a yearly quota of 31,000 tons for soft cheese exports, in exchange for almost complete market access for hard cheese.
Wallonia dairy farmers - EU v Canada (2016)
After years of negotiations, the EU completed its most ambitious free-trade deal to date: the Comprehensive Economic and Trade Agreement (Ceta) with Canada. But under EU rules, some far-reaching trade agreements require the consent of all 28 EU countries before they can come into force.
To make things even more complicated, in Belgium seven federal, regional and community bodies had to give their approval as well. Wallonia, the country's French-speaking region, said no. Politicians in the staunchly socialist region had concerns about the dispute-settlement mechanism in the agreement, along with something else - milk.
Wallonian dairy farmers worried about the impact of free trade on their sales. A group of them marched outside the European Commission in Brussels to voice their disapproval of Ceta. Eventually, Belgian political leaders reached a consensus and broke the deadlock, agreeing an addendum to the Canadian deal, which addressed concerns over the rights of farmers and governments. The European Parliament approved Ceta in February, although it has not come into force yet.