An environmentally-friendly cling film alternative could slow down how quickly avocados turn brown. Harvard University academics created a spray in a lab which covers the surface of the much-loved stoned fruit favoured by millennials and bourgeois cafes. Their proof-of-concept is the first time a team has managed to produce a one-step method where antimicrobial fibres can be spun and coated directly onto a fruit. The fibres are made of pullulan, a naturally-occurring sugar, and enriched with ant