The fishball riot is about more than the ubiquitous Hong Kong street food - it is about the deepening rift between the city's youth and the authorities.

For 10 hours from 10pm on the first day of Chinese New Year to 8am the next day, protesters battled policemen using handmade plastic shields and sharpened wooden sticks - and whatever else was to hand, including bottles and bricks.

The mostly young protesters, numbering between 400 and 500, were fighting, they said, to defend unlicensed hawkers against the authorities out to remove them.

For Hong Kongers, even with the experience of the sporadic violence that blotted the mostly peaceful months-long Occupy movement in 2014, the Chinese New Year mayhem in the rough and ready district of Mongkok came as a shock.

But the truth is that protests in Hong Kong - commonplace and usually peaceful with little disruption to daily life and business - have been increasingly punctuated by violent confrontation.

This is as younger Hong Kongers feel frustration at the intransigence of the city's government and its political masters in Beijing, in the face of their demand for greater political freedom. They also face a bleaker future than young people of generations past, with the income gap growing wider, scarcer jobs and escalating property prices.

Skirmishes in previous protests had mainly been spontaneous, including the January 2010 protests against a high-speed rail project that saw young people gaining prominence for the first time. During the Occupy movement, young people protected themselves against police batons and tear gas with umbrellas and raincoats.

This week was likely the first time protesters came prepared for a fight.

It is time the Hong Kong authorities looked deeply into where they have gone wrong in addressing the problems of youth and how they communicate with young people.