Last week I was out for breakfast with my mother. Upon a beautiful basket of pastries arriving at our table, I immediately whipped out my phone to take some snaps in the hope of just one ending up Instagram-worthy.

My mother, clearly embarrassed, leaned over and whispered to me: “Maybe we should tell them you’re a journalist and that’s why you’re taking pictures of the food.”

But it was nothing to do with me being a journalist - I’m just a millennial.

Yes, it’s now de rigeur to take photos - or Boomerangs - of your meals and post them on Instagram, despite my mother’s evident shame.

But not only are we using the photo-sharing social network to document what we’re eating, we’re using it to decide where to eat too.

A new study has revealed just how important a role Instagram plays for millennials.

According to research by Zizzi, 18-35-year-olds spend five whole days a year browsing food images on Instagram, and 30 per cent would avoid a restaurant if their Instagram presence was weak.

“All my friends check out a restaurant’s Instagram page to see what we want when we go out for a meal,” 23-year-old Londoner Georgie told The Independent.

In fact, it’s now normal to sit down in a restaurant having already decided what you’re going to order because you’ve spent a few minutes stalking on Instagram in advance.

“Knowing what a dish looks like is really important when deciding what to order,” says 24-year-old Rosie, “So I always go on Instagram first - not just the restaurant’s page either but the geotag and sometimes the hashtag too.”

And Rosie isn’t alone.

“I like to check the tagged location pictures on Instagram to see if I'll be able to take an aesthetically pleasing photo,” 21-year-old Rachel Marie explains.

“If I see a post on Facebook or Instagram or a delicious looking burger or fondue, I'll search out where it's from,” Chryssiana adds.

Many restaurants have now cottoned on to the power of Instagram too, especially if their target demographic is millennials.

One such restaurant is Ben’s Canteen, which has two branches in South London and a strong Instagram presence.

With a focus on big burgers and decadent brunches, the restaurant’s menu is highly Instagrammable. What’s more, as about 70 per cent of their customers are young women, they receive a lot of Instagram posts from their diners - and actively encourage them.

“Instagram is very important to us,” Ben’s Canteen founder Ben Walton explained to The Independent.

“It’s a good way to check whether we’re resonating with our crowd. If people are posting lots of pictures, we know we’re doing something right.

“In the old days you wanted people to say nice things about you but word of mouth has evolved. If you want people to say nice things about you now, you have to make sure your dishes look good.”

It’s not just the food though - Walton is constantly updating the design and decor of his restaurants with Instagram in mind too.

The same goes for nationwide restaurant chain, Bill’s: “We've seen Instagram play an increasingly important role in our comms strategy as both the channel itself and our Instagram profile has grown in popularity,” Head of Marketing Jack Carey told The Independent.

“As a social channel, Instagram has always been our most natural fit. Bill's is a such a visual brand; from the food to the restaurant decor and these two aspects are clearly big reasons why people come to us.

“So, we approach Instagram with the view of building a picture for the customer rather than an opportunity to drive quick sales. For us that's not what social is (or should be) about.”

And when a certain dish or food item - such as freakshakes or the cronut - becomes an Instagram sensation, it can see people queuing down the street to get into the restaurant and literally snap it up.

Walton also uses the social network to keep up with his competitors - “It makes restaurants consistently evolve, which is great for the customers.”

What’s more, running the Instagram account allows him to police what’s actually going out in his restaurants and check the dishes are being presented correctly.

He’s also very welcoming to bloggers: “I don’t understand why you wouldn’t want to embrace people who are willing to talk about you in a positive fashion,” Walton says.

And blogs are another source of inspiration for millennials when it comes to finding somewhere to eat.

“I follow lots of lifestyle and food blogs,” says Rosie, “And when one of them posts a review of a restaurant I like the look of, I always add it to my list of places I want to eat. Blogs are a great way of finding new restaurants.”

And bloggers know their own influence too.

Luxury lifestyle blogger Angie Silver from Silverspoon London says she feels a responsibility to make sure her restaurant reviews are honest: “If I thought a restaurant was truly terrible I would probably just not review it,” she explained to The Independent.

But even when it comes to blog posts, it’s the pictures that hold the most power: “I always look at recommendation lists (blogs, articles, etc) and pick the ones with the most appetising pictures,” says 25-year-old Rachel from Bath.

Sometimes Instagram isn’t the first port of call, but second, as Adele from Bristol explains: “I always look for menus online so I know the prices and also if there's a veggie option that isn't just 'salad' or something boring. Then if I like the look of it I might do further searching on Instagram or look for reviews.”

In fact, a straw poll of millennial friends reveals that checking out menus online is par for the course when deciding where to eat - both for prices and food options.

“I ALWAYS stalk menus first. I love deciding what to eat before I even go there,” 23-year-old Beth from London told The Independent, adding that she uses Google Maps to plot restaurants that she likes the look of so that when she’s trying to choose where to eat she can open the map and see what’s nearby.

And that’s not the only way millennials are using Google Maps - “If I know where I need to be area-wise, I look on Google Maps (sometimes for a specific type of food, sometimes just type in 'restaurants'), judge it by the pictures on there, and then maybe go on a restaurant's website from the Google Maps screen to make a final decision,” Londoner Jack explains.

It appears traditional newspaper and magazine restaurant reviews are losing their influence over millennials in favour of online round-ups, social networks and influencers.

But although you may associate TripAdvisor with baby-boomers, the website remains popular with those in their 20s too.