One of world’s oldest beer styles is roaring back to life thanks to a truckload of watermelons, 500 loaves of unsold bread and a creative partnership between Coles Liquor and Melbourne-based craft beer producer Local Brewing Co.

Local Brewing Co’s limited edition Surplus Sour Watermelon Beer, launched exclusively this week at Liquorland and First Choice Liquor Market, is the first of a series of fruit sour beers made with unsold or excess fruit from Coles’ supermarket suppliers and slated to hit the shelves in the next 12 months.

Brewed exclusively for Coles Liquor, Surplus Sour Watermelon Beer is made with three tonnes of excess melons donated by long-time Coles produce supplier Rombola Family Farms. In place of brewer’s malt, Local Brewing rescued 300 kilograms of unsold Coles bread to add to the ferment.

The result is a light, gently fruity and refreshing beer with a delicate tang that typifies sour beers, one of the fastest growing craft beer styles in Australia and part of a renaissance of this easy-drinking alternative to traditional ‘bitter’ pale ales.

Sour beers are synonymous with Belgium, where traditional sour styles such as Lambic have been brewed since early in the 18th century. However, their history can be traced back as far as 4000BC, when brewing involved little more than mixing grain and water together and allowing naturally-occurring microbes to do the rest.

In addition to yeast, which converts carbohydrates from the grain into alcohol, the microbial population also included lactobacillus, which instead uses carbohydrate to create lactic acid – the same compound that gives sourdough bread its distinct flavour.

While modern brewing techniques usually avoid so-called ‘wild’ bacteria by using carefully-cultivated strains of yeast to reduce the influence of sour or acidic flavours, the craft beer revolution has reignited interest in traditional styles.

Local Brewing Co has been creating sour beers on a boutique scale for the last three years however its collaboration with Coles has significantly upscaled production. Importantly for the brewery’s founders, it has also super-charged the positive social impact of a business that was conceived as a social enterprise to help feed those in need.

Ordinarily, Local Brewing Co contributes the equivalent of one meal from the sale of every four-pack of its beer to food rescue organisation SecondBite, which works with charities across the country to help Australians in need.

However through this partnership with Coles, co-founder Nick Campbell said Local Brewing would contribute the equivalent of one meal for the sale of every can of its Watermelon Sour beer – four times the usual donation.

“Our collaboration with Coles Liquor has been incredible – it’s allowed us to brew a genuinely sustainable beer and increase our social impact,” Mr Campbell said.

“We know from the release of previous sour beers that customers embrace this genuinely unique product and it’s a great way to use food that might otherwise be wasted.

“Every time we’ve released one of these sours in the past it has been a sell out in just a few days, so we know customers love the story of transforming rescued food into an entirely new product.”

Coles Liquor Merchandise General Manager Brad Gorman said the partnership would produce at least three other exclusive fruit sour beers in the next 12 months to meet growing demand for this style of beer as well as consumer appetite for genuinely sustainable products.

“We’re already planning new exclusive sours through partnerships with seasonal fruit suppliers in the supermarket business, which will underpin the creation of an exclusive, sustainable sour beer brand that will be unique to Coles Liquor,” Mr Gorman said.

“Sour beers are a very strong and rapidly growing segment in craft beer and we know our customers love locally made products; it’s a key element of delivering on our ambition to be the local drinks specialist.”

Fernando Rombola has been supplying watermelons to Coles for the past seven years, during which time he’s seen a significant increase in consumer interest in sustainable agriculture and reducing food waste.

His company Rombola Family Farms generously donated three tonnes of excess watermelons to the Local Brewing Co, embracing the opportunity to explore an alternative, sustainable route for the fruit, which is otherwise used as compost on the farm.

“This is super important for us – sustainability is not just about the environment, it’s financial sustainability, it’s sustainability for our people and sustainability for the land, if we are not looking after our land, how are we going to be able to reap the rewards from it?

“For the first time in my life I had to do an ESG (Environmental, Social, and Governance) statement for the bank on one of our last loans, so there is a lot of interest in sustainability and it’s the right thing to do.

“If this product is successful, we’d definitely like to see this as a different stream; the more sustainable we are, the more we can grow more with less hectares, which is what we are always trying to do.”

Local Brewing Co has a long history with SecondBite, partnering with the food rescue group when it was first established to embed philanthropy into the foundations of its craft brewing business.

“We are so excited that our long running partnership with Local Brewing Co is benefitting from a collaboration with Coles, who we’ve worked with for more than a decade now to end waste and end hunger in Australia,” said SecondBite Chief Executive Officer Steve Clifford.

“The fact Local Brewing Co is able to increase its support for SecondBite through the launch of this unique sour beer is very exciting for us.

“We couldn’t be prouder that two of our partners have collaborated to create a product that closes the loop on food waste and provides an opportunity for customers to give back with every purchase.”