Their sales have jumped by 85 per cent in the past five years, but are consumers sacrificing quality for the sake of savings?
Brand name basic white sliced bread costs $3.29. The equivalent Coles Smart Buy and Woolworths Homebrand white sliced loaf is just $1. Own label peanut butter costs $2.10, while a big brand version costs $4.50.
At more than double the price, is the expensive item also nutritionally richer?More stories from Today Tonight
Both Coles and Woolies employ nutritionists and dieticians, but say their most valuable judges are consumers. Ordinary shoppers who taste-test the supermarket's own label products to see if they're fit for the shelves.
Matt Cole from Woolworths says that as well as the texture, smell and after-taste, testers in their sensory kitchen are also looking for health benefits.
"If it doesn't live up to the customer expectations we work with the supplier to do it again. We start from scratch, come back to our sensory kitchen, put it in front of customers again, and if they like it, it is on the shelf. If they don't like it, we start again," Cole said.
"Customers don't want additional salts, sugars and fats that are unnecessary in the foods they are buying."
When comparing Woolworths and Coles own brands to the branded ones that cost significantly more for lower fat, sugar, sodium and kilojoules, the results are surprising.
Nutritionist Teresa Boyce analysed the nutritional contents and says "when it comes to saturated fat, sugar and salt, there is no difference between them. White bread isn't the best bread to eat, so if you are going to choose white bread, I would definitely go for the bread that's got the highest amount of fibre."
According to Boyce "all tomato sauces are very high in salt and very high in sugar. If you're looking at tomato sauce, the first thing I'd look at is the sugar content, and unfortunately with these sauces, the brand name has the highest amount of sugar."
Low income families spend 40 per cent of their supermarket bill on budget choices - the supermarket's generics. But many shoppers still feel the stigma and admit to concealing cheapies at the bottom of the trolley, and at the back of the pantry.
But cheap can be a smart choice - for example with jam.
"The Woolworths home brand is the best of the bunch. It's got the lowest amount of sugar and the lowest amount of salt," Boyce said.
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