Interest in dietary fibre has been increasing with scientific studies linking increased intake to reduced risks of cancers such as colorectal, and cardiovascular disease. As such, there is a trend to find new sources of dietary fibre as functional ingredients, say the authors of the new study,.
Despite the mounting evidence for the benefits of dietary fibre, a survey by Columbia University showed the average intake in the US was about 12.5 grams a day, well short of the 32 grams of fiber per day recommended by the US National Fiber Council.
"Mango dietary fibre might be an alternative for development of products with balanced dietary fibre components and low glycaemic response, aimed to people with special carbohydrate/energy requirements," wrote lead author Nely Vergara-Valencia from the Centro de Desarrollo de Productos Bioticos del IPN.
According to the FAO, global production was almost 25m metric tonnes in 2000, increasing to just under 28m metric tonnes last year. Almost 99.5 per cent of production is from developing countries.
"Unripe mango fruit represents an alternative source for dietary fibre production… as well as the low cost of the fruit that may allow the preparation of dietary fibre concentrates with attractive chemical and functional characteristics," explained Vergara-Valencia.
The new research, published on-line in the journal LWT - Food Science and Technology (doi: 10.1016/j.lwt.2006.02.028), reports on the extraction of dietary fibre from unripe mangoes and its chemical composition, soluble and insoluble fibre content, the antioxidant activity and the concentration of extractable polyphenols.
The researchers found that the lipid content was 2.3 per cent, making the extract potentially suitable for use in 'light' or 'diet' products, they said. The protein content was measured to be 4.2 per cent, and total soluble carbohydrates were 32.6 per cent.
Extractable polyphenols were measured as 16.1 milligrams per gram of mango fibre. This is higher than the value from apple fibre (3 milligrams per gram), but lower than grape skins (37.6 to 52.2 mg/g). The antioxidant activity of the fibre concentrate was measured using the DPPH free-radical scavenging assay and found to be higher than fibres extracted from guava, a fruit considered suitable as an antioxidant dietary fibre.
To test the mango dietary fibre (MDF) in finished products, the scientists used the concentrated extract in the baking of cookies and bread.
"Both products formulated with MDF exhibited increased total dietary fibre levels, with a better balance of soluble and insoluble dietary fibre [compared to control bakery products]," reported Vergara-Valencia.
The soluble dietary fibre content for the MDF cookie was found to be almost six times that of the control (6.0 versus 1.3 grams per 100g). The insoluble fibre was approximately the same for the mango and control cookies.
The mango fibre bread had a soluble fibre content of 7.1 g/100g compared to 6.0 g/100g for the control bread. The insoluble fibre was significantly higher for the mango bread compared to the control bread (9.4 versus 4.3 grams per 100g).
"Bakery products added with mango dietary fibre showed higher total dietary fibre that respective controls, and the products maintained significant antioxidant capacity associated to their extractable polyphenols," concluded the researchers.
The scientists, including researchers from Venezuela and Ecuador, do not make mention of the sensory perceptions of the mango-containing bread, and whether the source of the dietary fibre has an affect on flavour or aroma.
In Europe and Japan, soluble fibre has the greater market share than insoluble. In the US, where the entire fibre market was worth $192.8m (€151.0m) in 2004, insoluble fibre dominates the market with $176.2m (€138.0m), and $16.6m (€13.0m) soluble.
But while Frost and Sullivan predicts overall growth in the US to $470m (€m) by 2011, the soluble fibre sector is expected to increase by almost twice the compound annual growth rate (CAGR) compared to insoluble fibre - 26.3 per cent compared to 13.1 per cent.