Green banana fibres could give noodles nutrient boost

Resistant starch from the green fruits of plantain and banana may boost the fibre content of foods such as instant noodles, suggests new research.

Noodles formulated with durum wheat flour and isolated plantain starch contained resistant starch levels double that obtained in standard noodles, report researcher from Mexico and Venezuela in the journal Cereal Chemistry.

"Noodles containing the plantain starch exhibited a limited digestibility due to their relatively high resistant starch content and a moderate in vitro predicted glycemic index," wrote lead author Perla Osorio-Diaz from Centro de Desarrollo de Productos Bioticos del IPN.

"They may represent a dietary option for sectors of the population with particular caloric and glycemic requirements such as diabetic patients and overweight individuals."

Starches can be divided into three groups: rapidly digestible starch (RDS, digested within 20 minutes), slowly digestible starch (SDS, digested between 20 and 120 minutes), and resistant starch (RS). The latter is not digested but is fermented in the large intestine and has 'prebiotic' properties.

Resistant starch can be found naturally in cold cooked potatoes, pasta and rice as well as baked beans and lentils.

Noodle formulation

The researchers tested plantain because the RS content is reported to be around 50 per cent, which was attributed to the "granular structure" of the starch.

Noodles were prepared using different durum wheat flour and plantain starch ratios of 90:10, 80:20, and 70:30, and compared to control noodles prepared using 100 per cent durum wheat flour. All noodles were salted with two per cent salt.

Analysis of the cooked noodles showed that as the plantain starch level increased, the total starch (TS) decreased. In addition, the soluble fibre fraction was higher than the insoluble fraction in all the samples prepared, added Osorio-Diaz.


"These composite noodles exhibited higher indices than the control sample, a phenomenon that may also be dependent on the product physical structure. Results indicate that in spite of the increased starch digestion rate, plantain starch noodles are a better source of indigestible carbohydrates than pure wheat starch pasta," she concluded.

Nutritious and delicious?

Formulating the foods and quantifying the resistant starch content is only one step along the path towards functional foods, however. In order for consumers to accept the foods, the taste must be acceptable.

Recently, Spanish researchers reported that formulating bakery products with resistant starches does result in products with modified sensory properties (LWT - Food Science and Technology, doi: 10.1016/j.lwt.2008.01.012).

"Although resistant starch producers claim that the sensory properties of bakery products are not modified when resistant starch is used, the results obtained in this study demonstrated that some differences did appear," wrote the researchers from the Instituto de Agroquimica y Tecnologia de Alimentos (CSIC) in Valencia.

Source: Cereal Chemistry
May/June 2008, Volume 85, Number 3, Pages 339-343, doi: 10.1094/CCHEM-85-3-0339
"Composite Durum Wheat Flour/Plantain Starch White Salted Noodles: Proximal Composition, Starch Digestibility, and Indigestible Fraction Content"
Authors: Perla Osorio-Diaz, A. Aguilar-Sandoval, E. Agama-Acevedo, R. Rendon-Villalobos, J. Tovar, L.A. Bello-Pérez
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