Galactomannans show low GI snack potential

By Nathan Gray

- Last updated on GMT

Related tags: Glycemic index

Nutritional snacks could profit from lower glycemic index values from the addition of galactomannan gums, according to a new study.

The research, published in the journal Food Chemistry​, suggests that the addition of galactomannan gums as a functional ingredient in health snacks could boost nutritional values, whilst providing snacks with GI values as low as 44.

“With an increasing demand for snacks with lower GI, it is likely that these functional ingredients will become more important to the snack food industry,” ​wrote the researchers from the Institute of Food Nutrition and Human Health, at Massey University, New Zealand.

Common additive

Galactomannans are polysaccharides made up of mannose and galactose in varying ratios, and are commonly used in foods as additives and stabilisers.

Guar gum (GG) has the highest use in foods because of its low and stable price.

However, both GG and locust bean gum (LBG) are used to reduce melting and add texture to ice cream products - with LBG also commonly used in the production of cheese and salad dressings. Fenugreek gum (FG) is a galactomannan that is extracted from fenugreek seeds, and is known for its medicinal benefits.

The ratio’s of mannose to galactose in galactomannans is different in all gums – fenugreek gum has a mannose:galactose ratio of 1:1, guar gum has a 2:1 ratio, and locust bean gum a 4:1 ratio.

The addition of galactomannan gums to a food can affect the mechanical, chemical, and structural properties of a food – and could also lower glycemic index (GI) values.

According to the researchers of the new study, there has been little previous research into how galactomannan gums behave when incorporated into a snack product.

Functional properties

The new study aimed to compare the functional characteristics of FG, GG, and LBG in pea-rice blends – testing their functional properties as part of a nutritional snack product.

The research found that the addition of the gums (GG, LBG and FG) altered the physicochemical and nutritional quality of the extruded pea-rice snack products.

The results observed good expansion and functional properties for the snack products when the three gums were added at levels of up to 20 per cent, with similar results for physical characteristics like colour and texture.

Water absorption increased with the rising levels of FG – suggesting that the higher ratio of galactose may be beneficial, and could add to a lower GI product.

The researchers found that a 15 per cent addition of gums lead to GI values of less than 55 compared to control GI values of 69. - GI values of 70+ are considered high, while 55 and below are low.

The addition of FG was found to give the lowest GI value (44), whilst LBG (50) and GG (52) were still observed to be below the GI value of 55 that is considered to denote a low GI product.

Low GI

The findings of the study demonstrate that it is possible to add galactomannan gums to a food formulation to produce foods and snacks with low GI values.

However, the researchers outline that the way in which the gums affect the microstructure of products alters digestibility – and consequently GI and nutrient quality - in complex ingredient blends “requires further investigation”​.

The study suggests that snack formulated with high starch, low fat, and galacomannan gums, could provide energy, protein, and fibre in a low glycemic index product – highlighting the potential for future development of products with FG in particular, due to its lower GI values.

“Overall, the data suggest that all three galactomannans could be incorporated … to develop nutritious … snack products with low glycaemic index,” ​stated the researchers.

“The low GI also indicates that the products are more nutrient– than energy-dense and will release the sugars gradually resulting in smooth, stable rises in blood sugar and insulin levels”

Source: Food Chemistry

Published online ahead of print, doi: 10.1016/j.foodchem.2010.08.030

“A comparative study of the effects of three galactomannans on the functionality of extruded pea–rice blends”

Authors: G. Ravindran, A. Carr, A. Hardacre

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