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NutrInsight • Slow-release carbohydrates: Growing evidence on metabolic responses and public health interest

The reproducibility and repeatability of this method for SDS measurement have been confirmed by an inter-
laboratory trial conducted in six different laboratories (two in the UK, two in the US, and two in France) that
tested cereal products with a wide range of SDS values (1 g to 24 g/100 g) that typically occur in cereal foods. The
uncertainty for the SDS content, which was calculated by combining the repeatability and the reproducibility,
was u = 1.9 g/100 g based on triplicate analysis, meaning that a result can be expressed as the result ± u with
95% confidence. These results confirm that this method is reliable for quantifying SDS, as its uncertainty is in
the same range as that of several AOAC-approved methods [Vinoy et al., 2015].

Using the SDS method, it has been demonstrated that, in raw materials, starch digestibility varies greatly.
However, as a significant portion of starch consumed as part of the human diet comes from cereal products that
have undergone food processing, additional studies have gone on to investigate the impact of food processing
on the SDS content of foods.

1.3 Food processing dramatically impacts SDS content

Impact of food processing conditions on SDS content

The processing conditions used to manufacture cereal products vary greatly in terms of temperature, baking
time, water content, and pressure, and thus dramatically modulate starch digestibility (i.e. from slow to rapid
digestibility) [Lang, 2004].

The impact of food processing on starch fractions is illustrated in Figure 2, using the example of three different
cereal products (rotary-molded biscuits, white bread, and extruded cereals) that were manufactured from the
same wheat flour using different processing conditions. The SDS fraction represented approximately 55% to
60% of the total starch content of the dough for the three products. After the additional processing conditions
were applied, the SDS fraction decreased by different levels in the three final products. Indeed, the SDS fraction
disappeared almost entirely in the white bread and extruded cereals, while it was partially maintained in rotary-
molded biscuits with 33% of total starch as SDS [internal data].

Based on these results, it is important to further investigate how starch digestibility is influenced by food
processing.

Rotary-molded Biscuits White Bread Extruded Cereals

100% 100% 100% RS
80% RDS
RS RS SDS

RDS RDS

SDS SDS

80% 80%

60% 60% 60%

40% 40% 40%

20% 20% 20%

0% 0% 0%

Ingredients Final Ingredients Final Ingredients Final
after mixing product after mixing product after mixing product

Figure 2: Distribution of starch fractions [Slowly Digestible Starch (SDS), rapidly digestible starch (RDS), and resistant starch (RS)
as a % of total starch] in the dough and the final product for three different cereal products manufactured from the same wheat flour.
Source: Internal data

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