Effect of pre-treatment on physicochemical and structural properties, and the bioaccessibility of β-carotene in sweet potato flour

• Microwaves and steam pre-treatments were used to obtain flour from sweet potato.
• The crystalline region was damaged by the pre-treatment, especially by microwaves.
• Soluble and resistant starch fractions did not change with pre-treatments.
• The extraction of β-carotene was favored by microwave pre-treatment (2 and 4 min).
• The bioaccessibility after in vitro digestion increased with steam pre-treatment.

The aim of this research was to evaluate the effect of microwave or steam pre-treatment of raw sweet potato on physicochemical and microstructural properties, and the bioaccessibility of β-carotene in sweet potato flour. This is the first report on using the in vitro digestion model suitable for food, as proposed in a consensus paper, to assess the bioaccessibility of β-carotene in sweet potato flour. The pre-treatments produced a rearrangement of the flour matrix (starch, protein and non-starch polysaccharides), which was greater by using microwaves (M6) conducting to a greater increase in the phase transition temperatures up to 4.14 °C, while the enthalpy presented the higher reduction (4.49 J/g), both parameters in respect to the control. The resistant starch fraction was not modified, with about 3% in all samples. Microwave (M6) and all the steam pre-treatments showed the higher bioaccessibility of β-carotene. This flour can be used in the development of new products with high β-carotene content.