Structural effects of microalgae additives on the starch gelatinisation process

Abstract

This work presents a detailed structural characterisation of the starch gelatinisation process and the effect of the addition of three microalgae species, Nannochloropsis gaditana sp., Scenedesmus almeriensis and Spirulina, by means of an advanced approach consisting of temperature-resolved simultaneous SAXS/WAXS experiments, combined with DSC. Furthermore, regular and high amylose corn starch were utilised to evaluate the impact of the amylose content. The presence of microalgae has been seen to limit water accessibility towards the interior of starch granules, reducing granule swelling and, thus, hindering the arrangement of amylopectin helices into highly ordered crystalline structures. As a result, more heterogeneous lamellar structures, with reduced apparent crystallinity, are attained. Despite the existence of lipidic compounds in the three microalgae species, the tough cell walls in Nannochloropsis and Scenedesmus impede their release towards the aqueous medium. In contrast, the weak cell walls in Spirulina are disrupted by stirring, allowing cell components to be released. The diffused lipids form helical inclusion complexes with the amylose chains and promote the crystallisation of V-type structures. The presence of amylose-lipid complexes counteracts the limited water swelling effect and results in the formation of more crystalline and homogeneous lamellar structures. This result is relevant for the food industry due to the potential of Spirulina to affect the processability and nutritional characteristics of starch-based products.

Nano-/microstructure of extruded Spirulina/starch foams in relation to their textural properties

“…Moreover, the WAXS results suggest that the formed Vtype complexes were more thermally stable than the original A-type crystallites present in the raw corn starch, hence producing slightly more crystalline samples after the extrusion cooking process. This is in agreement with previous work which reported that a small fraction of these V-type crystallites was resistant at 110 ºC (Martínez-Sanz, et al, 2018).…”

“…Our results indicate that the formation of V-type crystallinity was clearly favoured by the presence of Spirulina. The weak cell walls from Spirulina have been seen to break down very easily, even with only mild stirring (Fabra, et al, 2017;Martínez-Sanz, et al, 2018), thereby enabling the release of the components contained within the cells, such as lipids and proteins. Furthermore, a previous study showed that the formation of V-type crystallites as the result of lipid-amylose complexation takes place when subjecting corn starch to a high-humidity thermal treatment in the presence of Spirulina (Martínez-Sanz, et al, 2018).…”

“…The weak cell walls from Spirulina have been seen to break down very easily, even with only mild stirring (Fabra, et al, 2017;Martínez-Sanz, et al, 2018), thereby enabling the release of the components contained within the cells, such as lipids and proteins. Furthermore, a previous study showed that the formation of V-type crystallites as the result of lipid-amylose complexation takes place when subjecting corn starch to a high-humidity thermal treatment in the presence of Spirulina (Martínez-Sanz, et al, 2018). Thus, it can be assumed that the shearing effect during the extrusion cooking process promoted cell wall disruption and facilitated the release of intracellular components which were able to form complexes with amylose.…”

“…The gelatinization process is initiated by the access of water towards the interior of starch granules, which swell and absorb water, followed by the disruption of the crystalline and lamellar structure and the leakage of amylose from the starch granules to form a continuous gel. In fact, it has been recently demonstrated that Spirulina microalgae interfere with the gelatinization process of starch and as a result, lipid-amylose complexes can be formed, promoting the crystallisation of V-type structures (Martínez-Sanz, Fabra, G. Gómez-Mascaraque, & López-Rubio, 2018). Thus, the incorporation of Spirulina into starch-based snack foods is not only expected to impact the nutritional value, but also to affect the structural properties of the obtained products.…”

Insight on a comprehensive profile of volatile compounds of Chlorella vulgaris extracted by two “green” methods

“…To show the potential of microalgae as food ingredient, some studies have been published on healthy food products containing microalgae such as vegetarian food gels (Batista et al., ), pasta (De Marco Rodríguez, Steffolani, Martínez, & León, ; Fradique et al., ), cookies (Batista et al., ), and bread (Kadam & Prabhasankar, ). To improve the knowledge on microalgae, studies have been performed to determine the impact of their incorporation in food products and their digestibility (Batista et al., ; Martínez‐Sanz, Gómez‐Mascaraque, & López‐Rubio, ), (De Marco Rodríguez et al., ).…”