Water uptake and texture formation in tiny cereal grains during cooking: The case of fonio (Digitaria exilis)

Abstract

Understanding heat and mass transfer in cereal grains is essential for optimizing cooking, yet the underlying mechanisms remain poorly understood. This study used fonio (Digitaria exilis) as a case study to investigate water transfer, starch conversion, and texture development during soaking, steaming, and absorption cooking. Gravimetry, texture analysis, optical microscopy, and X-ray microtomography were combined to characterize hydration and structural changes. Fonio grains (equivalent diameter 0.83 ± 0.05 mm; specific surface area = 7598 ± 428 1/m; porosity 7.7 ± 2.7 %) exhibited a dense microstructure. Water uptake followed a biphasic pattern, with rapid initial water uptake within 1 min (0.11 to ∼ 0.55 kg/kg db), followed by slower diffusion-controlled hydration (∼0.70 kg/kg db after 24 h), without measurable swelling. Filling-ratio analysis suggested that part of the retained water was located outside the μCT-resolved pore volume. Repeated soaking–steaming cycles increased hydration to ∼1.50 kg/kg db and starch conversion to ∼82 %, while steaming caused little additional water uptake. Absorption cooking increased stickiness up to tenfold through solute leaching, whereas hardness depended mainly on hydration and starch conversion. Decoupling hydration from heating improves texture control while reducing steaming time in fonio processing.

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Cite

BibTeX RIS

BibTeX

@article{babadoudou2026water,
  title = {{Water uptake and texture formation in tiny cereal grains during cooking: The case of fonio (Digitaria exilis)}},
  author = {Paloma Babadoudou and Julien Petit and Fernande G. Honfo and Nadia Fanou Fogny and Waliou B. Amoussa Hounkpatin and Christian Mestres and Comlan Evariste Simon Mitchikpè and Philippe Bohuon},
  journal = {LWT - Food Science and Technology},
  year = {2026},
  month = oct,
  doi = {10.1016/j.lwt.2026.120042},
  url = {https://hal.science/hal-05802123v1},
  note = {CC BY 4.0},
}

RIS

TY  - JOUR
TI  - Water uptake and texture formation in tiny cereal grains during cooking: The case of fonio (Digitaria exilis)
AU  - Paloma Babadoudou
AU  - Julien Petit
AU  - Fernande G. Honfo
AU  - Nadia Fanou Fogny
AU  - Waliou B. Amoussa Hounkpatin
AU  - Christian Mestres
AU  - Comlan Evariste Simon Mitchikpè
AU  - Philippe Bohuon
PY  - 2026
DA  - 2026/10/15
JO  - LWT - Food Science and Technology
DO  - 10.1016/j.lwt.2026.120042
UR  - https://hal.science/hal-05802123v1
AB  - Understanding heat and mass transfer in cereal grains is essential for optimizing cooking, yet the underlying mechanisms remain poorly understood. This study used fonio (Digitaria exilis) as a case study to investigate water transfer, starch conversion, and texture development during soaking, steaming, and absorption cooking. Gravimetry, texture analysis, optical microscopy, and X-ray microtomography were combined to characterize hydration and structural changes. Fonio grains (equivalent diameter 0.83 ± 0.05 mm; specific surface area = 7598 ± 428 1/m; porosity 7.7 ± 2.7 %) exhibited a dense microstructure. Water uptake followed a biphasic pattern, with rapid initial water uptake within 1 min (0.11 to ∼ 0.55 kg/kg db), followed by slower diffusion-controlled hydration (∼0.70 kg/kg db after 24 h), without measurable swelling. Filling-ratio analysis suggested that part of the retained water was located outside the μCT-resolved pore volume. Repeated soaking–steaming cycles increased hydration to ∼1.50 kg/kg db and starch conversion to ∼82 %, while steaming caused little additional water uptake. Absorption cooking increased stickiness up to tenfold through solute leaching, whereas hardness depended mainly on hydration and starch conversion. Decoupling hydration from heating improves texture control while reducing steaming time in fonio processing.
SN  - 0023-6438
SN  - 1096-1127
ER  -

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