Mechanistic insight into softening of Canadian wonder common beans (Phaseolus vulgaris) during cooking

• Published in: Food research international 2018-04, Vol.106, p.522-531
• Main Authors: Chigwedere, Claire Maria, Olaoye, Taye Foyeke, Kyomugasho, Clare, Jamsazzadeh Kermani, Zahra, Pallares Pallares, Andrea, Van Loey, Ann M., Grauwet, Tara, Hendrickx, Marc E.
• Format: Article
• Language: English
• Subjects: Bean cotyledons; Bean seed coats; Cell separation; Pectin solubilization; Starch gelatinisation; Texture evolution
• ISSN: 0963-9969; 1873-7145
• DOI: 10.1016/j.foodres.2018.01.016

The relative contributions of cotyledons and seed coats towards hardening of common beans (Phaseolus vulgaris) were investigated and the rate-limiting process which controls bean softening during cooking was determined. Fresh or aged whole beans and cotyledons were soaked and cooked in demineralised water or 0.1 M NaHCO3 solution, and texture evolution, microstructure changes and thermal properties were studied. Fresh and aged whole beans cooked in demineralised water had significantly different softening rate constants and so did fresh and aged cotyledons. The comparable softening rate constants of aged whole beans and cotyledons indicated an insignificant role of the seed coat in hardening during storage. All samples cooked faster in 0.1 M NaHCO3 solution. Disintegration of cooked tissues followed by microscopic examination revealed a transition from cell breakage through a phase of cell breakage and separation to complete cell separation with increased cooking time wherefore texture decayed. Therefore, progressive solubilization of pectin in the middle lamella greatly promoted texture decay. While residual birefringence even after substantial cooking time suggested some molecular order of the starch, calorimetric analyses revealed complete starch gelatinisation before complete cell separation occurred. This implies an insignificant role of starch in texture decay during cooking but its hindered uncoiling into a viscous gel after gelatinisation due to the restricting cell wall could promote its retrogradation. Therefore, we suggest that the rate-determining process in bean softening relates to cell wall/middle lamella changes influencing pectin solubilization. [Display omitted] •Relative contributions of seed coats and cotyledons to HTC development were explored.•Fresh/aged whole beans and cotyledons were cooked to determine texture evolution.•The contribution of seed coats to HTC development is insignificant.•The rate-limiting process in bean softening was investigated.•Starch was gelatinised at early stages of texture decay.•The mechanism for bean softening is related to cell wall and middle lamella changes.