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.

研究了子叶和种皮对普通豆（菜豆）变硬的相对贡献，并确定了控制蒸煮过程中豆变软的限速过程。将新鲜或老化的全豆和子叶在软化水或0.1 M NaHCO ₃溶液中浸泡和烹饪，并研究其质地演变，微观结构变化和热性能。用软化水煮熟的新鲜和陈旧的全豆的软化速率常数存在显着差异，新鲜和陈旧的子叶也是如此。老化的全豆和子叶的可比的软化速率常数表明种皮在储存过程中对硬化的作用微不足道。所有样品在0.1 M NaHCO _3中煮得更快解决方案。煮熟的组织崩解，然后进行显微镜检查，发现从细胞破裂到细胞破裂和分离的阶段过渡到完整的细胞分离，同时蒸煮时间增加，因此质地下降。因此，果胶在中间层中的逐步溶解大大促进了质地的衰变。尽管即使经过大量的烹饪时间，残留的双折射也表明淀粉具有一定的分子顺序，但量热分析显示，在细胞完全分离之前，淀粉已经完全糊化。这暗示着淀粉在蒸煮过程中在质地下降中的作用微不足道，但是由于细胞壁的限制，其在糊化后阻碍开卷成粘性凝胶会促进淀粉的回生。所以，