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 NaHCO 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 NaHCO 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.

<p>Tomato purees were produced from <em>De Rica </em>and<em> Roma</em> cultivars of tomato, packaged in high density polyethylene and stored at ambient temperature (32±2 ºC). The stored purees were analysed weekly for physicochemical composition, sensory attributes and microbial load until they became unwholesome. There was a significant (p&lt;0.05) falling in Titratable Acidity (TTA) within the first five and six weeks for <em>De Rica</em> and <em>Roma</em> purees respectively. TTA values dropped from 12.43 to 8.40 and 10.69-7.43 for <em>De Rica</em> and <em>Roma</em> purees respectively. Total solid (TS) of the purees decreased significantly (p&lt;0.05) from 16.2% to 9.08% for <em>De Rica</em> puree and 17.89% to 9.99% for <em>Roma</em> puree within the first four weeks of storage and became stable at the later weeks of storage. <em>Roma</em> puree had higher TS throughout the storage period. Total Insoluble Solid of the purees increased significantly from 3.07% and 4.01% for <em>De</em><em> </em><em>Rica</em> puree and 2.3% and 3.44% for <em>Roma</em> puree within the first week of storage. The values however, decreased significantly is (p&lt;0.05) at the second week of storage from 4.01% to 1.19% for <em>De Rica</em> puree and 3.44% to 1.89% for <em>Roma</em> puree. The bulk density of the samples decreased significantly (p&lt;0.05) from 1.14g/ml to 0.95 g/ml for <em>De Rica</em> puree and 1.12 g/ml to 0.95 g/ml for <em>Roma</em> puree through the storage period. There was an insignificant (p&gt;0.05) increase in total bacteria count from 140 CFU/g to 320 CFU/g for <em>De Rica</em> puree and 126 CFU/g to 280 CFU/g for <em>Roma</em> puree within the first two weeks of storage. The values increased significantly (p&lt;0.05) from 640 CFU/g to 137,000 CFU/g for <em>De Rica</em> puree and 590 CFU/g to 122,000 for <em>Roma</em> puree from the third to the tenth week of storage. There was no significant difference (p&gt;0.05) between the freshly produced <em>De Rica</em> puree, <em>Roma</em> puree and the commercial sample in appearance, colour, taste and overall acceptability before and during storage. Marked rejection of the purees was observed at the eight week of storage.</p>