Effect of water activity on the mechanical properties of selected legumes and nuts

✍ Scribed by Borges, Antje; Peleg, Micha

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 499 KB
• Volume: 75
• Category: Article
• ISSN: 0022-5142
• DOI: 10.1002/(sici)1097-0010(199712)75:4<463::aid-jsfa898>3.0.co;2-y

✦ Synopsis

Two legumes (kidney beans and chickpeas) and two nut kernels (almonds and hazelnuts) were compressed intact with a Universal testing machine at various levels in the range of 0É11È0É85 at an ambient temperature a w of 22¡C. Mechanical characterisation of the four was done through four parameters ; the slope of the initial part of forceÈdisplacement curve, considered a measure of sti †ness, the failure force, considered a measure of strength, the deformation at failure, considered a measure of brittleness or deformability and the area under the forceÈdisplacement curve corresponding to 20% compression, considered a measure of toughness. Among these parameters only the latter could be determined and used e †ectively in all four seeds and along the whole water activity range. The jaggedness of the forceÈdisplacement curve was also determined in terms of its apparent fractal dimension calculated with two di †erent algorithms for veriÐcation. There was a noticeable di †erence between the mechanical behaviour of the two groups. The nut kernels, apparently because of their high oil content, had a much smoother forceÈdisplacement curve, and the e †ect of absorbed moisture on their texture was generally more moderate than on that of the legumes. But in all the four types of seeds tested, each mechanical property had its own speciÐc moisture dependency, an observation consistent with previous reports on cereal-based products.