Novel insights into the role of the pectin-cation-phytate mechanism in ageing induced cooking texture changes of Red haricot beans through a texture-based classification and in situ cell wall associated mineral quantification.

Utilization of common beans is greatly hampered by the hard-to-cook (HTC) defect induced by ageing of the beans under adverse storage. Large bean-to-bean variations exist in a single batch of beans. Therefore, a texture-based bean classification approach was applied in this detailed study on beans with known textures, to gain in-depth insights into the role of the pectin-cation-phytate mechanism in relation to the texture changes during subsequent cooking of Red haricot fresh and aged beans. For the first time, a correlation between the texture (exhibited after cooking) of a single bean seed before ageing (fresh) and its texture after ageing was established. Furthermore, scanning electron microscopy coupled with energy dispersive spectrometry (SEM-EDS) based in situ cell wall associated mineral quantification revealed that the cell wall associated Ca concentration was significantly positively correlated with the texture of both fresh and aged cooked Red haricot bean cotyledons, with ageing resulting in a significant enrichment of Ca at the cell wall. These additional Ca cations originate from intracellular phytate hydrolysis during ageing, which was shown to affect the texture distribution of aged beans during cooking significantly. The relocation of the mineral cations from the cell interior to the cell wall occurs mainly during storage rather than subsequent soaking of the cotyledons. In addition, the pectin-cation-phytate hypothesis of HTC was further confirmed by demethylesterification of the cell wall pectin and increased pectin-Ca interactions upon ageing of the cotyledons, finally leading to HTC development of the cotyledon tissue.

Mechanical Disintegration and Particle Size Sieving of Chondrus crispus (Irish Moss) Gametophytes and Their Effect on Carrageenan and Phycoerythrin Extraction.

To better understand the migration properties of hybrid carrageenan from the seaweed tissue during carrageenan extraction, the effect of increasing the seaweed surface area by the mechanical disintegration of gametophyte Chondrus crispus chips was studied under various temperature and time extraction conditions. Dried Chondrus crispus seaweed chips were milled by a rotor beater mill and classified into eight different size fractions by sieving with varying mesh sizes from 50 to 2000 µm. During extraction at 22 °C, the red color of the filtrate increased significantly with the decreasing particle size of the fraction, correlating with the increasing phycoerythrin concentration (from 0.26 mg PE/g dry seaweed in the >2000 µm size fraction to 2.30 mg PE/g dry seaweed in the <50 µm size fraction). On the other hand, under the same extraction conditions, only a small increase in carrageenan precipitate was obtained with the decreasing size fractions (from no recovery in the >2000 µm size fraction to 2.1 ± 0.1 g/kg filtrate in the <50 µm size fraction). This yield was significantly lower than the ones from extractions at 45 °C (5.4 ± 0.1 g/kg) or at 90 °C (9.9 ± 2.1 g/kg) for the same particle size and time conditions. It could be concluded that hybrid carrageenan extraction is not surface area dependent, while phycoerythrin is. Therefore, it seems that phycoerythrin and carrageenan extraction follow different mechanisms. This creates potential for the selective extraction of each of those two compounds.

Relationship between processing history and functionality recovery after rehydration of dried cellulose-based suspensions: A critical review.

Cellulose-based suspensions have raised more and more attention due to their broad range of properties that can be used in paper industry and material science but also in medicine, nanotechnology and food science. Their final functionality is largely dependent on their processing history and notably the structural modifications that occur during drying and rehydration. The purpose of this work is to make a state-of-the-art contribution to the mechanisms involved in the process-structure-function relationships of cellulose-based hydrogels. The different assumptions that exist in the literature are reviewed taking the key role of the initial sample characteristics as well as the processing conditions into consideration. The decrease in swelling ability after drying is clearly due to an overall shrinkage of the structure of the material. At microscale, pore closure and cellulosic fibril aggregation are mentioned as the main reasons. The origins of such irreversible structural modifications take place at molecular level and is mainly explained by the establishment of a new balance of interactions between all components. Nevertheless, the respective contribution of each interaction are still under investigation.

New insights on the thermal analysis of low moisture composite foods.

Low moisture baked products were investigated with a view to characterising the effect of both formulation and humidity on their physical stability. At the end of the baking process, the samples were in the amorphous state as a result of starch gelatinization and sugar melting. Their thermal properties were analyzed with differential scanning calorimetry and their glass transitions were studied. The DSC thermograms were thoroughly studied through a Gaussian deconvolution of the first derivative of their heat flow. This approach evidenced a multiple phase behavior with different glass transitions in composite systems. They were associated with either a polymer-rich phase and/or a plasticizer (sugar)-rich phase whose behavior depended on the sample water content. This novel approach of thermal properties suggested new insights: considering the phase behavior of complex systems and thus the properties of their individual phases could contribute to a better understanding of the physical stability of the products.