Fruit softening and pectin disassembly: an overview of nanostructural pectin modifications assessed by atomic force microscopy

Aloe vera based edible coatings improve the quality of minimally processed ‘Hayward’ kiwifruit

Background The mechanical properties of parenchyma cell walls and the strength and extension of adhesion areas between adjacent cells, jointly with cell turgor, are main determinants of firmness of fleshy fruits. These traits are modified during ripening leading to fruit softening. Cell wall modifications involve the depolymerisation of matrix glycans and pectins, the solubilisation of pectins and the loss of neutral sugars from pectin side chains. These changes weaken the cell walls and increase cell separation, which in combination with a reduction in cell turgor, bring about textural changes. Atomic force microscopy (AFM) has been used to characterise the nanostructure of cell wall polysaccharides during the ripening and postharvest storage of several fruits. This technique allows the imaging of individual polymers at high magnification with minimal sample preparation. Scope and approach This paper reviews the main features of the cell wall disassembly process associated to fruit softening from a nanostructural point of view, as has been provided by AFM studies. Key findings and conclusions AFM studies show that pectin size, ramification and complexity is reduced during fruit ripening and storage, and in most cases these changes correlate with softening. Postharvest treatments that improve fruit quality have been proven to preserve pectin structure, suggesting a clear link between softening and pectin metabolism. Nanostructural characterisation of cellulose and hemicellulose during ripening has been poorly explored by AFM and the scarce results available are not conclusive. Globally, AFM could be a powerful tool to gain insights about the bases of textural fruit quality in fresh and stored fruits.

A nanostructural view of the cell wall disassembly process during fruit ripening and postharvest storage by atomic force microscopy

The self-assembled network and physiological degradation of pectins in carrot cell walls

Influence of chitosan-based coatings on the physicochemical properties and pectin nanostructure of Chinese cherry

To investigate the fundamental of firmness changes of crisp peaches, firmness and pectin contents of two peach (Prunus persica L. Batsch) cultivars (‘Cangfangzaosheng’ and ‘Songsenzaosheng’) stored at 2 °C, 8 °C and 15 °C were investigated. Sodium carbonate-soluble pectin (SSP) extracted showed the highest correlation (positive) with firmness among the three kinds of pectins (water-soluble pectin, chelate-soluble pectin and SSP). The qualitative and quantitative information about SSP nanostructures were determined by atomic force microscopy (AFM). The widths of the peach SSPs were very consistent. The SSP chain widths of both peach cultivars were similar and were composed of several basic units. Schematic models of the changes of the chain widths were proposed. The results indicate that the firmness of peach was closely related with the contents and nanostructural characteristics of SSP, which might be hydrolyzed by enzymes in fruit flesh.

Changes in firmness, pectin content and nanostructure of two crisp peach cultivars after storage

Disclosed is a method for separating soybean protein and fat by the reversed micellar extraction, which comprises the following procedures: (1) reversed micellar solution is prepared; (2)a pretreated raw material of soybean is added into the reversed micellar solution to extract protein and fat; (3) electrolyte solution is added so that the protein is transferred into the aqueous phase from the reversed micellar solution to be separated, thereby realizing back extraction of the protein, and protein aqueous solution and mixed oil are obtained; (4) the obtained protein product and the fat product are processed. The method has the following main advantages: the fat and the protein are separated at the same time in the reversed micellar extraction system, so the production process is greatly simplified, and the production cost and the investment on the fixed assets are reduced; the method has the advantages of solvent extraction; in the process of extraction, the protein is surrounded by the water environment in the reversed micellar, and the environment is close to the environment in the cells with mild condition, so the protein is not denatured and can keep the biological activity of the protein, and the purity of the product is high; and no acid and alkali wastewater is discharged without pollution.

Method for simultaneously separating soy protein and oil fat with inverse micelle abstraction technique

The invention relates to a method for extracting soybean protein by using a dodecyltrimethylammonium chloride reverse micellar solution, which is characterized by comprising the following steps: adding full-fat soybean powder or soybean meal powder to a dodecyltrimethylammonium chloride (DTAC) reverse micellar solution, extracting, and carrying out solid-liquid separation to obtain a soybean protein solution. The invention has the following major advantages: because of the use of the dodecyltrimethylammonium chloride reverse micelle, the formation time of the reverse micellar system is short, and the preparation is more convenient and faster; because the extraction of soybean protein by DTAC/n-heptane-n-hexyl alcohol reverse micellar system is assisted by ultrasound, the preparation is more convenient and faster; the extraction rate is obviously improved, and the extraction time is shortened; in the extraction process, the protein is enclosed by water environment in the reverse micelle, the water environment is similar to the intracellular environment and the conditions are wild, thereby ensuring that the protein can not be denatured easily and the bioactivity thereof can be kept; compared with other surfactants, the residual surfactant in the soybean protein, i.e. the dodecyltrimethylammonium chloride, is easy to separate, thereby achieving high product purity; and the method has the advantages of no acid and alkaline wastewater discharge and no pollution.

Method for extracting soybean protein by using dodecyltrimethylammonium chloride reverse micellar solution

Biodegradable materials of soybean protein have been considered as the potential substitution for petroleum-based plastics. It is an effective way to alleviate the shortage of resources and the environmental pollution, and ensure the sustainable development of resources and environment. The objective of this work was to characterize the material performance of soybean protein components. Two major soybean protein fractions, 7S globulin (7S-G) and 11S globulin (11S-G) were separated from defatted soybean flour, and their purities were examined by sodium dodecyl sulfate-polyacrylamide gel eletrophoresis (SDS-PAGE). This thesis mainly solved such a problem: being processed by plasticizers, how to produce the degradable material by the mixture of 7S-G and 11S-G mixed in a proper proportion and modified by succinylation, water caprolactam and glycerol. The effect of 7S-G and 11S-G on the mechanical, water resistant and light-admitting properties of the material, and the content of -S-S- bond were determined. Microstructures of the mixed materials were characterized using scanning electron microscopy (SEM). The relationship between microstructure and properties was illustrated.

Chongbin Jiang

Papers

Changes in firmness, pectin content and nanostructure of two crisp peach cultivars after storage

Method for simultaneously separating soy protein and oil fat with inverse micelle abstraction technique

Method for extracting soybean protein by using dodecyltrimethylammonium chloride reverse micellar solution

Effect of ratio of 7S and 11S globulin on the properties of the mixture for molded soybean protein materials