Softening plant tissue

Enzymatic maceration, which is a softening of plant tissue by the use of enzymes, has some potential quality advantages over mechanical-thermal disintegration as maceration is obtained with less damage to the cell walls. The major part of the plant cells remains intact by enzymatic maceration [25], as the enzymes attack only the space between the cells, and with only rare injury to the cell membrane [26]. The intact cells protect nutritional components within the cells which minimise flavour changes and deterioration on storage [27,28]. 

The composition and structure of food have an important bearing on lycopene bioavailability. Food characteristics may affect the release of lycopene from the tomato tissue matrix. Practices such as cooking or fine grinding can increase bioavailability by physically disrupting or softening plant cell walls and by disrupting lycopene-protein complexes (Hussein and El-Tohamy, 1990). 

Pectin makes up about one-third of the cell wall dry matter of dicotyledoneous and some monocotyledoneous plants (Jarvis et. al., 1988). Much smaller proportions of these substances are found in the cell walls of grasses (Wada and Ray, 1978). Pectin contributes both to adhesion between the cells and to the mechanical strength of the cell wall, behaving in the manner of stabilized gels (Jarvis, 1984). Physical changes in the plant tissue, such as softening, are frequently accompanied by changes in the properties of the pectic substances. 

Fruit Softening. The softening of plant tissues is usually accompanied by the breakdown and solubilization of pectic materials and by catabolism of cell wall polysaccharides Q). 

B. radicicola enters the plant through the root hairs or by way of a bruise. The bacteria produced in the nodule are said to be absorbed bodily by the plant tissue. With them the nitrogen which they have fixed is also assimilated by the plant. When the nodule becomes inactive it softens and disappears. As to how the plant utilizes the nitrogen fixed by tbe bacteria there are three theories ... 

The extension of the useful storage life of plant and animal products beyond a few days at room temperature presents a series of complex biochemical, physical, microbial, and economic challenges. Respiratory enzyme systems and other enzymes ia these foods continue to function. Their reaction products can cause off-davors, darkening, and softening. Microbes contaminating the surface of plants or animals can grow ia cell exudates produced by bmises, peeling, or size reduction. Fresh plant and animal tissue can be contaminated by odors, dust, iasects, rodents, and microbes. 

From the above description it will be appreciated that the efficiency of release of nutrients from ingested plant material is dependent upon the ease with which the digestive enzymes can penetrate the cell wall to release the nutrients so that they can diffuse out of the structure to be absorbed. Thus tissue maturity, cooking, macerating, mastication and mode of tissue failure, all of which control particle size, cell wall softening or cell disruption, are key features which regulate nutrient release. 

The conversion of protopectin, the water-insoluble parent pectic substance, into soluble pectin and pectate and, further, into their cleavage products, is one of the mechanisms playing a role in the plant during its maturation, as well as in the process of infection of the plant. In the plant, protopectin has the function of an intercellular adhesive and, hence, its conversion into the soluble form results in a disruption of tissue rigidity, and in cell separation that is reflected in softening and subsequent liquefaction of the plant material. 

Marinading can also transform texture. In animal tissues, dilute acid (e.g., acetic or citric) or salt solution destroys collagen-collagen interactions and so softens the fibres. Presumably in plant material, for which this treatment is also effective, it is the pectins that are altered, since the cellulose crystallites are too tightly bonded to be affected. 

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