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Research on squashy tomatoes.

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Research on squashy tomatoes Aim: To investigate the possible reasons for fruits, such as tomatoes, becoming softer and squashier as they ripen. Research: Pectin's are extracted from the cell wall with hot water or dilute acid or calcium chelators. They are the easiest constituents to remove from the cell wall. They form gels (i.e., used in jelly making). They are also another diverse group of polysaccharides that is particularly rich in galacturonic acid (galacturonans = pectic acids). Pectic polysaccharides can be cross-linked by dihydrocinnamic or diferulic acids. Although most pectic polysaccharides are acidic, others are composed of neutral sugars including arabinans and galactans. The pectic polysaccharides serve a variety of functions including determining wall porosity, providing a charged wall surface for cell-cell adhesion (middle lamella), cell-cell recognition, pathogen recognition and other. In plant cells, Pectin is linked to cellulose to form protopectin, which has the ability to absorb large amounts of water. Cellulose gives the supporting tissues their rigidity, whilst the pectic components give the plant its flexibility. In industry and at home, Pectin is well known for its gelling, thickening and stabilizing properties. Today, it is used in such diverse applications as yoghurt, confectionery and acid milk drinks. ...read more.


To achieve this, researchers removed the gene that codes for polygalacturonase, copied it and then reinserted the copy back into the plant, but backwards (a genetic modification technique termed 'anti-sense' technology), which 'switches off' the polygalacturonase enzyme. Because the rate of softening has been slowed, the modified tomatoes can remain longer on the vine to develop their full flavour (and colour). In order to stop fruits from becoming soft and squashy, and to preserve them as long as possible, we could store the fruit at low temperature, pickling in vinegar, food irradiation. Enzymes can be inactivated by heat, which is the reason for blanching vegetables; or cold temperatures below 40 degrees F can inactivate them, which is the reason for placing vegetables under refrigeration. Bacteria also produce enzymes that break down food and allow them to obtain nutrients through their cell walls. Therefore, lowering the temperature reduces the rate of enzyme action as well as the rate at which bacteria can multiply. Refrigeration increases the time required to spoil food. As the number of bacteria increases, the amount of enzymes produced increases. Higher temperatures can cause increased enzymatic activity. ...read more.


This period of growth and development, from fertilization to development of the mature fruit, requires about 45-55 days, depending on the cultivars and the season. During the growth and development period, there are many chemical and physical changes occurring that have an impact on fruit quality and ripening behaviour after harvest. Ripening is the final stage of the maturation process when the fruit changes colour, and develops the flavour, texture and aroma that makes up what we define as optimum eating quality. The biological agent that initiates this ripening process after the fruit is mature is naturally produced ethylene - this simple plant hormone described and understood over 40years ago. While there are other factors involved in this "triggering" of the ripening process by ethylene, it is essentially a universal ripening hormone. When this internal concentration of naturally produced ethylene increases to about 0.1 - 1.0 ppm, the ripening process is irreversibly initiated. The process may be glowed, but it cannot be reversed once it is truly under way. So, here is the key point: additional and externally applied ethylene, provided prior to the time that the naturally produced internal concentration reaches the required 0.1 - 1.0 ppm level, will trigger or initiate - "promote" if you will - this natural ripening process at an earlier time. Uday Patel ...read more.

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