الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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Abstract
Sugar beet (Beta vulgaris L.) is one of the most important sugar crop in the world. 40% of the world production of sugar manufactured from sugar beet. About 37% of local sugar production come from sugar beet roots which is considered the second crop for sugar production in Egypt.
This investigation was carried out to study the chemical, technological and invertase activity changes of sugar beet roots during storage after different chemical treatments ( Ca(OH)2 , SO2 and Na2S2O5 ) at different concentrations. As well as this investigation was carried out to study the factor affecting on dextran formation during post-harvest processing of sugar roots and effect of different chemical treatments on level of dextran in roots.
The results can be summarized as the follows :-
1- The technological characteristics of sugar beet roots were determined. These characteristics were 14.68% sucrose recovery, 3.18% sucrose loss in wastes, 84.14% juice purity and 78.47% quality.
2- Sucrose loss in wastes of sugar beet roots increased as a result of the increase in α-amino nitrogen, sodium and potassium. The best treatments which gave the lowest value of sucrose loss at the end of storage periods were 2500 ppm SO2 and 500 ppm Na2S2O5.
3- A decrease of sucrose recovery was noticed in all samples during storage periods. The roots treated by 500 ppm Na2S2O5 recorded the highest values of sucrose recovery during storage. The lowest value of sucrose recovery were recorded by the control samples and samples treated with 1% Ca(OH)2.
4- Sugar beet quality was increased in samples treated with 500 ppm Na2S2O5 at the end of storage period.
5- Similar change of relative percentage of juice purity during storage was observed. Roots treated with 500 ppm Na2S2O5 recorded the highest values of juice purity at the end of storage periods, while control sample had the least values.
6- Potassium recorded minor increase during storage after using different chemical treatments.
7- Significant differences of sodium content during storage between control sample and other treated samples were noticed. But there was no significant difference between treated samples at the end of storage.
8- An increase in α-amino nitrogen was noticed during storage period in all samples.
9- Values of sucrose percentage were decreased during storage in all samples treated by different chemical, but this decrease in all samples were less than in control. The roots treated with 500 ppm Na2S2O5 recorded the highest values of total sugar at the end of storage period.
10- The reducing sugars content of roots in all treatments were significantly increase during storage. Samples stored after treated with 500 ppm Na2S2O5 for 10 min had the lowest increase in reducing sugars. Control and samples stored after treated by 1% Ca(OH)2 had the highest increase at the end of storage period.
11- The highest value of moisture content were observed by use 500 ppm Na2S2O5 at the end of storage period.
12- The use of 500 ppm Na2S2O5 recorded the highest value of total soluble solids. Roots treated with 1% Ca(OH)2 recorded the lowest value of total soluble solids at the end of storage period.
13- Percentage of weight loss was highly increase during storage after treatments of roots with different chemical treatments. The use of 500 ppm Na2S2O5 protect the roots against weight loss. Roots treated by 1% Ca(OH)2 recorded the highest percentage of weight loss compared with other samples and control at the end of storage period.
14- The firmness values of all treated roots were increased after three days of storage periods, then gradually decreased. The concentration of 5% calcium hydroxide solution could be recommended because it is more safe and economic in the application.
15- High significant difference of invertase activity were observed between different chemical treatment and between periods of storage. The roots treated with 500 ppm Na2S2O5 recorded the lowest value of invertase activity at the end of storage period, while control samples and roots treated by 2500 ppm Na2S2O5 or 1%% Ca(OH)2 recorded the highest values of invertase activity at the end of storage period.
16- Studies of the factors affecting the extraction of non-sugar in the diffuser, showed that the temperature and pH are considered the main factors responsible for the extraction of non-sugar and also showed that the amount of non-sugar increases by rise in pH and temperature.
17- The optimum temperature for extraction is 70oC and pH 7.0 is also sufficient for extraction a minimum amount of non-sugars.
18- Dextran levels entered to the sugar factory which beet roots was not limited depending on the beet cases. Dextran levels increased considerable during industrial stages at different harvest dates. This increase ranged from 118 ppm/Brix in healthy beet roots harvested in march to 301 ppm/Brix in molasses during May.
19- The samples taken during May month recorded the highest levels of dextran at different processing stages compared with the samples taken during March and April months.
20- Increasing in dextran levels of healthy beet roots was noticed during storage in all samples. Control samples recorded the highest levels of dextran (233 ppm/Brix), while samples treated by 2500 ppm sodium benzoate or 2500 ppm sodium metabisulfite gave the lowest levels of dextran (140 and 141 ppm /Brix) at the end of storage periods.
21- The levels of dextran content of injured beet roots increased in all samples by increasing the storage periods. At the beginning of storage, control samples had 150 ppm / Brix dextran which raised to 385 ppm / Brix at the end of storage. While roots treated with 2500 ppm sodium metabisulfite or 2500 ppm sodium benzoate had 177 and 179 ppm /Brix dextran; respectively at the end of storage period.
22- The application of dextranase enzyme to reduce dextran from raw juice was more efficient and economic than adding it to thin and thick juice. More than fifty percent of dextran removal was achieved when dextranase applied at concentration of 20 U/ 100 ml raw juice and 30 min incubation. The dextran reduction was increased and reached 65% by the use of 30 U under the same conditions.
23- In thin juice, the percentage of dextran reduction reached 25%, 37% and 45% when dextranase enzyme used at 30 U/ 100 ml after 10, 20, and 30 min of incubation; respectively.
24- The percentage of dextran reduction of thick juice was less than of raw juice and thin juice at different levels of enzyme adding.
So it could be recommended the necessity of manufacturing sugar beet roots just after harvesting to reduce sugar loss during manufacturing and prevent inversion of sucrose into glucose and fructose which of invertase enzyme action. Prolonging the storage periods after harvesting led to a gradually an significant decrease in sucrose production.
If manufacturing is difficult after harvest because of un suitable environmental conditions, transportation difficulties or roots are in surplus, treatment of roots should be done by 500 ppm, 2500 ppm sodium metabisulfite or 2500 ppm sodium benzoate. This preferred to reduce the deterioration and infection with microorganisms and to control dextran levels during storage for 3 days.
Also it could recommended to add dextranase enzyme to raw juice. Because the application of dextranase enzyme to reduce dextran from raw juice was more efficient and economical than from thin and thick juice.