Extraction and bleaching of dietary fiber
The methods of dietary fiber extraction can be divided into two methods (43).
The first method was alcoholic extraction which was a common method for dietary
fiber preparation from various agricultural raw materials. In 1984, Altomare et al.
(58) produced bulking agent from pineapple cores. The process included coarsely
grinding or slicing pineapple core to obtain particles or slices of 0.6 cm or less,
washing with water to remove soluble carbohydrate, extract with alcohol to remove
color and flavor constituents, removing water and alcohol, drying and finally milling
to the consistency of flour. The product from this process is especially useful as a
replacement for high-caloric ingredients and possessed high water binding capacity.
It contained 30-40% of cellulose. In 1996, Thumthanaruk (59) extracted DF from
plant sources such as pineapple core by using 95% ethanol at the ratio 1:5 of wet
weight and repeating the same extraction 3 times. This process give 93.5% purified
pineapple core DF with 36.5% settling volume and possible to apply to soup and rice
porridge. In 2007, Chaidet (60) extracted dietary fiber from carrot pomace with the
alcoholic extraction and found that it gave 7% yield of carrot fiber containing 84%
TDF with a favored water-holding capacity of 12.92 g/g sample.
Another method was alkaline extraction. The chemical reagent favored for
this extraction was hydrogen peroxide which adjusted pH to alkaline. In 1997,
Thammarutwasik (61) treated cocoa husk with 20% sodium hydroxide solution.
Delignification and bleaching were carried out twice by reslurry in an alkaline
peroxide solution containing 20% hydrogen peroxide at room temperature for 20 h.
The color of extracted DF ranged from white to yellow. The resulted fiber was added
to cookies. In 2001, Youngprawat (62) prepared dietary fiber from brewer’s dried
grain by adding sodium hydroxide to the slurry at 20% by weight of brewer’s dried
grain. After that the suspension was heated to 65-70 ºC for 1 h. Then, the fibrous
product obtained from this step was treated with 20% hydrogen peroxide. The filtered
solid fraction was brewer’s dried grain dietary fiber. In 2003, Sangnark (63) treated
sugarcrane bagasse in alkaline hydrogen peroxide condition and investigated
functional properties of DF obtained. It was found that hydrogen peroxide can
improved color value by increasing the brightness to 34%. In addition, water- and oil-
Fac. of Grad. Studies, Mahidol Univ. M.Sc.(Nutrition) / 21
holding capacity increased 2 and 1.6 times, respectively, when compared with raw
material.
Extraction and bleaching of dietary fiber The methods of dietary fiber extraction can be divided into two methods (43).The first method was alcoholic extraction which was a common method for dietaryfiber preparation from various agricultural raw materials. In 1984, Altomare et al.(58) produced bulking agent from pineapple cores. The process included coarselygrinding or slicing pineapple core to obtain particles or slices of 0.6 cm or less,washing with water to remove soluble carbohydrate, extract with alcohol to removecolor and flavor constituents, removing water and alcohol, drying and finally millingto the consistency of flour. The product from this process is especially useful as areplacement for high-caloric ingredients and possessed high water binding capacity.It contained 30-40% of cellulose. In 1996, Thumthanaruk (59) extracted DF fromplant sources such as pineapple core by using 95% ethanol at the ratio 1:5 of wetweight and repeating the same extraction 3 times. This process give 93.5% purifiedpineapple core DF with 36.5% settling volume and possible to apply to soup and riceporridge. In 2007, Chaidet (60) extracted dietary fiber from carrot pomace with thealcoholic extraction and found that it gave 7% yield of carrot fiber containing 84%TDF with a favored water-holding capacity of 12.92 g/g sample.Another method was alkaline extraction. The chemical reagent favored forthis extraction was hydrogen peroxide which adjusted pH to alkaline. In 1997,Thammarutwasik (61) treated cocoa husk with 20% sodium hydroxide solution.Delignification and bleaching were carried out twice by reslurry in an alkalineperoxide solution containing 20% hydrogen peroxide at room temperature for 20 h.The color of extracted DF ranged from white to yellow. The resulted fiber was addedto cookies. In 2001, Youngprawat (62) prepared dietary fiber from brewer’s driedgrain by adding sodium hydroxide to the slurry at 20% by weight of brewer’s driedgrain. After that the suspension was heated to 65-70 ºC for 1 h. Then, the fibrousproduct obtained from this step was treated with 20% hydrogen peroxide. The filteredsolid fraction was brewer’s dried grain dietary fiber. In 2003, Sangnark (63) treatedsugarcrane bagasse in alkaline hydrogen peroxide condition and investigatedfunctional properties of DF obtained. It was found that hydrogen peroxide canimproved color value by increasing the brightness to 34%. In addition, water- and oil-Fac. of Grad. Studies, Mahidol Univ. M.Sc.(Nutrition) / 21holding capacity increased 2 and 1.6 times, respectively, when compared with rawmaterial.
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