Agriculture Reference
In-Depth Information
In another study hydrolysis of sugar beet shreds was conducted with the application of
the same mixture of enzymes. Although it is known that these enzymes could work
synergistically with fermenting microorganisms to convert the carbohydrate components of
sugar beet shreds into biofuels it was shown that hemicellulase was not necessary to improve
the hydrolysis for obtaining high reducing sugar yield [7]. Simultaneous saccharification and
fermentation may be one way to achieve high bioethanol yield from sugar beet shreds since
relatively low end-product concentration could be maintained leading to low end-product
inhibition.
3.2. Dietary Fiber
Dietary fiber as a class of compounds includes a mixture of plant carbohydrate polymers,
both oligosaccharides and polysaccharides, e.g., cellulose, hemicelluloses, pectic substances,
gums, resistant starch and inulin which may be associated with lignin and other non-
carbohydrate components. Each polysaccharide type is distinguished by chemical, physical,
and functional properties which generally define how they are isolated and used
technologically. Their effective utilization, however, is largely dependent on their efficient
extraction and separation, on whether the isolated polysaccharides can be used directly or
require further processing, and on whether they provide unique functionality.
Apart from the fact that it is not hydrolysed, digested and absorbed in the human small
intestine, dietary fiber achieves at least one of these functions - increases the faecal bulk,
stimulates colonic fermentation, reduces insulin responses and cholesterol levels, and even
reduce risk of some chronic disorders and some forms of cancer [55].
Dietary fiber can also impart some functional properties to foods, e.g., increase water
holding capacity, oil holding capacity, emulsification and/or gel formation. When
incorporated into food dietary fiber can modify i.e., improve its functional properties such as
water and oil holding capacity, viscosity, texture, sensory characteristics, gel forming
capacity, antioxidant capacity and shelf-life [55]. Generally, by-products derived from the
manufacturing or processing of plant based foods are sources of abundant dietary fiber. These
fiber-rich by-products can fortify foods, increase their dietary fibre content and result in
healthy products, low in calories, cholesterol and fat.
Sugar beet shreds have high both dietary fiber and soluble fiber content originating
exclusively from their cell walls. The structure and composition of the dietary fiber from
sugar beet is different of that from cereals which leads to very different physico-chemical
properties, with high hydration capacities and a high proportion of soluble dietary fiber. As
such, beet fiber can be considered as an intermediate between the insoluble dietary fibers
from cereals and the soluble dietary fibers [6].
Among dietary fiber which can be obtained from sugar beet shreds, pectic substances
seem to be the most interesting to be investigated regarding their structure, functional
properies and enzymatic conversion. It have to be poined out that sugar beet pectins differ
from pectins from other plant sources having high arabinose and relatively high rhamnose
content, notably high acetic acid content and presence of phenolic esters on their side chains
mainly with ferulic acid [6, 56, 57]
. On the other side, fractions originated from pectic
polysacharides extracted from sugar beet shreds showed
relatively small amounts of
glucomannans and xyloglucans [56]. The pectins from sugar beet do not form gels in the
