Traditional and Emerging Feedstocks for Food and Industrial Bioproduct Manufacturing - Food and Industrial Bioproducts and Bioprocessing - page 13

food products made with white sorghum are marketed as substitutes for wheat-based
products, targeting people with celiac disease who are allergic to wheat gluten (Ciacci et al .,
2007). Traditional sorghum varieties with moderate tannin content are commonly grown
and used for food and alcoholic beverages in Africa. The agronomic advantages of traditional
varieties outweigh the reduced nutrient availability and astringency of tannin sorghum. In
some African cultures tannin sorghums are preferred because of their satiating properties. It
is believed that pigmented sorghum varieties promote the health of unborn babies and have
therapeutic affects against digestive system related diseases (Taylor et al ., 2006).
Similar to other cereal grains, sorghum is rich in starch; as such, it is suitable for use in
fermentation. A large portion of grain sorghum is used for malting in Africa. There has been
extensive research and development work on enzymes used for sorghum malting and malting
and brewing technologies (Owuama, 1999; Taylor et al ., 2006). It is estimated that about
200 000 tonnes of sorghum are malted and 3000 million liters of sorghum beer is produced
annually in Southern Africa alone (Taylor and Dewar, 2001).
Sweet sorghum is classified as sugar and syrup-types. Syrup-type sweet sorghum is rich
in glucose and used for syrup, wine, lactic acid and alcohol production (Billa et al ., 1997 ).
Sorghum syrup is made by pressing the juice off the stems with rollers and boiling it down
to the desired consistency. Residual sweet sorghum stems after juice extraction are used as
animal feed and silage. Sugar-type sweet sorghum, which mainly contains sucrose, can be
used for crystal sugar production. Grain sorghum is used to produce industrial bioproducts,
such as starch, biopolymer films and coatings. Isolation of starch from sorghum is done by
wet milling (Munck, 1995). However, pigments in tannin sorghum stain the starch, making
the final product undesirable. Bleaching and low cost abbreviated wet milling have been
used to improve sorghum starch color (Yang and Seib, 1995; Beta et al ., 2000 ). It is
anticipated that new developments in wet-milling techniques and sorghum breeding will
increase the industrial uses of sorghum starch. Utilization of grain fractions from sorghum
wet milling for production of activated carbon (Diao et al ., 2002 ) and health beneficial food
ingredients enriched in PS and PC have been explored (Singh et al ., 2003 ).
Good film-forming properties make sorghum kafirin a potential feedstock for biopolymer
production. It has been demonstrated that kafirin films plasticized with glycerol and
polyethylene glycol had similar tensile and water vapor barrier properties to the films made
from commercial maize zein plasticized in the same way (Da Silva and Taylor, 2005).
Efficacy of coating fruits with kafirin to delay ripening, reduce stem-end withering and
increase shelf-life has also been investigated (Taylor et al ., 2006 ). Kafirin coating tests with
pears were successful but similar studies carried out with litchis resulted in excessive
darkening and formation of white deposits on the fruit. Recovery of sorghum wax from
DDGS and its utilization as edible coating have also been examined (Weller et al ., 1998 ).
However, edible coating applications with sorghum wax and kafirin require further research
prior to commercialization.
1.3 OIL AND OILSEEDS
Oilseed crops are major agricultural commodities grown globally. Total world oilseed
production was about 450 million tonnes during the 2010-2011 crop year (USDA, 2011). It is
expected that oilseed production will increase to 460 million tonnes in 2011-2012. About 376
million tonnes of oilseeds were crushed for oil in 2010. Currently rapeseed, canola, soybean,
cottonseed, peanuts and sunflower seed are the most important commercial oilseeds.