Arendt und Zannini - 2013 - Cereal grains for the food and beverage industries

132 Cereal grains for the food and beverage industries
(Table 3.8). Phosphorus is the most important element in nutritional terms;
however, in rice bran, a major proportion (90 %) of it exists as phytin phosphorus.
Wang et al. (2011) examined phytic acid (PA) and six mineral elements,
including; Mg, Ca, Mn, Fe, Zn and Se, in rice to reveal their distribution
in the different fractions to investigate the effect of degree of milling
(DOM) on the loss of these constituents during the milling process. They
found that most of the mineral elements and PA were present in the fractions
of the outermost part (bran and outer endosperm fraction), whereas
only small amounts are accumulated in the core endosperm fraction of the
rice kernels. Generally, the mineral content in rice followed the order Mg
> Ca > Mn > Zn > Fe > Se. P, Mg, Ca, Mn and Fe are mainly located in the
outer layer of the rice kernel. In contrast, Zn and Se seem to be evenly
distributed through the rice caryopsis (Wang et«/., 2011). Milling was shown
to have a large effect on mineral element concentrations and using this
technique to adjust the flour yield allows improvement of the elemental
composition of rice flour (Wang et al., 2011). Antoine et al. (2012) analysed
the mineral composition of 25 rice brands available on the Jamaican market
in addition to a local field trial sample. Brown rice was found to contain,
on average, significantly greater concentrations of Cr, Cu, K, Mg, Mn, Na,
P and Zn, in comparison with the white rice samples. White rice does not
significantly contribute to mineral nutrition for most essential elements.
3.3.5 Phytochemicals
Phytochemicals are non-nutritive components present in a plant-based diet
that exert protective or disease-preventing effects. Rice bran contains a
significant amount of natural phytochemicals such as oryzanols, tocopherols
and tocotrienols that have been reported as the strongest antioxidants in
rice bran (Orthoefer and Eastman, 2004). Polyphenols in rice are also of
particular interest due to their multiple biological activities. These phenolic
compounds, that include ferulic acid and diferulates, anthocyanins, anthocyanidins
and polymeric proanthocyanidins (condensed tannins) (Chun et al.,
2005), have a protective effect on cell constituents against oxidative damage.
Additionally, epidemiological studies have shown that they can prevent
cancers, cardiovascular and nerve diseases (Kehrer, 1993), as well as
possessing remarkable anti-inflammatory properties (Hou et al., 2012).
However, some of these bioactive components are heat labile and are often
lost during the high heat processing treatments (Pascual et al., 2012).
3.4 Rice processing
Rice processing comprises parboiling, followed by the various stages in the
milling process. The complex processing steps are detailed in the following