Sourdough and Gluten-Free Products - Sourdough Biotechnology - page 242

mixing, a weak batter, resembling a cake dough, is obtained [ 7 ] . Because of the
impaired rheological properties of the GF batters in comparison to conventional
doughs, most of the GF products available on the market are characterised by over-
all low quality, lacking flavour and showing poor textural characteristics and mouth
feel [ 4, 8 ]. Furthermore, as GF products are mainly made from starch and are gener-
ally not forti fi ed [ 9 ], their contribution in terms of different nutrients, such as folate,
B vitamins, iron and dietary fibre, is poor [ 10, 11 ] .
Over the last decade, most of the academic research in the GF field has been
focused on the improvement of the quality of GF breads, producing breads that would
meet the expectations of the GF consumers in terms of appearance, structure and
nutritional benefits. Recent advances have been made in the incorporation of nutrient-
dense whole grains in GF bread formulations [ 12- 14 ]. In particular, increasing atten-
tion has been drawn to the utilization of pseudocereals, i.e. amaranth, buckwheat and
quinoa, for their excellent protein quality and high fibre, mineral and phytochemical
contents [ 15, 16 ]. Incorporation of pseudocereals in GF formulations was shown to
induce significant improvements in the baking quality of the GF dough and in the
nutritional benefits of the GF bread [ 12, 13, 17, 18 ] . However, these “healthy” fl ours
are not yet extensively used for the production of GF products. Additionally, incorpo-
ration of prebiotics was also shown to be a successful approach for improving the
dietary fibre content of GF breads produced from starch [ 19 ] .
The attempts aimed at the improvement of the textural properties of GF bread are
primarily affected by the absence of standardised baking tests for GF flours. For
example, a recent study has shown how the physiochemical composition, i.e. starch
content, particle size and rate of damaged starch, of oat flour can dramatically
influence its bread-making performances [ 20 ]. However, no guidelines are currently
available for the evaluation of the baking quality of GF flours.
Various additives, such as starches, hydrocolloids, non-toxic proteins, enzymes
and combinations thereof have been investigated in an attempt to improve the
poor structural and gas-holding capacity of GF batters. Because of their structure-
forming properties [ 21 ], hydrocolloids have been extensively used to imitate the
viscoelastic properties of gluten [ 22 ] . In particular, hydroxyl-propril-methyl-cellulose
(HPMC), carbossi- or methyl-cellulose (CMC, MC), locust bean and guar gum,
xhantan and pectins have been efficiently incorporated in GF bread formulations
[ 9, 14, 23, 24 , 25 ]). Overall, these investigations suggest that the obtained quality
improvements, i.e. improved gas retention, crumb texture, specific volume and
prolonged shelf life, are correlated to the amount of hydrocolloids used and the
interaction between the type of flour and type of hydrocolloid employed.
Non-toxic proteins can also be applied to promote structure formation in GF
breads. Incorporation of milk, legume and egg proteins can induce the formation of
a gluten-like matrix in the batter and, therefore, improve the volume and the crumb
texture of the final bread [ 14, 18, 26, 27 ]. As for hydrocolloids, the positive effects
of the added proteins strongly depend on the interaction between type of flour and
nature of the proteins [ 25 ]. However, the application of structuring proteins may
represent a matter of concern, as these ingredients can be potential allergens for
celiac patients [ 28 ] .