Agriculture Reference
In-Depth Information
glycerol in the yeast cell wall which transfers to the dough and bread during
baking operations. This approach demonstrates how an ingredient, in this case
yeast, can be manipulated to produce a material that has an effect on the quality of
the fi nished product. While glycerol in itself is not an emulsifi er, it has humectant
properties and helps to keep the product soft and moist during storage.
14.2.2 Alternative sources of natural emulsifi ers for bakery applications
Lecithin was one of the fi rst emulsifi ers to be used extensively in the baking
industry. Commercially available lecithin contains a range of components with
the phospholipid fraction being the principal active components. In breadmaking,
lecithin is thought to improve the extensibility of the gluten, which leads to better
processing and fermentation stability resulting in improved volume and uniform
crumb structure (Bueschelberger 2004). In other products such as biscuits, cake
and pastry, it helps to emulsify the fat so that it is uniformly distributed in the
batter or dough.
Although lecithin is found in the tissues of plants and animals, the highest
amounts are found in egg yolk and the seeds of oil plants such as corn, soy and
sunfl ower to name a few. Lecithins from plants are extracted from the by-products
of the vegetable oil refi ning process, resulting in a crude material that requires
further processing before it can be used in food applications. Typical modifi cations
include hydrolysis with lipases, as well as chemical modifi cations such as
hydroxylation, acetylation and hydrogenation. Such treatment would mean that
the commercial lecithin cannot be labelled as a natural material according to the
guidelines provided by the UK FSA. Lecithin is described as a generally permitted
food additive in Europe and is labelled as E322. Despite the requirement to label
lecithin as an additive, it has a more 'natural' image compared with other
chemically synthesised emulsifi ers and would be looked on more favourably on a
product label.
Another interesting source of material which may be regarded as natural is oat
lipid. Oat lipid has been reported to have emulsifi cation and antioxidant properties
(Dull and Bonner 1996). There are also claims for it to be used as a bread improver
(Erazo-Castrejon
et al.
2001). The emulsifi cation capacity of the oil is reported to
be high due to the phospholipid, galacto- and digalactodiglyceride content. Oat oil
is commercially available, produced by the extraction of naked oats with
supercritical carbon dioxide or hexane. As with the extraction of oil from plants,
the solvent used for obtaining oat oil may disqualify the material from being
classed as natural according to the UK FSA guidelines.
Recently reported work (Yadav
et al.
2009) describes the enhancing of the
emulsifi cation function of corn fi bre gum. Corn fi bre is available in great quantity
as a by-product of the wet milling of maize from which an arabinoxylan gum can
be isolated. The corn fi bre gum has been suggested as a stabiliser for oil-in-water
emulsions and studies in model systems have shown greater functionality than
with gum Arabic. The same authors also demonstrated that corn fi bre gum and
milk protein conjugates can be prepared by a dry heat Maillard reaction for two
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