Biomedical Engineering Reference
In-Depth Information
The behaviour of part baked loaves was studied during part baking, frozen
storage and full baking (Barcenas and Rosell
2006b
). During those processes,
moisture content and hardness of crumb were quantifi ed to determine the impact of
temperature changes. The moisture content of the part baked loaves was always
higher and the crumb hardness lower than that of the full baked bread, due to the
additional evaporation during the full baking and the higher moisture content,
respectively. In addition, moisture also decreased during frozen storage owing to a
reduction of the water retention capacity of the bread constituents induced by the ice
crystals damage. The crumb hardness of the part baked loaves was almost constant
during the period of frozen storage. After full baking, a signifi cant effect of the fro-
zen storage was observed on the crumb hardness, with a progressive increase as the
frozen storage period was extended. This effect was attributed to the damage of
the bread constituents by ice crystal formation with the subsequent breakage of the
protein network and leaching out of intracellular amylose. All those effects might
increase the interaction between the inter and intra-granular amylose and the forma-
tion of a network of amylose that increased the crumb hardness (Barcenas and
Rosell
2006b
).
Almeida and Chang (
2013
) reported the changes occurring in the dough after the
pre-baking and re-baking steps in the preparation of wheat French rolls, mainly
regarding moisture content and starch gelatinization. According to those authors,
part baking and full baking did not compromise the moisture content of the crumb.
The partial baking was not suffi cient to gelatinize completely the starch granules
located in the crumb, and gelatinization still proceeded during the full baking.
Nevertheless, amylose-lipid complexes were already present in all parts of the rolls
after the pre-baking and re-baking steps, as confi rmed thermal (calorimetry) and
structural (X-ray diffraction) analysis. After partial baking, one important operation
is the chilling of the baked product, which has been emphasized as an industrial
problem due to the water loss of part-baked bread. The water loss can be prevented
by water spraying on the part baked surface without infl uencing the chilling rate
(Monteau et al.
2004
).
9.2.2
Formulation
In the case of partially baking processes, formulations or recipes could be identical
to the conventional or direct bread making process. Nevertheless, stabilizers of the
crumb structure are advisable when part baked products are going to be subjected to
freezing and frozen storage. The presence of bread improvers (alpha-amylase, sour-
dough, hydroxypropylmethylcellulose, kappa-carrageenan) minimizes the negative
effect (increase in the retrogradation temperature range) of frozen storage (Barcenas
et al.
2003b
).
Hydrocolloids are widely used in the food industry due to their capacity to control
both the rheology and texture of aqueous systems. In bakery, hydrocolloids have been
very useful as bread improvers due to their anti-staling effect (Barcenas et al.
2004
).
