What is role of pentosans and enzymes in retardation of bread staling?

A minor component of wheat flour is a carbohydrate material referred to as pentosans. Pentosans are present in wheat flour at a level of two to three percent. However, they have been examined extensively in terms of their functionality in baking. Whereas we have seen that starch is made up of one sugar unit, glucose, the pentosans are made up of two sugar units called xylose and arabinose.

One important property of the pentosans is their ability to increase the water-binding capacity of a flour and thus the baking absorption. The next table shows the effect of the addition of pentosans on the stating rate of bread at 20°C. Pentosans increased the overall time constant for the bread, that is, they decreased the rate constant or the rate of bread firming with the effect exerted by the water-insoluble pentosans being more pronounced than that of the water-soluble pentosans.

bread

overall time

constant (days)

control 5,44 

with 1 % soluble pentosans 6,53

with 1 % insoluble pentosans 8,54

The use of higher protein flour, higher absorption and the importance of storage temperature have been discussed. What else can the baker do to retard firming in bread? By far the most important ingredients presently used to retard stating are the surface-active agents. When a surface-active agent is used in bread for softness, the entire mechanism of what occurs is unclear. It is believed that a complex is formed between the surface-active agent and the amylose or the amylopectin components of the starch. The crystallization of starch is thus reduced by the incorporation of a surfactant, but the effect of temperature on this reaction is unchanged. In other words, breads with softeners still firm faster in a refrigerator than at room temperature. The primary means, therefore, to retard firming in bread is to retard the changes occurring in the starch or what is referred to as starch retrogradation.

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Pentosans have higher water binding capacity. So it will not allow to migrate the moisture and then loss. Consequently firming of bread will not occur.

Just for your infomation.

Apart from pentosan, trehalose also works well in retarding bread staling.

pentosan and some enzymes increase water holding capacity of the flour and thus slowing down the rate of firming of the bread which is known as staling of bread, where bread becomes leathery in nature, and loose its freshness. 

I agree with Devani Bansee

pentosans fortified bread retains its freshness and sensory properties better, and the shelf life of bread depends on the amount of pentose and the interaction of the starch- pentose.

The role of water-soluble and insoluble pentosans  in increasing dough volume and stale content showed that Soluble pentosansm absorbs 4.4 times more water and insoluble pentosans 9.9 times its own weight, and dough containing insoluble pentosans shows a greater increase than dough containing soluble pentosanes.

Kinetic  studies have shown that pentosans reduce the amount of starch available for crystallization, thereby delaying bread stale due to starch retrograde in the branched region of amylopectin.