Deepening:

Technological and nutritional aspects
of durum wheat flour.

Giovanni Battista Quaglia
National research institut for food and nutrition

History

The cultivation of the durum wheat is very important for the agriculture of the Mediterranean zone, especially for the regions of the South Italy.

Although the main use of the hard wheat is still the pasta making, it is also used for the production of a vaste range of bakery products and, in a distinctive way, rolls with various and characteristic names and shapes. This use has a historic meaning because the first wheat called "farro" used in the Magna Greece toward the V century BC was replaced by the hard wheat, that is the kind of wheat cultivated at that time and still cultivated in Puglia, Sicily and in many other zones of the southern and eastern Mediterraneo.

In Puglia the bread making with hard wheat, originally a domestic work, became an handicraft work, acquiring a connotation of peculiarity and genuineness that has been appreciated by the consumer from far away regions.

Till to-day is very diffused the house-made bread making in South Italy. The wheat is kept in big jar, in the cool rooms of the house, and when it is ready for the bread making ,it is taken to the mill.

The bread of hard wheat takes different names according to the shape, the place of origin( best known is the Altamura’s bread) and the type of processing.

The commonest is still today the "Fresedde" in the provinces of Bari, "frasella" near Foggia and "frasedda, frisedda or frisa"in province of Salerno. It is a bread, that after the baking, is cut into two pieces and toasted in order to obtain a more prolonged conservation. Before eating this bread ,it has to be moistened with water or other drinks. The "pane cafone", the "rote" and the"sckuanéte" are other typical bread’s names of Bari and Foggia zones.

Technological aspects

The grinding of durum wheat is a process to obtain flour. A good grinding system has an yield of 60-64% of flour and 8-12% of middlings bran. The fine durum wheat semolina is obtained thanks to ruled rollers that make it fine (fig.1). The wholemeal durum wheat is obtained, instead, at the start of the grinding without losing anything. (fig.2) The two products have more protein and gluten than soft wheat.The samples of fine hard wheat semolina have also a greater ash content, lutein and carotenoid. These are characteristics of the durum wheat.(tab.1)

These data were confirmed by the samples analysis of the fine hard wheat semolina for bread making.(tab.2).

The protein of the "fine semolina" have the capacity to retain water, that gives a more prolonged conservation to the end product and a better yield (from 100 kg of fine hard wheat semolina are obtained, more or less 130/140 kg of bread).(tab.3-4)

To these peculiarity of fine semolina contributes also the ferulic acid content, that is twice the amount of the soft wheat flour.

The different chemical composition beetwen fine hard wheat semolina and soft wheat flour differenciates also the characteristics of their doughs.

The fine semolina is characterized, by the Chopin alveograph analysis, by an high toughness compared to elasticity. In this way the relation toughness-elasticity is far higher than the soft wheat flour, in details the relation P/L is over 1,5 and the W is around 190-200.

The new studies have underlined the different rheologic behaviour of the variety of durum wheat used in bread making.

To a greater protein content in Svevo variety corresponds a higher value of W (tab.5), the Duilio and Creso variety present a higher relation P/L, aside from the relatively low protein content.

Moreover, the fine hard wheat flours, for their characteristic climatic conditions of cultivation, present a high value of falling index. The values, over 500 seconds, are typical of the wheats cultivated in warm-dry milieu, that is index, characteristic of a low amylasic activity.

For this reason long yeast fermentations, during the bead making, are necessary, togheter with natural yeast or must be added malt or amylase; on the contrary it would obtain little developed, heavy and hard breads.

Nutritional and healthy aspects

From tab.6 we can notice the high protein and fibre content. It is very important to underline the value of mineral elements (potassium, iron, phosphor) and that of vitamins (thiamine and niacin). Distinctive importance has again the presence of the carotenoid, in particular the lutein and the beta-carotene whose unoxiding action seems to play again a preventive role in the process of cells aging and for some kind of cancer (fig 3). Particularly we have to notice (fig.4) that the bread of fine hard wheat semolina and the cookies of fine wholemeal hard wheat present a quantity of unoxidind substances higher than that of red grapes,which is considered the reference product for his unoxidind capacity.

We must stress, the same as in all the other grain, the content of complex carbohydrates (starch) for which the recommendations of the Guide for a healthy feeding of the National Institute of the Nutrition(revision 1997), establish that they give the 45% of the daily energy. The presence in the diet of this quota of complex carbohydrates gives the organism energy which lasts in time, to avoid abrupt changes of glucose in the blood.

As for the "hard wheat wholemeal" it values all that has been said about the fine semolina but we must added the presence of fibre and a better content of vitamins.(tab.6)

The fibre in the diet is advisable from the infancy. In particular, a diet rich in insoluble fibre, present in the "hard wheat wholemeal", is a good cure for the constipation and, besides, recent studies have demonstrated that a diet containing correct quantity of these substances- for the adult 30 grams a day-, is advisable to cure heart disease and cancer. The fibre offers a protection against the cancer of the colon and it is capable to reduce the LDL-cholesterol, whose elevated level represents one of the risks for the aterogenesis the same as the starch, when it replaces in the diet the fats which contain acids of animal origin. One of the first rules of the European code against the cancer is in fact: "Eat often grain full of fibre".

Finally it must be said that it contains more carotenoid than any other product from the grain grinding, because, it is concentrated in the external part of the carotenoid.

Conclusion

The high protein and unoxiding substances content gives to the "fine semolina" technological and nutritional peculiarities, compared to other flour obtained from different grain.

In particular the quantity and quality of protein give to the product a nutritional valence that togheter with the capability of the starch to cover the 45% of the daily food requirement, define the fine semolina right for a correct and well-balanced feeding. The carotenoid content and its protective role towards thesenility ,heart deseases and cancer are very important. These quality of the fine semolina are stressed in the wholemeal semolina, which is very rich in fibre, vitamin and unoxiding substances, such as carotenoid, tocopherols, flavonoids and phytates.

To sum up, considering the relation beetwen costs and benefits, the choise of these products can be fully justified. Moreover the price of raw material has became, in the last years, very competitive, compared to that of other kind of grain flours.

(*) the text was published by "Molini d’Italia", December 2000, n.12, year LI.