EFFECT OF HEAT-SHOCK DURING GRAIN FILLING ON GRAIN QUALITY OF BREAD AND DURUM WHEATS

In southern Europe the Mediterranean climate is responsible for the re markable variability in both yield and quality from year to year and a lso from location to location, but it offers also a unique opportunity for the production of high-quality wheats which are deficient in the European Economic Community. This study was conducted to determine the role of the fluctuation of temperatures during grain filling on the t heological properties of bread and durum wheats (Triticum aestivum and Triticum turgidum) as evaluated with a Chopin alveograph. During the 1991-92 season, four cultivars of bread and durum wheat were grown in several locations scattered along the Italian peninsula and the island of Sicily. In each location different temperature profiles were impos ed during grain filling by anticipating or delaying sowing date or by covering the plots with plastic tunnels. Viscoelastic properties, eval uated by the variations in W, P and L alveograph parameters were signi ficantly affected by the imposed treatments. In presence of a long per iod of temperature in the range of 30-35 degrees C a dough 'strengthen ing' effect was observed, while frequent episodes of daily maximum tem peratures above 35 degrees C led to a dough 'weakening' effect. These results observed both in durum and bread wheat confirm those firstly d etected on bread wheat in Australia in areas charcterized by a Mediter ranean-like climate. The practical relevance of these effects differs in the two species: an increase of dough strength is considered detrim ental in breadmaking quality, while it exerts a positive effect in pas tamaking quality.