HEAT DAMAGE OF BAKERY PRODUCTS FROM DIFFERENT WHEAT SPECIES

Physical and organoleptic characteristics of bakery products are strongly influenced by the chemical reactions, which take place during baking, such as Maillard reaction and caramelisation. An unwelcome consequence is however the loss of lysine and other amino acids, that leads to a decrease in nutritional value. To better preserve the dietary properties of the end products and identify the critical steps of the production processes, the evolution of the heat damage indices furosine, glucosylisomaltol (GLI), hydroxymethylfurfural (HMF), as well as of sucrose, glucose, fructose, maltose, alpha- and beta-amylase activities, was assessed during the production of bread and water biscuits from refined flour of three einkorn, three bread and one durum wheat samples. Bread and water biscuit were manufactured according to the AACC Methods 10-10B and 10-52, baked at 215° C for 25 min and 205° C for 35 min, respectively. Furosine (Resmini and Pellegrino, 1991), GLI, HMF (Rufián-Henares et al., 2006) and sugars (Johansen et al., 1996) were performed by HPLC while amylase activities using Megazyme kits. During a preliminary water biscuit trial, comparing different baking times (25 to 75 min), furosine increased steadily up to 55 min and then collapsed. GLI and HMF were initially scarce but increased steadily. GLI, unlike HMF, was produced already after 25 min, thus suggesting a good sensibility to heat damage. The study of heat damage development during water biscuit and bread processing using different flours showed that furosine, GLI and HMF increased only during the baking step. The maximum levels of furosine were found in the bread crust, followed by the water biscuits and the bread crumb, as a consequence of lower Aw and higher temperatures. In all products, furosine content was significantly lower in einkorn than in bread wheat and durum wheat. GLI was detected in bread crust and water biscuits, and HMF only in bread crust: the lowest levels were always observed in einkorn products. The different behaviour of einkorn was mainly related to its moderate -amylase activity, and thus the low maltose content of its dough. The results show that einkorn bread undergoes lower heat damage and better preserves its nutritional value than analogous products from durum and bread wheat.