The effect of yeast concentration and fermentation temperature on the volatile composition of wheat bread crust

Bread belongs to the larges groups of foodstuffs consumed worldwide. Freshly baked bread usually posses a brownish crust with an appealing roasty flavour. The basis ingredients, used for bread making, are themselves not very aromatic. In the various steps of a bread making process, they undergo several changes resulting in the production of pleasant flavour compounds. The volatile compounds, responsible for the roasty flavours of the crust, are primarily produced during baking via the browning reactions Maillard reaction, and to a lesser extend caramelisation. Even though the baking process is the main factor determining the volatile composition of bread crust, the yeast concentration, as well as fermentation temperature and time, are also found to have an impact on the volatile composition of bread crust. The effect of yeast concentration and fermentation temperature on the volatile composition of wheat bread crust was investigated. 9 wheat breads were prepared with varying yeast concentrations (2, 4, and 6%) and fermentation temperatures (5, 15 and 35 °C). In order to standardise the volume of the breads, individual fermentation times were set for each fermentation combination. The volatile compounds were collected from crust samples by dynamic headspace and subsequently separated and identified by Gas chromatography mass spectrometry (GC-MS). The results of the present study generally showed an effect of the different fermentation conditions on the volatile composition of the crust samples. Results from principal component analysis (PCA) showed that the crust samples from the breads fermented at 5 °C combined with 2% yeast and at 35 °C with 6% yeast were the ones differentiating the most in the volatile compositions. The samples fermented at 5 °C were in general more identical in their volatile compositions than the samples fermented at 15 and 35 °C. A total of 70 volatile compounds were detected. These primarily consisted of alcohols, aldehydes, acids, k