Evaluatıon of Functıonal Food Ingredıents Produced By Sproutıng and Fermentatıon of Dıfferent Graıns in Terms of Thermal Processıng Contamınants

Abstract

Recently, the sprouted grains have commenced to be attracted progressively by food scientists and food market due to alleged health claims. The grains obtained as a result of the sprouting process, which takes about 2-3 days, not exceeding the grain size, are called sprouted grains. When the cereals, judged as nutritionally inadequate, are stimulated by sprouting, they become rich in various compounds that are beneficial for health. However, it is crucial to evaluate the risk of exposure to possible human carcinogenic compounds due to the increase in precursors of thermal process contaminants during sprouting.

This MSc thesis intended to investigate the functional food ingredients produced from different sprouted and fermented grains, in terms of thermal processing contaminants. The grains were determined as wheat, einkorn, barley, rye, oat, and buckwheat in this study. The grains sprouted for 36-72 h were fermented with Saccharomyces cerevisiae (SC) at 20, 30 and 40 ˚C for 1, 2 and 3 h and also fermented with sourdough (SD) at 10, 20 and 30 ˚C for 12, 24 and 36 h. In the first part, effects of sprouting and fermentation on reducing sugars and free amino acid composition in aforementioned grains was comprehensively evaluated. Additionally, formation of acrylamide and 5-Hydroxymethylfurfural (HMF) was monitored during heating at 180 °C for 5, 10 and 15 min in sprouted and fermented wholemeals. The asparagine concentration of grains decreased up to 40% after 24-36 h of sprouting, except buckwheat, and it started to increase after 48 h compared to native grains. The gradual increase of glucose concentration during sprouting resulted in higher acrylamide and HMF generation. The formation of acrylamide and HMF decreased after SC fermentation of both native and sprouted wholemeals, whereas HMF formation increased due to the pH reduction after SD fermentation.

In the second part of the study, α-dicarbonyl compounds and glycation products were measured after heating of sprouted and fermented wholemeals. Sprouting process significantly promoted the formation of Amadori product, measured as furosine, N-ε-carboxymyethyllysine (CML) and α-dicarbonyl compounds due to the increase in the concentration of reducing sugars (p<0.05). Especially the amount of 3-deoxyglucosone (3-DG) increased up to 29.6 folds compared to control. The formation of C6 α-dicarbonyl compounds after heating was greatly reduced with SC fermentation in all samples, except sprouted rye, compared to their unfermented counterparts. However, this was not observed for short chain α-dicarbonyl compounds since they were already formed during SC fermentation. Even though reducing sugars were greatly utilized by yeast during fermentation, the concentrations of furosine and CML did not decrease after heating of SC fermented wholemeals compared to the control, due to emergence of new protein bound amino groups after dough development. The accumulation of free amino acids in SD fermented wholemeals, where pH was dropped by lactic acid bacteria, prevented the increase of C6-α-dicarbonyl compounds, especially 3-DG concentrations. The amino group of amino acids reacted with the reducing sugars and α-dicarbonyl compounds, limiting the formation of α-dicarbonyl compounds expected to be formed in high amounts. Moreover, findings showed that glucose liberation from starch in SD fermented wholemeals contributed to the increase in the Amadori product formation.

In the last part, bread and biscuit production was carried out on a pilot scale using whole-wheat subjected to SC and SD fermentations after sprouting. The bread and biscuit samples were evaluated in terms of their physical properties, thermal processing contaminants content, and sensory properties. It was found that usage of sprouted wholemeal up to 50% in SC fermented toasted bread had no adverse effect on bread quality. However, the sprouted whole-wheat flour adversely changed the physical properties of SD fermented toasted bread samples, compared to the control. Finally, 50% sprouted whole wheat flour and fermented sprouted whole wheat flour in toasted bread and biscuits were not found to have a significant risk over the accumulation of acrylamide, HMF and AGEs compared to control, when substituted with native whole wheat flour.