TY - BOOK

T1 - Volatile Compounds and Inositol Hexakisphosphate (IP6) Content in Wholemeal Wheat Bread

AU - Mohd Noor, Nor Qhairul Izzreen B

PY - 2016

Y1 - 2016

N2 - In paper I and II, the influence of different fermentation temperature (8°C, 16°C and 32°C) andyeast level (2%, 4% and 6%) on the formation of volatile compounds in wholemeal wheat breadwere investigated. The fermentation times were regulated to optimum bread height for eachtreatment. The volatile compounds were extracted with dynamic headspace extraction andanalyzed with gas chromatography-mass spectrometry. The results were evaluated usingmultivariate data analysis and ANOVA.In paper I, the crumb fermented at high temperature (32°C) had higher relative areas of theMaillard reaction products 2-furancarboxaldehyde, 2-acetylfuran, 2-methylpyrazine andphenylacetaldehyde. At low temperature (8°C and 16°C) the crumb was characterized byhaving higher relative areas of the fermentation products 3-methylbutanal, 2-methylbutanal,ethyl acetate, ethyl hexanoate, ethyl propanoate and 3-methylbutanol. Fermentation with lowyeast level (2%) resulted in bread with higher relative areas of 2- and 3-methylbutanal as wellas (E)-2-nonenal and (E,E)-2,4-decadienal as important lipid oxidation compound in bread.Contrary, fermentation of bread with 6% yeast resulted in higher relative area of the importantfermentation product 2-phenylethanol. High yeast concentration (6%) was able to reduce therelative areas of important lipid oxidation products.In paper II, 28 volatile compounds out of 58 compounds were identified and the other 30compounds were tentatively identified in the crust. Higher fermentation temperatures promotedthe formation of Maillard reaction products 3-methyl-1-butanol, pyrazine, 2-ethylpyrazine, 2-ethyl-3-methylpyrazine, 2-vinylpyrazine, 3-hydroxy-2-butanone, methional and 5-methyl-2-furancarboxaldehyde whereas at lower temperature (8°C) the formation of 2- and 3-methylbutanal was favoured. Higher levels of yeast promoted the formation of 3-methyl-1-butanol, 2-methyl-1-propanol and 3-(methylsulfanyl)-propanal, whereas hexanal was promotedin the crust fermented with lower yeast level.In paper III the degradation of inositol hexaphosphate (IP6) was evaluated in wholemeal wheatdough fermented with different strains of S. cerevisiae (L1.12 or L6.06) or P. kudriavzevii(L3.04) with extracellular phytase activity, in order to see if the degradation of IP6 in wholemealdough could be increased by fermentation with phytase-active yeasts. Samples were taken atdifferent stage of bread-making; after mixing, after fermentation and after baking. Around 60 to70% of the initial value of IP6 in the flour (1002 mg/g) was reduced after dough mixing andadditional 10 to 20% after fermentation. No further degradation of IP6 was observed in all breadafter baking. Dough added with baker's yeast had the highest IP6 degradation after mixing anddough fermented with P. kudriavzevii L3.04 or S.cerevisiae L1.12 had the highest degradationwith the same content of IP6 (100 mg/100g) after fermentation. Although S.cerevisiae L6.06 hadthe highest extracellular volumetric phytase activity (28.8 ± 0.002 mU/mL), the IP6 content afterfermentation was in the same level of baker´s yeast (207 mg/100g) suggesting that the phytaseactivity from this yeast strain might be suppressed by reaction products in the dough. Longermixing time resulted in longer reaction time for the wheat phytase, so the activity of wheatphytase in dough seems to be the primary source of phytate degradation. Additionaldegradation can be achieved by fermentation with phytase active yeast dependent on yeaststrain.In this experimental work, fermenting wholemeal wheat dough at high temperature (32°C) withhigh yeast level (6%) might produce bread with high level of important volatile compounds in thecrumb and crust which are mostly generated from fermentation process and Maillard reactionrespectively, and this bread might have the highest degradation of IP6 contributed by theactivities of wheat phytase and yeast phytase compared to other fermentation conditions use inthis study. S.cerevisiae L.1.12 might be more efficient in reducing the amount of IP6 in doughwith short fermentation time which is suitable for the baking industry.

AB - In paper I and II, the influence of different fermentation temperature (8°C, 16°C and 32°C) andyeast level (2%, 4% and 6%) on the formation of volatile compounds in wholemeal wheat breadwere investigated. The fermentation times were regulated to optimum bread height for eachtreatment. The volatile compounds were extracted with dynamic headspace extraction andanalyzed with gas chromatography-mass spectrometry. The results were evaluated usingmultivariate data analysis and ANOVA.In paper I, the crumb fermented at high temperature (32°C) had higher relative areas of theMaillard reaction products 2-furancarboxaldehyde, 2-acetylfuran, 2-methylpyrazine andphenylacetaldehyde. At low temperature (8°C and 16°C) the crumb was characterized byhaving higher relative areas of the fermentation products 3-methylbutanal, 2-methylbutanal,ethyl acetate, ethyl hexanoate, ethyl propanoate and 3-methylbutanol. Fermentation with lowyeast level (2%) resulted in bread with higher relative areas of 2- and 3-methylbutanal as wellas (E)-2-nonenal and (E,E)-2,4-decadienal as important lipid oxidation compound in bread.Contrary, fermentation of bread with 6% yeast resulted in higher relative area of the importantfermentation product 2-phenylethanol. High yeast concentration (6%) was able to reduce therelative areas of important lipid oxidation products.In paper II, 28 volatile compounds out of 58 compounds were identified and the other 30compounds were tentatively identified in the crust. Higher fermentation temperatures promotedthe formation of Maillard reaction products 3-methyl-1-butanol, pyrazine, 2-ethylpyrazine, 2-ethyl-3-methylpyrazine, 2-vinylpyrazine, 3-hydroxy-2-butanone, methional and 5-methyl-2-furancarboxaldehyde whereas at lower temperature (8°C) the formation of 2- and 3-methylbutanal was favoured. Higher levels of yeast promoted the formation of 3-methyl-1-butanol, 2-methyl-1-propanol and 3-(methylsulfanyl)-propanal, whereas hexanal was promotedin the crust fermented with lower yeast level.In paper III the degradation of inositol hexaphosphate (IP6) was evaluated in wholemeal wheatdough fermented with different strains of S. cerevisiae (L1.12 or L6.06) or P. kudriavzevii(L3.04) with extracellular phytase activity, in order to see if the degradation of IP6 in wholemealdough could be increased by fermentation with phytase-active yeasts. Samples were taken atdifferent stage of bread-making; after mixing, after fermentation and after baking. Around 60 to70% of the initial value of IP6 in the flour (1002 mg/g) was reduced after dough mixing andadditional 10 to 20% after fermentation. No further degradation of IP6 was observed in all breadafter baking. Dough added with baker's yeast had the highest IP6 degradation after mixing anddough fermented with P. kudriavzevii L3.04 or S.cerevisiae L1.12 had the highest degradationwith the same content of IP6 (100 mg/100g) after fermentation. Although S.cerevisiae L6.06 hadthe highest extracellular volumetric phytase activity (28.8 ± 0.002 mU/mL), the IP6 content afterfermentation was in the same level of baker´s yeast (207 mg/100g) suggesting that the phytaseactivity from this yeast strain might be suppressed by reaction products in the dough. Longermixing time resulted in longer reaction time for the wheat phytase, so the activity of wheatphytase in dough seems to be the primary source of phytate degradation. Additionaldegradation can be achieved by fermentation with phytase active yeast dependent on yeaststrain.In this experimental work, fermenting wholemeal wheat dough at high temperature (32°C) withhigh yeast level (6%) might produce bread with high level of important volatile compounds in thecrumb and crust which are mostly generated from fermentation process and Maillard reactionrespectively, and this bread might have the highest degradation of IP6 contributed by theactivities of wheat phytase and yeast phytase compared to other fermentation conditions use inthis study. S.cerevisiae L.1.12 might be more efficient in reducing the amount of IP6 in doughwith short fermentation time which is suitable for the baking industry.

UR - https://soeg.kb.dk/permalink/45KBDK_KGL/fbp0ps/alma99122711167205763

M3 - Ph.D. thesis

BT - Volatile Compounds and Inositol Hexakisphosphate (IP6) Content in Wholemeal Wheat Bread

PB - Department of Food Science, Faculty of Science, University of Copenhagen

ER -