Call number: LD2668 .T4 1979 P59 / Master of Science

Call number: LD2668 .T4 1979 M33 / Master of Science

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No description available.

Thesis presented in partial fulfilment of the requirements for the degree of Master of Technology (Food Technology) Department of Food Technology Faculty of Applied Sciences 2014 / The aim of this study was to evaluate the effect of transglutaminase (TG) and cyclodextrinase (CG) on the rheological characteristics of oat dough and shelf-life characteristics of oat bread with a view to developing oat bread with improved texture and shelf-life. Firstly, the effects of yeast, carboxylmethylcellulose (CMC), plain yoghurt (YG), transglutaminase (TG) and cyclodextrinase (CG) on the mixing, pasting, thermal, quantification of free amino acid groups and protein crosslinking properties of oat dough were investigated through a 25-2 fractional factorial design resolution III with yeast (1.25, 3.25%), CMC (1, 2%), YG (10.75, 33.75%), TG (0.5, 1.5%) and CG (10, 40 μl) as independent variables. Among all the ingredients, only CMC, YG, and TG exhibited significant (p < 0.05) effects on the mixing properties of oat dough while yeast and CG slightly affected it. TG addition increased water absorption (34.80 - 38.45%) and peak resistance (696.40 - 840.30 FU) but decreased the dough softening (93.20 - 67.75 FU) as its level varied from 0.5 to 1.5 g. CG did not significantly (p > 0.05) affect the mixing properties of oat dough. As its level increased from 10 - 40 μl, the water absorption (38.45 - 34.80%), energy at peak (11.45 - 3.75 Wh/kg), peak resistance (840.30 - 696.40 FU) slightly decreased while the softening of oat dough increased from 67.75 to 93.20 FU. The addition of yeast and YG showed significant (p < 0.05) impacts on the pasting properties of oat dough compared to CMC, TG and CG. The storage modulus of oat dough was slightly (p > 0.05) increased by adding TG (180.37 - 202.78 kPa) and CG (170.75 - 175.71 kPa). TG decreased the loss modulus (65.95 - 62.87 kPa) of oat dough while CG increased it from 62.01 - 64.61 kPa. The thermal properties of oat dough were slightly affected by all the ingredients. The denaturation temperature was increased by incorporation of TG (6.53 - 8.33°C) and CG (6.42 - 8.33°C) but there was a decrease of enthalpy due to addition of TG (from 0.76 to –4.05 J/g) and CG (1.11 to –4.05 J/g). Only CG decreased the number of free amino acid groups (0.94 - 0.62) confirming that it catalysed the protein crosslinking of the oat glutelin while other ingredients increased it. Secondly, as CMC, YG and TG affected the mixing, pasting and thermal properties of oat dough, oat bread was baked with carboxylmethylcellulose (CMC), yoghurt (YG) and transglutaminase (TG) following a 33 Box-Behnken design consisting of CMC (1, 2 g), YG (10.75, 33.75 g) and TG (0.5, 1.5 g) as independent variables. The physical and textural analysis of oat bread showed that CMC, YG and TG addition did affect oat bread. TG decreased the springiness (6.47 - 4.14 mm), specific volume (1.61 - 1.54 ml/g) and increased hardness (537.85 - 692.41 N) of oat bread. No significant effect was observed on the colour parameters of crust and crumb of oat bread. Despite the optimal oat bread exhibited a high desirability, its high hardness and low springiness remain some challenges associated with oat bread production. Since it was well established that TG increased hardness and decreased springiness of the optimal oat bread, improvement was needed for the production of best oat bread. Thirdly, Psyllium husks (PH) and cyclodextrinase (CG) were added in five (05) best oat bread formulations such as (1) PH + CG, (2) CG, (3) TG + CG, (4) TG + PH and (5) TG + PH + CG. The best oat bread formulation with low hardness containing PH and CG was further used for sensory and shelf-life studies. The combination of ingredients psyllium husks and cyclodextrinase significantly (p < 0.05) improved the textural properties of best oat bread. It decreased the hardness (94.88 N) and increased the springiness (10.97 mm) of the best oat bread. Fourthly, the sensory evaluation showed that the consumers highly appreciated the crumb colour and texture of the best oat bread than the ones of wheat bread. In addition, they found that there was a strong correlation in crust and crumb colour between wheat and the best oat bread. However, some differences existed between the wheat and best oat bread. The best oat bread exhibited a less preference in taste than its wheat counterpart. The best oat bread positively received an overall acceptability (4.07) as wheat bread (4.22). Fively, the shelf-life studies of the best oat bread revealed that the pH and TVC of the best oat bread were more affected by the time, temperature and the interaction of both parameters (time and temperature) than Total Titratable Acidity (TTA), yeasts and mould as the storage time passed. The best oat bread could safely be stored up to 21 days at refrigeration temperature (5°C) with a Total Viable Count (TVC) load of 105 cfu/g. Finally, using survival analysis for the shelf-life studies of the best oat bread, the mathematical model revealed that the risk of deteriorating increased with the temperature.

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Master of Science / Department of Grain Science and Industry / J.M. Faubion / The market for frozen goods is expanding and the frozen dough goods sector still has potential to expand its market. It is well known that deterioration in bread quality occurs during frozen dough/bread production. In addition, it is known that dough rheology influences bread quality. To prevent deterioration of bread quality, many additives have been used and researched. Combinations of oxidants (potassium bromate and ascorbic acid) are widely used worldwide. However, potassium bromate may be carcinogenic to humans, and it has been detected in bread after baking. Since it has been prohibited or strictly limited in many countries, many researchers have tried to find a replacement. Ascorbic acid is safe for human intake, and does not persist in bread. However, it is not as effective as potassium bromate. Possible replacements in frozen doughs include oxidant (ascorbic acid)-enzyme combinations. This study evaluated the effects of ascorbic acid-specific enzyme combinations as a replacement for the potassium bromate in frozen dough and related the effects to dough behavior (gluten network strength) as evaluated by dynamic oscillation rheometry. Bread quality was evaluated by test baking. Based on the results from fresh baking studies, potassium bromate can be replaced by an optimum level combination of ascorbic acid and hemicellulase/endo-xylanase. This combination clearly improved loaf volume, and crumb grain over both control and potassium bromate containing doughs. For frozen dough/bread production, the addition of all additives improved bread quality, but ascorbic acid and endo-xylanase containing dough resulted in higher volume, and better crumb structure than did dough containing potassium bromate. Dough rheology experiments show that rheology was affected by both the process and additives. Strain sweeps gave the information about dough stability. Both the additives and proofing improved dough stability. Dough behavior (gluten network strength) was assessed by frequency sweeps. Dough containing ascorbic acid and endoxylanase was most stable during frozen dough processing.

Call number: LD2668 .T4 1986 H864 / Master of Science / Grain Science and Industry

Doctor of Philosophy / Department of Grain Science and Industry / Hulya Dogan / Jon M. Faubion / The overall hypothesis underlying this study is that the nature and extent of bran interactions with the gluten protein matrix play a dominant role in both 'in-process' dough and final product quality of whole grain baked goods. Therefore, the purposeful manipulation of those interactions should be able to minimize adverse processing or product characteristics resulting from bran inclusion/presence. The approach we took was to study the effects of bran milled to different particle sizes on dough development during and after dough mixing using fundamental rheology combined with traditional cereal chemistry approaches and x-ray microtomography (XMT). The research outcomes were used to create a better picture of how the bran is effecting the dough development and to suggest strategies that allow for the control of that effect. Study-I focused on characterization of the chemical properties, empirical rheological properties and baking performance of flours and dough with different bran contents from different sources. The development of dough microstructure and the resulting crumb texture in the presence of different bran were studied using XMT. HRW and SW bran additions resulted in higher water absorptions (WA) irrespective of the flour type and bran source. Fine bran caused slightly higher WA followed by coarse and as is bran. Both HRW and SW bran decreased the dough stability of HRW flour, while it improved the stability of SW flour doughs. Macro and microstructure of baked products were significantly affected both bran type and addition level. HRW bran added to HRW flour resulted in 8-23% decrease in loaf volume while SW bran added at the same level caused 3-11% decrease. XMT indicated that bran decreased the total number of air cells significantly. SW flour resulted in harder crumb texture than that of HRW flour breads. Overall, SW bran had less detrimental effects on mixing and baking performance of HRW flour. Study-II focused on specific bran particle size and composition on small and large deformation behavior of strong and weak flour doughs. Small deformation behavior was characterized using frequency and temperature sweep tests, while the large deformation behavior was studied using creep–recovery and uniaxial extensional testing. The results revealed that the rheological behavior of bran-enriched doughs depend on type of base flour, bran type, bran replacement level (0, 5, 10%), and the dough development protocol. Weak flour doughs benefited from inclusion of bran as inherently low peak height and stability of these doughs improved in the presence of bran. Temperature sweeps indicated a slight decrease in Gʹ and G" until around 55-60°C. In the same temperature range, presence of bran increased the moduli of composite four compared to that of the control flours. Creep compliance parameters indicated that both bran source and bran replacement had significant effect on maximum compliance (J[subscript max]) and elastic compliance (J[subscript e]). Finally, the bran type affected uniaxial extensional properties, maximum resistance (R[subscript max]) and elasticity (E), significantly independent from the type of base flour.

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