EFFECT OF SODIUM METABISULFITE ADDITION AND BAKING TEMPERATURE ON MAILLARD REACTION IN BREAD

ABSTRACT

In this study, the effect of sodium metabisulfite (SMBS) doses (0, 25, 50, 100 mg/kg dough) and baking temperatures (200, 230 and 250C) on the physical, chemical and sensory properties of bread were researched to reduce 5‐hydroxymethyl‐2‐furfural (HMF) and acrylamide contents. HMF and acrylamide contents of bread crust were decreased significantly by increasing SMBS dose and decreasing baking temperature. The HMF (137.29 mg/kg) and acrylamide (671.44 µg/kg) contents of bread crust were decreased by 33 and 67%, respectively by addition of 100 mg/kg SMBS. The maltol content of bread crusts were significantly affected by baking temperature, and were 7.19, 10.23 and 22.69 mg/kg in breads baked at 200, 230 and 250C, respectively. No HMF, acrylamide and maltol were detected in the bread crumb. The sulfur dioxide content of the crust and crumb of control bread was 6.99 and 10.69 mg/kg, and increased by 49 and 59%, respectively at 100 mg/kg SMBS dose. All breads were evaluated as acceptable by a sensory panel.

PRACTICAL APPLICATIONS

Since Maillard reaction products such as acrylamide and 5‐hydroxymethyl‐2‐furfural (HMF) are known as toxic compounds, mitigation of these compounds is important subject for health and nutrition. There is not an efficient method to prevent the formation of acrylamide and HMF in bread crusts comparison with potato crisps. The purpose of this research is to slow down Maillard reaction by addition of sodium metabisulfite in bread‐making process. As a result of this research, acrylamide and HMF content of bread crusts decreased by 33 and 67%, respectively with acceptable sensory evaluation.     

THE LACTIC ACID FERMENTATION OF THREE DIFFERENT GRAPE LEAVES GROWN IN TURKEY

Leaves of three different cultivars of Vitis vinifera L., Ekşikara, Hesapali and Siyah pekmezlik were fermented in 10% brine and 10% brine + 1% citric acid concentration for 5 weeks. Percent dry matter, average weight, protein and dimethyl sulfide content of fresh leaves were determined. During the fermentation time, chemical properties of brine (titratable acidity, pH, salt content) were determined at certain intervals. Fresh leaves of Ekşikara had the highest amount of dry matter (31.69%), followed by Siyah pekmezlik (27.89%) and Hesapali (25.36%).The protein content of fresh leaves decreased approximately 50% as a result of the fermentation. Fermented Hesapali leaves had the highest (2,955 kcal/100 g), while Siyah pekmezlik leaves had the lowest (2,384 kcal/100 g) energy values. Ekşikara leaves in 10% brine + 1% citric acid had the lowest pH value (2.09), while Siyah pekmezlik had the highest pH value (2.57) on the fifth week of the fermentation. The highest titratable acidity was measured in Hesapali (10% brine + 1% citric acid). Hesapali leaves in both types of brine showed the highest taste scores, while Ekşikara leaves were preferred for their more acceptable odor. Siyah pekmezlik leaves are not recommended for brining as the fermented leaves of this cultivar obtained the lowest sensory scores.     

USE OF COUNTERPROPAGATION NEURAL NETWORKS TO ENHANCE THE CONCURRENT SUBSPACE OPTIMIZATION STRATEGY

The paper explores the use of artificial neural networks in a concurrent optimization strategy that derives from a decomposition based approach to design of large-scale engineering systems. These problems are characterized by complex couplings that render parametric design methods inappropriate as solution tools. Decomposition methods reduce the large dimensionality problem into a sequence of smaller, more tractable optimization problems, each with a smaller set of design variables and constraints. The decomposed subproblems are rarely decoupled completely, and design changes in one subproblem have a profound influence on changes in another subproblem. Essential components of decomposition based design methods are strategies to identify a topology for problem decomposition, and to develop coordination strategies which account for couplings among the decomposed problems. The paper examines the effectiveness of artificial neural networks as a tool to both account for the coupling, and to develop methods to coordinate the solution in the different subproblems to a converged optimal design     

CHARACTERIZATION OF POLYPHENOLOXIDASE FROM WILD PEAR (PYRUS ELAEGRIFOLIA)

Wild pear polyphenoloxidase (PePPO) was extracted and purified using a Sepharose 4B- l -tyrosine- p -amino benzoic acid affinity column. Optimum conditions for pH, temperature and heat inactivation were determined. At the optimum pH and temperature, K _M and V _max values for PePPO with catechol and pyrogallol were determined. The V _max/ K _M showed that PePPO has the greatest activity toward catechol. Optimum pH for PePPO was pH 6.0 using catechol as substrate. Optimum temperatures of PePPO for pyragallol and catechol were 65 and 35C, respectively. Enzyme activity decreased because of heat denaturation with increasing temperature. Inhibition of PePPO was investigated using p -aminobenzoic acid, ethyleneglycol, l -cysteine, l -tyrosine, sodium azide, p -aminobenzenesulfonamide, β-mercaptoethanol and dithiothreitol and catechol as substrate. Competitive-type inhibition was obtained with ethyleneglycol, l -cysteine, l -tyrosine, p -aminobenzenesulfonamide and dithiothreitol. Uncompetitive inhibition was obtained with β-mercaptoethanol, sodium azide and p -aminobenzoic acid. These results show that the most effective inhibitor for PePPO was dithiothreitol and that the type of inhibition depended on the origin of PPO.

PRACTICAL APPLICATIONS

In this present work, the properties of polyphenoloxidase in Pyrus elaegrifolia , including optimum temperature, optimum pH, substrate specificity and response to inhibitors, were studied.     

Nanoscale scanning transmission electron tomography

Electron tomography enables the study of complex three‐dimensional objects with nanometre resolution. In materials science, scanning transmission electron microscopy provides images with minimal coherent diffraction effects and with high atomic number contrast that makes them ideal for electron tomographic reconstruction. In this study, we reviewed the topic of scanning transmission electron microscopy‐based tomography and illustrated the power of the technique with a number of examples with critical dimensions at the nanoscale.     

Shelf life determination of Yayik butter fortified with spice extracts

Sage ( Salvia officinalis L.), cinnamon ( Cinnamomum zeylanicum ), rosemary ( Rosmarinus officinalis L.), clove ( Syzygium aromaticum L.), sumac ( Rhus coriaria L.), oregano ( Origanum vulgare L.), ginger ( Zingiber officinale ), caraway ( Cuminum cyminum L.) and thyme ( Thymus vulgaris L.) extracts were added at two concentrations (0.2 and 0.5%) to yayik butter. The butter samples were stored at two different temperatures, 4°C and 25°C. Product acceptability was monitored following the Weibull Hazard sensory method where the end of shelf life was the time at which 50% of panellists found the product unacceptable. Ginger, thyme and cinnamon extracts increased the shelf life of yayik butter and were comparable to the synthetic preservatives sorbic acid and BHA. The shelf life of the samples stored in the refrigerator was approximately twice as long as the samples stored at room temperature.     

Investigation of the parameters affecting the behavior of RC beams strengthened with FRP

Three-point bending tests were carried out on nineteen Reinforced Concrete (RC) beams strengthened with FRP in the form of completely wrapping. The strip width to spacing ratios, FRP type, shear span to effective depth ratios, the number of FRP layers in shear, and the effect of stirrups spacing were the parameters investigated in the experimental study. The FRP contribution to strength on beams having the same strip width to spacing ratios could be affected by the shear span to effective depth ratios and stirrups spacing. The FRP contributions to strength were less on beams with stirrups in comparison to the tested beams without stirrups. Strengthening RC beams using FRP could change the failure modes of the beams compared to the reference beam. In addition to the experimental study, a number of equations used to predict the FRP contribution to the shear strength of the strengthened RC beams were assessed by using a limited number of beams available in the literature. The effective FRP strain is predicted by using test results, and this prediction is used to calculate the FRP contribution to shear strength in ACI 440.2R (2017) equation. Based on the statistical values of the data, the proposed equation has the lowest coefficient of variation (COV) value than the other equations.