The body of literature on the impact of emulsion particle size on oxidation rates is unclear. This could be because emulsions are typically polydisperse and the oxidation rate of individual droplets is impossible to discern. Flow cytometry is a technique for studying individual cells and their subpopulations using fluorescence technologies. It is possible that individual emulsion droplets could also be characterized by flow cytometry as a novel approach for studying lipid oxidation. Typical emulsion droplets are too small to be visualized by flow cytometer, so emulsions were prepared to have droplets > 2 μm; weighting agent and xanthan gum were added to minimize creaming during storage. A radical-sensitive lipid-soluble fluorescence probe (BODIPY665/676) was added to the lipid used to prepare the emulsion so that the susceptibility of individual emulsion droplets could be determined. The results showed that in a polydisperse emulsion system, small droplets were oxidized faster than large droplets. Using mixtures of emulsions with and without prooxidants, it was possible to see the transfer of prooxidants between droplets, a process that is influenced by surfactant and salt concentrations. For example, surfactants micelles can transfer prooxidants to neighboring non-oxidized droplets and cause fluorescence loss when surfactant concentration was higher than critical micelle concentration (CMC). Transfer of prooxidants was promoted by adding NaCl and free fatty acid which could be attributed to the lower CMC. This study showed the potential for applying flow cytometry on oxidation of individual emulsion droplets.

<p>Low moisture baked goods (cookies, biscuits, etc.) are known for their high sugar content, low water content, and characteristic texture. The added sugar in baked goods has been a concern of health advocates due to the negative health implications of overconsumption of sugar. To minimize these health implications and support healthier food products, the replacement of sugar, sucrose, in low moisture baked goods with alternative sweeteners is of interest. The goal of this study was to improve understanding on how sweetener alternatives and dietary fiber interact with cookie ingredients and the subsequent cookie texture compared to sucrose containing cookies to aid in developing health-conscious low moisture baked goods.</p><p> The replacement of sucrose with sucrose replacers (SRs) encompassing a variety of structural and physicochemical properties (high fructose corn syrup (HFCS), amorphous sucrose, maltitol, allulose, isomalt, Benefiber, Miralax, fructooligosaccharides (FOS), and isomalto-oligosacchrides (IMO)) in wire-cut cookies was investigated in terms of starch thermal properties, model cookie formulations, and sensory descriptive analysis. Starch thermal properties were investigated using differential scanning calorimetry (DSC) while wire-cut cookie parameters were analyzed through a_w, color (<i>a, b, L</i>), moisture loss, cookie dimensions (height, width, length), and cookie hardness (N) assays. Sensory descriptive analysis was used to ascertain texture perception of wire-cut cookies through five attributes (hardness, fracturability, pastiness, cohesiveness, and crumbliness).</p> The onset gelatinization temperature (T_gel) was increased to a greater extent than sucrose by Miralax and FOS, and to the same extent by IMO, maltitol, and Benefiber at high concentrations (60%w/w). The SRs which performed similar to sucrose in wire-cut cookie baking (spread, moisture loss, hardness) and texture intensity ratings were amorphous sucrose, maltitol, and allulose. No significant differences in descriptive analysis intensity scores were found in crumbliness, cohesiveness, and pastiness between SRs and sucrose formulated wire-cut cookies. FOS, IMO, and Benefiber displayed significantly larger fracture intensity scores compared so sucrose and isomalt cookies were significantly less hard than sucrose cookies. Principal component analysis (PCA) related SRs effect on starch gelatinization, cookie baking properties, and descriptive analysis intensity scores, and indicated the mostly likely candidates for use in reduced sugar cookies are maltitol and allulose.

Charles University in Prague - Faculty of Science Department of Teaching and Didactics of Chemistry Albertov 3, 128 40 Praha 2, Czech Republic Food in Chemistry for Chemical Education Bc. Hana Strnadová hanka.str@centrum.cz This final thesis is about using food themes in teaching chemistry at secondary level education. At first there is a brief background research made on the base of several issues focused on food chemistry. Then the conception of chemistry curricula in the Czech educational system is compared with the conception in the Slovenian educational system and the posibilities of registering the questions of food into the chemistry tuition in both countries are evaluated. Approximate analysis of several contemporary Czech and Slovenian chemistry student's textbooks for secondary schools summarises representation of this subject matter. The parts of this final work are methodically processed materials to support the experimental teaching at grammar schools.

<p>  </p> <p>Edible insects, a novel source of protein, are gaining interest for their health promoting attributes. In this study, the <em>in vivo and in vitro</em> antioxidant effect of tropical banded cricket (<em>Gryllodes sigillatus</em>) peptides was evaluated. Antioxidant activity by 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical scavenging activity, oxygen radical antioxidant capacity (ORAC) and caco-2 cellular antioxidant activity, were measured in hydrolyzed followed by simulated gastrointestinal digested (SGD) cricket peptides. <em>In vivo</em> analysis was conducted using <em>Caenorhabditis elegans</em> as a model. <em>In vitro</em> analysis showed cricket peptides had greater (p< 0.05) antioxidant activity than the unhydrolyzed protein (control). In <em>C. elegans,</em> the lifespan of nematodes fed SGD peptides increased under chronic and acute oxidative stress conditions. Reactive oxygen species (ROS) levels of nematodes fed SGD peptides under paraquat induced oxidative stress were lower (p<0.05) than that of the control group. Further studies using polymerase chain reaction (PCR) indicated that the increased resistance to oxidative stress in <em>C. elegans</em> fed SGD peptides could be due to the increased expression of the stress-related gene gst-4. Taken together, these results indicate that tropical banded cricket peptides could be used as a functional food and nutraceutical to combat oxidative stress. </p>

Enzymic milk coagulation was monitored by measuring changes in curd firmness and apparent absorbance of undiluted milk. Detection of coagulation, visually or rheologically, occurred after the milk changes from a system of aggregating particles to an extended space network. This change was observed as a shoulder in apparent absorbance plots and coagulation time was defined as the critical point in the aggregation process analogously to non-linear condensation polymerization reactions. It corresponds to the inflexion point during the period when apparent absorbance was rapidly increasing and can be calculated by fitting curd firmness data to an exponential equation. Addition of calcium chloride to milk reduced coagulation time with a minimum occurring at .05M calcium. Also, curd firmness increased with a maximum at .02M calcium. It appears that calcium affects all stages of coagulation: proteolysis, micelle aggregation, and gelation. When bulk culture media was added to milk, the pH of the media had a greater effect on coagulation time than did presence of phosphate in the media. Non-specific proteolytic activity of milk coagulants affects the initial rate of curd firming but not the maximum firmness. The more proteolytic the enzyme the slower the curd firming rate. This can be used to rapidly assay for pepsin content of bovine rennets.

The effect of reducing the fat content of low-moisture part-skim Mozzarella cheese from 19% to less than 5% on melted cheese properties, i.e., apparent viscosity, cheese melt, and cook color, was investigated. Functional properties of melt and stretch and cook color were evaluated at d 1, 7, 14, and 28. A rapid microwave oven method underestimated the moisture content of the low fat cheeses by approximately 10%. Low fat cheese did not melt as well as did the low-moisture part-skim Mozzarella cheese although the moisture content of the low fat cheese (moisture content ranged from 62.5% to 63.6%) was greater than the moisture content of the part-skim control (52.1 %). Storage for 28 d only marginally increased the meltability of low fat cheese. Lower fat content increased cook color. The amount of intact a αs-CN decreased by at least 48% in all cheeses as a result of proteolysis during 28 d of storage. The relative proportion of bound, entrapped, and expressible water was determined for a reduced-fat (8% fat) and control (19% fat) Mozzarella cheese on d 1, 7, 14, and 21 of refrigerated storage. Changes in the state of water were related to changes in cheese microstructure of a commercial Mozzarella cheese and to changes in cheese meltability of the control cheese. The amount of expressible water was proportional to fat content. Throughout storage, fat/serum channels became smaller and the protein matrix expanded into the areas between fat globules. The meltability of both cheeses increased during storage. Both cheeses contained 0.71g bound water/ g protein. Expressible water decreased in both cheeses until by d 21 no water was expressible. Entrapped moisture increased from approximately 10% to 60% for the control cheese and from approximately 33% to 50% for the reduced-fat cheese. An objective test was developed for measuring stretch, a characteristic of melted cheese. Three nonfat and four low-moisture part-skim cheeses were evaluated using the new test and the results compared with conventional test methods. Two new melted cheese parameters were defined: melt strength, the maximum load (g) obtained during the test, and stretch quality, the average load (g) as the cheese fibers stretched and elongated. Melt strength correlated with apparent viscosity. Stretch quality was determined for selected nonfat and low-moisture part-skim cheeses. A three-pronged probe was used to pull cheese vertically from a melted cheese pool. Use of this elongation stretch test, along with more traditional melted cheese tests, provides more complete information about the functional properties of Mozzarella cheese.

It has been shown that iron binds strongly to the proteins in milk, and our aim was to determine whether or not this binding was affected by lowering pH in the manufacture of yogurt. Iron-protein complexing was studied using two different techniques. 1) Skim milk was fortified with 10 mg iron/100 ml and the pH of the milk was adjusted to 6.7, 6.2, 5.8, 5.3, 4.5, and 4.0. The milk was fractionated by ultracentrifugation at 52,000 x g for 60 minutes. The pellets and serum were then analyzed for iron, calcium, and phosphorus content by inductively coupled plasma spectroscopy. SOS-PAGE gels were used to determine protein profiles in the pellets and serum. 2) Yogurt was made from milk fortified with FeCl3, iron complexed with casein, and iron complexed with whey proteins. Small samples of the yogurt were then freeze-dried on carbon coated grids and examined by transmission electron microscopy at 80 KV. Affinity of iron for milk proteins was independent of pH. Iron fortification of milk did not cause loss of calcium or phosphorus from casein micelles. Electron spectroscopic imaging (ESI) showed that iron was bound to casein when yogurt was fortified with FeC13 or iron-casein complex. When fortified with iron-whey protein complex, the iron was distributed throughout the non-micellar portion of the yogurt. To determine effects of iron on yogurt quality, low-fat (2%) and nonfat iron fortified yogurt was made with three sources of iron: FeCl3, iron complexed with casein, and iron complexed with whey protein, at three levels (10, 20, 40 mg/kg). Iron content and lipid oxidation were determined over one month of storage at 4°C. Iron fortification had no effect on the rate of fermentation by the lactic cultures. There was no significant increase in oxidation levels between iron-fortified yogurt and unfortified yogurt (P > .05). No differences in the appearance, mouth feel, flavor, and overall quality ,between iron-fortified yogurt and unfortified yogurt were detected in consumer sensory analysis. Our study showed that high quality iron-fortified yogurt could be manufactured without added food safety risks.

Different fiber types were incorporated in an extruded expanded high-protein snack food. Three dietary fibers (powdered cellulose, wheat fiber, and oat fiber) were selected based on ease of extrusion, percent total dietary fiber, visible expansion, and commercial availability. A high-fiber, high-protein snack food containing whey protein, normal cornstarch, and pregelatinized waxy cornstarch was extruded using the three selected fibers. The fibers replaced the normal cornstarch at 30, 60, and 80% yielding extrudates with three fiber levels (18, 36, and 48%). Each treatment or combination of fiber type and extrudate fiber level was extruded in triplicate. A control with no fiber added was also extruded in triplicate. Extrudate characteristics were evaluated on physical (expansion ratio, air cell size, density, and breaking force) and chemical (moisture content, water absorption index, water solubility index, water and total soluble protein , and water soluble carbohydrate) parameters. The physical and chemical characteristics of the extrudates were found to be greatly affected by combined interaction of the fiber type and level of fiber in the extrudate. As the amount of fiber in the extrudate increased, moisture content increased (p < 0.0001) associated with a decrease in expansion ratio (p < 0.0001), air cell size (p < 0.0001), and water solubility index (p = 0.0013) and increased extrudate density (p < 0.0001), breaking force (p < 0.0001), and water absorption index (p < 0.0001). Dependent extrusion parameters (pressure, motor torque, barrel and die temperature of the mix, barrel and die temperatures, residence time, and product flow rate) were recorded and analyzed. All dependent extrusion parameters were influenced by the level of fiber incorporation in the extrudates (p < 0.0001). The temperature at the die was also significantly influenced by the type of fiber used, and the level of fiber and fiber type interaction (p< 0.0001). Differences were deemed statistically significant at p < 0.05. The possibility exists to incorporate dietary fiber at levels > 30% in extruded whey and cornstarch products.

Effect of added calcium ions on the relative milk clotting activities of porcine pepsin, Mucor miehei protease, Endothia parasitica protease, and Mucor pusillus protease was compared with that of rennin. Skimmilk, maintained at pH 6. 3 with 0.000% to 0.030% added calcium chloride, was used as a substrate. The coagulation activity of Mucor pusillus protease appeared to be most sensitive to calcium ions, followed by Mucor rniehei protease, porcine pepsin, rennin, and Endothia parasitica protease. The clotting activities of Mucor pusillus protease were also more sensitive than rennin to added calcium ions in milk samples maintained at pH values of 6.4, 6.5, and 6.6. Mucor pusillus protease and rennin were standardized to equal activities in skimmilk maintained at pH 6.3 and 6.6 containing 0.020% added CaCl2. For skimmilk maintained at pH 6.3, Mucor pusillus protease concentrations ix that gave the same clotting times as rennin in skimmilk containing 0.000% and 0.010% added CaCl2, were 9.6% and 4.5% higher than its standardized concentration. While at pH 6.6 Mucor pusillus protease concentrations were 13.2% and 5.8% higher.

Pasteurized skimmilk at 4°C was acidified to pH 5.8 with 85.5% phosphoric acid (136g H3Po4;100 kg skimmilk), then warmed to 54°C and ultrafiltered to a protein concentration 9.1 ± 0.2%. The retentate was heated to 76.5°C for 16 s then cooled to 2°C. Phosphoric acid (85.5%) was added at a rate of 3.41g per kg retentate. The acidified retentate was slowly warmed to 29.5 °C (3°C/5 min) when the pH was checked. The pH at this point was no lower than 5.4. Heating was continued until a temperature of 32.2°C was reached. Glucono delta lactone was added to the retentate (17.6 g/kg retentate) and left undisturbed for approximately 80 min. The curd was cut at pH 4.7 with 0.64 cm curd knives and allowed 10 min for syneresis. Permeate obtained from the same lot of milk was acidified to pH 4.8 (66 g H3Po4;100 kg permeate), then added to the curd at 32.2°C (three parts permeate to four parts retentate) and used as a cooking vehicle. The curd was cooked to 59°C in 90 min. The curd was held at 59°C for 10 min, drained and washed once with ice water. Cream dressing containing 12.5% fat and 3% salt was used at the rate of two parts curd to one part dressing. Control cottage cheese was produced by a direct acid method from the same skimmilk used to produce ultrafiltered curd. Use of ultrafiltered skimmilk retentate for cottage cheese making resulted in 2.24% more curd (corrected to 20% solids) and 2.24% more curd per kg original milk protein than the control. However, satisfactory firmness in UF curd required slightly more than 20% solids in the final product. Sensory evaluations indicated that creamed cottage cheese was not significantly different (p