Search

Gluten proteins functionality during pastry production was examined by including redox agents in the ingredient bill. Addition of reducing and oxidizing agents respectively increased and decreased dough height during fermentation. The presence of large gas bubbles in the samples with oxidizing agents may have caused a ‘stacking’-effect and a more effective dough lift. During baking, the level of extractable proteins decreased to comparable values for all samples, except when potassium iodate (KIO 3 ) was used in the recipe. As a result of its use, a lower level of gliadin was incorporated into the gluten polymer and dough layers tended to ‘slide’ apart during baking, thereby causing collapse. Most likely, KIO 3 caused glutenin oxidation within each individual dough layer to such extent during the dough stage that insufficient thiol groups were available for forming dough layer interconnections during baking, after margarine melting. Furthermore, addition of redox agents impacted the product’s crumb structure.

To counteract iodine deficiency in the population in areas of environmental iodine deficiency table salt is often fortified with potassium iodide or iodate. However, most estimations of iodine contribution from the diet rely on calculations based on the added iodized salt and very limited experimental data about the stability of potassium iodate (KIO3) or iodine uptake during food processing is available. Therefore, the influence of cooking on the iodine content of potatoes, pasta, and rice having different size, varieties or composition was investigated. Commonly used cooking procedures were applied, using KIO3-enriched table salt in the cooking water. After iodine extraction with 0.5% NH3 iodine content was measured by ICP-MS. All products showed an increase in iodine content. Waxy potatoes, especially cut in small pieces, and egg pasta showed the highest iodine uptake. Based on the results, the use of KIO3-enriched salt for cooking is recommended to enhance iodine supply.

A new method is reported for sensitive determination of tartrazine in the food samples. The method is based on the catalytic effect of silver nanoparticle (AgNPs) on the oxidation reaction of tartrazine by potassium iodate in the acetate buffer medium. The reaction is followed spectrophotometrically by measuring the change in absorbance (ΔA) at 420 nm using a fixed time method (70 s). The reaction variables were optimised in order to achieve the highest sensitivity. The thirty six criterion detection limit was 0.3 ng/mL, and the relative standard deviation for ten replicate measurements of 30 ng/mL of tartrazine was 0.98% (n=10). The method was successfully applied to the determination of tartrazine in lemon, and papaya-flavoured gelatin, candy, and in fruit syrup.

The gluten protein network is of great importance for pasta cooking quality. Redox agents were used as a tool to impact the protein network formation during laboratory scale fresh pasta making (mixing and sheet rolling) and cooking. SE- and RP-HPLC data showed that disulphide bonds are formed in the pre-existing gluten protein network during cooking of fresh pasta and that, in the process, glutenin polymerisation occurs faster than gliadin-glutenin copolymerisation. The thiol blocking agent N-ethylmaleimide (245ppm, expressed on semolina, dry basis) and, to a lesser extent, the oxidising agent potassium iodate (70ppm), hindered glutenin polymerisation and gliadin-glutenin copolymerisation during cooking. However, the introduction of reactive thiol groups, by addition of the reducing agent glutathione (100ppm), resulted in faster gliadin-glutenin copolymerisation during cooking.

Iodised salt compositions formulated with potassium iodate typically have iodate content of 20–40 ppm (μg/g) which translates to iodine content of 15–30 ppm. The technique of iodide estimation in brine by ion chromatography with amperometric detection was applied to iodate estimation in salt. The method involved reduction of iodate to iodide with excess sodium bisulphite followed by estimation of iodide. No other pre-treatment was necessary for iodate estimation in the concentration range of interest for iodised salt. Quantitative analysis was feasible for iodate concentrations ⩾5 ppm in salt. Iodised salt formulations containing iodide and iodate together were also analysed and the two constituents were quantified separately. Interferences from impurities normally present in salt were insignificant. An important advantage of the present method is that it eliminates the possibility of misleading results from potential adulterants which can impart positive iodometric test while, at the same time, keeping the analytical procedure simple.

The gluten proteins, gliadin and glutenin, are important for wheat flour functionality and they undergo changes during heat treatment involving sulfhydryl (SH) groups. To change the level of SH-groups during hydrothermal treatment, the oxidant, potassium iodate (2.1 mu mol/g protein) and the reducing agent dithiothreitol (DTT, 6.1 mu mol/g protein) were added to 20% (w/w) gluten-in-water suspensions at room temperature, at 90 degrees C and after 15 min at 95 degrees C, and the viscosity was measured by the Rapid Visco Analyser (RVA). Protein extractabilities after hydrothermal treatment were determined by size-exclusion and reversed-phase HPLC. DTT decreased maximal RVA viscosity and the levels of extractable alpha- and gamma-gliadin and this decrease was independent of the time of addition during hydrothermal treatment. In contrast, potassium iodate increased the levels of extractable alpha- and gamma-gliadin. Its impact was less when added at later times during RVA analysis. A SH-blocking agent (N-ethylmaleimide, 8.0 mu mol/g protein), added at room temperature to the gluten suspension, decreased RVA viscosity at 95 degrees C and increased the extractabilities of glutenin and alpha- and gamma-gliadin after hydrothermal treatment. Subsequent addition, at 90 degrees C, of a reducing agent (glutathione, 3.1 and 6.2 mu mol/g protein) recovered the control RVA profile and restored the control protein extractabilities after RVA analysis. This shows the importance of heat-induced gliadin-glutenin reactions for gluten viscosity and of the presence of free SH-groups for the polymerization of gluten proteins. A model explaining gliadin-glutenin polymerization through a sulfhydryl-disulfide exchange mechanism and demonstrating the effects of redox agents is put forward. (C) 2007 Elsevier Ltd. All rights reserved. ispartof: Food chemistry vol:107 issue:2 pages:753-760 status: published