FT-IR and Raman spectroscopies determine structural changes of tilapia fish protein isolate and surimi under different comminution conditions

Effects of calcium ion on gel properties and gelation of tilapia (Oreochromis niloticus) protein isolates processed with pH shift method

The effect and mechanisms of calcium chloride and citric acid addition on the acid method of processing tilapia protein isolates and surimi gels were studied. The alkaline method shows better gel quality than the acid method with lower yield and high lipid content. The addition of calcium chloride increased the breaking force to 494.56 g and citric acid helped reducing the lipid content by 85.85%, resulting in a higher yield of 75.36%. Gels with calcium maintained low levels of expressible moisture (2.30%), indicating a well-organised gel matrix. The decrease in -SH content and increase in ionic bonds content suggested increased formation of disulphide bonds and ionic bonds. Oscillatory dynamic measurement indicated that more heat resistant bonds were formed. The morphology of myofibril proteins studied by atomic force microscopy (AFM) showed that the height of the proteins in the calcium-added gels decreased 79.4%, which suggested that the protein structure was "suppressed".

Bare carbon electrodes as simple and efficient sensors for the quantification of caffeine in commercial beverages

Food quality control is a mandatory task in the food industry and relies on the availability of simple, cost-effective and stable sensing platforms. In the present work, the applicability of bare glassy carbon electrodes for routine analysis of food samples was evaluated as a valid alternative to chromatographic techniques, using caffeine as test analyte. A number of experimental parameters were optimized and a differential pulse voltammetry was applied for quantification experiments. The detection limit was found to be 2 × 10^-5 M (3σ criterion) and repeatability was evaluated by the relative standard deviation of 4.5%. The influence of sugars, and compounds structurally related to caffeine on the current response of caffeine was evaluated and found to have no significant influence on the electrode performance. The suitability of bare carbon electrodes for routine analysis was successfully demonstrated by quantifying caffeine content in seven commercially available drinks and the results were validated using a standard ultra-high performance liquid chromatography method. This work demonstrates that bare glassy carbon electrodes are a simple, reliable and cost-effective platform for rapid analysis of targets such as caffeine in commercial products and they represent therefore a competitive alternative to the existing analytical methodologies for routine food analysis.