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The aim of this study was to test the usability of fluorescence spectroscopy to evaluate the stability of cold-pressed rapeseed oil during storage. Freshly-pressed rapeseed oil was stored in colorless and green glass bottles exposed to light, and in darkness for a period of 6 months. The quality deterioration of oils was evaluated on the basis of several chemical parameters (peroxide value, acid value, K232 and K270, polar compounds, tocopherols, carotenoids, pheophytins, oxygen concentration) and fluorescence. Parallel factor analysis (PARAFAC) of oil excitation-emission matrices revealed the presence of four fluorophores that showed different evolution throughout the storage period. The fluorescence study provided direct information about tocopherol and pheophytin degradation and revealed formation of a new fluorescent product. Principal component analysis (PCA) performed on analytical and fluorescence data showed that oxidation was more advanced in samples exposed to light due to the photo-induced processes; only a very minor effect of the bottle color was observed. Multiple linear regression (MLR) and partial least squares regression (PLSR) on the PARAFAC scores revealed a quantitative relationship between fluorescence and some of the chemical parameters.

Temperature-programmed reduction (TPR) measurements were performed for iron oxalates, iron(III) hydroxide (both pure and with additives) and iron(II, III) oxide. On the ground of TPR curves, reduction temperatures of the iron-containing parent substances were chosen followed by oxygen uptake determination. Comparison of oxygen uptakes points to the use of Fe(OH) 3 and Fe 3 O 4 as more advantageous than that of iron oxalates. Co-precipitation from a mixed solution of iron and manganese salts results in a product which is more resistant to particle agglomeration at elevated temperatures than that obtained by precipitation from solution of iron salt alone.

The aim of the research was to determine the influence of chitosan type and propolis extract concentration on biological and physicochemical properties of chitosan-propolis films in terms of their applicability in food packaging. The films were prepared using three types of chitosan: from crab shells, medium and high molecular weight and propolis concentration in the range of 0.75–5.0%. The prepared polysaccharide films were tested for antimicrobial properties, oxygen transmission rate (OTR) and water vapor transmission rate (WVTR). Moreover, sorption tests and structural analysis were carried out. Microbiological tests indicated the best antimicrobial activity for the film consisting of high molecular weight chitosan and 5.0% propolis extract. Both the type of chitosan and propolis concentration affected transmission parameters—OTR and WVTR. The best barrier properties were recorded for the film composed of high molecular weight chitosan and 5.0% propolis extract. The results of sorption experiments showed a slight influence of chitosan type and a significant effect of propolis extract concentration on equilibrium moisture content of tested films. Moreover, propolis extract concentration affected monolayer water capacity (Mm) estimated using the Guggenheim, Anderson and de Boer (GAB) sorption model. The obtained results indicate that chitosan films with an addition of propolis extract are promising materials for food packaging applications, including food containing probiotic microorganisms.

The aim of this study was to explore the influence of different barrier and atmosphere conditions on the complex processes affecting storage stability of potato snacks, and the use of oxygen determination measurements within the packaging atmosphere as a quick quality and shelf-life assessment method. The subject of investigation was potato snacks packed in transparent and metallised polymeric packaging laminates, filled with air or nitrogen. Samples were analysed for moisture, water activity, hydroperoxide content and oxygen concentration in the headspace by two methods: a non-invasive optical method based on fluorescence quenching and an electrochemical method. High barrier packaging provides better protection against moisture but not against oxidation. The shelf-life of potato snacks is undermined by oxygen presence in the foam structure of the product. Neither barrier packaging nor modification of atmosphere applied alone bring satisfactory results, therefore a combined strategy is recommended. The study proved that the most optimal solution was the use of metallised packaging with nitrogen. The use of an optical sensor can be an appropriate and effective novel method for a nondestructive oxidation progress evaluation of food that is stored in translucent packaging.Practical applications: The high linear correlation between hydroperoxides and oxygen content is of great practical value in shelf-life assessment and screening the correctness of a packaging process.Abbreviations: ASTM, American society for testing and materials; HSD, honestly significant difference; OTR, oxygen transmission rate; PA, polyamide; PE, polyethylene; PV, peroxide value; WVTR, water vapour transmission rate Eur.

In her last novel, The Finishing School, Muriel