Carotenoid and color changes in traditionally flaked and extruded products.

The objective of this study was to evaluate the impact of process and formulation on individual carotenoid loss in traditionally prepared cornflakes and those prepared by extrusion. The first step in the traditional process (maize grits cooking) promoted a 60% lutein content reduction and 40% in zeaxanthin loss, showing lutein more susceptibility to isomerization and decomposition. After toasting, the last step, the total loss averaged 80% for both compounds. The extruded maize in a plain formulation showed a 35% lutein and zeaxanthin reduction. However, in samples containing quinoa the decrease reached 60%, and the major loss (80%) was found in chia-containing formulations. Correlations between the color coordinate b∗, total and individual carotenoid content, were obtained. It is of a major importance that the efforts to increase carotenoid content in raw materials are complemented with attempts to reduce the losses during processing.

Non-enzymatic browning kinetics analysed through water-solids interactions and water mobility in dehydrated potato.

Non-enzymatic browning (NEB) development was studied in dehydrated potato at 70°C. It was related to the macroscopic and molecular properties and to water-solid interactions over a wide range of water activities. Time resolved (1)H NMR, thermal transitions and water sorption isotherms were evaluated. Although non-enzymatic browning could be detected in the glassy state; colour development was higher in the supercooled state. The reaction rate increased up to a water content of 26g/100g of solids (aw=0.84) and then decreased at higher water contents, concomitantly with the increase of water proton mobility. The joint analyses of NEB kinetics, water sorption isotherm and proton relaxation behaviour made it evident that the point at which the reaction rate decreased, after a maximum value, could be related to the appearance of highly mobile water. The results obtained in this work indicate that the prediction of chemical reaction kinetics can be performed through the integrated analysis of water sorption, water and solids mobility and the physical state of the matrix.

Inhibition of trehalose crystallization by cytoplasmic yeast components.

The influence of different yeast (Saccharomyces cerevisiae) cellular fractions was studied in an attempt to gain knowledge on the feasibility of trehalose crystallization in yeast cells. Certain constituents of S. cerevisiae cells inhibited/delayed trehalose crystallization upon humidification at high relative humidities.