Colour optimisation of ground pistachio during roasting

Abstract

In this research, ' Ahmad Aghaei' pistachio cultivar harvested from Iran in 2011 was supplied by the Pistachio Research Institute. The effect of roasting times (5, 10, 15, 20, 25 and 30 min) and temperatures (120, 130, 140, 150 and 160 °C) on the colour of pistachio nuts was investigated. Initially, the L value (lightness) decreased for all temperatures and then increased for 120 and 130 °C with increases in roasting temperature and time. Values of a (redness) and ΔE (colour difference) for pistachio samples showed an increase while b decreased. Changes in L, a and b (yellowness) values of pistachio were used to develop and to validate a numerical dynamic model. The developed prediction models satisfactorily described the colour development as a function of roasting temperature and time for L, a, b and ΔE of ground-state measurements. As a result of variance analysis, the effects of the roasting process on colour values of pistachios were found to be statistically significant. In addition, changes in colour values gave high R² and the obtained nonlinear equations may be utilised to determine the optimum roasting degree based on time and temperature. A reverse approach for modelling is used in order to establish that it is possible to obtain the optimal condition directly from the experimental data modelling step.

Changes in chemical composition of some oils extracted from seeds roasted at different temperatures

“…Oil seeds are roasted in order to promote the flavour, desired colour and changes in texture which ultimately increase the overall palatability of the product. Roasting also improves microbiological safety, digestibility, sensory quality, and shelf life of food products, inactivates enzymes, facilitates oil extraction by destroying cell barriers, and destroys toxic thermolabile substances in nuts and seeds (Karleskind, 1996;Yeganeh, 2013). It induces the formation of healthpromoting components, such as antioxidants (tocols and phenolic compounds), but also leads to the formation of heat-induced contaminants such as acrylamide, furans and furfurals, may also induce the isomerisation of double bonds, leading to the formation of trans fatty acids, lipid peroxidation, may increase the primary (hydroperoxides) and secondary (aldehydes/ketones) lipid oxidation products (Durmaz and Gökmen, 2010).…”