Effect of Roasting Conditions on Hardness, Moisture Content and Colour of Pistachio Kernels

Abstract

Roasting of whole-kernels is an important step in the production of pistachio paste. The effect of hot air roasting temperatures (90-190°C) and times (5-65 min) on the hardness, moisture content and colour attributes ('L', 'a' and 'b' values and yellowness index) of both whole-kernel and ground-state were investigated using response surface methodology (RSM). Increases in roasting temperature and time caused a decrease in all the responses except for 'a' value of ground-state. The interaction and quadratic models sufficiently described the changes in the hardness and colour values, respectively. The result of RSM analysis showed that hardness and colour attributes ('L' and 'b' values, yellowness index) of kernels and 'a' value of ground-state could be used to monitor the roasting quality of whole-kernels. This study showed that the recommended range of roasting temperature and time of whole-kernel for the production of pistachio paste were 130-140°C and 30-40 min, respectively.

Simultaneous multiple responses modelling, optimisation and correlation of Asian type peanuts (Arachis hypogaeaL.) roasting using response surface methodology

“…All the responses decreased with increase in roasting time and temperature (Figs 1-4). The observed results are in agreement with previous studies (KAHYAOGLU & KAYA, 2006;SHAKERARDEKANI et al, 2011) on texture and physical changes during pistachios and sesame seeds roasting, respectively. During a roasting process, as browning and caramelisation reactions progress, the brown pigments increase (SAKLAR et al, 2003) resulting in decrease of the L˗value of the colour.…”

“…This suggests that moisture content could be used to predict the textural properties of roasted peanuts in this experiment. Moisture content proved to be an important parameter during roasting of nuts, contradicting to previous studies on roasting of pistachio kernels (SHAKERARDEKANI et al, 2011) and sesame seeds (KAHYAOGLU & KAYA, 2006), but agreeing with the studies of HUNG (2000) and HUNG and CHINNAN (1989) on roasted peanut, where textural quality either in the form of hardness, crispiness, or crunchiness is strongly related to the moisture content. As colour attribute usually associates with fl avour and aroma compounds (JOHNSEN et al, 1988;SMYTH et al, 1998) or the breakdown of the chemical structure of peanut, such as arachin (SLADE & LEVINE, 2006), the good correlation between moisture and colour makes them a benefi cial attribute in describing other changes in chemical or physical properties of peanuts during roasting.…”

“…A second˗order polynomial equation in a function of X, was fi tted for each factor assessed (MENDES et al, 2001;KAHYAOGLU & KAYA, 2006;KAHYAOGLU, 2008;NIKZADEH & SEDAGHAT, 2008;AKINOSO & RAJI, 2011;SHAKERARDEKANI et al, 2011;YOUN & CHUNG, 2011;DE CONTO et al, 2012):…”

Physicochemical Changes of Cocoa Beans during Roasting Process

“…Color is widely used in roasted beans as an indicator of the progress of browning and caramelization reactions, temperature being the main factor that causes these changes [24,28,29].…”

Sensory and instrumental texture assessment of roasted pistachio nut/kernel by partial least square (PLS) regression analysis: effect of roasting conditions

“…There are also some studies on the effect of roasting on sensory and textural properties of nuts such as Kita and Figiel for walnuts (2006); Cea et al for peanuts (2008); Nikzadeh and Sedaghat (2008); Raei et al (2009) and Shakerardekani et al (2011) for pistachio nuts. However, to our knowledge, there is no study available concerning the effect of different combinations of time, temperature and air velocity of roasting process on sensory and textural properties and the relation between sensory and texture properties of pistachio nuts.…”