Effect of extrusion conditions and formulation on characteristics of snack corn and pistachio

Snacks are referred to as food that are eaten between main meals and the amount is less than the main meal. In order to increase the nutritional value of this popular snack, additives such as dairy products, meat, fish, vegetables, fruits, legumes, various cereals and snacks such as pistachios, walnuts, almonds and peanuts, etc. can be used. Pistachios are rich in copper, magnesium and a variety of B vitamins, so in order to increase the nutritional value of snacks, pistachios can be used in its preparation.

In this study, pistachios with variable ratios of 7, 14 and 21% in bulk grain formulations based on corn flour as well as moisture of 12, 15 and 18% and spiral rotation speed were 120, 150 and 180 rpm. The constant temperature extruder was 120 ° C in the second region and 145 ° C in the third region, and the constant feed rate was 40 kg / h. Tests performed were included physical characteristics (mass density, expansion ratio and tissue hardness), functional properties (water absorption index, water solubility index, oil absorption index, peroxide number), colorimetric and sensory components as well as characteristics The microstructures of the extruded product were examined. This study was conducted in the form of response level method (RSM) and Box-Behnken design and to analyze the changes, Minitab statistical software version 17 was used.

As it turns out, the most important issue in preparing snacks is its taste and texture. With the increase of pistachios in snack production samples, the amount of tissue hardness increased, while the satisfaction with the taste of snacks increased. In addition, increasing pistachios reduced a * and b * and the colors tended to be green and yellow. Increasing the humidity increased the expansion ratio, mass density, hardness and water absorption of the snack. Increasing the rotation speed of the spiral reduced the brightness and water absorption of the snack. Examination of the microstructural properties of the snack performed on the optimal sample showed that the amount of puffiness of the snack was appropriate and the wall diameter of the bubbles formed was less than 17 micrometers. The walls of the bubbles are almost smooth, which indicates that the pistachios are well mixed with the corn, as well as the good mixing of fat globules with flour.

According to the results, the optimal process conditions including screw speed, pistachio kernel and feed moisture were 150 rpm, 14% and 15%, respectively.