Abstract
Roasting is a key process in production of nuts. Improving the flavor and crispiness of texture in nuts is considered as a purpose of roasting, which increases the overall acceptance of the product. This review aims to introduce the infrared method as a new technique of roasting and evaluate the quality characteristics of some nuts after infrared roasting. Usually, the traditional roasting methods are time-consuming with high energy consumption and low production efficiency. One of the best ways to decrease roasting time and energy consumption is to provide heat by infrared (IR) radiation. However, the low penetration power of infrared radiation is one of the limitations of this method. The combination of infrared with other thermal methods can overcome this limitation. Studies have been done on roasting of nuts and other foods by different IR roasting methods such as IR, IR-hot air, and IR-microwave roasting methods. This paper reviews the effect of different IR roasting methods on the quality characteristics of roasted pistachio, peanut, hazelnut, almond, sunflower, soybean, and other food products. IR heating has been applied successfully to the roasting of some nuts. The use of infrared roasting has several advantages in comparison with traditional convective roasting methods. According to the results of most of these studies, the combination of infrared with other thermal methods to roast nuts has distinctly improved the potential of the technology as compared to the IR roasting alone.
Highlights
Roasting is known as a thermal time-temperature-dependent process at high temperatures (>150°C)
Since the penetrating power of infrared rays is limited to the depth of nuts, the combination of infrared with other thermal methods such as hot air, microwave, vacuum, and other states of convection and conduction can overcome this limitation. e capability of the combination of infrared rays with other roasting methods is weighed as one of its outstanding features
Roasting is the typical shape of sunflower seed processing, and the purpose is to increase the total acceptability of the product [28]. e effect of infrared (IR) power (400–600 W) and roasting time (4–10 min) on energy consumption, color parameters (L∗, a∗, and b∗ values, ΔE, BI, SI, WI, h°), texture, moisture content, and sensory properties of sunflower kernel was investigated by Mosayebi et al [28]
Summary
Roasting is known as a thermal time-temperature-dependent process at high temperatures (>150°C). Hot pan, and oven are basic ways for roasting nuts These roasting methods are time-consuming and have high energy consumption and low production efficiency [6]. Hot air roasting is one of the simplest convective methods of heating with low operating costs and is commonly applied for roasting of nuts. This system requires high thermal energy and extended time for roasting and results in adverse changes in the final product, mainly due to the Maillard reaction [4, 7]. Infrared (IR) radiation is energy in the form of electromagnetic wave and is more rapid in heat transfer than convection and conduction mechanisms. The fraction of energy between the sample surface and the wall surface. e heat transfer coefficient, hr (W/m2K), is calculated using the following equation: hr AIF
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