Effect of infrared wattage and treatment duration on physicochemical properties and sensory attribute of roasted macadamia nuts

Abstract

        Macadamia nuts are highly nutritious nuts, especially with a high content of unsaturated fatty acids and low cholesterol. The function is useful of macadamia to reduce fat in the blood. In addition to being edible, it can also be extracted as an oil that is used as a cosmetic ingredient to increased the moisture and smoothness of the skin. The processing of kernels macadamias firstly involves drying to reduce moisture in the shell. The kernels processed are husks and shell removed and then roasting or frying or baking processing. The rancidity and browning reaction have deteriorated the qualities of the macadamia products to the extended shelf life and are unsuitable to consume. The infrared of electromagnetic waves technique was provides highly efficient heating, short time, maintains a nutritional value, and low unit energy cost to drying kernels macadamia. In this study, the infrared drying instrument was developed to be an automatic infrared conveyor, it was made more convenient to use and more productive. The infrared heating examined optimal conditions were investigated infrared powers of 6,000, 7,200, and 8,000 watts, and 5, 6, and 7 minutes of processed times. The optimal heating condition of kernels macadamia product by infrared technique was found at 7,200 watts of infrared wattage and 6 minutes during processing. That condition was found that the moisture content, aw, L*, a*, b*, and acid value were 1.78 %, 0.35, 77.00, 1.46, 21.40, and 2.99 mg of KOH/gram of kernels macadamia, respectively. In the optimal condition, the sensory attribute was had the highest appearance, odor, flavor, and overall acceptance score. In addition, the calculation of the energy cost of the optimal condition by infrared dryer was had 0.85 baht per kilogram kernels macadamia per 8 hours of work.