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Postharvest pre-storage processing improves antioxidants, nutritional and sensory quality of macadamia nuts

Duduzile Buthelezi, Nana Millicent, Samukelo Magwaza, Lembe, Zeray Tesfay, Samson
Scientia horticulturae 2019 v.251 pp. 197-208
Macadamia, air, antioxidant activity, antioxidants, catechol oxidase, cultivars, drying, enzyme activity, flavonoids, macadamia nuts, models, monounsaturated fatty acids, ovens, peroxide value, polyphenols, rancidity, roasting, seeds, sensory properties, water content
Macadamia nut is rich in monounsaturated fatty acids, which are known to reduce the risk of cardiovascular diseases when included as part of a healthy human diet. On the negative side, high concentrations of unsaturated fatty acids lead to oxidative reactions, which result in rancidity thus decreases the quality of the nut. Drying and roasting are, therefore, needed to reduce moisture content and hence alleviate the above-mentioned problems. This research was conducted to evaluate and compare the quality properties of raw and roasted macadamia nuts during the accelerated storage of 70 days. Two commercially important macadamia cultivars, namely, ‘A4’ and ‘Beaumont’ were used as model cultivars. Nuts were roasted at 125 °C for 15 min using a hot air oven dryer. Roasted kernels of ‘A4’ and ‘Beaumont’ cultivars had significantly lower concentration of peroxide value (PV), high concentration of flavonoids, phenols and antioxidants activity and good sensory quality compared to raw kernels which had a higher concentration of polyphenol oxidase activity, PV, low concentration of flavonoids, phenols and antioxidant activity and poor sensory quality during the accelerated storage of 70 days. These results indicated that roasting significantly improved kernel quality and shelf life of ‘A4’ and ‘Beaumont’ macadamia cultivars.