Incorporation of fingerroot (Boesenbergia sp.) rhizome extract powder on chemical, microbial and sensory properties of dry-roasted macadamia (Macadamia sp.) nut during 12 months of storage

Abstract

Macadamia nut is an important crop with high economic value. It is commonly dried and roasted into an instant crisp. Due to high oil content, the dry-roasted macadamia nut is feasible to oil rancidity as well as microbial contamination. In order to improve the economic value of macadamia nuts, it is very urgent to stabilise the quality of roasted macadamia nuts during storage and distribution. Fingerroot (Boesenbergia sp.) belonging to the Zingiberaceae family is one of the most important Vietnamese perennial medicinal plants. Its rhizome contained numerous bioactive phytoconstituents like essential oils, flavonoids, phenolics exhibiting diversified biological activities beneficial for human health. This research evaluated the possibility of incorporation of fingerroot rhizome extract powder (0-6%) into the dry-roasted macadamia nut to improve its chemical, microbial and sensory properties during 12 months of storage. Results showed that 4.5% of fingerroot rhizome extract powder could be supplemented into the dry-roasted macadamia nut to reduce coliform load (1.28±0.03 log CFU/g), peroxide value (0.78±0.02 meq/kg), thiobarbituric acid reactive substances (0.65±0.03 mg malonaldehyde/kg), free fatty acid (0.76±0.02% oleic acid) while enhancing overall acceptance (8.24±0.17 score). This research revealed that fingerroot rhizome extract would be a promising antimicrobial and antioxidant natural source to preserve fatty foodstuffs efficiently.