Factors affecting anthocyanin stability and antioxidant activity of Ma-kiang (Cleistocalyx nervosum var. paniala) juice
Ma-kiang is a native plant of the northern parts of Thailand. The ripe fruit is edible, is purplish in colour and contains high levels of anthocyanins, natural compounds known for their antioxidant activity. Ma-kiang fruit is usually consumed as fruit juice. The common thermal processes could be employed to help preserve the fruit, but unfortunately anthocyanins exhibit low stability, particularly during heating and storage. This research aims to study the effect of extraction methods, heating process and storage conditions on anthocyanin stability and the antioxidant activity of Ma-kiang juice. The methods used to extract anthocyanins were hydraulic press and solvent extraction (ethanol: 0, 20, 40, 50, 60 and 80%). The juices were heated at 100°C for 15 min and then studied during storage conditions of 0, 4 and 25°C for five weeks. The total polyphenol and the monomeric anthocyanin (MA) content varied from 504.68 to 1847.35 µg GAE g-1 extract and 94.85 to 385.74 mg L-1, respectively. The heating process significantly decreased the amount of anthocyanins in Ma-kiang juices (p≤0.05). In contrast, the storage condition at a temperature of 4°C minimally affected the stability of MA and the antioxidant activity (t½, MA = 47.65 weeks). In contrast, storage at 0 and 25°C decreased the anthocyanin stability and the antioxidant activity of Ma-kiang juice dramatically (p≤0.05). From this research, the optimal practical method to extract Ma-kiang juice is ethanol 40% extraction and minimal thermal treatment for sterilisation. Moreover, the juice should be kept at 4°C to maintain stability of anthocyanins and preserve the health benefits in Ma-kiang juice.
Puangpraphant, S., Kunarayakul, S. and Worakulpisut, W. (2018). Factors affecting anthocyanin stability and antioxidant activity of Ma-kiang (Cleistocalyx nervosum var. paniala) juice. Acta Hortic. 1213, 417-422
Cleistocalyx nervosum, anthocyanins, stability, antioxidant activity