Lemon myrtle (Backhousia citriodora) is one of the most commercially grown native herbs in Australia. This study aimed to evaluate the effects of different drying methods on phenolic compounds and antioxidant properties of lemon myrtle leaves to identify the most suitable drying conditions. The drying methods include hot air drying, vacuum drying, microwave drying, sun drying, shade drying and freeze drying. The results showed that drying conditions significantly (p < 0.05) affected the retention of total phenolic content (TPC), total flavonoids (TFC), proanthocyanidins, gallic acid, hesperetin, and antioxidant properties of lemon myrtle leaves. The optimal conditions for hot air drying and vacuum drying are 90 °C for 75 min and 90 °C for 120 min, respectively; whereas optimal drying conditions for microwave drying are 960 W for 7 min, and the time required for sun drying and shade drying are 2 days and 12 days, respectively. The freeze dried leaves contained the highest level of TPC, TFC, proanthocyanidins, gallic acid and hesperetin (74.11 ± 2.87 mg GAE/g dw, 87.15 ± 2.70 mg CE/g dw, 123.49 ± 6.12 mg CE/g dw, 53.77 ± 0.22 mg/g dw and 38.99 ± 0.26 mg/g dw, respectively). The freeze dried leaves also contained higher antioxidant capacity as compared to other samples. No significant difference in phenolic compounds and antioxidant capacity was observed between tested other drying methods. Therefore, any of these methods can be selected for dehydration of lemon myrtle leaves for industrial purposes. However, microwave drying can be selected for drying of lemon myrtle leaves for an industrial scale as it was the most time and/or energy efficient technique.

This research was conducted aiming to assess the flow and physicochemical properties of fruit powder and their relationship with the dissolution of tablets containing effervescent agents. Commercial pitaya, pineapple, mango and guava fruit powders were used as samples in this research. Fruit powder tablets were prepared by using direct compaction method. Powder properties of individual fruits as well as their tablet formulation (fruit powder + effervescent agent + artificial sweeteners) analysed using standard methods were found significantly different at P < 0.001. The flowability and cohesiveness as determined by Carr index and Hausner ratio of individual fruit powders and their formulation were also different but in the range of passable class. The relationship of total dissolution time with moisture, protein, fat content and porosity of fruit powder tablets was polynomial as determined by multiple regression analysis. Dissolution rate of effervescent fruit powder tablets was much higher compared to normal fruit powder tablets in both dissolution medium (water and simulated saliva fluid). Among the fruit powder tablets, pitaya powder tablet went for fast dissolution (6 min) in simulated saliva fluid whereas guava powder tablets took the longest time (90 min) for complete dissolution in water. Based on this study, a better understanding of the physicochemical properties of fruit powder and their relationship with the dissolution rate and the effect of effervescent agents on the dissolution rate has been obtained, which is essential for processing and handling of fruit powder and tablet preparation as well as for the improvement of the dissolution rate.

Leptospermum petersonii is a native Australian medicinal and aromatic plant. This study was designed to evaluate the influence of solvents and ultrasound-assisted extraction (UAE) parameters including time, temperature, and sonication power on the yield of phenolic compounds and antioxidant capacity from lemon scented tea tree leaves. Extraction efficiency of the optimal UAE conditions were compared with that of shaking water bath technique. The results show that extraction solvents significantly affect extraction yield of phenolic compounds and antioxidant properties, and 50% acetone in water was found to be the most suitable solvent. The UAE optimal conditions were 60 min, 50 C and sonication power of 200 W. Under these optimal conditions the yields of total phenolics, flavonoids, proanthocyanidins were 98.91 AE 1.20 (mg GAE/g DW), 76.12 AE 0.79 (mg CE/g DW), 117.71 AE 2.18 (mg CE/g DW), respectively. Antioxidant properties from four assays including FRAP, CUPRAC,

The tableting of fruit powders is gaining popularity due to conveniences in its use, storage, transportation, and product formulation. Food powders are generally cohesive in nature, and their compressibility is highly correlated with the material properties of the powder. Here, the material properties of fruit powders and their respective compressibilities in relation to powder type, drying technique and their operating parameters, portion of the fruit used to produce the fruit powder, and drying aids are discussed. Among the material properties analyzed, moisture content, water activity, particle density, particle size and shape, and powder surface properties are identified as vital properties that highly influence the tableting behavior of fruit powders. The Kawakita and Lüdde model and Heckel equation are widely studied to describe the compressibility and compactibility of fruit powders. A four-parameter model fits the sigmoidal compression data of food powders well.