Red pitaya (Hylocereus polyrhizus) peel is a rich source of fibre, antioxidant and betacyanin; however, it is discarded during processing, so it is able to cause environmental problems. In order to convert the fruit waste to potential by-product ingredients, drum drying is used as pre-treatment to create an ingredient which is shelf-stable. In this study, the effects of rotation speed and steam pressure of drums on the physico-chemical properties of pitaya peel that had undergone drum drying are investigated. Pitaya peel was dried in a laboratory scale double drum dryer at rotation speed of 1, 2, and 3 rpm at steam pressure of 1, 2, and 3 bar. The drum dried pitaya peel was then further analyzed based on percentage yield, moisture content, water activity, betacyanin retention and color change. Interaction of steam pressure and rotation speed gives significant effect (p < 0.05) on percentage yield, moisture content, water activity, betacyanin retention and Hunter L value, whereas it has no significant on Hunter a and b values. The best combination parameters (1 rpm and 2 bar) yield the highest betacyanin retention (80.21 mg/g of dry solid), acceptable moisture content (10.66% wet basis), water activity (aw = 0.42) and with 7.61% of yield.
Hempedu bumi (Andrographis paniculata, AP), also known as the king of bitters, is an herb commonly found in Asian communities for medicinal usage. The drying behaviour of AP at temperatures of 40, 50, and 60oC with vacuum pressures of 10 and 30 kPa was investigated in this study. The data were then fitted with semi-theoretical and theoretical thin-layer drying models. The results reveal that the drying time is significantly (p
Ice cream contains high sugar content and therefore it is in contradiction with the concept of healthy diet. The objective of this study is to determine the suitability of using stevia as an alternative natural sweetener in making ice cream. In- house ice cream formulation (as the control) and three different concentrations of stevia ice cream formulations of (A, B and C) were used. Physical properties of the ice cream such as the overrun, total soluble solid, meltdown rate, rheology, and textural properties were evaluated. All ice cream samples exhibited a nonNewtonian flow with pseudoplastic behavior. Stevia ice cream has a lower melting rate and has a higher sustainability. The power law also showed that apparent viscosities of stevia ice cream were higher. Therefore, stevia can be used as a natural sugar substitute in ice cream production.
Traditional drying methods involve high temperatures that degrade heat-sensitive compounds.
Dehumidified-air drying, an alternative to traditional drying methods, is suitable for heatsensitive
compounds; however, it consumes a large amount of energy and is comparatively
expensive. In this study, a multi-chamber dehumidified-air dryer was designed to dry Hydrocotyle
bonariensis, and the retention of the polyphenol content of Hydrocotyle bonariensis under
various drying conditions was examined. Multi-chamber dehumidified-air drying involves two
chambers; each chamber was operated at temperatures of 30, 40, and 50o
C with air volumetric
flow rates of 30 and 50 L/min. The results indicated that the highest retention of total phenolic
content and total flavonoid content, 24.67 mg of GAE/g dry weight (DW) and 2.204 mg of
catechin/g DW, respectively, was obtained at 50o
C with a 50 L/min air flow rate in the first
drying chamber. Multi-stage dehumidified-air dryers have the potential to dry heat-sensitive
products with reduced energy consumption.