Effect Of Pre-Treatment And Drying Temperature On The Properties Of GAC Powder

Abstract

Gac fruit has a high content of antioxidant, especially carotenoids. These carotenoids are currently in special demand as they are natural antioxidants with potential to prevent cancers. The objectives of this research were to study the optimum drying condition to produce gac powder, study the waste utilization from gac skin as a powder, and investigate the physical and chemical properties of dried gac powder. Annova completely randomized factorial design was used to study the effect of different pre-treatment (blanching and adding of ascorbic acid) and dried using tray dryer at different temperature (50 and 60ºC) until moisture content in range of 5.8-6.4%. The results showed that the best dried gac powder was from the ascorbic acid pre-treated, using aril pulp and dried at 50°C due to the less amount of antioxidant loses. Physical properties showed bulk density value 0.65±0.02 g/mL and water solubility index (WSI) 36.42±3.11 %. Color properties showed lightness (23.55±2.43), with redness (a*) (23.48±1.27) and yellowness (b*) (39.72±2.97) (p<0.05). Aril and pulp mixture using ascorbic acid as pretreatment at 50ºC has the highest value in total carotenoid content (TCC) (93.49±11.35 mg β-carotene/100 mL samples),total phenolic compound (TPC) (467.44±7.64 μg GAE/g), DPPH (43.57±1.61 mmol Trolox/100g) and FRAP assay (598.22±18.59 μmol AAE/100g) (p<0.05) compared to other sample (p<0.05). Gac peel sample with blanching and dried at 60°C showed the lowest value of TCC (32.40±2.23 mg β-carotene/100 mL samples), TPC (0.62±0.03 mg GAE/g), DPPH (15.67±1.02 mmolTrolox/100g), and FRAP assay (194.00±7.84 μmol AAE/100g). The aril-pulp mixture showed the highest TCC, TPC, DPPH and FRAP value compared to peel significantly (p<0.05). Peel with ascorbic acid pre-treatment and dried at 50°C had the greatest antioxidant activities among the peel samples.