Chalida Niamnuy

Evaluation of bioactive compounds and bioactivities of soybean dried by different methods and conditions

Soybean has attracted significant research and commercial interests due to its many health-promoting bioactive compounds, especially isoflavones (β-glucosides, malonyl-β-glucosides, acetyl-β-glucosides and aglycones). Isoflavones possess antioxidant activity and α-glucosidase inhibitory activity, which has proved effective in the treatment of type 2 diabetes mellitus. Prior to its use, however, soybean needs to be dried to extend its storage life and to prepare the material for subsequent food or pharmaceutical processing. The present study investigated the effects of drying methods and conditions on the drying characteristics, isoflavones, antioxidant activity and α -glucosidase inhibitory activity of dried soybean. Hot-air fluidized bed drying (HAFBD), superheated-steam fluidized bed drying (SSFBD) and gas-fired infrared combined with hot air vibrating drying (GFIR-HAVD) were carried out at various drying temperatures (50, 70, 130 and150°C). The results showed that higher drying temperatures led to higher drying rates and higher levels of β-glucosides and antioxidant activity, but to lower levels of malonyl-β-glucosides, acetyl-β-glucosides and total isoflavones. At the same drying temperature GFIR-HAVD resulted in the highest drying rates and the highest levels of β-glucosides, aglycones and total isoflavones, antioxidant activity as well as α-glucosidase inhibitory activity of dried soybean. A drying temperature of 130°C gave the highest levels of aglycones and α-glucosidase inhibitory activity in all cases. The relationships between all the studied parameters were monitored and simple correlations between them were determined.

Bioactive Compounds and Bioactivities of Centella asiatica (L.) Urban Prepared by Different Drying Methods and Conditions

Centella asiatica (L.) Urban has attracted significant research and commercial interest due to its many health-promoting bioactive compounds, especially phenolic compounds and triterpene saponins, which possess several functional capacities, including antioxidant activity and antimicrobial activity. Prior to its use, however, C. asiatica usually needs to be dried to extend its storage life and to prepare the material for subsequent pharmaceutical processing. The present study investigated the effects of selected drying methods and temperature on the drying characteristics, phenolic compounds, triterpene saponins, antioxidant activity, and antimicrobial activity of dried C. asiatica. Hot-air drying (HAD), combined infrared–hot air drying (IR-HAD), and low-pressure superheated steam drying (LPSSD) were carried out at various temperatures (50, 60, 70°C). The results showed that higher drying temperatures led to higher drying rates but to lower levels of total phenolic compounds, total triterpene saponins, antioxidant activity, and antimicrobial activity. At the same drying temperature, IR-HAD resulted in the highest drying rates; this was followed by LPSSD and HAD in a descending order. Nevertheless, LPSSD resulted in the highest levels of the tested bioactive compounds, antioxidant activity, as well as antimicrobial activity. LPSSD at 50°C yielded dried C. asiatica of the best overall quality.

Stabilization of rice bran via different moving-bed drying methods

ABSTRACT Stabilization of rice bran after milling is a necessary step to avoid subsequent oxidation of lipids in the bran. Selected moving-bed drying methods, i.e., hot-air fluidized bed drying (HAFBD), superheated-steam fluidized bed drying (SSFBD), and infrared vibrated bed drying (IRVD), were used to reduce the moisture content of the bran and, at the same time, inactivate deleterious enzymes, which are the cause of oxidation. Drying kinetics, oxidative stability parameters (i.e., lipase activity, free fatty acid content, and peroxide value), oil extraction yield, and contents of phenolic compounds and γ-oryzanol as well as color changes of the bran were determined. SSFBD could reduce the drying time by 8–22 and 76–79% in comparison with HAFBD and IRVD, respectively. Drying method significantly affected the total phenolic content (TPC) and total color changes but did not significantly affect the γ-oryzanol content of the bran. SSFBD resulted in the lowest levels of all oxidative stability parameters and to the highest TPC and oil extraction yield. SSFBD at 140°C resulted in the bran with the longest shelf life of 55 days and is suggested as an alternative method to shorten the stabilization process and maintain the stability of rice bran.

Preparation and physico-chemical properties of hydrogels from carboxymethyl cassava starch crosslinked with citric acid

Recently, environmentally friendly hydrogels prepared from renewable bio-based resources have drawn significant attention from both industrial and academic sectors. In this study, chemically crosslinked hydrogels have been developed from cassava starch which is a bio-based polymer using a non-toxic citric acid as a crosslinking agent. Cassava starch was first modified by carboxymethylation to improve its water absorbency property. The carboxymethyl cassava starch (CMCS) obtained was then crosslinked with citric acid at different concentrations and reaction times. The gel fraction of hydrogels increased progressively with increasing citric acid concentration. Free swelling capacity of hydrogels in de-ionized water, saline solution and buffers at various pHs as well as absorption under load were investigated. The results revealed that swelling behavior and mechanical characteristic of hydrogels depended on the citric acid concentration used in reaction. Increasing citric acid concentration resulted in hydrogels with stronger network but lower swelling and absorption capacity. The cassava starch hydrogels developed were sensitive to ionic strength and pH of surrounding medium, showing much reduced swelling capacity in saline salt solution and acidic buffers.