Drying kinetics,physico‐chemical properties,antioxidant activity and phenolic composition of foam‐mat dried germinated rice bean (Vigna umbellata) hydrolysate

This research was aimed to study physico‐chemical properties and antioxidant activities of foam‐mat dried germinated rice bean (Vigna umbellata) hydrolysate. Germination led to an increase in released phenolic content and antioxidant activity (DPPH radical scavenging activity and FRAP) of rice bean hydrolysate. The hydrolysate obtained from germinated rice bean (GRB) and non‐germinated rice beans (NGRBs) was foam‐mat dried at 60 and 70 °C. Semi‐theoretical and empirical model could suitably describe the drying characteristic of foamed bean hydrolysate. Total phenolic content and antioxidant activities of foam‐mat dried samples decreased with increasing air‐drying temperature (P ≤ 0.05). Gallic acid, catechol and epicatechin were major phenolic compounds in foam‐mat dried samples prepared from both GRB and NGRB. The higher phenolic content and antioxidant activities were found in foam‐mat dried hydrolysate of GRB. Electron spin resonance spectrometry revealed that foam‐mat dried rice bean hydrolysate showed a strong ability to scavenge free radicals, especially carbon‐centred radicals.     

Microwave-assisted heating of cementitious materials: Relative dielectric properties,mechanical property,and experimental and numerical heat transfer characteristics

The characteristics of cementitious materials subjected to microwave energy are presented. First, the dielectric properties of cementitious materials during a 24-hour first-hydration period were measured at a frequency of 2.45 GHz. Second, the characteristics of hardened cement paste as subjected to heating for a short period (without loss of moisture) by microwave energy with a single-mode rectangular wave guide, with specific attention to temperature rise, compressive strength, and the use of the maturity function was investigated experimentally and theoretically. The obtained results show that dielectric properties are relatively high and remain constant during the dormant period. After this period, the hydration reaction resumes and dielectric properties decrease rapidly. With the use of microwave heating, early-age strength increases during the first 14 days; however, during the next 14 days, early-age strength decreases slightly, until it reaches its lowest at the 28-day mark. The temperature rise as actually recorded at the center of the sample during microwave heating in our experiment consistently agreed with figures calculated by a mathematical model.     

Drying of Osmosed Cantaloupe: Effect of Polyols on Drying and Water Mobility

Cantaloupe slices were sequentially immersed in 40 and 50 °Brix sucrose solutions for 24 h each. Partial replacement of the 50 °Brix sucrose solution with one of two polyhydric alcohols (sorbitol or glycerol) at 10 or 15% (w/v) was also performed along with a 0% (w/v) polyhydric alcohol treatment and a 10% (v/v) invert sugar partial replacement of the 50 °Brix solution as a control and a reference, respectively. Solids gain (SG) and water loss (WL) were determined up to 48 h later. Conversely, the treatment with 10 and 15% (w/v) sorbitol and the reference showed a significantly higher SG and a lower WL than the control (p < 0.05). The treatments with 10 and 15% (w/v) glycerol presented a significantly lower SG and higher WL than the control (p < 0.05). Increasing concentrations of polyol led to an increase in both the WL and the SG. The osmosed cantaloupe was then dried in a hot air dryer at 60°C, where the numerical drying rate was observed to be as follows: control > 10% sorbitol > 15% sorbitol > 10% glycerol > 15% glycerol > reference, but these differences at each moisture ratio were not significantly different (p > 0.05). Page's model showed a better goodness of fit with the experimental data for all treatments than did the Henderson and Pabis model. The addition of either of the two polyhydric alcohols resulted in a decreased longitudinal relaxation time (T ₁), as monitored using nuclear magnetic resonance (NMR), indicating the decreased mobility of water molecules. Among all treatments evaluated, the sensory analysis derived acceptance scores for the product treated with 10% (w/v) sorbitol were not significantly different from that of the reference (p > 0.05). This may due to the ability of invert sugar and polyols to act as a humectant.