Properties of konjac glucomannan–whey protein isolate blend films

Edible composite packaging has been developed by blending biocomponents for specific applications, aiming to take advantage of complementary functional properties or to overcome their respective flaws. The aim of this work was to study the effect of incorporation of whey protein isolate (WPI) on the properties of konjac glucomannan (KGM) based films. Five aqueous solutions of KGM and/or WPI were prepared by casting and solvent evaporation of 1:0, 0.8:3.4, 0.6:3.6, 0.4:3.8 and 0:4.2 g KGM:g WPI/100 g solution. Glycerol (Gly) was used as a plasticizer at 1.5 and 1.8 g/100 g solution. The result showed that incorporated WPI proportionally increased transparency of KGM-based films. An increase in proportion of WPI resulted in decreased tensile strength and elastic modulus as well as improved flexibility. The incorporation of WPI into the KGM matrix led to an increase in water insolubility which enhanced product integrity and water resistance. Nevertheless, WPI did not improve water vapor barrier of KGM–WPI films. WPI and blend film with the highest concentration of WPI could be heat sealed at 175 °C. Overall, the range of Gly in this study did not apparently affect properties of the films.     

Microencapsulation of bioactive compounds from mulberry (Morus alba L.) leaf extracts by protein–polysaccharide interactions

Mulberry leaf extracts were generated using four concentrations of ethanol (50%, 60%, 70%, and 95% v/v). A 60% ethanolic mulberry leaf extract (60E) yielded a high total phenolic content (TPC) and antioxidant activity using 1, 1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical scavenging and a ferric reducing antioxidant power (FRAP) assay. Coating materials were derived using a combination of soy protein isolates (SPI) and low methoxyl (LM) pectin in a 1:1 ratio. The effect of various parameters on microencapsulation, such as pH (3.5, 4.0, and 4.5) and the concentration of coating materials (2.5, 5.0 and 7.5% w/v), was studied. Microcapsules produced using 60E as a core material at pH 4.0 with 7.5% of coating material showed a high encapsulation yield, encapsulation efficiency, TPC and antioxidant activity.     

Microencapsulation of Kaffir Lime Oil and Its Functional Properties

This paper describes the effects of spray drying temperature and wall materials on functional properties of kaffir lime oil microcapsules. The effects of spray drying were studied at inlet air temperatures at 160, 180, and 200°C. Two coating materials (konjac glucomannan and gum arabic) were employed in this study. The results indicate that kaffir lime oil had antibacterial activity against all tested pathogens and was able to inhibit Vibrio cholerae comparable to a standard antibiotic. The combination of konjac glucomannan and gum arabic (KGM+GA) can enhance the yield and retention of total oil in the microcapsules more than using konjac glucomannan alone as a wall material. Increasing inlet air temperature resulted in a decrease of antibacterial activity and amount of bioactive volatile compounds. Physical and chemical properties of the microcapsules did not differ significantly (p > 0.05) in terms of process yield, a _w , moisture content, efficiency in retention of total, surface and inner oil, water solubility index, and color except at inlet air temperature of 200°C. However, it was found that the kaffir lime oil microcapsules from KGM+GA produced at inlet temperature of 180°C had the best functional properties in terms of antibacterial activity and efficiency of retention of total encapsulated oil.     

Studies of Physical State of Water in Maize from Northeast China (cv. Huangmo 417) During Drying at Subzero Temperatures

In northeastern provinces of China, maize is one of the main sources of income in agriculture. After harvest, the grain is kept under subzero conditions for 3-4 months. Studies have been undertaken to assess the feasibility of drying at subzero temperatures during storage. Using a combination of NMR and MRI enabled a better understanding of physical states of water in the cv. Huangmo 417 during drying at subzero temperatures. The studies showed two water components with different relaxation times (long and short T₁) that were found when temperature was lowered from +25 to -30°C. T₁ was a minimum when the temperature was reduced to -20°C. T₂ was found to be much shorter than T₁. This was an indication that water mobility was decreasing at the same time as the temperature. The results from MRI revealed the location of frozen water in different areas of the maize kernel during subzero drying. This approach to characterizing the states of water in maize under subzero conditions will assist in devising drying strategies for northeastern China.     

Effect of invert sugar on the drying kinetics and water mobility of osmosed‐air dried cantaloupe

Effect of partially replacing sucrose with invert sugar on drying kinetics of osmosed cantaloupe was evaluated using four levels of invert sugar (0, 5, 10 and 15% (v/v)) to partially replace sucrose syrup at 50 °Brix. The osmosed samples were then dried at 60 °C. The osmosed cantaloupe without invert sugar exhibited the fastest drying rate. The drying rate decreased with increasing amounts of invert sugar. An increase in the degree of water binding to invert sugar is the most likely explanation for this effect and is supported by the observed decrease in the NMR relaxation time. The use of invert sugar could reduce water activity of final product but not significantly improve overall appearance. Six different mathematical models were tested for their goodness of fit with experimental data. Modified Henderson and Pabis model was found to give the best fit and was able to predict the drying time accurately.     

Comparative Study of Effects of Drying Methods and Storage Conditions on Aroma and Quality Attributes of Thai Jasmine Rice

This article describes the effects of various drying treatments and storage conditions on the main quality attributes of Thai jasmine rice; i.e., aroma, milling, pasting, and cooking properties. The experimental results show that drying treatments using various high temperatures (115-150°C) combined with 30 min tempering time between the pass or ambient air drying affect the composition of volatile compounds as well as the commercially accepted quality characteristics of Thai fragrant rice. High-temperature drying followed by ambient air drying can retain most of the quality attributes of Thai jasmine rice than multi-pass high-temperature drying with a tempering period between passes.     

Comparative Study of Effects of Drying Methods and Storage Conditions on Aroma and Quality Attributes of Thai Jasmine Rice

This article describes the effects of various drying treatments and storage conditions on the main quality attributes of Thai jasmine rice; i.e., aroma, milling, pasting, and cooking properties. The experimental results show that drying treatments using various high temperatures (115–150°C) combined with 30 min tempering time between the pass or ambient air drying affect the composition of volatile compounds as well as the commercially accepted quality characteristics of Thai fragrant rice. High-temperature drying followed by ambient air drying can retain most of the quality attributes of Thai jasmine rice than multi-pass high-temperature drying with a tempering period between passes.     

Drying at Sub-zero Temperatures: Case Study on In-store Drying of Grains

Drying using ambient subzero temperatures is of potential interest for thermosensitive products. Existing theoretical drying models have been used to predict the response of the system to different aeration systems. The model is based on enthalpy balances and includes water freezing and deposition of water on the surface of the commodity. It uses thermophysical properties of the commodity (i.e., maize in this study) and ambient weather data collected from northeastern China. Water within the grain is modelled as bound, free or frozen. The physical state of water under subzero temperatures has been investigated using a differential scanning calorimeter and nuclear magnetic resonance spectrometry. It has been established that the quantity of bound water was around 17%. Thermophysical properties characterizing the drying behavior of maize kernels cv. Huangmo 417, the most common variety grown in northeastern China, were determined under a wide range of moisture contents and drying temperatures. Those were: particle and bulk density, porosity, thermal conductivity, specific heat, thin layer drying, and sorption isotherms. It could be established that the thermal conductivity and specific heat were strongly dependent on temperature and relative humidity and that the sorption isotherms followed the 5-term Guggenheim-Anderson-de-Boer model. The industrial-scale in-store drying experiments in northeastern China have demonstrated the feasibility of in-store drying under subzero conditions. Advantages in terms of reduced susceptibility of maize to mould formation have been established, resulting in improved quality and financial returns to the processor.