Effect of gelatinisation on slowly digestible starch and resistant starch of heat-moisture treated and chemically modified canna starches

The effects of gelatinisation on slowly digestible (SDS) and resistant starch (RS) of native and modified canna starches were investigated. Starch slurries (10% w/w) were gelatinised at 100 °C for 5, 10, 20 and 40 min using a rapid visco analyzer (RVA). Significant change in the degree of gelatinisation (DG) values of all starch samples was observed during the initial 10 min of gelatinisation; after that the DG values increased gradually with gelatinisation time. The RS contents in all gelatinised starches decreased with increasing gelatinisation time, while the SDS values fluctuated. Chemical modification affected DG values as well as RS/SDS contents. The RS contents in 10% (w/w) acetylated, hydroxypropylated, octenyl succinylated and cross-linked canna starches gelatinised at 100 °C for 40 min were 26.6%, 32.0%, 45.3% and 19.8%, respectively, which were higher than that of the native starch (12.4%). Canna starch modified by crosslinking had the highest SDS content when gelatinised for 20-40 min. Modification of canna starch by heat-moisture treatment resulted in a lower content of RS for all treated samples. However, the Vt-HMT25 (canna starch containing moisture content of 25% during heat treatment) when gelatinised for 5-20 min contained a higher amount of SDS, compared to unmodified starch. The most effective modification method for RS and SDS formation was octenyl succinylation, where the sum of RS and SDS approached that of Novelose260.     

Electrospinning of PAN/DMF/H2O containing TiO2 and photocatalytic activity of their webs

Polyacrylonitrile (PAN) nanofiber webs containing titanium dioxide (TiO₂) were prepared via electrospinning. Either dimethyl formamide (DMF) or its mixture with small amount of water (3 and 5%w/w.) was employed to prepare 5%w/w.PAN/DMF or PAN/DMF/H₂O solution, respectively. Introducing non-solvent water in PAN/DMF/H₂O solution was attempted to induce phase separation, which may lead to formation of porous structure on nanofibers surface. Different amounts of TiO₂ (1 to 3 wt.%) were added into PAN/DMF/(H₂O) solutions and then electrospun into nanofiber webs. From SEM, nanofibers possessed rough surfaces and had averaged diameters in ranges of 170–430 nm., showing tendency to increase with amount of TiO₂ and water. Porous structure on fiber surfaces was not clearly observed, which was suspected to be due to insufficient amount of water employed. Less homogeneity in polymer solution due to presence of TiO₂ disfavored increasing water content higher than 5%w/w. EDS data confirmed presence of TiO₂ in electrospun webs. From photocatalysis evaluation, webs containing 2 and 3 wt.% TiO₂ showed good photocatalytic activity such that 80 percent of 10 ppm. methylene blue degraded in 24 hours. Slight increase in photocatalytic activity was observed in webs obtained from PAN/DMF/H₂O solutions.     

Effects of Gelatinization and Gel Storage Conditions on the Formation of Canna Resistant Starch

The effects of gelatinization and gel storage conditions on the formation of canna resistant starch (RS) were investigated. Starch slurries (10%, dwb) were autoclaved at 121?°C for 30, 60, and 120?min. The gels obtained were subsequently stored at different temperatures (4?°C, 30?°C, and 100?°C) and times (0, 1, 3, 5, and 7?days). Analyses of the RS content in gelatinized starch samples in comparison with that in granular starch showed that the RS fraction in granular starch was very high (97.3% w/w); however, nearly all of the RS was thermally unstable, as indicated by a great reduction in RS content (to 1.9% w/w) after cooking at 100?°C for 20?min. The RS contents in gelatinized starch samples were 12.0?C15.9% w/w, which were reduced to 7.9?C10.8% w/w after cooking. Storage of gels resulted in a significant increase in the amount of the thermally stable RS fraction, e.g., a thermally stable RS content of 16.8% w/w was found in the gel sample gelatinized for 120?min and stored at 4?°C for 3?days. This indicated that the ordered structures of the RS portion were tightened under the storage conditions. The gelatinization temperature of canna starch was 72.2?°C, whereas the RS products exhibited two melting temperature ranges, 51.1?C76.3?°C and 163.1?C165.1?°C, indicating that the newly formed crystals were very strong.     

Changing in processing yield and physical properties of frozen white shrimp (Penaeus vannamei) treated with lysine and sodium bicarbonate

The objective of this research was to investigate the phosphate alternative use of natural compound, lysine with sodium bicarbonate (NaHCO₃), at low concentration for freezing of white shrimp (Penaeus vannamei). Shrimp were treated with lysine, NaHCO₃ and lysine with NaHCO₃ at various concentrations and frozen in an air‐blast freezer. Thawing yield, cooking yield, colour, texture and nanostructure of the sample were studied compared to the control (nontreated sample) and sodium tri‐polyphosphate (STPP) treated one. Use of lysine/NaHCO₃ each at 1% (w/v) could improve water holding capacity (WHC) of the frozen shrimp, increasing cooking yield to 100.45% (w/w), comparable to the 101.73% (w/w) of STPP‐treated sample. The colour of the noncook‐thawed shrimp was also improved. Microstructure and lipid oxidation of the treated samples were also studied. The combination of lysine and NaHCO₃ indicated high potential use as phosphate alternative for frozen white shrimps.     

Glycerol-enhancing heat-moisture treatment of A-type rice and cassava starches and B-type potato and canna starches

Effects of glycerol on the heat-moisture treatment (HMT) of A-type rice and cassava starches and B-type potato and canna starches were investigated. Starch samples were soaked in water or glycerol solution, adjusted to 25% moisture, and then subjected to HMT at 100 °C for 1, 6, and 16 h. Pasting profiles of all four starches plasticised with water clearly showed the B-type potato and canna starches were more susceptible to HMT than the A-type rice and cassava starches. The effect of HMT on the pasting properties of glycerol-plasticised samples was inconclusive; the B-type canna and A-type cassava starches were altered, but not the B-type potato and A-type rice starches, which remained comparable to the water-plasticised samples. Thus, the type of plasticiser as well as the environment surrounding the crystalline region, which is specific to each starch type, also affect the alteration of starch during HMT.     

Enrichment of rice noodles with fibre‐rich fractions derived from cassava pulp and pomelo peel

Cassava pulp and pomelo peel were evaluated for their potential as sources of dietary fibre in dried rice noodles. Noodles containing cassava pulp (1–20%) and pomelo peel (1–10%) had significantly higher cooking weight (136–166%) than the control sample (125%). Elongation of noodles containing cassava pulp (61–86%) was significantly higher than that of the control (56%) and noodles containing pomelo peel (29–49%). Total dietary fibre (TDF) content of noodles made from rice flour was 3.0%, and increased to 7.0% and 10.2% after adding 20% of cassava pulp and 10% of pomelo peel, respectively. A combination of cassava pulp and pomelo peel at a total amount of 20% resulted in an obvious increase in cooking weight, whereas tensile stress and elongation of noodles were comparable to those of the control noodle. The highest TDF content obtained was 14.4%.