Chureerat Puttanlek

Nano-structure of heat–moisture treated waxy and normal starches

Surface regions of untreated and heat-moisture treated (HMT) normal rice, waxy rice, normal corn, waxy corn, normal potato, and waxy potato starch granules were examined by atomic force microscopy (AFM). AFM images revealed surface roughness of untreated starch granules and protrusions with a diameter of approximately 15-90 nm. After treatment, the smooth surface region on starch granules was observed, especially in normal rice, waxy rice, and normal corn starches. A significant reduction in the size of protrusions on the surface of HMT potato starch granules was also detected. The newly formed structures may act as barriers and retard water penetration into starch granules. The blocklet model of starch granule architecture was also confirmed by the AFM images.

Anaerobic digestion of pineapple pulp and peel in a plug-flow reactor.

The objective of this research was to study the production of biogas by using pineapple pulp and peel, the by-products from fruit processing plants, in a plug-flow reactor (17.5 L total volume). The effects of feed concentration, total solids (TS) and hydraulic retention time (HRT) on degradation of the waste were investigated. The increase of pineapple pulp and peel of 2% (wt/vol) at HRT 7 d to 4% (wt/vol) at HRT 10 d showed increases in biogas production rate, biogas yield and methane yield - from 0.12 v/v-d, 0.26 m(3)/kg COD removed and 0.11 m(3)/kg COD removed, with COD removal at 64.1%, to 0.25 v/v-d, 0.43 m(3)/kg COD removed and 0.14 m(3)/kg COD removed, with COD removal at 60.41%. The methanogenic fermentation was more active in the middle and final parts of the reactor. The recirculation of fermentation effluent at 40% (vol/vol) of the working volume into the reactor could increase the biogas production rate and biogas yield up to 52% and 12%, respectively. The results showed technological potential for waste treatment of pineapple pulp and peel in a plug-flow reactor.

Quality assessment of noodles made from blends of rice flour and canna starch.

Canna starch and its derivatives (retrograded, retrograded debranched, and cross-linked) were evaluated for their suitability to be used as prebiotic sources in a rice noodle product. Twenty percent of the rice flour was replaced with these tested starches, and the noodles obtained were analyzed for morphology, cooking qualities, textural properties, and capability of producing short-chain fatty acids (SCFAs). Cross-linked canna starch could increase tensile strength and elongation of rice noodles. Total dietary fiber (TDF) content of noodles made from rice flour was 3.0% and increased to 5.1% and 7.3% when rice flour was replaced with retrograded and retrograded debranched starches, respectively. Cooking qualities and textural properties of noodles containing 20% retrograded debranched starch were mostly comparable, while the capability of producing SCFAs and butyric acid was superior to the control rice noodles; the cooked noodle strips also showed fewer tendencies to stick together.

Pasting properties of heat–moisture treated canna starches using different plasticizers during treatment

Different plasticizers (propanol, propylene glycol, glycerol, erythritol, xylitol and sorbitol) were used for plasticizing canna starch during heat-moisture treatment (HMT). Pasting properties of the modified starches were determined and compared with those of native starch and of HMT starch using water as a plasticizer. Canna starch was soaked in 5% (w/w) plasticizer solutions and adjusted to 25% moisture content before heating at 100 °C for 1h. The least change in paste viscosity was found when water was used as a plasticizer. Viscosity of the modified starches decreased as the molecular weight of plasticizers decreased. Plasticizer content in starch granules increased with decreasing molecular weight of the plasticizer, as well as with increased soaking time (from 10 min to 4 and 24h). However, pasting profiles of HMT starches prepared by soaking for 4h were comparable to those soaked for 24h, indicating that there was an effective limit of plasticizers. The plasticizer content in starch granules played a greater role in HMT than the number of hydroxyl groups.

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

Summary 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.

Concentration of plasticizers applied during heat–moisture treatment affects properties of the modified canna starch

Effects of the concentration of plasticizers applied during heat-moisture treatment (HMT) on the properties of canna starch were investigated. The modified starches were prepared by soaking starch in 0 (water), 1, 3, 5, 10, 20 and 30% w/w glycerol or sorbitol solution for 24h and adjusting the moisture content to 25% before HMT (100°C, 1h). Changes in the pasting profiles of heat-moisture treated starches were more obvious when glycerol solutions were used instead of water. An increase in the concentration of glycerol solution from 1% to 5% resulted in a progressive decrease in paste viscosity; paste viscosity then increased as the glycerol concentration rose from 10 to 30%. A similar trend was observed when sorbitol was used as a plasticizer, but with a lesser effect. A scheme for arrangements of the molecular structure of starch during the process of HMT was suggested.