Utilization of partially ripe mangoes for freezing preservation by impregnation of mango juice and sugars

Frozen mango is texturally damaged due to formation of ice crystals during freezing preservation. The objective of this investigation was to use partially ripe mango as an alternative for ripe mango. Based on its stronger structure, partially ripe mango could better withstand texture damage by ice crystals. Its flavor and color could be enhanced by impregnation of mango juice and sugars (natural flavor) into the mango matrix. This investigation found that calcium carbide incubation for two days helped prepare the mango at a partially ripe state. Vacuum infusion was more effective than natural mass diffusion in incorporation of mango juice-sugar mixture (shorter soaking time (˜10 min at 74.66 kPa) and better mango quality (texture, solid content and color sensory scores ˜7-8 in a traditional 9-point hedonic scale). After freezing (air-blast, jet-impingement and cryogenic freezing) and thawing, the juice/sugar-infused mangoes were high in sensory scores (7-8) and low in drip loss (9-12 g/100g) values. They better tolerated freezing damage than did ripe mango. This proposed method can help reduce the post-harvest losses arising from the faster spoilage of more ripe mangoes. It enhances natural flavor and taste of the partially forced ripening mangoes which normally impart only color.     

X-ray absorption spectroscopies of Mg-Al-Ni hydrotalcite like compound for explaining the generation of surface acid sites

Hydrotalcite-like compound containing metal cations such as Mg²⁺, Al³⁺ and Ni²⁺ was characterized using Ni K-edge EXAFS and in situ Ni K-edge XANES techniques for clarifying its bonding environment around Ni²⁺ sites and structure changes during calcination from room temperature to 550 °C, respectively. At the fixed molar ratio of Mg/Ni/Al of 2/1/1, the results obtained from EXAFS analysis showed a slight blue shift before and after the calcination at 550 °C and a reduction in white line peak; the best fits of the two samples revealed tiny change in coordination number about 7 for Ni-O path but considerable difference for Ni-Mg(Al) path from about 4.5 to 9.5, confirming a modification from brucite like to mixed oxide structure. On the other hand, bond distances of the Ni-O and Ni-Mg paths nearly fixed at about 2.06 Å to 3.0 Å reflected stability of the cationic bond order on each plane, but partial collapse and decomposition of the interlayer formed by water molecules and anion CO ₃ ^2? after the calcination. Linear combination fit extracted from the in situ Ni K-edge XANES also confirmed the changes along with the calcination such as slow and fast decreases of brucite fraction at 150 °C and 330 °C, respectively, in corresponding to the mixed oxide fraction increases. The achieved bonding structures were also applied to explain acid-base occurrence of the hydrotalcite-like material, especially the acid sites generated by different static charges along with the bonds. The explanation was illustrated by NH₃-TPD method.     

Fed-batch optimization of recombinant <Emphasis Type="Italic">α</Emphasis>-amylase production by <Emphasis Type="Italic">Bacillus subtilis</Emphasis> using a modified Markov chain Monte Carlo technique

A modified Markov Chain Monte Carlo (MCMC) searching procedure was developed to search for an optimal set of decision variables and optimal feed rate trajectories for recombinant α-amylase expression by Bacillus subtilis ATCC 6051a. The bacterium also synthesizes proteases as undesirable products in fed-batch culture that need to be minimized. To maximize α-amylase productivity, a 14th-order fed-batch model was optimized by integrating Pontryagin’s maximum principle with the Luedeking-Piret equation. The number of iterations and simulations of the proposed searching procedure were statistically examined for accuracy and acceptability of the results. It can be concluded that the proposed searching procedure increased the parameter selection opportunity near the tail ends of redefined triangular distribution. By applying a modified MCMC searching procedure with 1,500 iterations, the predicted α-amylase productivity was improved by 18% in comparison with near-optimum experimental results. This productivity was 3.5% higher than predicted by conventional MCMC optimization.     

Photocatalytic degradation of benzene,toluene, ethylbenzene,and xylene (BTEX) using transition metal-doped titanium dioxide immobilized on fiberglass cloth

Transition metal (Fe, V and W)-doped TiO₂ was synthesized via the solvothermal technique and immobilized onto fiberglass cloth (FGC) for uses in photocatalytic decomposition of gaseous volatile organic compounds—benzene, toluene, ethylbenzene and xylene (BTEX)—under visible light. Results were compared to that of the standard commercial pure TiO₂ (P25) coated FGC. All doped samples exhibit higher visible light catalytic activity than the pure TiO₂. The V-doped sample shows the highest photocatalytic activity followed by the W- and Fe-doped samples. The UV-Vis diffuse reflectance spectra reveal that the V-doped sample has the highest visible light absorption followed by the W- and Fe-doped samples. The X-ray diffraction (XRD) patterns indicate that all doped samples contain both anatase and rutile phases with the majority (>80%) being anatase. No new peaks associated with dopant oxides can be observed, suggesting that the transition metal (TM) dopants are well mixed into the TiO₂ lattice, or are below the detection limit of the XRD. The X-ray absorption near-edge structure spectra of the Ti K-edge transition indicate that most Ti ions are in a tetravalent state with octahedral coordination, but with increased lattice distortion from Fe- to V- and W-doped samples. Our results show that the TM-doped TiO₂ were successfully synthesized and immobilized onto flexible fiberglass cloth suitable for treatment of gaseous organic pollutants under visible light.     

Chemical composition and antioxidative activity of Thai traditional fermented shrimp and krill products

Chemical composition and antioxidative activities of some Thai traditional fermented shrimp and krill products including Jaloo, Koong-Som and Kapi were studied. All products did not contain myosin heavy chain or actin, but contained a large amount of small peptides. Kapi had the highest protein content, whereas carbohydrate content varied with products. Water-soluble fraction from all products possessed DPPH and ABTS radical-scavenging activity, as well as ferric reducing antioxidant power (FRAP) in a concentration-dependent manner. At the same concentration tested, the water-soluble fraction from Kapi exhibited the highest antioxidative activity. Soluble fraction of all products showed high stability over a wide pH range (2–11) and was stable after heating at 40–100 °C for 15–60 min. Fractions from all products heated at 100 °C had increases in FRAP, suggesting the enhancement of antioxidant activity. Therefore, fermented shrimp and krill products could be used as a potential source of nutrients and natural antioxidants.     

Physicochemical characterizations and release studies of nicotine–magnesium aluminum silicate complexes

Nicotine (NCT), a volatile strongly alkaline liquid, is widely used in smoking cessation therapy for relieving addiction symptoms. Magnesium aluminum silicate (MAS) is a mixture of montmorillonite and saponite and thus may adsorb an amine drug. In this study, NCT–MAS complexes were prepared at different pHs in order to improve NCT stability and to use as drug carriers. Physicochemical properties and in vitro NCT release of the complexes were studied. The molecular interaction between NCT and MAS was investigated using FTIR and solid-state ²⁹Si NMR spectroscopy. The results indicated that the complexation of NCT and MAS was formed not only via non-ionic electrostatic interaction, hydrogen bonding and water bridging mechanisms, but also via ionic electrostatic interaction, a cation exchange mechanism that was dependent on the pH of the preparation medium. The intercalation of NCT was revealed by PXRD. DSC and TGA studies indicated that the complexes could reduce evaporation and enhance the stability of NCT at high temperature. The complexes prepared at pH 4 and 7 had higher thermal stability than the complex prepared at pH 10. The complexes presented a sustained release of NCT after a burst release in pH 6 phosphate buffer. The NCT release kinetics could be described using the particle diffusion-controlled and Higuchi's models. The findings suggest that the NCT–MAS complexes could enhance the thermal stability of NCT and have good potential for use as drug reservoirs or drug carriers in NCT delivery systems intended for sustained release.     

Effect of high‐pressure microfluidization on the structure of cassava starch granule

Microfluidization has been applied to modify starch granules. The study was conducted to investigate the effect of microfluidization on the structure and thermal properties of cassava starch–water suspension (20% w/w). The means of optical microscopy, SEM, FTIR spectroscopy, XRD, and DSC were applied to analyze the changes in microstructure, crystallinity, and thermal property. Microscopy observations revealed that native starch granules were oval, round, and truncated in shape. After the microfluidization treatment, a bigger starch granule was partially gelatinized, and a gel‐like structure was formed on a granular surface. No significant difference in XRD patterns of the samples were observed and all samples exhibited A‐type allomorph. Crystallinity decreased with the pressure. Sample treated at 150 MPa contains 17.1% crystalline glucan polymer, lower than that of native granules which have crystallinity of about 25.8%. A lower crystallinity means poor order of crystalline glucan polymer structure in starch granules. The disruption of crystalline order within the granule was also observed by FTIR measurement. Thermal analysis using DSC indicated that the microfluidization treatment brought about a significant decrease of melting enthalpy. The gelatinization enthalpy was 12.0 and 3.0 J/g for the native sample and samples treated under the 150 MPa, respectively. The results indicate that high‐pressure microfluidization process induced the gelatinization of cassava starch, which is evaluated by a percentage of the degree of gelatinization, due to a pronounced decrease with increasing microfluidizing pressure.     

Effects of Flavourzyme on Yield and Some Biological Activities of Mungoong, an Extract Paste from the Cephalothorax of White Shrimp

ABSTRACT:  The use of Flavourzyme as a processing aid for the production of Mungoong, an extract paste from the cephalothorax of white shrimp, and its effect on biological activities were investigated. Flavourzyme increased the yield of Mungoong. Mungoong prepared from raw cephalothorax with the addition of 0.15% or 0.30% (w/w) Flavourzyme showed higher yields than those prepared from the cooked counterpart with a higher formal content and nitrogen solubility index when the same levels of Flavourzyme were used ( P  < 0.05). Higher ammonia and amino nitrogen contents were also observed in Mungoong prepared with the aid of Flavourzyme, particularly for the raw cephalothorax ( P  < 0.05). All Mungoong contained protein as the major constituent. For antioxidative activity, Mungoong prepared from raw cephalothorax with 0.15% Flavourzyme (Mungoong RF 15) exhibited the highest antioxidative activity as evidenced by the highest 2,2-diphenyl-1-picryl hydrazyl and 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging activities as well as ferric reducing antioxidant power, compared with other samples. Additionally, angiotensin I converting enzyme inhibitory activity was greater in Mungoong produced with the aid of Flavourzyme, regardless of processes used ( P  < 0.05).     

Antioxidative activity of Mungoong,an extract paste,from the cephalothorax of white shrimp (Litopenaeus vannamei)

The antioxidative activity of Mungoong, an extract paste, from the cephalothorax of white shrimp (Litopenaeus vannamei) was studied. Extraction media were shown to affect the antioxidative activity and properties of resulting extracts from Mungoong. Distilled water exhibited the highest efficacy in extracting the antioxidants from Mungoong, as evidenced by the highest ABTS (2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) and DPPH (2,2-diphenyl-1-picryl hydrazyl) radical scavenging activity as well as ferric reducing activity power (FRAP), compared with distilled water/ethanol mixture (1:1, 1:2 and 2:1) and ethanol. UV-absorbances at both 280 and 295 nm (A₂₈₀, A₂₉₅), browning intensity (A₄₂₀) and fluorescence intensity were also highest in the extract using distilled water. ABTS and DPPH radical scavenging activity and FRAP of water extract, increased linearly with increasing concentration. Good correlation between ABTS and DPPH radical scavenging activity; DPPH radical scavenging activity and FRAP; ABTS radical scavenging activity and FRAP were observed, suggesting that antioxidants in the extract, possessed the capability of scavenging the radicals together with reducing power. Antioxidants in the water extract from Mungoong showed high stability over the wide pH ranges (2–11) and temperature up to 100 °C, in which the activity of more than 80% remained. MALDI-TOF analysis revealed that water extract contained the peptides having the mass ranges of m/z 400–1000 and 4000–7000.