The effect of UV-B irradiation on structural and functional properties of corn and potato starches and their components.

In this work, UV-B irradiation, an environmentally friendly modification method, was applied to corn and potato carbohydrates. The influence of irradiation on starch properties was compared with that observed for starch oxidation with NaClO. The changes in the structures of starch carbohydrates were investigated by X-ray diffraction (XRD), electron paramagnetic resonance (EPR) and chromatographic methods. Functional properties such as viscosity, water binding capacity and solubility as well as pasting characteristics and thermodynamic parameters of gelatinization, resulting from structural changes were determined. UV-B irradiation was found to be a milder modification method than chemical oxidation. The potato carbohydrates, especially amylose, appeared to be more susceptible to changes upon irradiation, whereas corn ones, particularly amylopectin, were more stable and their properties changed to a smaller extent. Similarly, functional properties were not significantly influenced by UV-B treatment. EPR studies revealed the mechanism of depolymerization of starch carbohydrates via formation of stable carbon-centered radicals.

Structural variations of rice starch affected by constant power microwave treatment.

Although lots of work has reported the structural variations of starch in microwave treatment, most of them are detected in the environment with non-constant microwave power and inhomogeneous heating, and the results are always in poor repeatability. In this study, the equipment with constant microwave power (CPM) and homogeneous heating was designed. And the phase transition of multi-scale structure of rice starch (30% moisture content) caused by CPM treatments with two heating modes, namely rapid microwave heating (RWH) and slow microwave heating (SWH) were investigated systematically. SEM results showed that the surface of starch granules after CPM treatment were rough and broken, and the damage caused by RWH was more distinct than that by SWH. SAXS, XRD and 13C NMR results revealed that the CPM treatment decreased the degree of crystallinity and content of double helices of starch. Moreover, the influence of RWH on the variation of starch granules was greater than that of SWH, which can be attributed to the intensive friction and collision as well as the rapid evaporation of water in RWH treatment. Specifically, it exhibited greater destruction on the linkage of starch and the internal crystalline region in RWH treatment than SWH treatment, thereby resulting in more obvious damages on the lamellar and morphological structure of rice starch. In conclusion, CPM equipment has improved the problems of uneven heating and poor experimental repeatability. After CPM treated starch, the molecular structure of starch was destroyed, which provides a useful method to modify properties of starch.

Effects of electron beam irradiation on the properties of waxy maize starch and its films.

Waxy maize starch was irradiated under different doses of radiation (2-30 kGy), and starch physicochemical properties were analysed. Films were subsequently produced from native and irradiated waxy maize starches and their properties were tested. The starch molecular weight markedly decreased with increasing irradiation dose. And the branch chain length, melting temperature, melting enthalpy, and relative crystallinity decreased slightly, especially at an irradiation dose below 15 kGy. This indicated that more α-1,6-glucosidic bonds than α-1,4-glucosidic bonds were cleaved by a low dose of irradiation; hence, more linear chains were released. Films prepared from 10 kGy irradiated waxy maize starch displayed enhanced mechanical properties and increased solubility, owing to a moderate increase in linear starch chains and a decrease in starch molecular weight, respectively. The resulting rapidly-dissolvable films from irradiated waxy maize starch have potential for use in instant food packaging.

Fabrication of smart stimuli-responsive mesoporous organosilica nano-vehicles for targeted pesticide delivery.

It is highly desirable to construct stimuli-responsive nanocarriers for improving pesticides targeting and preventing the pesticides premature release. In this work, a novel redox and α-amylase dual stimuli-responsive pesticide delivery system was established by bonding functionalized starch with biodegradable disulfide-bond-bridged mesoporous silica nanoparticles which loaded with avermectin (avermectin@MSNs-ss-starch nanoparticles). The results demonstrated that the loading capacity of avermectin@MSNs-ss-starch nanoparticles for avermectin was approximately 9.3 %. The starch attached covalently on the mesoporous silica nanoparticles could protect avermectin from photodegradation and prevent premature release of active ingredient. Meanwhile, the coated starch and disulfide-bridged structure of nanoparticles could be decomposed and consequently release of the avermectin on demand when nanoparticles were metabolized by glutathione and α-amylase in insects. The bioactivity survey confirmed that avermectin@MSNs-ss-starch nanoparticles had a longer duration in controlling Plutella xylostella larvae compared to avermectin emulsifiable concentrate. In consideration of the superior insecticidal activity and free of toxic organic solvent, this target-specific pesticide release system has promising potential in pest management.

Characterization of the physical properties of electron-beam-irradiated white rice and starch during short-term storage.

Electron-beam irradiation (EBI) is a cold sterilization technology used in the irradiation processing of food, including rice. Herein, the effects of EBI on the swelling power, color, pasting, and sensory properties of white rice after short-term storage were analyzed. Samples were electron-beam irradiated at 0, 2, 4, 6, or 8 kGy and stored at 25 °C or 37 °C for up to 75 days. Results showed that swelling power and major pasting viscosities (including peak, breakdown, and setback viscosities) at both storage temperatures decreased with increased irradiation dose. Negative correlations were also observed between the major viscosities of pasting properties and irradiation dose at both storage temperatures. During sensory evaluation, extremely low scores for rice hardness, appearance, taste, and overall acceptability were obtained for rice subjected to high EBI dose (>4 kGy). However, rice stored at 37 °C showed lower performance than rice at 25 °C in terms of the abovementioned parameters. By contrast, the sensory properties at irradiation doses between 2 and 4 kGy were better than those of the control group at both storage temperatures. All these findings indicated the potential of low-dose (<4 kGy) EBI as pretreatment for improving the quality of white rice during storage.

Effect of microwave irradiation-retrogradation treatment on the digestive and physicochemical properties of starches with different crystallinity.

The effect of microwave irradiation-retrogradation (MIR) treatment on the physicochemical properties and in vitro digestibility of corn starch (A-type crystallinity), potato starch (B-type) and chestnut starch (C-type) were evaluated. After MIR treatment, the amount of resistant starch (RS) increased and rapid digestible starch (RDS) decreased along with the retrogradation time in all three starches. The degree of retrogradation (DR) of starch was significantly positive correlated with amylose and RS content. All three starches subjected to MIR treatment exhibited a B-type crystalline structure. With the increase in retrogradation time, starch granules became more orderly. The DR was significantly positively correlated with relative crystallinity of X-ray pattern, To, ΔH of thermal properties, and the Fourier transform infrared ratio of 1047/1022 cm-1 of starch. The results indicated that MIR treatment is a good industrial method for preparing low digestive starch and retrogradation time is an important parameter for the process.

Physiological responses of Lepidium meyenii plants to ultraviolet-B radiation challenge.

BACKGROUND: Ultraviolet-B (UV-B) radiation can affect several aspects ranging from plant growth to metabolic regulation. Maca is a Brassicaceae crop native to the Andes growing in above 3500 m of altitude. Although maca has been the focus mainly due to its nutraceutical properties, it remains unknown how maca plants tolerate to harsh environments, such as strong UV-B. Here, we present the first study that reports the physiological responses of maca plants to counteract and recover to repeated acute UV-B irradiation. RESULTS: In detail, plants were daily exposed to acute UV-B irradiation followed by a recovery period under controlled conditions. The results showed that repeated acute UV-B exposures reduced biomass and photosynthetic parameters, with gradual senescence induction in exposed leaves, reduction of young leaves expansion and root growth inhibition. Negative correlation between increased UV-B and recovery was observed, with marked production of new biomass in plants treated one week or more. CONCLUSIONS: A differential UV-B response was observed: stress response was mainly controlled by a coordinated source-sink carbon allocation, while acclimation process may require UV-B-specific systemic defense response reflected on the phenotypic plasticity of maca plants. Moreover, these differential UV-B responses were also suggested by multifactorial analysis based on biometric and physiological data.

Microwave treatment regulates the free volume of rice starch.

The aim of this work was to investigate the role of microwave parameters and moisture content on the free volume (FV) changes of rice starch by positron annihilation lifetime spectroscopy analysis (PALS) and to explore the potential relationship between the changes of FV and physicochemical properties of rice starch. Microwave heating and water molecules lead to the increasing of FV of starch. However, this result is largely influenced by the plasticization of water molecule. The anti-plasticization caused by water evaporation resulting in a decrease in the size and concentration of FV during microwave heating. Significant decrease (p < 0.05) in the thickness of amorphous region of microwave-heated rice starch was found by small angle X-ray scattering (SAXS), and the glass transition temperature (Tg) and gelatinization temperature significantly increase (p < 0.05) after microwave heating. According to correlation analysis, the power intensity and heating time were correlated negatively with the lifetime of o-Ps. In addition, the changes of amorphous region and Tg of rice starch were strongly related to FV changes. These results provided a theoretical basis for further research on the directional regulation of FV and improvement the quality of starch-based food by using microwave treatment.

Effects of stearic acid and irradiation alone and in combination on properties of amylose-lipid nanomaterial from high amylose maize starch.

This study determines the effects of stearic acid and gamma irradiation, alone and in combination, on properties of amylose-lipid nanomaterials from pasted high amylose maize starch (HAMS) with and without alpha amylase hydrolysis. HAMS was incorporated with stearic acid (0, 1.5% and 5%, w/w), irradiated at 0, 30 and 60 kGy and pasted under pressure in a rheometer. Isolated materials after thermostable alpha amylase or hot water washing were freeze-dried and characterised using differential scanning calorimetry (DSC), X-ray diffraction (XRD), Atomic Force Microscopy (AFM) and Transmission Electron Microscopy (TEM). The isolated materials contain amylose-lipid complexes (ALCs) as determined by DSC and XRD. Pasting of gamma irradiated HAMS produced type I ALCs, whereas that for un-irradiated HAMS produced type II ALCs. The ALCs occurred at nanoscale with sizes ranging from 10 to 110 nm as observed with AFM and TEM. Tailor-made ALCs nanomaterials can be produced from HAMS (with and without added stearic acid).

Properties of potato starch treated with microwave radiation and enriched with mineral additives.

The paper discusses how microwave radiation and mineral additives affect selected physical and chemical properties of potato starch. Potato starch was irradiated with microwaves of 440 W or 800 W and then enriched with ions of potassium, magnesium, copper, or iron. Atomic absorption spectroscopy showed an effective incorporation of ions, while mineral saturation depended on both the microwave radiation density and the element being introduced. The data obtained prove that the microwave radiation and saturation with minerals affect the rheology and thermal characteristics of the samples under examination. Both the degree and the vector of the transformation depend on the microwave output and the mineral component introduced. Generation of radicals depends on starch degradation at high temperature while microwaves affect the number of the radicals formed. Amounts of the heat-generated radicals depend on the microwave output and the type of metal ions introduced into the starch structure.

Comparison of Conventional and Microwave Assisted Heating on Carbohydrate Content, Antioxidant Capacity and Postprandial Glycemic Response in Oat Meals.

Minimally processed cereal breakfast products from whole grain entered the market due to consumer demand of more nutritional food with more controlled sugar release. However, the subsequent processing of such products with different cooking methods in the consumer's kitchen may lead to significant differentiation of their nutritional value. Therefore, the evaluation of the impact of frequently used cooking methods on a final quality of breakfast cereals meal is needed. The present study investigates how the two different methods of heating, conventional and microwave (MW) assisted, affect the carbohydrate content, profile and resulting glycemic index of so prepared food as well as the antioxidant activity of meals. Two products available on the market-oat bran and flakes-were used. The highest starch content in fluid phase of oatmeal was detected in samples heated for 3 min with microwaves, regardless the type. The lowest starch content was obtained for 5 min MW heated flakes sample. The total content of glucose was about 1.5 times lower in bran vs. flakes oatmeal. The highest ß-glucan content in fluid fraction was also observed for bran meal but its release was independent of applied conditions.

Effect of ultrasound pretreatment on enzymolysis and physicochemical properties of corn starch.

In the paper, the effects of ultrasound on the enzymolysis properties of corn starch were investigated. The results showed that the rate of enzymolysis changed with the change of ultrasonic conditions. Ultrasound pretreatment starches reduced the time in liquefaction process, and resulted in significantly higher DE value in saccharification process. DE value was negatively correlated to PV, BV, SV, To, Tp, ΔHg, DO, DD, N-O'KI, RC, Mw and DP, respectively, and positively correlated to Mw/Mn. X-ray diffraction analysis showed that the relative crystallinity was reduced, and the starch exhibited an A-pattern. Scanning electron microscope indicated that the notch and groove appeared on the surfaces of starch granules. The polarized cross of starch becomes smaller or even disappear. It was concluded that enzymolysis efficiency of different ultrasound pretreatment to changes due to its effect not only on the physicochemical properties, but also on the structural characteristics of corn starch.

Frequency, moisture content, and temperature dependent dielectric properties of potato starch related to drying with radio-frequency/microwave energy.

To develop advanced drying methods using radio-frequency (RF) or microwave (MW) energy, dielectric properties of potato starch were determined using an open-ended coaxial-line probe and network analyzer at frequencies between 20 and 4,500 MHz, moisture contents between 15.1% and 43.1% wet basis (w.b.), and temperatures between 25 and 75 °C. The results showed that both dielectric constant (ε') and loss factor (ε″) were dependent on frequency, moisture content, and temperature. ε' decreased with increasing frequency at a given moisture content or temperature. At low moisture contents (≤25.4% w.b.) or low temperatures (≤45 °C), ε″ increased with increasing frequency. However, ε″ changed from decrease to increase with increasing frequency at high moisture contents or temperatures. At low temperatures (25-35 °C), both ε' and ε″ increased with increasing moisture content. At low moisture contents (15.1-19.5% w.b.), they increased with increasing temperature. The change trends of ε' and ε″ were different and dependent on temperature and moisture content at their high levels. The penetration depth (d p ) decreased with increasing frequency. RF treatments may provide potential large-scale industrial drying application for potato starch. This research offers useful information on dielectric properties of potato starch related to drying with electromagnetic energy.

Physicochemical and structural evaluation of alkali extracted chickpea starch as affected by γ-irradiation.

In this study, starch isolated from chickpea was exposed to gamma-irradiation at 0, 4, 8 and 12kGy doses. The irradiated starches were evaluated for their physicochemical, morphological and pasting properties. The results revealed significant (p≤0.05) reduction in apparent amylose content, swelling power, turbidity, syneresis, L (lightness) value, and pasting parameters whereas solubility and b (yellowness) value increased with increase in irradiation dose. X-ray diffraction showed C-type of crystallographic pattern. Relative crystallinity (RC) of irradiated starches was different at different irradiation doses. Prominent changes were recorded in the FT-IR spectra of irradiated starch samples with respect to intensity and shifting of major bands in specific regions. Analysis of O - H and C - H stretches, bending mode of water and glycoside bonds of irradiated starches revealed marked decrease in their absorbance intensities. Scanning electron microscopy revealed cracking and clumping of starch granules at elevated doses of gamma-irradiation. Radiation doses were negatively correlated to swelling power, pasting parameters (peak viscosity, hold viscosity, final viscosity, setback viscosity and pasting temperature), turbidity, syneresis and apparent amylose content except solubility.

Physicochemical, thermal and pasting characteristics of gamma irradiated rice starches.

Starches isolated from two recently released rice cultivars (PR 121 and PR 116) grown in sub-tropical climates of Punjab, India were subjected to gamma irradiation at 0, 2, and 10 kGy doses using a Co(60) irradiator source. Physicochemical, thermal, pasting, and morphological properties were studied. Irradiation resulted in a significant decrease in apparent amylose content, swelling power and pasting properties. Carboxyl content and solubility increased with irradiation. The granule morphology was evaluated using scanning electron microscope, particle size analyzer and light microscope. Irradiation resulted in formation of small size granules. Granules were irregular and polyhedral in shape. The granule morphology and A-type X-ray diffraction pattern were not altered by irradiation.

Effect of γ-irradiation on structure and physico-chemical properties of Amorphophallus paeoniifolius starch.

Gamma irradiation is one of the effective techniques able to alter structure and its properties of starch. In this research, the effect of modification in terms of molecular structure and physico-chemical properties of Amorphophallus paeoniifolius starch by γ-irradiation using (60)Co as γ-source at doses of 5, 10, 15, 20 and 25 kGy with dose rate 2 kGy/h was studied. Morphology of native and irradiated starches under scanning electron microscope revealed that granules are round, elliptical and polygonal in shape with smooth surfaces; no cracking or roughness was noted on irradiated starches. Amylose content, pH, swelling power of the starches and syneresis of the gelatinized starch were significantly decreased by irradiation; while carboxyl content, solubility, light transmittance and water absorption capacity of the starch granules were raised with increased dose of irradiation. Reduced pasting parameters and changes in FTIR spectrum significantly differed from each other. XRD pattern of irradiated starches showed C-type pattern with intermediate peaks of 2θ at 16.92° and 18.12°, strong peaks of 2θ at 23.05° and weak peaks of 2θ at 14.7°, displaying slight decreased in the intensity of peaks in irradiated starches. Irradiation of starches increased gelatinization temperatures and enthalpy value was measured using DSC.

Morphological, physicochemical, and viscoelastic properties of sonicated corn starch.

In the present work, different parameters of ultrasound treatment were studied for physical modification of corn starch. The results revealed that the influence of sonication strongly depends on temperature (25-65 °C) and exposure time (5-15 min), while concentration (10-20% w/w) and ultrasound amplitude (50 and 100%) have little influence on functional and rheological properties. SEM micrographs demonstrated the damage induced by ultrasound on starch granules' surface. The solubility, swelling power, and gel clarity were increased. Ultrasonication decreased the gelatinisation enthalpy and temperature range while the X-ray pattern and crystallinity remained almost unchanged, except for samples treated at onset temperature as measured by DSC. The pseudoplasticity and consistency coefficient decreased; also, apparent viscosity diminished prominently. The pasting behaviour of samples was altered without any clear change in gel strength characterised by loss factor. The results of the present work provide further insight into the mode of action of ultrasound on modifying corn starch granules.

A simple one pot purification of bacterial amylase from fermented broth based on affinity toward starch-functionalized magnetic nanoparticle.

Surface-functionalized adsorbant particles in combination with magnetic separation techniques have received considerable attention in recent years. Selective manipulation on such magnetic nanoparticles permits separation with high affinity in the presence of other suspended solids. Amylase is used extensively in food and allied industries. Purification of amylase from bacterial sources is a matter of concern because most of the industrial need for amylase is met by microbial sources. Here we report a simple, cost-effective, one-pot purification technique for bacterial amylase directly from fermented broth of Bacillus megaterium utilizing starch-coated superparamagnetic iron oxide nanoparticles (SPION). SPION was prepared by co-precipitation method and then functionalized by starch coating. The synthesized nanoparticles were characterized by transmission electron microscopy (TEM), a superconducting quantum interference device (SQUID, zeta potential, and ultraviolet-visible (UV-vis) and Fourier-transform infrared (FTIR) spectroscopy. The starch-coated nanoparticles efficiently purified amylase from bacterial fermented broth with 93.22% recovery and 12.57-fold purification. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) revealed that the molecular mass of the purified amylase was 67 kD, and native gel showed the retention of amylase activity even after purification. Optimum pH and temperature of the purified amylase were 7 and 50°C, respectively, and it was stable over a range of 20°C to 50°C. Hence, an improved one-pot bacterial amylase purification method was developed using starch-coated SPION.

Thermal and electrical properties of starch-graphene oxide nanocomposites improved by photochemical treatment.

Bionanocomposite films have been prepared by casting an aqueous suspension of acetylated starch (ST) and poly(vinyl alcohol) (PVA) loaded with graphene oxide (GO). A photochemical and reagentless method has been successfully performed to convert the GO phase into reduced graphene oxide (RGO). The nanocomposites have displayed improved thermal and electrical properties when the amount of the GO phase is increased and properly converted to RGO. The molecular-level interactions between components are mainly hydrogen-bonding type according to attenuated total reflectance-Fourier transform infrared (ATR-FTIR) and Raman spectroscopies, as well as thermogravimetric analysis (TGA). Scanning electron microscopy (SEM) has confirmed the effective mixing between the GO and the ST-PVA matrix. The thermal diffusivity and electrical resistivity of ST-GO nanocomposites have increased one order and decreased two orders of magnitude, respectively, after the photochemical treatment. These findings have confirmed the effectiveness of the proposed approach to produce starch-based nanocomposites with improved thermal and electrical properties.

Solar energy assisted starch-stabilized palladium nanoparticles and their application in C-C coupling reactions.

Present work reports a novel one step, greener protocol for the synthesis of starch-stabilized palladium nanoparticles (PdNPs) with an average particle diameter of 30-40 nm. These particles were stable and uniform in size. In present protocol, the concentrated solar energy mediated reduction of palladium chloride was achieved by using citric acid as a reducing agent and starch as a capping agent. UV-Visible spectroscopy, Transmission Electron Microscopy, Field Emission Gun-Scanning Electron Microscopy, Selected Area Electron Diffraction and Electron dispersive X-ray Spectral analysis techniques were used to characterize this starch capped PdNPs. Herein; we are reporting such combination of starch and citric acid in the synthesis of PdNPs for the first time. The catalytic activity of synthesized nanoparticles has been checked for Suzuki and Heck cross coupling reactions. The product yield was confirmed by GC. The products were confirmed using GC-MS analysis and also using GC with the help of authentic standards. Solar energy assisted starch stabilized PdNPs showed excellent activity in the C-C bond formation between aryl halides (I, Br) with phenyl boronic acid and its derivatives. In addition, the catalyst showed good activity in the Heck coupling reaction of C-C bond formation of aryl halides with aromatic alkene. The use of starch, citric acid, water and solar energy makes present protocol greener.