•Liquid egg-yolk is an alternative ingredient for EPN production in monoxenic liquid culture.•The IJ yield production is doubled by adding liquid egg-yolk to the culture medium.•In vitro cultured ...Steinernema carpocapsae JAP1 maintain his virulence against Galleria mellonella.
Dehydrated egg yolk is usually incorporated as a powder into the liquid medium to supply protein for entomopathogenic nematodes (EPNs) culture. This study aimed to evaluate the yield production of Steinernema carpocapsae strain JAP1 cultured in 10 mL of the P2 medium with fresh liquid egg-yolk (P2-LEY) and powdered egg-yolk (P2-PEY) into orbitally shaken bottles at 130 rpm and 28 °C for 16 days. The nematode inoculum was transferred from the surface layer of a solid culture with 21.5 % of infective juveniles (IJs), to achieve an initial concentration of 2000 ± 200 IJs·mL−1. Using P2-LEY, the maximum concentration was improved to 265 000 nematodes·mL−1 with 60% of the population in the IJ stage. In addition, the mortality of Galleria mellonella due to confrontation with these juveniles was 61%, which shows a non-statistical difference with the virulence of IJs in vivo reared in host insects. We concluded that LEY is a suitable component for the liquid culture mass production of nematodes. These results are discussed in light of information on the nutritional differences between LEY and PEY and their emulsifier attributes.
Native corn and potato starches were mixed in different proportions. Blends presented similar values to potato starch at onset temperature and at ending temperature to corn starch. CS20PS80 blend had ...the highest values for hardness between blends due to the formation of a three-dimensional network with corn starch granules that act as composite material. Some blends exhibited higher recovery viscosity than native starches, possibly due to interactions. Gelatinization temperature, swelling power, phosphorous content, granule size, and x-ray pattern played an important role in the resulting properties, however, the amylose content did not show influence due to both starches having a similar content.
Luffa fibers were evaluated as a reinforcement material in poly-hydroxy-butyrate matrix composites. The treatments consisted of varying the incorporation percentage of mercerized and non-mercerized ...luffa fibers in a poly-hydroxybutyrate (PHB) matrix (5%, 10%, and 20% w/v). Composites made with PHB and reinforced with luffa fibers (treated and non-treated) were mechanically evaluated (tensile strength, Young’s modulus, and percentage of elongation at break), the surface morphology was described by using scanning electronic microscopy, and the degradability behavior of composites was obtained. According to the results, mechanical properties decreased when the percentage of fibers increased and no significant effects were observed when compared with mercerized fiber composites. Degradability tests demonstrated that the weight loss increased with increased fiber content in composites, independent of the applied pretreatments. Microscopy images exhibited that mercerization improved the fiber incorporation into the polymeric matrix, diminishing the “pull out” effect; the above-mentioned result was supported by using the Fourier-transform infrared spectroscopy technique, observing the reduction of lignin and hemicellulose peaks in mercerized fibers. Based on the composite mechanical performance and degradability behavior, it was concluded that this material could be used in the packaging sector as biodegradable secondary packaging material.
The structural properties of blends of waxy corn starch and potato starch at different proportions were evaluated at 20% solids content. The results from differential scanning calorimetry, wide-angle ...X-ray scattering, and small-angle X-ray scattering of the starch blends indicated that each starch gelatinized completely and independently. The setback viscosity values were higher in the blends compared with native starches, which suggested that the granular interactions had an important effect. The presence of waxy corn starch granules could have reinforced the network formed by amylose leached from potato starch granules. The intrinsic characteristics of waxy corn starch and potato starch determined the type of granular and molecular interactions that could be carried out during the processes of gelatinization and gel formation in starch blends.
•Proximate composition and minerals were determined in 30 cultivars of sweet potato.•Influences of the island and cycle of cultivation on the minerals were observed.•High contributions of vitamin C, ...phenolics, K, Mg, Ca, Mn, Fe and Cu from sweet potato.•MDS technique can classify cultivars by geographical location and maturation cycle.
Proximate composition (moisture, protein, starch, amylose, total dietary fibre, Brix degree, fat, ash, ascorbic acid, phenolic compounds, acidity and pH), minerals (Na, K, Ca, Mg) and trace elements (Fe, Cu, Mn, Zn) were determined in 30 cultivars of sweet potato from the Canary Islands (Spain). There were significant differences between the sweet potato cultivars for all the parameters studied; in addition, both the island of production and the cultivation cycle showed a noteworthy influence on the mineral and trace element composition of the tubers. It is worth mentioning that the consumption of sweet potatoes contributes relatively high intake levels of vitamin C, phenolic compounds and mineral and trace elements (K, Mg, Ca, Mn, Fe and Cu). Application of multidimensional scaling (MDS) correctly classified the sweet potato cultivars according to the island of production and maturation cycle.
•Water vapour permeability values decreased in films with cellulose nanoparticle (CN).•Starch films (chayote and potato) with CN had the highest tensile strength.•Melting temperature of starch films ...increased for addition of CN.•Reduction in ΔH value indicated no ordering in double helices of the polysaccharides.
The aim of this study was to characterize chayotextle starch films reinforced with cellulose (C) and cellulose nanoparticle (CN) (at concentrations of 0.3%, 0.5%, 0.8% and 1.2%), using thermal, mechanical, physicochemical, permeability, and water solubility tests. C was acid-treated to obtain CN. The films were prepared by casting; potato starch and C were used as the control. The solubility of the starch films decreased with the addition of C and CN compared with its respective film without C and CN. No statistical difference (α=0.05) was found in the films added with different concentrations of C and CN. In general, the mechanical properties were improved with the addition of C and CN, and higher values of tensile strength and elastic modulus were determined in the films reinforced with CN. The melting temperature and enthalpy increased with the addition of C and CN, and the values of both thermal parameters were higher in the films with CN than with C; the enthalpy value of the film decreased when the concentration of C or CN increased in the composite. Low concentration of C and CN is better distributed in the matrix film. The addition of C and CN in the starch films improved some mechanical, barrier, and functional properties.
Composites of polyvinyl alcohol, native banana starch, oxidized banana starch using glycerol like plasticizer, were studied by mechanical tests (MT), scanning electronic microscopy (SEM), ...differential scanning calorimetry (DSC) and solubility in water. The oxidized banana starch showed higher level of carboxyl groups than of carbonyl groups. Composites of native banana starch/polyvinyl alcohol and oxidized banana starch/polyvinyl alcohol showed irregularities, indicating incomplete dispersion of the polymers. However, the film elaborated with the blend oxidized banana starch/polyvinyl alcohol showed the highest mechanical properties and the melting temperature of the first transition, as well as the lowest water vapor permeability, indicating higher interaction between both polymers. The composite oxidized banana starch/polyvinyl alcohol showed higher water solubility than the one of its counterpart with native banana starch at 25°C, and similar values were obtained for both films at 60°C. The oxidation of banana starch in order to elaborate a film blended with polyvinyl alcohol improved some mechanical and barrier properties, and this composite could be used for specific applications in the packing of food.
The viscoelasticity at 25 °C and microstructure of 0.02–0.07 wt% of low acyl gellan aqueous media were investigated for ratios of Ca2+ to gellan in the range of 0–38.8, using small amplitude ...oscillatory shear rheometry and confocal laser scanning microscopy (CLSM), respectively. The total ionic concentration (CT = γ CP + CS, being CP and CS the gellan and calcium concentrations, respectively, and γ the mean activity coefficient) of the systems was found to be the triggering and critical factor for the gelation and elasticity of gellan systems. The gel point (Tgel) and storage moduli (G′) increased upon increasing CT. However, G′ showed a maximum for CT = 9.3 ± 1.2 meq/L, followed by a progressive reduction as CT increased; this was primarily due to further addition of calcium, as CP had a low contribution to CT of the systems. CLSM demonstrated that the level of counter-ions was enough to induce the formation of a network, whose connection depended on CP and whose reinforcement was ion dependent. Therefore, even at very low levels of gellan, it is possible to create a wide spectrum of viscoelastic behaviors going from structured liquids to strong gels through the specific combinations of gellan and cation concentrations.
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The sol–gel transition temperatures of 0.1–1.0% high acyl gellan (HAG) with 0–200 mM NaCl or KCl and 0–20 mM CaCl2 or MgCl2 were determined using rheological measurements. Transition temperatures for ...monovalent cations, Na+ and K+, in the range of 50–80 °C were not significantly different (p > 0.5). Absence of thermal hysteresis was the salient feature. However, thermal hysteresis (∼4.4 °C) was observed for 0.1% HAG without added salt, but disappeared on increasing HAG and counterion concentrations. Few concentrations of HAG and added monovalent and divalent cations showed thermal hysteresis not higher than 2.5 °C. Transition temperatures for divalent cations were similar to those for monovalent cations although for considerably lower concentrations of Ca2+ or Mg2+. Increasing concentrations of monovalent and divalent counterions give rise to higher transition temperatures but not to higher storage moduli. This was interpreted as a lack of cross-link formation in the three-dimensional network structure of the gels. A single sol–gel transition diagram for monovalent cations is proposed, in which different zones associated with the presence of ordered and disordered conformations serve to identify the conditions in which HAG can exist in aqueous media.
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► The divalent cations are more effective in promoting transitions than the monovalent cations. ► Lack of thermal hysteresis was the salient feature. ► Increasing the total ionic strength of monovalent or divalent cations promotes ordered and more stable structures. ► A transition diagram for monovalent cations makes it possible to identify which conditions give solutions and which give gels.
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