Effects of Annealing and Concentration of Calcium Salts on Thermal and Rheological Properties of Maize Starch During an Ecological Nixtamalization Process

The objective of the present work was to study the effect of annealing and concentration of Ca(OH)₂ (lime) and calcium salts on the thermal and rheological properties of maize starch during an ecological nixtamalization process. Thermal and rheological properties of maize starch changed during the ecological nixtamalization process because of three main causes: the annealing phenomenon, type of calcium salt, and calcium salt concentration. In all treatments thermal properties (T_o, T_p, and T_f) of nixtamal starch increased owing to the annealing process, whereas the type of salt or lime increased thermal properties and decreased pasting properties in this order: CaCl₂ > CaSO₄ > Ca(OH)₂ ≈ CaCO₃. This behavior was because of the dissociation of each salt or lime in water. Anions (OH⁻) can penetrate much more easily into the starch granule and start the gelatinization process by rupturing hydrogen bonds. Additionally, amylose‐lipid complexes were formed during the nixtamalization processes, as indicated by an increasing peak at 4.5 Å in X‐ray diffraction patterns.     

Afforestation trials with Prosopis chilensis (Mol.) Stuntz and Prosopis flexuosa D.C. in the Dry Chaco, Argentina

In implantation trials carried out with Prosopis chilensis and Prosopis flexuosa, the following variables were considered: implantation time (December and March), implantation technique (direct seeding and seedling transplantation) and age of the seedlings at the time of transplantation (60, 105 and 150 days). Survival was evaluated for more than 9 months after implantation and trials were repeated in 3 consecutive years.

Results from both species were similar and they show that survival after transplantation was higher (60–80%) than from direct seeding (35–45%). Survival from transplantation was independent of the size and age of the seedlings and it was less affected by climatic conditions than direct field sowing. Survival from direct seeding was higher in March than in December. The best time for either implantation alternative would be the end of the summer or beginning of fall, when climatic conditions increase the probability of seedling survival.     

Comparison on the effect of high-methoxyl pectin or soybean-soluble polysaccharide on the stability of sodium caseinate-stabilized oil/water emulsions

The interactions of high-methoxyl pectin (HMP) and soybean-soluble polysaccharide (SSPS) with sodium caseinate-stabilized emulsions were investigated using a multitechnique approach, including dynamic light scattering (DLS), electrophoretic mobility measurements, transmission diffusing wave spectroscopy (DWS), and ultrasonic spectroscopy (US). At pH 6.8, both polysaccharides are negatively charged and did not adsorb onto caseinate-coated droplets due to electrostatic repulsion; however, SSPS showed a different behavior compared to HMP in the turbidity parameter 1/l* and sound attenuation parameters measured by DWS and US, respectively. The present study brought the first evidence of the stabilization effect of SSPS in acidified sodium caseinate-emulsions. While destabilization occurred at low polysaccharide concentrations, probably via bridging flocculation, acid-induced aggregation of the oil droplet was completely prevented by 0.2% SSPS or HMP. However, the interaction behavior of SSPS during acidification was different from that of HMP. This was demonstrated by the different development of the parameter 1/l*, droplet sizes, sound attenuation, and velocity.     

Genetic and functional leaf traits variability of Quercus laurina along an oak diversity gradient in Mexico

The ecological literature has documented the effects of plant hybridization on phenotypic variation, and dominant, intermediate, or novel morphological, chemical and physiological traits in hybrids. It is important to understand the ecological consequences of hybridization by evaluating their impact on phenotypic expression of functional traits. We evaluated the relationship between genetic diversity of Quercus laurina and functional foliar traits along an oak diversity gradient. We selected five study sites that represent an oak diversity gradient where Q. laurina is present. Using chloroplast and nuclear microsatellites, we evaluated genetic diversity, measured functional foliar traits of Q. laurina in each site and assessed the effects of local climate variables on the oak community and functional traits. We found a greater abundance of Q. laurina in all study sites. We did not find a relationship between the number of accompanying red oak species and the population genetic diversity in Q. laurina, but higher genetic diversity was found in all study sites in comparison with European oak species. Sites with more oak species had more variation of foliar functional traits. Our results do not support the hypothesis that predicts higher levels of genetic diversity of Q. laurina in communities with greater oak diversity from the same section, but we demonstrated an increase in the foliar functional traits of Q. laurina associated with oak richness and climate variables. We highlight the need to consider environmental and ecological variables linkages as regulatory mechanisms of the phenotypic plasticity expressed in changes of some functional attributes of oaks.

     

Optimization of experimental infection protocols for the estimation of genetic parameters of resistance to White Spot Syndrome Virus (WSSV) in Penaeus (Litopenaeus) vannamei

Two infection protocols, individual oral (IO) and waterborne infection (WB), were evaluated to challenge Penaeus (Litopenaeus) vannamei with White Spot Syndrome Virus (WSSV). Five different batches of full and half-sib families were infected experimentally and tested for growth performance under commercial growth conditions. The genetic variance for WSSV resistance was estimated using a linear sire-dam repeatability model that considers test-day survival as the dependent variable. The heritability estimates using the IO protocol ranged from 0.01 ± 0.00 to 0.02 ± 0.01, whereas the heritability estimates using the WB infection protocol were not significantly different from zero. The genetic correlations measured as the product moment correlation between full-sib family breeding values for resistance to WSSV and harvest body weight in ponds were unfavourable in three of the five batches and favourable in one of them. The dosage of WSSV was better controlled with IO oral infection than with other methods, with all animals being exposed to approximately the same risk of infection at the same time. This should improve the accuracy of the genetic parameters and hence improve the accuracy of the breeding values. It should, however, be noted that once the outbreak was established and the mortalities began, the shape and the magnitude of the slope of the mortality curves showed little difference in the infection pattern between batches irrespective of the dosage and infection protocol, and in most of the cases the cumulative mortality was greater than 80%. The main reason for this is probably the high densities of animals in the tanks needed for the genetic evaluations.     

Diet trials on tehuelche scallop Aequipecten tehuelchus (d'Orb) larvae

Laboratory spawned one week old veliger larvaeof the tehuelche scallop, Aequipectentehuelchus (D'Orb., 1846), were reared topedivelger stage under three different dietaryregimes in order to determine the best algalcombination under standard hatchery conditions.Veligers were cultured at mean densities of 2.7larvae/ml. Larval growth and survival wereassessed on larvae fed the following dietarytreatments: (1) Isochrysis galbana(T-Iso)+ Chaetoceros calcitrans, (2)Pavlova lutheri + C calcitrans, and (3)P. lutheri + I. galbana T-Iso +Ch. calcitrans. The highest growth rateswere detected on larvae fed diets includingP. lutheri.     

Effects of Pre-Stratification Storage Conditions on Black Walnut Seed Post-Stratification Germination Capacity

The objective of this work was to quantify changes in the germination capacity of Juglans nigra seeds following storage and then artificial stratification. Seeds were stored at 5 and –20 °C under 5% and 14% internal moisture content (IMC) for 0, 8, 10, and 12 months under conditions with oxygen or under vacuum. Germination percentage (GP) was affected by storage temperature, IMC, and storage period. Seeds stored with 5% IMC succeeded in germinating regardless of the temperature. Seeds stored with 14% IMC did not germinate (–20 °C) or germinated during storage (5 °C). The GP was reduced with the time of storage in seeds at –20 °C and 5% IMC and this effect was avoided in storage under vacuum. In conclusion, the germination capacity of black walnut seeds did not change for up to 12 months at low above-zero temperature and low IMC (5 °C, 5% IMC), being the most cost-effective alternative for long-term storage of black walnut seeds in commercial nurseries. Vacuum storage avoided the decrease of around 50% in average germination capacity of seeds stored for a year at –20 °C.