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Influence of Pacific Ocean multidecadal variability on the distributional properties of hydrological variables in north-central Chile.

Autores:

Núñez, J., Rivera, D., Oyarzún, R., & Arumí, J.

Resumen:

This paper addresses the relationship between multitemporal variability and regime shifts in the Pacific Decadal Oscillation and El Niño Southern Oscillation, with precipitation and streamflows in Andean watersheds of the north-central region of Chile. In addition, an analysis of the effect of a regime shift displayed by annual streamflow records on their distributional properties is performed. By applying empirical fluctuation processes to monthly standardized PDO, Niño 3.4, precipitation and streamflow time series, the occurrence of a regime shift in the streamflow series, consistent with that for PDO, but highly dependent on the latitude of particular watersheds, is shown. No regime shift is detected for the precipitation time series. Using the ensemble Empirical Mode Decomposition procedure on all series, a relationship between climatic indices and hydrological variables in two main modes is determined: the former associated with a mean period of quasi 1.5–3 years related to interannual variability, and the latter with a mean period of quasi 30–35 years, related to decadal low frequency variability. Using the regional frequency analysis based on the L-moments procedure, it is found that the distributional properties of streamflow records are influenced by the phases of the PDO, with changes that affect the mean, L-CV, L-skewness and L-kurtosis in three identified homogeneous regions. The importance of incorporating low-frequency climate variability for distributional analysis and the implications of these results for water resources management and planning in north-central Chile and similar areas is discussed.

Año: 2013

Palabras claves: Climate variability; Distributional analysis; L-moments; Pacific Decadal Oscillation; Empirical Mode Decomposition.

Referencia APA: Núñez, J., Rivera, D., Oyarzún, R., & Arumí, J. (2013). Influence of Pacific Ocean multidecadal variability on the distributional properties of hydrological variables in north-central Chile. Journal Of Hydrology, 501, 227-240.

Long-term monitoring of mammals in the face of biotic and abiotic influences at a semiarid site in north-central Chile.

Autores:

Kelt, D., Meserve, P., Gutiérrez, J., Milstead, W., & Previtali, M.

Resumen:

The data set covers a 16-year period (1989–2005) of monthly small-mammal surveys and associated habitat and environmental data. Small mammals are trapped every month on all experimental plots, and both ephemeral and perennial plant cover and soil seed bank composition are measured at regular intervals. Rainfall is recorded and compiled annually (through 1998) or monthly; information on captured small mammals and on all vegetative and rainfall data is contained in associated files. These data have been applied to diverse population- and community-level analyses and remain useful for investigations of population dynamics, species interactions, and the relative influence of biotic and abiotic factors. Sampling is ongoing, and data will be added over time.

Año: 2013

Palabras claves: Biotic vs. abiotic interactions; climate; competition; ENSO; ephemeral plant cover; LTREB data; predation; semiarid ecosystem; shrub cover; small mammals.

Referencia APA: Kelt, D., Meserve, P., Gutiérrez, J., Milstead, W., & Previtali, M. (2013). Long-term monitoring of mammals in the face of biotic and abiotic influences at a semiarid site in north-central Chile. Ecology, 94(4), 977-977.

Osmotic dehydration under high hydrostatic pressure: Effects on antioxidant activity, total phenolics compounds, vitamin C and colour of strawberry (Fragaria vesca).

Autores:

Nuñez-Mancilla, Y., Pérez-Won, M., Uribe, E., Vega-Gálvez, A., & Di Scala, K.

Resumen:

Simultaneous application of osmotic dehydration under high hydrostatic pressure conditions of strawberries was studied with the purpose of analyzing the effect of the combined process on the antioxidant capacity, phenolic compounds, colour and vitamin C of strawberries during refrigerated storage. The osmotic solution was prepared using commercial sugar at 40 °Brix. Samples were pressurized between 100 and 500 MPa for 10 min. The radical scavenging activity showed higher antioxidant activity at 400 MPa rather than at low pressure (100, 200 and 300 MPa). The total phenolic content increased with pressure presenting a maximum at 400 MPa. Pressurized samples retained vitamin C content. Based on these results, working at 400 MPa for 10 min ensures physicochemical and high levels of nutritional parameters in osmo-dried strawberries.

Año: 2013

Palabras claves: Osmotic dehydration; High hydrostatic pressure; Antioxidant capacity; Total phenolic content; Colour; Vitamin C; Strawberry

Referencia APA: Nuñez-Mancilla, Y., Pérez-Won, M., Uribe, E., Vega-Gálvez, A., & Di Scala, K. (2013). Osmotic dehydration under high hydrostatic pressure: Effects on antioxidant activity, total phenolics compounds, vitamin C and colour of strawberry (Fragaria vesca). LWT - Food Science And Technology, 52(2), 151-156.

Rehydration Capacity of Chilean Papaya (Vasconcellea pubescens): Effect of Process Temperature on Kinetic Parameters and Functional Properties.

Autores:

Zura, L., Uribe, E., Lemus-Mondaca, R., Saavedra-Torrico, J., Vega-Gálvez, A., & Di Scala, K.

Resumen:

Slabs of Chilean papaya hot air-dried at 60 °C were rehydrated at 20, 40, 60, and 80 °C to study the influence of process temperature on mass transfer kinetics during rehydration. Diffusive and empirical models were selected to simulate the experimental rehydration curves. All models parameters showed dependence with temperature, thus activation energy could be estimated according to an Arrhenius-type equation. Among the applied models, Weibull provided the best fit for each rehydration curve based on the statistical tests RMSE, SSE, and chi-square. According to these results, this model could be used to estimate the rehydration time of Chilean papaya. In addition, rehydration ratio and water-holding capacity were analyzed. Both indices showed a decrease with increasing rehydration temperature indicating modification of the papaya cell structure due to thermal treatment which resulted in a reduction of the rehydration ability, in particular at high rehydration temperatures.

Año: 2013

Palabras claves: Chilean papaya, Rehydration kinetics, Mathematical modeling, Water-holding capacity, Rehydration ratio.

Referencia APA: Zura, L., Uribe, E., Lemus-Mondaca, R., Saavedra-Torrico, J., Vega-Gálvez, A., & Di Scala, K. (2013). Rehydration Capacity of Chilean Papaya (Vasconcellea pubescens): Effect of Process Temperature on Kinetic Parameters and Functional Properties. Food Bioprocess Technol, 6(3), 844-850.

Chemical and physical properties of aloe vera (Aloe barbadensis Miller) gel stored after high hydrostatic pressure processing.

Autores:

Scala, K., Vega-Gálvez, A., Ah-Hen, K., Nuñez-Mancilla, Y., Tabilo-Munizaga, G., Pérez-Won, M., & Giovagnoli, C.

Resumen:

The aim of this study was to evaluate the influence of high hydrostatic pressure (150, 250, 350, 450, and 550 MPa), applied for 5 minutes, on antioxidant capacity, total phenolic content, color, firmness, rehydration ratio, and water holding capacity of aloe vera gel stored for 60 days at 4 °C. The analyzed properties of the pressurized gel showed significant changes after the storage period. The highest value of total phenolic content was found at 550 MPa. However, a decrease in the antioxidant capacity was observed for all pressurized gel samples when compared to the control sample (p < 0.05). The smallest changes in product color were observed at pressure levels between 150 and 250 MP. The application of high hydrostatic pressure resulted in lower gel firmness, and the lowest value was found at 150 MPa (p < 0.05). On the other hand, the untreated sample showed a greater decrease in firmness, indicating that high pressure processing preserves this property. The application of high hydrostatic pressure exhibited modifications in the food matrix, which were evaluated in terms of rehydration ratio and water holding capacity.

Año: 2013

Palabras claves: Antioxidant capacity; total phenolics; quality; aloe vera.

Referencia APA: Scala, K., Vega-Gálvez, A., Ah-Hen, K., Nuñez-Mancilla, Y., Tabilo-Munizaga, G., Pérez-Won, M., & Giovagnoli, C. (2013). Chemical and physical properties of aloe vera (Aloe barbadensis Miller) gel stored after high hydrostatic pressure processing. Food Science And Technology (Campinas), 33(1), 52-59.

Quality Characterization of Waste Olive Cake During Hot Air Drying: Nutritional Aspects and Antioxidant Activity.

Autores:

Uribe, E., Lemus-Mondaca, R., Vega-Gálvez, A., López, L., Pereira, K., & López, J., Ah-Hen, K., Di Scala, K.

Resumen:

Olive cake, a by-product of the olive oil industry, was characterised through a drying process, where the influence of air drying temperature on physicochemical properties and antioxidant activity was investigated. A comparison of fresh and dehydrated olive cake showed that drying led mainly to denaturation of crude protein. Crude fibre content showed a slight increase during drying and may have undergone some alterations in its structure due to Maillard reactions. Fatty acid analysis revealed that olive cake was especially rich in oleic acid and fatty acid composition did not significantly change during drying. Ash content also showed a slight variation but may be considered as practically unchanged. Potassium and sodium were respectively the most and the least abundant minerals found in olive cake. Total phenolic content showed a direct relationship to DPPH radical scavenging activity. Overall antioxidant activity, highest in fresh olive cake, was affected by air drying temperatures being more evident at 90 °C. Vitamin E showed an increasing trend at all drying temperatures. According to this investigation, convective dehydration can lead not only to a dried olive cake that can be used as a material for many processing industries (e.g. food and cosmetic) but also can contribute to minimize the environmental impacts of this agro-industrial waste.

Año: 2013

Palabras claves: Olive cake, Convective dehydration, Phenolic compounds, DPPH, Antioxidant activity, Vitamin E.

Referencia APA: Uribe, E., Lemus-Mondaca, R., Vega-Gálvez, A., López, L., Pereira, K., & López, J., Ah-Hen, K., Di Scala, K. (2013). Quality Characterization of Waste Olive Cake During Hot Air Drying: Nutritional Aspects and Antioxidant Activity. Food Bioprocess Technol, 6(5), 1207-1217.

No evidence of a trade-off between drought and shade tolerance in seedlings of six coastal desert shrub species in north-central Chile.

Autores:

Martínez-Tillería, K., Loayza, A., Sandquist, D., & Squeo, F.

Resumen:

We found species-specific differences in the temporal pattern of mortality. Water and/or light levels affected seedling survival of all species, excluding C. chilensis. Relative growth rate (RGR) increased in low-light conditions in C. chilensis and P. revolutus, but otherwise did not vary in response to differences in either light or water, independently or to their interaction. Across species, the effect of water on specific leaf area (SLA) was inconsistent, increasing both in drought conditions (C. chilensis) and in treatments with supplemental water (S. cumingii). Additionally, SLA tended to increase with decreasing light levels for most species (F. thurifera, H. parvifolius, C. chilensis). In our study, only F. thrurifera and C. chilensis showed changes in leaf mass ratio (LMR) and only with respect to light levels; specifically, LMR tended to increase with decreasing light level. Biomass allocation was independent of light and water for all species except F. thurifera, which showed an increase in root biomass in drought conditions.

Año: 2012

Palabras claves: Atacama desert; Biomass allocation; Centaurea chilensis ; Encelia canescens ; Flourensia thurifera ; Haplopappus parvifolius ; LMR ; Pleocarphus revolutus ; RGR ; Seedling performance; Senna cumingii ; SLA

Referencia APA: Martínez-Tillería, K., Loayza, A., Sandquist, D., & Squeo, F. (2012). No evidence of a trade-off between drought and shade tolerance in seedlings of six coastal desert shrub species in north-central Chile. J Veg Sci, 23(6), 1051-1061.

Application of high hydrostatic pressure to aloe vera (Aloe barbadensis Miller) gel: Microbial inactivation and evaluation of quality parameters

Autores:

Vega-Gálvez, A., Giovagnoli, C., Pérez-Won, M., Reyes, J., Vergara, J., & Miranda, M. et al.

Resumen:

High hydrostatic pressure (HHP) is an innovative technology which minimizes loss of physicochemical and nutritional quality matching consumer demands for fresh-like foods. The aim of this study was to investigate the effect of high hydrostatic pressure (300, 400 and 500 MPa/1, 3 and 5 min) on microbial inactivation and quality parameters of A. vera gel after 60 days of storage. Shelf life was determined successfully by fitting experimental microbial data to the modified Gompertz equation for samples treated at 300 MPa/1 min. The samples treated at 400 and 500 MPa during 1, 3 and 5 min presented undetectable levels of microorganisms' counts. Based on microbiological results, the analysis of quality attributes was focused on the effects of HHP (300, 400 and 500 MPa) during 5 min of processing. Antioxidant activity, which was analyzed by means of total polyphenols content and DPPH-radical scavenging activity, showed a maximum value at 500 MPa. At 400 MPa, vitamin C showed the maximum retention (93%) and vitamin E increased the initial value of the gel. An increase of polysaccharides at 500 MPa also affected the gel firmness. Differences in surface color were also observed. Based on results, application of 500 MPa during 5 min may be successfully used to preserve main quality attributes of A. vera gel.

Año: 2012

Palabras claves: High hydrostatic pressure; Quality indices; Microbial growth; Shelf life; A. vera gel

Referencia APA: Vega-Gálvez, A., Giovagnoli, C., Pérez-Won, M., Reyes, J., Vergara, J., & Miranda, M. et al. (2012). Application of high hydrostatic pressure to aloe vera (Aloe barbadensis Miller) gel: Microbial inactivation and evaluation of quality parameters. Innovative Food Science & Emerging Technologies, 13, 57-63

Effect of high pressure on the interactions of myofibrillar proteins from abalone (Haliotis rufencens) containing several food additives.

Autores:

Barrios-Peralta, P., Pérez-Won, M., Tabilo-Munizaga, G., & Briones-Labarca, V.

Resumen:

Changes induced by high hydrostatic pressure (HHP) processing on the chemical and functional properties of seafood proteins and their interactions with selected food additives, such as potato starch (PS), dried egg whites (EW) and agar, were studied at pressures ranging from 200 to 550 MPa for 3, 5 and 10 min. Phosphate buffers were used to extract abalone muscle myofibrillar proteins. Protein changes was studied by UV–visible spectroscopy and functionality by their emulsifying capacity. The results show changes in peak heights and the appearance of new peaks at 327 nm in pressurised samples with additives; however, interactions between myofibrillar proteins and food additives did not take place, the same was observed by SDS-PAGE, regardless of the pressure treatment applied. In contrast, the emulsifying capacity increased in samples with agar and PS treated at 350–550 MPa. The highest emulsifying capacity was obtained in samples with 4 g PS/100 mL of protein dilution at 450 MPa for 5 min, while the emulsifying capacity decreased at 200 MPa using 10 g EW/100 mL of protein. No changes in protein bands were observed for all samples, suggesting that high pressure did not influence changes in the molecular weights of the proteins.

Año: 2012

Palabras claves: Myofibrillar protein; High hydrostatic pressure; Starch; Agar; Abalone.

Referencia APA: Barrios-Peralta, P., Pérez-Won, M., Tabilo-Munizaga, G., & Briones-Labarca, V. (2012). Effect of high pressure on the interactions of myofibrillar proteins from abalone (Haliotis rufencens) containing several food additives. LWT - Food Science And Technology, 49(1), 28-33.

Effects of high hydrostatic pressure on microstructure, texture, colour and biochemical changes of red abalone (Haliotis rufecens) during cold storage time.

Autores:

Briones-Labarca, V., Perez-Won, M., Zamarca, M., Aguilera-Radic, J., & Tabilo-Munizaga, G.

Resumen:

This study was carried out to evaluate the effect of high hydrostatic pressure on quality changes (microstructure, colour, texture and biochemical) of red abalone (Haliotis rufecens) during storage time at 4 °C. High hydrostatic pressure (HHP) treatments were applied at 500 MPa for 8 min and 550 MPa for 3 and 5 min. Biochemical indices covering pH, total volatile basic nitrogen (TVB-N) and trimethylamine (TMA), as well as instrumental texture, microstructure and colour of abalone samples were determined immediately after treatment and throughout subsequent storage at 4 °C. Results have shown that HHP-treated abalones have significantly (p ≤ 0.05) higher pH, moisture and ash content than untreated abalones. Protein and fat contents of treated abalones were significantly (p ≤ 0.05) lower compared to untreated sample (control). TVB-N and TMA levels for HHP-treated abalones rose over the storage period but did not exceed 28 mg TVB-N/100 g and 3 mg TMA/100 g, respectively at the end of 60 days. Instead, the untreated sample exceeded the allowed limit in a 30 day period for the TVB-N and TMA. However, all HHP treatments had less negative effects on tissue colour of abalone than untreated samples in the cold storage time; moreover, whiteness index was reduced to 8% at the end of day 60. A more compact structure was identified as high hydrostatic pressure was higher. Thus, it was concluded that holes in muscle fibres were often due to protein gelation, whenever pressure and protein concentration are high enough, confirming that the structure of abalone muscle treated with high hydrostatic pressure differed significantly from that of raw abalone meat.

Año: 2012

Palabras claves: High hydrostatic pressure; Abalone; Colour; pH; TVB-N; TMA; Microstructure

Referencia APA: Briones-Labarca, V., Perez-Won, M., Zamarca, M., Aguilera-Radic, J., & Tabilo-Munizaga, G. (2012). Effects of high hydrostatic pressure on microstructure, texture, colour and biochemical changes of red abalone (Haliotis rufecens) during cold storage time. Innovative Food Science & Emerging Technologies, 13, 42-50.

Hydro-meteorological trends in semi-arid north-central Chile (29–32°S): water resources implications for a fragile Andean region

Autores:

Souvignet, M., Oyarzún, R., Verbist, K., Gaese, H., & Heinrich, J.

Resumen:

Changes in hydro-meteorological historical records are of considerable importance for future planning. This study analyses trends of hydro-climatological indices of annual and seasonal precipitation, temperature and discharge in the “Norte Chico” region of Chile (29–32°S), located in the Central Andes. It addresses how these trends possibly impacted on the water resources in a nival regime, typical for arid mountainous regions. Homogenous records were tested against monotonic trends using the non-parametric rank-based Mann-Kendall test. The results suggested, at a very high confidence level, a strong warming signal trend over recent decades, consistent at the annual and seasonal levels. Furthermore, warmer days are observed in summer, especially at higher elevations. The region also experienced a shift in the rainy season over the last 42 years. However, an increase in precipitation was observed over recent decades, whereas an annual decrease was the general tendency when the whole century was considered. Changes in discharge were not unequivocal and glacier retreat has been compensated for possibly by an increase in snowmelt in recent years. Hence, in an under-studied area, from the hydrological perspective, this work provides some insights for a better understanding of changing hydrological processes in the mid-latitude Andes Cordillera.

Año: 2012

Palabras claves: trend detection, variability, climate change, hydro-climatological indices, arid region, Chile.

Referencia APA: Souvignet, M., Oyarzún, R., Verbist, K., Gaese, H., & Heinrich, J. (2012). Hydro-meteorological trends in semi-arid north-central Chile (29–32°S): water resources implications for a fragile Andean region. Hydrological Sciences Journal, 57(3), 479-495.

Shrub facilitation increases plant diversity along an arid scrubland-temperate rain forest boundary in South America

Autores:

van Zonneveld, M., Gutiérrez, J., & Holmgren, M.

Resumen:

Theoretical models predict nurse plant facilitation enhances species richness by ameliorating stressful environmental conditions and expanding distributional ranges of stress-intolerant species into harsh environments. We studied the role of nurse facilitation on the recruitment of perennial plants along an arid scrubland–temperate rain forest boundary to test the following predictions: (1) nurse shrub canopy increases seedling abundance and species richness along the rain forest–scrubland boundary; (2) scrubland species are less dependent on facilitative interactions than temperate rain forest species, especially at the moister, upper end of the gradient.

Año: 2012

Palabras claves:

Referencia APA: van Zonneveld, M., Gutiérrez, J., & Holmgren, M. (2012). Shrub facilitation increases plant diversity along an arid scrubland-temperate rain forest boundary in South America. J Veg Sci, 23(3), 541-551.