University of Lleida

About: University of Lleida is a education organization based out in Lleida, Spain. It is known for research contribution in the topics: Population & Pregnancy. The organization has 2939 authors who have published 5853 publications receiving 148417 citations. The organization is also known as: Escola Superior Politècnica & Universitat de Lleida.

Chapter 11 Hydrological effects of dams and water diversions on rivers of Mediterranean-climate regions: examples from California

Abstract: Rivers in Mediterranean-climate and other semi-arid regions tend to be more heavily impounded and thus their hydrology more strongly affected than rivers in humid climates because demand for water is greater (to supply irrigated agriculture) and runoff is out-of-phase with demand. The impounded runoff index (ratio of reservoir capacity divided by mean annual runoff) is 0.8 on the Sacramento and 1.2 on the San Joaquin Rivers of California, much higher than rates: encountered in humid Atlantic climate regions. As a result of these high levels of impoundment, the overall magnitude and seasonal distribution of flow has changed substantially. Flood peaks tend to be reduced: the Q2 declined on average 53 and 81% in the Sacramento and San Joaquin River basins, respectively. On many rivers, summer baseflows have increased to supply irrigation diversions downstream, creating a flatter hydrograph that no longer supports dynamic channel processes and the aquatic ecosystem that depends upon such channel dynamics. Vegetation has encroached in the formerly active channels of many rivers in response to reduced flood scour and sediment supply.

Browning, polyphenol oxidase activity and headspace gas composition during storage of minimally processed pears using modified atmosphere packaging

Abstract: Modified atmosphere packaging was used to prevent browning of minimally processed Conference pears, thus extending their shelf-life. Colour changes as well as PPO activity were strongly influenced by the package headspace gas composition, which was determined by the packaging conditions. The initial colour of minimally processed pears was preserved for several weeks under cold storage in plastic pouches of very low O2 permeability and an initial atmosphere of 100% N2. A fractional conversion kinetic model fitted the experimental browning data with high accuracy. Colour degradation (ΔE*) of minimally processed pears occurred exponentially (kΔE = 0.019–0.077 day−1) owing to changes in lightness (kL = 0.021–0.07 day−1). In contrast, PPO exhibited a linear increase in activity which could be related to the availability of O2 in the package headspace. © 2002 Society of Chemical Industry

Quality changes in fresh-cut Fuji apple as affected by ripeness stage, antibrowning agents, and storage atmosphere.

Abstract: The effect of ripening state, modified atmosphere, and the use of antibrowning agents was investigated in an attempt to determine optimum ripeness and processing conditions for extending the shelf-life of fresh-cut Fuji apple. Apples were classified in 3 groups: mature-green, partially ripe, and ripe; after peeling and slicing, fruits were treated with 1% (w/v) N-acetylcysteine, or 1% (w/v) ascorbic acid (control), and then packed into polypropylene trays with air or a gas mixture (2.5% O2 + 7% CO2 + 90.5% N2) and sealed. Trays containing the apple slices were stored in darkness at 4 degrees C +/- 1 degree C and analyzed periodically during 43 d. Changes in atmosphere composition, color, and firmness were examined. Partially ripe apples, based on their lower ethanol production and maintenance of their original color and firmness, were the most suitable to prepare the fresh-cut commodities. A postcutting dip in 1% (w/v) N-acetylcysteine was the most effective treatment to prevent cut surface browning and preserve the initial appearance of Fuji apple slices during more than 1 mo at 4 degrees C. Low O2 and elevated CO2 (2.5% O2 + 7% CO2) atmosphere extended the shelf life of apple slices because of a significant inhibition of ethylene production.