Roasting and packaging in nitrogen atmosphere protect almond var. Guara against lipid oxidation.

The effect of packaging in nitrogen (N2) atmosphere or in air on the quality of peeled and roasted almond var. Guara during storage for 20 weeks at 20 °C ± 1 °C and 65-70% relative humidity (RH) was studied. No changes in the sugar, fat, protein or fiber contents were observed during the storage period nor in color. Only the lipid fraction showed significant changes with the kind of packaging atmosphere. The composition of fatty acids remained unchanged during the 5 month storage in all the samples. Packaging in N2 atmosphere was seen to have a protective effect against the accumulation of conjugated dienes (CD) in peeled almonds, while in roasted almonds, the protective effect was lower and even nil by the end of storage. The contrary effect was observed for the ultraviolet (UV; K270) index which increased more slowly in the roasted samples packaged in N2, while in peeled samples it reached the same levels at the end of storage regardless of the packaging atmosphere. No effect of the packaging atmosphere was observed on the evolution of the peroxide value in the tested samples (peeled or roasted almonds). None of these changes in the lipid fraction was reflected in the final sensory quality of the samples and the taster panel found no changes in the sensory quality in any case.

Influence of irrigation and organic/inorganic fertilization on chemical quality of almond (Prunus amygdalus cv. Guara).

The chemical quality of almonds variety Guara cultivated in nonirrigated farming (NI) and drip-irrigated farming (DI) conditions with different fertilizing treatments, two organic treatments (T1 and T2) and a mineral treatment (C), all of them with a N-P-K proportion of 1-2-1, is studied. Almonds obtained in irrigated farming showed higher content in sugars and organic acids and a better quality of oil. Among the fertilizing treatments employed, the organic ones have shown the best results related to chemical quality, regardless of the quantity of fertilizer employed (9.5 kg per T1 tree vs 4.5 kg per T2 tree). The organic treatments produced almonds with a higher content of sugar, organic acids and fiber and a similar fat content. These results are interesting from a commercial point of view since the consumers, even under the same conditions of chemical quality, prefer those products cultivated under organic conditions due to their benefits for health and because these practices are environment-friendly.

Electron beam ionization induced oxidative enzymatic activities in pepper (Capsicum annuum L.), associated with ultrastructure cellular damages.

Mature green pepper fruits (Capsicum annuum L.) were subjected to ionizing radiation, in the range of 1-7 kGy, with accelerated electrons. Ultrastructural changes by electron microscopy, and the activity of several oxidative metabolism-related enzymes such as superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), guaicol peroxidase (POX), and lipoxygenase (LOX), were determined in pericarp tissue just after the ionization treatment and during postionization storage at 7 degrees C followed by 3 days at 20 degrees C. Changes in oxidative stress during the ionization treatment was assessed by the accumulation of malondyaldehide (MDA), a lipid peroxidation product. The ionization induced modifications in the cell ultrastructure, a moderate separation of the plasma membrane from the cell wall being observed for all doses. At 5 and 7 kGy, peroxisomes were not detected and the structures of the chloroplast and vacuoles were seriously damaged. Lipid peroxidation and lipoxygenase activity increased with the ionization dose, staying constant and decreasing, respectively, during the storage period. Conversely, catalase, ascorbate peroxidase, and superoxide dismutase had lower values than in nonionized fruits and, in general, their values did not change or diminished slightly from the seventh day of storage. Peroxidase exhibited an increase in activity with the ionization dose, although these was not a linear relationship, with higher values at 3kGy. Ionization of pepper, especially at doses of 5 and 7 kGy, caused a significant oxidative damage in the fruit, since it increased oxidation and decreased the antioxidant enzymatic defense systems causing ultrastructural changes at cell level.

Role of ethylene and abscisic acid in physicochemical modifications during melon ripening.

Hormonal metabolism associated with fruit ripening in two cantaloupe muskmelon cultivars, Talma and Manta, has been studied. The ethylene crisis began on day 33 after fruit set, reaching the maximum values of internal ethylene concentration and ethylene production rate on day 35 after fruit set. This was the optimum moment for consumption as shown by the higher content in soluble solids, ripening index, sensory analysis, and color parameter values. The b parameter and the b/a quotient values in peel were good indicators of the maturity stage, the optimum moment for harvesting being about day 33 after fruit set (when autocatalytic ethylene synthesis has begun), with values of 20 and 5 for the b parameter and b/a quotient, respectively. In both cultivars, free 1-aminocyclopropane-1-carboxylic acid (ACC) content increased until day 35 after fruit set and conjugated ACC increased in postclimacterium. The increase in both ACC-synthase and ACC-oxidase activities together could be responsible for the climacteric ethylene production. Significant differences in the abscisic acid evolution in Talma and Manta cultivars were reached, and also a possible stimulation of ethylene by this hormone could be established.

Kinetic and operational study of a cross-flow reactor with immobilized pectolytic enzymes.

The kinetics and operational behavior of a nylon membrane derivative with immobilized pectolytic enzymes in a cross-flow reactor were analyzed. A high dependence on the recycling flow rate was observed. A design equation of the system has been proposed by taking into account both the shear stress deactivation and the control of the external diffusional limitations. Integration of the resulting design equation allowed us to study the effect of different operational parameters on substrate conversion. The catalytic efficiency of the immobilized derivative in a cross-flow reactor showed the highest pectin hydrolysis capability when it was compared with two different configurations of packed-bed reactors.

A cross-flow reactor with immobilized pectolytic enzymes for juice clarification.

A new system for continuous juices clarification is presented. The bioreactor combines microporous plates commercially available and industrial pectinases immobilized on nylon membranes in a cross-flow configuration. The kinetic behaviour of the reactor for different recirculation flow rates has been determined. Fresh apricot juice has been continuously clarified in the bioreactor with excellent results.