Phenylalanine ammonia-lyase (PAL, EC 4.3.1.5.) activity, tanning ability, and polyphenols levels were measured in cherimoya (Annona cherimola Mill.) fruit treated with 20% CO(2) + 20% O(2) + 60% N(2) for 1, 3, or 6 days during chilling temperature (6 degrees C) storage. The residual effect of CO(2) after transfer to air was also studied. These observations were correlated with texture and cellular characteristics, visualized by cryo-SEM. Tanning ability and the early increase in tannin polyphenols induced by chilling temperature were reduced by CO(2) treatment. Conversely, high CO(2) atmosphere enhanced the nontannin polyphenol fraction as compared with fruit stored in air. Lignin accumulation and PAL activation observed in untreated fruit after prolonged storage at chilling temperature were prevented by high CO(2). Moreover, the restraining effect on lignification was less effective when the CO(2) treatment was prolonged for 6 days. In addition, fruits held at these conditions had greater firmness and the histological characterization of the separation between cells was similar to that in untreated fruits. We conclude that CO(2) treatment modulates the phenolic response that seems to regulate the strength of cell adhesion and so to prevent hardening caused by chilling temperature storage.

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Zinc deficiency is a world wide problem, centred on the lower income population, though not restricted to it. Food supplementation with magnesium is also considered of interest for correcting deficiencies in this oligoelement. Highpressure partially gelatinised starch is proposed as a vehicle for inclusion of these metals in food products. While highpressure levels (and/or temperature) give rise to total gelatinisation, lower pressures, at temperatures close to ambient, yield partially-gelatinised products, where only a portion of the intramolecular bonds in the amylopectin double helix has been substituted by intermolecular bonds between the unfolded amylopectin and water, as it can be deduced by differential scanning calorimetry, while the resultant granular microstructure is strongly altered (observed by low temperature scanning electron microscopy). Production of this modified starch implies lower energy expense, compared to thermal gelatinisation, and it guarantees higher homogeneity in the final degree of gelatinisation. The effect of moderated high-pressure treatments (400 MPa, 25°C, 35 min) on potato and corn starches has been studied. The effect of pressure treatment, after alkaline treatment or the addition of another hydrocolloid (guar gum) has also been considered. The observed preferential binding of zinc and magnesium salts to these modif ied starches (after determination of metal content by atomic absorption spectrophotometry) is favourable to the use of these products as metal carriers.Additional key words: differential scanning calorimetry, magnesium, metal binding, micronutrients, scanning electron microscopy, supplementation, zinc. Resumen Almidones parcialmente gelatinizados mediante altas presiones como transportadores de oligoelementosLa deficiencia de cinc es una cuestión de alcance mundial, centrada en la población de menores recursos, aunque no restringido a ella. La suplementación de alimentos con magnesio también se considera de interés para corregir las carencias de este oligoelemento. Como vehículo para la inclusión de estos metales en productos alimenticios se propone el almidón parcialmente gelatinizado por alta presión. Mientras que altos niveles de presión (y/o temperatura) causan gelatinización total, menores presiones a temperaturas cercanas a la ambiente rinden productos parcialmente gelatinizados, en los que sólo una proporción de uniones intramoleculares de la doble hélice de amilopectina han sido sustituidas por enlaces intermoleculares entre la amilopectina desenrollada y agua, según se deriva de datos de calorimetría diferencial de barrido, mientras que la microestructura del gránulo resulta muy alterada (observada por microscopía electrónica de barrido de baja temperatura). La producción de este almidón modificado conlleva menor gasto energético, en comparación con la gelatinización térmica, así como garantiza mayor homogeneidad en el grado de gelatinización final. Se ha estudiado el efecto de tratamientos moderados de alta presión (400 MPa, 25°C, 35 min) sobre a...

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The relative stability of spores of Bacillus cereus grown at three different temperatures was examined by using quasi-elastic light scattering (q.l.s.) in conjunction with turbidity and scanning electron microscopy (s.e.m.). Cultures grown at 20, 30 and 40 degrees C (BC20, BC30 and BC40 respectively) were compared in terms of (i) their effective hydrodynamic radius, rH, as determined from q.l.s. and (ii) their gross morphology, as determined from s.e.m. The effects of autoclaving at 121.1 degrees C on both these properties was also examined. We observed (1) that cultures BC20 and BC30 appeared to have similar values for rH, whereas that of BC40 appeared some 50% higher, and (2) BC40 had a correspondingly much lower heat resistance (its structural integrity was lost after about 20 min autoclaving, whereas that of BC20 and BC30 was retained even after 80 min autoclaving). These data were in good agreement with independent measurements of heat-resistance coefficients. Changes in the hydrodynamic radius, polydispersity (both using q.l.s.) and turbidity were monitored with time on addition of the disinfectants sodium hypochlorite and peracetic acid; again BC40 appeared to have a lower resistance.

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