The objective of this study was to evaluate the influence of package materials on the preservation of cold-stored 'Kumagai' guavas. The treatments were: PO2, coextruded polyolephinic film with gas injection (5% O 2 /5% CO 2 /N 2 ); PO3, coextruded polyolephinic film with gas injection (5% O 2 /5% CO 2 /N 2 ); LDPE, linear low density polyethylene film; LDPE-gas, linear low density polyethylene film with gas injection (3% O 2 /8% CO 2 /N 2 ); PVC, polyvinylchloride stretch film; PO1, co-extruded polyolephinic film and control: non-packaged guavas. Guavas were stored at 10 ± 1°C/80-90% RH for 21 days, and then transferred to room temperature. Gas composition within the package headspace was analysed during storage and the physical and chemical characteristics of the guavas were evaluated daily during ripening. The modified atmosphere provided by PO1 film was insufficient to promote the benefit of senescence control. Although PVC provided an atmosphere close to that recommended, it did not preserve the colour and pulp firmness. PO2, PO3, LDPE and LDPE-gas retarded the senescence process of the guavas during 21 days at 10°C plus 2 days at room temperature, but harmed the normal ripening of guavas in some aspects. This can be explained by reduced O 2 and elevated CO 2 levels within these four packages. None of the packages influenced the titratable acidity and the soluble solids, but they did harm ascorbic acid synthesis.
INTRODUCTIONGuava is a perishable fruit with a short shelf-life when stored at room temperature. The use of preservation methods that can increase guava shelf-life whilst-maintaining quality is desirable. In climacteric fruits, reduction of temperature retards the climacteric and consequently the ripening process. 1 The recommended storage temperature for guavas is 9-10°C in order to avoid chilling injury.
2,3Many studies have evidenced the efficiency of plastic packages on guava preservation by reducing the ripening and weight loss.4-6 Guavas could be stored for 2 weeks when packed in polyethylene films impregnated with humidity-absorbent mineral.7 'Kumagai' guavas could be conserved in sealed polyethylene packages for 3 weeks at 8°C.
8The major reason for using modified atmosphere packaging is that the low O 2 and high CO 2 concentrations reduce the respiration rate and consequently slow down quality loss. Concentrations below 8% O 2 and/or above 3% CO 2 reduce ethylene production and sensitivity. 9 Atmosphere modification within a package can occur passively, as the product consumes O 2 and discharges CO 2 , or can be promoted actively by vacuum followed by gas mixture injection. In both cases, the package permeability must be compatible with the vegetal respiration rate, maintaining an appropriate atmosphere for a better conservation.
10The objective of this work was to evaluate the influence of package materials, associated or not with active atmosphere modification, on the preservation of cold-stored 'Kumagai' guavas.
MATERIALS AND METHODS'Kumagai' guavas (Psidium guajava) were harvested from ...