Color stability of pumpkin (Cucurbita moschata, Duchesne ex Poiret) puree during storage at room temperature: Effect of pH, potassium sorbate, ascorbic acid and packaging material

The color stability of pumpkin (Cucurbita moschata, Duchesne ex Poiret) puree of pH 4.00 and 5.00 containing potassium sorbate (KS), ascorbic acid (AA) or their mixture, packaged in polyethylene and in polyvinyl chloride–polyvinylidene chloride copolymer (PCPC) bags, was analyzed throughout the storage at 25 °C. Color changes were measured through lightness (L), redness (a), yellowness (b). Changes in a and b were mathematically modeled. In general, lightness, redness and yellowness diminished with storage time. The presence of KS diminished color loss of purees packed in PCPC bags and increased the discoloration of purees contained in polyethylene suggesting, in the first case, that KS oxidation diminished the available oxygen protecting carotenoids oxidation, and in the second case, the existence of a coupled oxidation between KS and carotenoids helped by the oxygen presence. Addition of AA to a puree of pH 4.00 containing KS and packed in polyethylene minimized the losses of redness and yellowness; probably as a consequence of the antioxidant action of AA. The increase in pH from 4.00 to 5.00 in the presence of KS significantly minimized color degradation of puree packed in PCPC. From the point of view of improving color stability, a convenient formulation could be a puree of pH 5.00 preserved with KS and packed in PCPC.