Gamma irradiation and storage conditions: effect on pumpkin (Cucurbita moschata, Duchesne ex Poiret) puree quality

MARÍA F. GLIEMMO, MARÍA E. LATORRE, PATRICIA NARVAIZ,;LÍA N. GERSCHENSON, CARMEN CAMPOS.

Chicago, USA

Congreso; Institute of Food Technologist. Annual Meeting. 2009; 2009

Institute of Food Technologist

Pumpkin purees are prone to microbial spoilage and undesirable biochemical changes. These processes may cause beta-carotene degradation inducing sensory and nutritional losses. The objective of this work was to apply a hurdle technology to optimize shelf-life of a pumpkin puree obtained by a 12 min steam process and containing potassium sorbate (KS; 0.120%w/w), vanillin (0.050%w/w) and glucose (10.00%w/w). The pH was adjusted to 5.00 and packing was performed in polyvinyl-polyvinylidene-chloride copolymer bags. The product was heated at 50ºC for 15 min and exposed to gamma irradiation. A Box-Behnken design was performed, in three blocks, with three variables at two levels and a central point, for a total of 45 experiments. The variables and levels were: storage temperature (5.0-12.5-20.0ºC), radiation dose (0.00-0.75-1.50 kGy) and storage time (0-14-28 days). There were analyzed: i) microbial stability, throughout native flora plate count, ii) color stability throughout total color difference determination and iii) rheological behavior throughout consistency index (K), initial yield stress (t0)  and flow index (n) estimations. Yeasts and molds, lactic-acid bacteria, psychrophiles and coliforms did not grow throughout storage. Radiation dose increase produced a significant decrease of aerobe and anaerobe counts. A positive interaction dose-time was observed on the growth of anaerobes. Maximum population of 9.103 and 3.103 CFU/ml, attained for aerobes and anaerobes, respectively, were within the values fixed in Argentinean Food Code for ready to eat dietetic foods. Total color difference enhanced with temperature increase, reaching a maximum of 3.3, which do not allow detecting visual changes. Samples behaved as non-newtonian time-dependent fluids. Values of t0 and K diminished with dose increase and enhanced with temperature increase, although preliminary sensorial evaluation showed no significant changes in texture.   Results obtained demonstrated that hurdles applied assured microbial, color and rheological adequacy throughout 28 storage days offering an alternative process to pumpkin puree preservation.