Edible Coating Technology for the Stabilization of Functional Foods Based on Pumpkin

Abstract

Vegetable foods were prepared from blanched Cucurbita moschata Duchesne ex Poiret (pumpkin) and enriched with probiotics, particularly Lactobacillus casei (ATCC 393) or enriched with probiotics and fortified with iron (Fe). With the purpose of extending the shelf life of the product, the application of edible coating (EC) was tested using both a drying and a non-drying process. Likewise, the probiotic survival capacity to the different applied technologies was studied and the effect of processes used on the color characteristics of the final product was evaluated. According to the results, ir was verified that the application of an EC based on aga-agar extended up tp 14 dyas (8°C) the shelf life of the pumpkin impregnated with L. casei. The pH reduction and drying processes contributed to prolonging the storage time, reaching 18 days at 20°C witha viability of the probiotics around 8 log CFU/g product. In additon, a loss of color was observed, possibly as a result of the pigmen degradation. It was also demonstrated that the pumpkin tissue was able to contain L. casei. In the case of cmbined enrichment with probiotics and Fe, the blanched pumpkin was subjected to a dry infusion process to incorporate the mineral and, in addition, it was coated with an EC based on hydroxypropyl methylcellulose (HPMC) containing L. casei. Two kinds of HPMC based coatings were evaluated, one with 28-30% of methoxyl gropus (E4M) and the other one with 19-24% of methoxyl groups (K4M). Six coating systems were studied: A: 3% w/v HPMC E4M, B1 and B2: 1.6% w/v HPMC E4M, C: 3% w/v HPMC K4M, D1 and D2: 1.6% w/v HPMC K4M. Systems A, B1, C and D1 were submitted to a drying process with forced air convection at 46°C for 4 h while systems B2 and D2 were dehydrated at 38°C for 20 h. The viability of L. casei in the final product during storage and the bioaccesibility Fe in the intestinal lumen (55-77%) did not show significant differences among the studied systems, consequently, the type of hydrocolloid and drying process did not affect these parameters. However, at 14 days of storage at 8°C, a lower stabilization capacity of L. casei was observed for the systems D1 and D2. The obtained results allow confirming that EC is a realistic alternative for the stabilization of vegetal foods enriched with Fe and / or probiotics. The EC technology has proved to be useful for adding value to a vegetal product and to expand the offer of functional foods.