Experimental study of the application of edible coatings in pumpkin sticks submitted to osmotic dehydration

Abstract

Osmotic dehydration (OD) process permits to improve the organoleptic characteristics of the products; nevertheless, depending of the product, the incorporation of great amounts of solute can be not desirable for consumers. The application of hydrogel coatings would contribute to overcome this inconvenient acting as a barrier to solute entering. An Alginate-Calcium Chloride barrier system (A-CC) was tested with or without pretreatment of Ca2+ as a firmness agent applied to pumpkin sticks. Products were dehydrated in sucrose and glucose solutions (40 and 60 % w/w). Different parameters were estimated along the process such as soluble solids uptake, water content, weight reduction; besides, texture and microstructural changes were studied. The A-CC configuration complies with the barrier function to solids uptake from the dehydrating solution in case of 60% of sucrose, allowing water exit from the vegetal matrix. The pretreatment with Ca2+ contributed to the retention of the product firmness. Integrity, adhesiveness and thickness of the A-CC system during the OD process were evaluated by ESEM. In this case, the coating thickness reduction was according to the product weight reduction, indicating that the coated product was dehydrated as an integrated system.