Study the effect of pre-treatment of drying ‘mortiño’ (Vaccinium floribundum Kunth) with reference to drying rate and total content of soluble polyphenols and anthocyanins

Resumen

The aim of this work was to study the effect of pre-treatments on drying of ‘mortiño’, on the drying rate and total content of soluble polyphenols and anthocyanins. It was applied to fresh fruit pre-treatment of immersion bath of aqueous solution of ethyl oleate and potassium carbonate. It was used a 2² factorial design with axial points, to evaluate its effect on the drying rate and content of phenolic compounds. It was performed a second pre-treatment with SO₂, it was used a 2² factorial design to study its effect on the content of phenolic compounds. Stability assays were performed with dried fruits stored in a laminated multilayer film and metalized for 2 months under refrigeration (4 °C), freezing (-17 °C) and 25 °C at 90 % RH. It was evaluated the moisture content, color, soluble polyphenols and anthocyanins. It was conducted a sensory analysis of the product. The best conditions to dry ‘mortiño’ are 40 ºC, airflow of 0.24 m³/s, immersion bath concentration of 1.55 % K₂CO₃ (w/w) -             1.25 % of ethyl oleate (V/V), concentration of SO₂ 2 000 ppm and sulfidation 2 h. The product was dried to 5 % moisture in the oven in 40 % less time required to dry without pretreatments. The dried ‘mortiño’ retained 98.2 % of anthocyanins and 99.7 % of soluble polyphenols in relation to freeze-dried ‘mortiño’. Meanwhile the ‘mortiño’ dried by solar dryer hybrid retained 88.5 % of anthocyanins and 99.7 % of soluble polyphenols. The product stored at 18 °C in a multilayer film laminated and metalized, retains 50 % of anthocyanins in relation to its initial content in 4 months and 11 days