THE IMPACT OF DIFFERENT DRYING METHODS ON SELECTED QUALITY PARAMETERS OF CELERY ROOT

Abstract

In present study, the impact of different drying methods (convective drying, lyophilization and combined drying) on the color, sensory and antioxidative attributes of celery root, was investigated. Samples of celery root were dried convectively in a dryer at 50°C to a constant mass, in a lyophilizer for 48 hours, and by combined dehydration that included low-energy osmotic pretreatment in sugar beet molasses and shortened consecutive lyophilization for 24 hours. Subsequently, dehydrated samples were powdered and subjected to the color instrumental analysis (L, a, b coordinates), sensory analysis (color intensity, taste and odor) and analysis of total phenols content and antioxidant capacity (determined by ABTS and DPPH methods). The results showed that convectively dried celery root sample was darker than combinedly dried, with a greater share of red and yellow tones. The greatest departure from usual taste and odor (grade 4) was characterized for convectively dried powder (grade 5.5 and 5.9), followed by combinedly dehydrated celery (grade 3.2 and 3.0). Regarding the impact of the drying type on the antioxidant capacity, the combined drying confirmed to be the most efficient, DPPH 163.28 μmol TE/100 g d.m. and ABTS 577.28 μmol TE/100 g d.m., due to the molasses input (an excellent source of antioxidants) in the dehydrated celery root. The powder of celery root previously osmotically dried in molasses had an 8.5% higher content of total phenols in comparison to lyophilized powder, even though lyophilization is one of the most effective methods in preserving phenols.