RESUMO
Freezing of artichoke is a promising alternative to storing it in brine and canning. The perishable vegetable was vacuum infused with inulin to improve freezing tolerance. Artichokes with and without inulin were frozen by static, air blast and individual quick freezing (IQF) methods and thawed by microwave, 25 °C and 4 °C temperature levels at each month of 6-months storage. Process conditions were evaluated by multivariate analysis of variance (MANOVA) and were found significant on the quality parameters. Inulin infusion better conserved the aw, color, texture, ascorbic acid and overall integrity of artichokes during frozen storage. Inulin incorporation and IQF showed mutual positive effect on drip loss. Polyphenol oxidase (PPO) activity values fitted to 2nd order kinetic and the highest residuals were determined in static freezing. PPO showed alleviating effect on total phenolic content. Vacuum impregnation caused a color difference prior to freezing, but was found effective for maintaining color during storage. As a result, the use of quick freezing techniques together with the addition of cryoprotectant was effective in the preservation of artichoke quality attributes during frozen storage.
RESUMO
Chokeberry (aronia) fruit is a rich source of bioactive compounds with various health benefits. However, it has a limited shelf life and a firm (tight) structure that makes it difficult for moisture transfer during drying. Therefore, the aim of the study is to investigate the effects of high-power ultrasound pretreatment (550â W, 30â min) and air drying temperature (65, 70 and 75 °C) on the drying rate and bioactive compounds of chokeberry fruit. Accordingly, chokeberries were dried directly or after ultrasound pretreatment, and the retention rate of bioactive properties, i.e., total phenolic, flavonoid and monomeric anthocyanin contents along with antioxidant capacity values, were examined. The required time for drying as well as the activation energy values were significantly lower in ultrasound treated samples. Logarithmic and Midilli models exhibited the best fit for drying kinetics of samples. The pretreatment led to significantly lower moisture content and aw values. Compared to fresh sample, the highest retention rate for some bioactive properties was found in ultrasound pretreated sample dried at 75 °C. The ultrasonication also reduced the electricity consumption (kWh) in all temperature levels of drying operations. As a conclusion, the ultrasound pretreatment prior to drying had dual role by facilitating drying kinetics and by providing higher bioactive contents.
