engleski

Influence of processing on yield and quality of cloudy plum juices

Pressing of plum fruit in producing cloudy juices is difficult due to high amount of pectic substances in plum. Maceration of pulp with enzymes is usual way to make pressing more effective but provided that no negative impact on juice quality and biological value e.g. antioxidant capacity (AC). Content of anthocyanins and other phenolic compounds in juices are related with its AC so better extraction of these compounds from fruit to juice is of great importance to obtain juice with nice colour, health benefits and excellent sensory characteristics. The aim of this work was to investigate the influence of enzyme concentration, maceration temperature and duration on the yield, content of phenolic compounds, anthocyanins, AC and sensory perception in producing cloudy juices. Plum fruit (Prunus domestica L.), cultivar Bistrica, was used to produce cloudy juices on small scale equipment. Before pressing, fruits were pitted and treated with maceration enzymes in concentration of 100 or 140 ppm at 20 or 48oC for one or two hours (eight samples). Anthocyanins were determined by method based on bisulfite bleaching, total phenolics (TP) by Folin-Ciocalteu reagent, the AC by FRAP (Ferric Reducing Antioxidant Power) method and sensory evaluation by Quantitative descriptive method. The higher yields were obtained with pre-treatments by 140 ppm of enzyme on 48oC during 1 and 2h, and also in the same juices the highest amount of TP was found. In general, anthocyanin contents increased with enzyme concentration, temperature and duration. Despite some exceptions increasing trend of AC with enzyme concentration and temperature of treatment was observed. Sensory all juices were high evaluated without significant differences. Enzyme treatment on 48oC/2h could be recommended to produce high quality cloudy plum juice due to high yield, high anthocyanin contents and total phenolics, antioxidant capacity and sensory evaluation.

plum juice; enzyme treatment; sensory evaluation; phenolics

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