Change of anthocyanins content during raspberry extraction

Abstract

Change in anthocyanins content under different conditions of extraction enzymatic maceration and heat treatment of two raspberry cultivars (Villamette and Meeker) was determined. Experiments were carried out on a laboratory hydraulic extractor. During extraction commercial operating conditions were emulated using a "Bucher" extractor (pressure 180-200 bar 1-3 pulp shakings). A pectin preparation Klerzyme®120, manufactured by DSM France, was used for maceration and depectinization, because it is specific for "sour fruits" with pH below 3.2. At a single-stage maceration, it was applied in the amount of 200-400 g/t, for 1-2 hours at 50oC. In a two-stage maceration and depectinization, the enzyme was added as follows: in the first stage 100-200 g/t for 0.5 - 1 hour at 20oC and in the second stage 4-8 g/hl for 1-2 hours at 200C. Thermal breaks of raspberry pulp were performed at raised temperatures for 2 and 5 min in order to examine the effects of raised temperatures on anthocyanins extraction. The application of heat-enzymatic treatments of the pulp prior to extraction proved to be suitable in both raspberry cultivars. Apart from well-known degrading effects of heat on anthocyanins, the juice obtained by extraction, after enzymatic maceration, has higher anthocyanins content by 30% than the juice obtained without enzymatic maceration. Juice pasteurization, in each stage of processing, produced markedly negative effect on anthocyanins content therefore their content decreases considerably. The forms of anthocyanins that are lost most are those uncolored. In batches subjected to a two -stage enzymatic maceration, despite initial high anthocyanins content, the content of total anthocyanins is reduced after the second pasteurization to the approximate value as that in batches subjected to a single-stage enzymatic maceration.

Keywords

• anthocyanins
• raspberry
• extraction
• pectin preparation