Screening of commercial cellulase preparations for manufacturing moromi vinegar from purple sweet potatoes [Ipomoea batatas] and their effect on the degradation of anthocyanin

The shochu distillery by-products of sweet potatoes are known as starting materials for moromi vinegar. Cellulase treatment of the by-products improves the manufacture of moromi vinegar and filterability of the by-products. In this study, 20 commercial cellulase preparations have been investigated on their filterability and degradation of anthocyanin for moromi vinegar from purple sweet potatoes. Improvement of the filterability was rendered excellent by the Trichoderma origin compared with those of the Aspergillus origin. Many cellulase preparations degraded the taste of the vinegar. Six cellulase preparations gave bitterness and egumi to the vinegars ; 4, bitterness ; 1, bitterness and acidity ; and 3, acidity. Two cellulase preparations did not change the taste. After the treatment with 12 cellulase preparations, the vinegar still retained a purple color, but 4 preparations significantly degraded the purple color. When the best preparation was used for 500 1 scale-vinegars, the filterability was improved and no degradation of anthocyanin was observed.