The treatment with enzymes causes an increasing of all the
substances of juice: total soluble solids, organic acids (measured as
total acidity), proteins and polyphenols; in fact pectolytic enzymes
are normally used to increase yields of extraction of plant tissues
. Results agree with literature data reporting that enzymatic
hydrolysis of the cell walls increases the reducing sugars, soluble
dry matter content, galacturonic acid content and titrable acidity of
several fruit juices In this case the
most interesting data is the polyphenols content, which is almost
triplicate in the juice treated with the high enzyme concentration
(PJ7E3) respect to the control (PJ7E0), and it is also significantly
higher respect to the juices obtained from the mixtures containing
peels (see Table 2). Polyphenols content of samples PJ7E2 was a
little lower compared to PJ7E1: this fact could be due to proteine
polyphenols complex precipitation, as reported by Wang, Zhang,
Liang, and Yuan (2013), because sample PJE2 presented also a
lower protein content respect to PJ7E1.
However, the turbidity values reached are still high, and the
obtained juices needed a further clarification step in order to achieve
acceptable product stability and a limited cloudiness during
storage, or could be mixed with juices of other fruits, as commonly
observed on the market.