Introduction
As the most popular fruit beverages worldwide, Citrus
juices represent the predominant industrially processed
fruit products [1]. Among the Citrus species, orange is the
outstanding raw material, but utilization of further species
like mandarins, limes, and lemons is common in various
countries for blends with orange juice or as ingredients for
other fruit products [2]. Commercial Citrus juice is still
mostly preserved by thermal pasteurization, currently being
the most cost-effective means that ensures both microbial
safety and enzyme deactivation [3]. The latter is of prime
importance to stabilize turbidity besides colour [4] and
flavour [5] throughout the turnover period. Due to the
overall high thermal resistance of Citrus pectin methylesterase
(PE; EC 3.1.1.11) resulting from thermally stable
isoenzymes [6], high-temperature-short-time procedures
aim at PE deactivation [7] to prevent cloud loss, but alter
the juice aroma [8].
On the other hand, freshly squeezed fruit juices, chiefly
from orange, have gained significant importance [9].
Constituting premium products in an upper price segment,
they feature a healthy product image due to their natural,
fresh aroma [10] that is retained for a while by minimal
processing without pasteurization, addition of preservatives
or dilution from concentrates. Their freshness implies a
shelf life limited to 10–14 days and the application of
perfect sanitation standards throughout processing and