In the framework of
searching for new pectin sources to partially compensate for domestic and
regional demands, the peel (albedo) of the “non-comestible” fruit of Poncirus trifoliata was investigated
using a relatively simple experimental design for optimization, in which only
the variable was the extraction pH (1.0, 1.5, and 2.0) on the basis of our
previous studies on diverse pectin sources. The results showed that the yield
of pectin (7.4%-19.8%) was strongly influenced by the extraction pH when
the other parameters, namely the solid to liquid extractant (S/L) ratio,
temperature (T °C), and time (t) were fixed to 1:25 (w/v), 75°C, and 90 min, respectively. Likewise, the
galacturonic acid content (GalA: 61.4%-79.2%), total neutral sugar content
(TNS: 9.1%-22.5%), degree of branching (3.5%-13.9%), homogalacturonan (HG)
to rhamnogalacturonan-I (RG-I) ratio (2.2-5.6), degree of methylesterification
(DM: 54-77), viscosity average molecular weight (Mν: 57-82), and gelling capacity (GC: 124-158) were all affected by the extraction pH. The optimum pH for producing pectin
with good yield, quality characteristics (GalA > 65%, DM > 60, Mν > 80 kDa), and gelling capacity (GC > 150), from the peel of P. trifoliata fruit, was found to be pH
1.5.