Figure 5 Yeasts (log Ufc g
)1
) of minimally processed Barattiere melon
dipped in ascorbic acid (1%) and calcium chloride (0.2%) and
packaged with the different films. Each value is the mean of two
replicates and the vertical bars indicate standard deviation. The curves
were drawn with the sole aim of highlighting data trends.
latter evidence suggested that the recorded differences in
microbial growth cannot be ascribed to change in pH.
Mass loss
Figure 6 shows the percentage mass loss of the packaged
fresh-cut produce over a two-weeks storage period.
Curves shown in the figure were drawn with the sole aim
of highlighting the trend of experimental data. Mass loss
for dipped and untreated melon packaged in the two
biodegradable films was markedly higher than that
observed for MLF and OPP (Fig. 6). A cluster analysis
was run to assess if the above-mentioned differences 15
were statistically significant. The statistical approach
showed that dehydration kinetics between biodegradable
and no biodegradable films are statistically different.
In fact, the analysis classified all samples in two
different groups: one included melon packaged with
both OPP and MLF, the other melon packaged with
both NVT1 and NVT2. These results can be ascribed to
the different water permeability coefficients of the films
under study. As reported in the literature, the water
permeability coefficient is equal to the product of the
water diffusion coefficient and the water solubility
coefficient. The former is related with the macromolecular
mobility of the diffusing phase (polymeric film),
whereas the latter depends on the affinity between water
and diffusing media (Del Nobile et al., 1997). OPP film
possessed a high macromolecular mobility and a low
affinity to water molecules. In contrast, the biodegradable
films used in this investigation have been shown to
possess lower macromolecular mobility and higher
affinity to water, compared to OPP. Therefore, OPP
showed higher barrier properties to water than both
NVT1 and NVT2, whereas the opposite was true with
gas barrier properties. As reported above, MLF used in
this study was made up of a multi-layer structure
composed of a nylon layer and a polyolefin layer.
Therefore, it had high barrier properties to gas due to
the nylon layer, and high barrier properties to water,
due to the polyolefin layer. As expected, the pretreatment
adopted in this study did not greatly modify
the mass loss kinetic of the investigated produce. In fact,
the statistical analysis showed no differences between
dipped and untreated melons for all the packaging films
used in this study.