20/ J. Agrobiotech.
Vol. 8 (1), 2017, p. 13–24.
The smaller molecules are more easily trapped inside the ice structure and larger molecules are less like
to be present in the ice fraction (Chen
et al., 2000). Thus, protein remains higher in concentrate of coconut water.
The increase in protein content by freeze-concentrated of tofu whey can be observed in the findings from Belén
et al. (2013).
Crude fat content in the coconut water increased in value as the maturity increases. The coconut water
fat portion encompasses the jelly-like meat, thus the closer the coconut to the stage of meat formation the higher
the fat content (Jackson
et al., 2004). The increase in the crude fat content of the freeze-concentrated coconut
water may be due to the larger molecules of fat are less likely to be included in ice fraction and caused it to be
accumulated at the concentrate juice in a way that could be similar to the way in which protein molecules.
TPC in GC was significantly higher (
P<0.05) than MC, while freeze-concentrated coconut waters
showed significantly higher (
P<0.05) TPC than fresh coconut waters, which were about 2-fold higher, regardless
of the maturity. The higher TPC content in freeze-concentrated coconut water could be associated to the
availability of phenolics compound in coconut water that might be trapped inside
the concentrate during the
processing. Formation of ice crystal during the freezing process might cause the phenolics compound to become
partially insoluble in water and remain in a higher amount in the concentrate. Consequently, coconut water with
higher concentration of antioxidant content was successfully produced through the freeze-concentration process.
This result tallies with the findings of increase in TPC in concentrated pineapple
juice by using osmotic
evaporation (Hongvaleerat
et al., 2008) and reverse osmosis (Couto
et al., 2011), as well as in wild elderberry juice
concentrated juice (Gali
et al., 2009).
The major sugars that contribute to the sweetness of
the coconut water are glucose, fructose, and
sucrose (Campbell-Falck
et al., 2000; Tan
et al., 2014). The reducing sugars (
i.e. fructose and glucose) were high,
while the non-reducing sugar (
i.e. sucrose) was low in GC (Table 1). Significant increase (
P<0.05) in sucrose
content in parallel to the significant decrease (
P<0.05) of glucose and fructose were observed when comparing
between GC and MC. These changes of sugars content might be due to the expense of fructose and glucose to
form sucrose (Tan
et al., 2014).
There is a significant increase (
P<0.05) in each of the sugars content after the freeze-concentration
process for both GC and MC. According to Prades
et al. (2012), total sugars content is correlated to the total
soluble solids. Hence, an increment in total sugars content of concentrated coconut water is observed as the total
soluble solids increased. The result is in agreement with the finding by Gali
et al. (2009), who reported that the
increase in reducing sugars of wild elderberry juice after being concentrated. The increase in the sugars content
might be due to the concentration process, whereby the sugar molecules are likely to remain in the concentrate
after the water removal by physical mean.
Minerals are the second most constituents in coconut water, with K as the predominant mineral (Yong
et
al., 2009; Solangi and Iqbal, 2011; Tan
et al., 2014). The K content in GC water is significantly higher (
P<0.05)
than MC water, wherein the reverse trend is observed for Mg, Na, Ca, and Fe contents. In general, MC water has
a significantly higher (
P<0.05) mineral content in comparison with GC water. There is a significant difference
(
P<0.05) for all the samples of coconut water after freeze-concentration process. The result is in line with the
findings with increase in P, Mg, K, and Ca contents of the concentrated pineapple juice (Couto
et al., 2011), and
Mg and Na contents in freeze-concentrated tofu whey (Belén
et al., 2013). Interaction between the same
molecules formed clusters during the freeze-concentration process, whereby big molecules were separated from
the ice crystals and possibly remained in high concentration in the coconut water concentrate, resulting in the
increase of minerals concentration. It has been reported that the level of minerals content in the coconut water
depends on their presences in the soil, water irrigation, and the species of coconut cultivars (Solangi and Iqbal,
2011).
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