31 pectin occured. Furthermore, chain aggregation of end linear fibriller to another end linear fibriller
was promoted. An increase in the salt concentration from 0.05 to 0.2 M enhanced low methoxyl pectin aggregation so that the fibriller bound become so close Yoo et al. 2003. Montero and
PèrezMateos 2002 stated that the effect of cations depend on concentration. At low concentration, they appear to have stabilising effect, whereas at very high concentration, they
appear to have opposite effect. This may mean the saturation of anionic groups occurs at certain.
Figure 17. Syneresis graphs of NaHCO
3
addition treatments Marudova and Jilov 2002 pointed out that pectin gel strength and viscoelasticity
decreased in the presence of high concentration ions. It may be happened due to the decrease in crosslinking junctions between the pectin chains. The decrease is most considerable with
increasing salt concentration that is with increasing ionic strength in the solution. By the decrease in crosslinking junctions, the water will be released from the gel. Sodium ion itself has salting out
effects. The presence of the ion inside gel structure can not be dispersed uniformly. Gel parts with high concentration of sodium ion will draw the water from another gel parts to balance the ionic
concentration. It will lead to the competition between hydrocolloid components and salt to get the water.
4. pH Changes
Observation of changes in the pH of green grass jelly was also conducted. The result of this observation can be seen in Appendix 8 and briefly presented on Figure 18. At 0 hour after
steaming, all of green grass jellies’ pH are decreased in comparison with pH before steaming. This is caused by the release of organic acids from the network due to the heating process Gross
1991. Von Elbe and Schwartz 1996 stated that heating could initiate decompartmentalization of cellular acids as well as the synthesis of new acids. In vegetables, several acids have been
identified, including oxalic, malic, citric, acetic, succinic, and pyrrolidone carboxylic acid PCA. Start from 24 hours after steaming, all of green grass jellies’ pH are increased in
comparison with pH at 0 hour after steaming. It might be happened due to the buffering effects of NaHCO
3
. Above 70 °C, sodium bicarbonate gradually decomposes into sodium carbonate, water, and carbon dioxide, resulting the increasing pH Lakhanisky 2002. Furthermore, NaHCO
3
which has been ionized to be Na
+
and HCO
3
in the water is transformed to be H
2
CO
3
and OH reversibly.
y = 0.2394x 0.924 R² = 0.9828
y = 0.1768x 0.273 R² = 0.9800
y = 0.3885x + 0.133 R² = 0.9951
5 5
10 15
20 25
30 35
10 20
30 40
50 60
70 80
S y
n er
es is
Time Hours
0.125 0.583
32 Release of Na
+
will raise the pH. Furthermore, as the concentration of HCO
3
increased, reaction equilibrium is shifted to the right side, increasing the production of OH
. It shall increase the pH. Until at certain concentration, OH present will shift the reaction equilibrium back to the left side,
increasing the production of HCO
3
, decreasing the pH. It can be seen from the pH at 72 hours after steaming. For the treatment without addition of NaHCO
3
, increasing pH was happened due to the partial degradation and βelimination of carboxyl groups in the polysaccharide chains which
also impact to the gel texture. Release of magnesium ion form chlorophyll structures also leads to the increase of pH Saris et al. 2000.
NaHCO
3
addition at the concentrations of 0.125 and 0.583 produced green grass jelly with less fluctuative pH change than without addition of NaHCO
3
. It can be seen from R
2
value at the graph. The largest R
2
value belongs to the NaHCO
3
concentration of 0.583. But, addition of 0.583 NaHCO
3
makes the taste of green grass jelly to bitter. Furthermore, pH of green grass jelly by addition of 0.125 NaHCO
3
after 3 days of storage is not so different with pH of that sample before steaming. In terms of pH changes, the chosen treatment was 0.125 of NaHCO
3
concentration.
Figure 18. Graphs of pH changes by NaHCO
3
addition treatments Based on the taste parameter, the chosen NaHCO
3
concentration were 0 and 0.125 since it could not affect green grass jellies’ taste to be bitter. Based on the color parameter, the chosen
NaHCO
3
concentration was 0.125 because of its lightest, greenest, and yellowest color. This concentration also has the lowest syneresis rate. Based on the pH changes, the most linear one belongs
to the NaHCO
3
concentration of 0.583. But this concentration could not be used since it affects to the bitter taste. From the overall parameters, the chosen concentration of NaHCO
3
was 0.125. This concentration would then be used for the all green grass jelly formula with steaming treatment.
D. DETERMI ATIO OF
