32
4.2.7 Total Residual Sulfites
Results of total residual sulfites in dried bamboo shoots were shown in Figure 19. It was observed that residual sulfites contained in the final products was highly significant
affected p0.01 by both factors, the concentration of sodium metabisulfite and the drying temperature, and their interactions. As expected, the residual sulfites increased with increase
in concentration of sodium metabisulfite used in blanching solution. The residual level of sulfites in dried sulfited samples ranged from 1250.08 to 3377.94 ppm, calculated as
SO
2
. The highest residual level of sulfites was found in sample blanched in 1.5 sodium
metabisulfite solution and then dried at 70 ⁰C. Thailand FDA has regulated that maximum
sulfites contained in dried fruits and vegetables is 2500 ppm SO
2
. In the regulation, the dried fruits and vegetables may consumed directly without any futher processing. Although almost
samples blanched in sodium metabisulfite solution had residual level of sulfites less than 2500 ppm SO
2
, it should noted that the dried bamboo shoot need to be rehydrated or even cooked before consuming. According to General standard for food additives GSFA, dried
vegetables which may contain up to 5000 ppm sulfites are usually rehydrated and cooked before consumption resulting in much lower concentrations of sulfite in the food at the time
of consumption WHO 1999.
Figure 19. Mean total residual sulfites in dried bamboo shoots
4.2.8 Best Sample
Total weighted scores of dried bamboo shoots were shown in Table 12. Referred to Appendix 37, there were some attributes considered to choose the best sample, i.e. L,a, and
b values of both dried and rehydrated bamboo shoots; rehydration ratio; dimentional changes shrinkage; and firmness of both dried and rehydrated bamboo shoots. The highest
total weighted score was found in the sample blanched in 1.5 sodium metabisulfite solution and then dried at 70
⁰C. Yet, all samples blanched in 1.5 sodium metabisulfite solution had total residual sulfite more than 2500 ppm SO
2
. Thailand FDA has regulated that the
33 maximum level of sulfites contained in dried fruits and vegetables is 2500 ppm, calculated as
SO
2
. The sample did not meet the requirement, thus it can not choose to be the best sample. The 2
nd
highest total weighted score was found in the sample blanched in 1.0 sodium metabisulfite solution and then dried at 60
⁰C. The sample had total residual sulfites less than 2500 ppm SO
2
, thus it can be inferred that the sample met the criterion of the best sample.
Table 12. Total weighted scores of dried bamboo shoots
[Na
2
S
2
O
5
] T
⁰C 50
60 70
41.41 55.15
52.84 0.5
51.80 54.80
59.93 1.0
47.45 64.63
63.15 1.5
55.63 63.94
70.13 Due to some overlapped standard deviations, the firmness of bamboo shoots may not
be considered to determine the best sample. Referred to Appendix 38, regardless of the firmness of dried and rehydrated bamboo shoots, a similar tendency was observed. The
highest total weighted score was found in the sample blanched in 1.5 sodium metabisulfite solution and then dried at 50
⁰C and followed by the sample blanched in the sample blanched in 1.5 sodium metabisulfite solution and then dried at 60
⁰C and the sample blanched in the sample blanched in 1.0 sodium metabisulfite solution and then dried at 60
⁰C. It was also inferred that the sample blanched in the sample blanched in 1.0 sodium metabisulfite
solution and then dried at 60 ⁰C met the criterion of the best sample, regardless of the
firmness attribute.
4.2.9 Sensory Analysis of The Best Sample of Bamboo Shoot
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