20
Table 5. Treatment combinations
Factors N
N
1
N
2
N
3
T
1
T
1
N T
1
N
1
T
1
N
2
T
1
N
3
T
2
T
2
N T
2
N
1
T
2
N
2
T
2
N
3
T
3
T
3
N T
3
N
1
T
3
N
2
T
3
N
3
General model of the experimental design as follows:
Y =
μ
+
α
+
β
+
αβ
+
ε where:
Y
ijk
= response for treatment of concentration of sodium metabisulfite at level i, drying temperature of at level j, and replicate k
μ = average value
α
i
= treatment effect of concentration of sodium metabisulfite at level i β
j
= treatment effect of drying temperature at level j αβ
ij
= interaction between drying temperature at level i and concentration of sodium metabisulfite at level j
ε
ijk
= error
3.3.4 Statistical Analysis
SPSS 16.0 was used for data analyses. Effects of drying temperature, concentration of sodium metabisulfite, and their interaction on water activity, color, rehidration ratio,
firmness, and total residual sulfites of dried and rehydrated bamboo shoots were analyzed using ANOVA Generalized Linear Model at 95 confidence level and the further test
multiple comparison test would also be done using Duncan test at 95 confidence level Meilgaard et al. 2007. Results of sensory evaluation for color, aroma, texture, taste, and
overall preference of rehydrated bamboo shoots were analyzed using t-Test: two-sample assuming equal variances at 95 confidence level Meilgaard et al. 2007.
IV. RESULTS AND DISCUSSION
4.1 PRELIMINARY RESEARCH
Prior to main research, it was necessary to do some adjustment of process conditions. Some steps in this research were done with different methods. In addition, at this stage, it was also
determined drying time for bamboo shoots which were dried at the lowest temperature, i.e. 50 ⁰C.
Bamboo shoots used at this stage, as shown in Figure 9, were purchased in Chiang Mai. They are different with bamboo shoots used in main research, Dendrocalamus membranaceus Munro which
grows in the Doi Tung forest has not been able to be harvested during this stage.
Figure 9. Fresh bamboo shoots purchased in Chiang Mai
There are difficulties to handle bamboo shoots, besides many sheaths of overlapping protect bamboo shoots, it should be noted that they can be stored just for one day at ambient
temperature, thus there were two choices, either they were processed at the same day they were harvested or stored in the refrigerator 1-2
⁰C. Prior to both choices, bamboo shoots needed to peel for reducing their bulkiness and removing dirts on the sheaths. Moreover, there was
adjustment for peeling technique. Bamboo shoots should be peeled well. Thickness of peeled sheaths may influence final products. If they were not peeled well, there still remained sheaths
after drying, as shown in Figure 10. Thus, it needed to improve the peeling technique, due regard to yield obtained. After some experiments, it was obtained a good technique for applying in main
research, i.e. bamboo shoots were partially slashed from the bottom to the top of shoots and then the remaining sheaths were peeled in a counterclockwise motion into conical shape. Bamboo
shoots that were not directly processed, just peeled the outer sheaths and then packed in plastic bags before storing in the refrigerator.
