J Food Sci Technol (JanuaryFebruary 2012) 49(1):103109

DOI 10.1007/s13197-011-0324-1

ORIGINAL ARTICLE

Optimization of processing conditions for cyanide content

reduction in fresh bamboo shoot during NaCl treatment
by response surface methodology
Bindu Rana & Pratima Awasthi & B. K. Kumbhar

Revised: 10 May 2010 / Accepted: 13 May 2010 / Published online: 3 June 2011
# Association of Food Scientists & Technologists (India) 2011

Abstracts NaCl treatment was optimized for maximum 11.3 mg/kg on fresh weight basis, which was in good
reduction of cyanide content in raw bamboo (Dendrocala- agreement with predicted and was well below permissible
mus strictus) shoot using response surface methodology limit (500 mg/kg). The reduction of cyanide content was of
with 4 independent variables like concentration of NaCl, 98.3% at optimum level.
thickness of bamboo shoot, amount of NaCl solution and
duration of treatment at 3 levels of each variable. Box- Keywords Bamboo shoot . Cyanide . Sodium chloride .
Behnken design was used to select the levels of variables in Dendrocalamus strictus . Response surface methodology .
experimental runs. Cyanide content ranged between 12.8 Optimization
and 29.6 mg/kg in bamboo shoot after NaCl treatment. The
effect of concentration of NaCl was higher in reducing the
cyanide content followed by thickness of bamboo shoot and Introduction
treatment time in decreasing order. Amount of NaCl
solution did not affect the reduction of cyanide content In search for new sources of food for humans and animals,
significantly. Optimum condition was 2.4% NaCl concen- many wild plants are being investigated as food sources.
tration, 1.25 cm thickness of bamboo shoot, 216 ml of Bamboo is one such uncommon food. It has now achieved the
NaCl solution and 23 min treatment. Corresponding status of an economically most important plant, rightly
cyanide content was 11.2 mg/kg. Experimental verification considered as Green Gold (Dutt 2004). Bamboo shoots are
at optimum condition gave average cyanide content of traditionally consumed more often as fresh vegetable during
their season of availability. Bamboo shoots are used exten-
sively for preparation of pickles, snacks, papads and other
B. Rana (*)
stuff to curries, bhaajis and other preparations with rice
GBPUAT, PANTNAGAR.,
C-2534, New Township, Panipat Refinery, (Kumbhare and Bhargava 2007). The common edible bamboo
Panipat, Haryana 132140, India species in India are Dendrocalamus strictus and Bambosa
e-mail: brana_09@rediffmail.com bambos (Awasthi and Tewari 2008; Pandey and Jharia 2009).
Zhang and Liu (2001) reported that bamboo shoots
P. Awasthi
GBPUAT, PANTNAGAR., Department of Food and Nutrition, contain vitamins C, B6 and B2, and amino acids essential
College of Home, G B Pant University of Agriculture for human nutrition. They also contain minerals (Zn, Co, K,
and Technology, Mn) and plenty of dietary fiber. Sucrose is the most
Pantnagar 263145, India
abundant sugar in bamboo shoot. Bamboo shoots contain
e-mail: pratimawasthi@yahoo.co.in
high proportion of linoleic acid. The major fatty acid in
B. K. Kumbhar bamboo shoots is palmitic acid; glutamic acid and lysine
GBPUAT, PANTNAGAR., Department of Post-harvest Process are the most abundant amino acids in bamboo shoots
and Food Engineering, College of Technology, G B Pant
(Soo-Jung and Sung-Ja 1993).
University of Agriculture and Technology,
Pantnagar 263145, India Bhargava et al. (1996) have reported that bamboo shoot
e-mail: bkkumbhar@rediffmail.com contains appreciable quantities of vitamin C, carbohydrates
104 J Food Sci Technol (JanuaryFebruary 2012) 49(1):103109

and protein. Besides, bamboo shoots of many species also Table 1 Variables and their levels used in the experiments
contain lethal concentration of cyanogenic glucosides, Variables Code level
which on endogenic hydrolysis, yield hydrocyanic acid.
Cooking destroys the enzymes responsible for the endo- 1 0 +1
genic hydrolysis largely. Another constituent of bamboo
NaCl concentration,% X1 1 2 3
shoot, known as homogentistic acid is responsible for the
Thickness, cm X2 1 1.5 2
disagreeable, pungent taste, characteristics of bamboo
Amount of NaCl solution, ml X3 100 200 300
shoots (Ferreira et al. 1991). Freshly harvested bamboo
shoot has a necessity for a precooking processing, primarily Time, min X4 15 20 25
to remove the toxic and bitter components, prior to the
preparation of any dish. The level of cyanogenic glucosides
up to 500 ppm in foods is considered to be of no health NaCl solution  200
X3 3
hazard (Anon 2005; FAO 2005). Soaking in water, sun 100
drying, boiling and steaming are some popular traditional
methods of reducing cyanide content (Coursey 1973).
The present study was carried out to optimize the sodium Time  20
X4 4
chloride (NaCl) treatment for reduction of cyanide content 5
of raw bamboo shoot to the maximum level.
where, X1, X2, X3, X4 are coded values for concentration of
NaCl (%), thickness of bamboo shoot (cm), amount of
Materials and methods NaCl (ml) and duration of treatment (min), respectively.
Coding of variables helps in computational simplicity and
Samples of bamboo (Dendrocalamus strictus) tender shoots brings the independent variables in the same range
were procured from Agro-forestry Research Centre of the irrespective of the actual magnitude of the variables.
university. Bamboo shoots were washed thoroughly with Therefore, the effect of the variables at linear, quadratic
tap water for removal of dust and dirt. Then tip was cut and and interactive level can be deduced using the magnitude of
thick outer sheath was peeled off. Inedible portion of shoot the regression coefficients. Higher the magnitude of the
was removed and finally edible portion of tender bamboo coefficient, higher is the effect of that variable.
shoots were sliced (1, 1.5, 2 cm thick). Sample (25 g) was
taken for the treatment in boiling solution as per the Statistical analysis Cyanide content data were analyzed
experimental conditions. Treatment time was noted after by multiple regressions through the least square method to
temperature of solution reached 100 C. fit the following equation:
Hydrocyanic acid was determined following the test
described by Hogg and Ahlgren (1942). X
4 X
4 3 X
X 4
Y b0 bi Xi bii Xi bij Xi Xj 5
i1 i1 i1 ji1
Experimental design Response surface methodology
(RSM) was used to investigate the influence of treatment where, 0, i, ii, ij are the coefficients of the regression
variables, namely, concentration of NaCl, thickness of equation; i and j, the integers; and Y, the response and X i,
tender bamboo shoot, amount of NaCl and duration of Xj independent variables.
treatment on cyanide content of bamboo shoots. A Box and Adequacy of the model was determined using coefficient
Behnken factorial design with 4 factors each varied at 3 of determination (R2), F value, and lack of fit. Effect of
levels and with 3 centre point replications, was used for variables was deduced from the magnitude and sign of the
experimental design and a second order response surface. regression coefficients. The best-fitted equation was
Tables 1 and 2 show the factors and their levels at which obtained by eliminating the insignificant terms from full
the experiments were carried out. Independent variables second order equation in order to get simple predictive
were coded using the following: equation. The coefficients of the response function, their
statistical significance and process conditions for minimum
NaCl Concentration  2 cyanide content were determined using statistical package
X1 1
1 Design Expert Trial version 7.1.3(Statease Inc., Minne-
apolis, USA) were repeated at optimum condition to asses
the reproducibility and its validity. Surface plots and
Thickness  1:5 contour plots were developed to study the effect of
X2 2
0:5 variables on cyanide content.
J Food Sci Technol (JanuaryFebruary 2012) 49(1):103109 105

Table 2 Experimental design and observed response

Expt. No. Coded (real values) Cyanidea content mg/kg

X1 (NaCl conc,%) X2 (Thickness, cm) X3 (Amount of NaCl, ml) X4 (Time, min)

1 1(1) 1 (1) 0(200) 0 (20) 23.81

2 +1 (3) 1 (1) 0 (200) 0 (20) 17.50
3 1 (1) +1 (2) 0(200) 0 (20) 25.03
4 +1 (3) +1 (2) 0(200) 0 (20) 26.72
5 0 (2) 0 (1.5) 1(100) 1 (15) 20.02
6 0 (2) 0 (1.5) +1(300) 1 (15) 15.31
7 0 (2) 0 (1.5) 1(100) +1 (25) 15.84
8 0 (2) 0 (1.5) +1(300) +1 (25) 14.82
9 0 (2) 0 (1.5) 0(200) 0 (20) 15.43
10 1 (1) 0 (1.5) 0(200) 1 (15) 28.41
11 +1 (3) 0 (1.5) 0(200) 1 (15) 18.22
12 1 (1) 0 (1.5) 0(200) +1 (25) 23.21
13 +1 (3) 0 (1.5) 0(200) +1 (25) 14.91
14 0 (2) 1 (1) 1 (100) 0 (20) 15.73
15 0 (2) +1 (2) 1 (100) 0 (20) 19.46
16 0 (2) 1 (1) +1 (300) 0 (20) 13.53
17 0 (2) +1 (2) +1 (300) 0 (20) 22.52
18 0 (2) 0 (1.5) 0 (200) 0 (20) 12.50
19 0 (2) 1 (1) 0 (200) 1(15) 21.0
20 0 (2) +1 (2) 0 (200) 1(15) 22.50
21 0 (2) 1 (1) 0 (200) +1(25) 13.42
22 0 (2) +1 (2) 0 (200) +1(25) 19.81
23 1 (1) 0 (1.5) 1 (100) 0 (20) 30.03
24 +1 (3) 0 (1.5) 1 (100) 0 (20) 15.61
25 1 (1) 0 (1.5) +1 (300) 0 (20) 25.03
26 +1 (3) 0 (1.5) +1 (300) 0 (20) 12.81
27 0 (2) 0 (1.5) 0 (200) 0 (20) 13.06

a
Value on fresh weight basis

Results and discussion

Table 3 Analysis of variance (ANOVA) for NaCl treatment

The results of cyanide content under various conditions are Source df SS MS F value
given in Table 2. It shows that cyanide content ranged between
Regression
12.5 and 30.0 mg/kg. The lowest cyanide content was at 3%
Model 14 601.13 42.94 6.05
NaCl concentration, 1.5 cm thickness of tender bamboo shoot,
Linear 4 345.17 86.29 12.15**
300 ml of NaCl solution and 20 min duration, while the
Quadratic 4 282.07 70.51 9.93**
highest cyanide content was at 1% NaCl concentration,
1.5 cm thickness of bamboo shoot, 100 ml of NaCl solution Cross product 6 34.56 5.76 0.81ns
and 20 min duration. The cyanide content of the fresh tender Residual 12 85.21 7.10 3.35ns
Lack of fit 10 80.41 8.04
bamboo shoot was 649 mg/kg, which indicated that reduction
Pure error 2 4.81 2.40
in cyanide content varied between 95.4 and 98.1%.
Total effect of factors
Equation 5 was fitted into the response variable cyanide
Concentration 5 418.36 83.67 11.78**
content using least square regression analysis and the results
Thickness 5 174.44 34.88 4.91*
of analysis are given in Table 3. F value suggests that the
Amount of NaCl solution 5 29.69 5.93 0.83ns
model was significant at p<0.0001. Coefficient of determi-
Time 5 73.86 14.77 2.08ns
nation, R2 was 0.8758 suggesting that 87.6% variability in
the data was explained by the model. Moreover, there was F Fishers ratio; df Degrees of freedom; SS Sum of squares; MS Mean
insignificant lack of fit. Therefore, the model was adequate sum of squares; ns not significant; significant at **p0.01, *p0.05
106 J Food Sci Technol (JanuaryFebruary 2012) 49(1):103109

(a) Surface plot

(X3=0.16, X4=0.62)
(a) Surface plot
1.00
(X3=0.16, X4=0.62)
0.80
1.00
0.60
0.80
0.40

X2 (Thickness, cm)
0.60
0.20
0.40
X2 (Thickness, cm)

0.00
0.20
-0.20
0.00
-0.40
-0.20
-0.60
-0.40
-0.80
-0.60
-1.00
-1.00 -0.60 -0.20 0.20 0.60 1.00
-0.80
X1 (Conc of N acl, %)
-1.00 (b) Contour plot
-1.00 -0.60 -0.20 0.20 0.60 1.00

X1 (Conc of Nacl, %) Fig. 2 Interactive effect of NaCl concentration and amount of NaCl
solution on cyanide content (thickness l.25 cm, boiling time 23 min)
(b) Contour plot
Fig. 1 Interactive effect of NaCl concentration and thickness on
cyanide content (amount of NaCl solution 216 ml, boiling time Regression results indicated that the concentration of
23 min) NaCl and thickness of bamboo shoot had significant effect
(p<0.01) on cyanide content while time had significant
effect (p<0.05) at linear level. Amount of NaCl solution did
not affect cyanide content significantly. Concentration of
to predict the response and interpret the effect of variables on NaCl, amount of NaCl solution and treatment time had
the response. The standard of estimate of the coefficients for negative effect i.e. increase in the level of these variables
the variables at linear, quadratic and interactive level was decreased the cyanide content while the thickness of
0.79, 1.154 and 1.332, respectively. The model obtained for bamboo shoot showed positive effect i.e. increase in level
cyanide content (Y) was as follows: of thickness of bamboo shoot decreased reduction in
cyanide content. As the concentration of NaCl increases
Y 13:633  4:141X1 2:583X2  1:050X3 in the solution, the osmotic pressure of the solution
decreases. This facilitates the increased removal of water
 1:958X4 2:000X1 X2 0:550X1 X3 from bamboo shoots and thereby decreases the cyanide
content. Moreover, treatment time affects the diffusion of
0:475X1 X4 1:325X2 X3 1:225X2 X4
solution. Longer the treatment time, higher is the diffusion
0:925X3 X4 6:037X1 2 3:500X2 2 and hence lower is the cyanide content. Thickness of
bamboo shoot of the material increases the resistance to
0:950X3 2 1:812X4 2 6 diffusion and therefore, cyanide content increases. Concen-
J Food Sci Technol (JanuaryFebruary 2012) 49(1):103109 107

(a) Surface plot

(X2= -0.53, X3=0.16)

1.00
(a) Surface plot
0.80
(X1=0.41, X4=0.62)
0.60
1.00
X3 (Amount of Nacl, ml)

0.40
0.80
0.20
0.60
0.00
X3 (Amount of Nacl, ml)
0.40
-0.20
0.20
-0.40
0.00
-0.60
-0.20
-0.80 -0.40
-1.00 -0.60
-1.00 -0.60 -0.20 0.20 0.60 1.00

X1 (Conc of Nacl, %) -0.80

(b) Contour plot -1.00
-1.00 -0.60 -0.20 0.20 0.60 1.00
Fig. 3 Interactive effect of NaCl concentration and time on cyanide
X2 (Thickness, cm)
content (amount of NaCl solution 216 ml, thickness l.25 cm)
(b) Contour plot
Fig. 4 Interactive effect of thickness and amount of NaCl solution on
tration of NaCl and thickness of bamboo shoot affected the cyanide content (NaCl concentration 2.4%, time 23 min)
cyanide content at p<0.01 and p<0.05, respectively at
quadratic level. Amount of NaCl solution and treatment
time did not affect cyanide content quadratically. Interac- Coefficient of determination, R2, was 0.7989 and F value
tions among the variables were not present in the was 13.24 with probability of p=0.000 suggesting predic-
experimental range investigated. tive model was adequate.
The total effect of concentration of NaCl and thickness of
bamboo shoot was significant at p<0.01 and p<0.05, Optimization of the process variables Design Expert (v
respectively while the effect of amount of NaCl solution 7.1.3) software was employed to minimize cyanide content
and time was nonsignificant. The total effect of variables was by NaCl treatment using numerical method of optimization.
significant at p<0.01 at linear and quadratic level (Table 3). The optimum obtained was at 2.4% NaCl concentration,
The insignificant terms were eliminated from the full 1.25 cm thickness of bamboo shoot; 216 ml NaCl solution
second order model to get simplified predictive equation. and treatment time 23 min at 100 C. The cyanide content
The result of regression analysis was as follows: predicted was 11.2 mg/kg at optimum point. This was
verified by conducting 3 replications at optimum point and
Y 15:475  4:141X1 2:583X2  1:050X3 it was observed that cyanide content ranged between 11.28
and 11.33 mg/kg. Two experiments were also conducted at
 1:958X4 5:346X1 2 2:809X2 2 7 variable concentrations of NaCl (2.4 and 2.5%), thickness
108 J Food Sci Technol (JanuaryFebruary 2012) 49(1):103109

(a) Surface plot

(x1=0.41, x2=-0.53)
(a) Surface plot 1.00
(X1=0.41 , X4=0.62) 0.80
1.00
0.60
0.80
0.40

X4 (Time, min)
0.60
0.20
0.40
0.00
X4 (Time,min)

0.20 -0.20
0.00 -0.40

-0.20 -0.60

-0.40 -0.80

-0.60 -1.00
-1.00 -0.60 -0.20 0.20 0.60 1.00
-0.80 X3 (Amount of NaCl, ml)

-1.00 (b) Contour plot

-1.00 -0.60 -0.20 0.20 0.60 1.00
Fig. 6 Interactive effect of amount of NaCl solution and time on
X2 (Thickness,cm )
cyanide content (concentration of NaCl 2.4%, thickness 1.25 cm)
(b) Contour plot
Fig. 5 Interactive effect of thickness and time on cyanide content
(concentration of NaCl 2.4%, amount of NaCl solution 216 ml)
concentration of NaCl. It can be also seen that cyanide
content was higher at higher and lower levels of both
concentration of NaCl and thickness of bamboo shoot as
of bamboo shoot (1.25 and 1.05 cm), amount of NaCl (260 well as at low level of concentration of NaCl and higher
and 250 ml), and time (20 and 21 min). The resultant thickness of bamboo shoot. Effect of concentration of NaCl
cyanide contents were 11.8 and 11.5 mg/kg, respectively. and amount of NaCl was also depicted (Fig. 2) that the least
This validates the optimum condition. cyanide content was obtained at 2.4% NaCl and 216 ml of
NaCl solution. The cyanide content of about 13 mg/kg can
Interactive effects of variables on reduction of cyanide be obtained over wide range of NaCl concentration. The
content Three dimensional surface plots and contour plots amount of solution had a little effect on the cyanide content.
were developed between two variables using full second In Fig. 3, the minimum cyanide content was observed at
order model and keeping other variables at optimum to 2.4% NaCl concentration and 23 min of treatment time.
show the effects of variables on cyanide content. The effect of NaCl concentration and treatment time was
more pronounced at higher levels. The interactive effect of
Effect of concentration of NaCl and thickness of bamboo thickness of bamboo shoot and amount of NaCl showed
shoot on cyanide content showed (Fig. 1) that the cyanide (Fig. 4) that the cyanide content increased with increase in
content decreased as concentration of NaCl increased up to thickness of bamboo shoot. The minimum cyanide content
2.4% and then decreased. However, thickness of bamboo was obtained at 1.25 cm thickness of bamboo shoot and
shoot had slight effect on the cyanide content up to 2% 216 ml of NaCl. However, there was no significant effect of
J Food Sci Technol (JanuaryFebruary 2012) 49(1):103109 109

amount of NaCl content. The effect of thickness of bamboo conditions may be very effective to make tender bamboo
shoot was more pronounced at their higher values. shoots suitable for human consumption.
The interactive effect of treatment time and thickness of
bamboo shoot showed (Fig. 5) that the minimum cyanide
content (11.2 mg/kg) was obtained at 23 min treatment and References
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