In order to determine the combined effect of different factors on tomato waste, optimization experiments were conducted (Table 4.1). The dried tomato material after being dried were extracted with ethyl acetate at 50oC for 90 min. Lycopene content and antioxidant capacity of the extract were shown in Table 4.1.
Table 4.1. Results of optimization treatment regimens for tomato waste Treatment Temperature
(X1) (oC)
Moisture content (X2)
(%)
Lycopene content * (mg/g DW)
Antioxidant capacity (àmol
TE/ g DW)
T8 70 23 9.50± 0.56 8.35± 0.54
T9 70 7 4.81± 1.11 4.39± 0.24
T10 60 15 5.05± 0.17 5.78± 0.35
T11 50 23 8.42± 0.35 7.84± 0.31
T12 50 7 3.77± 0.043 4.26± 0.10
*Mean ± SE
Results in Table 4.1 reveal that the lycopene contents obtained at different treatment regimens range from 3.77 to 9.5 mg/g DW. The highest value
obtained when material was dried at 70oC until the moisture content reached 23% (T8), followed by the value obtained at 50 oC and 23% moisture content (T11). When the material was dried till low moisture content of 7% the lycopene in the extract reached lowest value (T9, T12). These results could be explained by the fact that during long time drying the waste from 85% to 7%
moisture content, lycopene was degraded due to exposing to temperature and oxygen (Shi and Marguer, 2000).
In order to evaluate the effect of two experimental factors to lycopene content (Y1) and antioxidant capacity (Y2) and to obtain the desirability value at various treatment regimens, the experimental results were analyzed by JMP 12.0 software. The experimental results were fitted to the polynomial equation:
Y = b0 + b1.X1 + b2.X2 + b12.X1.X2
After analyzing by JMP 12.0 software, the interactions of the experimental factor on lycopene content and antioxidant capacity were presented in the Table 4.2.
Table 4.2. Summary of effect of independent factors to the output variables
Source LogWorth PValue
X2 8.114 0.00000
X1 0.882 0.13112
X1*X2 0.229 0.58966
X1: temperature oC; X2: moisture %.
Table 4.3. Results of the analysis of variance on lycopene content
Term Estimate Std Error t Ratio Prob>|t|
Intercept -1.250812 2.114759 -0.59 0.5625
X1 0.0529977 0.033306 1.59 0.1311
X2 0.2919715 0.041633 7.01 <.0001*
X1*X2 0.0001461 0.004163 0.04 0.9724
X1: temperature oC; X2: moisture %.
According to data given in Table 4.2, there was different effect between temperature (X1)moisture (X2) and interaction of X1*X2. Among them, moisture content (X2) had a significantly effect on lycopene content and antioxidant capacity as p-value << α=0.05. While the temperature (X1) and the interaction of X1*X2 did not give clear effect on lycopene content and antioxidant capacity.
Table 4.3 showed that there was clear effect of X2-moisture content of the material after drying on lycopene content while X1 and the interaction of X1*X2
were not significantly influenced on lycopene content. The estimate coefficient of X2 was positive (+2.91) that means the higher the moisture content, the more lycopene content obtained. However, if the moisture is too high, it is proned to be spoiled due to microbial proliferation (Kaur et al., 2008). Nobre et al. (2009) also reported that an increase in the moisture content of the sample, from 4.6% to 22.8% led to a rise in the lycopene extraction yield. Most probably, the decrease in trans-lycopene content of the dried sample could be due to physical changes in the structure of the skins (Brunner, 1994); namely, lipid pillars of a plant cell elementary membrane change with the water content and if there is not enough water in the system the pillar closes the membrane making it impermeable (Brunner, 1994).
From the fitting results, the linear equation relationship between lycopene content and the independence variables is derived:
Y1 = -1.251+ 0.053X1 + 0.292X2 + 0.0001X1*X2
Where: Y1 is lycopene content (mg/g DW)
Similarly, Table 4.4 presents the results of the analysis of variance on antioxidant capacity. It can be seen that the moisture content (X2) significantly affected the antioxidant capacity at α =0.05, while X1 and interaction of X1*X2
were not significantly effect on antioxidant capacity of lycopene in the extract. The estimate coefficient of X2 was positive (+0.23) that mean if the higher the moisture content, the more antioxidant capacity of lycopene in the extract obtained. This result are consistent to theory that lycopene is among the most efficient sighlet oxygen quenchers of the natural carotenoids (Shi and Maguer, 2000).
Table 4.4. Result of the analysis of variance antioxidant capacity of lycopene extract
Term Estimates Std Error t Ratio p - value
Intercept 1.6299541 1.092553 1.49 0.1552
X1 0.0160314 0.017207 0.93 0.3653
X2 0.235459 0.021509 10.95 <0.0001*
X1*X2 0.0011838 0.002151 0.55 0.5897
X1: temperature oC; X2: moisture %.
From the fitting results, the linear equation relationship between antioxidant capacity and the independence variables is derived:
Y2 = 1.63+ 0.016.X1 + 0.235.X2 + 0.001.X1*X2
Where Y2 is antioxidant capacity (àmol TE/ g DW)
In order to determine the optimal values for two factors, the desirability was optimized using prediction profiler. The results are presented in Figures 4.5A and 4.3B.
A
Figure 4.3. Profiler showing the optimal drying conditions of tomato waste The results in Figure 4.3 A show that the highest values of lycopene content and antioxidant capacity were 9.19 mg/g DW and 8.26 àmol TE/g DW, respectively when tomato waste was dried at 70oC until the moisture content reached 23%. However, according to Shi and Maguer (2000), heat induces isomerization of the trans into cis form. It has also been reported that serious losses of lycopene can occur when the holding time at high temperature is long.
Therefore, in order to balance the lycopene content and lycopene quality, the selected drying-temperature was 65oC and moisture content after drying was 23%. Under this condition, lycopene content in the extract was 8.92 mg/g DW (Figure 4.3B), a bit lower than that at 70oC; however, the lower quantities were not considerable in return for ensuring quality of lycopene and increasing economic efficiency.
The result of optimization showed that moisture content of dried tomato waste was influenced most on lycopene extraction. It is can explain that lycopene was degraded due to exposing temperature, oxygen in a long time (Shi and Maguer, 2000) when dried waste drying waste process was from 85% moisture to
B
7% moisture content. These results are consistent to the find of Favati et al.
(2003) who observed that the lycopene content of dried samples was lower than that of fresh tomato waste sample.
In conclusion, the optimal drying condition for tomato waste which will be used for lycopene extraction are temperature 65oC and moisture content of dried tomato waste of 23%. These conditions were used for the next experiments.