Yellowstripe Scad (Selaroides leptolepis)
3. RESULTS AND DISCUSSION 1 Yield
Yield of powdered hydrolysate showed the efficiency of hydrolysis time against the production of yield. Figure 1 shows that the yield obtained increased from 1h of hydrolysis to 4h of hydrolysis. The result showed that the protein yield increased rapidly from first hour to the second hour but slowly increase from second to forth hour of hydrolysis. The decrease in rate could be decrease in substrate concentration. Liaset et
reaction at the end of reaction might be due to decrease in enzyme activity, substrate saturation or product inhibition. Gbogouri et al. (2004) and Guerard et al. (2002) observed the same phenomenon using Alcalase enzymein extracting salmon byproduct and tuna waste, respectively.
Figure 1: Percentage yield obtained from hydrolysis
3.2 Degree of hydrolysis (DH)
Degree of hydrolysis (DH) plays a vital role in determining important properties of a protein hydrolysate. Figure 2 showed that DH increased from 1 h to 2 h of hydrolysis but decreases in third and forth hour. However, previous studies by Norma et al. (2005) and Guerard et al. (2002) reported that DH increased as incubation time and enzyme-substrate ratio increased on threadfin bream and yellowfin tuna, respectively.
The decrease in third and forth hour of hydrolysis might be due to reduction of enzyme activities due to exhaustion the enzyme as substrate as time prolonged. Claver and Huiming (2005) also reported that the decrease in DH could be due to denaturation of protein molecules, subsequently reduces its biological activities. Degree of hydrolysis is also dependent on the availability of susceptible peptide bonds on which primary attack is based and the physical structure of the protein molecule (Kanu et al, 2009).
14,0 14,2 14,4 14,6 14,8 15,0 15,2 15,4 15,6 15,8 16,0
1 2 3 4
Percentage (%)
Time of hydrolysis (hours)
50 60 70 80
ge (%)
Protein content obtained was mostly referring to the nitrogen compound found in the sample. The nitrogen content reflects the yield of protein that can be recovered from the hydrolysis process. The protein content of the hydrolysates was found to have an increasing trend from 1h to 4 h of hydrolysis as shown in Figure 3. In previous study, the highest protein recovery found at 4 hour of hydrolysis was superior to those reported by Gbogouri et al. (2004), Ovissipour et al. (2009) and Shahidi et al. (1995).
Figure 3. Protein content that can be recovered from hydrolysis
3.4 Colour
The colour of powdered hydrolysate was determined using colorimeter where the value L* indicates the lightness, a* indicates the redness and greenness and b* indicates the yellowness and blueness. Figure 4 elucidates the value for L*, a* and b* which has no drastic increment or reduction. Dark coloured contributed by slight negative a* value might be contributed by oxidation process. The darkening resulted from oxidation of myoglobin and melanin pigment of the raw material (Benjakul & Morrisey 1997).
Besides, the process of lipid oxidation upon reaction with basic groups in proteins via Maillard reaction, also produces brown pigments from aldol condensation of carbonyls (Van Boekel, 1998).
Figure 4. Colour of powdered protein hydrolysate 0
5 10 15 20 25 30 35
1 2 3 4
Percentage (%)
Time of hydrolysis (hours)
-20,00 0,00 20,00 40,00 60,00 80,00 100,00
1 2 3 4
Reading
Time of hydrolysis (hours)
L*
a*
b*
The study clearly shows that 2 h of hydrolysis is more preferable since it has the highest degree of hydrolysis (69%) which gives better functional properties of the protein hydrolysate for further analysis. The yield, protein recovery and colour were among the results with no notable increment or reduction.
ACKNOWLEDGEMENT
Deepest appreciation to the Ministry of Higher Education (FRGS grant –Vot 59372) for financial support and UMT for lab facilities.
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