Antioxidant and antibacterial activities of modified crab shell bioactive peptides by Maillard reaction

Figures & data

Figure 1. T-AOC activity of MRPs generated from CSBPs and different reducing sugars. CSBPs: crab shell bioactive peptides; TDPs: thermal degradation products. Bars represent the standard deviation. Different lowercase letters represent the significant differences (p< 0.05).

Figure 2. Browning index of the MRPs generated from CSBPs and fructose. All samples were diluted eight times with demonized water and measured at 420 nm. Bars represent the standard deviation.

Figure 3. Antioxidant activities of the MRPs generated from CSBPs and fructose. Bars represent the standard deviation.

Table 2. The correlation coefficient between MRP properties and pH at different fructose concentration.

Correlation coefficient		5 mg/mL	10 mg/mL	20 mg/mL	40 mg/mL
Browning index		0.939*	0.959**	0.891*	0.841
DPPH radical scavenging activity		0.989**	0.986**	0.967**	0.978**
Hydroxyl radical scavenging activity		0.967**	0.834	0.89*	0.937*
Reducing power		0.973**	0.958*	0.934*	0.910*
Molecular weight	2–5 kDa	0.951*	0.992**	0.983**	0.985**
	1–2 kDa	0.636	−0.241	−0.532	−0.924*
	0.5–1 kDa	−0.985**	−0.977**	−0.982**	−0.984**
	<0.5 kDa	−0.979**	−0.979**	−0.986**	−0.998**

Table 3. The correlation coefficient between MRP properties and fructose concentration at different pH.

Correlation coefficient		pH8	pH9	pH10	pH11	pH12
Browning index		0.471	0.376	0.978*	0.929	0.992**
DPPH radical scavenging activity		0.75	0.889	0.994**	0.949	0.957*
Hydroxyl radical scavenging activity		−1.44	0.7	0.993**	0.994**	0.892
Reducing power		0.431	0.867	0.992**	0.996**	1.000**
Molecular weight	2–5 kDa	0.965*	0.668	0.868	0.933	0.945
	1–2 kDa	0.715	0.536	0.353	−0.694	−0.94
	0.5–1 kDa	−0.800	−0.891	−0.635	−0.867	−0.952*
	<0.5 kDa	−0.858	−0.898	−0.852	−0.897	−0.935

Table 1. Antibacterial activity of CSBPs, TDPs, and MRPs.

Strain	Gram	Inhibition zone (mm)									Correlation coefficients
		CSBPs	TDPs	1	2	3	4	5	6	7
Escherichia coli (ATCC25922)	-	nt	nt	+	+	++	+++	++++	+++	++++	0.967**
Vibrio Parahaemolyticus (ATCC17802)	-	nt	nt	+	+	++	+++	++++	+++	++++	0.963**
Listeria monocytogenes (ATCC19115)	+	nt	nt	+	+	+	++	++	++	+++	0.972**
Staphylococcus aureus (ATCC25923)	+	nt	nt	+	+	+	++	++	++	+++	0.971**

Tips: Inhibition zone: ++++ >15 mm, +++ 10–15 mm, ++ 7–10 mm, + <7 mm, nt: not detected. The MRPs which generated at the condition of 40 mg/mL fructose concentration and pH range of 8–12 were indicated by 1, 2, 3, 4, and 5. 6: 10 mg/mL ampicillin, 7: 20 mg/mL ampicillin. ** means significant difference at p< 0.01.

Figure 4. Total free amino acid concentration of the MRPs generated from CSBPs and fructose. Bars represent the standard deviation.

Figure 5. The molecular weight distribution of the MRPs generated from CSBPs and fructose. Size exclusion chromatograms using a TSKgel G2000SWXL column at a flow rate of 1.0 mL/min of pH 7.2 sodium phosphate buffer (0.02 M) containing 0.25 M NaCl. Molecular weight distributions of the CSBPs, TDPs, and MRPs were calculated according to the calibration curve. Bars represent the standard deviation.

Figure 6. Antioxidant activities of the MRPs with different molecular weight.

Table 4. Correlation analysis among different properties of MRPs at a fructose concentration of 40 mg/mL.

Parent parameter	Partner of correlation	Correlation coefficients
DPPH radical scavenging activity	Hydroxyl radical scavenging activity	0.974**
	Reducing power	0.898*
Hydroxyl radical scavenging activity	Reducing power	0.927*
Antioxidant activity ^a	Browning index	0.879*
	2–5 kDa product content	0.963**
	Antibacterial activity	0.984*
Antibacterial activity ^b	Browning index	0.919*
	2–5 kDa product content	0.994**
Browning index	2–5 kDa product content	0.911*

Tips: ^aThe antioxidant activity used for correlation analysis was the hydroxyl radical scavenging activity. ^bThe antibacterial activity used for correlation analysis was an antibacterial activity to Escherichia coli. * means significant difference at p< 0.05. ** means significant difference at p< 0.01.