Synergistic action of <sup>60</sup>Co-γ irradiation on quality preservation of fresh-cut lotus root: microbial control and targeted polyphenol oxidase suppression

Figures (5) Tables (3)

Figure 1.
Effects of irradiation on microbial contamination of fresh-cut lotus root during storage.
Figure 2.
Pictures of fresh-cut lotus root subjected to ⁶⁰Co-γ irradiation at 1, 2, and 3 kGy during storage.
Figure 3.
The dynamic changes of total phenolic compounds, and soluble quinone content of lotus root slices subjected to irradiation during storage.
Figure 4.
The PPO activity, and relative gene expression of PPO of lotus root slice samples with and without irradiation. ** Represents significant different between treatments (p < 0.05).
Figure 5.
Fluorescence spectra of PPO with and without ⁶⁰Co-γ irradiation.

Parameters	Storage time (d)	Treatments
Parameters	Storage time (d)	Control	1 kGy	2 kGy	3 kGy
Color (L^*)	0	50.91 ± 1.99^b	50.21 ± 0.85^a	50.98 ± 0.77^b	50.13 ± 1.58^ab
	3	41.81 ± 1.32^a	40.48 ± 1.07^b	40.34 ± 1.41^b	40.68 ± 0.78^b
	5	40.02 ± 1.94^a	38.98 ± 2.00^a	39.70 ± 2.08^a	40.23 ± 2.00^a
	9	31.70 ± 1.85^c	32.14 ± 1.60^c	35.62 ± 2.66^b	38.98 ± 2.28^a
Color (ΔE)	0	45.51 ± 1.61^a	44.08 ± 1.80^a	45.46 ± 1.73^a	44.48 ± 1.89^a
	3	47.74 ± 1.33^a	46.67 ± 0.89^b	46.6 ± 1.11^b	46.33 ± 0.63^b
	5	54.67 ± 1.86c	56.96 ± 0.84a	54.98 ± 0.68bc	56.1 ± 1.49ab
	9	44.28 ± 2.07a	36.64 ± 1.94c	40.19 ± 2.73b	35.88 ± 2.07c
Browning Index (BI)	0	4.87 ± 0.80^a	4.87 ± 1.28^a	4.80 ± 1.12^a	4.83 ± 1.15^a
	3	8.94 ± 2.59^c	7.19 ± 0.73^b	6.68 ± 0.92^ab	6.38 ± 1.62^a
	5	14.07 ± 2.07^c	7.37 ± 0.31^a	7.13 ± 0.82^ab	6.91 ± 2.06^b
	9	15.57 ± 2.73^a	10.88 ± 0.48^c	9.84 ± 0.52^c	7.98 ± 0.67^b
Different letters in the same row indicate significant difference (p < 0.05).

Table 1.

Changes in color and browning index of fresh-cut lotus root during storage.

Parameters	Storage time (d)	Treatments (U/g FW)
Parameters	Storage time (d)	Control	1 kGy	2 kGy	3 kGy
PAL activity	0	6.05 ± 0.67^a	6.65 ± 0.57^a	6.15 ± 1.32^a	6.45 ± 2.89^a
	3	10.71 ± 0.06^a	10.89 ± 1.30^a	9.09 ± 1.22^a	9.21 ± 1.65^a
	5	10.42 ± 0.71^a	12.02 ± 0.73^b	9.97 ± 0.24^a	10.58 ± 0.29^a
	9	9.46 ± 0.68^a	9.23 ± 0.57^a	9.75 ± 1.86^a	9.98 ± 0.72^a
POD activity	0	39.77 ± 5.38^a	39.91 ± 3.30^a	38.23 ± 3.27^a	38.76 ± 4.19^a
	3	56.84 ± 8.71^a	54.75 ± 1.86^a	56.38 ± 1.95^a	53.49 ± 1.13^a
	5	53.48 ± 1.13^a	59.51 ± 9.73^b	59.70 ± 8.11^b	53.48 ± 4.36^a
	9	51.47 ± 2.10^a	55.62 ± 0.97^a	53.16 ± 5.62^a	54.89 ± 8.75^a
Different letters in the same row indicate significant difference (p < 0.05).

Table 2.

The activities of PAL and POD in lotus roots slices subjected to different doses of ⁶⁰Co-γ irradiation during storage.

Treatment	α-Helix (%)	β-Sheet (%)	β-Corner (%)	Random coil (%)
Control	35.4 ± 0.4^a	20.6 ± 0.5^a	14.0 ± 0.1^a	30.1 ± 0.9^a
3 kGy	18.4 ± 0.2^b	28.5 ± 0.1^b	14.2 ± 0.1^a	39.0 ± 0.3^b
The different letters in the same row means significant difference (p < 0.05).

Table 3.

Effect of ⁶⁰Co-γ irradiation on the percentage content of lotus PPO secondary structures.