Table 2 Effect of freezing, thawing methods on total color difference value (ΔE) in blanched sweet potato stems with vacuum packaging

Freezing method	Thawing method	Color

		L^*	a^*	b^*	ΔE

Control		40.63±1.77^cde	-3.62±1.53^bcd	9.94±3.34^cd	-

Conventional freezing -20°C	Room temperature	41.72±1.83^abcAx	-3.63±1.11^bcdAx	10.26±2.92^cdBy	3.35±1.63^abc
	Running water	42.39±1.90^aAx	-4.10±1.27^cdeAy	12.19±2.56^abAy	3.85±2.23^ab
	HF1)	40.42±1.78^deBy	-3.72±1.00^bcdAxy	11.16±3.00^bcABy	3.31±1.80^abc
	MW2)	41.74±1.71^abcAx	-3.57±1.38^bcdAxy	11.13±2.30^bcABx	3.28±1.26^abc

Conventional freezing -40°C	Room temperature	41.82±2.11^abcAx	-4.61±1.28^eAy	12.56±2.51^abAx	4.02±2.26^ab
	Running water	41.77±1.77^abcAxy	-4.61±1.24^eAy	13.73±1.80^aAx	4.49±2.03^a
	HF	41.75±1.90^abcAx	-4.33±1.25^deAy	12.98±2.20^aAx	3.97±2.24^ab
	MW	42.07±1.67^abAx	-4.31±1.34^deAy	12.76±3.30^abAx	4.43±2.42^a

Immersion freezing -40°C	Room temperature	40.25±1.60^deABy	-3.35±0.90^bcBx	9.09±1.70^dAy	2.28±1.33^c
	Running water	41.18±1.60^abcdAy	-2.26±0.82^aAx	6.79±1.79^eBz	3.92±1.74^ab
	HF	40.96±1.22^bcdeAxy	-3.27±1.23^bcBx	8.60±2.22^dAz	2.86±1.21^bc
	MW	39.78±1.75^eBy	-2.88±0.91^abBx	8.54±2.04^dAy	2.98±1.46^bc

^a-eMeans with different superscripts within the whole column are significantly different (p<0.05).
^A-BMeans with different superscripts within the same freezing method are significantly different (p<0.05).
^x-zMeans with different superscripts within the same thawing method are significantly different (p<0.05).
¹⁾High frequency thawing.
²⁾Microwave thawing.