Table 1.

Extraction yield, protein content and polyphenol content of pectin.

Samples	Yield (%)	Protein Content (%)	TPC (mg GAE/g)
AE	5.28 ± 1.57 b	0.46 ± 0.08 d	8.58 ± 0.47 b
UA	6.52 ± 0.48 b	0.51 ± 0.05 c	9.15 ± 0.35 b
SEA	9.93 ± 0.33 a	0.68 ± 0.04 a	17.55 ± 0.55 a
USEA	10.72 ± 0.39 a	0.62 ± 0.01 b	18.85 ± 0.22 a

TPC, total polyphenol content; AE, acid extraction; UA, ultrasonic-assisted acid extraction; SEA, steam explosion pretreatment combined with acid extraction; USEA, ultrasonic-assisted steam explosion pretreatment combined with acid extraction. The meanings of AE, UA, SEA and USEA in subsequent charts and tables are described above. Values with different superscripts within a column are significantly different (p < 0.05).