Table 5. Organic acid composition of citrus, apple, and grape peel powders (unit: mg/100 g)

Organic acids	Citrus	Apple	Grape	F-value
Oxalic	49.83±1.10^a1)2)	ND³⁾	12.43±0.31^b	5,147.55^***4)
Citric	508.20±11.48^a	34.93±0.76^b	ND	5,608.35^***
Tartaric	42.00±1.05^b	0.73±0.06^c	45.97±1.11^a	3,270.56^***
Malic	217.53±6.04^b	875.87±17.61^a	125.83±3.59^c	5,104.07^***
Succinic	8.27±0.15^b	1.37±0.06^c	31.10±0.87^a	3,206.60^***
Lactic	19.47±0.51^b	ND	37.73±0.81^a	4,250.92^***
Formic	ND	ND	ND	ND
Acetic	21.37±0.45^c	62.97±1.50^b	80.50±2.52^a	1,860.01^***
Adipic	9.47±0.32^b	ND	134.57±3.10^a	5,356.33^***
Propionic	ND	ND	ND	ND
Total⁵⁾	876.17±21.54^b	975.90±19.14^a	468.17±12.04^c	2,433.72^***

All values are mean±SD (n=3).
Means within different superscript letters (^a-c) in the same row are significantly different at p<0.05 using Duncan’s multiple range test.
ND, not detected.
^***p<0.001.
Total organic acid content was calculated as the sum of individually quantified acids.