Effect of Tannin-Binding Agents (Polyethylene Glycol and Polyvinylpyrrolidone) Supplementation on In Vitro Gas Production Kinetics of Some Grape Yield Byproducts

Table 2

Total gas production volume of grape yield byproducts in incubation times (mL/g DM).

Treatments	Incubation times (h)
	2	4	6	8	12	16	24	36	48
Grape pomace (GP)
Control	39.2^a	89.1^a	127.8^a	157.7^b	188.8^b	206.3^b	231.7^b	260.3^b	269.8^b
GP + PEG	7.6^b	56.2^b	119.1^b	166.7^a	208.6^a	242.0^a	277.8^a	312.5^a	331.1^a
GP + PVP	9.4^b	51.3^b	115.5^b	163.6^a	205.4^a	239.8^a	276.5^a	310.5^a	327.8^a
SEM	1.59	1.59	1.49	1.25	1.83	2.36	2.45	2.39	2.54
Raisin waste (RW)
Control	33.1^a	73.8^a	101.0^b	118.7^b	141.8^b	156.6^b	180.9^b	203.2^b	208.7^b
RW + PEG	12.7^b	62.0^b	109.6^a	134.3^a	158.4^a	180.3^a	204.4^a	229.4^a	247.1^a
RW + PVP	9.8^b	54.4^c	104.6^ab	132.8^a	159.9^a	182.3^a	206.5^a	229.7^a	247.9^a
SEM	1.41	1.49	1.85	2.51	3.51	3.74	3.87	3.64	3.54
Dried grape byproduct (DGB)
Control	32.7^a	77.5^a	112.7^a	139.1^a	161.6^b	182.5^b	209.2^b	234.5^b	243.4^b
DGB + PEG	9.8^b	58.4^b	114.8^a	146.9^a	182.5^a	212.3^a	241.8^a	269.2^a	286.5^a
DGB + PVP	6.9^b	47.8^c	103.3^b	136.3^a	165.6^b	189.9^b	218.3^b	234.5^b	264.1^b
SEM	2.01	2.83	2.50	3.59	4.02	5.16	6.08	6.12	6.18

GP: grape pomace, RW: raisin waste, and DGB: dried grape pomace.
^a,b,cWithin a column, means without a common superscript letter differ (𝑃<0.05).