Waste grape skins thermal dehydration: potential release of colour, phenolic and aroma compounds into wine

Figures & data

Table 1. Moisture content (g_water kg⁻¹ _{dry matter}) of waste grape skins according to the dehydration treatment.

Tabla 1. Contenido de humedad (g_agua kg⁻¹ _{base seca}) de hollejos de uva de acuerdo al tratamiento de deshidratación.

Waste grape skin	Raw	Control freeze-drying	Oven drying
			60°C	90°C	100°C
Bobal	1308.79	71.63^b	156.89^a	63.63^b	21.26^c
Garnacha Tintorera	1528.76	88.53^b	145.55^a	67.44^b	16.06^c
Cabernet Sauvignon	1391.77	94.64^b	173.61^a	90.91^b	15.10^c
AMIX	1490.77	94.50^b	119.70^a	81.97^b	18.45^c
Note: Different letters between dehydration columns indicate significant differences (p < 0.05) Nota: Letras diferentes entre los tratamientos de deshidratación indican diferencias significativas (p < 0,05).

Table 2. Total polyphenol index (TPI) and colour parameters of dehydrated waste grape skins macerated in synthetic wine solutions.

Tabla 2. Índice de polifenoles totales y parámetros de color de las soluciones de hollejos deshidratados macerados en vino sintético.

		Oven drying
Control	60°C	90°C	100°C
Bobal
TPI	33.71^a,1	25.04^b,3	23.13^c,2	7.21^d,3
Colour intensity	0.01^c,2	0.02^b,2	0.02^b,3	0.03^a,3
Shade	0.64^c,1	0.58^c,3	1.40^b,3	4.51^a,3
% Yellow	36.44^c,1	34.81^c,3	54.42^b,4	79.88^a,3
% Red	56.66^b,1	59.30^a,1	38.68^c,1	17.70^d,2
% Blue	6.89^a,2	5.88^a,1	6.89^a,1	2.41^b,2
Garnacha Tintorera
TPI	23.03^b,c,2	26.55^a,2	23.96^b,1	22.88^c,1
Colour intensity	0.02^d,1	0.03^c,1	0.04^b,1	0.06^a,1
Shade	0.55^c,1	0.55^c,4	1.49^b,3	3.07^a,3
% Yellow	32.87^c,1	32.96^c,4	55.91^b,3	71.63^a,4
% Red	59.90^a,1	59.73^a,1	37.42^b,2	23.26^c,1
% Blue	7.38^a,1,2	7.12^a,1	6.66^a,1	5.10^a,1
Cabernet Sauvignon
TPI	14.78^c,4	43.97^a,1	17.42^b,3	9.05^d,2
Colour intensity	0.02^c,2	0.01^d,3	0.04^a,2	0.03^b,3
Shade	0.68^b,1	0.62^b,2	5.98^a,1	4.71^a,1
% Yellow	36.40^d,1	38.45^c,1	85.67^b,1	97.94^a,1
% Red	53.50^b,1	61.54^a,1	14.32^c,4	2.05^d,4
% Blue	0.01^a,3	0.01^a,2	0.01^a,2	0.08^a,2
AMIX
TPI	19.42^a,3	14.24^b,4	11.20^c,4	0.75^d,4
Colour intensity	0.01^b,3	0.01^b,2	0.02^b,3	0.05^a,2
Shade	0.68^c,1	0.66^c,1	2.40^b,2	8.40^a,2
% Yellow	35.24^c,1	36.41^c,2	65.41^b,2	87.87^a,2
% Red	59.75^a,1	59.10^a,2	27.15^b,3	10.69^b,3
% Blue	6.63^b,2	8.47^a,1	7.43^a,1	1.43^c,2
Note: Different superscript letters within columns indicate significant differences (p < 0.05) between dehydration treatments. For each parameter, different superscript numbers within a row indicate significant differences (p < 0.05) between waste grape skin varieties. TPI is expressed in mg L^−1 of gallic acid equivalents. Control refers to waste grape skins dehydrated by freeze drying. Notas: Letras diferentes entre las columnas indican diferencias significativas (p < 0,05) entre los tratamientos de deshidratación. Para cada parámetro, los superíndices numéricos diferentes entre filas indican diferencias significativas (p < 0,05) entre las variedades de hollejos. TPI está expresado en mg L^−1 de equivalentes de ácido gálico. La liofilización se utilizó como tratamiento control.

Table 3. Anthocyanin concentration (mg L⁻¹) of dehydrated waste grape skins macerated in synthetic wine solutions.

Tabla 3. Concentración de antocianos (mg L⁻¹) de las soluciones de hollejos deshidratados macerados en vino sintético

		Oven drying
	Control	60°C	90°C	100°C
Bobal
Dephinidinl–3-glucoside	4.46^a,1	1.83^b,1	1.37^c,1	0.12^d,3
Cyanidin-3-glucoside	2.75^a,1	0.71^b,3	0.42^c,1	0.04^d,2
Petunidin-3-glucoside	4.07^a,1	1.40^b,3	0.78^c,1	0.11^d,1
Peonidin-3-glucoside	7.22^a,2	3.50^b,2	1.68^c,2	0.47^d,2
Malvidin-3-glucoside	11.76^a,3	6.90^b,2	3.41^c,2	0.72^d,3
Total non-acyl anthocyanins	30.27^a,2	14.38^b,2	7.68^c,2	1.48^d,3
Total acetyl-anthocyanins	1.80^a,2	0.97^b,3	0.55^b,1	0.19^c,2
Total coumaroyl-anthocyanins	8.19^a,2	3.70^b,2	2.49^c,2	0.72^d,2
Total pigments	40.26^a,2	19.05^b,2	10.72^c,2	2.39^d,2
Garnacha Tintorera
Dephinidinl-3-glucoside	2.51^a,3	1.83^b,1	0.58^c,2	0.33^d,2
Cyanidin-3-glucoside	2.48^a,2	1.66^b,1	0.18^c,2	0.05^d,1
Petunidin-3-glucoside	3.20^a,3	2.39^b,1	0.38^c,2	0.11^d,1
Peonidin-3-glucoside	20.37^a,1	13.87^b,1	3.69^c,1	1.27^d,1
Malvidin-3-glucoside	18.33^a,1	13.14^b,1	3.86^c,1	1.35^d,1
Total non-acyl anthocyanins	46.91^a,1	32.91^b,1	8.71^c,1	3.13^d,1
Total acetyl-anthocyanins	1.67^a,2	1.13^b,3	0.34^c,2	0.13^c,2
Total coumaroyl-anthocyanins	13.33^a,1	8.90^b,1	3.50^c,1	1.37^c,1
Total pigments	61.91^a,1	42.94^b,1	12.54^c,1	4.63^d,1
Cabernet Sauvignon
Dephinidinl-3-glucoside	4.19^a,2	1.71^b,2	0.41^c,3	0.43^c,1
Cyanidin-3-glucoside	1.40^a,4	0.20^b,4	0.03^c,3	0.03^c,3
Petunidin-3-glucoside	3.38^a,2	0.89^b,4	0.15^c,4	0.11^c,1
Peonidin-3-glucoside	3.00^a,4	1.10^b,4	0.21^c,4	0.17^c,3
Malvidin-3-glucoside	11.94^a,2	5.53^b,4	0.97^c,3	0.78^c,2
Total non-acyl anthocyanins	23.93^a,3	9.51^b,4	1.79^c,3	1.54^c,2
Total acetyl-anthocyanins	7.00^a,1	3.48^b,1	0.75^c,1	0.52^c,1
Total coumaroyl-anthocyanins	4.93^a,3	1.71^b,3	0.77^c,3	0.45^c,3
Total pigments	35.86^a,3	14.70^b,3	3.31^c,3	2.51^c,2
AMIX
Dephinidinl-3-glucoside	1.98^a,4	1.65^b,2	0.24^c,4	0.01^d,4
Cyanidin-3-glucoside	1.61^a,3	1.12^b,2	0.17^c,2	0.01^d,4
Petunidin-3-glucoside	1.90^a,4	1.47^b,2	0.21^c,3	0.01^d,2
Peonidin-3-glucoside	4.32^a,3	2.98^b,3	0.52^c,3	0.04^d,4
Malvidin-3-glucoside	8.30^a,4	6.46^b,3	1.07^c,3	0.06^d,4
Total non-acyl anthocyanins	18.13^a,4	13.68^b,3	2.23^c,3	0.1^d,4
Total acetyl-anthocyanins	1.78^a,2	1.49^b,2	0.27^c,2	0.01^d,3
Total coumaroyl-anthocyanins	4.60^a,3	2.51^b,2,3	0.52^c,3	0.01^d,4
Total pigments	24.51^a,4	17.68^b,2	3.02^c,3	0.01^d,3
Notes: Different superscript letters within columns indicate significant differences (p < 0.05) between dehydration treatments. For each compound, different superscript numbers within a row indicate significant differences (p < 0.05) between waste grape skin varieties. Control refers to waste grape skins dehydrated by freeze drying. Notas: Letras diferentes entre las columnas indican diferencias significativas (p < 0,05) entre los tratamientos de deshidratación. Para cada compuesto, los superíndices numéricos diferentes entre filas indican diferencias significativas (p < 0,05) entre las variedades de hollejos. La liofilización se utilizó como tratamiento control.

Table 4. Low molecular weight phenolic compounds concentration (mg L⁻¹) of dehydrated waste grape skins macerated in synthetic wine solutions.

Tabla 4. Concentración de compuestos fenólicos de bajo peso molecular (mg L⁻¹) de las soluciones de hollejos deshidratados macerados en vino sintético.

		Oven drying
	Control	60°C	90°C	100°C
Bobal
(+)-Catechin	1.65^a,2	1.06^b,2		n.d.
Vanillic acid	2.63^1	n.d.		n.d.
(−)-Epicatechin	n.d.	n.d.		n.d.
Ferulic Acid	0.15^a,1	0.15^a,1	0.18^a,1,2	n.d.
(E)-Resveratrol	0.66^a,2	0.30^b,1	0.21^c,1	n.d.
Total LMWPC	5.11^a,2	1.52^b,1	0.4^c,1	n.d.
Garnacha Tintorera
(+)-Catechin	1.83^2	n.d.	n.d.	n.d.
Vanillic acid	n.d.	n.d.	n.d.	n.d.
(−)-Epicatechin	6.81^1	n.d.	n.d.	n.d.
Ferulic acid	0.13^b,1	0.01^b,2	0.21^a,1	0.19^a,1
(E)-Resveratrol	0.04^b,3	0.12^a,2,3	0.06^b,2	0.02^c,1
Total LMWPC	8.8^a,1	0.14^c,2	0.27^b,2	0.21^b,1
Cabernet Sauvignon
(+)-Catechin	n.d.	n.d.	n.d.	n.d.
Vanillic acid	n.d.	n.d.	n.d.	n.d.
(−)-Epicatechin	n.d.	n.d.	n.d.	n.d.
Ferulic acid	0.18^a,1	0.16^a,1	n.d.	0.07^a,b,2
(E)-Resveratrol	2.77^a,1	0.22^b,1,2	n.d.	n.d.
Total LMWPC	2.9^a,3	0.39^b,2	n.d.	0.07^c,2
AMIX
(+)-Catechin	2.12^a,1	1.39^b,1	n.d.	n.d.
Vanillic acid	n.d.	n.d.	n.d.	n.d.
(−)-Epicatechin	n.d.	n.d.		n.d.
Ferulic acid	0.20^a,1	0.20^a,1	0.13^b,2	n.d.
(E)-Resveratrol	0.11^a,3	0.04^b,3	n.d.	n.d.
Total LMWPC	2.44^a,3	1.64^b,1	0.13^7c,3
Notes: Low molecular weight phenolic compounds (LMWPC). Different superscript letters within columns indicate significant differences (p < 0.05) between dehydration treatments. For each compound, different superscript numbers within a row indicate significant differences (p < 0.05) between waste grape skin varieties. Control refers to waste grape skins dehydrated by freeze drying. Notas: Compuestos fenólicos de bajo peso molecular (LMWPC). Letras differentes entre las columnas indican diferencias significativas (p < 0,05) entre los tratamientos de deshidratación. Para cada compuesto, los superíndices numéricos diferentes entre filas indican diferencias significativas (p < 0,05) entre las variedades de hollejos. La liofilización se utilizó como tratamiento control.

Figure 1. Volatile composition and standard deviation after oven dehydration from different dehydrated waste grape skin model wine solutions.

Figura 1. Composición volátil y desviación estándar de las soluciones de hollejos deshidratados macerados en vino sintético.

Figure 2. Discriminant analysis scatter plots of dehydration treatments and dehydrated waste grape skins (DWGS).

Figura 2. Análisis discriminante de las soluciones de hollejos (DWGS) de acuerdo al tratamiento de deshidratación y a la variedad.

Figure 3. Composition and standard deviation of synthetic and rosé wine prepared with dehydrated waste grape skins (DWGS) of Bobal.

Figura 3. Composición y desviación estándar de los vinos rosados elaborados con hollejos deshidratados (DWGS) de Bobal.

Supplementary Figure 1. Free aroma fraction of hydroalcoholic solution after direct addition of dehydrated waste grape skins.

Figura adicional 1. Fracción libre de los aromas presentes en las soluciones de hollejos (DWGS) de acuerdo al tratamiento de deshidratación y a la variedad.