Effects of different defrosting methods on the stability of bioactive compounds and consumer acceptability of frozen broccoli

Figures & data

Figure 1. Total phenolic compounds (A) and vitamin C (B) of frozen and thawed broccoli. Different letters in the same chart indicate statistical difference by the LSD test (p < 0.05). Abbreviations: Stove Method 1 (SM1, broccoli boiled for 40 s); Stove Method 2 (SM2, broccoli boiled until second boiling was observed); Microwave Method 1 (MM1, broccoli microwaved for 150 s); Microwave Method 2 (MM2, broccoli microwaved for 300 s).

Figura 1. Compuestos fenólicos totales (A) y vitamina C (B) del brócoli congelado y descongelado. Diferentes letras en la misma gráfica indican diferencia estadísticamente significativa por la prueba LSD (p < 0,05). Abreviaciones: Método por estufa 1 (SM1, brócoli hervido por 40 s); Método por estufa 2 (SM2, brócoli hervido hasta que se observó un segundo hervor); Método por microondas 1 (MM1, brócoli descongelado en microondas por 150 s); Método por microondas 2 (MM2, brócoli descongelado en microondas por 300 s).

Figure 2. Typical HPLC-DAD glucosinolate chromatogram (shown at 227 nm) obtained from methanol/water extracts of frozen broccoli. Tentative identification of peaks was performed as indicated in Table 1. Peak assignment: (1) Glucoraphanin; (2) 4-hydroxyglucobrassicin; (3) Glucobrassicin; (4) Neoglucobrassicin; (IS) Sinigrin (internal standard).

Figura 2. Perfil cromatográfico típico obtenido mediante HPLC-PDA de glucosinolatos (mostrado a 227 nm) presentes en extracto metanólico/acuoso de brócoli congelado. La identificación tentativa de los picos cromatográficos se realizó como se indica en la Tabla 1. Asignación de picos: (1) Glucorafanina; (2) 4-hidroxiglucobrasicina; (3) Glucobrasicina; (4) Neoglucobrasicina; (IS) Sinigrina (estándar interno).

Table 1. Tentative identification of broccoli (Brassica oleracea var. Italica) glucosinolate chromatographic profile obtained by HPLC-PDA.

Tabla 1. Identificación tentativa del perfil cromatográfico de glucosinolatos de brócoli (Brassica oleracea var. Italica) obtenido por HPLC-PDA.

Peak number (retention time)^1	Λmax (nm)^2	Tentative identification	Previously reported in broccoli^3	Method of identification^4
1 (6.9)	222	Glucoraphanin	i, ii, iii, iv	A, B, C
2 (15.0)	221	4-hydroxyglucobrassicin	i, iii	B, C
3 (22.3)	222, 280	Glucobrassicin	i, ii, iii, iv	B, C
4 (25.7)	222	Neoglucobrassicin	i, ii, iii, iv	B, C

Notes: ¹Number of peak assigned according to the order of elution from the C18 stationary phase. ²Wavelengths of maximum absorption in the UV/Vis spectra of each chromatographic peak. ³Previously reported by (i) Vallejo et al. (2003c); (ii) Miglio et al. (2008); (iii) Barbieri et al. (2008); (iv) Yuan et al. (2009). ⁴Method applied for the identification of the peak: (A) identification by comparison with the retention time and wavelengths of maximum absorption in the UV/Vis spectra of commercial standards; (B) identification by spectral interpretation of the wavelengths of maximum absorption in the UV/Vis spectra and comparison with wavelengths of maximum absorption reported in the literature (Vallejo et al., 2003a); (C) identification by the order of chromatographic elution reported in the literature (Barbieri et al., 2008; Hansen et al., 1995; Vallejo et al., 2003a).

Notas: ¹Número de pico asignado de acuerdo al orden de elución de la fase estacionaria C18. ²Longitudes de onda de máxima absorción en el espectro de UV/vis de cada pico cromatográfico. ³Previamente reportado por (i) Vallejo et al. (2003c); (ii) Miglio et al. (2008); (iii) Barbieri et al. (2008); (iv) Yuan et al. (2009). ⁴Método aplicado para la identificación del pico: (A) identificación por comparación con el tiempo de retención y longitudes de onda de máxima absorción en el espectro de UV/Vis de estándares comerciales; (B) identificación por interpretación del espectro de longitudes de onda de máxima absorción en el espectro de UV/Vis y comparación con longitudes de onda de máxima absorción reportadas en la literatura (Vallejo et al., 2003a); (C) identificación por el orden de elución cromatográfica reportado en la literatura (Barbieri et al., 2008; Hansen et al., 1995; Vallejo et al., 2003a).

Table 2. Concentrations of individual glucosinolates present in frozen and thawed broccoli.

Tabla 2. Concentraciones de glucosinolatos individuales presentes en brócoli congelado y descongelado.

	Individual glucosinolates content (mmol/kg DW)^1,2,3
Compound	Control	SM1^4	MM1^4	SM2^4	MM2^4
Glucoraphanin	5.22 ± 0.12 b	5.40 ± 0.14 b	7.79 ± 0.60 a	3.91 ± 0.20 c	5.53 ± 0.33 b
4-hydroxyglucobrassicin	10.13 ± 0.86 b	11.61 ± 0.48 b	14.50 ± 0.91 a	6.90 ± 1.13 c	9.46 ± 0.23 b
Glucobrassicin	73.16 ± 3.00 a	58.16 ± 0.91 b	57.09 ± 2.40 b	23.87 ± 1.21 c	54.63 ± 1.42 b
Neoglucobrassicin	9.30 ± 0.61 ab	6.83 ± 0.16 c	9.72 ± 0.40 a	3.60 ± 0.46 d	8.10 ± 0.23 bc
TOTAL	97.81 ± 4.59 a	82.00 ± 1.69 bc	89.10 ± 4.31 ab	38.28 ± 3.00 d	77.72 ± 2.21 c

Notes: ¹Concentrations are reported as desulfoglucoraphanin equivalents. All compounds were quantified at 227 nm. ²Values represent the mean of 3 replications ± standard error of the mean. ³Different letters in the same row indicate statistical difference by the LSD test (p < 0.05). ⁴Abbreviations: Stove Method 1 (SM1, broccoli boiled for 40 s); Stove Method 2 (SM2, broccoli boiled until second boiling was observed); Microwave Method 1 (MM1, broccoli microwaved for 150 s); Microwave Method 2 (MM2, broccoli microwaved for 300 s).

Notas: ¹Las concentraciones son reportadas como equivalentes de desulfoglucorafanina. ²Los valores representan la media de 3 réplicas ± el error estándar de la media. ³Diferentes letras en la misma fila indican diferencia estadísticamente significativa por la prueba LSD (p < 0,05). ⁴Abreviaciones: Método por estufa 1 (SM1, brócoli hervido por 40 s); Método por estufa 2 (SM2, brócoli hervido hasta que se observó un segundo hervor); Método por microondas 1 (MM1, brócoli descongelado en microondas por 150 s); Método por microondas 2 (MM2, brócoli descongelado en microondas por 300 s).

Figure 3. Typical HPLC-DAD carotenoid chromatogram (shown at 450 nm) from acetone (0.1% BHT) extracts of frozen broccoli. Tentative identification of peaks was performed as indicated in Table 2. Peak assignment: (1) Neoxanthin; (2) Violaxanthin; (3) Chlorophyll b; (4) Lutein; (5) Chlorophyll a; (6) β-cryptoxanthin; (7) β-carotene.

Figura 3. Perfil cromatográfico típico obtenido mediante HPLC-PDA de carotenoides (mostrado a 227 nm) presentes en extracto acetónico (0.1% BHT) de brócoli congelado. La identificación tentativa de los picos cromatográficos se realizó como se indica en la Tabla 2. Asignación de picos: (1) Neoxantina; (2) Violaxantina; (3) Clorofila b; (4) Luteína; (5) Clorofila a; (6) β-criptoxantina; (7) β-caroteno.

Table 3. Tentative identification of broccoli (Brassica oleracea var. Italica) carotenoid and chloropyll chromatographic profile obtained by HPLC-PDA.

Tabla 3. Identificación tentativa del perfil cromatográfico de carotenoides y clorofilas en brócoli (Brassica oleracea var. Italica) obtenido por HPLC-PDA.

Peak number (retention time)^1	λmax (nm)^2	Tentative identification	Previously reported in broccoli^3	Method of identification^4
1 (10.3)	(417), 441, 470.1	Neoxanthin	i, ii	B, C
2 (11.0)	(416), 439.8, 468.8	Violaxanthin	i, ii	B, C
3 (20.4)	(315.4), 344, 468.8	Chlorophyll b	i	B, C
4 (21.1)	(422), 445.9, 473.7	Lutein	i, ii	A, B, C
5 (26.2)	(382), (417), 432.6	Chlorophyll a	i	B, C
6 (40.0)	(429), 453.1, 478.5	β-cryptoxanthin	i	B, C
7 (41.7)	(422), 447.1, 473.7	β-carotene	i, ii	A, B, C

Notes: ¹Number of peak assigned according to the order of elution from the C30 stationary phase. ²Wavelengths of maximum absorption in the UV/Vis spectra of each chromatographic peak, values in parentheses indicate a shoulder in the peak. ³Previously reported by (i) Khachik, Beecher, and Whittaker (1986). (ii) Khachik, Beecher, Goli, and Lusby (1991). ⁴Method applied for the identification of the peak: (A) identification by comparison with the retention time and wavelengths of maximum absorption in the UV/Vis spectra of commercial standards; (B) identification by spectral interpretation of the wavelengths of maximum absorption in the UV/Vis spectra and comparison with wavelengths of maximum absorption reported in the literature (Chandrika, Jansz, & Warnasuriya, 2005; Lee, Castle, & Coates, 2001; Mendes-Pinto, Ferreira, Oliveira, & De Pinho, 2004; Taylor, Brackenridge, Vivier, & Oberholster, 2006); (C) identification by the order of chromatographic elution reported in the literature (Chandrika et al., 2005; Khachik et al., 1986; Lee et al., 2001; Mendes-Pinto et al., 2004; Taylor et al., 2006).

Notas: ¹Número de pico asignado de acuerdo al orden de elución de la fase estacionaria C30. ²Longitudes de onda de máxima absorción en el espectro de UV/vis de cada pico cromatográfico, los valores entre paréntesis indican un hombro en el pico. ³Previamente reportado por (i) Khachik et al. (1986). (ii) Khachik et al. (1991). ⁴Método aplicado para la identificación del pico: (A) identificación por comparación con el tiempo de retención y longitudes de onda de máxima absorción en el espectro de UV/Vis de estándares comerciales; (B) identificación por interpretación del espectro de longitudes de onda de máxima absorción en el espectro de UV/Vis y comparación con longitudes de onda de máxima absorción reportadas en la literatura (Chandrika et al., 2005; Lee et al., 2001; Mendes-Pinto et al., 2004; Taylor et al., 2006); (C) identificación por el orden de elución cromatográfica reportado en la literatura (Chandrika et al., 2005; Khachik et al., 1986; Lee et al., 2001; Mendes-Pinto et al., 2004; Taylor et al., 2006).

Table 4. Concentrations of individual carotenoids present in frozen and thawed broccoli.

Tabla 4. Concentraciones de carotenoides individuales presentes en brócoli congelado y descongelado.

	Individual carotenoids content (mg/kg DW)^1,2,3
Compound	Control	SM1^4	MM1^4	SM2^4	MM2^4
Neoxanthin	16.02 ± 0.74 a	11.86 ± 0.69 bc	9.18 ± 0.13 d	12.35 ± 0.47 b	10.59 ± 0.33 cd
Violaxanthin	8.91 ± 0.64 b	10.82 ± 0.97 a	6.15 ± 0.02 c	8.22 ± 0.27 b	9.16 ± 0.26 ab
Chlorophyll b	43.19 ± 2.15 a	33.02 ± 1.70 b	27.21 ± 0.18 c	43.28 ± 0.92 a	35.02 ± 1.75 b
Lutein	99.22 ± 5.10 b	125.08 ± 6.31 a	74.02 ± 0.32 c	82.65 ± 2.28 c	73.38 ± 2.31 c
Chlorophyll a	22.24 ± 1.23 a	15.06 ± 0.92 c	13.77 ± 0.04 c	20.18 ± 0.52 ab	17.80 ± 0.60 b
β-cryptoxanthin	34.41 ± 1.69 b	42.72 ± 2.26 a	20.75 ± 2.60 c	20.45 ± 0.95 c	3.92 ± 0.24 d
β-carotene	4.26 ± 0.20 b	5.49 ± 0.32 a	2.77 ± 0.30 c	2.79 ± 0.12 c	0.95 ± 0.04 d
TOTAL	162.80 ± 8.38 b	195.98 ± 10.56 a	112.85 ± 3.37 cd	126.48 ± 4.07 c	97.99 ± 3.18 d

Notes: ¹Concentrations of carotenes are reported as β-carotene equivalents and xanthophylls are expressed as lutein equivalents. All compounds were quantified at 450 nm. ²Values represent the mean of 3 replications ± standard error of the mean. ³Different letters in the same row indicate statistical difference by the LSD test (p < 0.05). ⁴Abbreviations: Stove Method 1 (SM1, broccoli boiled for 40 s); Stove Method 2 (SM2, broccoli boiled until second boiling was observed); Microwave Method 1 (MM1, broccoli microwaved for 150 s); Microwave Method 2 (MM2, broccoli microwaved for 300 s).

Notas: ¹Las concentraciones de los carotenos son reportadas como equivalentes de β-caroteno y las xantófilas son exptresadas como equivalentes de luteína. ²Los valores representan la media de 3 réplicas ± el error estándar de la media. ³Diferentes letras en la misma fila indican diferencia estadísticamente significativa por la prueba LSD (p < 0,05). ⁴Abreviaciones: Método por estufa 1 (SM1, brócoli hervido por 40 s); Método por estufa 2 (SM2, brócoli hervido hasta que se observó un segundo hervor); Método por microondas 1 (MM1, brócoli descongelado en microondas por 150 s); Método por microondas 2 (MM2, brócoli descongelado en microondas por 300 s).

Figure 4. Average acceptance level of cold-served (A) and hot-served (B) broccoli and paired preference of cold-served (C) and hot-served (D) broccoli by consumers. Different letters in the same chart indicate statistical difference by the LSD test (p < 0.05). Abbreviations: Stove Method 1 (SM1, broccoli boiled for 40 s); Stove Method 2 (SM2, broccoli boiled until second boiling was observed); Microwave Method 1 (MM1, broccoli microwaved for 150 s); Microwave Method 2 (MM2, broccoli microwaved for 300 s).

Figura 4. Nivel de aceptación promedio de brócoli servido frío (A) y caliente (B) y preferencia pareada de brócoli servido frío (C) y caliente (D) por parte de los consumidores. Diferentes letras en la misma gráfica indican diferencia estadísticamente significativa por la prueba LSD (p < 0,05). Abreviaciones: Método por estufa 1 (SM1, brócoli hervido por 40 s); Método por estufa 2 (SM2, brócoli hervido hasta que se observó un segundo hervor); Método por microondas 1 (MM1, brócoli descongelado en microondas por 150 s); Método por microondas 2 (MM2, brócoli descongelado en microondas por 300 s).

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