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The Brassica genus (Brassicaceae family) is a large group of primarily herbaceous plants, one of the most important crops after soybean in world oilseed production, and as fresh vegetables, they are widely consumed throughout the year as part of salads or after cooking. This genus includes various types of well-known species such as cabbage, broccoli, brussels sprouts, kale, kohlrabi, pak choi, rape, turnip, mustard, and cress. Brassica plants are also distinguished from other vegetable plants by their high functional (phenolic and organosulfur compounds) and nutritional properties. Food losses and waste reduction are a worldwide challenge involving governments, researchers, and food industries. Therefore, by-product revalorization and the use of key extracted biocompounds to fortify innovative foods seems an interesting challenge to afford.
By-Product Characteristics |
F (kHz) |
Power Parameters |
Solvent | S:L Ratio (w:v) |
T (min) |
T (°C) |
Other Information | Main Findings | Ref. |
---|---|---|---|---|---|---|---|---|---|
Radish seeds cv. IPR 11 Particle size information NA |
25 | 165 W | EtOH | 1:12 | 20–60 | 30–60 | USAE bath with indirect contact. After the extraction, seeds were separated by filtration, and the excess solvent was removed until reaching a constant weight. |
The maximum yield (25%), a greater amount of phytosterols and tocopherols, and, consequently, greater oxidative stability. | [14] |
Red radish cv. information NA Freeze dried 1–2 mm pieces |
NA | 138–358 W | H2O | 0.06:30 | 30–120 | 45 | Before USAE by pulse cycles of 5 s on and 1 s off, extraction of anthocyanins was performed. | High-energy USAE treatment (120 min at 286–258 W) is adequate to enhance TAC but does not preserve anthocyanins. | [8] |
Broccoli leaves, stems, and inflorescences cvs.: ‘TSX 007′, ‘Monaco’, ‘BRO 2047′, ‘Parthenon’, and ‘Summer Purple’ Dried (45 °C, 48 h) Particle size information NA |
NA | NA | 80% EtOH |
10:60 | 60 | 45–50 | Excess EtOH was removed by heating it at 37 °C in a rotary evaporator under vacuum. The resulting aqueous extracts were combined and lyophilized. |
Extraction yield of 13.4–16.3% dw. High TAC and chlorophylls and phenolics (mainly kaempferol and quercetin glucosides) in leaf extracts (‘Summer Purple’) and high GLS content in inflorescence extract. |
[15] |
Broccoli leaves, stems, and inflorescences cv. Parthenon Dried (45 °C, 24–48 h) Particle size information NA |
NA | 220 V 360 W |
H2O | 1:50 | 60 | NA | Before USAE, the mixture was heated for 16 min at 121 °C. After US, four times its volume of ethanol was added, and after 12 h of incubation, it was dried at 45 °C in a forced-air oven. | USAE did not manage to modify the neutral sugar profile. | [16] |
Broccoli by-products cv. information NA Dried (35 °C, 48 h) Particle size information NA |
25 | 50 W/L | H2O | 1:10 | 60 | 15 | The extract was dried at 30 °C in a vacuum oven. The residue was mixed with water and recovered by centrifugation (6000 rpm × 10 min). | USAE extracted more bioactive compounds than supercritical fluids but not as many as pressurized liquid. | [13] |
Cauliflower by-products cv., drying, and particle size information NA |
NA | 175 W | H2O (pH 11) |
1:4 | 15 | NA | The crude fiber and insoluble protein were removed from the extract first with 3 layer gauze and then by centrifugation (4000 rpm × 30 min). | Extraction yield of 53.1% and 12.066 g of soluble leaf protein kg−1. | [9] |
Cauliflower by-products Blanching cv. information NA Dried (50–55 °C overnight) Particle size 0.5 mm |
24 | 400 W | H2O 70% MeOH 80% Ac |
50:100 | 0–10 | NA | Amplitude USAE from 20–100%. After US, centrifugation at 1500× g for 15 min, and the pellet was centrifuged with 100 mL of solvent. Both supernatants were collected, combined, and filtered under vacuum conditions. |
The amplitude affected the extraction of isothyocyanates (80% amplitude for 3 min) and phenolics (100% amplitude for 3 min). | [12] |
Rapeseed meal cv., drying, and particle size information NA |
28 | 0.228 W/cm2 | H2O | 1:30 | 41.48 | NA | Other extraction conditions were pH 11.71 and USAE power 40%. | High protein yield of 43.3% and nitrogen solubility of 18.1%. | [3] |
Broccoli cv., drying, and particle size information NA |
40 | 500 W | Ch 80% EtOH Ac |
100:500 | 60 | 40 | Extracts were combined to metal-organic framework nanocubes. They were dispersed by an ultrasonic probe in 100 mL, then triethylamine as a capping agent was added, and the mixture was agitated and heated for 12 h at 130 °C. | Broccoli extract combined with MOF-5-NCs showed synergistic activity against P. aeruginosa bacteria in standard and clinical strains. | [2] |
Kale cv. information NA Convective dryer (39 °C) Particle size information NA |
20 | 100 W | 80% EtOH |
2:40 | 60 | 60 | USAE in two cycles of 30 min Extracts were filtered, combined, and evaporated. The residues were dissolved in methanol and filtered. |
High isolation of phenolic acids and high yield of biocompounds in short time and reduced solvent volume with easy handling. | [4] |
Broccoli seeds cv., drying, and particle size information NA |
NA | 200–500 W | H2O EA |
1:10–1:50 | 5–40 s | 25–35 | Before USAE, broccoli seeds were treated in a MWAE oven for 1–4 min at low power. | The highest SFN formation was under a MWAE pretreatment of 3 min and a US treatment of 20 s, 500 W, and 1:10 for water or 1:50 ethyl acetate. | [7] |
Broccoli stems and leaves cv. information NA. Dried (30–35 °C, 48 h). Particle size information NA |
25 | 50 W/L | H2O | 1:10 | 60 | NA | After homogenization, the extract was dried at 30 °C in a vacuum oven. The residue was mixed with water (25 mL) and recovered by centrifuging at 6000 rpm for 10 min. | High-quality extract in terms of antimicrobial efficacy against Pseudomonas spp. and Candida krusei. | [17] |
White cabbage cv. information NA Oven-dried (60 °C, 72 h) Particle size information NA |
40 | 132 W | 60% EtOH |
2:10 | 120 | 30–70 | Ultrasonic intensity of 0.46 W/cm2. The obtained extracts were hydrolyzed before analyzing. | Richer extract at 30 °C. Antimicrobial activities only of the hydrolyzed extracts. |
[5] |
Broccoli heads cv., drying, and particle size information NA |
23 | NA | H2O | 1:20 | 1–12 | 25–60 | Amplitude was set at 135 µm. | Higher myrosinase inactivation and SFN content at 60 °C for 4 min. Activation energy was 3.6-fold lower regarding traditional blanching. | [10] |
Camelina sativa oil cv., drying, and particle size information NA |
35 | 60–120 W | 40–80 EtOH |
1:5–1:15 | 10–20 | 30 | USAE in 2–4 cycles of 5 min each. A solid-phase extraction procedure to obtain an extract rich in GLS and to perform cellular assays. |
High-GLS extraction with 65% EtOH, 1:15, and 10 min. The purified extract (800 mg from 10 g) showed chemopreventive action against colorectal cancer cells. |
[6] |
Thirty-six Brassica oleracea var. acephala accessions Dried in an oven (105 °C) or freeze-dried Particle size information NA. |
40 | 300 W | 80% MetOH |
0.03:1.5 | 30 | 20 | After USAE, extracts were centrifuged at 15,000× g for 5 min. | Higher GLS content, TAC, TPC, and sugars with freeze-dried samples and USAE compared with hot extraction. | [11] |
Cabbage leaves, fresh and steamed (100 °C, 2 min) cv., and drying info NA Particle size 1.7–2.55 mm. |
37 | 320 W | H2O | 5:50 | 40 | NA | Absorbed US power of 0.03 W/g extraction + MWAE or vaccum. |
Higher glucoraphanin content with USAE + vacuum or MWAE More effective (87%) when leaves were steamed, presenting higher myrosinase inactivation. |
[18] |
By-Product Characteristics |
Power (W) |
P | Solvent | S:L Ratio (w:v) |
T (min) |
T (°C) |
Other Information | Main Findings | Ref. |
---|---|---|---|---|---|---|---|---|---|
Purple-heart radish cv. information NA. Dried in the oven (60 °C) Particle size 117-μm. |
NA | Atm | H2O andEtOH | 0.5:31.5 | 20 | 70 | Twenty grams of broccoli powder were pre-extracted with petroleum ether II at 80 °C for 6 h. | Polysaccharide yield (29%) was higher than hot (~24%) and USAE (27%) extraction. | [20] |
White cabbage leaves are chopped. cv. information NA. Fresh or dried with a hot air dryer (60 °C) Particle size information NA. |
130–390 | Atm | DCh H2O |
5:50 | 1–5 | 22–38(DCh)22–98(H2O) | After extraction with a domestic MW oven, the extract was filtered and dehydrated using the rotary evaporator at 30 °C (for DCh) or 45 °C (for H2O). | Higher SFN yield in less time. Higher MW powers resulted in a shorter extraction time.No differences between fresh and semi-dried samples, nor between the solvents used. |
[21] |
Broccoli florets, stems, and leaves. cv., drying, and particle size information NA. | NA | Atm | 40–80% MetOH |
1:20 | 10–20 | 55–75 | After extraction, the mixture was centrifuged for 20 min at 10,350 rpm and 4 °C. The supernatant was filtered and stored at −20 °C. |
The optimum conditions were 74.5, 80, 80% MetOH, 15.9, 10, 18.9 min, and 74.5, 73.3, 75 °C for stalks, leaves, and florets, respectively. Increased the phenolic yield up to 65.3, 45.70, 133.6% for stalks, leaves, and florets, respectively, in less time. |
[22] |
Purple and white cabbages cv. information NA. Sun-dried. Particle size 80–100 µm. |
200–400 | Atm | NAc | 1:4–1:7 | 10–25 | 60–90 | After extraction, the extract was completed with 10 mL. | Optimum conditions: 201 W at 60 °C for 10 min at a 1:4 ratio. A polynomial regression was the best-fitting model. |
[19] |
Cabbage leaves (1.7–2.55 mm) cv. information NA. Fresh and steamed. (100 °C for 2 min). Particle size information NA. |
180 | Atm 70 kPa |
H2O | 5:50 | 10 | NA | Combined with USAE | Higher glucoraphanin content using vacuum MWAE with USAE than atmospheric MWAE. More effective (87%) when leaves were previously steamed, and a higher inactivation of the myrosinase enzyme. |
[18] |
EAE is based on the use of enzymes to break down the cell walls of plant material and improve the extraction yield of its bioactive compounds. The main conditions to be considered are shown in Table 3. Most of the Brassica by-products used in the studies come from broccoli, radish, cauliflower, and cabbage. Before EAE, by-products are usually pretreated by grounding and drying (oven at 45–60 °C or using a freeze-dryer), although particle size is rarely detailed. The enzymes used were determined by the compound to be extracted. The main enzymes found were cellulase, hemicellulase, protease, pectinase, and glucanase, among others. Papaioannou and Liakopoulou-Kyrikides [23] used a fungus to facilitate the β-carotene production from Brassica by-products. Other green technologies combined with EAE, such as MWAE [20] and USAE [24], have been used to increase the extraction yield prior to enzymatic rupture of the cell walls. Only half of the articles summarized in Table 3 detail the enzyme inactivation conditions; two of them used heating for a few minutes and one used refrigeration. The solid:liquid ratio ranged from 10:40 to 5:500, like other extraction methods using green technologies. Extraction time was highly variable, ranging from 8.4 to 1200 min, but the temperature was limited between 26 [23] and 68 °C [20].
By-Product Characteristics | Combined with | Enzymes | Inactivation Enzymes |
S:L Ratio (w:v) |
T (min) |
T (°C) |
Main Findings | Ref. |
---|---|---|---|---|---|---|---|---|
Purple-heart radish cv. information NA. Oven-dryer (60 °C). |
MW | Papain | NA | 1:55–1:65 | 8.4 | 68 | EAE combined with MWAE facilitated cell rupture and enzymolysis, improving the extraction yields and shortening the extraction time. | [20] |
Broccoli by-products (leaves, stems, and inflorescences). cv. Parthenon Forced-air oven dryer (45 °C, 24–48 h) |
NA | Cellulase | Cooled at room temperature | 1:50.8 | 120 | 50 | Decreased the sugar content and increased the uronic acid content. Non-extractable phenolics were found higher in inflorescences and increased with EAE and TAC. |
[16] |
Radish root ground with a mortar. cv. and drying information NA. |
US | Cellulases Pectinases Amylases Glucanases Hemicellulases |
Few minutes at 90 °C | 10:40 | 66–84 | 46–64 | Higher TAC with the highest extraction of TPC. | [24] |
Canola (Brassica napus) oil pressing residues. Particle size: 0.5 mm cv. and drying information NA. |
NA | Protamex® Alcalase® Viscozyme® Phyzyme® |
NA | 1:10 | 240–1200 | 45–50 | The applied enzymes effectively enhanced the solubility of proteins, despite the lower yield of crude proteins compared to the alkaline extraction (40–82 vs. 91 g/100 g dw). | [25] |
Cauliflower florets and leaves cv. information NA Pre-extraction with 96% ethanol (1:5) for 30 min at 100 °C. Residue was dried at 40 °C. |
NA | Proteases Cellulases Endopolygalacturonase II Rhamnogalacturonan hydrolase Pectin methyl esterases Rapidase Liq+ |
10 min at 100 °C | 5:500 | 240 | 50 | Higher methoxy pectins of high molar mass were extracted with three enzyme mixtures. Health benefit pectic oligosaccharides were obtained after pectin extraction. Seventy percent of the by-products were consumed to extract two products of interest. |
[26] |
Cabbage (91.5% humidity) | NA | Blakeslea trispora (mould) | NA | 1:10 | NA | 26 | Higher biomass accumulation and carotenoid production. | [23] |
By-Product Characteristics | Green Technology Used | S:L Ratio (w:v) |
T (min) |
T (°C) |
Other Parameters to Be Monitored | Main Findings | Ref. |
---|---|---|---|---|---|---|---|
Broccoli leaves, stems, and inflorescences. cv. ParthenonDried in a forced-air oven (45 °C, 24–48 h). |
Supercritical fluids using CO2 | NA | 120 | 45–55 | Dynamic extraction. Flow: 2 L/min. Three hundred bar at 55 °C or one-hundred and fifty bar at 45 °C. |
The content of non-extractable phenolics and TAC increased and were higher in inflorescences. | [16] |
Broccoli by-products. Dried (35 °C, 48 h). |
Supercritical fluids using CO2 | NA | 140 | 35 | Two pumps:
Flow: 2 L/min |
Presented the worst results regarding the extraction of bioactive compounds. | [29] |
Broccoli by-products. Dried (35 °C, 48 h) |
Pressurized liquid | 15:25 | 10 | 60 | Steps:
|
The highest content of bioactive compounds and TAC. | [13] |
Yellow mustard flour (30.7% oil, 30.9% protein, 4% ash, and 9% fiber). | Ultrafiltration | NA | NA | 25 | Before ultrafiltration, defatting was carried out with hexane. Film composite membrane (150–300 Da, pH tolerance range 2–10 at 25 °C, max. Tª of 80 °C, and pressure of 40 bar). |
In acidic conditions, 77% of the phenolic compounds were recovered. Combination of diafiltration with nanofiltration was beneficial only when processing under acidic conditions. |
[30] |
Broccoli stems and leaves Dried (30–35 ℃, 48 h). |
Supercritical fluids using CO2 | NA | 140 | 35 | Two pumps:
Flow: 2 L/min Drying in a vacuum oven (30 °C) |
High-quality extract in terms of antimicrobial efficiency against Pseudomonas spp. and Candida krusei. | [17] |
Broccoli stems and leaves cv. Parthenon and Naxos. |
Supercritical fluids using CO2 | NA | NA | NA | Two pumps:
|
High yield of β-carotene, phenolic compounds, chlorophylls, and phytosterols. Great TAC. Reduced organic solvent consumption. |
[31] |