Time dependence of bioactive compounds and antioxidant capacity during germination of different cultivars of broccoli and radish seeds

Optimisation of the germination process of different cultivars of broccoli (Brassica oleracea var. italica cv. Lucky, cv. Tiburon and cv. Belstar) and radish (Raphanus sativus cv. Rebel and cv. Bolide) seeds in relation to the content of glucosinolates (GLS), vitamin C and total antioxidant capacity was carried out in order to maximise the health-promoting properties of Brassica sprouts. The content of total and individual GLS varied between species, among cultivars, and germination time. Glucoraphanin in broccoli and glucoraphenin in radish were the predominant GLS in raw seeds (61–77 and 63–129 μmol/g DM, respectively) and, although their content decreased during germination, they were maintained in rather large proportions in sprouts. Vitamin C was not detected in raw seeds and its content increased sharply in broccoli and radish sprouts (162–350 and 84–113 mg/100 g DM, respectively). Raw brassica seeds are an excellent source of antioxidant capacity (64–90 and 103–162 μmol Trolox/g DM in broccoli and radish, respectively) and germination led to a sharp increase. Germination of broccoli cv. Belstar and radish cv. Rebel for 4 days provided the largest glucoraphanin and glucoraphenin content, respectively, and also brought about large amounts of vitamin C and antioxidant capacity.     

The antioxidant activity of selected cruciferous vegetables subjected to aquathermal processing

Kale (Brassica oleracea var. Acephala), broccoli (Brassica oleracea var. botrytis italica), Brussels sprouts (Brassica oleracea L. var. gemmifera) and green and white cauliflower (Brassica oleracea var. botrytis) were used to determine their contents of antioxidising agents: vitamin C, carotenoids and polyphenols. The examined vegetables were found to contain between 40.6 and 107 mg/100 g FW of vitamin C, from 0.04 to 2.7 mg/100 g FW of carotenoids, and from 144 to 773 mg/100 g FW of polyphenols. Cauliflower was found to contain the smallest amount of these compounds and kale the largest. The antioxidant activity of the vegetables was determined on the basis of their ability to extinguish the ABTS free radical. The aquathermal processes to which the vegetables were subsequently subjected reduced their antioxidant activity, mainly due to escape of vitamin C and polyphenols into the water environment. These losses were largest in the case of leafy or highly fragmented vegetables.     

A rapid quantitative determination of phenolic acids in Brassica oleracea by capillary zone electrophoresis

A simple and rapid capillary zone electrophoresis method to quantitatively determine the phenolic acid contents in brassica vegetables is described. Phenolic compounds were extracted from broccoli, broccolini, Brussels sprouts, cabbage and cauliflower and the main hydroxycinnamic acids (sinapic, ferulic, p-coumaric and caffeic acids) were isolated by solid phase extraction with C18 cartridges. Using an optimised method, the four analytes were separated in less than 7 min in a 50 μm × 60 cm capillary with a 15 mM borate buffer (pH = 9.13) and a separation voltage of 30 kV at 30 °C. A linear relationship was observed for the method (r = 0.9997–0.9999) with detection limits ranging from 1.1 to 2.3 mg/kg of vegetables for the analytes. This method demonstrated good reproducibility with coefficients of variation of less than 5% for peak area and less than 1% for migration time (n = 7). The method was successfully applied to quantitatively determine the phenolic acid contents in a range of brassica vegetables and the results were in good agreement when compared to those from high performance liquid chromatography analysis.     

A comparative study on the polyphenolic content,antibacterial activity and antioxidant capacity of different solvent extracts of Brassica oleracea vegetables

Brassica vegetables are rich in polyphenols, flavonoids and glucosinolates. Investigation was undertaken to optimise the best solvents among 60% ethanol, acetone and methanol for the extraction of polyphenols from Brassica vegetables. Furthermore, different properties such as antibacterial activity and antioxidant capacity were also investigated. Results showed that a 60% methanolic extract showed the highest total phenolic content which was 23.6, 20.4 and 18.7 mg gallic acid equivalents (GAE) g^?1 extract for broccoli, Brussels sprouts and white cabbage, respectively. The hydroxybenzoic acid content of various solvent extracts ranged from 5.86 to 8.91 GAE g^?1 extract for broccoli, 2.70 to 5.44 GAE g^?1 extract for Brussels sprouts and 3.69 to 4.86 GAE g^?1 extract for white cabbage, while the hydroxycinnamic acid content ranged from 0.78 to 1.26 chlorogenic acid equivalents (CAE) g^?1 extract for broccoli, 1.41 to 3.45 CAE g^?1 extract for Brussels sprouts and 0.49 to 1.14 CAE g^?1 extract for white cabbage. A concentration‐dependent antioxidative capacity was confirmed for different reactive oxygen species, and moderate antibacterial activity was observed against a number of Gram‐negative and Gram‐positive food spoilage and food pathogenic bacteria. Solvents significantly affected polyphenolic content and its different properties, and the methanol was found to be the best solvent for the extraction of polyphenols from studied Brassica vegetables.     

Improving the phytochemical composition of broccoli sprouts by elicitation

In order to increase the concentrations of bioactive compounds in broccoli sprouts, exogenous elicitors: methionine, tryptophan, chitosan, salicylic acid (SA) and methyl jasmonate (MeJA) were sprayed at different concentrations during germination. The effects of the elicitors on vitamin C, phenolic compounds and glucosinolate levels were assessed in 3, 5 and 7-days old seedlings. The application of 200, 300 μM SA and 0.01% chitosan induced increases, by 26%, 18% and 54%, respectively in the content of vitamin C in 5 days old broccoli sprouts. Flavonoid concentration was also increased by 31% and 33% after 10 μM MeJA and 100 μM SA treatments, respectively in 7 days old broccoli sprouts. In contrast, methionine or tryptophan solutions did not positively affect the vitamin C or the phenolic compounds in the sprouts. The individual classes of glucosinolates respond differently to the elicitor treatment. Methionine, a sulphur-containing amino acid, applied at 5 mM, significantly increased, by 32%, the levels of aliphatic glucosinolates. However, indole glucosinolates presented a significant response to the induction with tryptophan, SA or MeJA treatments. Tryptophan at 10 mM concentration augmented by 1.8-fold the indole glucosinolate concentration in 7 days old broccoli sprouts, and the treatments of 100 μM SA and 25 μM MeJA also induced significantly higher amounts of indole glucosinolates (by 33% and 51%, respectively) in 7 days old treated broccoli sprouts. Therefore, the application of elicitors could be a useful tool for improving the bioactive metabolites in broccoli sprouts for fresh consumption or functional ingredients for nutraceuticals foods.     

Acidification,crushing and thermal treatments can influence the profile and stability of folate poly-γ-glutamates in broccoli (Brassica oleracea L. var. italica)

The influence of different treatments, i.e., crushing, high temperature short time (90 °C/4 min) (HTST) and low temperature long time (60 °C/40 min) (LTLT) blanching, acidification (pH 4.3), and sequences of these treatments on the folate poly-γ-glutamate profile and stability were investigated. In this study, broccoli was used as a case study. Regarding the folate poly-γ-glutamate profile, endogenous folate poly-γ-glutamates in broccoli florets were found predominantly as hepta- and hexa-γ-glutamates. Crushing raw broccoli, acidification and LTLT blanching enhanced folate deconjugation resulting in monoglutamate, di- and tri-γ-glutamates. Compared to other treatments, HTST blanching preformed prior to crushing resulted in the highest concentration of long chain poly-γ-glutamates. Regarding folate poly-γ-glutamates stability, acidification combined with LTLT blanching decreased folate stability whereas HTST blanching combined with different sequences of blanching and crushing did not affect folate poly-γ-glutamates stability. It was concluded that crushing (prior to heating), acidification and blanching could be strategically applied to increase the folate monoglutamate content of broccoli.     

Retention of mineral constituents in frozen brassicas depending on the method of preliminary processing of the raw material and preparation of frozen products for consumption

The content of ash, P, K, Ca, Mg, Na, Fe, Zn, Mn, Cu, Cr and Ni was determined in four species of brassicas: Brussels sprouts, broccoli, and green and white cauliflowers. The investigation covered the raw material, the material blanched or cooked before freezing and frozen products after 12 months of refrigerated storage and prepared for consumption. Frozen products were obtained by the traditional method of freezing the blanched material or by the modified method of freezing the cooked material. The processing of vegetables before freezing (washing, grinding, blanching or cooking) caused statistically significant decreases in most constituents analysed. Blanching did not basically change the content of sodium and calcium; or that of chromium in both types of cauliflower; copper and nickel in white cauliflower; and nickel and phosphorus in Brussels sprouts. Cooking in brine, however, caused increases in the content of ash, sodium and calcium in white cauliflower, decreases in the content of potassium and iron and, in some species, of the remaining constituents. In comparison with the traditional method, a greater content of most analysed elements was found in frozen products obtained by the modified technology and prepared for consumption. However, no significant differences were noted in the level of chromium in all the samples; in the level of calcium in broccoli and green cauliflower; of nickel in broccoli; of nickel, copper and zinc in white cauliflower; and of copper in green cauliflower.     

Genotypic effects on the phytochemical quality of seeds and sprouts from commercial broccoli cultivars

Determining ontogenic diversity in vegetables, in general or Brassicas in particular, regarding the bioactive content, is an interesting task since the most promising Brassicaceae foods could have the highest nutritional and health-promoting properties. Therefore, vitamin C, phenolic compounds, glucosinolate content, and total antioxidant capacity were evaluated in commercial cultivars of broccoli (Brassica oleracea var. italica; cv. Nubia, cv. Marathon and cv. Viola) seeds and during the sprouting period. Vitamin C was not detected in dormant seeds and its content increased with the germination, reaching values ranging from 53 (cv. Nubia) to 64 (cv. Marathon) mg/100 g FW, at the end of the monitored period (14days). The total glucosinolate content in seeds and 3-day-old sprouts was higher in cv. Marathon (1005 and 556 mg/100 g FW, respectively), however cv. Viola sprouts registered the highest glucosinolate content 7 and 14 days after sowing (235 and 208 mg/100 g FW, respectively). Aliphatic glucosinolates were more affected by genetic factors than the indolic glucosinolates, being glucoraphanin the predominant glucosinolate in cv. Nubia and cv. Marathon, whereas glucoiberin was the major glucosinolate in cv. Viola. The flavonoid and total phenolic content was significantly higher in cv. Viola. Also, seeds of this cultivar showed the highest antioxidant capacity (2.7 mg Trolox/g FW).     

Effect of thermal treatment on glucosinolates and antioxidant-related parameters in red cabbage (Brassica oleracea L. ssp. capitata f. rubra)

The effects of various thermal processing treatments (blanching, boiling and steaming) of red cabbage, Brassica oleracea L. ssp. capitata f. rubra cv. ‘Autoro’, were assessed for the levels of glucosinolates (GLS), total phenols (TP), total monomeric anthocyanins (TMA), l-ascorbic acid (L-AA) and soluble sugars, as well as for the antioxidant potential by the ferric reducing ability power (FRAP) and oxygen radical absorbance capacity (ORAC) assays. Individual native GLS were determined by ion-pair HPLC-MS/DAD. There were significant (p < 0.05) losses in blanched red cabbage: TP, 43%, TMA 59%, FRAP 42%, ORAC 51%, L-AA 48% and soluble sugars 45%. Boiling gave less extensive reductions: TP 16%, TMA 41%, FRAP 17%, ORAC 19%, L-AA 24% and soluble sugars 19%. Steaming caused no losses for TP, ORAC, FRAP or soluble sugars. However, significant reductions were found for TMA and L-AA, with 29% and 11%, respectively. In general losses were accounted for in the processing waters; however, TMA was not fully recovered, indicating degradation. Total GLS were severely affected by processing, with reductions of 64%, 38% and 19% in blanched, boiled and steamed red cabbage, respectively. Total aliphatic and indole GLS were similarly affected. Lost GLS were partially recovered in the processing water.     

Processing (blanching, boiling, steaming) effects on the content of glucosinolates and antioxidant-related parameters in cauliflower (Brassica oleracea L. ssp. botrytis)

Five different varieties of cauliflower (Brassica oleracea L. ssp. botrytis); two white (cv. ‘Aviso’, ‘Dania’), one purple (cv. ‘Grafitti’), one green (cv. ‘Emeraude’) and one romanesco/green pyramidal (cv. ‘Celio’) cultivar have been studied. All samples were thermally processed and the effects on the levels of glucosinolates (GLS), total phenols (TP), total monomeric anthocyanins (TMA), l-ascorbic acid (l-AA) and antioxidant capacities (FRAP and ORAC) were investigated. Processing methods applied were: blanching (3 min), boiling (10 min) and steaming (10 min). Total GLS were significantly (p < 0.05) affected by processing with the highest losses, 55 and 42% on average, occurring for boiled and blanched samples, respectively. Significant effects were also noted for steaming, but to a lesser extent, i.e. 19% average reduction. Antioxidant-related parameters were similarly affected with average losses of 27, 33, 36 and 46% in boiled cauliflower and 16, 21, 22 and 28% in blanched for TP, FRAP, l-AA and ORAC, respectively. Blanching and boiling reduced TMA in purple cauliflower by 38 and 53%, respectively. Steaming affected the antioxidant-related parameters the least for all cultivars. l-AA was significantly reduced by 14% in all cultivars by steaming. Some differences in behaviour between cultivars were noted, especially between white and coloured cultivars for TP, FRAP and l-AA, but also for some GLS. The main losses were caused by leaching into the processing water.     

Partial characterization of white cabbages (Brassica oleracea var. capitata f. alba) from different regions by glucosinolates, bioactive compounds, total antioxidant activities and proteins

Glucosinolates (GLS), antioxidative compounds, total radical scavenging activities (TRSAs) and proteins of white cabbage samples derived from different regions of Europe, collected in the spring and autumn, were studied. Glucobrassicin and sinigrin were the dominating GLS in all analyzed cabbage samples. Depending on origin, these two GLS accounted for ∼30% to ∼70% of the total. The total GLS content ranged from 3.3 to 7.7 μmol/g dw in lyophilized vegetables. Assays based on electron transfer [total phenols by Folin-Ciocalteu reagent (FCR), 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)] radical cation (ABTS) and 1,1-diphenyl-2-picrylhydrazyl (DPPH)] were used to compare the TRSAs and the main bioactive compounds in cabbage. Total polyphenols varied from 2.4 to 4.9 GAE/g dw. The TRSAs ranged from 2.7 to 8.2 μmol TE/g dw in ABTS test and from 2.4 to 5.4 μmol TE/g dw in DPPH assay. The maximum amount of polyphenol compounds, antioxidant activity, as well as total GLS content, were recorded in Belgian cabbage harvested in the autumn and the lowest ones were found for Poland 2 cabbage harvested in the spring. In extracted and separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) proteins from cabbage leaves only in samples from England and Belgium some differences in patterns were found in the regions of 60 and 97 kDa. The calculated correlations between antioxidative potency and the abundance of bioactive compounds were highly statistically significant. This suggests that TRSA could serve as a means of standardization of natural mixtures, at least in the case of cabbage, necessary to compare results of biological studies carried out for vegetable derived samples.     

Anti-oxidant activity and total phenolic content of some Asian vegetables

The anti-oxidant activity of extracts from 36 vegetables was evaluated by using a model system consisting of β-carotene and linoleic acid. The total phenolics of the extracts was determined spectrophotometrically according to the Folin–Ciocalteau procedure and ranged from 34 to 400 mg (100 g)⁻¹ on a fresh weight basis. Mint, aonla, black carrots, chenopodium, fenugreek, kachnar and ginger had high phenolic contents. The anti-oxidant activity expressed as per percent inhibition of oxidation ranged from a high of 92% in turmeric extracts to a low of 12.8% in long melon. Other vegetables found to have high anti-oxidant activity (>70%) were kachnar, aonla, ginger, fenugreek, mint, beetroot, black carrots, Brussels sprouts, broccoli, lotus stem, yam, coriander and tomato. Anti-oxidant activity correlated significantly and positively with total phenolics ( r ²=0.6578, P  < 0.05). The results indicate that vegetables containing high phenolics may provide a source of dietary anti-oxidants.     

Glucosinolates fortification of cruciferous sprouts by sulphur supplementation during cultivation to enhance anti-cancer activity

The cruciferous sprouts, including cabbage (Brassicaoleracea), broccoli (Brassicacapitata) and radish (Raphanussativus), were cultivated with supplementation of sulphur salts. With supplementation of sulphur at 60 kg/ha, a 2–5-fold increases in total glucosinolates contents in the sprouts were observed. The individual glucosinolates whose concentration increased most significantly, included progoitrin, glucoerucin, glucobrassicin, glucohirsutin and 4-methoxybrassicin. The antioxidant properties of these sulphur supplemented sprouts were also higher than that of the normal sprouts due to the increases of phenolic compounds. Consequently, the glucosinolates fortified sprouts had higher anti-proliferative activity against HepG2 human hepatocarcinoma cells than the normal sprouts, as the cell viability decreased by 22–35%. Also in CT26 mouse colorectal cancer cells, the cell viability decrease by 34–59%.     

Antimicrobial effect and physicochemical properties of bioactive trilayer polycaprolactone/methylcellulose-based films on the growth of foodborne pathogens and total microbiota in fresh broccoli

Bioactive trilayer films were prepared using methylcellulose (MC) and polycaprolactone (PCL). Two antimicrobial formulations named as A (organic acids, extract of rosmarinic acid and Asian essential oil (EO) mixture) and B (organic acids, extract of rosmarinic acid and Italian EO mixture) were added in MC films during casting and the trilayer composite films (PCL/MC/PCL) were fabricated using compression molding. These films were inserted into packages containing broccoli and the packages were kept at 4 °C during 12 days storage to determine the antimicrobial capacity of the films and the physico-chemical properties of the films. Bioactive films showed a significant reduction of Escherichia coli in broccoli from Day 4 and a total inhibition at Day 12. Similarly, these films showed a significant reduction of Salmonella typhimurium from Day 2 and a total inhibition at Day 7. Moreover, the films controlled the growth of total aerobic microbiota (TAM) in broccoli up to 10 days. Encapsulation of antimicrobial compounds in films allowed decrease of barrier properties of films. Tensile strength of films was not affected by the presence of formulation B. These results demonstrated the potential application of trilayer antimicrobial on controlling food pathogens and total flora in pre-cut vegetables.     

In vitro binding of bile acids by spinach, kale, brussels sprouts, broccoli, mustard greens, green bell pepper, cabbage and collards

The in vitro binding of bile acids by spinach (Spinacia oleracea), kale (Brassica oleracea acephala), Brussels sprouts (Brassica oleracea gemmifera), broccoli (Brassica oleracea italica), mustard greens (Brassica juncea), green bell peppers (Capsicum annuum), cabbage (Brassica oleracea capitala) and collards (Brassica oleracea acephala) was determined using a mixture of bile acids secreted in human bile at a duodenal physiological pH of 6.3. Six treatments and two blank incubations were conducted testing various fresh raw green vegetables on an equal dry matter basis. Considering cholestyramine (bile acid binding, cholesterol lowering drug) as 100% bound, the relative in vitro bile acid binding of various vegetables tested on equal dry matter and total dietary fibre basis was 2–9% and 6–32%, respectively. Bile acid binding for spinach, kale and brussels sprouts was significantly higher than for broccoli and mustard greens. For broccoli and mustard greens binding values were significantly higher those for cabbage, bell pepper and collards. These results point to the health promoting potential of spinach = kale = brussels sprouts > broccoli = mustard greens > cabbage =  green bell peppers =  collards, as indicated by their bile acid binding on dry matter basis.     

Vegetables antioxidant losses during industrial processing and refrigerated storage

Twenty-five vegetables (artichoke, asparagus, beetroot, broad bean, broccoli, Brussels sprout, carrot, cauliflower, celery, chicory, cucumber, eggplant, endive, garlic, green bean, leek, lettuce, maize, onion, pea, pepper, radish, spinach, Swiss chard and zucchini) were used to evaluate their antioxidant activity. All fresh vegetables studied were able to scavenge lipoperoxyl and hydroxyl radicals. All the vegetables also presented good total capacity antioxidant by TEAC assay except cucumber, endive, carrot and zucchini.Vegetables stored (7 days) in a home refrigerator recorded the same antioxidant activity as fresh samples, except cucumber and zucchini (lipid peroxidation) and broccoli, Brussels sprout and leek (TEAC).Canned vegetables showed a more pronounced loss of antioxidant activity than frozen vegetables compared with fresh vegetables.During the shelf life of the processed vegetables (8 months for frozen and 18 months for canned vegetables), some products showed losses (19–48%) of their lipoperoxyl radical scavenging capacity and total antioxidant activity.     

Sulfhydryl and Ascorbic Acid Relationships in Selected Vegetables and Fruits

Selected vegetables and fruits were analyzed for ascorbic acid, total sulfur, and sulfhydryl-containing (-SH) fractions, shortly after harvest and after 3 wk storage at 2°C and 95–100% relative humidity. More than 95% of the original ascorbic acid content was retained in broccoli and brussels sprouts. Ascorbic acid stability in fruits appeared to be due to low pH but that did not explain high retention in broccoli and brussels sprouts. Initial ascorbic acid correlated with total sulfur (r = 0.909). Weaker correlations were found between total −SH and protein −SH fractions and ascorbic acid content (r = 0.626 and 0.672). The quantity of sulfhydryl containing compounds did not explain ascorbic acid retention mechanisms of the vegetables.     

Improvement of heating uniformity in packaged acidified vegetables pasteurized with a 915 MHz continuous microwave system

Continuous microwave processing to produce shelf-stable acidified vegetables with moderate to high salt contents poses challenges in pasteurization due to reduced microwave penetration depths and non-uniform heating. Cups of sweetpotato, red bell pepper, and broccoli acidified to pH 3.8 with citric acid solution containing 0-1% NaCl were placed on a conveyor belt and passed through a microwave tunnel operating at 915 MHz and 4 kW with a 4 min residence time. The time-temperature profiles of vegetable pieces at 5 locations in the package were measured using fiber optic temperature sensors. Addition of 1% NaCl to the cover solution lowered microwave penetration into vegetable pieces and decreased the mean temperature in cups of acidified vegetables from 84 to 73 °C. Soaking blanched vegetables for 24 h in a solution with NaCl and citric acid prior to processing improved microwave heating. Heating was non-uniform in all packages with a cold spot of approximately 60 °C at a point in the container farthest from the incident microwaves. More uniform heating was achieved by implementation of a two-stage rotation apparatus to rotate vegetable cups 180° during processing. Rotating the cups resulted in more uniform heating and a temperature of 77 °C at the cold spot. This is above the industrial standard of 74 °C for in-pack pasteurization of acidified vegetables. The effective treatment involved blanching, soaking for 24 h in a NaCl and citric acid solution, and 180° rotation. This work has contributed to a better understanding of the influence of salt addition and distribution during dielectric heating of acidified vegetables using a 915 MHz continuous microwave system.     

Changes in post-harvest phytochemical qualities of broccoli florets during ambient and refrigerated storage

The effect of ambient and refrigerated storage temperature on post-harvest phytochemical qualities of broccoli florets was investigated during storage. Fresh broccoli florets were packed in polypropylene (PP) micro-perforated film bags and stored, under open ambient storage conditions (15 ± 1 °C, 55 ± 2% RH), and laboratory refrigerated storage (4 ± 0.5 °C, 50 ± 2% RH) for a total period of 144 h. Quality of broccoli florets was evaluated in terms of physiological weight loss (PLW), ascorbic acid content, chlorophyll content, β-carotene and total antioxidant activity. Samples packed in PP micro-perforated film showed significantly (P < 0.05) lower losses of PLW, ascorbic acid, chlorophyll, β-carotene and total antioxidant activity (5.51%, 4.53%, 18.9%, 4.04% and 16.4%, respectively), during storage for up to 144 h under refrigerated conditions. For better phytochemical retention, the broccoli florets should be packed in PP micro-perforated film bags and stored under refrigerated conditions.